Search

Understanding the ecological assembly of parasite communities is critical to characterise how changing host and environmental landscapes will alter infection dynamics and outcomes. However, studies frequently assume that (a) closely related parasite species or those with identical life-history strategies are functionally equivalent, and (b) the same factors will drive infection dynamics for a single parasite across multiple host species, oversimplifying community assembly patterns. Here, we challenge these two assumptions using a naturally occurring host–parasite system, with the mussel Anodonta anatina infected by the digenean trematode Echinoparyphium recurvatum, and the snail Viviparus viviparus infected by both E. recurvatum and Echinostoma sp. By analysing the impact of temporal parasite dispersal, host species and size, and the impact of coinfection (moving from broader environmental factors to within-host dynamics), we show that neither assumption holds true, but at different ecological scales. The assumption that closely related parasites can be functionally grouped is challenged when considering dispersal to the host (i.e. larger scales), while the assumption that the same factors will drive infection dynamics for a single parasite across multiple host species is challenged when considering within-host interspecific competition (i.e. smaller scales). Our results demonstrate that host identity, parasite identity and ecological scale require simultaneous consideration in studies of parasite community composition and transmission. [ABSTRACT FROM AUTHOR]

The biodiversity‐disease relationship states that increased species richness leads to lower pathogen pressure (i.e. the dilution effect), an effect that erodes with biodiversity loss. However, whether losses of the dilution effect can trigger extinction cascades remains largely unexplored.To explore this idea, we consider declines in freshwater mussels, on average the most threatened non‐marine group of organisms in the world. We argue that anthropogenically stimulated declines in mussel richness amplify pathogens in remaining species. Pathogen amplification triggers further local losses in both mussel abundance and richness, explaining the observed so‐called "enigmatic" declines in freshwater mussels.Vulnerable communities could become trapped in cycles of pathogen amplification and host decline. We highlight knowledge gaps and provide key steps to assess the likelihood of this occurring; these key steps are applicable to any host group.Policy implications. Our argument constitutes a testable hypothesis that may explain richness or abundance declines in previously intact communities. We provide further impetus for the consideration and preservation of diversity at a local scale and show that effective conservation requires integration of both host and parasite ecology. [ABSTRACT FROM AUTHOR]

Further isolation may arise through site-specific co-evolution between the mussels and hosts; Douda et al. ([7]) demonstrated that there are often differences in the suite of fish hosts used by I U. crassus i , even across genetically and geographically close populations. Keywords: conservation; glochidia; host specificity; parasitism; reproduction EN conservation glochidia host specificity parasitism reproduction 1 5 5 05/03/23 20230501 NES 230501 Understanding the life-history characteristics of endangered species is crucial to their conservation, management, and predicting their responses to environmental change (Stark et al., [16]). Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Uniocrassus Host specificity can increase vulnerability of mussels as survival is intrinsically linked to that of their hosts. [Extracted from the article]

Understanding how ecological communities are assembled remains a key goal of ecosystem ecology. Because communities are hierarchical, factors acting at multiple scales can contribute to patterns of community structure. Parasites provide a natural system to explore this idea, as they exist as discrete communities within host individuals, which are themselves part of a community and metacommunity.We aimed to understand the relative contribution of multi‐scale drivers in parasite community assembly and assess how patterns at one level may mask those occurring at another. Specifically, we wanted to disentangle patterns caused by passive sampling from those determined by ecological drivers, and how these vary with scale.We applied a Markov Random Fields model and assessed measures of β‐diversity and nestedness for 420 replicate parasite infracommunities (parasite assemblages in host individuals) across two freshwater mussel host species, three sites and two time periods, comparing our results to simulations from four different ecologically relevant null models.We showed that β‐diversity between sites (explaining 25% of variation in parasite distribution) and host species (41%) is greater than expected, and β‐diversity between individual hosts is smaller than expected, even after accounting for parasite prevalence and characteristics of host individuals. Furthermore, parasite communities were significantly less nested than expected once parasite prevalence and host characteristics were both accounted for, but more nested than expected otherwise, suggesting a degree of modularity at the within‐host level that is masked if underlying host and parasite characteristics are not taken into account. The Markov Random Fields model provided evidence for possible competitive within‐host parasite interactions, providing a mechanism for the observed infracommunity modularity.An integrative approach that examines factors at multiple scales is necessary to understand the composition of ecological communities. Furthermore, patterns at one level can alter the interpretation of ecologically important drivers at another if variation at higher scales is not accounted for. [ABSTRACT FROM AUTHOR]

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus‐building Delphi technique. Our 14 priority topics fell into five broad themes (autecology, population dynamics, global stressors, global diversity, and ecosystem services) and included understanding diets throughout mussel life history; identifying the drivers of population declines; defining metrics for quantifying mussel health; assessing the role of predators, parasites, and disease; informed guidance on the risks and opportunities for captive breeding and translocations; the loss of mussel–fish co‐evolutionary relationships; assessing the effects of increasing surface water changes; understanding the effects of sand and aggregate mining; understanding the effects of drug pollution and other emerging contaminants such as nanomaterials; appreciating the threats and opportunities arising from river restoration; conserving understudied hotspots by building local capacity through the principles of decolonization; identifying appropriate taxonomic units for conservation; improved quantification of the ecosystem services provided by mussels; and understanding how many mussels are enough to provide these services. Solutions for addressing the topics ranged from ecological studies to technological advances and socio‐political engagement. Prioritization of our topics can help to drive a proactive approach to the conservation of this declining group which provides a multitude of important ecosystem services. [ABSTRACT FROM AUTHOR]

Biological early warning systems (BEWSs) monitor the behaviour or physiology of living organisms as an indirect mechanism to sense local environmental changes, and have become a widely established tool for monitoring water pollution. Complementary to conventional chemical and physical techniques, their strength lies in the ability to continuously monitor water quality, providing direct and rapid warning of toxic discharges. Bivalve molluscs (mussels and clams) are ideal sensing organisms for BEWSs, owing to their: high water filtration capacity; sensitivity to numerous, diverse pollutants; considerable longevity; high abundance; and wide range of physical responses to environmental change. Two behavioural metrics of bivalves have dominated in ecotoxicological studies, and consequently spawned development into BEWSs: valve movements, typically measured using electromagnetic techniques; and bivalve cardiac activity, typically measured using infrared photoplethysmography. However, other, less studied bivalve behaviours may exhibit pollutant impacts, including shell growth and dissolution, premature egg/larval release, horizontal movement, and burial. Such metrics may, with further research, provide bases for future BEWSs, some through current valve movement monitoring technology, others potentially through acoustic telemetry. Future bivalve-based BEWSs may become more informative and sensitive through the greater nuance that lies in integration of different metrics simultaneously and/or multi-species monitoring. Future directions may seek techniques that reduce disturbance to bivalves and enable observation of a more natural mode of behaviour, through using untethered, or entirely unequipped, specimens. With rigorous controls for individual- and population-level variation, bivalves have great power as biosensors and, bolstered by the scope for future advancements, this field has the potential to make significant contributions to future water quality management. [ABSTRACT FROM AUTHOR]

A pioneering, quantitative study published in Journal of Animal Ecology in 1966 on freshwater mussel populations in the River Thames, UK, continues to be cited extensively as evidence of the major contribution that mussels make to benthic biomass and ecosystem functioning in global river ecosystems.Ecological alteration, as well as declines in freshwater mussel populations elsewhere, suggest that changes to mussel populations in the River Thames are likely to have occurred over the half century since this study.We resurveyed the site reported in Negus (1966) and quantified the changes in mussel population density, species composition, growth patterns and productivity.We found large declines in population density for all unionid species. The duck mussel Anodonta anatina decreased to 1.1% of 1964 density. The painter's mussel Unio pictorum fell to 3.2% of 1964 density. The swollen river mussel Unio tumidus showed statistically nonsignificant declines. In contrast to 1964, in 2020 we found no living specimens of the depressed river mussel Pseudanodonta complanata (classified as Vulnerable by the IUCN Red List) but found new records of the invasive, nonnative zebra mussel Dreissena polymorpha and Asian clam Corbicula fluminea. Additionally, we found strong decreases in size‐at‐age for all species, which now grow to 65–90% of maximum lengths in 1964. As a result of reduced density and size, estimated annual biomass production fell to 7.5% of 1964 levels.Since mussels can be important to ecosystem functioning, providing key regulating and provisioning services, the declines we found imply substantial degradation of freshwater ecosystem services in the River Thames, one of the UK's largest rivers. Our study also highlights the importance to conservationists and ecologists of updating and validating assumptions and data about wild populations, which in the present era of anthropogenic ecosystem alteration are undergoing significant and rapid changes. Regular population surveys of key species are essential to maintain an accurate picture of ecosystem health and to guide management. [ABSTRACT FROM AUTHOR]

Parasite conservation is important for the maintenance of ecosystem diversity and function. Conserving parasites relies first on understanding parasite biodiversity and second on estimating the extinction risk to that biodiversity. Although steps have been taken independently in both these areas, previous studies have overwhelmingly focused on helminths in vertebrate hosts over broad scales, providing low resolution and excluding a large proportion of possible host and parasite diversity. We estimated both total obligate parasite richness and parasite extinction risk in freshwater mussels (Unionidae and Margaritiferidae) from Europe and the United States to provide a case study for considering parasite conservation in a severely understudied system. We used currently reported host–parasite relationships to extrapolate parasite diversity to all possible mussel hosts and then used the threat levels of those hosts to estimate the extinction risk for both described and undescribed parasites. An estimated 67% of parasite richness in freshwater mussels is undescribed and over 80% of the most host‐specific groups (digenean trematodes and ciliates) are undescribed. We estimated that 21% of this total parasite fauna is at immediate risk of extinction, corresponding to 60 unique species, many of which will likely go extinct before being described. Given the important roles parasites play in community structure and function and the strong ecosystem engineering capacities of freshwater mussels, such extinctions are likely to severely affect freshwater ecosystems. Our detailed study of mussel parasites provides compelling evidence for the hidden conservation threat to parasites through extinction cascades and shows parasites are deserving of immediate attention. Article Impact Statement: Two‐thirds of freshwater mussel parasites are undescribed and over one‐fifth are at immediate risk of extinction. [ABSTRACT FROM AUTHOR]

The crisis generated by the emergence and pandemic spread of COVID‐19 has thrown into the global spotlight the dangers associated with novel diseases, as well as the key role of animals, especially wild animals, as potential sources of pathogens to humans. There is a widespread demand for a new relationship with wild and domestic animals, including suggested bans on hunting, wildlife trade, wet markets or consumption of wild animals. However, such policies risk ignoring essential elements of the problem as well as alienating and increasing hardship for local communities across the world, and might be unachievable at scale. There is thus a need for a more complex package of policy and practical responses. We undertook a solution scan to identify and collate 161 possible options for reducing the risks of further epidemic disease transmission from animals to humans, including potential further SARS‐CoV‐2 transmission (original or variants). We include all categories of animals in our responses (i.e. wildlife, captive, unmanaged/feral and domestic livestock and pets) and focus on pathogens (especially viruses) that, once transmitted from animals to humans, could acquire epidemic potential through high rates of human‐to‐human transmission. This excludes measures to prevent well‐known zoonotic diseases, such as rabies, that cannot readily transmit between humans. We focused solutions on societal measures, excluding the development of vaccines and other preventive therapeutic medicine and veterinary medicine options that are discussed elsewhere. We derived our solutions through reading the scientific literature, NGO position papers, and industry guidelines, collating our own experiences, and consulting experts in different fields. Herein, we review the major zoonotic transmission pathways and present an extensive list of options. The potential solutions are organised according to the key stages of the trade chain and encompass solutions that can be applied at the local, regional and international scales. This is a set of options targeted at practitioners and policy makers to encourage careful examination of possible courses of action, validating their impact and documenting outcomes. [ABSTRACT FROM AUTHOR]

There is growing acknowledgement that human‐induced change can push ecosystems beyond tipping points, resulting in the dramatic and sudden loss of vital ecosystem services. Invasive non‐native species (INNS) are spreading rapidly due to anthropogenic activities and climate change and can drive changes to ecosystem functioning by altering abiotic conditions and restructuring native communities. Shallow lake ecosystems are especially vulnerable to perturbation from INNS as they can exist in two alternative stable states: either clear water with an abundance of vegetation or turbid, unvegetated and dominated by phytoplankton. Through a global meta‐analysis of studies observing the effects of INNS on recipient lake ecosystems, we found that certain INNS drive significant changes in the abundance of key taxa and conditions that govern the balance of alternative equilibria in shallow lakes. Invasive fish and crustaceans demonstrated effects likely to lead to early ecosystem collapse to a turbid state and delay ecosystem recovery. Invasive molluscs presented opposite effects, which may delay ecosystem collapse and encourage ecosystem recovery. Our results demonstrate that INNS could significantly alter the tipping points of ecosystem collapse and recovery, and that not all invasive species may initiate system collapse. Our results provide guidance for managers of invaded shallow lake ecosystems, which provide diverse services including sanitation, potable water supply, industrial cooling, aquaculture and recreational resources. Moreover, our approach could be applied to identify key potential drivers of change in other crucial ecosystems which demonstrate alternative equilibria, such as coral reefs and kelp forests. [ABSTRACT FROM AUTHOR]

Isotopic analyses of the incrementally growing baleen in Mysticeti have been used to learn about their feeding and movement patterns. Using methods previously applied to Pacific minke whales, stable δ15N and δ13C isotope values were measured along the baleen plates of male and female minke whales from two locations in the Northeast Atlantic. The sample sizes used in this study are comparable to those previously used in the literature, and, although limited in size, the evidence suggests differences in isotopic signatures between whales caught at different locations. Both the δ15N and δ13C data suggest whales at the higher latitude site of Svalbard have a narrower diet than the whales from Lofoten/Vesterålen in Norway. Across all whales, the δ15N data indicate the whales primarily prey on fish for much of the year, only switching to zooplankton during the spring bloom. The δ13C data fail to confirm whether the whales migrate over long distances. [ABSTRACT FROM AUTHOR]

However, these models can only be used for one parasite at a time, and so possible interactions between parasites need to be indirectly estimated by including other parasites as a predictor in separate models for each parasite studied (e.g. Markle et al. [18]; Obiegala et al. [21]). This example is particularly pertinent; while the mobility of parasite life history stages has been demonstrated as important in driving infection dynamics and parasite infracommunity structure in terms of both presence and abundance (e.g. Lhorente et al. [17]; Mazé-Guilmo et al. [19]), the relative mobilities of different hosts, and specifically the mobile-immobile contrast, are an underdeveloped area of research. More generally, we recommend careful consideration of how host and parasite traits as well as the environment affect parasite prevalences and parasite abundances and an acknowledgement that these effects may not be the same. For example, whether parasites are directly transmitted between conspecifics (i.e. microparasites) or environmentally transmitted (i.e. macroparasites) can alter the risk of a parasite infection in the same host population (Han et al. [12]), though whether this extended to parasite intensity was not explored. [Extracted from the article]

Understanding how environmental drivers influence the assembly of parasite communities, in addition to how parasites may interact at an infracommunity level, are fundamental requirements for the study of parasite ecology. Knowledge of how parasite communities are assembled will help to predict the risk of parasitism for hosts, and model how parasite communities may change under variable conditions. However, studies frequently rely on presence–absence data and examine multiple host species or sites, metrics which may be too coarse to characterise nuanced within‐host patterns.We utilised a novel host system, the freshwater mussel Anodonta anatina, to investigate the drivers of community structure and explore parasite interactions. In addition, we aimed to highlight consistencies and inconsistencies between PA and abundance data.Our analysis incorporated 14 parasite taxa and 720 replicate infracommunities. Using Redundancy Analysis, a joint species distribution model and a Markov random field approach, we modelled the impact of both host‐level and environment‐level characteristics on parasite structure, as well as parasite–parasite correlations after accounting for all other factors. This approach was repeated for both the presence and abundance of all parasites.We demonstrated that the regional species pool, individual host characteristics (mussel length and gravidity) and predicted parasite–parasite interactions are all important but to varying degrees across parasite species, suggesting that applying generalities to parasite community construction is too simplistic. Furthermore, we showed that PA data fail to capture important density‐dependent effects of parasite load for parasites with high abundance, and in general performs poorly for high‐intensity parasites.Host and parasite traits, as well as broader environmental factors, all contribute to parasite community structure, emphasising that an integrated approach is required to study community assembly. However, care must be taken with the data used to infer patterns, as presence‐absence data may lead to incorrect ecological inference. [ABSTRACT FROM AUTHOR]

Multiple national and international trends and drivers are radically changing what biological security means for the United Kingdom (UK). New technologies present novel opportunities and challenges, and globalisation has created new pathways and increased the speed, volume and routes by which organisms can spread. The UK Biological Security Strategy (2018) acknowledges the importance of research on biological security in the UK. Given the breadth of potential research, a targeted agenda identifying the questions most critical to effective and coordinated progress in different disciplines of biological security is required. We used expert elicitation to generate 80 policy-relevant research questions considered by participants to have the greatest impact on UK biological security. Drawing on a collaboratively-developed set of 450 questions, proposed by 41 experts from academia, industry and the UK government (consulting 168 additional experts) we subdivided the final 80 questions into six categories: bioengineering; communication and behaviour; disease threats (including pandemics); governance and policy; invasive alien species; and securing biological materials and securing against misuse. Initially, the questions were ranked through a voting process and then reduced and refined to 80 during a one-day workshop with 35 participants from a variety of disciplines. Consistently emerging themes included: the nature of current and potential biological security threats, the efficacy of existing management actions, and the most appropriate future options. The resulting questions offer a research agenda for biological security in the UK that can assist the targeting of research resources and inform the implementation of the UK Biological Security Strategy. These questions include research that could aid with the mitigation of Covid-19, and preparation for the next pandemic. We hope that our structured and rigorous approach to creating a biological security research agenda will be replicated in other countries and regions. The world, not just the UK, is in need of a thoughtful approach to directing biological security research to tackle the emerging issues. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) are one of the greatest drivers of ecological change. Typically, control uses chemical agents that often are ineffective, harmful to non-target organisms, and environmentally persistent. Bivalves are frequently high impact IAS, but have proven particularly hard to control due to their valve-closing response when exposed to conventional control agents. Microencapsulation of biocides with edible coatings represents a highly targeted delivery route, bypassing avoidance responses and accumulating in bivalves through their prodigious filter feeding. Uneaten microcapsules degrade and become biologically inactive within hours thus reducing potential impacts on non-target biota. We manufactured two new formulations of microcapsules (BioBullets). Particles were designed to mimic natural food particles (algae) in terms of size (9.5 ± 0.5 to 19.4 ± 1.3 SE µm diameter), buoyancy (near neutral) and shape (spherical). Laboratory exposures demonstrated that two formulations effectively controlled the Gulf wedge clam Rangia cuneata, an IAS currently spreading rapidly through Europe. A single dose of 2–6 mg L−1 of the active ingredient in a static system achieved 90% mortality after 30 days of exposure. Microencapsulation offers an effective and targeted management tool for rapid responses following the early detection of both Gulf wedge clams and many other filter-feeding IAS, and may be especially effective in closed systems or where populations remain very localised. [ABSTRACT FROM AUTHOR]

Antarctica is experiencing significant ecological and environmental change, which may facilitate the establishment of non‐native marine species. Non‐native marine species will interact with other anthropogenic stressors affecting Antarctic ecosystems, such as climate change (warming, ocean acidification) and pollution, with irreversible ramifications for biodiversity and ecosystem services. We review current knowledge of non‐native marine species in the Antarctic region, the physical and physiological factors that resist establishment of non‐native marine species, changes to resistance under climate change, the role of legislation in limiting marine introductions, and the effect of increasing human activity on vectors and pathways of introduction. Evidence of non‐native marine species is limited: just four marine non‐native and one cryptogenic species that were likely introduced anthropogenically have been reported freely living in Antarctic or sub‐Antarctic waters, but no established populations have been reported; an additional six species have been observed in pathways to Antarctica that are potentially at risk of becoming invasive. We present estimates of the intensity of ship activity across fishing, tourism and research sectors: there may be approximately 180 vessels and 500+ voyages in Antarctic waters annually. However, these estimates are necessarily speculative because relevant data are scarce. To facilitate well‐informed policy and management, we make recommendations for future research into the likelihood of marine biological invasions in the Antarctic region. [ABSTRACT FROM AUTHOR]

Abstract Sustainable expansion of aquaculture is critical to global food security, and bivalve shellfish aquaculture represents a sustainable method to provide people with affordable nutritious food. Oysters represent 54% of the global bivalve market by value, with propagation of juveniles within hatcheries critical to allow the industry to grow. Growth and survival of juvenile oysters in hatchery systems is constrained by suboptimal feed. The live algal feed currently used is expensive, of variable quality, contamination prone, and the high level of skill and equipment required limits where hatcheries can be located. We demonstrate how a novel microencapsulated diet can increase the growth and survivorship of Ostrea edulis (European flat oyster) juveniles in both the laboratory and hatchery setting. The microcapsules are easily produced in large quantities, stable for long term storage, and can be customised to have exceptionally high levels of nutrients key for oyster growth. O. edulis larvae fed a combined diet of microcapsules and algae for 8 days had a 46% greater increase in maximum size, 171% greater increase in minimum size, and 5% higher survival than larvae fed algae alone. O. edulis spat of 4 mm fed the combined diet for 7 weeks also had significantly greater survivorship (16% greater in hatchery, 58% greater in laboratory) and growth comparable (hatchery) or better (laboratory experiments) than algae alone. Further tailoring of the nutritional composition of microcapsules to specific bivalve species or growth stages could allow microcapsules to replace a greater proportion of or even completely replace algal diets. There is potential for these diets to revolutionise bivalve shellfish farming globally. Highlights • O. edulis juveniles fed diets containing microcapsules had greater growth and survivorship than juveniles fed algae alone • The microcapsules are easily produced at large scale, stable for storage, and rich in desirable nutrients for bivalve growth • Microencapsulated diets for bivalves could help increase bivalve production and contribute to sustainable food security [ABSTRACT FROM AUTHOR]

Inter-basin Water Transfers (IBWT) are recognized as one of the major pathways of freshwater invasion. They provide a direct link between previously isolated catchments and may modify the habitat conditions of the receiving waters such that they become more favourable for the establishment of invasive species. Combined, IBWT and invasive species will intensify the stress upon native species and ecosystems. Using the Severn and Thames Rivers –two of the largest river systems in Great Britain—as a case study, here we assess the potential influence of IBWT on the expansion of invasive species and thus their impact on biodiversity conservation. The Thames Valley is subject to extensive water abstraction, and an increasing population means that supplemented flow from the River Severn is being considered. Multi-scale Suitability Models, based on climate and water chemistry respectively, provided novel evidence that there is serious risk for further spread of invasive species in the focus area, particularly of the quagga mussel, a recent invader of the Thames River. Native freshwater mussels are particularly vulnerable to changing environmental conditions, and may suffer the decrease in alkalinity and increase in sedimentation associated with an IBWT from the lower Severn to the upper Thames. Regional models suggest considerable overlap between the areas suitable for three vulnerable native freshwater mussels and the expansion of invasive species that negatively impact upon the native mussels. This study illustrates the use of novel spatially-explicit techniques to help managers make informed decisions about the risks associated with introducing aquatic invasive species under different engineering scenarios. Such information may be especially important under new legislation (e.g. EU Invasive Species Regulation No 1143/2014) which increases the responsibility of water managers to contain and not transfer invasive species into new locations. [ABSTRACT FROM AUTHOR]

Risk assessment currently lacks reliable tools that can be applied across a range of environmental contexts to predict the success and impact of invasive species. A comparative functional response approach may offer insight and predictive power regarding the impacts of invasive bivalves. This could prove valuable in the management of invasive species that drive losses in ecosystem function and biodiversity. We conducted feeding experiments to assist in predicting the relative impact of two sympatric species of dreissenid mussel, the zebra and quagga (Dreissena polymorpha and D. rostiformis bugensis, respectively). Feeding rates and functional responses were calculated for each species under different 'contexts', including ranges of algal concentrations and temperatures. Clearance rates ranged from 10 to 44 ml/g mussel/h. Both species exhibited type I functional responses across all contexts studied. There were no differences in the clearance rates or functional responses between species at 4 °C and 12°C. Thus, the competitive exclusion of zebra mussels by quagga mussels seen in nature does not appear to be driven by disparities in feeding efficiencies. Both species demonstrated elevated functional responses at the highest temperature (24 °C) compared with the lowest temperature (4 °C). Zebra mussels showed a significantly higher clearance rate than quagga mussels at 24 °C. We conclude that total species abundance, rather than changes in species dominance, is likely to be more important for net species impact. Functional responses may offer considerable explanatory and predictive power under certain contexts; they are particularly fitting for sessile invasive bivalves due to their high feeding rates and the seasonal changes in algae abundance they experience. [ABSTRACT FROM AUTHOR]

Litterfall is an important resource subsidy for lake ecosystems that primarily accumulates in littoral zones. Bivalves are abundant within littoral zones and may modify the effects of terrestrial resource subsidies through trophic interactions and engineering their surrounding habitat. Leaf inputs to lakes and freshwater mussel abundances are changing throughout the boreal ecoregion so we set out to investigate how the co-occurring benthic community might respond. We set up an in situ mesocosm experiment in Ramsey Lake, Sudbury, ON, Canada. Mesocosms contained sediments of either 5% or 35% terrestrial organic matter (tOM), into which we placed mussels ( Elliptio complanata ) at differing densities (0, 0.4 and 2 mussels m − 2 , with a sham mussel treatment at 0.4 mussels m − 2 ). Over one month we recorded the sediment chemistry (dissolved organic carbon, nitrogen and phosphorus), littoral organisms (benthic algae and zooplankton) and mussel growth. At high mussel densities we recorded a 90%, 80%, 45% and 40% reduction in phosphorus, dissolved organic carbon, nitrogen and benthic diatoms, respectively, whereas at low mussel densities we observed a 3-fold increase in zooplankton. We discuss that these results were caused by a combination of bioturbation and trophic interactions. Benthic diatom concentrations were also reduced by 20% in sediments of 35% tOM, likely due to shading and competition with bacteria. Mussel growth increased at high mussel densities but was offset at high tOM, likely due to the organic matter interfering with filter feeding. Our results suggest that mussels can alter the geochemical composition of sediments and abundances of associated littoral organisms, in some cases regardless of tOM quantity. Therefore, the dominant top-down control exerted by freshwater mussels may outweigh bottom-up effects of tOM additions. Generally, our study reveals the importance of considering dominant species when studying the effects of cross-ecosystem resource fluxes. [ABSTRACT FROM AUTHOR]

Protected areas ( PAs) are intended to provide native biodiversity and habitats with a refuge against the impacts of global change, particularly acting as natural filters against biological invasions. In practice, however, it is unknown how effective PAs will be in shielding native species from invasions under projected climate change. Here, we investigate the current and future potential distributions of 100 of the most invasive terrestrial, freshwater, and marine species in Europe. We use this information to evaluate the combined threat posed by climate change and invasions to existing PAs and the most susceptible species they shelter. We found that only a quarter of Europe's marine and terrestrial areas protected over the last 100 years have been colonized by any of the invaders investigated, despite offering climatically suitable conditions for invasion. In addition, hotspots of invasive species and the most susceptible native species to their establishment do not match at large continental scales. Furthermore, the predicted richness of invaders is 11%-18% significantly lower inside PAs than outside them. Invasive species are rare in long-established national parks and nature reserves, which are actively protected and often located in remote and pristine regions with very low human density. In contrast, the richness of invasive species is high in the more recently designated Natura 2000 sites, which are subject to high human accessibility. This situation may change in the future, since our models anticipate important shifts in species ranges toward the north and east of Europe at unprecedented rates of 14-55 km/decade, depending on taxonomic group and scenario. This may seriously compromise the conservation of biodiversity and ecosystem services. This study is the first comprehensive assessment of the resistance that PAs provide against biological invasions and climate change on a continental scale and illustrates their strategic value in safeguarding native biodiversity. [ABSTRACT FROM AUTHOR]

Freshwater mussels (Bivalvia: Unionidae) are often described as ecosystem engineers, with the capacity to alter abiotic habitats; this can facilitate certain macroinvertebrate taxa, increasing biodiversity and potentially altering community composition. Mussel species are often implicitly considered to be broad ecological equivalents, with similar impacts on abiotic environments and benthic communities. This assumption of redundancy is important in conservation approaches that aim to preserve ecosystem functioning, rather than species identity. We tested this assumption of equivalence in two species of subtropical freshwater mussels, Lamellidens marginalis and Parreysia caerulea, studying the associations between these mussel species and macroinvertebrate communities.We measured mussel density and abundance of macroinvertebrates, identified to family level, at 50 sites within Dhanmondi Lake, a heavily polluted sub‐tropical urban lake in Dhaka, Bangladesh. We investigated the associations of mussel density on different macroinvertebrate families, which we further classified into functional feeding groups (predators, scrapers, collectors and shredders).We found that densities of the two mussel species were negatively correlated in the 1–3‐m nearshore zone; average density of Lamellidens was 46.4 ± SE 3.6 individuals/0.25 m2, and average density of Parreysia was 6.4 ± SE 1.4 individuals/0.25 m2. In total, 2319 Lamellidens and 320 Parreysia specimens were recorded. Sites containing higher densities of Lamellidens had greater similarity in macroinvertebrate community composition, while there was no effect for Parreysia. Particular macroinvertebrate families and functional feeding groups were also associated with mussels; the majority of significant associations were with Lamellidens but not Parreysia. The clearest associations were with predators and scrapers, which increased in abundance with Lamellidens density.This provides support for a possible role for mussels in structuring freshwater invertebrate communities and emphasises the importance of species identity in these effects, with one possible keystone species (Lamellidens) largely accounting for mussel–invertebrate associations. While microhabitat variables (shading and sediment type) were poor predictors of abundance in any invertebrate taxa (including mussels), manipulative studies are needed to disentangle the direct effects of mussels from the role of overlapping habitat preference between mussels and other invertebrates.Our results highlight the importance of species identity in patterns of community composition, particularly for ecosystem engineer species. We also reinforce the need to test the assumption of ecological redundancy within communities. [ABSTRACT FROM AUTHOR]

The outcome of multiple invasions from a common origin may lead to facilitative interactions because the invaders have co-evolved under similar environmental conditions. This outcome is often referred to as invasional meltdown, with a resultant increase in invasive species and a decline in native species richness and abundance., This study seeks to assess the full scope of the threat posed by a high-risk group of 23 freshwater invaders originating from the Ponto-Caspian region (south-east Europe) across Great Britain. Ponto-Caspian invaders constitute a group of special concern because they have recently caused a large-scale invasion into western Europe., According to a literature review, 76% of reported interactions between Ponto-Caspian invaders are positive (mostly provision of food and commensalism) or neutral (habitat partitioning). Negative interactions (mostly predation) were rare, thus highlighting the ability of Ponto-Caspian invaders to coexist., At least 14 out of the 23 Ponto-Caspian organisms investigated are well-established in the Rhine estuary and Dutch ports. Four of them ( Hemimysis anomala, Dikerogammarus villosus, D. haemobaphes and Hypania invalida) have recently established in Great Britain. Regression models suggest the rest are under a critical risk of being transported, with four species predicted to have arrived already to Great Britain: Echinogammarus ischnus, Jaera istri, Limnomysis benedeni and D. bispinosus., According to species distribution models, the cumulative risk of invasion of multiple Ponto-Caspian species, thus invasional meltdown, is highest in the south-east of England and decreases to the north and west., Great Britain might be on the brink of invasional meltdown, and as a consequence, confronting the problem of Ponto-Caspian invasive species is a vital element for national biosecurity., Synthesis and applications. The predictive models and maps developed in this study provide a means for an evidence-based prioritization of species and habitats for the management of existing and future invasions of Ponto-Caspian species. This integrated approach can be easily applied to risk assess other groups of species and habitats. [ABSTRACT FROM AUTHOR]

Aquatic invasive species are a growing concern to environmental managers because of their diverse impacts on aquatic biodiversity and high eradication costs, necessitating effective management policies. In this study, we evaluate the ability of environmental and socio-economic factors to predict the risk of invasion in Great Britain and Ireland of 12 potential aquatic invaders covering all major aquatic groups. Despite their potential to inform risk assessments, this is the first time socio-economic factors related to propagule pressure have been specifically integrated in distribution modelling., Species distribution models ( SDM, MaxEnt algorithm) were calibrated with a set of environmental factors (e.g. bioclimatic, geographical and geological) and integrated with socio-economic (e.g. human influence index, population density, closeness to ports) predictors., The inclusion of socio-economic factors in SDM did not affect accuracy scores ( AUC already >0·90), but their effects were more pronounced in spatial predictions, resulting in up to a sixfold amplification of the area predicted suitable for each species. Despite the inclusion of potential surrogates of water chemistry (e.g. geology) and propagule pressure (e.g. population density), temperature-related variables were most important predictors of aquatic species' distributions., According to SDM, the environmental suitability for a suite of invaders belonging to different taxonomic groups and regions of origin is greatest in east and south-east England and decreases towards the north and west. Multiple invasions in this region are of special concern, as species are known to modify their habitat facilitating subsequent invasions, thereby potentially exacerbating their impacts., Major management regions to be prioritized in monitoring programmes include the Humber, Thames and Anglian River Basin Districts. Species of special concern include a mysid ( Hemimysis anomala) , a gammarid ( Dikerogammarus villosus), a plant ( Ludwigia grandiflora) and two crayfishes ( Procambarus clarkii and P. fallax)., Synthesis and Applications. The inclusion of socio-economic factors in species distribution models has the potential to improve predictions of areas under a highest risk of multiple invasions and to help disentangle the complex interplay between biological invasions and global environmental and socio-economic processes. Such understanding is pivotal to prioritize limited resources for the optimum prevention and control of biological invasions. [ABSTRACT FROM AUTHOR]

Abstract: Climate change and invasive species are two major biodiversity threats expected to provoke extinctions of many species in the future. This study evaluates the joint threat posed by climate change and two invasive species: the zebra mussel (Dreissena polymorpha) and the signal crayfish (Pacifastacus leniusculus), on the distribution of two endangered freshwater species: the depressed river mussel (Pseudanodonta complanata) and the white-clawed crayfish (Austropotamobius pallipes), at the scale of Europe. We expected the native species to experience a gradual contraction over time in their geographic range size, while the invasive species would maintain or increase their spread; therefore, their overlap would increase, further threatening the conservation of the native species. To test these three hypotheses, ensemble species distribution models (SDMs) were calibrated with current distributions and projected onto present and 2050 future climatic scenarios. In agreement with our expectations, the 2050 scenarios suggested D. polymorpha may strongly benefit from climate changes (increase of 15–20% in range size), while the depressed river mussel would experience a considerable loss (14–36%), the overlap between both mussels increasing up to 24%. Although both crayfishes were predicted to be negatively affected by climate changes, the contraction was more severe for the invasive P. leniusculus (up to 32% decrease in range size). Moreover, the overlap between both crayfishes decreased by 13–16%, which may reduce the pressure upon the native A. pallipes. This study illustrates how SDMs can assist in management of endangered species over large spatial and temporal scales by identifying current and future areas of shared bioclimatic suitability and potential refugia. [Copyright &y& Elsevier]

Abstract: Algal biofuel production offers great potential as a sustainable source of bioenergy without competing for arable land with food crops. However, many challenges must be overcome to enable this to be done commercially at the scale required to produce biofuels. Here we explain how an understanding of algal ecology could lead to more reliable raceway-based microalgal cultivation, drawing from established principles of community ecology to highlight practices that could be applied to protect algal cultures from unwanted contaminants. Using theoretical concepts, we show how an understanding of local community dynamics at the species level might be used to enhance productivity by encouraging certain community structures over others. [Copyright &y& Elsevier]

Abstract: The toxic effects of low level metal contamination in sediments are currently poorly understood. We exposed different sized Asian clams, Corbicula fluminea, to sediment spiked with environmentally relevant concentrations of either zinc, cadmium or a zinc–cadmium mixture for one week. This freshwater bivalve is well suited for sediment toxicity tests as it lives partly buried in the sediment and utilises sediment particles as a food resource. After one week, the whole tissue composition of low molecular weight metabolites was analysed by nuclear magnetic resonance spectroscopy (NMR) and gas chromatography–mass spectrometry (GC–MS). The condition index (ratio of tissue dry weight to volume inside the shell valves) was also measured. Small and large clams were clearly differentiated by their metabolic composition and the two size classes showed opposite responses to the mixture spiked sediment. No effects of zinc alone on the metabolome were found and cadmium only influenced the smaller size class. The main perturbations were seen in amino acid and energy metabolism, with small clams using amino acids as an energy resource and larger clams primarily drawing on their larger storage reserves of carbohydrates. Our study demonstrates that metabolomics is a useful technique to test for low level toxicity which does not manifest in mortality or condition index changes. The differing effects between the two size classes stress that it is important to consider age/size when conducting metabolomic and ecotoxicology assessments, since testing for the effects on only one size class makes it more difficult to extrapolate laboratory results to the natural environment. [Copyright &y& Elsevier]

Non-indigenous crayfish often have major ecological impacts on invaded water bodies, and have contributed to the decline of native crayfish species throughout Europe. The American signal crayfish, Pacifastacus leniusculus, is the most widespread invasive crayfish in Great Britain, where the zebra mussel, Dreissena polymorpha, is similarly an invasive pest species. The potential for the American signal crayfish to regulate zebra mussel populations was investigated through a series of laboratory experiments. Crayfish were found to be highly size selective, consuming significantly more of the smallest size class of zebra mussels offered (7-12 mm), over medium (16-21 mm) and large (25-30 mm). Crayfish feeding rate on zebra mussels was not altered when mussels were presented clumped together in natural druses compared with mussels in a disassembled druse. Crayfish spent significantly more time foraging when mussels were unattached, and a greater proportion of attacks were on medium and large than on small mussels (83% of attacks were on medium and large mussels when unattached as opposed to 47% when on druses). Individual crayfish feeding rate decreased significantly at densities of > ~5 crayfish m. Signal crayfish are, therefore, unlikely to be able to significantly impact established populations of zebra mussels in the wild, although zebra mussels have the potential to provide crayfish with a substantial food source. [ABSTRACT FROM AUTHOR]

The European bitterling, Rhodeus amarus, is a non-indigenous fish species in British fresh waters. It lays its eggs in unionid mussels which themselves are vulnerable to fouling by the non-indigenous zebra mussel, Dreissena polymorpha. Observations from an unmanipulated natural system showed that only 27% of zebra mussel-fouled Unio pictorum hosted bitterling, while 47% of unfouled U. pictorum hosted bitterling. We conducted a field experiment in the River Great Ouse catchment, Cambridgeshire, England in May–June 2007 and 2008 to quantify the impact of zebra mussels on bitterling load in host mussels. Zebra mussel-fouled unionids were significantly less likely to host bitterling than unfouled unionids. The number of unionids hosting bitterling did not differ significantly whether the zebra mussels fouling the unionid were alive or dead. Bitterling appeared to discriminate against zebra mussel-fouled unionids less as the 2007 breeding season advanced, potentially because preferred unfouled unionids had a higher bitterling load, and were therefore relatively lower quality hosts than at the start of the breeding season. [ABSTRACT FROM AUTHOR]

Most species of freshwater mussels (Unionoida) show a wide variability in shell form and size but an understanding of which factors determine unionoid morphology is poor. We identified ecophenotypic trends in shell and internal characters within three unionoid species from two habitat types (marinas and river) of the River Thames, UK, using traditional and modern morphometric techniques. In marinas, all species grew to larger maximum sizes than in the river, which might be a result of higher temperatures and phytoplankton densities in marinas. Unio pictorum in marinas was more elongated than in the river and Fourier shape analysis revealed a trend from dorsally arched river specimens to straight dorsal and pointed posterior margins in marina individuals. The degree of shell elongation and shape of dorso-posterior margin were not associated with sediment composition, but were associated with the different hydrological characters of the two habitat types. Relative shell width was a poor indicator of collection site and influenced by allometric growth. Unlike U. pictorum, a difference in shell elongation of marina and river mussels could not be detected in Unio tumidus and Anodonta anatina. However, all three species showed the same trends regarding the shape of the dorso-posterior shell margin. This shell character may thus have broad ecological significance and could have considerable utility to palaeontologists, taxonomists, and conservation biologists. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 814–825. [ABSTRACT FROM AUTHOR]

Abstract: The zebra mussel (Dreissena polymorpha) is a notorious freshwater biofouling pest, and populations of the species can alter aquatic environments through their substantial filtration capabilities. Despite the ecological importance of zebra mussel filtration, many predictions of their large-scale effects on ecosystems rely on extrapolations from filtration rates obtained in static laboratory experiments, not accounting for natural mussel densities, boundary layer effects, flow rates or elevated algal concentrations. This study used large-scale industrial flume trials to investigate the influence of these factors on zebra mussel filtration and proposes some novel industrial applications of these findings. The flume trials revealed some of the highest zebra mussel clearance rates found to date, up to 574±20mlh−1 g−1 of wet tissue mass. Under low algal concentrations, chlorophyll a removal by zebra mussels was not proportional to mussel density, indicating that field rates of zebra mussel grazing may be much lower than previous studies have predicted. Increasing ambient velocities up to 100mls−1 (∼4cms−1) led to increased clearance rates by zebra mussels, possibly due to the replenishment of locally depleted resources, but higher velocities of 300mls−1 (12cms−1) did not lead to further significant increases in clearance rate. When additional algal cultures were dosed into the flumes, chlorophyll a removal increased approximately logarithmically with zebra mussel density and there were no differences in the clearance of three different species of alga: Ankyra judayi, Pandorina morum and Cyclotella meneghinia. Some novel industrial uses of these zebra mussel filtration studies are proposed, such as: (1) helping to inform models that predict the large-scale grazing effects of the mussels. [Copyright &y& Elsevier]

The widespread invasion of freshwaters by the zebra mussel, Dreissena polymorpha, during the last 2 decades has made it one of the world's most economically and ecologically important pests. Since arriving in the North American Great Lakes in the 1980s, zebra mussels have become a major biofouler, blocking the raw water cooling systems of power stations and water treatment works and costing U.S. $1-5 billion per year. Despite the development of numerous control methods, chlorination remains the only widespread and licensed technique. Zebra mussels are able to sense chlorine and other toxins in their surrounding environment and respond by closing their valves, thus enabling them to avoid toxic effects for up to 3 weeks. Furthermore, prolonged dosing of chlorine in raw water produces ecotoxic trihalomethanes (THMs) by reaction with organic material in the water. We have developed a novel, environmentally safe, and effective method for controlling the zebra mussel: the BioBullet. Our method uses the encapsulation of an active ingredient (KCI) in microscopic particles of edible material. The mussels' natural filtering ability then removes and concentrates the particles from the water, without stimulating the valve- closing response. By using the mussels' filtering behavior to concentrate BioBullets the absolute quantity of active ingredient added to the water can be reduced substantially. Our approach allows us to engineer the particles to break up and dissolve completely within a few hours, thus eliminating the risk of polluting the wider ecosystem. We demonstrate that the effectiveness of a toxin in the control of biofouling filter-feeders can be enhanced greatly by using our technique. This paves the way for a new approach to the control of some of the world's most important economic pests. [ABSTRACT FROM AUTHOR]

This paper reviews the current, apparently rapid spread of zebra mussels (Dreissena polymorpha) in Britain, discusses the possible causes of this spread, considers the potential ecological consequences, and looks at what measures could be undertaken to minimise the impacts of zebra mussels and other invasive pests in Britain''s freshwaters. Five out of 27 major water companies reported increases in their regions between 2000 and 2002 and a further three acknowledged their presence. Increases were also reported by the Environment Agency, Broads Authority, angling clubs and boatyards. No one interviewed reported a decrease in zebra mussels between 2000 and 2002. The most notable increases have been in southern, central and eastern England. A newly recorded population of zebra mussels in the River Darent, Kent, contained zebra mussels in dense mats of up to 11,000 individuals m-2 and up to 20 cm in depth. There is evidence that the ecology of recently invaded sites has been deleteriously affected. A fishing lake in Lancashire has experienced increased water clarity and reduced fish biomass coincidental with the arrival of zebra mussels, while a newly recorded population in Barden Lake, Kent, appears to be having a deleterious impact on native unionid mussels, particularly the swan mussel (Anodonta cygnea) and, more, recently the painter''s mussel (Unio pictorum). Repeated surveys in the River Thames, River Great Ouse and Barden Lake showed that the proportion of unionid mussels infested by zebra mussels had increased significantly in all sites studied during the past one to five years. [Copyright &y& Elsevier]

This study aimed to elucidate the mechanism of glochidial release in Unio pictorum (L., 1758) and U. tumidus Philipsson, 1788, and thus interpret the confused reports of unionine reproduction in the literature. Both species release mature, hooked glochidia on mucous threads, resembling a pearl necklace. Individual threads can reach 15 cm in length and carry c. 500 glochidia. Under hypoxic conditions both species released conglutinate-like structures comprising c. 500 eggs and immature, unhooked glochidia. The conglutinate-like structures released by U. pictorum and U. tumidus are coloured yellow and white, respectively. Increased temperature did not induce the release of conglutinates. The conglutinate-like structures are unlikely to be involved in increasing reproductive success by attracting host fishes. Rather, the premature evacuation of the gill contents may relieve the respiratory burden on adult mussels under hypoxic stress. Ambient hypoxia during the reproductive season may help explain the irregular recruitment success of relatively long-lived mussels, such as U. pictorum and U. tumidus. [ABSTRACT FROM PUBLISHER]

• Quagga mussels may affect biotic and abiotic characteristics of invaded reservoirs. • Quagga mussel establishment led to reduced cyanobacteria and diatom abundance. • Aphanizomenon sp. abundance decreased in quagga mussel invaded reservoirs. • Soluble reactive phosphorus concentrations increased in invaded reservoirs. • Changes in nutrients and phytoplankton communities may affect reservoir management. Invasive quagga mussels (Dreissena rostriformis bugensis) are an emerging threat to the functioning and management of freshwater ecosystems. Quagga mussels were first recorded in the UK in 2014 and have subsequently established at high densities in a number of major reservoirs. Through implementing a Progressive-Change BACIPS (Before-After-Control-Impact Paired Series) analysis, we found that the following trends were observed following quagga mussel establishment: reduced diatom and cyanobacteria abundances; increased soluble reactive phosphorus and reactive silica concentrations; and reduced abundances of Aphanizomenon sp., a potentially toxic cyanobacterium. We also found reservoirs with established quagga mussel populations experienced slightly increased overall chlorophyll a concentration but no changes in turbidity or Microcystis sp. abundance, which are often considered common indicators of dreissenid invasion. Our results show that Progressive-Change BACIPS analysis is a powerful tool which can be used to interrogate industry standard long-term datasets of water quality metrics in order to identify and quantify the impacts of invasive species when the approximate timeframe of species arrival is known. We also demonstrate that quagga mussels may have had significant effects on reservoir ecosystems which, primarily through their impacts on phytoplankton communities, may have implications for reservoir management. [Display omitted] [ABSTRACT FROM AUTHOR]

Identification of ecosystem services, i.e. the contributions that ecosystems make to human well‐being, has proven instrumental in galvanising public and political support for safeguarding biodiversity and its benefits to people. Here we synthesise the global evidence on ecosystem services provided and disrupted by freshwater bivalves, a heterogenous group of >1200 species, including some of the most threatened (in Unionida) and invasive (e.g. Dreissena polymorpha) taxa globally. Our systematic literature review resulted in a data set of 904 records from 69 countries relating to 24 classes of provisioning (N = 189), cultural (N = 491) and regulating (N = 224) services following the Common International Classification of Ecosystem Services (CICES). Prominent ecosystem services included (i) the provisioning of food, materials and medicinal products, (ii) knowledge acquisition (e.g. on water quality, past environments and historical societies), ornamental and other cultural contributions, and (iii) the filtration, sequestration, storage and/or transformation of biological and physico‐chemical water properties. About 9% of records provided evidence for the disruption rather than provision of ecosystem services. Synergies and trade‐offs of ecosystem services were observed. For instance, water filtration by freshwater bivalves can be beneficial for the cultural service 'biomonitoring', while negatively or positively affecting food consumption or human recreation. Our evidence base spanned a total of 91 genera and 191 species, dominated by Unionida (55% of records, 76% of species), Veneroida (21 and 9%, respectively; mainly Corbicula spp.) and Myoida (20 and 4%, respectively; mainly Dreissena spp.). About one third of records, predominantly from Europe and the Americas, related to species that were non‐native to the country of study. The majority of records originated from Asia (35%), with available evidence for 23 CICES classes, as well as Europe (29%) and North America (23%), where research was largely focused on 'biomonitoring'. Whilst the earliest record (from 1949) originated from North America, since 2000, annual output of records has increased rapidly in Asia and Europe. Future research should focus on filling gaps in knowledge in lesser‐studied regions, including Africa and South America, and should look to provide a quantitative valuation of the socio‐economic costs and benefits of ecosystem services shaped by freshwater bivalves. [ABSTRACT FROM AUTHOR]

Parasites can indirectly affect ecosystem function by altering host phenotype, but the trait‐mediated impacts of parasitism at an ecosystem level remain poorly characterised. However, understanding the influence of parasites is central to understanding the ecosystem services provided by host species, especially in an era of global environmental change.We examined the effect of native (the trematode Rhipidocotyle campanula) and invasive (the bitterling fish Rhodeus amarus) parasites, and their interaction, on the clearance rates of unionid mussels, a dominant ecosystem‐engineering group that modify freshwater ecosystems worldwide. We used a combination of field experiments, laboratory experiments and ecological simulations to demonstrate the phenotypic impact of parasites on the functional response of two mussel species across an environmental gradient (suspended particle concentration), and extended this with host and parasite community data to demonstrate the consequences for a real‐world ecosystem, the Old West River in Cambridgeshire, England.Both parasites altered the clearance rates of their hosts but in contrasting fashion: while R. campanula increased host clearance rates relative to uninfected conspecifics under all conditions, R. amarus supressed clearance rates at high suspended particle concentrations (eutrophic conditions) but elevated them otherwise. The parasites displayed different infection patterns in the two host species, and the invasive R. amarus rarely co‐infected mussels with R. campanula.Given their disparate effects, the parasites' distributions reversed the relative filtration capacity of the two host species under high vs. low concentrations of suspended particles, demonstrating how differences between the infection patterns of native and invasive parasites, as well as their individual effects, need to be considered. Overall, the proportion of daily river discharge filtered by the combined mussel community changed by up to 96% in the presence of parasites. By incorporating multiple host species and multiple parasite species, we provide ecologically relevant evidence for the trait‐mediated effects of parasites on ecosystem processes.Our study demonstrates that parasitism can significantly alter wider ecosystem processes through changing the phenotype of their host. Future work on ecosystem function should take parasitism into account, and consider both trait‐mediated and density‐mediated effects. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Coastal estuaries are especially vulnerable to the arrival and establishment of invasive aquatic species (IAS) as they are often the receiving locations of ship-based introductions. Rapid response tools, such as mechanical or chemical treatments to capture, remove, and contain of IAS, are needed to prevent subsequent spread into adjacent marine and freshwater systems. Abrupt salinity change, created when infrastructure in estuaries situated at the proximity of river mouths is operated, offers a novel, low-cost and environmentally friendly method for potentially controlling IAS. We investigated the use of osmotic shock to control the invasive brackish water clam Rangia cuneata that is quickly spreading through Europe. Clams were exposed in the laboratory to eight salinity concentrations ranging from 0.5 to 32.0‰ and monitored for 60 days. Saline shock, but not freshwater shock, could control R. cuneata. Salinities >26‰ killed 95% R. cuneata in two weeks. All specimens exposed to full strength seawater (32‰) were killed within 30 days. At lower salinities, clams collected from the most freshwater locality (1.2‰) showed lower mortality than clams from the most saline site (3.1‰). Furthermore, even modest increases in salinity during spawning periods of R. cuneata may prevent recruitment. Given the vulnerability of coastal estuaries to introduction of IAS, saline flushing presents a novel and effective management tool for many species. Image 1 • Saline, but not freshwater, shock could control invasive brackish R. cuneata. • All clams exposed to full strength seawater (32‰) were killed. • Salinities > 26‰ killed 95% R. cuneata in two weeks. [ABSTRACT FROM AUTHOR]

The shell morphology and population dynamics of the five British Unionidae are compared within a sympatric population. Pseudanodonta complanata is distinguished from Anodonta anatina and A. cygnea by the hinge length-shell length relationship; this morphological distinction may serve as a useful tool in the identification of this threatened species. The shell length at a given annulus was remarkably similar for all five species, although the symptotic length is reached most quickly in P. complanata and Unio pictorum. P. complanata is relatively short-lived and attains the lowest maximum length, while A. cyanea lives more than twice as long and attains almost double the length of P. complanata. Unio spp. have a short gravid season over the summer, while Anodonta spp. have a long gravid period, lasting from Autumn through to Spring. Unlike other members of the Anodontinae, P. complanata has a short breeding season, overlapping with that of the Unio spp. [ABSTRACT FROM PUBLISHER]

In the present study, we evaluated the effects of different environments on the filtering rate (FR), mortality, and biodeposition (BD) of the freshwater mussel Unio douglasiae in bloom waters containing the toxic cyanobacterium Microcystis aeruginosa. The mean FR of 19 selected individuals (shell length, 5.0–9.8 cm) was 0.30 ± 0.03 L g − 1 h − 1 (range = 0.24 – 0.35 L g − 1 h − 1 ). Shell length was strongly correlated with both net and gross BD of mussels (P < 0.0001). The mean FR was higher in river water (0.405 ± 0.052 L g − 1 h − 1 ) than in lake water (0.304 ± 0.051 L g − 1 h − 1 ). In contrast, the BD of mussels was higher in RW (0.671 ± 0.609 mg g − 1 h − 1 ) than in LW (0.275 ± 0.027 mg g − 1 h − 1 ). For algal species, the FR of mussels ranged from 0.114 ± 0.024 to 0.553 ± 0.019 L g − 1 h − 1 . The FR of U. douglasiae was higher in river water (mainly diatoms), whereas BD was higher in lake water (mainly Microcystis). U. douglasiae did not prefer toxic M. aeruginosa, which was significantly accumulated in pseudofaeces and faeces. The maximum FR of U. douglasiae in algal bloom water was recorded at a water temperature of 25°C and water depth of 50 cm. Moreover, the in situ mortality of U. douglasiae was strongly affected by water temperature and nitrogen concentration. Overall, U. douglasiae can enhance water quality in eutrophic areas by removing dominant cyanobacteria, although its removal efficiency depends on environmental parameters and site of introduction. [ABSTRACT FROM AUTHOR]

The expansion of Invasive Alien Species (IAS) is a growing concern to the UK water industry because of their diverse impacts on water quality, infrastructure and eradication costs. New regulations reinforcing the industry's responsibilities beyond operational costs, coupled with continued range expansion and establishment of new IAS will increase damages. To tackle IAS effectively, the water industry requires reliable information about which species pose the greatest risk to operations and which areas are most vulnerable to invasion. Here we assess potential biosecurity threats for the 24 water companies in the UK using well-established modelling research techniques such as risk assessment and distribution modelling. Using a consensus approach with environmental managers and water companies, we identified 11 IAS of concern for the UK water industry, including five plants, three crustaceans, two molluscs and one fish. These invaders pose important hazards in terms of water quality, flood protection, human health, integrity of infrastructures, recreational and aesthetic values, amongst others. We used distribution models to predict their potential expansion under current and future 2050 climate scenarios within each of the 24 water companies in the UK. Water companies in the South East of England (Cambridge Water, Anglian Water, Affinity Water and Thames Water) are under the highest risk of invasional meltdown from multiple IAS, both now and under future scenarios. The quagga mussel poses the most serious risk of immediate spread and may exacerbate the impacts of the widespread zebra mussel for the water industry. The information generated in this study can support the prioritization of species and regions at risk, so that funds for prevention and eradication of invasions are well allocated. Ultimately, this study demonstrates that scientific risk assessments, usually restricted to the academic and public sectors, can be extremely useful to guide decision-making by the private sector. Image 1 • Invasive Alien Species cause important changes in water quality. • We identified 11 IAS of concern to the water industry through a consensus approach. • We modelled their potential expansion under current and future climate scenarios. • Water companies in the SE of England will bear the highest costs of control of IAS. • Our approach can cost-effectively prioritize species and regions at risk. [ABSTRACT FROM AUTHOR]

Antarctica, an isolated and long considered pristine wilderness, is becoming increasingly exposed to the negative effects of shipborne human activity, and especially the introduction of invasive species. Here, we provide a comprehensive quantitative analysis of ship movements into Antarctic waters and a spatially explicit assessment of introduction risk for nonnative marine species in all Antarctic waters. We show that vessels traverse Antarctica's isolating natural barriers, connecting it directly via an extensive network of ship activity to all global regions, especially South Atlantic and European ports. Ship visits are more than seven times higher to the Antarctic Peninsula (especially east of Anvers Island) and the South Shetland Islands than elsewhere around Antarctica, together accounting for 88% of visits to Southern Ocean ecoregions. Contrary to expectations, we show that while the five recognized "Antarctic Gateway cities" are important last ports of call, especially for research and tourism vessels, an additional 53 ports had vessels directly departing to Antarctica from 2014 to 2018. We identify ports outside Antarctica where biosecurity interventions could be most effectively implemented and the most vulnerable Antarctic locations where monitoring programs for high-risk invaders should be established. [ABSTRACT FROM AUTHOR]

The naiads, large freshwater mussels (Unionida), have very long life spans, are large-bodied, and produce thousands to millions of larvae (glochidia) which typically must attach to host fish tissues to metamorphose into a juvenile mussel. Glochidia develop within a female's marsupial gill demibranch, thus their number is restricted by female size. However, larger mussels acquire more energy, which could be invested in either larger-sized glochidia, in a more glochidia, or a combination of both. The high level of host specialization seen in many naiads may constrain glochidial size and shape around a narrow optimum, while naiads that use a wide range of host fishes may be predicted to possess greater plasticity in glochidial morphology. In this paper, we investigated the relationship between maternal body size and progeny body size and shape, aided by modern digital microscopy. We analyzed the between- and within- species variation of glochidia size and shape relative to female size in four widespread species of European naiads: Anodonta anatina, Anodonta cygnea, Unio crassus and Unio tumidus. Whereas the total reproductive output is collinear with female body size, substantial differences between species in glochidia size were found within genus Anodonta, but not genus Unio where glochidial size is remarkably consistent. The glochidial shape, however, differed within both Unio and Anodonta. We interpret this constant within-species glochidial size in Unio as reflecting a constraint imposed by the likelihood of successful transmission onto and off from a narrow range of hosts, whereas their shape seems to be less constrained. The Anodonta species, inhabiting a wide spectrum of habitats and using more than twice the number of fish hosts than Unio spp., have larger glochidia with greater variation in size and shape. Our results suggest that measures of glochidial variability may also serve as an indicator of host specificity in other naiads. [ABSTRACT FROM AUTHOR]

Land‐use change and agricultural expansion have caused marked biodiversity loss in Southeast Asia, but impacts on freshwater communities have been very little studied. Semi‐aquatic bugs are abundant in streams, provide prey for many other animals, and are sensitive to environmental change, making them a relevant group for studying land‐use change.We investigated the effects of logging and conversion of forest to oil palm plantations on semi‐aquatic bugs in Sabah, Malaysia, and the potential value of retaining riparian buffer strips in plantations, by sampling across 12 rivers along an existing land‐use gradient. We recorded catchment, riparian, and stream‐scale environmental variables and surveyed semi‐aquatic bugs within streams in old‐growth forest, logged forest, and oil palm plantation with (OPB) and without buffer strips (OP). We recorded the abundance, richness, total biomass, and proportion of juveniles and winged adult individuals of all species, together with the sex ratio of a common morphospecies (Ptilomera sp.), as possible indicators of disturbance effects.Average abundance and average richness, but not total biomass, of all semi‐aquatic bugs were lower in areas with higher habitat disturbance. In particular, average abundance in old‐growth forest was more than two, four, and six times higher than that in logged forest, OPB, and OP, respectively. Average richness in old‐growth forest was higher than in logged forest by two species, but more than two and three times higher than in OPB and OP, respectively.The presence of riparian buffer strips in oil palm had little effect on the abundance and richness of semi‐aquatic bugs. We found no significant differences in the proportion of juveniles, winged adult individuals, or the sex ratio of Ptilomera sp. along the disturbance gradient.In conclusion, oil palm plantations were associated with lower average abundance and richness of semi‐aquatic bugs than forest sites, but community composition did not differ markedly between logged and old‐growth forests. We also found that the forested buffer strips maintained within our oil palm plantation study sites did not protect forest species of semi‐aquatic bugs. Maintaining forest may therefore provide the best option for the conservation of semi‐aquatic bugs, but further studies of the effects of land‐use change and management options are needed across Southeast Asia. [ABSTRACT FROM AUTHOR]

Freshwater mussels are one of the most endangered animal groups globally, making them a high conservation priority. Conservationists increasingly employ translocation or captive breeding procedures to support ailing populations, and the ecosystem engineering capabilities of mussels are being increasingly harnessed in bioremediation projects. However, there is little consideration of the risk of pathogen transmission when moving mussels from hatcheries or wild donor populations into new habitats. This is of significant concern as recent developments suggest parasites and diseases are highly prevalent and have contributed to several mass population‐level die‐offs. Here, we explicitly highlight the risks of pathogen spread in mussel translocations, explore how these risks are mediated, and provide recommendations for both research and action to avoid the inadvertent spread of virulent pathogens when conserving vulnerable mussel populations. While targeted at freshwater conservationists, this perspective has relevance for considering translocation‐mediated disease and parasite spread in any study system. [ABSTRACT FROM AUTHOR]

Unprecedented rates of introduction and spread of non-native species pose burgeoning challenges to biodiversity, natural resource management, regional economies, and human health. Current biosecurity efforts are failing to keep pace with globalization, revealing critical gaps in our understanding and response to invasions. Here, we identify four priority areas to advance invasion science in the face of rapid global environmental change. First, invasion science should strive to develop a more comprehensive framework for predicting how the behavior, abundance, and interspecific interactions of non-native species vary in relation to conditions in receiving environments and how these factors govern the ecological impacts of invasion. A second priority is to understand the potential synergistic effects of multiple co-occurring stressors— particularly involving climate change—on the establishment and impact of non-native species. Climate adaptation and mitigation strategies will need to consider the possible consequences of promoting non-native species, and appropriate management responses to non-native species will need to be developed. The third priority is to address the taxonomic impediment. The ability to detect and evaluate invasion risks is compromised by a growing deficit in taxonomic expertise, which cannot be adequately compensated by new molecular technologies alone. Management of biosecurity risks will become increasingly challenging unless academia, industry, and governments train and employ new personnel in taxonomy and systematics. Fourth, we recommend that internationally cooperative biosecurity strategies consider the bridgehead effects of global dispersal networks, in which organisms tend to invade new regions from locations where they have already established. Cooperation among countries to eradicate or control species established in bridgehead regions should yield greater benefit than independent attempts by individual countries to exclude these species from arriving and establishing. [ABSTRACT FROM AUTHOR]

The global bivalve shellfish industry makes up 25% of aquaculture, is worth USD $17.2 billion year−1, and relies upon a supply of juvenile bivalves produced by adult broodstock in hatcheries. Today large quantities of live algae are grown to feed broodstock at $220 kg−1, driving highly unsustainable energy and resource use. New advances in algal and microencapsulation technology provide solutions. We developed microencapsulated Schizochytrium algae diets, which can be produced sustainably at < $2 kg−1 from organic side-streams, and are shelf-stable to minimise waste. Physiological, histological, and cutting-edge metabolomic analyses demonstrate that in commercial settings sustainable microencapsulated diets facilitate improved sexual development and 12 × greater omega-3 levels in oysters relative to conventional live algal diets. Every tonne bivalve protein produced instead of fish spares 9 ha, 67 tonnes CO2, and 40,000 L freshwater. Further research into microencapsulated diets could support bivalve industry expansion, and contribute towards a step-change in sustainable global food production through improved aquaculture practices. [ABSTRACT FROM AUTHOR]

Profound changes to the species configuration of ecosystems globally during the 19th to 21st centuries, resulting from the introduction of neobiota, have produced a distinctive palaeontological signature in sedimentary deposits, here exemplified by those of the River Thames. Coring near Teddington Lock (ca. 4.3 m above sea level, ca. 89 km upstream from the mouth of the Thames estuary) yielded dense assemblages of shells of the invasive Asian clam Corbicula fluminea (recently invaded in 2004) and the zebra mussel Dreissena polymorpha (invaded 1824), which together accounted for 96% of individuals sampled. Population densities of C. fluminea of over 6000 individuals per m2 were maintained for a depth of 1 m indicating that the Asian clam is an important biostratigraphical marker in the Thames for sedimentary deposits accumulating since 2004. The first modern European occurrence of C. fluminea was in Portugal in 1980. In 1987, the first occurrence of C. fluminea on the northern coast of South America was observed in the Caripe River, Venezuela. The non‐native range of D. polymorpha was restricted to continental Europe for over 200 years until it appeared in the Great Lakes, USA, in 1986 having been transported in ballast water. Within three years, it reached populations of over 750,000 individuals per m2 and it is presently recorded in 35 states. Therefore, the pan‐Atlantic range expansion of D. polymorpha, coupled with the recent invasion history of C. fluminea in Venezuela and Portugal, identifies a biostratigraphical interval in sedimentary deposits forming from the early 1980s that can be correlated between Europe and the Americas. [ABSTRACT FROM AUTHOR]

Since their introduction to North America in the 1980s, research to develop effective control tools for invasive mussels (Dreissena polymorpha and D. rostriformis bugensis) has been ongoing across various research institutions using a range of testing methods. Inconsistencies in experimental methods and reporting present challenges for comparing data, repeating experiments, and applying results. The Invasive Mussel Collaborative established the Toxicity Testing Work Group (TTWG) in 2019 to identify "best practices" and guide development of a standard framework for dreissenid mussel toxicity testing protocols. We reviewed the literature related to laboratory‐based dreissenid mussel toxicity tests and determined the degree to which standard guidelines have been used and their applicability to dreissenid mussel testing. We extracted detailed methodology from 99 studies from the peer‐reviewed and gray literature and conducted a separate analysis for studies using presettlement and postsettlement mussels. We identified specific components of methods and approaches that could be refined or standardized for dreissenid mussels. These components included species identification, collection methods, size/age class distinction, maintenance practices, testing criteria, sample size, response measures, reporting parameters, exposure methods, and mortality criteria. We consulted experts in the field of aquatic toxicology and dreissenid mussel biology on our proposed. The final recommendations contained in the present review are based on published standard guidelines, methods reported in the published and gray literature, and the expertise of TTWG members and an external panel. In addition, our review identifies research needs for dreissenid mussel testing including improved methods for early–life stage testing, comparative data on life stages and between dreissenid mussel species, inclusion of a reference toxicant, and additional testing of nontarget species (i.e., other aquatic organisms). Environ Toxicol Chem 2023;42:1649–1666. © 2023 His Majesty the King in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]