Search

\nHighlightsOcean warming is driving poleward range shifts for many marine species. For foundation organisms that underpin the wider ecosystem, such as canopy-forming seaweeds, shifts in distributions or population demography can have widespread ecological consequences. The warm water kelp, Laminaria ochroleuca, is found towards its leading edge in Plymouth Sound (southwest England, UK), where it has proliferated in recent years, partially replacing the cool-water congeneric species, L. hyperborea, at some wave-sheltered locations. To determine how ecosystem dynamics have changed due to this substitution and to benchmark population structure, monthly surveys were conducted of L. ochroleuca populations at three sites over 10 months. Canopy-forming L. ochroleuca sporophytes were recorded in all months at all sites, in densities of up to ~8 individuals m‒2, indicating that this species is now a conspicuous space occupier within this ecosystem. Blade length, weight and fertility followed clear seasonal patterns peaking during late spring/early summer and rapidly declining in autumn/winter. Between-site variability was also observed, with greater densities, blade lengths/widths and standing stock biomass at the most wave-sheltered but tidally influenced site. The most abundant herbivore associated with L. ochroleuca was the blue rayed limpet, Patella pellucida, which was predominantly found in summer months and in greater abundance than reported values for other kelps in the region. Our survey wide estimates of carbon standing stock ranged from 408 ± 67 to 1006 ± 181 g C m‒2 across sites, with a regional mean of 615 g C m‒2, which was in line with previous estimates for the congeneric L. hyperborea at nearby sites. Overall, the most detailed demographic assessment of L. ochroleuca to date is provided, which allows for a greater understanding of its ecological role within the wider temperate ecosystem and serves as a robust baseline against which to detect future ecological changes. Kelp population demography at the leading range edge was highly variable.There was pronounced seasonality and site-level variation in demography.The warm-adapted Laminaira ochroleuca is now an abundant and conspicuous habitat-former.Kelp population demography at the leading range edge was highly variable.There was pronounced seasonality and site-level variation in demography.The warm-adapted Laminaira ochroleuca is now an abundant and conspicuous habitat-former. [ABSTRACT FROM AUTHOR]

Climate-driven species range expansions are underway with more tropically affiliated species, including Scleractinian corals, becoming increasingly abundant at higher latitudes. However, uncertainty remains on how these range shifts will affect reef-scale ecosystem processes, which will ultimately depend on the traits of the taxa that dominate these assemblages. Here, we quantified spatiotemporal patterns in the taxonomic and trait structure of coral assemblages along the subtropical-temperate coast of Western Australia (27°–34°S). Coral abundance was generally low and coral cover < 5% across our study sites. Coral assemblages shared similarities in morphological trait structures across the latitudinal gradient, mostly characterised by taxa with simple morphologies; yet subtle differences were also observed across latitudes, with high-latitude corals characterised by slower growth rates and reduced maximum colony sizes. We found a 3.4-fold increase (from 1 to 3.4 individuals m−2) in coral abundance at one heavily disturbed location, where canopy-forming seaweeds were replaced by turfing algae, a pattern that was partly driven by an increase in the relative contribution of warm affinity taxa, such as Acropora spp. We predicted these changes would be reflected in different components of functional diversity; yet, despite a localised signal of tropicalisation, we only observed subtle changes in the functional identity, richness, evenness, and divergence. The spatially invariant trait structure of coral assemblages suggests that the nature of ecosystem functions will likely remain unchanged during early stages of tropicalisation, and hence their contribution to temperate reef-scale ecological processes will depend on dominance over other benthic foundational species. [ABSTRACT FROM AUTHOR]

The effects of hunting on predator-avoidance behaviour are increasingly being recognised on land but have received less attention in marine systems. We examined whether predator-avoidance behaviour of temperate reef fishes differed between areas protected and not protected from recreational fishing by examining the flight-initiation distance (FID; the distance a predator can approach before the prey animal flees) of six common species in southeastern Australia. By testing species that ranged in desirability to recreational fishers, we could determine if behavioural differences were specific to target species or extended more broadly throughout the assemblage. After accounting for potential variability among sites within protection levels, we found that the FID of all species was higher in fished areas than protected areas, with FID up to 2.4 times higher in fished areas. The two commonly targeted species had the greatest FID response to fishing. FID also increased with body size for all but one species. Our findings indicate the potential for assemblage-wide effects of fishing on predator-avoidance behaviour and are consistent with an indirect mechanism of behavioural modification. [ABSTRACT FROM AUTHOR]

Kelp species function as foundation organisms in coastal marine ecosystems, where they alter environmental conditions and promote local biodiversity by providing complex biogenic habitat for an array of associated organisms. The structure and functioning of kelp forest ecosystems in some regions, such as along the Peruvian coastline, remain critically understudied. We quantified the structure and diversity of faunal assemblages within both holdfast and understory reef habitats within Eisenia cokeri forests. We sampled both habitat types within four subtidal kelp forests on multiple occasions between 2016 and 2020, and quantified fauna at a fine taxonomic level (mostly species). We recorded a total of ~ 55,000 individuals representing 183 taxa across the study, with holdfast assemblages typically exhibiting higher richness, abundance and biomass values compared with understory reef-associated assemblages. Holdfast assemblages were structurally and functionally dissimilar to those on reef surfaces and were less variable and consistent across sites and sampling events. Even so, assemblages associated with both habitat types varied significantly between sites and sampling events, with variation in upwelling strength, ocean currents, and grazing pressure among potential drivers of this ecological variability. Overall, E. cokeri supports diverse and abundant holdfast assemblages and functions as a foundation organism in Peru. Given that no other habitat-forming kelp species persist at the low latitudes of E. cokeri in mid-to-north Peru, the lack of functional redundancy suggests that effective management and conservation of this species is vital for wider ecosystem processes and biodiversity maintenance. [ABSTRACT FROM AUTHOR]

Introduction: Biogenic volatile organic compounds (BVOCs) are emitted by all organisms as intermediate or end-products of metabolic processes. Individual BVOCs perform important physiological, ecological and climatic functions, and collectively constitute the volatilome—which can be reflective of organism taxonomy and health. Although BVOC emissions of tropical benthic reef taxa have recently been the focus of multiple studies, emissions derived from their temperate counterparts have never been characterised. Objectives: Characterise the volatilomes of key competitors for benthic space among Australian temperate reefs. Methods: Six fragments/fronds of a temperate coral (Plesiastrea versipora) and a macroalga (Ecklonia radiata) from a Sydney reef site were placed within modified incubation chambers filled with seawater. Organism-produced BVOCs were captured on thermal desorption tubes using a purge-and-trap methodology, and were then analysed using GC × GC − TOFMS and multivariate tests. Results: Analysis detected 55 and 63 BVOCs from P. versipora and E. radiata respectively, with 30 of these common between species. Each taxon was characterised by a similar relative composition of chemical classes within their volatilomes. However, 14 and 10 volatiles were distinctly emitted by either E. radiata or P. versipora respectively, including the halogenated compounds iodomethane, tribromomethane, carbon tetrachloride and trichloromonofluoromethane. While macroalgal cover was 3.7 times greater than coral cover at the sampling site, P. versipora produced on average 17 times more BVOCs per cm2 of live tissue, resulting in an estimated contribution to local BVOC emission that was 4.7 times higher than E. radiata. Conclusion: Shifts in benthic community composition could disproportionately impact local marine chemistry and affect how ecosystems contribute to broader BVOC emissions. [ABSTRACT FROM AUTHOR]

Despite 22% of the world's coastal regions experiencing some degree of light pollution, and biologically important artificial light at night (ALAN) reaching large portions of the seafloor (greater than 75%) near coastal developments, the impacts of ALAN on temperate and tropical reefs are still relatively unknown. Because many reef species have evolved in response to low-light nocturnal environments, consistent daily, lunar, and seasonal light cycles, and distinct light spectra, these impacts are likely to be profound. Recent studies have found ALAN can decrease reproductive success of fishes, alter predation rates of invertebrates and fishes, and impact the physiology and biochemistry of reef-building corals. In this paper, we integrate knowledge of the role of natural light in temperate and tropical reefs with a synthesis of the current literature on the impacts of ALAN on reef organisms to explore potential changes at the system level in reef communities exposed to ALAN. Specifically, we identify the direct impacts of ALAN on individual organisms and flow on effects for reef communities, and present potential scenarios where ALAN could significantly alter system-level dynamics, possibly even creating novel ecosystems. Lastly, we highlight large knowledge gaps in our understanding of the overall impact of ALAN on reef systems. This article is part of the theme issue 'Light pollution in complex ecological systems'. [ABSTRACT FROM AUTHOR]

The northern Adriatic Sea (NAS) hosts numerous biogenic subtidal reefs that are considered biodiversity hotspots. Several studies have already investigated the origin and biodiversity of these reefs. However, many of them are still unexplored and further knowledge is needed for their conservation. Here, the spatial variability, epibenthic community structure, and environmental features that characterize these habitats were investigated. Fifteen randomly selected reefs were sampled between 2013 and 2017, including some remote sites that have never been studied before. A fuzzy k-means clustering method and redundancy analysis were used to find similarities among sites in terms of epibenthic assemblages and to model relationships with abiotic variables. The results showed that these reefs are highly heterogeneous in terms of species composition and geomorphological features. The results were also consistent with previous studies and highlighted three main types of benthic assemblages defined by the dominance of different organisms, mainly reflecting the coastal-offshore gradient: nearshore reefs, generally dominated by stress-tolerant species; reefs at a middle distance from the coast, characterized by sponges, non-calcareous encrusting algae and ascidians; offshore reefs, dominated by reef builders. However, distance from the coast was not the only factor affecting species distribution, as other local factors and environmental characteristics also played a role. This kind of biogenic reefs in temperate seas are still poorly known. The present work contributed to shed further light on these habitats, by complementing the results of previous studies on their natural diversity, highlighting the specificity of the epibenthic communities of NAS reefs and the need to improve current, still inadequate, conservation measures. [ABSTRACT FROM AUTHOR]

Intensive and regular fishing occurs in the marine area of the natural park “Parque Natural do Sudoeste Alentejano e Costa Vicentina” (PNSACV; SW coast of continental Portugal). In 2011, this area became a marine park with different protection levels (total, partial, and complementary). We assessed in 2011 and 2012 if partial protection (PP) in Marine Protected Areas (MPAs) changed the taxa richness, abundance, size, and community composition of cryptic and non-cryptic fishes. We also determined if these effects were observed outside PP areas in adjacent control areas. Underwater visual censuses (UVC) of cryptic and non-cryptic fish species were conducted in rocky subtidal habitats (~10 m deep) with band transects (25 × 2 m and 25 × 4 m, respectively) to determine abundance and size classes. The northern half of the PNSACV was sampled at a scale of tens (site—two sites per area; 4–6 transects per site) and hundreds (area) of meters. Two PP and six control areas were sampled. The homogeneity and abundance of bottom habitat types were assessed at each site. Effects of protection were not detected in the community structure or univariate analyses (i.e., taxa richness and total abundance) of non-cryptic and cryptic fishes. The early phase of the MPAs may have driven the lack of significant protection effects. Replication in time within a monitoring program is recommended to assess these conservation measures’ ecological effects.

Coastal habitats are increasingly recognized as fundamentally important components of global carbon cycles, but the rates of carbon flow associated with marine macrophytes are not well resolved for many species in many regions. We quantified density, rates of primary productivity, and detritus production of intertidal stands of two common intertidal kelp species—Laminaria digitata (oarweed) and Saccharina latissima (sugar kelp)—on four NE Atlantic rocky shores over 22 months. The density of L. digitata was greater at exposed compared to moderately exposed shores but remained consistently low for S. latissima throughout the survey period. Individual productivity and erosion rates of L. digitata did not differ between exposed and moderately exposed shores but differed across exposure levels throughout the year at moderately exposed sites only. Productivity and erosion of S. latissima remained low on moderately exposed shores and showed no clear seasonal pattern. Patterns of productivity and total detrital production (erosion and dislodgement) per m2 of both L. digitata and S. latissima followed closely that of densities per m2, peaking in May during both survey years. Temperature and light were key factors affecting the productivity rates of L. digitata and S. latissima. Erosion rates of L. digitata were affected by wave exposure, temperature, light, grazing, and epiphyte cover, but only temperature‐affected erosion of S. latissima. Production of biomass and detritus was greater in L. digitata than in S. latissima and exceeded previous estimates for subtidal and warmer‐water affinity kelp populations (e.g., Laminaria ochroleuca). These biogenic habitats are clearly important contributors to the coastal carbon cycle that have been overlooked previously and should be included in future ecosystem models. Further work is required to determine the areal extent of kelp stands in intertidal and shallow subtidal habitats, which is needed to scale up local production estimates to entire coastlines. [ABSTRACT FROM AUTHOR]

Intensive and regular fishing occurs in the marine area of the natural park "Parque Natural do Sudoeste Alentejano e Costa Vicentina" (PNSACV; SW coast of continental Portugal). In 2011, this area became a marine park with different protection levels (total, partial, and complementary). We assessed in 2011 and 2012 if partial protection (PP) in Marine Protected Areas (MPAs) changed the taxa richness, abundance, size, and community composition of cryptic and non-cryptic fishes. We also determined if these effects were observed outside PP areas in adjacent control areas. Underwater visual censuses (UVC) of cryptic and non-cryptic fish species were conducted in rocky subtidal habitats (~10 m deep) with band transects (25 × 2 m and 25 × 4 m, respectively) to determine abundance and size classes. The northern half of the PNSACV was sampled at a scale of tens (site—two sites per area; 4–6 transects per site) and hundreds (area) of meters. Two PP and six control areas were sampled. The homogeneity and abundance of bottom habitat types were assessed at each site. Effects of protection were not detected in the community structure or univariate analyses (i.e., taxa richness and total abundance) of non-cryptic and cryptic fishes. The early phase of the MPAs may have driven the lack of significant protection effects. Replication in time within a monitoring program is recommended to assess these conservation measures' ecological effects. [ABSTRACT FROM AUTHOR]

Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change. [ABSTRACT FROM AUTHOR]

Climate change can alter ecological communities both directly, by driving shifts in species distributions and abundances, and indirectly by influencing the strength and direction of species interactions. Within benthic marine ecosystems, foundation species such as canopy‐forming macro‐algae often underpin important cascades of facilitative interactions.We examined the wider impacts of climate‐driven shifts in the relative abundances of foundation species within a temperate reef system, with particular focus on a habitat cascade whereby kelp facilitate epiphytic algae that, in turn, facilitate mobile invertebrates. Specifically, we tested whether the warm‐water kelp Laminaria ochroleuca, which has proliferated in response to recent warming trends, facilitated a secondary habitat‐former (epiphytic algae on stipes) and associated mobile invertebrates, to the same degree as the cold‐water kelp Laminaria hyperborea.The facilitative interaction between kelp and stipe‐associated epiphytic algae was dramatically weaker for the warm‐water foundation species, leading to breakdown of a habitat cascade and impoverished associated faunal assemblages. On average, the warm‐water kelp supported >250 times less epiphytic algae (by biomass) and >50 times fewer mobile invertebrates (by abundance) than the cold‐water kelp. Moreover, by comparing regions of pre‐ and post‐range expansion by L. ochroleuca, we found that warming‐impacted kelp forests supported around half the biomass of epiphytic algae and one‐fifth of the abundance of mobile invertebrates, per unit area, compared with unimpacted forests. We suggest that disruption to this facilitation cascade has the potential to impact upon higher trophic levels, specifically kelp forest fishes, through lower prey availability.Synthesis. Climate‐driven shifts in species' distributions and the relative abundances of foundation organisms will restructure communities and alter ecological interactions, with consequences for ecosystem functioning. We show that climate‐driven substitutions of seemingly similar foundation species can alter local biodiversity and trophic processes in temperate marine ecosystems. [ABSTRACT FROM AUTHOR]

Collin, A.; James, D.; Gairin, E.; Aubert, M.; Daniel, Y.; Feunteun, E., and Dubois, S., 2024. The spatial network of the largest honeycomb reef in the world as revealed by an ultra-high resolution lidar drone. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 961-965. Charlotte (North Carolina), ISSN 0749-0208. On temperate coastal areas, Sabellaria alveolata worms are honeycomb reef-builders, providing multiple ecosystem services. The largest honeycomb reef in the world is located in the Bay of Mont-Saint-Michel (France) and has never been surveyed in its entirety at ultra-high spatial resolution. This original research addresses this gap by using a medium-cost drone topographic lidar system over the time window of a low spring tide. A denoised lidar point cloud, composed of 702 million illuminations (on average, 118 points/m2), enabled to compute point-scaled height above the ground at an accuracy of 0.06 m. The 3033 reef patches of height ≥ 0.5 m allowed to draw a graph-based network, woven with 3032 edges. The contribution of each node and edge was estimated and mapped using Betweenness Centrality, a local weighted connectivity metric. The nodes of the central and seaward front sub-reefs primarily contributed to the network's anchoring, while the edges linking the easternmost and westernmost sub-reefs were crucial to ensure full connectivity. The use of ultra-high spatial resolution, at very high temporal resolution, paves the way to seasonally monitor the world's largest honeycomb reef in order to outline areas subjected to erosion, and rapidly manage threats upon that ecosystem. [ABSTRACT FROM AUTHOR]

Aim: Temperate marine systems globally are warming at accelerating rates, facilitating the poleward movement of warm‐water species, which are tropicalizing higher‐latitude reefs. While temperature plays a key role in structuring species distributions, less is known about how species' early life stages are responding to warming‐induced changes in preferred nursery habitat availability. We aim to identify key ecological and environmental drivers of juvenile reef fishes' distributions in the context of ocean warming. Location: South‐eastern Australian coastline from 30 to 37°S. Methods: We used a decade of underwater visual census data to uncover latitudinal distribution patterns of juvenile reef fishes and habitats across 1000 km of coastline, from subtropical to temperate latitudes. We modelled how benthic habitat cover, depth, wave exposure and sea surface temperature influence distributions of warm‐water and cool‐water juvenile reef fishes on temperate rocky reefs. Results: We found sea surface temperature was typically the most important factor influencing densities of juvenile fishes, regardless of species' thermal affinity or latitudinal range extent. Juveniles of tropical and subtropical range‐expanding fishes responded more strongly to warmer temperatures and lower wave exposure, while juveniles of temperate species responded more strongly to benthic habitats. Species' responses to greater availability of temperate reef habitat‐formers such as kelp and other macroalgae contrasted, being positive for temperate and negative for tropical and subtropical juvenile fishes. Main conclusions: The availability of both suitable habitat and sea temperatures for species' early life stages is important considerations when predicting changes in reef fishes' distributions in the context of ocean warming. Warming‐induced isotherm shifts and feedback loops constraining the persistence of key temperate reef habitat‐formers will favour range‐expanding tropical reef fishes colonizing higher‐latitude reefs, while disadvantaging some macroalgal‐associated resident temperate species. Such varying responses to warming‐induced environmental changes may strongly influence the structure of emerging tropicalized reef assemblages. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs), discrete periods of extreme warm water temperatures superimposed onto persistent ocean warming, have increased in frequency and significantly disrupted marine ecosystems. While field observations on the ecological consequences of MHWs are growing, a mechanistic understanding of their direct effects is rare. We conducted an outdoor tank experiment testing how different thermal stressor profiles impacted the ecophysiological performance of three dominant forest‐forming seaweeds. Four thermal scenarios were tested: contemporary summer temperature (22°C), low persistent warming (24°C), a discrete MHW (22–27°C), and temperature variability followed by a MHW (22–24°C, 22–27°C). The physiological performance of seaweeds was strongly related to thermal profile and varied among species, with the highest temperature not always having the strongest effect. MHWs were highly detrimental for the fucoid Phyllospora comosa, whereas the laminarian kelp Ecklonia radiata showed sensitivity to extended thermal stress and demonstrated a cumulative temperature threshold. The fucoid Sargassum linearifolium showed resilience, albeit with signs of decline with bleached and degraded fronds, under all conditions, with stronger decline under stable control and warming conditions. The varying responses of these three co‐occurring forest‐forming seaweeds under different temperature scenarios suggests that the impact of ocean warming on near shore ecosystems may be complex and will depend on the specific thermal profile of rising water temperatures relative to the vulnerability of different species. [ABSTRACT FROM AUTHOR]

Understanding the resilience of temperate reefs to climate change requires exploring the recovery capacity of their habitat-forming species from recurrent marine heatwaves (MHWs). Here, we show that, in a Mediterranean highly enforced marine protected area established more than 40 years ago, habitat-forming octocoral populations that were first affected by a severe MHW in 2003 have not recovered after 15 years. Contrarily, they have followed collapse trajectories that have brought them to the brink of local ecological extinction. Since 2003, impacted populations of the red gorgonian Paramuricea clavata (Risso, 1826) and the red coral Corallium rubrum (Linnaeus, 1758) have followed different trends in terms of size structure, but a similar progressive reduction in density and biomass. Concurrently, recurrent MHWs were observed in the area during the 2003–2018 study period, which may have hindered populations recovery. The studied octocorals play a unique habitat-forming role in the coralligenous assemblages (i.e. reefs endemic to the Mediterranean Sea home to approximately 10% of its species). Therefore, our results underpin the great risk that recurrent MHWs pose for the long-term integrity and functioning of these emblematic temperate reefs. [ABSTRACT FROM AUTHOR]

Poleward range extensions of coral reef species can reshuffle temperate communities by generating competitive interactions that did not exist previously. However, novel environmental conditions and locally adapted native temperate species may slow tropical invasions by reducing the ability of invaders to access local resources (e.g. food and shelter). We test this hypothesis on wild marine fish in a climate warming hotspot using a field experiment encompassing artificial prey release. We evaluated seven behaviours associated with foraging and aggressive interactions in a common range-extending coral reef fish (Abudefduf vaigiensis) and a co-shoaling temperate fish (Microcanthus strigatus) along a latitudinal temperature gradient (730 km) in SE Australia. We found that the coral reef fish had reduced foraging performance (i.e. slower prey perception, slower prey inspection, decreased prey intake, increased distance to prey) in their novel temperate range than in their subtropical range. Furthermore, higher abundance of temperate fishes was associated with increased retreat behaviour by coral reef fish (i.e. withdrawal from foraging on released prey), independent of latitude. Where their ranges overlapped, temperate fish showed higher foraging and aggression than coral reef fish. Our findings suggest that lower foraging performance of tropical fish at their leading range edge is driven by the combined effect of environmental factors (e.g. lower seawater temperature and/or unfamiliarity with novel conditions in their extended temperate ranges) and biological factors (e.g. increased abundance and larger body sizes of local temperate fishes). Whilst a future increase in ocean warming is expected to alleviate current foraging limitations in coral reef fishes at leading range edges, under current warming native temperate fishes at their trailing edges appear able to slow the range extension of coral reef fishes into temperate ecosystems by limiting their access to resources. [ABSTRACT FROM AUTHOR]

Ecological interactions are found across ecosystems, facilitating comparison among systems with distinct species composition. The balance of positive and agonistic interactions among species may be sensitive to variation in the diversity and abundance of species in a community. We studied marine interaction networks among reef fishes on two oceanic islands characterized by high rates of endemism and restricted population connectivity: Rapa Nui (Easter Island) and Robinson Crusoe Island (Juan Fernandez Archipelago). Specifically, we examined whether the type and strength of behavioral interactions varied between these two isolated fish assemblages, how the relative proportions of agonistic and positive interactions compare, and which are the most important interacting species in each system. Combining detailed interaction records using standardized remote underwater video and visual censuses, we observed: (a) Rapa Nui contains 50% more fish species but half the fish densities than Robinson Crusoe, (b) despite these differences, the total number of interactions and proportion of all potentially interacting species were similar between the two oceanic islands; (c) the species that occupied the greatest proportion of all potential interactions in each community were endemic to their respective islands; (d) the relative frequency of positive and agonistic interactions varied, with more agonistic interactions in the more speciose reef system (Rapa Nui) and more positive interactions where fish densities were higher (Robinson Crusoe); and lastly (e) the relative abundance of each species predicted the interaction strength and the number of interactions across all reef fish species. It is of particular importance to understand the role of endemic species and processes affecting reef fish ecological networks on oceanic islands given the multiple anthropogenic threats to these isolated and vulnerable ecosystems. [ABSTRACT FROM AUTHOR]

We examined spatiotemporal variability in the structure of faunal assemblages associated with the warm-temperate pseudo-kelp Saccorhiza polyschides towards its range centre (Western English Channel, southwest UK), to better understand its role as a habitat-former in the northeast Atlantic. A total of 180 sporophytes and their associated fauna were sampled across three months, three sites, and two depths. Assemblage abundance and biomass varied markedly between three morpho-functional sporophyte components (i.e., holdfast, stipe, blade). We recorded rich and abundant macroinvertebrate assemblages, comprising nine phyla, 28 coarse taxonomic groups, and 57 species of molluscs, which consistently dominated assemblages. We observed pronounced seasonality in faunal assemblage structure, marked variability between sites and depths, and strong positive relationships between biogenic habitat availability and faunal abundance/biomass. S. polyschides sporophytes are short-lived and offer temporary, less-stable habitat compared with dominant perennial Laminaria species, so shifts in the relative abundances of habitat-formers will likely alter local biodiversity patterns. [Display omitted] • Saccorhiza polyschides is a widespread but understudied pseudo-kelp. • Molluscs, arthropods and annelids dominated faunal communities. • Faunal assemblages and abundances exhibited strong seasonality and some spatial variation. • S. polyschides plays a crucial role as a habitat-forming foundation species. • Study provides a robust baseline against which to detect future ecological changes and community shifts. [ABSTRACT FROM AUTHOR]

Global warming is facilitating the range expansion of tropical herbivores, causing a tropicalization of temperate marine ecosystems, where tropical herbivores can suppress habitat‐forming macrophytes, supporting the resilience of canopy‐free ecosystem states. However, currently we lack a thorough understanding of the mechanisms that, on one hand, support the persistence of tropical herbivores and on the other support the recovery of temperate foundation species in tropicalized ecosystems, a required knowledge to predict potential regime shifts and reversals to the baseline state of the ecosystem.This study tested processes behind the persistence of the tropicalization of temperate reefs which experienced a complete loss of their kelp forests and an influx of tropical herbivores following a marine heatwave in 2011. For this, we assessed the feedback mechanisms that maintain turf‐dominated states (recruitment of tropical herbivores, browsing and grazing rates and turf cover) and those that resist it (kelp recruitment, survival and reproductiveness).We found that the reefs remained tropicalized with high abundances of turf and tropical herbivores after 9 years from the regime shift. The rabbitfish Siganus fuscescens and the chub Kyphosus bigibbus were the most important herbivores whose persistence was supported by the adjacent reef lagoon, where seagrass meadows and the backreef habitats hosted juveniles of both species, particularly rabbitfish. Tropical herbivores exerted a strong top–down control on turf seaweed and kelp during herbivory assays, rapidly consuming kelp individuals in open areas. However, in topographical refuges in the reefs, herbivory was low and kelp individuals survived, with some having reproductive tissue.Synthesis. Our findings incorporate the importance of nursery grounds for tropical herbivores and herbivory refugia for kelp individuals into the tropicalization model, where the former increases the resilience of canopy‐free states and the latter might facilitate recovering kelp populations. The restoration of abundant warm‐resistant kelp populations in shelters could provide local sources of propagules to recolonize open spaces; however, our results suggest that the reduction of herbivory and the provision of turf‐free substratum would be necessary to boost the recovery of kelp forests. [ABSTRACT FROM AUTHOR]

Abstract Worldwide, several countries have established coherent, representative, and large‐scale networks of marine reserves to conserve biodiversity. Very few have, however, published systematic assessments of the ecological responses to this network protection, hindering broad understanding of their generality, utility, and efficacy. We present data collected from systematic sampling of rocky reef fish assemblages at sites across a network of 27 no‐take marine reserve areas (NTMR) and 27 partially protected areas (PPA) nested within multiple marine parks (regional networks) across three Australian bioregions spanning >1000 km of coastline (7° latitude) to test the generality of ecological change across this network. We also sampled 18 reference areas (outside of the marine parks) to provide an independent assessment of potential NTMR effects and also to assess whole marine park effects. Baited remote underwater video (BRUV) was used to sample fishes between depths of 20–40 m over austral winters in four years (2010, 2011, 2015, and 2016). Despite substantial bioregional differences in fish assemblages, large and consistent effects of NTMR protection were detected across all bioregions for a key commercially and recreationally harvested species, Chrysophrys auratus (pink snapper). There were substantial increases in relative abundance of C. auratus in NTMR compared with fished zones through time (effect sizes >150%). The wider assemblage of targeted fish (excluding C. auratus) only showed relatively small effects of protection (~11%) with trends observed for site‐attached wrasses (labrids) and planktivores (e.g., commercially fished Scorpis lineolata) that are recreationally and commercially harvested. Furthermore, the relative abundance of non‐target or by‐catch species generally did not differ among management zones across the bioregional network. These results highlight how NTMR can be used to assess the ecological effects of fishing and wider environmental management, and can be incorporated into ecosystem‐based management for reef species more generally. Importantly, the provision of robust evidence of the performance and generality of NTMR over large‐spatial scales (e.g., bioregions) provides greater confidence in the expected outcomes from marine reserve networks as a conservation management approach.

Citizen science (CS) projects may provide community-based ecosystem monitoring, expanding our ability to collect data across space and time. However, the data from CS are often not effectively integrated into institutional monitoring programs and decision-making processes, especially in marine conservation. This limitation is partially due to difficulties in accessing the data and the lack of tools and indices for proper management at intended spatial and temporal scales. MedSens is a biotic index specifically developed to provide information on the environmental status of subtidal rocky coastal habitats, filling a gap between marine CS and coastal management in the Mediterranean Sea. The MedSens index is based on 25 selected species, incorporating their sensitivities to the pressures indicated by the European Union’s Marine Strategy Framework Directive (MSFD) and open data on their distributions and abundances, collected by trained volunteers (scuba divers, free divers and snorkelers) using the Reef Check Mediterranean Underwater Coastal Environment Monitoring (RCMed U-CEM) protocol. The species sensitivities were assessed relative to their resistance and resilience against physical, chemical, and biological pressures, according to benchmark levels and a literature review. The MedSens index was calibrated on a dataset of 33,021 observations from 569 volunteers (2001–2019), along six countries’ coasts. A free and user-friendly QGIS plugin allows easy index calculation for areas and time frames of interest. The MedSens index was applied to Mediterranean marine protected areas (MPAs) and the management and monitoring zones within Italian MPAs. In the studied cases, the MedSens index responds well to the local pressures documented by previous investigations.MedSens converts the data collected by trained volunteers into an effective monitoring tool for the Mediterranean subtidal rocky coastal habitats. MedSens can help conservationists and decision-makers identify the main pressures acting in these habitats, as required by the MSFD, supporting them in the implementation of appropriate marine biodiversity conservation measures and better communicate the results of their actions. By directly involving stakeholders, this approach increases public awareness and the acceptability of management decisions, enabling more participatory conservation tactics.

Worldwide, several countries have established coherent, representative, and large‐scale networks of marine reserves to conserve biodiversity. Very few have, however, published systematic assessments of the ecological responses to this network protection, hindering broad understanding of their generality, utility, and efficacy. We present data collected from systematic sampling of rocky reef fish assemblages at sites across a network of 27 no‐take marine reserve areas (NTMR) and 27 partially protected areas (PPA) nested within multiple marine parks (regional networks) across three Australian bioregions spanning >1000 km of coastline (7° latitude) to test the generality of ecological change across this network. We also sampled 18 reference areas (outside of the marine parks) to provide an independent assessment of potential NTMR effects and also to assess whole marine park effects. Baited remote underwater video (BRUV) was used to sample fishes between depths of 20–40 m over austral winters in four years (2010, 2011, 2015, and 2016). Despite substantial bioregional differences in fish assemblages, large and consistent effects of NTMR protection were detected across all bioregions for a key commercially and recreationally harvested species, Chrysophrys auratus (pink snapper). There were substantial increases in relative abundance of C. auratus in NTMR compared with fished zones through time (effect sizes >150%). The wider assemblage of targeted fish (excluding C. auratus) only showed relatively small effects of protection (~11%) with trends observed for site‐attached wrasses (labrids) and planktivores (e.g., commercially fished Scorpis lineolata) that are recreationally and commercially harvested. Furthermore, the relative abundance of non‐target or by‐catch species generally did not differ among management zones across the bioregional network. These results highlight how NTMR can be used to assess the ecological effects of fishing and wider environmental management, and can be incorporated into ecosystem‐based management for reef species more generally. Importantly, the provision of robust evidence of the performance and generality of NTMR over large‐spatial scales (e.g., bioregions) provides greater confidence in the expected outcomes from marine reserve networks as a conservation management approach. [ABSTRACT FROM AUTHOR]

Many temperate reefs are experiencing a shift towards a greater abundance of tropical species in response to marine heatwaves and long-term ocean warming worldwide. Baseline data for coral communities growing in high-latitude reefs is required to better understand ecosystem changes over time. In this study, we explore spatial and temporal trends in the distribution of coral communities from 1999 to 2019 at 118 reef sites within the five marine parks located in the south-west of Western Australia (WA) between 30° to 35° S. Our estimates of coral cover were generally low (Turbinaria spp. at Marmion Marine Park and Ngari Capes Marine Park, and Pocillopora spp. and Dipsastraea spp. at Rottnest Island and Jurien Bay. Our findings suggest that conditions in south-west WA are favorable to the ongoing survival of existing genera and there were minimal signs of expansion in coral cover at most study sites. Coral cover and composition on these reefs may, however, change with ongoing ocean warming and increased occurrence of marine heatwaves. This study provides a valuable benchmark for assessing future changes in coral assemblages and highlights the need for targeted hard-coral surveys to quantify subtle changes in high-latitude coral community assemblages.

Climate change threatens coastal benthic communities on a global scale. However, the potential effects of ongoing warming on mesophotic temperate reefs at the community level remain poorly understood. Investigating how different members of these communities will respond to the future expected environmental conditions is, therefore, key to anticipating their future trajectories and developing specific management and conservation strategies. Here, we examined the responses of some of the main components of the highly diverse Mediterranean coralligenous assemblages to thermal stress. We performed thermotolerance experiments with different temperature treatments (from 26 to 29°C) with 10 species from different phyla (three anthozoans, six sponges and one ascidian) and different structural roles. Overall, we observed species‐specific contrasting responses to warming regardless of phyla or growth form. Moreover, the responses ranged from highly resistant species to sensitive species and were mostly in agreement with previous field observations from mass mortality events (MMEs) linked to Mediterranean marine heat waves. Our results unravel the diversity of responses to warming in coralligenous outcrops and suggest the presence of potential winners and losers in the face of climate change. Finally, this study highlights the importance of accounting for species‐specific vulnerabilities and response diversity when forecasting the future trajectories of temperate benthic communities in a warming ocean. [ABSTRACT FROM AUTHOR]

Abstract Sea urchins, ecologically important herbivores of shallow subtidal temperate reefs, are considered particularly threatened in a future ocean acidification scenario, since their carbonate structures (skeleton and grazing apparatus) are made up of the very soluble high-magnesium calcite, particularly sensitive to a decrease in pH. The biomechanical properties of their skeletal structures are of great importance for their individual fitness, because the skeleton provides the means for locomotion, grazing and protection from predators. Sea urchin skeleton is composed of discrete calcite plates attached to each other at sutures by organic ligaments. The present study addressed the fate of the sea urchin Paracentrotus lividus (Lamarck, 1816) skeleton in acidified oceans, taking into account the combined effect of reduced pH and macroalgal diet, with potential cascading consequences at the ecosystem level. A breaking test on individual plates of juvenile specimens fed different macroalgal diets has been performed, teasing apart plate strength and stiffness from general robustness. Results showed no direct short-term effect of a decrease in seawater pH nor of the macroalgal diet on single plate mechanical properties. Nevertheless, results from apical plates, the ones presumably formed during the experimental period, provided an indication of a possible diet-mediated response, with sea urchins fed the more calcified macroalga sustaining higher forces before breakage than the one fed the non-calcified algae. This, on the long term, may produce bottom-up effects on sea urchins, leading to potential shifts in the ecosystem equilibrium under an ocean acidified scenario. Highlights • Biomechanical properties of sea urchin test have a great importance in their individual fitness. • Combined effect of decreased pH and macroalgal diet highlights potential cascading effects. • No direct short-term effect of decreased pH and macroalgal diet on plate mechanical properties. • Longer term exposure needed to observe substantial differences on skeletal plate structure. [ABSTRACT FROM AUTHOR]

Introduction: Biogenic volatile organic compounds (BVOCs) are emitted by all organisms as intermediate or end-products of metabolic processes. Individual BVOCs perform important physiological, ecological and climatic functions, and collectively constitute the volatilome-which can be reflective of organism taxonomy and health. Although BVOC emissions of tropical benthic reef taxa have recently been the focus of multiple studies, emissions derived from their temperate counterparts have never been characterised., Objectives: Characterise the volatilomes of key competitors for benthic space among Australian temperate reefs., Methods: Six fragments/fronds of a temperate coral (Plesiastrea versipora) and a macroalga (Ecklonia radiata) from a Sydney reef site were placed within modified incubation chambers filled with seawater. Organism-produced BVOCs were captured on thermal desorption tubes using a purge-and-trap methodology, and were then analysed using GC × GC - TOFMS and multivariate tests., Results: Analysis detected 55 and 63 BVOCs from P. versipora and E. radiata respectively, with 30 of these common between species. Each taxon was characterised by a similar relative composition of chemical classes within their volatilomes. However, 14 and 10 volatiles were distinctly emitted by either E. radiata or P. versipora respectively, including the halogenated compounds iodomethane, tribromomethane, carbon tetrachloride and trichloromonofluoromethane. While macroalgal cover was 3.7 times greater than coral cover at the sampling site, P. versipora produced on average 17 times more BVOCs per cm 2 of live tissue, resulting in an estimated contribution to local BVOC emission that was 4.7 times higher than E. radiata., Conclusion: Shifts in benthic community composition could disproportionately impact local marine chemistry and affect how ecosystems contribute to broader BVOC emissions., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Climate change is driving a redistribution of species and the reconfiguration of ecological communities at a global scale. Persistent warming in many regions has caused species to extend their geographical ranges into new habitats, with thermally tolerant species often becoming competitively dominant over species with colder affinities. Although these climate‐driven changes in species abundance and diversity are well documented, their ecosystem‐level implications are poorly understood, and resolving whether reconfigured communities can maintain fundamental ecosystem functions represents a pressing challenge in an increasingly warmer world.Here, we investigated how climate‐driven substitutions of foundation species influence processes associated with the cycling of organic matter (biomass production, detritus flow, herbivory, decomposition) by comparing two habitat‐forming kelp species with contrasting thermal affinities. We examined the wider ecosystem consequences of such shifts for the observed (and predicted) emergence of novel marine forest communities in the NE Atlantic, which are expected to become more dominated by range‐expanding, warm‐temperate kelp species.Warm‐temperate kelps both accumulated and released 80% more biomass than the cold‐temperate species despite being taxonomically closely related and morphologically similar. Furthermore, the warm‐temperate species accumulated biomass and released detritus year‐round, whereas the cold‐temperate species did so during short, discrete periods. The warm‐temperate kelps supported higher densities of invertebrate grazers and were a preferred food source. Finally, their detritus decomposed 6.5 times faster, despite supporting comparable numbers of detritivores. Overall, our results indicate an important shift in organic matter circulation along large sections of NE Atlantic coastline following the climate‐driven expansion of a warm‐affinity kelp, with novel forests supplying large amounts of temporally continuous—yet highly labile—organic matter.Synthesis. Collectively, our results show that, like species invasions, climate‐driven range expansions and consequent shifts in the identity of dominant species can modify a wide range of important ecosystem processes. However, alterations in overall ecosystem functioning may be relatively limited where foundation species share similar ecological and functional traits. Our study suggests an important shift in the cycling of organic matter along large sections of NE Atlantic coastline following the climate‐driven expansion of a warm‐affinity kelp, with novel forests supplying large amounts of temporally‐continuous—yet highly labile—organic matter. [ABSTRACT FROM AUTHOR]

Abstract Grazing is a pivotal function in many marine systems, conferring resilience to coral reefs by limiting algal overgrowth, but triggering phase shifts on temperate reefs. Thus, changes to consumption rates of grazing species in response to higher future temperatures may have broad ecological consequences. We measured how the consumption rates of a widespread mesograzer (the hermit crab Clibanarius virescens) responded to changing temperatures in the laboratory and applied these findings to model the spatial footprint on grazing animals throughout the Indo-Pacific region under climate change scenarios. We show that mean grazing capacity may increase in shallow coastal areas in the second half of the century. The effects are, however, asymmetrical, with tropical reefs predicted to experience slightly diminished grazing whilst reefs at higher latitudes will be grazed substantially more. Our findings suggest that assessments of the effects of climate change on reef ecosystems should consider how warming affects grazing performance when predicting wider ecological impacts. Graphical abstract Unlabelled Image Highlights • Warmer seas may alter species interactions and ecological functions (e.g. grazing). • We measured grazing response in the lab and modelled changes under future climates. • Grazing changes unimodally with temperature and may increase in Indo-Pacific. • Small decreases in tropics offset by big increases at higher latitudes in the future. • Similar responses in other grazers suggest possible broad effects as seas warm. [ABSTRACT FROM AUTHOR]

The introduction of a non‐native species frequently has adverse direct effects on native species. The underlying mechanisms, however, often remain unclear, in particular where native and invasive species are taxonomically similar.We found evidence of direct competitive interactions between a globally distributed invasive species (the Pacific oyster, Magallana gigas) and its native counterpart (the European oyster, Ostrea edulis). We also discovered that the competitive outcome differed between different habitat types and orientation by identifying context‐dependent responses driven by environmental conditions and stress (i.e. intertidal compared to subtidal habitats; and vertical versus horizontal substratum). This is particularly important because the European oyster is threatened, or in decline, throughout most of its range, and restoration efforts are underway in many regions.We combined experimental manipulations and stable isotope analysis (SIA) to identify the direct effects of competition and the mechanisms by which the invasive and native species compete. We identified negative effects of the invasive species on the native oyster, but these were limited to the subtidal habitat (lower stress environment) and determined by substratum orientation (habitat structure). Crucially, we found that effects of the invasive species on the native species were not always negative and under certain conditions (e.g. on vertical substrata) were positive. Shifts in isotopic niches of both species when co‐occurring, alongside mixing models, indicate that exploitative competition for food is most likely to underpin niche partitioning between both species.We have identified different foraging strategies under different contexts, and our findings highlight the importance of exploitative competition as a driving mechanism behind the co‐occurrence of two seemingly functionally similar consumers. The combination of experimental manipulations with SIA is a powerful tool, and we illustrate how this approach should be incorporated, into multiple environmental contexts at appropriate scales, to more accurately predict impacts of the spread of invasive species on native communities. Plain Language Summary [ABSTRACT FROM AUTHOR]

Competition for space between corals and macroalgae represents a key threatening process for coral reefs, yet the influence of climate change on this competitive interaction is poorly understood, particularly at the poleward margins of coral distribution. Here we describe the discovery of Australia’s southernmost hermatypic corals and explore novel dynamics facilitating the presence and extent of high-latitude coral communities. Examination of 607 shallow reef sites across temperate Australia revealed hard corals to be negatively associated with increasing kelp bed cover, but positively associated with increasing sea surface temperature, herbivorous fishes, grazing sea urchins, and increasing cover of turf algae, which proliferates in the absence of kelp. However, the nature of these effects varied across different regions of temperate Australia consistent with regional variability in the presence/absence of key functional groups for temperate reefs, such as guilds of subtropical herbivorous fishes and/or prevalence of overgrazing sea urchins. For the southernmost coral communities, in eastern Bass Strait Tasmania, the dominant reef-building coral Plesiastrea versipora was negatively associated with kelp and positively associated with the southward range-extending diadematid sea urchin Centrostephanus rodgersii, which has caused extensive kelp bed overgrazing since first locally reported in 1974. Facilitation of coral establishment was strongest on overgrazed barrens where urchin density was relatively low, but sufficient to maintain the reef kelp-free, while corals were less frequent at high urchin densities and completely absent from barrens colonised by intensively grazing limpets. In contrast to tropical Australian coral reefs and other temperate regions (e.g. Western Australia), assays of herbivory confirmed sea urchin grazing, not herbivorous fishes, as chiefly responsible for kelp consumption within this high-latitude system. Size structure of P. versipora in eastern Bass Strait was dominated by small colonies (~ 20 cm2), suggesting an expanding population at the poleward edge of the species’ range. Nevertheless, colonies up to a maximum area of 500 cm2 were observed, which are likely > 40 yrs old based on growth rates established in warmer waters. This research highlights novel patterns and processes structuring the interface between subtropical and temperate reef communities under climate change and specifically highlights the role of herbivores in releasing corals from competition with kelp under warming ocean regimes. [ABSTRACT FROM AUTHOR]

Aim: Understanding the relative importance of climatic and non‐climatic distribution drivers for co‐occurring, functionally similar species is required to assess potential consequences of climate change. This understanding is, however, lacking for most ecosystems. We address this knowledge gap and forecast changes in distribution for habitat‐forming seaweeds in one of the world's most species‐rich temperate reef ecosystems. Location: The Great Southern Reef. The full extent of Australia's temperate coastline. Methods: We assessed relationships between climatic and non‐climatic environmental data known to influence seaweed, and the presence of 15 habitat‐forming seaweeds. Distributional data (herbarium records) were analysed with MAXENT and generalized linear and additive models, to construct species distribution models at 0.2° spatial resolution, and project possible distribution shifts under the RCP 6.0 (medium) and 2.6 (conservative) emissions scenarios of ocean warming for 2100. Results: Summer temperatures, and to a lesser extent winter temperatures, were the strongest distribution predictors for temperate habitat‐forming seaweeds in Australia. Projections for 2100 predicted major poleward shifts for 13 of the 15 species, on average losing 78% (range: 36%–100%) of their current distributions under RCP 6.0 and 62% (range: 27%–100%) under RCP 2.6. The giant kelp (Macrocystis pyrifera) and three prominent fucoids (Durvillaea potatorum, Xiphophora chondrophylla and Phyllospora comosa) were predicted to become extinct from Australia under RCP 6.0. Many species currently distributed up the west and east coasts, including the dominant kelp Ecklonia radiata (71% and 49% estimated loss for RPC 6.0 and 2.6, respectively), were predicted to become restricted to the south coast. Main conclusions: In close accordance with emerging observations in Australia and globally, our study predicted major range contractions of temperate seaweeds in coming decades. These changes will likely have significant impacts on marine biodiversity and ecosystem functioning because large seaweeds are foundation species for 100s of habitat‐associated plants and animals, many of which are socio‐economically important and endemic to southern Australia. [ABSTRACT FROM AUTHOR]

Kelp forests dominate wave-exposed rocky reefs along mid-to-high latitude coastlines. The distribution and structure of kelp forests is determined by a range of physical and biological processes operating across varying spatial and temporal scales. Many kelp forest systems are strongly influenced by herbivory, and overgrazing by urchins, in particular, is a recognised driver of kelp forest distribution and structure. The ecological significance of herbivory by kelp-associated limpets, however, has received far less attention. We quantified seasonal population dynamics of Laminaria digitata and the blue-rayed limpet Patella pellucida on two rocky shores in North Devon, UK. For the kelp, we quantified density, percent cover, morphology, standing biomass, elongation and erosion rates, and C:N and phenol content. For the limpet, we measured abundance, biomass, and morphology, and for the limpet-kelp interaction we recorded observable grazing damage on the blade. Both populations exhibited typical seasonality with kelp growth rates peaking in spring, maximum standing biomass observed in summer and increased erosion rates in autumn. Blue-rayed limpets, which were recorded within kelp holdfasts as well as on stipes and blades, recruited in spring and peaked in abundance in late summer, with length and biomass generally increasing through the year. The area of kelp blade damaged by limpet grazing was low (a maximum of ~4%) and relatively consistent throughout the year, and the number and size of grazing scars exhibited limited seasonality. Survey data from other L. digitata populations in the UK suggested that the limpet abundances recorded in North Devon were comparable with other sites in the region. Although the impact of P. pellucida grazing on kelp blade tissue appears to be minimal, further research into cavity grazing by limpets on the stipe and in the holdfast is needed to formerly assess the impact these cavities have on dislodgement and fracture rates, especially when increased occupancy and grazing coincides with periods of intense wave action. We conclude that while herbivory is an important processes acting upon many kelp populations globally, the grazing pressure exerted by P. pellucida on L. digitata is unlikely to strongly influence population structure on UK rocky shores. [ABSTRACT FROM AUTHOR]

Predators select prey so as to maximize energy and minimize manipulation time. In order to reduce prey detection and handling time, individuals must actively select their foraging space (microhabitat) and populations exhibit morphologies that are best suited for capturing locally available prey. We explored how variation in diet correlates with habitat type, and how these factors influence key morphological structures (mouth gape, eye diameter, fin length, fin area, and pectoral fin ratio) in a common microcarnivorous cryptic reef fish species, the triplefin Helcogrammoides cunninghami. In a mensurative experiment carried out at six kelp-dominated sites, we observed considerable differences in diet along 400 km of the Chilean coast coincident with variation in habitat availability and prey distributions. Triplefins preferred a single prey type (bivalves or barnacles) at northern sites, coincident with a low diversity of foraging habitats. In contrast, southern sites presented varied and heterogeneous habitats, where triplefin diets were more diverse and included amphipods, decapods, and cumaceans. Allometry-corrected results indicated that some morphological structures were consistently correlated with different prey items. Specifically, large mouth gape was associated with the capture of highly mobile prey such as decapods, while small mouth gape was more associated with cumaceans and copepods. In contrast, triplefins that capture sessile prey such as hydroids tend to have larger eyes. Therefore, morphological structures co-vary with habitat selection and prey usage in this species. Our study shows how an abundant generalist reef fish exhibits variable feeding morphologies in response to the distribution of potential habitats and prey throughout its range. [ABSTRACT FROM AUTHOR]

Sedentary polychaete Sabellaria spinulosa (Leukhart, 1849) is a suspension feeder that builds tubes by cementing together terrigenous particles. Under a set of environmental conditions, S. spinulosa can form reefs (consisting of hundreds or thousands of worm tubes) that can vary greatly in thickness, size and patchiness. The more-developed reefs form in areas with a large and continuous supply of sand, turbulent water, nutrient availability and rocky seafloor. Recently, for the first time in the Mediterranean area, a large reef of S. spinulosa has been discovered along the northern Gargano coast at Torre Mileto (Adriatic Sea, southern Italy). In this paper, we will detail the main sedimentological data of this worm reef. In order to evaluate the kind of terrigenous particles involved in the worm tube constructions, detailed grain-size and petrographic analyses were carried out on both reef and soft-sediment substrate samples. It is demonstrated that S. spinulosa selects sands on the basis of their grain size and shape, and not their composition. It is also shown that some seasonal variations of these parameters are the result of the interplay between reef growth and degradation periods mainly related to physical processes. In particular, the degradation stages seem to be induced mainly by storm wave action, while the reef growth is the result of the complex interaction between ecological and physical processes. [ABSTRACT FROM AUTHOR]

Impacts of mobile fishing gears on habitat and benthos have been well-documented; in contrast, less studied physical impacts of static fishing gear on benthic habitats are still debated. Pot fishing, is a growing sector in the UK and evidence of any impacts is needed to inform management. This study simulated high intensity experimental pot fishing on the epibenthos of two common UK reef habitats in Northumberland, UK. Single tethered pots were fished in intensively and lightly fished areas over the course of 2 months. Within each area, three experimental sites and control sites were surveyed before and after fishing using photoquadrats (n = 240 per 290 m² site) collected by scuba divers. PERMANOVA analysis indicated no evidence of epibenthic species abundances decreasing due to physical crushing or abrasion from potting on either intensively or lightly fished reefs. A shift in community composition over time was detected but was attributed to natural change as epibenthos in control sites shifted similarly. Experimental pot impacts far exceeded those of the local commercial pot fishery, providing relevant evidence for statutory governing bodies revisiting current fisheries management. Results are applicable across Western Europe due to the selection of habitats with abundant and commonly distributed benthic species. [ABSTRACT FROM AUTHOR]

Kelps are ecologically important primary producers and ecosystem engineers, and play a central role in structuring nearshore temperate habitats. They play an important role in nutrient cycling, energy capture and transfer, and provide biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and provide three-dimensional habitat structure for a vast array of marine plants and animals, including a number of commercially important species. Here, we review and synthesize existing knowledge on the functioning of kelp species as biogenic habitat providers. We examine biodiversity patterns associated with kelp holdfasts, stipes and blades, as well as the wider understorey habitat, and search for generality between kelp species and biogeographic regions. Environmental factors influencing biogenic habitat provision and the structure of associated assemblages are considered, as are current threats to kelp-dominated ecosystems. Despite considerable variability between species and regions, kelps are key habitat-forming species that support elevated levels of biodiversity, diverse and abundant assemblages and facilitate trophic linkages. Enhanced appreciation and better management of kelp forests are vital for ensuring sustainability of ecological goods and services derived from temperate marine ecosystems. [ABSTRACT FROM AUTHOR]

Reproduction of tropical species beyond their geographic range associated with ocean warming is regarded as the key indicator of a range shift. However, the lack of historical breeding records poses challenges for detecting distinct range shifts of tropical fishes. To obtain baseline data of the current status of the occurrence and breeding activity of tropical pomacentrid and apogonid fishes in ocean warming hotspots of temperate reefs (Kochi and Wakayama, 33°N) of Japan, we conducted a two-year underwater visual survey and synthesized those data with recently published information. By combining data from the present as well as past studies, the results confirmed the occurrence of 52 pomacentrid and 34 apogonid species, whereas breeding activity was confirmed for 19 and 16 species, respectively. Species richness and abundance of recruitment periphery and breeding active species were high at the warmer site adjacent to the Kuroshio Current. Most observed species were found beyond their known geographic range. Some species showing active breeding were widespread tropical fishes (e.g., Amphiprion clarkii, Pomacentrus coelestis and Apogon notatus) and probably have established breeding populations irrespective of recent global warming. The winter sea water temperature around the study sites will continue to rise, increasing by >2 °C by the end of the century; therefore, our results are highly relevant and represent the first step to elucidate the potential range extension of tropical fishes into temperate reefs with climate change. [ABSTRACT FROM AUTHOR]

The combination of ocean warming and acidification brings an uncertain future to kelp forests that occupy the warmest parts of their range. These forests are not only subject to the direct negative effects of ocean climate change, but also to a combination of unknown indirect effects associated with changing ecological landscapes. Here, we used mesocosm experiments to test the direct effects of ocean warming and acidification on kelp biomass and photosynthetic health, as well as climate-driven disparities in indirect effects involving key consumers (urchins and rock lobsters) and competitors (algal turf). Elevated water temperature directly reduced kelp biomass, while their turf-forming competitors expanded in response to ocean acidification and declining kelp canopy. Elevated temperatures also increased growth of urchins and, concurrently, the rate at which they thinned kelp canopy. Rock lobsters, which are renowned for keeping urchin populations in check, indirectly intensified negative pressures on kelp by reducing their consumption of urchins in response to elevated temperature. Overall, these results suggest that kelp forests situated towards the low-latitude margins of their distribution will need to adapt to ocean warming in order to persist in the future. What is less certain is how such adaptation in kelps can occur in the face of intensifying consumptive (via ocean warming) and competitive (via ocean acidification) pressures that affect key ecological interactions associated with their persistence. If such indirect effects counter adaptation to changing climate, they may erode the stability of kelp forests and increase the probability of regime shifts from complex habitat-forming species to more simple habitats dominated by algal turfs. [ABSTRACT FROM AUTHOR]

Subtidal forests comprised of kelps and other canopy-forming macroalgae represent critically important marine habitats. Kelp forests exhibit high rates of primary productivity, magnified secondary productivity, support high levels of biodiversity and provide various ecosystem services. Compared with many other regions, kelp forests around the UK have been largely understudied despite their recognised importance and the possible impacts of environmental change factors. We conducted surveys at 12 kelp-dominated open-coast sites within four regions in the UK, spanning ~ 9° in latitude and ~ 3 °C in mean sea temperature. We used a combination of quadrat-scale abundance and percent cover data as well as transect-scale canopy cover estimates to quantify ecological structure at multiple spatial scales. Kelp forest structure varied significantly between sites (nested within region) and also between regions. Regional-scale differences were principally driven by a higher abundance/cover of Alaria esculenta at the colder northern regions (i.e. north and west Scotland), and the presence of the Lusitanian kelp Laminaria ochroleuca at some sites in the southernmost region (i.e. southwest England) but nowhere else. The kelp Laminaria hyperborea dominated all sites and varied significantly between sites but not regions. All assemblage-level and population-level response variables were highly variable between sites within regions, suggesting that environmental factors varying at corresponding spatial scales (e.g. wave exposure, turbidity, sedimentation) are important drivers of pattern. The detection of regional-scale variability suggests that predicted changes in ocean climate, particularly increased sea temperature, may lead to changes in kelp forest structure in the future, with poleward range contractions (for A. esculenta ) and expansions (for L. ochroleuca ) likely. However, as the distribution-abundance patterns of the assemblage dominant L. hyperborea did not vary predictably with ocean temperature at this spatial scale, the fundamental structure of these habitats may be more influenced by localised factors, at least in the short-term. The relative importance of multiple, concurrent environmental change factors in structuring UK kelp forests remains largely unknown. [ABSTRACT FROM AUTHOR]

Kelp forests dominate temperate and polar rocky coastlines and represent critical marine habitats because they support elevated rates of primary and secondary production and high biodiversity. A major threat to the stability of these ecosystems is the proliferation of non-native species, such as the Japanese kelp Undaria pinnatifida ('Wakame'), which has recently colonised natural habitats in the UK. We quantified the abundance and biomass of U. pinnatifida on a natural rocky reef habitat over 10 months to make comparisons with three native canopy-forming brown algae ( Laminaria ochroleuca, Saccharina latissima, and Saccorhiza polyschides). We also examined the biogenic habitat structure provided by, and epibiotic assemblages associated with, U. pinnatifida in comparison to native macroalgae. Surveys conducted within the Plymouth Sound Special Area of Conservation indicated that U. pinnatifida is now a dominant and conspicuous member of kelp-dominated communities on natural substrata. Crucially, U. pinnatifida supported a structurally dissimilar and less diverse epibiotic assemblage than the native perennial kelp species. However, U. pinnatifida-associated assemblages were similar to those associated with Saccorhiza polyschides, which has a similar life history and growth strategy. Our results suggest that a shift towards U. pinnatifida dominated reefs could result in impoverished epibiotic assemblages and lower local biodiversity, although this could be offset, to some extent, by the climate-driven proliferation of L. ochroleuca at the poleward range edge, which provides complex biogenic habitat and harbours relatively high biodiversity. Clearly, greater understanding of the long-term dynamics and competitive interactions between these habitat-forming species is needed to accurately predict future biodiversity patterns. [ABSTRACT FROM AUTHOR]