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The ecological success of tropical corals is regulated by symbiotic dinoflagellate algae (Symbiodiniaceae). Corals can associate with multiple Symbiodiniaceae species simultaneously, yet the conditions that permit Symbiodiniaceae cohabitation are not understood. We examined how corals self-shade their own tissues causing within-colony light gradients that drive Symbiodiniaceae photoacclimatory processes and positional genetic disparity. Paired light ‘exposed’ and ‘shaded’ samples from 20 coral species were collected from a shallow coral reef (Rarotonga, Cook Islands). Through active chlorophyll fluorometry, rapid light curves revealed that exposed Symbiodiniaceae exhibited 50% higher values in minimum saturating irradiances and demonstrated a shift towards preferential nonphotochemical quenching [1 – Q], consistent with higher overall light exposure. High-throughput or targeted DNA sequencing of ITS2 and psbAncr markers demonstrated that corals harboured distinct and/or differentially abundant Symbiodiniaceae ITS2 sequences (typically rare in relative abundance) or multiple ITS2 intragenomic variant profiles across shaded vs exposed regions. In Hydnophora cf. microconos, within-colony symbiont genetic disparity was positively correlated with the magnitude of difference in [1 – Q] utilisation. Together, these results suggest that within-colony light gradients produce distinct optical niches that enable symbiont cohabitation via photoadaptation, a phenomenon that is expected to increase the adaptive capacity of corals under future climates.

Understanding the effects of climate change on fish biology and ecology is crucial for effective management of fisheries resources. Estuaries are warming at a faster rate than nearby oceans in south-eastern Australia, yet there is little understanding of how this may impact the growth of estuarine fish. We examined long-term changes and drivers of growth in an ecologically and economically important estuarine fish in this region, the mulloway Argyrosomus japonicus, using a growth chronology spanning 39 yr (1980-2018). The chronology was developed using 3112 otoliths collected over 12° of latitude. Mixed effects models identified a long-term increase in the growth rate of A. japonicus spanning nearly 3 decades in south-eastern Australia and a positive growth response to temperature. Temperature during the months of November-February best explained this growth response, likely representing a specific growing season for the species. However, there also remained some variation in growth not explained by increasing temperature over the period. We also found evidence of faster growth in individuals sampled at both younger and older ages, potentially caused by selectivity mechanisms. Regional climate forecasts predict that, based upon the observed response to temperature, the mean annual growth rate of A. japonicus in south-eastern Australia may increase by up to 8.9% by 2099. These results add to the growing body of literature demonstrating positive growth responses by marine species in warming environments and highlight the value of understanding the drivers of long-term growth variation in exploited fish stocks in order to predict future productivity under a range of environmental and fisheries management scenarios.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.1. From measurements at several weir pool sites along the turbid and freshwater Barwon-Darling River, Australia, the development of persistent stratification (for periods of >5 days) was related to river discharge. For the sites examined, the required discharge to allow the development of persistent stratification was between 100 and 450 ML day−1 during the hotter months. High discharge during the hotter months did not allow the formation of persistent stratification, although diel stratification did occur. Low discharge through the cooler months resulted in diel stratification, although persistent stratification lasting for a few days could occur at times.2. The growth and dominance of Anabaena circinalis at these sites was closely related to the establishment and maintenance of persistent and strong thermal stratification. Growth only occurred during extended periods (>5 days) of persistent stratification. These conditions not only restrict the displacement of A. circinalis downstream, they also allowed the alga to accumulate in surface waters.3. The discharge levels required to suppress the formation of persistent stratification at the study sites were variable because of large differences in channel cross-sectional area. To compensate for this variation, the discharges were converted to flow velocities. A critical velocity of 0.05 ms−1 was sufficient for the suppression of persistent thermal stratification and concurrent A. circinalis growth for all sites. The turbulent velocity (u*) under weak wind mixing at the study locations varied between 2.66 × 10−3 and 2.91 × 10−3 ms−1 at the critical flow velocities. These values may have potential to be applied to other rivers in similar climatic zones to suppress nuisance cyanobacterial growth.

© The Author 2014. Published by Oxford University Press. All rights reserved. The zooplankton community changes that may occur with increases in concentration of allochthonous dissolved organic carbon (DOC) are not well understood in unconstrained lowland rivers. We examined in mesocoms over 8 days the short-term responses of river zooplankton to amendments of DOC from two different sources, glucose and leachates of a common riparian tree (Eucalyptus camaldulensis; river red gum) both alone and with inorganic nutrients added. DOC additions with and without nutrients increased heterotrophic respiration and led to significant increases in bacterial biomass. These responses varied between glucose and leachate addition. In treatments with added DOC, zooplankton density significantly increased relative to controls. Some zooplankton genera only responded to the leachate as a DOC source, and community structures significantly varied between the control and the glucose and leachate amendments. Zooplankton are particularly important in lowland river systems as they are key organisms for the transfer of carbon to higher trophic levels and this study indicates that allochthonous DOC has the potential to be an important basal resource to lowland river food webs. This may be particularly important in lowland sections of unconstrained flood plain rivers during and immediately following floods when allochthonous DOC is more available.

The biological carbon pump transports photosynthetically fixed carbon from surface waters to depths. It removes carbon from the atmosphere and sequesters it in the deep ocean, playing an important role in global climate regulation. As the biological carbon pump is directly related to biological processes, it is heavily influenced by the biomass and trophic interactions between populations in the ecosystem. However, behavioral responses and adaptations to predation risk change trophic interactions, potentially having larger impacts than direct effects on trophic interactions and population abundances. Thus, predation risk may play an important role in shaping the biological carbon pump's strength (how much carbon leaves the euphotic zone) and efficiency (what fraction of detritus reaches a certain depth without being degraded). Except in the case of active carbon transport by vertically migrating organisms, this role of risk is not generally recognized. Here, we synthesize the existing knowledge on the consequences of anti-predation responses on the biological carbon pump. First, we consider a generic anti-predation response and investigate the different direct, indirect, and cascading effects that the response can induce. Then, we focus on pelagic anti-predation responses and detail how they can specifically alter the different components of the pump. Finally, we discuss points to consider in biological carbon pump studies and highlight directions for future research. In particular, there is a need for more quantitative research to evaluate the importance of anti-predation responses in shaping the biological carbon pump.

Efforts to manage coral reef declines are increasingly turning towards in situ propagation of corals to aid reef recovery. Understanding the factors that influence ‘success’ throughout the propagation process is therefore critical to ensure efforts are viable and cost-effective, yet the extent to which propagation practices potentially impact the underlying coral biology remains unknown. Given growing evidence for the importance of the coral microbiome, we examined the influence of nursery-based propagation and out-planting on the bacterial communities of two coral species–Acropora millepora and Pocillopora verrucosa–increasingly propagated on the northern Great Barrier Reef (Opal Reef). Bacterial communities of coral fragments were characterised over four months of nursery propagation (sampling points: zero, seven and 125 days) and one month of subsequent out-planting (sampling points: zero, one and 30 days). Bacterial community structure differed between A. millepora and P. verrucosa throughout the experiment and species-specific temporal dynamics were observed during the transplantation of corals into nurseries and subsequent out-planting back to the reef. P. verrucosa bacterial community structure remained stable over time in the natural reef environment and within the nursery. In contrast, A. millepora bacterial communities within the nursery significantly changed over time, whereas those associated with source colonies within the natural reef environment remained unchanged. However, after one month of out-planting, the composition, richness and diversity of A. millepora bacterial communities were not statistically different to those associated with the source colonies. We interpret the transient shift of A. millepora bacterial communities within the nursery as an impact of distinctive environmental conditions in nurseries compared to natural reef settings, and the greater responsiveness of A. millepora bacterial communities to environmental change. Our observations highlight that different coral species exhibit distinct microbial responses to coral propagation and out-planting, and we recommend that these should be considered when designing and scaling future coral management strategies.

Diel vertical migration (DVM) is a common behavior among marine organisms to balance the trade-off between surface feeding opportunities and predation-related mortality risk. Body size is a master trait that impacts predation risk to both visual and nonvisual predators. Acoustic measurements from the autonomous Zooglider revealed size-dependent DVM behaviors in the San Diego Trough. Dual frequency (200 and 1000 kHz) backscatter, in conjunction with physical properties of the ambient water and optical imaging of zooplankton, were recorded during 12 Zooglider missions over 2yr. Acoustic size-categories were identified based on the theoretical scattering properties of dominant taxonomic groups identified optically by the Zoocam. Acoustic modeling suggests that the measured acoustic backscatter in this region is largely dominated by copepods, with appreciable contributions from other taxa. We found that larger organisms migrated deeper (245–227 m) and faster (> 20 m h−1) compared to smaller organisms (156 m, > 15 m h−1). Larger organisms entered the upper layer of the water column later in the evening (0.2–1.5h later) and descended into deeper water earlier in the morning (0.4–3.7h earlier) than smaller-bodied organisms, consistent with body size-dependent visual predation risk. The variability in daytime depths occupied by small, intermediate, and large-bodied backscatterers was related to the depth of the euphotic zone, again consistent with light-dependent risk of predation.

As historically described, the genus Amphidinum has long been recognized to be polyphyletic. Amphidinium sensu lato is the most diverse of all marine benthic dinoflagellate genera and after the redefinition of the sensu stricto genus about 100 species remained of unknown generic affiliation. A species similar to the Australian sensu lato species Amphidinium boggayum was discovered in France. Morphological and molecular phylogenetic data supported the description of a new species and the classification of the two closely related species within a new athecate, photosynthetic, benthic genus, named Bindiferia. Cells were dorsoventrally flattened with smaller asymmetric epicone. The cingulum was descending. The sulcus reached the antapex and had an extension onto the epicone. The apical structure complex formed an anticlockwise loop around the apex. A red stigma was located in the anterior part of the epicone, near the apex. Vegetative division occurred in a non-motile stage within a hyaline sheath. Non-motile cells had dorsal hypocone grooves. The two species differed from each other in epicone size, cingulum displacement, nucleus location and surface groove occurrence. The molecular phylogenetic results showed that Bindiferia is a distinct taxon that is only distantly related to Amphidinium sensu stricto. The nearest sister group to Bindiferia could not be reliably determined, but the apical structure complex suggested a close relationship to the genera of the Gymnodinium sensu stricto clade.

Estuaries are among the most productive of aquatic ecosystems. Yet the collective understanding of patterns and drivers of primary production in estuaries is incomplete, in part due to complex hydrodynamics and multiple controlling factors that vary at a range of temporal and spatial scales. A whole-ecosystem experiment was conducted in a deep, pelagically dominated terminal channel of the Sacramento-San Joaquin Delta (California, USA) that seasonally appears to become nitrogen limited, to test whether adding calcium nitrate would stimulate primary productivity or increase phytoplankton density. Production did not respond consistently to fertilization, in part because nitrate and phytoplankton were dispersed away from the manipulated area within 1–3 days. Temporal and spatial patterns of gross primary production were more strongly related to stratification and light availability (i.e., turbidity) than nitrogen, highlighting the role of hydrodynamics in regulating system production. Similarly, chlorophyll was positively related not only to stratification but also to nitrogen—with a positive interaction—suggesting stratification may trigger nutrient limitation. The average rate of primary production (4.3 g O2 m−2 d−1), metabolic N demand (0.023 mg N L−1 d−1), and ambient dissolved inorganic nitrogen concentration (0.03 mg N L−1) indicate that nitrogen can become limiting in time and space, especially during episodic stratification events when phytoplankton are isolated within the photic zone, or farther upstream where water clarity increases, dispersive flux decreases, and stratification is stronger and more frequent. The role of hydrodynamics in organizing habitat connectivity and regulating physical and chemical processes at multiple temporal and spatial scales is critical for determining resource availability and evaluating biogeochemical processes in estuaries.

Hydraulic retention time (HRT) in wastewater treatment high rate algal ponds is an important operational parameter that determines both nutrient loading and effluent water quality. Shorter HRT increases the influent nutrient loading, and ultimately, areal microalgal productivity, but decreases effluent quality. Recycling a proportion of the effluent water can decrease the HRT whilst maintaining the same nutrient loading. This study investigated how partially and fully harvested recycled effluent affected microalgal performance, with respect to nutrient removal and biomass production in high rate algal mesocosms operated on shortened (summertime) 4-day HRT compared to longer (wintertime) 8-day HRT. Recycling partially harvested effluent water, still containing some microalgal/bacterial biomass, negatively affected the net biomass production, relatively to all other treatments. This was due to the diminished light climate and photosynthetic potential within the mesocosm, as a result of biomass loading. On the other hand, recycling fully harvested effluent to decrease the HRT by half did allow for higher daily biomass productivity compared to high rate algal mesocosms run on an 8-day HRT. However, it did not result in any increase in wastewater treatment over that in the 8-day full-load HRT treatment but had higher effluent quality than that of the 4-day full-load HRT treatment. Recycling effluent has the potential to increase microalgal biomass production, without degrading effluent quality, to further improve the economics of coupled wastewater treatment and resource recovery, but complete or near-complete harvesting of biomass is required.

Foundation seaweed species are experiencing widespread declines and localized extinctions due to increased instability of sea surface temperature. Characterizing temperature thresholds are useful for predicting patterns of change and identifying species most vulnerable to extremes. Existing methods for characterizing seaweed thermal tolerance produce diverse metrics and are often time-consuming, making comparisons between species and techniques difficult, hindering insight into global patterns of change. Using three kelp species, we adapted a high-throughput method - previously used in terrestrial plant thermal biology - for use on kelps. This method employs temperature-dependent fluorescence (T-F0 ) curves under heating or cooling regimes to determine the critical temperature (Tcrit ) of photosystem II (PSII), i.e., the breakpoint between slow and fast rise fluorescence response to changing temperature, enabling rapid assays of photosynthetic thermal tolerance using a standardized metric. This method enables characterization of Tcrit for up to 48 samples per two-hour assay, demonstrating the capacity of T-F0 curves for high-throughput assays of thermal tolerance. Temperature-dependent fluorescence curves and their derived metric, Tcrit , may offer a timely and powerful new method for the field of phycology, enabling characterization and comparison of photosynthetic thermal tolerance of seaweeds across many populations, species, and biomes.

Ocean warming endangers coastal ecosystems through increased risk of infectious disease, yet detection, surveillance, and forecasting of marine diseases remain limited. Eelgrass (Zostera marina) meadows provide essential coastal habitat and are vulnerable to a temperature-sensitive wasting disease caused by the protist Labyrinthula zosterae. We assessed wasting disease sensitivity to warming temperatures across a 3500 km study range by combining long-term satellite remote sensing of ocean temperature with field surveys from 32 meadows along the Pacific coast of North America in 2019. Between 11% and 99% of plants were infected in individual meadows, with up to 35% of plant tissue damaged. Disease prevalence was 3× higher in locations with warm temperature anomalies in summer, indicating that the risk of wasting disease will increase with climate warming throughout the geographic range for eelgrass. Large-scale surveys were made possible for the first time by the Eelgrass Lesion Image Segmentation Application, an artificial intelligence (AI) system that quantifies eelgrass wasting disease 5000× faster and with comparable accuracy to a human expert. This study highlights the value of AI in marine biological observing specifically for detecting widespread climate-driven disease outbreaks., This work was supported by the National Science Foundation (awards OCE-1829921, OCE-1829922, OCE-1829992, OCE-1829890). This is contribution 104 from the Smithsonian's MarineGEO and Tennenbaum Marine Observatories Network.

The dinoflagellate family Symbiodiniaceae comprises numerous genera and species with large differences in diversity, ecology and geographic distribution. An evolutionarily divergent lineage common in temperate symbiotic cnidarians and designated in the literature by several informal names including ‘temperate–A’, AI, Phylotype A´ (A-prime) and ‘Mediterranean A’, is here assigned to the genus Philozoon. This genus was proposed by Geddes (1882) in one of the earliest papers that recognized ‘yellow cells’ as distinct biological entities separate from their animal and protist hosts. Using phylogenetic data from nuclear (rDNA), chloroplast (cp23S) and mitochondrial genes (cob and cox1), as well as morphology (cell size), ecological traits (host affinity) and geographic distributions, we emend the genus Philozoon Geddes and two of its species, P. medusarum and P. actiniarum, and describe six new species. Each symbiont species exhibits high host fidelity for particular species of sea anemone, soft coral, stony coral and a rhizostome jellyfish. Philozoon is most closely related to Symbiodinium (formerly Clade A), but, unlike its tropical counterpart, occurs in hosts in shallow temperate marine habitats in northern and southern hemispheres including the Mediterranean Sea, north-eastern Atlantic Ocean, eastern Australia, New Zealand and Chile. The existence of a species-diverse lineage adapted to cnidarian hosts living in high latitude habitats with inherently wide fluctuations in temperature calls further attention to the ecological and biogeographic reach of the Symbiodiniaceae.

Worldwide, many coral reefs are at risk of shifting to degraded algal-dominated states, due to compromised ecological conditions. Functional diversity of herbivorous fishes maintains coral reef health and promotes reef resilience to disturbances. Given previous evidence, it appears the functional roles of herbivorous fishes differ across geographical locations, indicating a need for further assessment of macroalgal consumption by herbivorous fishes. We assessed functional diversity by examining foraging behavior of herbivorous fish species on macroalgae on a fringing reef in Moorea, French Polynesia. We video-recorded choice experiments containing seven common macroalgae and used Strauss' linear resource selection index to determine macroalgal selectivities. We used cluster analysis to identify any distinct groups within herbivorous fish species, given the macroalgal species they targeted, and fitted generalized linear mixed-effects models to identify factors that best predicted the number of bites taken on macroalgae. Seven species from 3 fish families/tribes took a total of 956 bites. Fish species differed in their selectivity with some species (Naso lituratus, N. unicornis, Calatomus carolinus) strongly preferring one or two macroalgal species, while other fish species (Acanthurus nigrofuscus, Ctenochaetus striatus, Chlorurus sordidus, Balistapus undulatus) were less selective. This resulted in fish species forming two clusters. Only 3 of 7 macroalgae were preferred by any fish species, with two fish species both preferring the same two macroalgae. The limited differences in fish species' preferences for different macroalgae suggests limited functional complementarity. Two models (macroalgal species identity+fish functional group, macroalgal species identity+fish species) best predicted the number of bites taken on macroalgae compared to models incorporating only a single explanatory factor or fish family. In the context of this Moorean fringing reef, there is greater functional redundancy than complementarity of herbivorous fishes consuming macroalgae, and the fishes grouped together according to their relative selectivity. We observed fish species that are not classified as browsers consuming macroalgae, suggesting diets of herbivorous fishes may be broader than previously thought. Finally, we observed macroalgal selectivities and consumption that differed from previous studies for the same fish species. Our results contribute to the understanding of functional diversity of herbivorous fishes across coral reefs, and also highlight the need for additional research to further elucidate the role of context and functional diversity of herbivorous fishes consuming macroalgae on coral reefs.

Climate change is altering naturally fluctuating environmental conditions in coastal and estuarine ecosystems across the globe. Departures from long-term averages and ranges of environmental variables are increasingly being observed as directional changes [e.g., rising sea levels, sea surface temperatures (SST)] and less predictable periodic cycles (e.g., Atlantic or Pacific decadal oscillations) and extremes (e.g., coastal flooding, marine heatwaves). Quantifying the short- and long-term impacts of climate change on tidal marsh seascape structure and function for nekton is a critical step toward fisheries conservation and management. The multiple stressor framework provides a promising approach for advancing integrative, cross-disciplinary research on tidal marshes and food web dynamics. It can be used to quantify climate change effects on and interactions between coastal oceans (e.g., SST, ocean currents, waves) and watersheds (e.g., precipitation, river flows), tidal marsh geomorphology (e.g., vegetation structure, elevation capital, sedimentation), and estuarine and coastal nekton (e.g., species distributions, life history adaptations, predator-prey dynamics). However, disentangling the cumulative impacts of multiple interacting stressors on tidal marshes, whether the effects are additive, synergistic, or antagonistic, and the time scales at which they occur, poses a significant research challenge. This perspective highlights the key physical and ecological processes affecting tidal marshes, with an emphasis on the trophic linkages between marsh production and estuarine and coastal nekton, recommended for consideration in future climate change studies. Such studies are urgently needed to understand climate change effects on tidal marshes now and into the future.

An increase in cases of ciguatera poisoning (CP) and expansion of the causative species in the South Pacific region highlight the need for baseline data on toxic microalgal species to help identify new areas of risk and manage known hot spots. Gambierdiscus honu is a toxin producing and potential CP causing dinoflagellate species, first described in 2017. Currently no high-resolution geographical distribution, intraspecific genetic variation or toxin production diversity data is available for G. honu. This research aimed to further characterize G. honu by investigating its distribution using species-specific real-time polymerase chain reaction assays at 25 sites in an area spanning ∼8000 km of the Coral Sea/Pacific Ocean, and assessing intraspecific genetic variation, toxicity and toxin production of isolated strains. Assessment of genetic variation of the partial rRNA operon of isolates demonstrated no significant intraspecific population structure, in addition to a lack of adherence to isolation by distance (IBD) model of evolution. The detected distribution of G. honu in the Pacific region was within the expected tropical to temperate latitudinal ranges of 10° to -30° and extended from Australia to French Polynesia. In the lipophilic fractions, the neuroblastoma cell-based assay (CBA-N2a) showed no ciguatoxin (CTX)-like activity for nine of the 10 isolates, and an atypical pattern for CAWD233 isolate which showed cytotoxic activity in OV- and OV+ conditions. In the same way, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis confirmed no Pacific-CTXs (CTX-3B, CTX-3C, CTX-4A, CTX-4B) were produced by the ten strains. The CBA-N2a assessment of the hydrophilic fractions showed moderate to high cytotoxicity in both OV- and OV+ condition for all the strains showing a cytotoxic profile similar to that of gambierone. Indeed, this study is the first to show the cytotoxic activity of gambierone on mouse neuroblastoma cells while no cytotoxicity was observed when 44-MG was analysed at the same concentrations using the CBA-N2a. Analysis of the hydrophilic via LC-MS/MS confirmed production of gambierone in all isolates, ranging from 2.1 to 38.1 pg/cell, with 44-methylgambierone (44-MG) also produced by eight of the isolates, ranging from 0.3 to 42.9 pg/cell. No maitotoxin-1 was detected in any of the isolates. Classification of the G. honu strains according to the quantities of gambierone produced aligned with the classification of their cytotoxicity using the CBA-N2a. Finally, no maitotoxin-1 (MTX) was detected in any of the isolates. This study shows G. honu is widely distributed within the Pacific region with no significant intraspecific population structure present. This aligns with the view of microalgal populations as global metapopulations, however more in-depth assessment with other genetic markers could detect further structure. Toxicity diversity across 10 isolates assessed did not display any geographical patterns.

Environmental DNA (eDNA) metabarcoding is increasingly being used to assess community composition in coastal ecosystems. In this study, we chose to examine temporal and spatial changes in the aquatic community of Manly Lagoon - one of the most heavily developed and polluted estuaries in eastern Australia. Based on metabarcoding of the 16S mitochondrial gene (for fish) and the 18S nuclear gene (for macroinvertebrates), we identified seasonal differences in fish and macroinvertebrate community composition as well as species richness, which correlated, in some cases, with the environmental parameters of sea surface temperature and freshwater input. Moreover, given the greater taxonomic resolution of fish versus macroinvertebrate assignments, we identified several known migratory fish species of management importance that contributed significantly to the overall patterns observed. Overall, our data support the use of eDNA metabarcoding to track fish assemblages shifting in response to environmental drivers in polluted estuaries with increased sampling and consultation with historical data.

Cyanobacterial blooms have major impacts on the ecological integrity and anthropogenic value of freshwater systems. Chrysosporum ovalisporum, a potentially toxic cyanobacteria has been rare in Australian waters until recently when is has bloomed in a number of lake and river systems. The aim of this study was to determine drivers of its growth and growing dominance. We performed regular monitoring of Mannus Lake, a small freshwater reservoir in South-Eastern Australia that has recently undergone extremely dense bloom events. Blooms of the diazotrophic Chrysosporum ovalisporum occurred in both summers of the 19 month study during periods of persistent thermal stratification. Following the C. ovalisporum blooms, non-diazotrophic taxa (Microcystis aeruginosa and Woronichinia sp.) dominated the phytoplankton community under less stratified conditions. Thermal stratification and nitrogen availability appeared to be the primary drivers of changes in cyanobacterial community structure. We propose that the observed transition from C. ovalisporum to M. aeruginosa and/or Woronichinia sp. may be a result of nitrogen limitation in early summer, which combined with persistent thermal stratification led to an ecological advantage for the nitrogen-fixing C. ovalisporum. Mixing events caused the senescence of the C. ovalisporum bloom, likely supplementing the nutrient budget of the lake with atmospherically derived N and alleviating N limitation to non-diazotrophic taxa. Non-diazotrophic cyanobacterial growth then increased, albeit at much lower biovolumes compared to the initial bloom. Overall, the results demonstrate the role of thermal stratification and nutrient cycling in structuring the cyanobacterial community and provide insights into the environmental factors driving the proliferation of the relatively new, potentially toxic cyanobacterium C. ovalisporum in Australian waters.

Ammonia oxidation by ammonia-oxidising archaea (AOA) and bacteria (AOB) is the first and rate-limiting step of nitrification. By providing substrate to the nitrogen–removing denitrification processes, nitrification is an important process for attenuation of allochthonous nitrogen loads in urban rivers, thereby mitigating eutrophication of downstream ecosystems. However, the relative importance of AOA and AOB communities in ammonia oxidation, the distribution and varied patterns of these groups and the underlying mechanisms have received limited study in hypereutrophic urban river networks. To investigate spatial and temporal patterns of particle-attached and free-living ammonia-oxidising microbial communities, we conducted a 2-year study of four different water quality/habitat conditions within a hypereutrophic urban river network of eastern China. The structure and dynamics of ammonia-oxidising microbial communities were determined by high-throughput sequencing based on the AOA and AOB amoA gene. We found significant spatial and temporal heterogeneity of ammonia-oxidising microbial communities, but no significant differences between particle-attached and free-living fractions. Analysis revealed that changes in the diversity and composition of ammonia-oxidising microbial communities were mainly related to substrate availability (e.g., ammonia, nitrite, dissolved oxygen). AOB communities were more complex and had a higher species richness and diversity compared with AOA communities. Our findings indicate that high anthropogenic nitrogen loadings appear to promote higher ammonia-oxidising microbial richness and diversity, and AOB are more adaptable to the hypereutrophic conditions, thereby playing a more important role than AOA in nitrogen transformations in hypereutrophic urban river networks. This study highlights the importance of ammonia-oxidising microorganisms in nutrient-rich river systems and provides valuable insights into ammonia transport and transformations in urban river networks.

More than half of the fish biomass of coastal rocky reefs depends on zooplankton however the trophic basis of estuarine fish assemblages remains unknown We quantified the trophic basis i e basal energy sources of fish community biomass inhabiting three habitat types seagrass natural reef and artificial reef in two estuaries compared with two coastal rocky reef sites Fish assemblages were surveyed with Baited Remote Underwater Video BRUVs and the species abundance richness and biomass of fish were classified into nine functional feeding groups 6 teleost and 3 elasmobranch Comparable metrics for coastal fish assemblages were obtained from published surveys using BRUVs Using the functional feeding group biomass and the group specific diet composition the breakdown of energy sources was calculated using a food web analysis Estuarine reef habitats had different species and different functional feeding group composition than seagrass habitat The majority of fish biomass in the seagrass habitat was supported by detritus 51 in Botany Bay or macrophytes 58 in Lake Macquarie In contrast zooplankton supported most fish biomass 45 59 at the coastal reef locations and in reef habitat in one estuary 35 43 but not the other estuary 33 34 Trophic pathways which support fish assemblages are key in identifying mitigation measures which can help conserve these populations with growing urbanisation of estuaries and coasts 2022 The Author s under exclusive licence to Springer Verlag GmbH Germany part of Springer Nature

In late 2018 to early 2019, three significant fish death events occurred in the Lower Darling River, Australia, with mortality estimates of millions of fish. We examined the proximate and ultimate causes of these events. We determined that not only were the conditions existing at the time a significant contributing factor, but that antecedent conditions, particularly during the period 2010–17, also contributed. The extreme hot and dry climate during 2018, extending into 2019, shaped the conditions that saw a large fish biomass, which had flourished in the Darling River and Menindee Lakes since favourable spawning conditions in 2016, isolated in weir pools, with no means of escaping upstream or downstream. Strong and persistent weir pool stratification created hypoxic conditions in the hypolimnion. A series of sudden cool changes subsequently initiated rapid and sudden mixing of the stratified waters, causing depletion of oxygen throughout the water column and resulting in the fish deaths. The events were also shaped by broader climatic, hydrological and basin management contexts that placed the Lower Darling River at risk of such fish deaths. Our observations have implications for future river management, and we make several suggestions how policy makers and river operators can minimise fish death risks into the future.

Stock-recruitment relationships for managing commercial fisheries are difficult to measure and notoriously poor, so marine ecologists have relied on larval recruitment as a proxy for how planktonic processes regulate populations and communities. However, my literature review revealed that coupling between reproductive output and recruitment in benthic populations was common, occurring in 62% of 112 studies and 64% of 81 species. Coupling was considerably stronger for studies on brooders (72%) than broadcast-spawners (46%) and taxa with short (74%) than long (56%) planktonic larval durations (PLDs); hence, it was highest for brooders with short PLDs (94%). Coupling was similar in studies on benthic animals (63%) and seagrasses and kelp (56%). Coupling was detected more often by quantifying both reproductive output and settlement (79%) than adult density and recruitment (60%). It also was detected in 83% of just 21% of studies that estimated dispersal. Coupling was even detected by 55% of the 46% of studies conducted at just one site and 58% of the 65% of studies lasting no longer than 3 years. Decoupling was detected 33 times in invertebrates and fishes, occurring more often in the plankton (48.5%) and during reproduction (45.5%) than after settlement (6%), and nine times in seagrasses and kelp, occurring more often during reproduction (44.4%) than postsettlement (33.3%) or in the plankton (22.2%). Widespread coupling between reproductive output and settlement for sedentary, benthic species suggests that the poor stock-recruitment relationships typical of vagile, wide-ranging, pelagic species may be due more to the difficulty of detecting them than decoupling.

© 2020, Springer Nature Switzerland AG. Temperature plays a fundamental role in determining phytoplankton community structure, distribution, and abundance. With climate models predicting increases in ocean surface temperatures of up to 3.2°C by 2100, there is a genuine need to acquire data on the phenotypic plasticity, and thus performance, of phytoplankton in relation to temperature. We investigated the effects of temperature (14–28°C) on the growth, morphology, productivity, silicification and macromolecular composition of the marine diatom Thalassiosira pseudonana. Optimum growth rate and maximum P:R ratio were obtained around 21°C. Cell volume and chlorophyll a increased with temperature, as did lipids and proteins. One of the strongest temperature-induced shifts was the higher silicification rates at low temperature. Our results reveal temperature-driven responses in physiological, morphological and biochemical traits in T. pseudonana; whereby at supra-optimal temperatures cells grew slower, were larger, had higher chlorophyll and protein content but reduced silicification, while those exposed to sub-optimal temperatures were smaller, heavily silicified with lower lipid and chlorophyll content. If these conserved across species, our findings indicate that as oceans warm, we may see shifts in diatom phenotypes and community structure, with potential biogeochemical consequences of higher remineralisation and declines in carbon and silicon export to the ocean interior.

Microalgae form the base of the Antarctic marine food web and through their conversion of nutrients into biomass, are the principal source of energy for higher trophic levels. Environmental conditions strongly influence microalgal photophysiology, biochemistry and macromolecular composition, which has implications for the quality and quantity of energy available for transfer through the food web. Here we assessed the photosynthetic performance, biochemical (dimethylsulfoniopropionate; DMSP) and macromolecular composition (lipids, carbohydrates and proteins) of selected diatoms sampled from 2 distinct Antarctic marine environments, namely the late spring bottom sea ice (sympagic) and near-shore ice-free coastal waters (pelagic). The photosynthetic efficiency and photoprotective capacity of the communities differed significantly, and chlorophyll a-specific gross primary productivity was 4-fold greater in the pelagic community. At the community level, pelagic microalgae had the highest DMSP content (1.4 nmol [µg chl a]-1) and the highest potential rates of DMSP lyase activity (0.87 nmol [µg chl a]-1 h-1). Comparisons within each community showed taxon-specific differences in macromolecular composition, which were strongest amongst the sympagic diatoms. Comparing across communities, pelagic diatoms had lower lipid to protein ratios, whereas sympagic diatoms were lipid rich and had significantly higher content of unsaturated fatty acids. These findings show variability in the physiology and nutritional quality of the base of the food web depending on habitat and taxonomic group and emphasise the importance of the sympagic community for providing a concentrated source of high-energy compounds during the pulsed productivity events for key grazers such as krill to survive through long dark winters.

The 2015–2016 El Niño provided insight into how low-inflow estuaries might respond to future climate regimes, including high sea levels and more intense waves. High waves and water levels coupled with low rainfall along the Southern California coastline provided the opportunity to examine how extreme ocean forcing impacts estuaries independently from fluvial events. From November 2015 to April 2016, water levels were measured in 13 Southern California estuaries, including both intermittently closed and perennially open estuaries with varying watershed size, urban development, and management practices. Elevated ocean water levels caused raised water levels and prolonged inundation in all of the estuaries studied. Water levels inside perennially open estuaries mirrored ocean water levels, while those inside intermittently closed estuaries (ICEs) exhibited enhanced higher-high water levels during large waves, and tides were truncated at low tides due to a wave-built sand sill at the mouth, resulting in elevated detided water levels. ICEs closed when sufficient wave-driven sand accretion formed a barrier berm across the mouth separating the estuary from the ocean, the height of which can be estimated using estuarine lower-low water levels. During the 2015–2016 El Niño, a greater number of Southern California ICEs closed than during a typical year and ICEs that close annually experienced longer than normal closures. Overall, sill accretion and wave exposure were important contributing factors to individual estuarine response to ocean conditions. Understanding how estuaries respond to increased sea levels and waves and the factors that influence closures will help managers develop appropriate adaptation strategies.

Author(s): Liu, W; Chen, X; Strong, DR; Pennings, SC; Kirwan, ML; Chen, X; Zhang, Y | Abstract: Introduced plants provide a unique opportunity to examine how plants respond through plasticity and adaptation to changing climates. We compared plants of Spartina alterniflora from the native (United States, 27–43°N) and introduced (China, 19–40°N) ranges. In the field and greenhouse, aboveground productivity of Chinese plants was greater than that of North American plants. Aboveground biomass in the field declined with increasing latitude in the native range, a pattern that persisted in the greenhouse, indicating a genetic basis. Aboveground biomass in the field displayed hump-shaped relationships with latitude in China, but this pattern disappeared in field and greenhouse common gardens, indicating phenotypic plasticity. Relationships in both geographic regions were explained by temperature, which is probably the underlying environmental factor affecting aboveground biomass. S. alterniflora has evolved greater biomass in China, but in the four decades since it was introduced, it has not yet evolved the genetic cline in biomass seen in its native range. By working at lower latitudes in the introduced range than have been sampled in the native range, we identified an optimum temperature in the introduced range above which aboveground productivity decreases.

Author(s): Hetherington, Elizabeth D; Kurle, Carolyn M; Benson, Scott R; Jones, T Todd; Seminoff, Jeffrey A

© 2019 The authors. Corals live in symbiosis with algal dinoflagellates, which can achieve outstanding photo - synthetic energy efficiencies in hospite approaching theo retical limits. However, how such photosynthetic efficiency varies with environmental stress remains poorly known. Using fiber-optic and electrochemical microsensors in combination with variable chlorophyll fluorescence imaging, we investigated the combined effects of thermal stress and active feeding on the radiative energy budget and photosynthetic efficiency of the symbiotic coral Pocillopora sp. At ambient temperature (25°C), the percentage of ab sorbed light energy used for photosynthesis under low irradiance was higher for fed (∼5-6%) compared to unfed corals (4%). Corals from both feeding treatments responded equally to stress from high light ex posure (2400 μmol photons m-2 s-1), exhibiting a de crease in photosynthetic efficiency, down to 0.5-0.6%. Fed corals showed increased resilience to thermal-induced bleaching (loss of symbionts) compared to unfed corals. In addition, while unfed corals decreased their photosynthetic efficiency almost immediately when exposed to thermal stress, fed corals maintained a constant and high photosynthetic efficiency for 5 more days after onset of thermal stress. We conclude that active feeding is beneficial to corals by prolonging coral health and resilience during thermal stress as a result of an overall healthier symbiont population.

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. The grey reef shark, Carcharhinus amblyrhynchos, is one of the most abundant coral reef sharks throughout the Indo-Pacific. However, this species has been critically impacted across its range, with well-documented population declines of > 90% attributed to human activities. A key knowledge gap in the successful implementation of grey reef shark conservation plans is the understanding of large-scale movement patterns, along with the associated biological and ecological drivers. To address this shortfall, we acoustically monitored 147 adult and juvenile grey reef sharks of all sexes for more than 2 yr across the New Caledonian archipelago, West Pacific. Here, we document multiple adult males undertaking return journeys of up to nearly 700 km in consecutive years. This constitutes the first evidence of repeated long-range migrations for this species. Although only a limited number of adult males were definitively tracked undertaking migrations, similar timing in changes in the detection patterns of a further 13 animals, mostly adult males, suggests this behavior may be more common than previously thought. The paucity of evidence for juvenile migrations and timing of adult movements suggest that mating is the motivation behind these migrations. Our results have important implications for management, given the potential of mature individuals to recurrently travel outside managed or protected areas. Future management of this species clearly needs to consider the importance of large-scale migratory behaviors when developing management plans.

Diarrhetic shellfish toxins produced by certain species of the marine dinoflagellate Dinophysis can accumulate in shellfish in high concentrations, representing a significant food safety issue worldwide. This risk is routinely managed by monitoring programs in shellfish producing areas, however the methods used to detect these harmful marine microbes are not usually automated nor conducted onsite, and are often expensive and require specialized expertise. Here we designed a quantitative real-time polymerase chain reaction (qPCR) assay based on the ITS-5.8S ribosomal region of Dinophysis spp. and evaluated its specificity, efficiency, and sensitivity to detect species belonging to this genus. We designed and tested twenty sets of primers pairs using three species of Dinophysis - D. caudata, D. fortii and D. acuminata. We optimized a qPCR assay using the primer pair that sufficiently amplified each of the target species (Dacu_11F/Dacu_11R), and tested this assay for cross-reactivity with other dinoflagellates and diatoms in the laboratory (11 species) and in silico 8 species (15 strains) of Dinophysis, 3 species of Ornithocercus and 2 species of Phalacroma. The qPCR assay returned efficiencies of 92.4% for D. caudata, 91.3% for D fortii, and 91.5% for D. acuminata, while showing no cross-reactivity with other phytoplankton taxa. Finally, we applied this assay to a D. acuminata bloom which occurred in an oyster producing estuary in south eastern Australia, and compared cell numbers inferred by qPCR to those determined by microscopy counts (max abund. ∼6.3 × 10

In the original online version of this article, there were some errors in the values in Table 7. The original article was corrected.

Carbon sequestration is defined as the secure storage of carbon-containing molecules for >100 years, and in the context of carbon dioxide removal for climate mitigation, the origin of this CO2 is from the atmosphere. On land, trees globally sequester substantial amounts of carbon in woody biomass, and an analogous role for seaweeds in ocean carbon sequestration has been suggested. The purposeful expansion of natural seaweed beds and aquaculture systems, including into the open ocean (ocean afforestation), has been proposed as a method of increasing carbon sequestration and use in carbon trading and offset schemes. However, to verify whether CO2 fixed by seaweeds through photosynthesis leads to carbon sequestration is extremely complex in the marine environment compared to terrestrial systems, because of the need to jointly consider: the comparatively rapid turnover of seaweed biomass, tracing the fate of carbon via particulate and dissolved organic carbon pathways in dynamic coastal waters, and the key role of atmosphere-ocean CO2 exchange. We propose a Forensic Carbon Accounting approach, in which a thorough analysis of carbon flows between the atmosphere and ocean, and into and out of seaweeds would be undertaken, for assessing the magnitude of CO2 removal and robust attribution of carbon sequestration to seaweeds.

Ecosystem metabolism is a key ecological attribute and easy to describe, but quantifying metabolism in estuaries is challenging. Properly scaling measurements through time and space requires consideration of hydrodynamics and mixing water from heterogeneous sources, making any estimation uncertain. Here, we compared three methods for modeling ecosystem metabolism in a portion of the Sacramento-San Joaquin Delta. Metabolism estimates based on laboratory incubations, continuous in situ buoys, and an oxygen isotope approach all indicated the system was net heterotrophic, and calculated rates were comparable in magnitude when averaged over the 2-month study. Daily metabolic rates based on in situ buoys were the most variable, likely due to horizontal and vertical advection and poor portrayal of the dissolved oxygen budget. After temporally averaging in situ buoy estimates or smoothing the dissolved oxygen time series for tidal effects, rates were more comparable to the other methods, which may be necessary to account for tidal advection and unbalanced contributions from subhabitats within the metabolic footprint. Incubation-based rates represent the finest temporal and spatial scale and only account for pelagic processes, which may explain why incubation-based rates were lower than the other two methods. The oxygen isotope method provided temporally and spatially integrated rates that were bracketed by the other two methods and may be a valuable tool in systems matching the model requirements. Because uncertainty arises in each method from a number of assumptions and scaling calculations, the resolution of metabolic rates in estuaries is likely coarser and more variable than in other aquatic ecosystems.

We use Zooglider, a low-power optical zooplankton-sensing glider, to test the covariability of the fine-scale vertical distributions of six omnivorous zooplankton taxa with three different representations of their potential prey field: small suspended particles (equivalent circular diameter [ECD] between 0.25 and 0.45 mm), marine snow (ECD ≥ 0.45 mm), and chlorophyll a (Chl a), in the San Diego Trough. All three prey fields tend to be highly correlated from 100 m to the depth of the subsurface Chl a maximum layer (SCML), while correlations between the prey fields are weaker or nonexistent from the SCML to the surface. An index of spatial overlap (Local Index of Collocation) showed stronger overlap of zooplankton with marine snow or small particles than with Chl a in most cases. Moreover, generalized additive models revealed marine snow distributions or small particles as the primary explanatory variable, by percent deviance explained, for all zooplankton taxa tested. Chl a distributions were a secondary explanatory variable for four of the six taxa tested (small copepods, appendicularia-Fritillaria, and both night and day large copepods), and an insignificant explanatory variable for the remaining two (appendicularia-others and large protists). The distributions of suspended particles, during our year-round study in the San Diego Trough, were more informative for explaining distributions of omnivorous zooplankton than Chl a alone.

Coastal salt marshes are distributed widely across the globe and are considered essential habitat for many fish and crustacean species. Yet, the literature on fishery support by salt marshes has largely been based on a few geographically distinct model systems, and as a result, inadequately captures the hierarchical nature of salt marsh pattern, process, and variation across space and time. A better understanding of geographic variation and drivers of commonalities and differences across salt marsh systems is essential to informing future management practices. Here, we address the key drivers of geographic variation in salt marshes: hydroperiod, seascape configuration, geomorphology, climatic region, sediment supply and riverine input, salinity, vegetation composition, and human activities. Future efforts to manage, conserve, and restore these habitats will require consideration of how environmental drivers within marshes affect the overall structure and subsequent function for fisheries species. We propose a future research agenda that provides both the consistent collection and reporting of sources of variation in small-scale studies and collaborative networks running parallel studies across large scales and geographically distinct locations to provide analogous information for data poor locations. These comparisons are needed to identify and prioritize restoration or conservation efforts, identify sources of variation among regions, and best manage fisheries and food resources across the globe.

Tidal marshes are a key component of coastal seascape mosaics that support a suite of socially and economically valuable ecosystem services, including recreational opportunities (e.g., fishing, birdwatching), habitat for fisheries species, improved water quality, and shoreline protection. The capacity for tidal marshes to support these services is, however, threatened by increasingly widespread human impacts that reduce the extent and condition of tidal marshes across multiple spatial scales and that vary substantially through time. Climate change causes species redistribution at continental scales, changes in weather patterns (e.g., rainfall), and a worsening of the effect of coastal squeeze through sea level rise. Simultaneously, the effects of urbanization such as habitat loss, eutrophication, fishing, and the spread of invasive species interact with each other, and with climate change, to fundamentally change the structure and functioning of tidal marshes and their food webs. These changes affect tidal marshes at local scales through changes in plant community composition, complexity, and condition and at regional scales through changes in habitat extent, configuration, and connectivity. However, research into the full effects of these multi-scaled, interactive stressors on ecosystem service provision in tidal marshes is in its infancy and is somewhat geographically restricted. This hinders our capacity to quickly and effectively curb loss and degradation of both tidal marshes and the services they deliver with targeted management actions. We highlight ten priority research questions seeking to quantify the consequences and scales of human impacts on tidal marshes that should be answered to improve management and restoration plans.

Mechanisms driving the consumption and transport of tidal marsh nutrients and energy by fishes are of key interest in the San Francisco Estuary, CA, USA. By combining multiple data sources (gill-net catches, gut contents, channel morphology, tides), we modeled spatial and temporal patterns of fish abundance and gut fullness across a tidal marsh elevation gradient. Channel depth, microhabitat, and tide were important predictors of fish abundance and gut fullness. Species, feeding guild, and season were also important to fish abundance but not to gut fullness, suggesting that abundance was more related to physical constraints of shallow water than to prey availability. Multiple feeding guilds overlapped in space and time at interaction hotspots in subtidal channel habitat near the marsh entrance. In contrast, fish use of shallow intertidal marsh channels was more variable and indicated tradeoffs between foraging and predation. Gut content analysis revealed moderate-to-high gut fullness for all feeding guilds and models predicted high gut fullness in subtidal reaches duringtidal flooding, after which fish fed intensively throughout the marsh. While mysids, amphipods, and detritus were common prey among feeding guilds, variation in prey consumption was apparent. Overall, complex tidal marsh hydrogeomorphology driving land-water exchange and residence time may diversify and enhance benthic and pelagic food web pathways to fishes and invertebrates. Furthermore, these findings substantiate the notion that dynamic tidal marshes in this system can support robust secondary production, foraging by multiple feeding guilds, and trophic transfer by fishes to the estuarine mosaic.

The IPCC Special Report on Global Warming of 1.5 °C highlights the potential for dietary shifts to reduce greenhouse gas emissions from livestock. Reductions in the consumption of terrestrial animal protein require increases in the consumption of other food categories, to maintain food security, balanced dietary patterns, and protein intake. Aquaculture has long been suggested as one way to meet future food security needs, and marine and estuarine aquaculture in particular is associated with comparatively low greenhouse gas emissions. However, marine and freshwater aquaculture is affected by factors including harmful algal blooms (HABs), which have been increasingly documented around the world, correlated to increases in worldwide aquaculture. In this study, we applied a global multi-region input-output model to capture the direct effects as well as the indirect and induced effects HABs might pose to a global dietary transition from terrestrial livestock to increased seafood consumption from marine and estuarine aquaculture sources. We found that marine and estuarine aquaculture has a substantial potential to replace meat consumption from terrestrial livestock sources, as increases in CO2 emissions from aquaculture were more than offset by reductions in emissions from mainly cattle grazing and associated land clearing. HABs were found to have a minor monetary impact, but the impact on protein supply was found to be potentially sizeable. For example, in a future setting where 40% of terrestrial protein sources were replaced by aquaculture, a HAB-caused global loss of 5% would set in motion numerous supply-chain cascades, affecting industries auxiliary to aquaculture, indirectly and ultimately reducing protein intake by 10–20%. Such reductions have the potential for pushing parts of Sub-Saharan populations into protein-energy malnutrition. Nevertheless, there remains a significant potential for a dietary transition to increased aquaculture seafood to contribute to reductions in GHG.

Micronutrients play key roles in numerous metabolic processes in cyanobacteria. However, our understanding of whether the micronutrient cobalt influences the productivity of freshwater systems or the occurrence of cyanobacterial blooms is limited. This study aimed to quantify the concentration of Co necessary for optimal cyanobacterial growth by exposing Microcystis aeruginosa to a range of Co concentrations under culture conditions. Extended exposure to concentrations below ˜0.06 μg · L-1 resulted in notable inhibition of M. aeruginosa growth. A clear negative relationship was observed between Co concentration in solution and intracellular Fe quota of M. aeruginosa, possibly due to decreased transport of Fe at higher Co concentrations. Cyanocobalamin and any Co within the structure of cyanocobalamin appears to be non-bioavailable to M. aeruginosa, instead they likely rely on the synthesis of a structural variant - pseudocobalamin, which may have implications for the wider algal community as the variants of cobalamin are not necessarily functionally exchangeable. To evaluate the likelihood of Co limitation of cyanobacterial growth under field conditions, a survey of 10 freshwater reservoirs in South-Eastern Australia was conducted. Four of the ten sites had dissolved Co concentrations below the 0.06 μg · L-1 threshold value. All four of these sites rarely undergo cyanobacterial blooms, strengthening evidence of the potential for Co to limit growth, perhaps either alone or in combination with phosphorus.

The aim of the present work was the investigation of various cultivation conditions in order to provide a foundation for a sustainable, financially viable, and environmentally friendly cultivation system for the heterologous β-phellandrene production by Synechocystis sp. PCC 6803. Synechocystis cells were able to grow and form distinct colonies both at the internal and the external surfaces of calcium alginate beads and maintained their ability to produce β-phellandrene, in considerably higher amounts compared to suspension cultures, with maximum production after 6 days. Both immobilized and suspended Synechocystis cells exhibited a continuous and long-term ability to produce β-phellandrene, only by CO2 addition, without renewal of the nutrients or the growth medium. However, photoheterotrophic growth of Synechocystis, with glucose as an alternative carbon source, had a negative impact on the heterologous production β-phellandrene. Despite the fact that cell growth and biomass accumulation were pronounced under photoheterotrophic growth conditions, β-phellandrene production was substantially decreased, indicating that this growth condition is not recommended for scale-up applications. Finally, combination of alkaline (pH 10.5) and saline (600mM NaCl), i.e., extremophilic for Synechocystis growth conditions, proved to be amenable to cell growth and β-phellandrene production, albeit yields were a bit lower. The results provide new approaches for the development of larger scale, environmentally friendly, and financially viable cultivation systems for sustainable heterologous production of terpenoids by Synechocystis.

A variety of cetacean species inhabit the productive waters offshore of Washington State, USA. Although the general presence of many of these species has been documented in this region, our understanding of fine-scale habitat use is limited. Here, passive acoustic monitoring was used to investigate the spatial and temporal distributions of ten cetacean species at three locations offshore of Washington. Between 2004 and 2013, a total of 2845days of recordings were collected from sites on the continental shelf and slope, and in a submarine canyon. Acoustic presence was higher for all species at sites farther offshore. Detections were highest during the fall and winter for blue (Balaenoptera musculus), fin (B. physalus), and humpback whales (Megaptera novaeangliae), likely related to reproductive behavior, while minke whales (B. acutorostrata) were only detected on two days. Odontocetes showed temporal separation, with sperm whale (Physeter macrocephalus) detections highest in spring, Risso’s (Grampus griseus) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) highest in summer, and Stejneger’s beaked whales (Mesoplodon stejnegeri), Cuvier’s beaked whales (Ziphius cavirostris), and the BW37V signal type highest in winter or spring. There was interannual variation in detections for most mysticete species, which may be linked to oceanographic conditions: blue and fin whale detections increased during 2007 and 2008, and fin and humpback whale detections increased in 2011. These results inform our understanding of cetacean behavior and habitat use in this region and may aid in the development of conservation strategies suited to the dynamic conditions that drive cetacean distribution.

Ichthyoplankton studies can be used to assess the abundance, distribution, and reproductive activity of marine fishes, but few studies have monitored spawning activity at inshore sites. This study utilized weekly plankton sampling to construct a year-long time series of fish spawning at 6 pier sites along the California coast—Santa Cruz, San Luis Obispo, Santa Barbara, Santa Monica, Newport Beach, and La Jolla; sampling at the La Jolla site continues ongoing monitoring initiated in 2012. Fish eggs were sorted from the collected plankton and identified to species level using DNA barcoding of the COI and 16S genes. While only one year of data has been collected from 5 of the sites, the 2 sites north of Point Conception show markedly reduced diversity compared to the southern sites. Although the species observed reflect the local environment of each site, this pattern of reduced diversity at the northern sites is consistent with the well-documented decline in species richness with latitude along the California coast. The 7-year time series from La Jolla has revealed that spawning activity varies greatly among years, both in terms of egg production and species diversity, with a continuing trend of highest egg numbers in years with colder average winter sea surface temperature.

Ichthyoplankton studies can be used to assess the abundance, distribution, and reproductive activity of marine fishes, but few studies have monitored spawning activity at inshore sites. This study utilized weekly plankton sampling to construct a year-long time series of fish spawning at 6 pier sites along the California coast—Santa Cruz, San Luis Obispo, Santa Barbara, Santa Monica, Newport Beach, and La Jolla; sampling at the La Jolla site continues ongoing monitoring initiated in 2012. Fish eggs were sorted from the collected plankton and identified to species level using DNA barcoding of the COI and 16S genes. While only one year of data has been collected from 5 of the sites, the 2 sites north of Point Conception show markedly reduced diversity compared to the southern sites. Although the species observed reflect the local environment of each site, this pattern of reduced diversity at the northern sites is consistent with the well-documented decline in species richness with latitude along the California coast. The 7-year time series from La Jolla has revealed that spawning activity varies greatly among years, both in terms of egg production and species diversity, with a continuing trend of highest egg numbers in years with colder average winter sea surface temperature.

Loss of estuarine and coastal habitats worldwide has reduced nursery habitat and function for diverse fishes, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Underutilized off-channel habitats such as flooded rice fields and managed ponds present opportunities for improving rearing conditions and increasing habitat diversity along migratory corridors. While experiments in rice fields have shown enhanced growth rates of juvenile fishes, managed ponds are less studied. To evaluate the potential of these ponds as a nursery habitat, juvenile Chinook salmon (~ 2.8 g, 63 mm FL) were reared in cages in four contrasting locations within Suisun Marsh, a large wetland in the San Francisco Estuary. The locations included a natural tidal slough, a leveed tidal slough, and the inlet and outlet of a tidally muted managed pond established for waterfowl hunting. Fish growth rates differed significantly among locations, with the fastest growth occurring near the outlet in the managed pond. High zooplankton biomass at the managed pond outlet was the best correlate of salmon growth. Water temperatures in the managed pond were also cooler and less variable compared to sloughs, reducing thermal stress. The stress of low dissolved oxygen concentrations within the managed pond was likely mediated by high concentrations of zooplankton and favorable temperatures. Our findings suggest that muted tidal habitats in the San Francisco Estuary and elsewhere could be managed to promote growth and survival of juvenile salmon and other native fishes.

This paper presents the development and testing of a gamma radiation dose rate calculation model for the marine environment, and evaluates the potential use for such a model in both short term nuclear emergency response management and emergency response planning. This is believed to be the first implementation of a full field gamma radiation mapping model (including air attenuation and buildup) to be incorporated within a Lagrangian marine dispersion model. Calculated surface gamma ray dose rates for nine generic release scenarios are presented and used to undertake an emergency countermeasure optioneering assessment.