Small metazoans, especially harpacticoid copepods, are an important component in the benthic food webs of benthic environments. However, studies on the effects of elevated CO2 and temperature on these animals are scarce and those that do exist focus mainly on the individual species level. A laboratory experiment was conducted to evaluate the impact of different climate change scenarios on a community of harpacticoid copepods from a coral reef environment. Samples were collected from the coral reef subtidal zone of Serrambi beach (Ipojuca, Pernambuco, Brazil), using colonized artificial substrate units. The units were exposed to control treatments and to three climate change scenarios and were collected after 14 and 29 days. A highly diverse community of harpacticoids was analyzed [H′(log2) = 4.37]. Changes in the community structure were observed, and the response of the copepod community structure to the different scenarios varied according to the sampling period. The maintenance of a highly diverse community enabled a complex pattern of responses to be observed at a species level with three different response patterns to the changing seawater conditions: sensitive species represented by Tisbe sp., Stenhelia sp. and Ameira sp.; mildly sensitive represented by Cyclopoida and Dactylopusia sp.; resistant or opportunist represented by Ectinosoma sp.1, Ectinosoma sp.2 and Mesochra sp. The increase in malformed adult animals in the most severe scenario indicated that species that do not suffer mortality are not exempt from sublethal symptoms. Harpacticoid organisms are shown as reliable tools to assess climate change in coral reef environments.
Continue reading ‘Future climate change scenarios of increased CO2 and temperature strongly affect a coral reef meiobenthic harpacticoid (Crustacea) community’Posts Tagged 'zooplankton'
Future climate change scenarios of increased CO2 and temperature strongly affect a coral reef meiobenthic harpacticoid (Crustacea) community
Published 15 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, crustaceans, laboratory, morphology, mortality, multiple factors, otherprocess, South Atlantic, temperature, zooplankton
Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities
Published 10 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, otherprocess, photosynthesis, phytoplankton, protists, South Atlantic, zooplankton
Highlights
- Multi-interacting driver effects were evaluated on South Atlantic estuarine plankton
- Warming×pH×nutrients×UVR reduced the photosynthetic and resource use efficiencies
- A multi-driver change condition prompted a microzooplankton-phytoplankton uncoupling
- Altered trophic interactions could reduce the energy transfer efficiency in food webs
Abstract
Plankton communities are subjected to multiple global change drivers; however, it is unknown how the interplay between them deviates from predictions based on single-driver studies, in particular when trophic interactions are explicitly considered. We investigated how simultaneous manipulation of temperature, pH, nutrient availability and solar radiation quality affects the carbon transfer from phytoplankton to herbivorous protists and their potential consequences for ecosystem functioning. Our results showed that multiple interacting global-change drivers reduced the photosynthetic (gross primary production-to-electron transport rates ratios, from 0.2 to 0.6-0.8) and resource use efficiencies (from 9 to 1 μg chlorophyll a (Chl a) μmol nitrogen-1) and prompted uncoupling between microzooplankton grazing (m) and phytoplankton growth (μ) rates (μ > m). The altered trophic interaction could be due to enhanced intra-guild predation or to microzooplankton growing at suboptimal temperatures compared to their prey. Because phytoplankton-specific loss rates to consumers grazing are the most significant uncertainty in marine biogeochemical models, we stress the need for experimental approaches quantifying it accurately to avoid bias in predicting the impacts of global change on marine ecosystems.
Continue reading ‘Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities’Microplastic hotspots mapped across the Southern Ocean reveal areas of potential ecological impact
Published 9 January 2025 Science ClosedTags: Antarctic, biological response, chemistry, crustaceans, phytoplankton, review, zooplankton
Marine microplastic is pervasive, polluting the remotest ecosystems including the Southern Ocean. Since this region is already undergoing climatic changes, the additional stress of microplastic pollution on the ecosystem should not be considered in isolation. We identify potential hotspot areas of ecological impact from a spatial overlap analysis of multiple data sets to understand where marine biota are likely to interact with local microplastic emissions (from ship traffic and human populations associated with scientific research and tourism). Then we account for cumulative effects by identifying which areas with potential elevated microplastic-biota interaction are already subject to climate change related stresses (ocean warming and acidification). Our analysis indicates that biologically productive coastal areas in proximity to populated facilities are where microplastics pose most risk to the ecosystem, and that the northern Antarctic Peninsula is likely to be the main risk hotspot. This study is the first to map the threat of microplastics to the Southern Ocean ecosystem in a multi-stressor context, locating where microplastic monitoring programmes and mitigation measures may be considered a matter of urgency.
Continue reading ‘Microplastic hotspots mapped across the Southern Ocean reveal areas of potential ecological impact’Toxicity of PAHs-enriched sediments on meiobenthic communities under ocean warming and CO2-driven acidification scenarios
Published 6 January 2025 Science ClosedTags: annelids, biological response, BRcommunity, community composition, crustaceans, laboratory, mollusks, multiple factors, nematodes, otherprocess, platyhelminthes, sediment, South Atlantic, tardigrada, temperature, toxicants, zooplankton
Highlights
- Temperature rise reduced the densities of Copepoda and certain Nematoda groups.
- CO2 acidification prevented some Nematoda groups from increasing at high temperatures.
- CO2 acidification reduced Copepoda and nauplii densities, but increased Ostracoda.
- Complex interactions increased certain meiobenthic groups exposed to sediment PAHs.
- Global change and pollution showed interactive effects in meiobenthic communities.
Abstract
This study aimed to assess the interactive effects of CO2-driven acidification, temperature rise, and PAHs toxicity on meiobenthic communities. Laboratory microcosms were established in a full factorial experimental design, manipulating temperature (25 °C and 27 °C), pH (8.1 and 7.6), and PAH contamination (acenaphthene + benzo(a)pyrene spiked sediments and negative control). Temperature rise and CO2-driven acidification led to a decrease in the densities of Copepoda. The density of nematodes Pseudochromadora and Daptonema also decreased, while Sphaerotheristus and Sabatieria densities increased, particularly in the absence of CO2-driven acidification. Ostracoda densities increased in the acidified scenario. PAH contamination resulted in decreased Daptonema densities but increased Turbellaria and certain Nematoda genera (e.g. Pseudochromadora). Overall, the results indicate that the changes of meiobenthic communities caused by CO2 acidification, warming, and PAH contamination are shaped by the vulnerability and tolerance of each taxonomic group, alongside indirect effects observed in Nematoda assemblages.
Continue reading ‘Toxicity of PAHs-enriched sediments on meiobenthic communities under ocean warming and CO2-driven acidification scenarios’Temperature, pH, and diet interactively affect biosynthesis of polyunsaturated fatty acids in a benthic harpacticoid copepod
Published 3 January 2025 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, physiology, temperature, zooplankton
Greenhouse gas emissions lead to ocean warming and acidification, negatively impacting marine organisms and their functioning, including long-chain polyunsaturated fatty acid (LC-PUFA) production by marine microalgae. Copepods, primary consumers of microalgae, possess a unique capacity for endogenous LC-PUFA biosynthesis, possibly enabling them to cope with reduced dietary LC-PUFA availabilities. However, this capacity may be itself impacted by changing oceanographic conditions. In this study, we conducted a laboratory experiment to evaluate the combined effects of warming (+3°C), acidification (−0.4 pH), and dietary LC-PUFA deficiency on the fatty acid composition and LC-PUFA biosynthesis (measured by quantitative RT-PCR) of the benthic harpacticoid copepod Platychelipus littoralis (Brady, 1880). We hypothesized increased LC-PUFA biosynthesis under all drivers compensating for LC-PUFA reductions. Lipid profiles of copepods exposed to multiple stressors contained shorter-chained and more saturated fatty acids. While copepods maintained base-line relative concentrations of the physiologically important LC-PUFA docosahexaenoic acid (DHA) on an LC-PUFA deficient diet at ambient temperatures, DHA concentrations decreased significantly with higher temperatures. Expression of the DHA biosynthesis genes Δ4 front-end desaturase and elovl1a increased under dietary LC-PUFA deficiency but did not exceed base-line levels when simultaneously exposed to acidification. Expression of Δ4 front-end desaturase and multiple elongases correlated positively with C18 precursor concentrations and negatively with those of LC-PUFAs such as DHA, indicating their role as LC-PUFA biosynthesis enzymes. Overall, our findings suggest that ocean warming and acidification may impede benthic copepods’ LC-PUFA biosynthesis capacity under reduced dietary inputs, limiting their contribution toward global LC-PUFA availability for higher trophic levels.
Continue reading ‘Temperature, pH, and diet interactively affect biosynthesis of polyunsaturated fatty acids in a benthic harpacticoid copepod’Local effects of Sargassum beds on the seawater carbonate system and plankton community
Published 30 December 2024 Science ClosedTags: biological response, BRcommunity, chemistry, crustaceans, field, mitigation, North Pacific, phanerogams, phytoplankton, zooplankton
Highlights
- The ecological effect of the sargassum beds depends on seaweed biomass.
- The biomass of the sargassum beds in Weizhou Island reached its peak in spring.
- Sargassum beds significantly influenced the carbonate system and DOC pool in spring.
- Sargassum beds is more likely to alter phytoplankton communities than zooplankton.
Abstract
Sargassum beds are recognized as important habitats for fostering species diversity and capturing blue carbon, exerting significant influence on seawater chemistry and planktonic communities. However, there is still much to uncover about the interactions between these biogenic habitats and seawater chemistry, as well as their impact on plankton communities in the water column. To address this gap, we conducted a study on the functions of natural Sargassum beds in various seasons around the northern part of Weizhou Island in the South China Sea. Our research involved quantifying carbonate chemistry, carbon stock potential, and seawater plankton communities in two distinct areas: the core area in the interior regions of the seaweed beds and the non-core areas at its periphery or external. Our findings revealed an estimated 3.7 km2 of benthic Sargassum, with an overall biomass of 21.2 Gg km−2, reaching its peak productivity in spring, equivalent to 1.14 Pg C km−2. Notably, during spring, the seaweed beds significantly influenced the exchange of CO2 at the air-sea interface, leading to reduced pCO2 (41 μatm) in the core area compared to the non-core area (p < 0.05), thus enhancing the local carbon sequestration capacity. Additionally, we observed significant regional differences in the concentration of dissolved organic carbon (DOC) only during the spring season, indicating the capacity of Sargassum to alter the DOC pool around its habitat. We anticipate that seaweed deposition will become a more frequent occurrence towards the end of the growth period, with increasing fragments facilitating a transition towards phytoplankton-dominated marine ecosystems. Furthermore, the fixation of extra CO2 by seaweed may lead to a pH increase, providing a refuge for copepods from ocean acidification. In summary, our observations suggest that the Sargassum beds plays a substantial role in nearshore carbon cycling and ecological impact, surpassing previous documentation.
Continue reading ‘Local effects of Sargassum beds on the seawater carbonate system and plankton community’A regional physical-biogeochemical ocean model for marine resource applications in the Northeast Pacific (MOM6-COBALT-NEP10k v1.0)
Published 25 December 2024 Science ClosedTags: Arctic, biogeochemistry, biological response, field, modeling, North Pacific, regionalmodeling, zooplankton
Regional ocean models enable generation of computationally-affordable and regionally-tailored \ ensembles of near-term forecasts and long-term projections of sufficient resolution to serve marine resource management. Climate change, however, has created marine resource challenges, such as shifting stock distributions, that cut across domestic and international management boundaries and have pushed regional modeling efforts toward “coastwide” approaches. Here we present and evaluate a multidecadal hindcast with a Northeast Pacific (NEP) regional implementation of the Modular Ocean Model version 6 with sea ice and biogeochemistry that extends from the Chukchi Sea to the Baja California Peninsula at 10-km horizontal resolution (MOM6-COBALT-NEP10k, or “NEP10k”). This domain includes an Arctic-adjacent system with a broad shallow shelf seasonally covered by sea ice (the Eastern Bering Sea, EBS), a sub-Arctic system with upwelling in the Alaska Gyre and predominant downwelling winds and large freshwater forcing along the coast (the Gulf of Alaska, GoA), and a temperate, eastern boundary upwelling ecosystem (the California Current Ecosystem, CCE). The coastwide model was able to recreate seasonal and cross-ecosystem contrasts in numerous ecosystem-critical properties including temperature, salinity, inorganic nutrients, oxygen, carbonate saturation states, and chlorophyll. Spatial consistency between modeled quantities and observations generally extended to plankton ecosystems, though small to moderate biases were also apparent. Fidelity with observed zooplankton biomass, for example, was limited to first-order seasonal and cross-system contrasts. Temporally, simulated monthly surface and bottom temperature anomalies in coastal regions (< 500m deep) closely matched estimates from data-assimilative ocean reanalyses. Performance, however, was reduced in some nearshore regions coarsely resolved by the model’s 10-km resolution grid, and the time series of satellite-based chlorophyll anomaly estimates proved more difficult to match than temperature. System-specific ecosystem indicators were also assessed. In the EBS, NEP10k robustly matched observed variations, including recent large declines, in the area of the summer bottom water “cold pool” (< 2 °C) which exerts a profound influence on EBS fisheries. In the GoA, the simulation captured patterns of sea surface height variability and variations in thermal, oxygen and acidification risk associated with local modes of inter-annual to decadal climate variability. In the CCE, the simulation robustly captured variations in upwelling indices and coastal water masses, though discrepancies in the latter were evident in the Southern California Bight. Enhanced model resolution may reduce such discrepancies, but any benefits must be carefully weighed against computational costs given the intended use of this system for ensemble predictions and projections. Meanwhile, the demonstrated NEP10k skill level herein, particularly in recreating cross-ecosystem contrasts and the time variation of ecosystem indicators over multiple decades, suggests considerable immediate utility for coastwide retrospective and predictive applications.
Continue reading ‘A regional physical-biogeochemical ocean model for marine resource applications in the Northeast Pacific (MOM6-COBALT-NEP10k v1.0)’Sensitivity of pteropod calcification to multi stressor variability in coastal habitats
Published 18 December 2024 Science , Uncategorized ClosedTags: biological response, field, modeling, mollusks, morphology, multiple factors, North Pacific, regionalmodeling, temperature, zooplankton
Highlights
- Pteropod calcification under coastal multiple stressors was investigated.
- Shell morphometrics and high-resolution model outputs was combined.
- Saturation state, temperature and food are drivers of calcification.
- Different calcification modes are dependent on the type of environment.
- Stable vs dynamic conditions induce different calcification strategy.
Abstract
Comprehensive understanding of environmental multiple stressors on calcification in marine calcifiers remains an important topic of study, especially under ocean global change associated with multiple stressors. We explore the impact of multiple stressor variability on pteropod calcification in the southern Salish Sea (Washington, U.S.), a coastal estuarine system that exhibits a high degree of spatial and temporal variability in multiple environmental parameters across sampling locations. We hypothesized that such variability is associated with differences in pteropod calcification. Shell thickness and shell density across pteropod life history stages was compared with high-resolution outputs from a realistic model of regional circulation and biogeochemistry to explore how the mean and variability of multiple stressors (aragonite saturation state (Ωar), temperature, food availability) influence calcification. We found that both the mean and variability in multiple stressors play a major role in calcification in pteropods, with a generalized linear model explaining more than 60% of the variance in calcification. We suggest two different modes of shell building: stable conditions of lower mean Ωar trigger the loss of shell thickness and density. In the more variable habitats, i.e., where the variability occurs over diel and seasonal scales, shell thickness increases at higher Ωar variability and greater food availability, which might partially compensate for the loss of shell density. This plastic response appears to be consistent across life stages and could represent a response mechanism that allows some compensatory calcification under less favourable conditions. However, compensation is very limited, as evident by lower shell growth resulting in lower shell sizes comparable to early life stages. These results substantially improve the understanding of the variability in multiple stressors on the calcification process under multiple stressors and provide a foundation for the development of two new proxies for calcification monitoring, and with implications for marine carbon dioxide removal strategies.
Continue reading ‘Sensitivity of pteropod calcification to multi stressor variability in coastal habitats’Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities
Published 16 December 2024 Science ClosedTags: biological response, chemistry, community composition, field, North Pacific, otherprocess, phytoplankton, zooplankton
Highlights
- Untreated effluent caused decreases in seawater pH from 8.1 to lower than 7.5.
- Decreases in pH led to nonlinearly declined abundance of all plankton groups.
- Plankton abundance recovered as pH bounced back to normal levels.
- Negative impacts of decreases in pH on the marine planktons were reversible.
Abstract
An event of releasing untreated effluent caused serious decreases in surface seawater pH from 8.1 to lower than 7.5 in seven years and increased back to prior levels after 15 years. It gives us a rare natural experiment to examine the impacts of decreases in pH on the marine plankton communities (phytoplanktons, zooplanktons, shrimp larvae, crab larvae, fish eggs, and larvae) in the natural environment. Observed decreases in pH had a nonlinear effect ubiquitous on all plankton groups, leading to a reduction of approximately 50 % in their density and abundance compared to the level at pH 8.1. Non-linear responses of planktons implied the existence of specific groups more robust to decreases in pH. As pH bounced back to normal levels, the density and abundance of the plankton communities also recovered, further indicating that the negative impacts of decreases in pH on the marine plankton communities were reversible.
Continue reading ‘Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities’Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years
Published 24 September 2024 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, corals, laboratory, mortality, multiple factors, North Pacific, nutrients, otherprocess, physiology, protists, zooplankton
Under predicted future ocean conditions, corals will experience frequent and intense thermal stress events while simultaneously being exposed to chronic ocean acidification. Yet, some corals will likely be more resistant and/or resilient to these predicted conditions than others and may be critical to reef persistence in the future. Following natural thermal stress in two consecutive years (2014 and 2015), we evaluated the effects of feeding and simulated ocean acidification on the physiological recovery of Montipora capitata and Porites compressa sourced from Kāneʻohe Bay and Waimānalo Bay, Hawaiʻi. Following the 2014 thermal stress event, simulated ocean acidification did not slow recovery of the holobiont and feeding enhanced recovery. However, feeding did not decrease susceptibility to the 2015 thermal stress event, and simulated ocean acidification did not increase susceptibility. Recovery strategies employed between species and between sites clearly differed, highlighting that coral reef restoration and management should consider species-level and site-specific vulnerabilities. Overall, our findings call attention to the immediate threat which ocean warming presents, the lack of additional stress to the holobiont from ocean acidification, the importance of heterotrophy in coral resilience, and the potential significance of additional local biotic stressors (i.e., predator outbreaks) for coral resiliency under annual thermal stress.
Continue reading ‘Ocean acidification does not prolong recovery of coral holobionts from natural thermal stress in two consecutive years’Species sensitivity distributions: understanding ocean acidification’s impact on marine biota
Published 30 July 2024 Science ClosedTags: biological response, cnidaria, crustaceans, echinoderms, fish, mollusks, phytoplankton, review, zooplankton
This research paper investigates the repercussions of ocean acidification on marine ecosystems, focusing on the sensitivity of diverse taxa to changing pH stages. Drawing from recent research, we discover the complicated interaction among climate change, contaminant accumulation, and atmosphere dynamics, with a particular emphasis on coastal regions reliant on fisheries. Through a complete assessment, we recognize substantial differences in sensitivity amongst calcifying taxa, highlighting the implications for each polar and temperate/tropical region. Furthermore, we propose tailored management techniques relying on distinct climate zones and taxonomic groups to mitigate the destructive effects of ocean acidification. Our sensitivity analyses monitoring of capability shifts in Species Sensitivity Distributions (SSDs) under preindustrial pH situations, underscoring the importance of historic baselines in predicting future influences. This paper contributes to our understanding of how ocean acidification threatens marine biodiversity and underscores the urgency of implementing efficient conservation measures.
Continue reading ‘Species sensitivity distributions: understanding ocean acidification’s impact on marine biota’From nutrients to fish: impacts of mesoscale processes in a global CESM-FEISTY eddying ocean model framework
Published 26 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, fish, globalmodeling, modeling, otherprocess, phytoplankton, review, zooplankton
The ocean sustains ecosystems that are essential for human livelihood and habitability of the planet. The ocean holds an enormous amount of carbon, and serves as a critical source of nutrition for human societies worldwide. Climate variability and change impacts marine biogeochemistry and ecosystems. Thus, having state-of-the-art simulations of the ocean, which include marine biogeochemistry and ecosystems, is critical for understanding the role of climate variability and change on the ocean biosphere. Here we present a novel global eddy-resolving (0.1° horizontal resolution) simulation of the ocean and sea ice, including ocean biogeochemistry, performed with the Community Earth System Model (CESM). The simulation is forced by the atmospheric dataset based on the Japanese Reanalysis (JRA-55) product over the 1958 – 2021 period. We present a novel configuration of the CESM marine ecosystem model in this simulation which includes two zooplankton classes: microzooplankton and mesozooplankton. This novel planktonic food web structure facilitates “offline” coupling with the Fisheries Size and Functional Type (FEISTY) model. FEISTY is a size- and trait-based model of fish functional types contributing to fisheries. We present an evaluation of the ocean biogeochemistry, marine ecosystem (including fish types), and sea ice in this high-resolution simulation compared to available observations and a corresponding low resolution (nominal 1°) simulation. Our analysis offers insights into environmental controls on trophodynamics within the ocean. We find that this high resolution simulation provides a realistic reconstruction of nutrients, oxygen, sea ice, plankton and fish distributions over the global ocean. On global and large regional scales the high-resolution simulation is comparable to the standard 1° simulation, but on smaller scales, explicitly resolving the mesoscale dynamics is shown to be important for accurately capturing trophodynamic structuring, especially in coastal ecosystems. We show that fine scale ocean features leave imprints on ocean ecosystems, from plankton to fish, from the tropics to polar regions. This simulation also offers insights on ocean acidification over the past 64 years, as well as how large scale climate variations may impact upper trophic levels. The data generated by the simulations are publicly available and will be a fruitful community resource for a large variety of oceanographic science questions.
Continue reading ‘From nutrients to fish: impacts of mesoscale processes in a global CESM-FEISTY eddying ocean model framework’Impact of ocean acidification on microzooplankton grazing dynamics
Published 28 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, laboratory, North Pacific, otherprocess, performance, phytoplankton, zooplankton
This study examines the potential impacts of projected atmospheric carbon dioxide (pCO2) levels reaching 800 ppm by the end of the century, focusing on ocean acidification effects on marine ecosystems in the coastal areas of Bohai. We investigated how acidification affects the grazing patterns of microzooplankton using dilution techniques and ecophysiological methods. Our findings indicate that acidic conditions shift the phytoplankton community structure, changing dominant species. Elevated CO2 concentrations reduced grazing pressure on phytoplankton, with less steep declines in growth rates at 800 ppm CO2 (spring: 2.43 d−1 vs. 2.16 d−1, summer: −0.46 d−1 vs. −0.73 d−1, autumn: −0.45 d−1 vs. −0.90 d−1) and significant decreases in grazing pressure percentages (%Pp from 0.84 to 0.58 and %Pi from 0.64 to 0.46). Short-term acid exposure significantly increased superoxide dismutase activity in both microplankton (from 0.03 to 0.08 U mg−1, p<0.01) and nanoplankton (from 0.05 to 0.09 U mg−1, p<0.001), indicating an adaptive response to oxidative stress. These results highlight that elevated CO2 levels primarily boost phytoplankton growth by reducing microzooplankton grazing pressure, resulting in higher growth rates and a shift towards smaller-sized phytoplankton, reflecting complex short-term ecological responses to acidification. Further research is needed to understand the long-term effects of ocean acidification on microzooplankton and their role in marine secondary productivity.
Continue reading ‘Impact of ocean acidification on microzooplankton grazing dynamics’Mortality of mesozooplankton in an acidified ocean: investigating the impact of shallow hydrothermal vents across multiple monsoonal periods
Published 19 June 2024 Science ClosedTags: biological response, chemistry, laboratory, mortality, North Pacific, vents, zooplankton
Highlights
- Hydrothermal vents exert different mortalities on different mesozooplankton taxa.
- Low pH significantly increases mesozooplankton mortality.
- Lethal mesozooplankton effects decrease with increasing distance from hydrothermal vents.
- Mesozooplankton mortalities differ with monsoonal periods.
Abstract
The shallow hydrothermal vents (HVs) of Kueishan Island are considered as a template for studying the extremes of sulfide-polluted and acidified water. The present study examined the biological and spatiotemporal aspects of mesozooplankton mortality in waters around this extreme HV environment. Zooplankton sample collection was carried out in three monsoonal periods and the results revealed that there was a significant decrease in the mortality of total mesozooplankton with increasing distance from the HVs. The overall mortality of mesozooplankton showed a significant negative correlation with sea surface temperature and pH. Particularly, mortality of copepods showed a significant negative correlation with pH, whereas it was significantly positive correlated with sea surface temperature in the southwest monsoon prevailing period. Overall, the results may imply a situation that zooplankton will encounter in the more acidified environment of a future ocean.
Continue reading ‘Mortality of mesozooplankton in an acidified ocean: investigating the impact of shallow hydrothermal vents across multiple monsoonal periods’Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm
Published 4 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, mesocosms, otherprocess, photosynthesis, phytoplankton, prokaryotes, zooplankton
Highlights
- The communities were strongly affected by phytoplankton bloom stages.
- Ocean acidification (OA) affected some taxa as the phytoplankton bloom stages progressed.
- OA changed the co-occurrence network complexity and stability of microeukaryotes.
- OA altered the proportions of potential interactions between phytoplankton and their predators.
Abstract
Ocean acidification (OA) is known to influence biological and ecological processes, mainly focusing on its impacts on single species, but little has been documented on how OA may alter plankton community interactions. Here, we conducted a mesocosm experiment with ambient (∼410 ppmv) and high (1000 ppmv) CO2 concentrations in a subtropical eutrophic region of the East China Sea and examined the community dynamics of microeukaryotes, bacterioplankton and microeukaryote-attached bacteria in the enclosed coastal seawater. The OA treatment with elevated CO2 affected taxa as the phytoplankton bloom stages progressed, with a 72.89% decrease in relative abundance of the protist Cercozoa on day 10 and a 322% increase in relative abundance of Stramenopile dominated by diatoms, accompanied by a 29.54% decrease in relative abundance of attached Alphaproteobacteria on day 28. Our study revealed that protozoans with different prey preferences had differing sensitivity to high CO2, and attached bacteria were more significantly affected by high CO2 compared to bacterioplankton. Our findings indicate that high CO2 changed the co-occurrence network complexity and stability of microeukaryotes more than those of bacteria. Furthermore, high CO2 was found to alter the proportions of potential interactions between phytoplankton and their predators, as well as microeukaryotes and their attached bacteria in the networks. The changes in the relative abundances and interactions of microeukaryotes between their predators in response to high CO2 revealed in our study suggest that high CO2 may have profound impacts on marine food webs.
Continue reading ‘Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm’Ocean acidification and food availability impacts on the metabolism and grazing in a cosmopolitan herbivorous protist Oxyrrhis marina
Published 8 March 2024 Science ClosedTags: abundance, biological response, growth, laboratory, multiple factors, North Pacific, nutrients, otherprocess, performance, physiology, primary production, protists, respiration, zooplankton
The heterotrophic dinoflagellate Oxyrrhis marina is an essential microzooplankton in coastal waters, linking the energy transfer from phytoplankton to higher trophic levels. It is of general significance to investigate how it responds and acclimates to ocean acidification (OA), especially under varied availabilities of food. Here, O. marina was exposed and acclimated to three pCO2 levels (LC: 415, MC:1000, HC:1500 μatm) for 60 days, and then was further grown under the CO2 levels with different levels of food (the microalgae Dunaliella salina) availability for about 8 generations. The OA treatments did not significantly hamper its growth and ingestion rates even under the reduced food availability and starvation (deprived of the microalgae), which significantly reduced its growth rate. While the impacts of OA on the growth and ingestion rates of O. marina were insignificant, the OA treatments appeared to have resulted in a faster decline of the heterotrophic dinoflagellate cells during the starvation period. Nevertheless, the acidic stress under the elevated pCO2 of 1000 or 1500 μatm decreased its respiration by about 53% or 59% with the high and by about 26% or 23% with the low food availability, respectively. Such OA-repressed respiration was also significant during the starvation period. On the other hand, the OA treatments and deprivation of the microalgae synergistically reduced the cellular quota of particulate organic C, N and P, resulting in a reduction of food value of the heterotrophic dinoflagellate as prey. In conclusion, our results show that O. marina is highly resilient to future ocean acidification by reducing its respiration and sustaining its ingestion of microalgae.
Continue reading ‘Ocean acidification and food availability impacts on the metabolism and grazing in a cosmopolitan herbivorous protist Oxyrrhis marina’A global biogeography analysis reveals vulnerability of surface marine zooplankton to anthropogenic stressors
Published 16 January 2024 Science ClosedTags: abundance, biological response, globalmodeling, modeling, otherprocess, performance, zooplankton
Highlights
- Multiple stress factors for zooplankton overlap in the surface ocean
- Stress brought by surface warming and acidification strongly increased in ∼50 years
- More research on anthropogenic impacts on zooplankton is urgently needed
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Summary
Anthropogenic impacts on zooplankton at the surface ocean pose an urgent challenge because these keystone species are crucial for oceanic processes. Some anthropogenic stressors for zooplankton have been identified, such as acidification due to climate change, but a multitude of other stressors exist, and the combination of these may lead to unknown impacts. We utilized global biogeochemical models to assess the temporal and spatial distribution of zooplankton stress factors, including changes in sea surface temperature, acidification, prey quantity, food quality, and contaminants. We highlighted regional hotspots where multiple stress factors overlap and revealed that most stress factors are increasing. By linking stress factors to zooplankton distribution, we introduced a zooplankton vulnerability index. We found that the zooplankton vulnerability index has doubled in 50 years, and this suggests that zooplankton populations are increasingly at risk from anthropogenic stressors. Further research is needed to develop strategies for mitigating the impacts of anthropogenic stressors on zooplankton.
Continue reading ‘A global biogeography analysis reveals vulnerability of surface marine zooplankton to anthropogenic stressors’Short-term impact assessment of ocean liming: a copepod exposure test
Published 19 December 2023 Science ClosedTags: biological response, crustaceans, laboratory, mitigation, mortality, North Atlantic, performance, zooplankton
Highlights
- Ocean liming (OL) may cause temporary pH peaks which can be dangerous for marine life.
- Short-term exposure tests (<24 h) are required to evaluate the impact of OL.
- At pH 9 for exposures lower than 6 h, copepods showed no adverse effects.
- At pH ≥ 10, adverse effects on copepods were seen for exposures shorter than 3 h.
Abstract
Ocean liming (OL) is a potential carbon dioxide removal (CDR) method that aims to increase the ocean’s capacity to absorb atmospheric CO2 by adding hydrated lime to the surface ocean. Modeling studies indicate that OL may cause temporary pH spikes lasting several minutes, depending on the lime sparging rate. Little is known about the short-term effects of these spikes on marine organisms. Aim of the present study is to investigate these effects on the copepod Acartia tonsa. Copepods were exposed to different pH conditions (9, 10, 11, 12) by dosing different hydrated lime solutions. Copepod mortality, movements, and behavior were recorded. At pH 9 for short exposure times (<6 h), no negative effects were observed indicating a potential tolerable threshold for OL applications. At longer exposure times (>6 h) and pH higher than 9, negative effects (mortality and sublethal effects) were found significantly higher than in the control.
Continue reading ‘Short-term impact assessment of ocean liming: a copepod exposure test’The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean
Published 18 December 2023 Science ClosedTags: abundance, biogeochemistry, biological response, field, mesocosms, North Pacific, otherprocess, performance, phytoplankton, primary production, reproduction, zooplankton
Gelatinous zooplankton are increasingly recognized to play a key role in the ocean’s biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.
Continue reading ‘The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean’
