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)’Posts Tagged 'zooplankton'
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
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
…
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’The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean
Published 22 November 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, chemistry, communitymodeling, field, mesocosms, modeling, morphology, North Atlantic, otherprocess, photosynthesis, phytoplankton, 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’Global synthesis of the status and trends of ocean acidification impacts on shelled pteropods
Published 13 November 2023 Science ClosedTags: Antarctic, Arctic, biological response, chemistry, mollusks, morphology, North Pacific, physiology, zooplankton
The accumulation of anthropogenic CO₂ in the ocean has major ecological, socioeconomic, and biogeochemical impacts, with repercussions for the ocean as a critical carbon sink. Ocean acidification (OA) disproportionately affects marine calcifiers, among which pelagic zooplanktonic pteropods play a significant role in carbonate export. The pteropod, due to the susceptibility of its aragonite shell to rapid dissolution, is one of most vulnerable groups and a key indicator for OA regional monitoring, but its regional sensitivities have not yet been extrapolated over global scales. To delineate spatial and temporal changes in pteropod shell dissolution, global OA status and the OA rate of change were evaluated, based on gridded climatologies of observations and using a Regional Ocean Modeling System (ROMS) biogeochemical/ecosystem model. Pteropods, which dominate in the polar and subpolar regions, are characterized by low aragonite saturation state and low buffering capacity, where extended pteropod subsurface dissolution is projected. We show that pteropods are most susceptible to OA in the polar regions, subpolar North Pacific, and eastern boundary upwelling system regions, particularly the California and Humboldt Current Systems. Rates of acidification and corresponding increases in pteropod shell dissolution are projected to be the fastest in the North and South Equatorial Currents. These are the regions with the greatest impacts on pteropods and biogeochemical implications.
Continue reading ‘Global synthesis of the status and trends of ocean acidification impacts on shelled pteropods’Prepared microplastics interaction with Artemia salina under low pH conditions representing ocean acidification; a simulated environmental exposure
Published 31 October 2023 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, physiology, reproduction, toxicants, zooplankton
Ocean acidification and microplastic pollution are two of the major ecological concerns. The distribution of large quantities of plastic debris and microplastics all across the oceans emphasises the need to determine the influence of microplastics in ocean acidification and to evaluate its concomitant toxicological effects on aquatic life forms. Studies on the combined impact of both the stressors are very limited, but much needed in the current scenario. Where most of the present-day research use purchased microplastics of defined size and morphology (microspheres, fibres, rods, etc.), the present study employs prepared “true to life microplastics” that resemble the environmental microplastic pollutants in morphology and size heterogeneity. The present study focusses on evaluating the fate and impact of oceanic microplastics on the physiology and development of Artemia salina (Brine shrimp), one among the most ecologically significant zooplankton species. Natural sea water was acidified by controlled perturbation of carbon dioxide using a valve system. The hatching rate of A. salina cysts receded significantly (p < 0.05) upon singular exposures to microplastics and low pH (7.80), whereas combined effect was insignificant. The reactive oxygen species (ROS) elevated as a result of individual exposures to microplastics and low pH. However, only in 0.5 mg mL−1 PE treatments at pH 7.80, an additive impact was reported for ROS activity (p < 0.05). The SOD activities increased significantly but it can be attributed as the individual responses towards exposure to both the stressors. A significant additive impact was not observed for SOD activity (p > 0.05). But during the development, significant morphological anomalies were observed. Changes in the appendages of nauplii and juveniles as a result of combined exposure to microplastics and low pH treatments are significant findings. Our observations suggest that coupled exposure to microplastics and low pH could induce significant oxidative stress in the marine zooplanktons and also adversely affect their normal development. Findings from the current study emphasise the need for further research to understand the coupled toxicological impacts of ocean acidification and predominant pollutants such as microplastics to other marine animals as well.
Continue reading ‘Prepared microplastics interaction with Artemia salina under low pH conditions representing ocean acidification; a simulated environmental exposure’Interactive effects of ocean acidification and temperature on oxygen uptake rates in Calanus hyperboreus nauplii
Published 30 October 2023 Science ClosedTags: Antarctic, biological response, crustaceans, laboratory, multiple factors, physiology, respiration, temperature, zooplankton
The Arctic region is undergoing rapid and significant changes, characterized by high rates of acidification and warming. These transformations prompt critical questions about the resilience of marine communities in the face of environmental change. In the Arctic, marine zooplankton and in particular calanoid copepods play a vital role in the food web. Changes in environmental conditions could disrupt zooplankton communities, posing detrimental consequences for the entire ecosystem. Copepod early-life stages have been shown to be particularly sensitive to environmental stressors since they represent a bottleneck in the life cycle. Here, we investigated the responses of 4-day old Calanus hyperboreus nauplii when exposed to acidification (pH 7.5 and 8.1) and warming (0 and 3°C), both independently and in combination. Naupliar respiration rates increased when exposed to a combination of acidification and warming, but not when exposed to the stressors individually. Moreover, we found no discernible differences in lipid content and fatty acid (FA) composition of the nauplii across the different experimental treatments. Wax esters accounted for approximately 75% of the lipid reserves, and high amounts of long chain fatty acids 20:1 and 22:1, crucial for the reproduction cycle in copepods, were also detected. Our results indicate a sensitivity of these nauplii to a combination of acidification and warming, but not to the individual stressors, aligning with a growing body of evidence from related studies. This study sheds light on the potential implications of global change for Arctic copepod populations by elucidating the responses of early-life stages to these environmental stressors.
Continue reading ‘Interactive effects of ocean acidification and temperature on oxygen uptake rates in Calanus hyperboreus nauplii’The transcriptome profile of the marine Calanoid copepod Parvocalanus crassirostris isolated from Kuwait territorial waters and generations cultured under different ocean acidification scenarios
Published 16 October 2023 Science ClosedTags: biological response, crustaceans, Indian, laboratory, molecular biology, zooplankton
Copepods are primary consumers, amounting to about 70 % of the metazoans in the marine environment, and are fundamental to marine food webs. Ocean acidification (OA) and ocean warming (OW) significantly affect the copepod community leading to the severe consequences of an ecological imbalance. Molecular resources are minimal for copepods and call for transcriptome profiling to better understand their responses under changing environmental conditions. This manuscript describes the de novo transcriptome of Parvocalanus crassirostris, a common inhabitant of coastal waters. RNA sequencing (RNAseq) was performed on whole organisms. Raw reads assembled through Trinity comprised 344,652 transcripts and 249,255 unigenes. Bench-marking-universal-single-copy-orthologs (BUSCO) analysis identified 86.6 % (C:86.9 % [S: 78 %, D: 8.6 %], M: 3.5 %, F: 9.9 %) of the assembly to be complete. Approximately 40 % and 12 % of unigenes were functionally annotated against the gene ontologies (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The dominant GO categories were cellular (58.20 %) > metabolic (55.91 %) > catalytic activity (50.12 %) > binding (45.55 %) > cellular anatomical entity (39.36 %) > and intracellular binding (21.68 %). In contrast, signal transduction pathways were the dominant pathways under the environment information processing of the KEGG category. Differential gene expression analysis was performed on different generations of copepods under progressively lower pH. Over 99,117 unigenes were discovered, of which 53,044 were upregulated and 46,073 downregulated. Gene ontologies enrichment analysis revealed significantly different functional pathways at a false discovery rate (FDR) of q< 0.05 (COP1-COP2: 15; COP1-COP3: 47; COP2-COP3: 22). The KEGG enrichment informed genes associated with 17 pathways to be upregulated while 31 pathways to be downregulated. This investigation provides an important genomic resource of P. crassirostris under ambient conditions and in future climate scenarios in response to OA.
Continue reading ‘The transcriptome profile of the marine Calanoid copepod Parvocalanus crassirostris isolated from Kuwait territorial waters and generations cultured under different ocean acidification scenarios’Transgenerational adaptation to ocean acidification determines the susceptibility of filter-feeding rotifers to nanoplastics
Published 26 September 2023 Science ClosedTags: biological response, laboratory, molecular biology, multiple factors, North Pacific, performance, physiology, toxicants, zooplankton
The adaptation of marine organisms to the impending challenges presented by ocean acidification (OA) is essential for their future survival, and mechanisms underlying OA adaptation have been reported in several marine organisms. In the natural environment, however, marine organisms are often exposed to a combination of environmental stressors, and the interactions between adaptive responses have yet to be elucidated. Here, we investigated the susceptibility of filter-feeding rotifers to short-term (ST) and long-term (LT) (≥180 generations) high CO2 conditions coupled with nanoplastic (NPs) exposure (ST+ and LT+). Adaptation of rotifers to elevated CO2 caused differences in ingestion and accumulation of NPs, resulting in a significantly different mode of action on in vivo endpoints between the ST+ and LT+ groups. Moreover, microRNA-mediated epigenetic regulation was strongly correlated with the varied adaptive responses between the ST+ and LT+ groups, revealing novel regulatory targets and pathways. Our results indicate that pre-exposure history to increased CO2 levels is an important factor in the susceptibility of rotifers to NPs.
Continue reading ‘Transgenerational adaptation to ocean acidification determines the susceptibility of filter-feeding rotifers to nanoplastics’
