Ocean acidification (OA) refers to the increase in the partial pressure of CO2 and decrease in the pH of seawater resulting from the absorption of atmospheric CO2 by the ocean. This study investigated OA impacts across multiple generations (F0-F3) of the copepod Acartia tonsa which were exposed to four pH conditions (8.1, 7.8, 7.6 and 7.1). Key reproductive and developmental traits were evaluated, including egg production, hatchability, development time, fecal pellet production, and sex ratio. Results showed that pH 7.1 significantly reduced egg production, hatchability and fecal pellet production, while prolonging the N–C time; N-A time remained unaffected by pH across all groups. For sex ratio, a downward trend was observed with increasing generations and decreasing pH: in F3, female proportion in pH 7.8, 7.6 and 7.1 groups was significantly lower than in the control group, and pH 7.1 and 7.6 groups had lower F3 female proportion than in the F1 generation. A. tonsa showed some tolerance under short-term acidification conditions at pH 7.1, but its physiological functions were further reduced after long-term exposure, suggesting a limited adaptive capacity. Ecologically, A. tonsa is a dominant coastal zooplankton species that links phytoplankton to higher trophic levels (e.g., fish larvae) and mediates energy flow and biogeochemical cycling. These results highlight the risks to key zooplankton populations and associated ecosystem functioning. Future studies should focus on the long-term effects of acidification on A. tonsa and combine multi-species experiments with field surveys to assess the ecological risks of OA.
Continue reading ‘Multigenerational physiological plasticity of the marine copepod Acartia tonsa in response to ocean acidification’Posts Tagged 'zooplankton'
Multigenerational physiological plasticity of the marine copepod Acartia tonsa in response to ocean acidification
Published 16 July 2026 Science Leave a CommentTags: biological response, BRcommunity, crustaceous, laboratory, morphology, physiology, reproduction, zooplankton
Anthropogenic stressors and amphipod size influence herbivory on eelgrass in San Francisco Bay
Published 15 July 2026 Science Leave a CommentTags: biological response, crustaceans, laboratory, mesocosm, morphology, multiple factors, North Pacific, nutrients, phanerogams, zooplankton
Seagrasses provide valuable ecosystem functions, yet they are declining globally due to anthropogenic stressors. Understanding how global climate stressors like ocean acidification interact with local environmental conditions (e.g., increased nutrient pollution) to affect ecosystem dynamics can be used to inform management of these habitats. In San Francisco Bay, it is unknown how stressor interactions will affect herbivory by Ampithoe valida, an invasive amphipod that exhibits novel feeding behavior by directly consuming the tissue of Zostera marina (eelgrass), which has been linked to negative impacts on local meadows. The goal of this study was to determine how anthropogenic stressors and amphipod size influence A. valida herbivory on eelgrass in San Francisco Bay to evaluate the ecological implications for eelgrass habitats. To further understand this relationship, feeding assays first examined food preferences of A. valida of three sizes on eelgrass of two ages and epiphytic algae. Secondly, a mesocosm experiment exposed A. valida of medium and large sizes to levels of ocean acidification expected with accelerating climate change and eelgrass to levels of nutrient pollution possible from point sources along shorelines, to test if these combined stressors affect A. valida direct herbivory of eelgrass. Additionally, A. valida were collected in the field during peak eelgrass growing season in summer and early fall to determine their size distributions and provide context to the experiments. Results found that A. valida largely prefer epiphytic algae over eelgrass regardless of their size. When offered only eelgrass, medium to large individuals consumed the tissue, whereas small individuals exhibited near-zero consumption. Although small A. valida were most abundant in field collections, medium-sized individuals were also present in moderate numbers, suggesting amphipods of this size may be the primary contributors to direct eelgrass consumption in San Francisco Bay, with high-consuming large individuals less common. Mesocosm results indicated that increased nutrients reduced eelgrass aboveground morphology (leaf size) and biomass, while tissue nutrient content increased, suggesting that although nutrients were taken up, they were not used for growth. Finally, feeding assays revealed that the effects of reduced pH and nutrient additions on A. valida eelgrass herbivory varied with grazer size and experimental context. In the no-choice assay, medium-sized individuals increased consumption under reduced pH relative to ambient pH, while large individuals consumed more of the highest nutrient-enriched eelgrass tissue. In contrast, the choice assay showed higher eelgrass consumption under ambient pH relative to reduced pH, and no effect of nutrient additions. This suggests that under reduced pH A. valida may shift their feeding behavior depending on environmental context, potentially increasing consumption through compensatory feeding on lower-quality tissue when food options are limited or reducing consumption when alternative refugia and higher-quality resources are available. This also indicates that ocean acidification may primarily alter eelgrass grazing behavior among mid sized A. valida, while nutrient enrichment may increase grazing pressure from larger individuals, potentially exacerbating eelgrass vulnerability in San Francisco Bay given reduced plant performance under high-nutrient conditions.
Continue reading ‘Anthropogenic stressors and amphipod size influence herbivory on eelgrass in San Francisco Bay’Climate assessment report for the Central Arctic Ocean (CAO) [Suppl. to ICES Scientific Reports 8(25)]
Published 9 July 2026 Science Leave a CommentTags: Arctic, chemistry, community composition, fish, mammals, zooplankton
Climate change is transforming the Central Arctic Ocean (CAO) at an unprecedented pace. Sea ice is rapidly declining in extent, thickness, and age, with projections indicating an ice-free summer Arctic by mid-century, possibly earlier. This loss of ice amplifies warming, alters stratification and circulation, and accelerates ocean acidification—occurring up to four times faster than the global average—threatening calcifying organisms and ecosystem stability.
Biological impacts are profound: shifts in microbial and primary producer communities, reduced ice-associated biodiversity, and boreal species moving northward disrupt food webs. Benthic ecosystems show signs of long-term decline in biodiversity and organic carbon supply, while fish, seabirds, and marine mammals face habitat loss, changing prey availability, and new stressors such as increased predation and contaminants. Some species may benefit from enhanced productivity, but cumulative effects of warming, acidification, and ice loss remain uncertain. These changes interact with other pressures—pollution, invasive species, and human activities—creating complex, compounding stress on the CAO ecosystem. Knowledge gaps on tipping points and resilience underscore the urgent need for research on circulation, carbon dynamics, and species adaptation to inform conservation and management strategies.
Continue reading ‘Climate assessment report for the Central Arctic Ocean (CAO) [Suppl. to ICES Scientific Reports 8(25)]’Evaluating the combined effects of ocean acidification and harmful algal blooms on the fitness of Artemia salina
Published 6 July 2026 Science Leave a CommentTags: biological response, crustaceans, laboratory, mortality, multiple factors, performance, physiology, reproduction, toxicants, zooplankton
This study assessed the potential synergistic effects of harmful algal blooms (HABs) and ocean acidification (OA) on the survival and grazing potential on HABs by brine shrimp (Artemia salina). The effects on the fitness of three life stages (i.e. newly hatched, 1-week old, and 2-week old post hatch) of A. salina was evaluated over a 24-hour period. Using well plates, A. salina were individually exposed to toxin producing HABs (i.e. Alexandrium catenella or Margalefidinium polykrikoides), a non-toxin producing HAB (i.e. Gymnodinium aureolum), and fed or unfed non-HAB controls. pH conditions administered were ambient (pH ~ 8) or acidified (pH ~ 7.2). Survival analysis revealed a significant effect of treatment on mortality across life stages. Hazard ratios showed elevated mortality in HAB treatments relative to controls, while OA alone did not. HAB exposure or ontogeny are more important for survival of A. salina than short-term OA exposure. Regarding grazing potential, significant reductions in HAB cell density were more commonly found in treatments with older individuals than younger conspecifics. Cell density of A. catenella was never significantly reduced as compared with other HAB treatments. Overall, exposure to OA conditions did not affect the survival or grazing potential of A. salina, but the species of HAB did.
Continue reading ‘Evaluating the combined effects of ocean acidification and harmful algal blooms on the fitness of Artemia salina’Pteropod vulnerability to ocean acidification in the eastern Arabian Sea
Published 18 June 2026 Science ClosedTags: biological response, BRcommunity, Indian, laboratory, mollusks, zooplankton
Highlights
- First study on pteropod response to ocean acidification in the eastern Arabian Sea.
- High pteropod abundance during fall inter monsoon season due to food availability.
- pH in the Arabian Sea was low during south west monsoon with pHT upto 7.75
- Pteropod shell dissolution was observed under acidified conditions
- Protrusions through the pteropod shell were observed under acidified conditions
Abstract
The rapid rise in atmospheric CO2 and its subsequent uptake by the oceans has led to ocean acidification and other associated changes in the marine ecosystem. The recent reports of the shoaling of the aragonite saturation horizon in the northern Indian Ocean are particularly alarming, as they pose a serious threat to the survival of calcareous organisms. Pteropods, also known as sea-butterflies, are believed to be highly susceptible to ocean acidification due to their thin aragonite shell. In our study in the eastern Arabian Sea, we found low pH conditions with surface pHT as low as 7.751 during late South-west monsoon (SWM). The pteropod abundance is high during the fall inter-monsoon (FIM), suggesting that the system continues to sustain productivity even after the cessation of peak monsoon activity. This also implies that the food availability regulates pteropod abundance in the eastern Arabian Sea. As pteropods are key components of food sources for many marine species, such as fish, any changes in their abundance can have cascading effects on the marine food web. To show how pteropods will be affected in futuristic elevated CO2 conditions, a CO2 manipulation experiment was conducted in the eastern Arabian Sea during December 2024. Pteropods belonging to Creseis acicula from the eastern Arabian Sea were subjected to pHT = 7.470, and pCO2 = 1734 μatm under controlled conditions. Our findings suggest that acidification led to the dissolution of pteropod shells. Acidification also led to protrusion through the shells, and these protrusions varied in length up to 88 μm. These structural alterations represent an acute response of pteropod shells to reduced pH, highlighting their rapid vulnerability to acidification stress. These observed protrusions need to be assessed further to determine if they provide any competitive advantage in combating or minimizing the impact of ocean acidification.
Continue reading ‘Pteropod vulnerability to ocean acidification in the eastern Arabian Sea’Combined ecotoxicity of microplastics and crude oil co-pollutants: occurrence, distribution and its synergistic impact with ocean acidification on Artemia franciscana
Published 3 April 2026 Science ClosedTags: biological response, crustaceans, Indian, laboratory, multiple factors, physiology, plastics, reproduction, toxicants, zooplankton
Microplastics (MPs) are recognized as a global concern, with specific attention shifted towards marine MPs pollution. This particular study investigates the abundance and distribution of crude oil-loaded microplastics (COMPs) along the Chennai coastline, Tamil Nadu, India and evaluates their combined toxicological effects with ocean acidification on Artemia franciscana. Spatial analysis revealed that Ennore Creek exhibited the highest MP concentration (10.82 ± 0.2 items/L). Polypropylene was recorded as the predominant polymer type followed by low density polyethylene and polyethylene terephthalate, with particle size ranging from 250 to 500 µm. COMPs were detected across all sampling sites, with concentrations declining from Ennore Creek (0.21 ± 0.03 items/L) to Kasimedu Beach (0.10 ± 0.02 items/L). The adsorption of crude oil on MPs is primarily mediated by physical interaction with multi-layer adsorption behaviour. The results highlighted that increase in MP concentration and decrease in seawater pH significantly induced acute toxicity and oxidative stress responses in A. franciscana. At pH 7.8, experimental groups exposed to 0.5 mg/mL of COMPs developed higher ROS, SOD and catalase activity (p<0.001). Whereas control groups alone showed significant increase in oxidative stress responses at lower pH level such as pH 7.8 and 8.0. Combined exposure of COMPs and low pH conditions significantly increased oxidative damages in A. franciscana and affected its hatching ability. The observations from this study emphasize the urgent need for integrated monitoring and further research to explore combined toxicological effects of MPs and ocean acidification to other marine organisms as well.
Continue reading ‘Combined ecotoxicity of microplastics and crude oil co-pollutants: occurrence, distribution and its synergistic impact with ocean acidification on Artemia franciscana’Impacts of ocean acidification on marine zooplankton: a review of physiological, developmental, and reproductive responses
Published 31 March 2026 Science ClosedTags: adaptation, biological response, otherprocess, physiology, reproduction, review, zooplankton
Acidification. The increasing levels of carbon dioxide CO₂ in the atmosphere are leading to ocean acidification, and this is altering the chemical content of marine water and is endangering life in the oceans. The examples of marine zooplankton, including Copepods, Pteropods, krill, and larvae of invertebrates are essential to the pelagic food webs and carbon cycles, even though they differ in their tolerance to low PH concentration and high pCO₂ levels. Early developmental phases are particularly vulnerable, with them showing retardation in developmental stages, reduced hatch rates, physical deformities as well as a lack of calcification. Higher carbon dioxide CO₂ levels interfere with the acid-base balance, increase oxidative stress and alter the allocation of metabolism, leading to trade-offs that lower growth, reproduction and survival rates. Calcifying organisms such as the pteropods are highly susceptible whereas some of the non-calcifying copepods exhibit a level of physiological resilience. Negative effects of other stressors may be affected by increased temperature, oxygen depletion, and nutrient enrichment which may further compound negative effects. There is some evidence that there is some possible acclimation in the short term and that there might be transgenerational plasticity but we do not understand adaptive capacity in the long term. Knowledge gaps exist in regard to multigenerational response, non-calcifying and gelatinous species and how physiological plasticity occurs. Species-specific responses are an important aspect of predictive models to estimate the impact of the ecosystem and guide conservation efforts. To ensure marine ecosystems remain stable as ocean acidification continues, vulnerable zooplankton should be safeguarded to preserve tropic structure, nutrient cycling, and nutrient stability.
Continue reading ‘Impacts of ocean acidification on marine zooplankton: a review of physiological, developmental, and reproductive responses’Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea
Published 25 March 2026 Science ClosedTags: abundance, biological response, chemistry, community composition, crustaceans, field, nematodes, North Pacific, otherprocess, zooplankton
This study aimed to investigate the meiofauna community characteristics in coastal waters affected by ocean acidification. Therefore, the meiofauna communities in the coastal waters of Hupo in Uljin-gun, which showed a high ocean acidification trend in the integrated data on the coastal areas of South Korea for the previous ten years, were monitored over five years. During the study period, the mean abundance of total meiofauna communities expressed in population density was 614 individuals (Inds.)/10 cm2. The most dominant taxa were nematodes (65–70%) and harpacticoids (7–20%); these two taxa accounted for approximately 80% of the total meiofauna abundance. Station (St.) 5 and 10, which had the lowest seawater pH values, showed the lowest average abundance values for harpacticoids (average 46 Inds./10 cm2) and nauplius (average 4 Inds./10 cm2) among the major meiofaunal groups over the 5-year period. In addition, St. 5 indicated the lowest meiofaunal diversity index of 0.54. To examine the effect of ocean acidification on meiofauna communities at the species level, species of nematodes, the most dominant taxon, were analyzed. The results indicated that the number of nematode species at St. 10, one of the two stations with the lowest pH, was the lowest compared to those at other stations. Analysis of c-p values for nematode species showed that both species sensitive to environmental disturbance and species resistant to environmental pollution appeared at high rates. According to the feeding type of nematodes, epistrate feeders accounted for a remarkably high proportion at St. 10. This study provides various data on meiofauna community characteristics to understand the effects of ocean acidification on coastal ecosystems.
Continue reading ‘Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification on the coast of Korea’Eco-evolutionary dynamics of planktonic calcifying communities under ocean acidification
Published 12 March 2026 Science ClosedTags: adaptation, biological response, BRcommunity, calcification, communitymodeling, growth, modeling, mortality, otherprocess, performance, phytoplankton, primary production, zooplankton
Increasing emissions of CO2 into the atmosphere are causing ocean acidification, threatening calcifying organisms. In this study, we model the physiological responses of coccolithophorids to acidification to understand the ecological and evolutionary outcomes of a system in interaction with zooplankton. Assuming a trade-off between growth and protection against grazing, we show that calcification has bivalent effects on transfers between two trophic levels and that acidity can strongly alter energy transfers. Taking into account the evolution of calcifying phenotypes in response to acidification, we show that the system outcome contrasts with previous results. While the effect of evolution depends on how calcification affects grazing, it nevertheless follows that acidification leads to a decrease in calcifying capacity. This evolutionary decrease may be progressive, but can also lead to tipping points where abrupt shifts may occur. Such a counter-selection of calcification in turn affects ecosystem functioning, enhancing energy transfers within the system and modifying carbon fluxes. We discuss how such eco-evolutionary changes may impact food webs integrity, carbon sequestration into the deep ocean and therefore endanger the carbon pump stability.
Continue reading ‘Eco-evolutionary dynamics of planktonic calcifying communities under ocean acidification’Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH
Published 2 January 2026 Science ClosedTags: biological response, crustaceans, growth, laboratory, mortality, multiple factors, reproduction, temperature, zooplankton
Cirolanid isopods play important ecological roles as predators and scavengers, but when populations increase, they can form swarms that attack fish and humans. Understanding how the reproduction of cirolanid isopods will be affected by future warmer and more acidic oceans is therefore important. Samples of the viviparous species Cirolana harfordi were held in 4 combinations of 2 temperatures (18 and 24°C) and 2 pH levels (7.7 and 8.1), and the development of embryos and mancas was investigated by microscopic examination of each pregnant female through the transparent ventral cuticle of their thorax. Higher temperature increased the rate of development, thereby reducing pregnancy duration and accelerating the growth of mancas postpartum. By contrast, increased acidity had no significant effect on these parameters and had no deleterious effects on the development of the mancas. Higher temperature did not have a significant effect on the number of postpartum mancas after the 22 weeks that the adults spent in treatments. Increased temperature and/or lowered pH had no effect on the adult survival or growth. These data are in keeping with the hypothesis that C. harfordi may be able to withstand future warmer and more acidic oceans. Longer-term studies are needed to determine whether decreasing pregnancy durations in higher temperatures increases the number of times females can become pregnant over their lifetime, potentially leading to greater population numbers.
Continue reading ‘Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH’Stressed overwintering bottleneck hypothesis: ocean warming and acidification synergistically disrupt Arctic zooplankton overwintering
Published 1 December 2025 Science ClosedTags: Arctic, biological response, crustaceans, laboratory, molecular biology, mortality, multiple factors, physiology, reproduction, respiration, temperature, zooplankton
Ocean warming (OW), driven by the influx of warm Atlantic water masses, and acidification (OA) are threatening Arctic marine ecosystems. However, their potential synergistic effects are poorly understood, especially during the Polar Night when marine species are particularly vulnerable to stressors. Here, we tested our novel Stressed Overwintering Bottleneck Hypothesis (SOBH): warming will disrupt the overwintering of the keystone pan-Arctic copepod Calanus glacialis, a pivotal secondary producer, by impairing fitness-related traits underpinning survival and reproduction. We exposed C. glacialis to current and projected future OW levels (0 °C and 4 °C) and OA levels (pH 8.0 and 7.4-7.3) for 53 days during the mid-Arctic Polar Night. We assessed survival, development, and physiological and molecular mechanisms (oxygen consumption, lipid depletion, the expression of nine targeted genes related to oxidative stress and damage repair, and DNA damage). OW alone did not affect C. glacialis mortality; however, OA increased copepod survival at 0 °C. Notably, their combined effects (OWA) synergistically doubled mortality, as predicted by SOBH. Warming also accelerated moulting from copepodite stage V to adulthood in December, and increased respiration, exhausted lipid reserves entirely by early March, approximately one to four months before the spring algal bloom, further supporting SOBH. DNA damage and gene expression patterns indicated low investment in maintenance and damage repair. Collectively, these findings reveal hidden mechanisms by which OW and OA synergistically threaten overwintering Calanus copepods by drastically increasing mortality, accelerating moulting, raising metabolic rates, and causing early lipid depletion. These effects generate cross-seasonal phenological mismatches among overwintering survival, energy reserves, reproduction, and primary production. Such stressed overwintering bottlenecks in foundational secondary producers like Calanus copepods provide novel explanations for how OW and OA can constrict Arctic marine food webs. At a broader perspective, SOBH highlights how multiple stressors induced overwintering disruption could reshape pan-Arctic and global biodiversity.
Continue reading ‘Stressed overwintering bottleneck hypothesis: ocean warming and acidification synergistically disrupt Arctic zooplankton overwintering’Calcifying plankton: from biomineralization to global change
Published 28 October 2025 Science ClosedTags: biological response, mollusks, physiology, phytoplankton, protists, review, zooplankton
BACKGROUND
The production and dissolution of calcium carbonate (CaCO3) is a key component of the ocean carbon cycle. In the open ocean, nearly all CaCO3 is produced by three groups of calcifying plankton: coccolithophores, foraminifers, and pteropods. These taxonomically and functionally diverse organisms play a major role in ocean biogeochemistry by modulating air-sea CO2 exchange, and facilitating the export of carbon and alkalinity to depth.
Despite their biogeochemical importance, these groups are typically considered separately, precluding an integrated understanding. Yet the pathways by which CaCO3 is produced and cycled through the ocean have important consequences for the carbon cycle and ecosystem functioning. Notably, none of the Earth system models included in the current Coupled Model Intercomparison Project (CMIP6) explicitly represents these groups of organisms. Here, we review the distinct functional traits of coccolithophores, foraminifers, and pteropods to elucidate how these traits shape their global distributions, vulnerabilities to climate change and acidification, and their role in modulating ocean chemistry and the Earth system.
ADVANCES
Recent advances in data compilation at multiple levels offer a comprehensive but still incomplete view of the CaCO3 cycle, from biomineralization up to the global ocean, with different traits leading to differing vulnerabilities to environmental change. For example, coccolithophores, as primary producers, are relatively less affected by changes in oxygen concentration compared with heterotrophs, but are particularly sensitive to ocean acidification because of the proton load generated during intracellular calcification, which requires effective pH regulation and proton expulsion. Differing resource requirements contribute to the geographic distributions of each group, while traits such as body size and turnover rate are fundamentally linked to global production, export, dissolution, and burial. Compiling these data allows us to compare the markedly different fates of the CaCO3 produced by each group, from surface production through export to eventual sediment burial. A major imbalance exists in the global CaCO3 cycling related to each calcifying plankton group, with key uncertainties, especially in rates of group-specific production and shallow biologically mediated dissolution. Current best estimates indicate that a large fraction of coccolithophore-derived CaCO3—the dominant source of CaCO3 in the ocean—is dissolved and recycled in the upper ocean. This underscores the central role of ecological processes such as predation, particle aggregation, and microbial respiration in shaping ocean carbonate chemistry.
We suggest that the overlooked process of shallow dissolution, mainly of coccolithophores, is also likely at play within the geological record of this group.
OUTLOOK
The three major groups of calcifying plankton play essential but distinct roles within ocean ecosystems and the marine carbon cycle. Their diverse traits govern global distributions, production, export, and their differing response to environmental change. The magnitude of biologically mediated CaCO3 dissolution in the upper ocean remains broadly unrecognized, with implications for both the global alkalinity budget and interpretations of the fossil record. Sediment cores provide a fossil record going back 65 million years, revealing large variation in organism size and diversity likely linked to changes in seawater carbonate chemistry (acidification) and warming. The extent to which shallow, selective dissolution has biased this record remains an important unresolved question. Addressing discrepancies between CaCO3 production and export from the upper ocean will require renewed focus on both quantifying and understanding the individual and combined contribution of these groups, as well as the biological processes driving shallow dissolution. These efforts are also critical for incorporating a mechanistically resolved CaCO3 cycle into future climate models, thereby supporting a more integrated view of ocean biogeochemistry under climate change.
Continue reading ‘Calcifying plankton: from biomineralization to global change’Depth-resolved vertical distribution of the pteropod Limacina helicina in the Northeast Pacific and its implications for exposure to ocean acidification
Published 27 October 2025 Science ClosedTags: abundance, biological response, BRcommunity, field, mollusks, North Pacific, otherprocess, performance, review, zooplankton
The pteropod Limacina helicina has become an important bioindicator for the impacts of ocean acidification on marine ecosystems, yet its vertical distribution and diel vertical migration (DVM) patterns remain poorly understood. Understanding these behaviours is critical to accurately predict the risks of ocean acidification to pteropods since the depth ranges they inhabit strongly influence their exposure to water corrosive to aragonite shells (i.e. ΩAr <1), given the natural vertical gradients in pH and ΩAr. To resolve the vertical distribution of L. helicina, we utilized an existing dataset consisting of 179 vertically stratified zooplankton net tows from the Northeast Pacific spanning 1983–2019. Using conventional observational analyses and Bayesian statistical models, we determine and compare the average day and night vertical distributions of two size ranges of L. helicina, plus those of the strong vertical migrator euphausiid Euphausia pacifica and a non-migratory control group of mollusc larvae. We show that the average day and night vertical distributions and mean depths of L. helicina do not differ and closely match those of the non-migratory control, indicating that L. helicina does not perform DVM in this region. Typical mean depths of L. helicina are ∼50–70 m, with ≥ 75% of the population occupying the upper ∼100 m, and ≥ 50% being found in the upper ∼50 m, regardless of body size and time of day. Given the typical shape of ΩAr profiles in the ocean, we estimate that pteropod exposure to low ΩAr may be overestimated if calculated using the standard vertically integrated approach (i.e. a homogeneous depth distribution) as opposed to our depth-resolved vertical distribution.
Continue reading ‘Depth-resolved vertical distribution of the pteropod Limacina helicina in the Northeast Pacific and its implications for exposure to ocean acidification’Seasonal and interannual variability of Atlantidae heteropods along the west coast of Baja California, Mexico
Published 23 October 2025 Science ClosedTags: biological response, chemistry, community composition, field, mollusks, North Pacific, otherprocess, zooplankton
Highlights
- Atlantid species richness was higher in winter than in spring.
- Maximum species diversity was associated with the 2013–2016 anomalous warm period.
- Distribution associated with seawater masses, hypoxia, and aragonite saturation.
- Atlantid species are potential biological indicators of environmental changes.
Abstract
The Atlantidae are holoplanktonic gastropods with aragonitic shells that inhabit the epipelagic habitat primarily in tropical and subtropical oceans, as well as in certain transitional and temperate regions, such as the California Current System. However, there is limited knowledge about how their diversity, distribution, and abundance respond to environmental changes over different time scales. The strongest seasonal changes of zooplankton species composition and environmental conditions in the southern California Current System occur between winter and spring. El Niño Southern Oscillation and marine heat waves are two additional environmental change drivers of interannual scale. Our aim was to infer the effect of the seasonal (winter-spring) and interannual (2012–2016) environmental variability on the diversity, distribution, and abundance of the Atlantidae species assemblage along the Pacific coast off the Baja California peninsula, Mexico. Atlantidae diversity was higher during winters than during springs. Their horizontal distribution recorded during winter was statistically correlated with temperature, salinity, and the seawater masses distribution, and during spring was correlated with the depth of hypoxic conditions (<60 μmol O2/kg oxyline) and the depth of Ω aragonite saturation horizon. Atlanta californiensis was the most abundant species, mainly during spring and its relative abundance decreased during anomalously warm periods, while tropical/subtropical species showed an opposite abundance pattern. The maximum species richness was associated with the 2013–2015 marine heat wave and El Niño 2015–2016 events, when tropical species were observed in the study area. Differences in the species community structure, their response to Ω aragonite undersaturated waters and hypoxia, and their seawater mass affinity showed that atlantids are useful biological indicators of environmental changes, ocean acidification, and deoxygenation conditions.
Continue reading ‘Seasonal and interannual variability of Atlantidae heteropods along the west coast of Baja California, Mexico’DNA methylation plasticity drives copepod resilience to coastal high pCO2 and cadmium pollution under multigenerational exposure
Published 20 October 2025 Science ClosedTags: adaptation, biological response, crustaceans, laboratory, metals, molecular biology, mortality, multiple factors, North Pacific, otherprocess, reproduction, zooplankton
Highlights
- Fluctuating acidification caused the most Cd multigenerational toxicity in copepods.
- The adverse effects of acidification and Cd tended to intensify during F1-F3.
- The copepods potentially adapted to combined exposure in F4.
- DNA hypomethylation rendered copepods presenting the adaptive potential.
ABSTRACT
The vast majority of coastal organisms have been facing multigenerational scenarios of fluctuatingly high pCO2 and Cd pollution in their natural habitats. However, the adaptive capacity of these organisms to such combined stressors and the underlying mechanisms remain poorly understood. In this study, we conducted a multigenerational experiment (F1-F4) to investigate the adaptive responses of the marine copepod Tigriopus japonicus to combined fluctuatingly high pCO2 and Cd exposure, along with the associated mechanisms. Our findings revealed that steady high pCO2 aggravated Cd multigenerational toxicity, and it was more under fluctuating acidification. Notably, by the F4 generation, copepods potentially adapted to the combined stressors. Through transcriptomic and DNA methylation analyses of copepods from the F1 and F4 generations, we found that under combined exposure, F1 copepods likely reallocated more energy to counteract Cd toxicity; however, DNA hypermethylation inhibited Cd exclusion and detoxification/stress response pathways, ultimately compromising development and reproduction. In contrast, in the F4 generation, DNA hypomethylation enhanced processes such as cuticle repair program, compensatory mechanism (e.g., detoxification and immune response), and reproduction, consequently increasing the copepod’s fitness. These findings reveal an epigenetic basis for phenotypic acclimatization, offering marine copepods a supplementary mechanism to cope with combined stressors.
Continue reading ‘DNA methylation plasticity drives copepod resilience to coastal high pCO2 and cadmium pollution under multigenerational exposure’Significant effects of temperature and pH on zooplankton dynamics: implications for ocean warming and acidification
Published 20 October 2025 Science ClosedTags: abundance, biological response, community composition, field, multiple factors, North Pacific, otherprocess, temperature, zooplankton
Highlights
- The Yellow Sea coast showed a trend of warming and acidification of the sea water.
- Zooplankton along the Yellow Sea coast were affected by temperature and pH.
- Zooplankton showed significant spatial and temporal dynamics.
Abstract
Coastal ecosystems are increasingly affected by ocean warming and acidification, yet their combined impacts on zooplankton communities remain inadequately studied. Based on 11 ecological surveys conducted along the Yellow Sea coast between 2021 and 2023, we analyzed the responses of zooplankton communities to changes in seawater temperature and pH, which were accompanied by pronounced seasonal and spatial variation in community structure. Results revealed continuous warming and acidification trends. Copepods were the dominant group, followed by planktonic larvae, while Noctiluca scintillans and Centropages abdominalis exhibited clear seasonal outbreaks. Temperature showed a significantly negatively correlated with zooplankton abundance and biomass but positively with diversity and evenness, conversely, pH demonstrated the reverse pattern. Model analyses further indicated that the synergistic effects of warming and acidification were a major driver of dynamic and nonlinear fluctuations in zooplankton communities, pointing to the ecological instability of this coastal ecosystem. These findings provide observational evidence of climate-driven ecological change and highlight the importance of integrating zooplankton indicators into coastal monitoring and management strategies.
Continue reading ‘Significant effects of temperature and pH on zooplankton dynamics: implications for ocean warming and acidification’Molecular responses of amphipod (Parhyale darvishi), to pH stress in Persian Gulf
Published 10 October 2025 Science ClosedTags: biological response, crustaceans, Indian, laboratory, molecular biology, zooplankton
Climate change is driving more frequent and extreme pH fluctuations in intertidal habitats, yet the molecular mechanisms by which small crustaceans cope with acid–base stress remain poorly understood. In this study, we evaluated the transcriptional responses of the intertidal amphipod Parhyale darvishi to acute low-pH (6.0) and high-pH (9.0) challenges, simulating the extremes observed in tide pools. Following a 7-day acclimatization in aerated seawater (salinity 40–42 ppt, 24–25 °C, 12:12 h light:dark), individuals (4–7 mm length) were randomly assigned to one of three treatments: control (ambient pH 7.50–7.60), low pH (adjusted to 6.0 with 20 mL 37% HCl), or high pH (adjusted to 9.0 with 3 mL NaOH), each with two 1-L replicates containing 50 animals. After 0h, 12h and 24 h of exposure, total RNA was extracted and reverse-transcribed to cDNA. Real-time PCR assays quantified expression of five target genes: catalase (CAT), glutathione S-transferase (GST), Na⁺/K⁺-ATPase, apoptosis signal-regulating kinase 1 (ASK1), and caspase-3, with tubulin serving as the reference gene. Both pH stressors elicited significant transcriptional changes relative to controls. Under low pH, antioxidant genes CAT and GST were upregulated by approximately 2.5- and 2.1-fold, respectively, indicating activation of oxidative defense pathways. In contrast, high pH induced a more moderate antioxidant response (1.8- and 1.5-fold for CAT and GST) but triggered a pronounced apoptotic signal, with caspase-3 expression increasing nearly 3-fold. Na⁺/K⁺-ATPase transcripts rose under both treatments, reflecting osmoregulatory adjustments, while ASK1 exhibited a stronger induction in acid-stressed amphipods, suggesting stress-activated kinase signaling. These findings demonstrate that P. darvishi mounts distinct molecular responses to acid versus alkaline challenges, engaging antioxidant defenses under low pH and apoptosis-related pathways under high pH. Such differential gene expression profiles provide mechanistic insight into how intertidal amphipods cope with rapid pH swings, and underscore the utility of molecular biomarkers for assessing the resilience of coastal invertebrates under future acidification and alkalinization scenarios.
Continue reading ‘Molecular responses of amphipod (Parhyale darvishi), to pH stress in Persian Gulf’Temperature and CO2 alter trophic structure of Arctic plankton assemblages
Published 27 August 2025 Science ClosedTags: Arctic, biological response, BRcommunity, growth, laboratory, multiple factors, performance, phytoplankton, temperature, zooplankton
Driven by increasing anthropogenic CO2, the impact of ongoing climate change on the marine plankton ecosystem ultimately extends to higher trophic levels and the biogeochemical cycling of carbon and nutrients. However, the impacts of multiple environmental changes on trophic interactions between predator and prey have still not been fully explored. Here we conducted incubation experiments to determine the temperature and CO2 sensitivities of marine phytoplankton growth and microzooplankton grazing in the western Arctic Ocean, where rapid climate change is taking place. The temperature sensitivity of the growth of larger phytoplankton decreased owing to the increase in CO2 levels, whereas that of the growth of smaller phytoplankton increased under higher CO2 levels. Notably, the temperature sensitivity of Arctic phytoplankton is at least two times higher than the canonical estimates irrespective of size classes, highlighting the uniqueness of the Arctic ecosystem’s response to warming. Microzooplankton grazing was closely coupled with, but did not exceed, the growth rates of their prey, suggesting that microzooplankton behavior is mainly regulated by prey availability rather than the ambient environment. The higher competitiveness of smaller phytoplankton under higher temperatures and CO2 conditions might lead to a less productive Arctic Ocean ecosystem for higher trophic-level organisms in the future.
Continue reading ‘Temperature and CO2 alter trophic structure of Arctic plankton assemblages’Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal
Published 21 August 2025 Science ClosedTags: abundance, biological response, community composition, field, Indian, mollusks, otherprocess, protists, zooplankton
Anthropogenic greenhouse gas emissions have a detrimental impact on the carbon sequestration by the oceans. Pteropods, a crucial component of the ocean’s planktic community, secrete aragonite shells that are sensitive to increasing atmospheric carbon dioxide levels, making them the first indicators of ocean acidification. Therefore, pteropods are often used to observe the changes in aragonite compensation depth (ACD). Intriguingly, in the major parts of the northern Indian Ocean, the chemically defined ACD is < 800 m, but pteropods have been reported in surface sediments collected from much deeper depths in the same region, which raises questions about the use of pteropods to trace ACD in this area. To address this ambiguity, we conducted a systematic and detailed evaluation of pteropods to trace the changes in ACD in the western Bay of Bengal, which is the first-ever such study. The pteropods population dominated by Heliconoides inflatus was low on the inner shelf, and isolated pockets of high pteropod abundance were restricted to the upper slope. Based on the pteropod abundance in the surface sediments and the ratio of pteropods to planktic foraminifera, we report the baseline ACD in the western Bay of Bengal at ~ 500 m. The aragonite compensation depth based on the pteropod abundance in the surface sediments correlates well with the chemically defined ACD in this region. These findings will help to assess the impact of ocean acidification on aragonite compensation depth in the western Bay of Bengal.
Continue reading ‘Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal’Strategies of marine plankton ecosystems to cope with climate change and their role in Ocean Negative Carbon Emissions (ONCE)
Published 5 August 2025 Science ClosedTags: biological response, phytoplankton, review, zooplankton
Current climate issues pose major challenges to human survival and development, with CO2 recognized as the main driver of climate change. The ocean, as Earth’s largest carbon sink, plays a vital role in the global carbon cycle, with Ocean Negative Carbon Emissions (ONCE) being a crucial pathway. Plankton, encompassing most marine primary producers and lower trophic-level consumers, are central to marine ecosystems and highly sensitive to climate change. Understanding their role in ONCE requires insight into their responses to ocean acidification and warming. These stressors influence plankton both at the cellular level-by altering biochemical processes-and at the community level-through adaptive differences and cascading ecological effects. Plankton responses may, in turn, generate feedbacks to the climate system. However, existing studies predominantly focus on individual species, lacking comprehensive cross-taxonomic comparisons. This review evaluates the effects of warming and acidification on diverse plankton groups, systematically analyzing their response mechanisms and potential climate feedbacks across multiple dimensions. The goal is to enhance understanding of the interactive processes between planktonic ecosystems and climate change, offering insights into their ecological functions and roles in shaping future carbon dynamics.
Continue reading ‘Strategies of marine plankton ecosystems to cope with climate change and their role in Ocean Negative Carbon Emissions (ONCE)’
