This research was intended to investigate the effects of reduced pH on the growth rates and diversity of phytoplankton in the coastal waters of Visakhapatnam in the Bay of Bengal. A short-term (six days) microcosm experiment was conducted with different pH conditions such as ambient (control-in situ pH), pH 8.0 (0.2 pH units drop from in situ pH) and pH 7.8 (0.4 pH units drop from in situ pH) corresponding to low, medium, and high future pH decline scenarios, respectively, to study the direct acidification impact on phytoplankton. The results revealed that the phytoplankton communities exhibit a wide range of responses including changes in growth rate during incubation. From the two treatments, a more pronounced response was observed in pH 7.8 conditions compared to the present pH scenario. Some phytoplankton communities exhibited positive growth responses to acidification, while others showed negative reactions in terms of biodiversity. Notably, Pseudo-nitzschia sp. became dominant during acidification, whereas larger centric diatoms such as Skeletonema spp., Chaetoceros spp., Rhizosolenia sp., Dactyliosolen fragilissimus, and Ditylum brightwellii showed no significant growth response to upcoming acidified conditions. This indicates a diverse array of physiological tolerance among the plankton species to environmental shifts. This study recommends further research to explore the impact of ocean acidification on other planktonic species in the coastal waters of Bay of Bengal.
Continue reading ‘Effects of pH on phytoplankton growth and diversity in a tropical coastal bay: an experimental study’Posts Tagged 'BRcommunity'
Effects of pH on phytoplankton growth and diversity in a tropical coastal bay: an experimental study
Published 14 April 2026 Science Leave a CommentTags: biological response, BRcommunity, community composition, growth, Indian, laboratory, otherprocess, phytoplankton
Coexpression among eastern oyster host and microbiome genes suggests coordinated regulation of calcifying fluid chemistry
Published 13 April 2026 Science Leave a CommentTags: biological response, BRcommunity, laboratory, molecular biology, mollusks, North Atlantic, physiology, prokaryotes
Significance
Oysters and many marine animals build shells by controlling the chemistry of extracellular fluids where minerals form, yet whether microbes in these fluids influence calcification remains unclear. We show that oysters maintain favorable conditions for mineral formation by regulating the carbonate chemistry of the shell-forming fluid, and that resident microbes respond to these changes by expressing nitrogen- and sulfur-cycling genes capable of altering pH, alkalinity, and carbonate availability. Many of these microbial transcripts were tightly correlated with oyster immune and signaling genes, suggesting that host and microbiome processes may be linked within the calcifying environment. These findings point to a host–microbiome interaction in the regulation of calcifying-fluid chemistry that directly links microbial activity to the carbonate chemistry underlying biomineralization.
Abstract
Marine animals that build shells, such as oysters, carefully regulate the chemistry of their internal calcifying fluids, but the molecular mechanisms behind this control, as well as whether microbes play a role in calcification, are poorly understood. To better understand oysters’ molecular mechanisms and the role of their calcifying-fluid microbes, we conducted experiments that simulated a tidal cycle, measured calcifying fluid pH and total dissolved inorganic carbon, and characterized host and microbial gene expression via transcriptomics. These experiments showed that calcifying fluid pH remained relatively stable throughout tidal pH fluctuations, with corresponding increases in oyster transcripts for ion transport and acid–base regulation. These data provide direct evidence that tidal fluctuations drive rapid changes in oyster calcifying fluid chemistry. Most surprisingly, increases in microbial transcripts related to nitrogen and sulfur cycling correlated to higher calcifying fluid DIC, and coexpression network analysis revealed patterns of gene expression that linked oyster immune and neural pathways to microbial redox processes, providing molecular evidence of potential host modulation of microbial metabolism. Together, these results reveal that oysters actively regulate their calcifying fluid pH over short timescales, and the endemic microbiome metabolic responses can yield metabolites that influence calcifying fluid pH, alkalinity, and ultimately calcification. These data offer a perspective on oyster physiological capacity and, most importantly, the potential role of microbes in oyster calcification. In light of ongoing changes in ocean pH and temperature, oysters provide a model for studying animal–microbial responses to environmental acidification and how their interactions may shape biomineralization.
Continue reading ‘Coexpression among eastern oyster host and microbiome genes suggests coordinated regulation of calcifying fluid chemistry’Unravelling marine benthic functioning shifts under ocean acidification
Published 10 April 2026 Science Leave a CommentTags: algae, biological response, BRcommunity, calcification, community composition, crustaceans, field, Mediterranean, mollusks, morphology, otherprocess, photosynthesis, physiology, porifera, respiration, vents
Ocean acidification (OA) driven by increasing atmospheric CO2 is altering marine biodiversity. However, impacts of OA on ecosystem functioning at the community level, including calcification, primary production and nutrient uptake, remain largely unknown. Here, we conducted community transplant experiments at natural CO2 vents to assess how declining pH affects marine community species composition, biomass, and key ecosystem processes over time. Our results indicate that community shifts caused by declining pH lead to decreased biomass and calcification rates, while photosynthesis and nutrient uptake rates increased. By leveraging OA field model systems and in situ measurements of ecosystem functioning, this study provides critical insights into how OA-induced biodiversity loss reshapes the structure and functioning of temperate marine coastal ecosystems.
Continue reading ‘Unravelling marine benthic functioning shifts under ocean acidification’Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification
Published 26 March 2026 Science ClosedTags: abundance, algae, biological response, BRcommunity, chemistry, field, laboratory, mollusks, morphology, mortality, North Pacific, otherprocess, phytoplankton, reproduction, vents
Highlights
- Natural CO₂ seep systems showed reduced intertidal chiton abundance.
- Adult chitons showed resilience to acidification in field and lab experiments.
- Larval survival and recruitment were strongly impaired under acidified seawater.
- Population declines are linked to early life-stage vulnerability.
- Loss of chitons may reduce grazing and bulldozing, reshaping intertidal communities.
Abstract
Ocean acidification (OA) is a major threat to marine calcifiers; however, the sensitivity across taxa and life stages remains elusive. In this study, we combined field surveys of natural CO₂ seeps with laboratory exposure, transplantation, and larval settlement experiments to assess the effect of OA on chitons, a group of calcifying grazers and bulldozers that play critical roles in the structure of rocky intertidal ecosystems. Field surveys revealed approximately 98.6% reduction in chiton (Acanthopleura loochooana, Liolophura japonica, and Acanthochitona rubrolineata) abundance at acidified habitats (pH 7.6), despite greater microalgal food availability and no detectable increase in predator abundance. Laboratory CO₂-exposure experiments showed no direct effect of OA on adult A. loochooana survival, which is consistent with the presence of protective structural features in the valves that confer resistance to dissolution. Transplant experiments revealed no evidence of increased adult A. loochooana mortality in the acidified habitats (pH 7.6). In contrast, larvae showed pronounced sensitivity to OA, with acidified seawater (pH 7.6) reducing larval settlement by approximately 81.5% compared to control conditions (pH 8.1); early life stages were the most vulnerable. These findings suggest that OA-associated decline in chiton abundance is mainly mediated by impaired recruitment rather than by direct adult mortality, predation, or food limitation. Given the role of chitons as grazers and bulldozers, their loss could substantially change intertidal community dynamics by decreasing grazing pressure and disturbing algal and microbial assemblages. Our findings underscore the criticality of considering life-stage vulnerability and ecological function when evaluating the ecosystem-level consequences of OA.
Continue reading ‘Resilient adults but vulnerable larvae: demographic pathways of chiton decline under ocean acidification’Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change
Published 24 March 2026 Science ClosedTags: biological response, BRcommunity, corals, globalmodeling, modeling, multiple factors, temperature
The ocean is undergoing significant changes, including warming, acidification, and deoxygenation, which pose great challenges to marine biodiversity. However, most models projecting the impacts of climate change on marine species overlook predictor variables critically meaningful for species’ ecologies such as pH and dissolved oxygen. The recent release of high-resolution projections of different future climate-change scenarios offers the opportunity to explore species redistribution under multiple threats beyond ocean warming. Accordingly, we conducted a global comparative analysis to study the impact of incorporating predictor variables describing pH and dissolved oxygen into marine species distribution models. We used models trained for 268 cold-water coral species to project potential future distributions for different climate and dispersal scenarios over different time periods. We found that, irrespective of scenario or period, models using pH and dissolved oxygen projected 11.5–21.4% higher impacts of climate change than those without them. For instance, by the end of the century under a high emission scenario, models including pH and oxygen projected an average range contraction of 48.2% for cold-water corals under a no-dispersal scenario, compared with a 26.8% contraction projected by models excluding these two predictors. Given the substantial differences in the predicted distribution patterns and the biological importance of these variables, we highlight that researchers should consider more diverse sets of predictor variables when predicting future range shifts for marine biodiversity assessments under climate change.
Continue reading ‘Acidification and deoxygenation matter in assessing redistribution of global cold-water coral biodiversity induced by climate change’Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts
Published 19 March 2026 Science ClosedTags: biological response, BRcommunity, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, phytoplankton, reproduction, temperature
Uncontrolled carbon dioxide emissions from human activities contribute to ocean warming and acidification. These alterations in ocean chemistry threaten marine organisms, such as the true giant clam, Tridacna gigas, which is already imperiled due to overharvesting and habitat destruction. To gain an understanding of the physiological and molecular responses of T. gigas and its symbiotic dinoflagellates to ocean warming and acidification, we subjected juvenile individuals to different treatments simulating predicted seawater pH (7.6 and 8.0) and temperature (28°C, 30°C, 32°C and 34°C) levels for the next century. Juvenile giant clams were able to tolerate sustained exposure to temperatures of up to 32°C and pH as low as 7.6, while exposure to higher temperature (34°C), regardless of pH level, resulted in total mortality after a week. However, symbiosis was compromised even in the sublethal treatments, as indicated by the decrease in Symbiodiniaceae density and changes in symbiont gene expression. Symbionts significantly upregulated genes involved in splicing, translation, fatty acid metabolism, and DNA repair, which may constitute an adaptive response, while downregulating genes involved in photosynthesis and transmembrane transport, suggests impaired transfer of photosynthates to the host. These findings demonstrate the vulnerability of the juvenile T. gigas holobiont to heat stress, highlighting the critical importance of continued conservation and management alongside efforts to mitigate global changes in ocean conditions to safeguard this iconic marine bivalve.
Continue reading ‘Influence of ocean warming and acidification on juveniles of the true giant clam, Tridacna gigas, and its microalgal symbionts’Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves
Published 18 March 2026 Science ClosedTags: biological response, BRcommunity, chemistry, growth, laboratory, mollusks, mortality, North Atlantic, phanerogams
While the accumulation of anthropogenic CO2 in the atmosphere is causing a decline in global ocean pH, many eutrophic estuaries are already experiencing acidification due to accelerated respiration driving the consumption of dissolved oxygen (DO) and production of CO2, decreasing available carbonate ions (CO32-) and threatening marine calcifiers. Here, a novel in situCO2 enrichment system was constructed to examine the effects of coastal acidification on the growth and survival of two species of North Atlantic bivalves (Argopecten irradians and Crassostrea virginica) in two distinct estuarine habitats: a seagrass meadow and an unvegetated sandy bottom in an open water estuary. The in-situ system captured natural diel dynamics as ambient chambers displayed chemistry nearly identical to the surrounding water, while CO2-enriched, acidified chambers maintained a consistent ~Δ 0.3–0.5 pH offset. At the unvegetated sandy bottom site, A. irradians and C. virginica displayed significant reductions in growth and survival in the acidified chambers (pHT = 7.3–7.5; saturation state of aragonite, ΩAr = 0.6–0.9) relative to ambient conditions (pHT = 7.6–7.9; ΩAr = 1.6–2). At the seagrass site, while growth of A. irradians and C. virginica in the acidified treatments (pHT = 7.3–7.7; ΩAr = 0.7) receiving the same delivery of CO2 was, again, significantly slowed compared to the control (pHT = 7.5–8.1; ΩAr = 2 – 2.8), the growth reduction, mortality rates, and levels of acidification were attenuated compared to the sandy bottom experiment, evidencing the ability of seagrass to buffer seawater and serve as a potential acidification refuge for bivalves. Collectively, the novel experimental CO2 enrichment system constructed for this project demonstrates that coastal acidification can have deleterious effects on marine bivalve populations, and that future conditions as well as the habitat refuge offered by seagrasses must be considered when developing management and restoration plans for temperate estuaries.
Continue reading ‘Novel in situ CO2 enrichment system reveals seagrass meadows are a refugium against coastal acidification for North Atlantic bivalves’Multi-level holobiont dysregulation increases the ecological risk of combined ocean acidification and benzo[a]pyrene pollution to the reef-building coral Porites lutea
Published 17 March 2026 Science ClosedTags: archaea, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, prokaryotes, toxicants
Highlights
- Combined ocean acidification and BaP induce holobiont dysregulation, evidencing by a decoupled Symbiodiniaceae proliferation and a collapse of the archaeal Nanoarchaeota-Halobacterota symbiosis.
- The coral host shifts its defense strategy from antioxidant capacity to cellular homeostasis, while the bacterial community increases functional redundancy, revealing a costly acclimation mechanism.
- The multi-level dysregulation demonstrates an underestimated ecological risk, highlighting that current single-stressor risk assessments are inadequate for protecting corals under complex pollution scenarios.
Abstract
Reef-building corals are increasingly threatened by the combined effects of global climate change and localized organic pollutants. However, the holistic impacts of co-exposure to ocean acidification (OA) and benzo[a]pyrene (BaP) on coral holobionts remain poorly understood. Here, we investigated the multi-level responses of the reef-building coral Porites lutea to short-term (7-day) exposure to OA (pH 7.80), BaP (10 µg/L), and their combination, by integrating physiological measurements with microbiome profiling (ITS2 and 16S rRNA). We found that combined stress was associated with a dysregulated response in Symbiodiniaceae, characterized by a significant increase in cell density without a parallel rise in chlorophyll content, suggesting a possible compensatory but inefficient proliferation response. Despite this, the dominant symbiont Cladocopium C15 remained stable. The bacterial diversity increased (e.g., enrichment of Ruegeria and Acanthopleuribacter, decline of Endozoicomonas), which may suggest enhanced functional redundancy, while the archaeal community was significantly restructured, most notably a marked decline of the putative obligate Nanoarchaeota–Halobacterota symbiosis. At the host level, combined stress was associated with suppressed antioxidant enzyme activities (SOD/POD) but upregulated genes related to protein folding (Hsp90) and calcium homeostasis (NCX1, VAMP4). These findings suggest a complex holobiont reconfiguration under combined stress, involving a stabilized core symbiont, altered microbiomes, and a shifted host defense strategy. Our study suggests that the ecological risk of combined OA and organic pollution may not be extrapolated from single-stressor responses, indicating the need to incorporate multi-stressor frameworks into coral reef risk assessments.
Continue reading ‘Multi-level holobiont dysregulation increases the ecological risk of combined ocean acidification and benzo[a]pyrene pollution to the reef-building coral Porites lutea’Marine heatwaves, ocean warming and acidification reshape reef fish gut microbiomes
Published 16 March 2026 Science ClosedTags: biological response, BRcommunity, community composition, field, fish, molecular biology, multiple factors, North Pacific, otherprocess, physiology, prokaryotes, temperature, vents
Extreme climatic events and gradual climate change are increasingly anticipated to interact and reshape ecological communities. However, the combined effects of ocean warming, acidification and marine heatwaves on host‐associated microbial communities and their potential role in host adaptation remain poorly understood. Here, we assessed shifts in gut microbiome communities and their associations with physiological performance in one tropical ( Abudefduf vaigiensis ) and one subtropical ( Microcanthus strigatus ) reef fish species, across three temperate reefs representing natural analogues of climate change: a present‐day baseline (‘cool reef’), a chronically warmed reef (‘warm reef’) and a reef experiencing combined warming and extreme acidification (‘extreme reef’). We also examined gut microbiome changes in A. vaigiensis before and during a severe marine heatwave. A. vaigiensis had lower gut microbiome evenness and diversity at the warm (43% and 44% decrease, respectively) and extreme (38% and 31% decrease) reefs compared to the cool reef, and its gut microbiome community shifted at the extreme reef with a 122% increase in abundance of opportunistic bacteria Vibrio. A. vaigiensis also had lower gut microbiome richness at the warm (42% decrease) and extreme (52% decrease) reefs during the heatwave compared to pre‐heatwave individuals. In contrast, M. strigatus showed higher microbiome evenness (99% increase) and diversity (98% increase) at the warm reef compared to the cool reef; however, these gains were lost at the extreme reef, with microbiome diversity and evenness returning to cool reef levels. Microbiome changes in both species were generally not associated with their physiological performance (protein content, oxidative stress, antioxidant capacity or body condition). Our findings suggest that marine heatwaves, ocean warming and acidification can reshape reef fish gut microbiomes, driving simplification in Abudefduf vaigiensis but distinct restructuring in Microcanthus strigatus . We conclude that climate‐driven microbiome reshuffling may alter host–microbiome relationships and functions in fishes in a future ocean.
Continue reading ‘Marine heatwaves, ocean warming and acidification reshape reef fish gut microbiomes’Stony coral symbioses show variable responses to future ocean conditions
Published 16 March 2026 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, multiple factors, North Pacific, otherprocess, phytoplankton, temperature
Coral reefs support over a quarter of marine species and nearly a billion people worldwide but are also among the ecosystems most threatened by anthropogenic impacts. There is long-standing debate about whether coral symbioses will be disrupted or respond adaptively under future ocean conditions. Using a factorial 2.5-year future-ocean mesocosm experiment across eight coral species representing the major coral lineages, we tracked symbiont community shifts within replicate fragments from the same individual coral. Some corals exhibited stochastic divergence consistent with dysbiosis, whereas others showed deterministic, thermally adaptive shifts. Heat stress generally reduced symbiont diversity and promoted predictable restructuring, supporting deterministic processes under moderate stress but stochastic dysbiosis under extreme conditions. We propose that adaptive and stochastic responses represent endpoints along a continuum of host-orchestrated symbiont sorting. This study bridges coral reef ecology with broader host–microbiome theory, offering an integrated perspective on how symbiotic systems may respond to environmental change.
Continue reading ‘Stony coral symbioses show variable responses to future ocean conditions’Environmental controls and nonlinear responses of the diatom-dinoflagellate ratio in Jiaozhou Bay
Published 13 March 2026 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, North Pacific, otherprocess, phytoplankton
Highlights
- Dia/dino abundance, biomass, and diversity ratios exhibited similar temporal patterns;
- All ratios showed considerable heterogeneity without a consistent distributional trend;
- Dia/dino ratios responded distinctly to DO, nutrients, and their interactions;
- Shifting seawater properties exerted large influence on diatom-dinoflagellate dynamics.
Abstract
Diatoms and dinoflagellates are widely recognized as key indicators of marine ecosystem status and play central roles in ecosystem functioning and biogeochemical cycling. Yet how these two major phytoplankton groups adjust to changing coastal environments, and whether such adjustments occur coherently in different ecological dimensions, remains poorly constrained. Hence, we studied the temporal and spatial dynamics of diatom-dinoflagellate (dia/dino) ratios in Jiaozhou Bay during 2021 and 2024, integrating abundance-, carbon biomass-, diversity-, and richness-based metrics. Although abundance, biomass, and diversity ratios exhibited broadly similar temporal trajectories, the richness ratio displayed an opposite pattern, highlighting a decoupling between numerical dominance and species composition. Spatially, all four ratios exhibited significant heterogeneity, without a consistent nearshore-offshore gradient, reflecting complex local regulation. Correlation analyses revealed distinct controls on dia/dino ratios. The abundance ratio increased under conditions of elevated dissolved inorganic nitrogen (DIN) and reduced dissolved oxygen (DO), whereas the diversity ratio was associated with high DIN and low dissolved inorganic phosphorus (DIP). In contrast, the carbon biomass ratio was primarily linked to reduced DO and lower pH, while the richness ratio responded most strongly to the combined influence of low DO and elevated DIP. These contrasting responses indicated that dia/dino ratios captured different facets of phytoplankton community reorganization rather than reflecting a single environmental driver. Overall, our results suggested that the balance between diatoms and dinoflagellates in Jiaozhou Bay emerged from the coupled and nonlinear interactions among nutrient availability and oxygen dynamics. This study highlighted the dia/dino balance as an integrative indicator of coastal ecosystem condition and implied the importance of considering multiple ecological dimensions when assessing phytoplankton responses to ongoing eutrophication and environmental change.
Continue reading ‘Environmental controls and nonlinear responses of the diatom-dinoflagellate ratio in Jiaozhou Bay’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’Persistence of coral reef structures into the twenty-first century
Published 2 March 2026 Science ClosedTags: biological response, BRcommunity, corals, review
Coral reefs provide important socioecological services but are vulnerable to climate change, which shifts the balance between the production and erosion of calcium carbonate (CaCO3). In this Review, we summarize understanding of reef accretion, describe the mechanisms of carbonate production and erosion, and consider the effects of future ocean warming and acidification on key reef-building and eroding taxa. The combined stressors of climate change substantially reduce net carbonate production, with a more pronounced effect on calcifying algae than corals. However, declining coral cover driven by marine heatwaves and mass bleaching will probably be the dominant determinant of future reef carbonate budgets, and thus only reefs with thermally adapted populations are predicted to maintain the ability to sustain positive CaCO3 production under climate change, even if calcareous algal cover increases. As carbonate budgets become net negative in the future, the longevity of pre-existing reef frameworks remains unknown and understudied owing to the timescales required to meaningfully assess framework removal rates. Improving estimates of the rates of biologically driven framework loss and chemical dissolution will also be important in better predicting future reef persistence. Key knowledge gaps exist in understanding the effects of deoxygenation on coral reefs, as well as the influence of climate change on understudied sediment-producing taxa such as foraminifera and tropical molluscs.
Continue reading ‘Persistence of coral reef structures into the twenty-first century’Ocean acidification reduces diatom and photosynthetic gene abundance on plastic in an coastal bay mesocosm experiment
Published 25 February 2026 Science ClosedTags: abundance, biological response, BRcommunity, community composition, laboratory, mesocosms, molecular biology, North Pacific, otherprocess, phytoplankton, prokaryotes
Discarded plastics are accumulating in the global ocean and posing threat to marine life. The plastisphere – the community colonizing plastic surfaces – profoundly influences plastic’s environmental behavior, affecting its degradation and entry into marine food webs. Ocean acidification (OA) resulted from anthropogenic CO2 emissions, is also threatening marine ecosystems, but the effect of OA on the structure and ecological function of the plastisphere community remains poorly understood. Here, using a mesocosm experiment, we investigated the effects of OA on the plastisphere colonizing floating PET plastic bottles. The study was conducted using subtropical eutrophic coastal water from Southern China under two CO2 conditions: increased CO2 to 1000 μatm (HC) and ambient CO2 410 μatm (LC). Metagenomic sequencing of the plastic samples, after exposure for 32 days, showed striking changes in relative abundance of eukaryotes and bacteria caused by HC. There was a 75.3 % decrease in eukaryote read abundances at high CO2, most strikingly a 95.6% decrease in the relative abundance of diatoms. In addition, the relative abundance of genes involved in photosystem II light reactions and pigment synthesis decreased under high CO2 conditions. This suggests that OA could reduce the photosynthetic potential within the plastisphere. Shifts in plastisphere community structure and potentially diminished photosynthesis under OA could influence the food chains within plastisphere, plastic degradation, transportation, and carbon cycle involving plastics. Overall, our results suggest that OA can alter the functional ecology of the plastisphere, with potential implications for marine biogeochemical processes and food web dynamics in subtropical eutrophic coastal water.
Continue reading ‘Ocean acidification reduces diatom and photosynthetic gene abundance on plastic in an coastal bay mesocosm experiment’Ocean acidification modifies site fidelity and patterns of seagrass habitat use by a herbivorous fish
Published 25 February 2026 Science ClosedTags: algae, biological response, BRcommunity, field, fish, Mediterranean, morphology, performance, physiology, vents
Ocean acidification (OA), characterized by changes in seawater chemistry and a concomitant decline of pH due to the uptake by seawater of the atmospheric CO2, will profoundly shape marine ecosystems. The lower pH/higher pCO2 can act negatively (as a stressor for organisms with a calcareous exoskeleton) or positively (as a direct resource for primary producers like macrophytes). Consequently, herbivores may indirectly benefit from OA counteracting the direct negative effects of living under high pCO2/low pH conditions. Here, we investigated how OA may influence site fidelity, habitat use, and trophic behaviour patterns of Sarpa salpa, the main herbivorous fish associated with Posidonia oceanica meadows in the north-western Mediterranean Sea. We assessed if and how OA influences the habitat use of S. salpa by comparing natural tags, in otoliths and muscle tissues, between CO2 vents and reference pH sites. We did not find differences in otolith elemental composition and shape among fish exposed to different pH conditions (CO2 vent vs ambient pH sites). However, otolith isotopic signatures differed between life stages (young vs sub-adults), consistent with the variations observed in seawater-dissolved inorganic carbon across sites. Finally, comparisons of the nutritional value marine vegetation (macroalgae, P. oceanica, epiphytes) showed that P. oceanica and epiphytes were more nutritious at CO2 vents, along with increased consumption by S. salpa. This trophic separation indicates that S. salpa spent more time exploiting the trophic resources in the CO2 vents. Together, our findings shed new light on plant–herbivore interactions within P. oceanica meadows under future OA scenarios.
Continue reading ‘Ocean acidification modifies site fidelity and patterns of seagrass habitat use by a herbivorous fish’Indo-Pacific coral reef sponge diversity declines under predicted future ocean conditions
Published 19 February 2026 Science ClosedTags: abundance, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, multiple factors, North Pacific, otherprocess, porifera, temperature
Future oceans are predicted to favor groups like sponges over calcifying taxa such as scleractinian corals. Here, we test this hypothesis by examining the development of coral reef communities in experimental mesocosms over 23 months. 85 sponge species among the calcifying class Calcarea (~33%), and non-calcifying Demospongiae (~60%) and Homoscleromorpha (<10%) recruited to warming (+2°C), acidification (-0.2 pH), and warming+acidification (+2°C, -0.2 pH) future ocean treatments. The diversity of calcifying sponges was unimpacted across any treatment, whereas non-calcifying classes showed greatest declines. 57-66% of demosponges decreased under future ocean conditions, and homoscleromorphs were entirely absent from acidified treatments. Through the sponge loop, sponges play a fundamental role in coral reef nutrient cycling, and altered coral reef community composition likely has functional consequences. This study challenges the assumption that non-calcifying species are less impacted and highlights the importance of understanding how community composition may alter ecosystem functioning under future ocean conditions.
Continue reading ‘Indo-Pacific coral reef sponge diversity declines under predicted future ocean conditions’Seaweeds (Ulva, Gracilaria) significantly increase the growth rates of North Atlantic oysters, scallops, and clams grown in an aquaculture setting
Published 17 February 2026 Science ClosedTags: algae, biological response, BRcommunity, chemistry, fisheries, laboratory, mitigation, mollusks, morphology
Highlights
- Seaweeds significantly increased the growth rates of oysters by 20–70%, of clams by 60–70%, and of scallops by 130–140%.
- Seaweeds caused significant increases in pH, DO, and the saturation state of calcium carbonate (Ω).
- Seaweeds caused a significant increase in the concentrations of suspended chlorophyll a.
- Co-culture of seaweeds with bivalves accelerates the growth rate of bivalves by increasing pH, DO, Ω, and food availability.
Abstract
While bivalve populations are threatened by climate change stressors including ocean acidification and hypoxia, the photosynthetic activity of seaweeds can raise the pH and dissolved oxygen (DO) of seawater, combatting these stressors. Here, three commercially important North Atlantic bivalves (Eastern oysters, Crassostrea virginica; hard clams, Mercenaria mercenaria; bay scallops, Argopecten irradians) were grown in the presence and absence of two common seaweeds (Ulva sp. and Gracilaria sp.) in replicated 300 L outdoor aquaculture tables with flow-through seawater. Environmental conditions including pH, DO, and chlorophyll a were continuously monitored and levels of dissolved inorganic carbon and the complete carbonate chemistry of seawater were quantified. The presence of seaweeds significantly increased shell- and tissue-based growth rates of oysters by 20–70%, of clams by 60–70%, and of scallops by 130–140% (p < 0.05) with both seaweeds being similarly effective. Both seaweed species caused significant increases in pH, DO, and the saturation state of calcium carbonate (Ω) during the day (p < 0.05) whereas differences at night were muted with night-time Ωaragonite levels being at or below saturation in all treatments. In some experiments, the presence of seaweeds caused a significant increase in the concentrations of suspended chlorophyll a, suggesting that seaweeds increased the total amount and diversity of food available to bivalves. Collectively, this study demonstrates that the co-culture of seaweeds with bivalves in a land-based aquaculture setting can significantly accelerate the growth rate of bivalves by increasing pH, DO, Ω, and food availability.
Continue reading ‘Seaweeds (Ulva, Gracilaria) significantly increase the growth rates of North Atlantic oysters, scallops, and clams grown in an aquaculture setting’Carbon concentration mechanisms in Canary Islands macroalgae and their implications for future benthic community structure under ocean acidification
Published 12 February 2026 Science ClosedTags: algae, biological response, BRcommunity, community composition, laboratory, North Atlantic, otherprocess, physiology, primary production, respiration, vents
In recent decades, due to the anthropogenic CO2 concentration increase in the atmosphere, the chemistry of seawater has been seriously altered, producing the phenomenon known as Ocean Acidification (OA). Of all the dissolved inorganic carbon (DIC) present in seawater, only 1% is in the form of CO2. However, if anthropogenic CO2 emissions to the atmosphere continue, it will no longer be a limiting resource. Part of the response of marine photosynthetic organisms to these changes depends on their carbon physiology. The presence and effectiveness of carbon concentration mechanisms (CCM) can define the production and growth of macroalgae under OA conditions. Although CCMs are not essential when the seawater concentration of inorganic carbon is high, species that do not use them can see their performance improved. Our goal was to determine the presence or absence of CCMs in a total of 19 species of common macroalgae in the Canary Islands through a pH drift experiment and to establish their primary production rates through incubations and measurements of the O2 variation. Samples of each species were incubated during 8, 24 and 32 h in isolated containers and under controlled lighting and temperature conditions. Of the 19 species studied, 11 presented CCM and 8 did not present CCM. Five of the eight species that did not show the presence of CCMs in the present study are present in the CO2 seeps of Fuencaliente and one of them, H. scoparia is a dominant species.
Continue reading ‘Carbon concentration mechanisms in Canary Islands macroalgae and their implications for future benthic community structure under ocean acidification’Summary of ocean acidification data collected by the National Coral Reef Monitoring Program in the U.S. Pacific Islands, 2021—2023
Published 10 February 2026 Newsletters and reports ClosedTags: biological response, BRcommunity, chemistry, corals, field, North Pacific, primary production
Coral reefs are among the most biologically diverse and economically valuable ecosystems on earth. They provide billions of dollars annually in food, jobs, recreation, coastal protection, and other critical ecosystem services (Brander & van Beukering, 2013; Costanza et al., 2014). However, these ecosystems are also among the most vulnerable to ocean acidification (OA). Even under the most optimistic model projections, increasing atmospheric and seawater carbon dioxide concentrations are likely to occur over the next few decades, decreasing seawater pH and reducing the availability of the carbonate ion (CO32-) building blocks that corals and other marine calcifiers use to construct reef habitat (Chan & Connolly, 2013; Jiang et al., 2023). OA threatens the persistence of coral reefs by reducing rates of coral and crustose coralline algae (CCA) calcification and accelerating rates of bioerosion, thereby lowering net production of calcium carbonate (CaCO3) and compromising the structural complexity and integrity of three-dimensional reef habitat (Cornwall et al., 2021; Hill & Hoogenboom, 2022). As a result, many of the ecological, economic, and cultural values offered by coral reefs could be significantly impacted by OA over the next century.
NOAA’s National Coral Reef Monitoring Program (NCRMP) provides a framework for long-term, national-level monitoring of the U.S.-affiliated coral reef areas. Funded jointly by the NOAA Coral Reef Conservation Program and Ocean Acidification Program, NCRMP assesses the status and trends of U.S. coral reef ecosystems and supports the management of the nation’s reefs (NOAA Coral Program, 2021). NCRMP’s long-term monitoring of OA and related coral reef ecosystem responses (NCRMP-OA) evaluates patterns and trends in carbonate chemistry and key ecosystem indicators across gradients of biogeography, oceanographic conditions, habitat types, and human impacts. These data sets are used to inform the efficacy of place-based coral reef management in close collaboration with federal, state, and jurisdictional partners.
To assess the progression of OA and impacts on coral reef ecosystems in the U.S. Pacific Islands, NCRMP-OA monitoring includes the following objectives:
- Conduct carbonate chemistry sampling to monitor spatial variability and temporal change in pH, aragonite saturation state (Ωar), and other carbon system parameters;
- Conduct diel carbonate chemistry water sampling and oceanographic instrument deployments at select sites;
- Conduct census-based carbonate budget assessments to estimate rates of coral reef biological carbonate production and erosion.
This report summarizes the monitoring effort and results from 2021–2023 NCRMP-OA sampling and surveys. Additional NCRMP environmental, benthic, and fish data are not included in this report, but they can be accessed at the links provided in the Data Availability section.
Continue reading ‘Summary of ocean acidification data collected by the National Coral Reef Monitoring Program in the U.S. Pacific Islands, 2021—2023’Assessing sponge resilience to ocean acidification in natural reef environments
Published 28 January 2026 Science ClosedTags: biological response, BRcommunity, community composition, field, otherprocess, photosynthesis, porifera, prokaryotes, respiration, South Pacific, vents
Highlights
- Sponges are key components of coral reefs globally providing a range of important functional roles.
- We used in situ incubation chambers to measure chlorophyll concentrations, oxygen fluxes and microbial communities for two common Indo-Pacific sponge species (Melophlus sarasinorum and Neopetrosia chaliniformis) at a natural CO2 vent (pHT 7.6–7.7) and control site in Papua New Guinea.
- We found little evidence for any physiological differences between vent and control sponges, and no differences in the overall microbial communities
- Overall, our results support the emerging evidence that heterotrophic sponges will likely be resilient to future ocean acidification.
Abstract
Sponges are key components of coral reefs globally providing a range of important functional roles. While sponges are under threat from the impacts of global climate change, there is an emerging picture of sponge tolerance to ocean acidification (OA). However, to date all physiological studies on sponge tolerance to OA have been under ex-situ experimental conditions and only for a limited number of sponge species. Instead, here we used in situ incubation chambers to measure chlorophyll concentrations and oxygen fluxes for two common Indo-Pacific sponge species (Melophlus sarasinorum and Neopetrosia chaliniformis) at a natural CO2 vent (pHT 7.6–7.7) and control site in Papua New Guinea. We also explored differences between the sponge microbial community composition between control and vent locations for N. chaliniformis. We found very low concentrations of chlorophyll in both species, compared to other sponges, suggesting these species are largely heterotrophic. We also found little evidence for any physiological differences between vent and control sponges, and no differences in the overall microbial communities, except some specific microbes. Overall, our results support the emerging evidence that heterotrophic sponges will likely be resilient to future ocean acidification.
Continue reading ‘Assessing sponge resilience to ocean acidification in natural reef environments’
