Marine microorganisms underpin primary production, biogeochemical cycling and host-associated symbioses, supporting climate regulation, coastal protection, fisheries and other ecosystem services. Rapid global change, including ocean warming and marine heatwaves, acidification, deoxygenation, eutrophication, pollution and overuse reshape microbial communities and their functions across marine habitats. These changes can alter carbon, nitrogen and sulfur cycles, promote microbialization and harmful algal blooms, disrupt host–microbiome associations and modify pathogen and antimicrobial resistance dynamics, collectively amplifying the ecological and societal impacts of global change. This Review frames marine microbiomes as cross-scale mediators that translate external pressures, including climate change, pollution, eutrophication and habitat degradation, into altered microbial metabolism, biogeochemical fluxes, host-associated health outcomes, ecosystem service consequences and broader One Health risks. We synthesize shared mechanisms and cross-habitat patterns, highlight cases in which microbiome interventions and stewardship could mitigate impacts and/or accelerate recovery, and outline management options ranging from the reduction of local stressors to emerging microbiome stewardship approaches in ecosystem restoration. Building upon this, we outline pathways for embedding marine microbiome science into globally coordinated One Health strategies, operational management protocols and financing frameworks that align economic incentives with long-term ecosystem and public health outcomes.
Continue reading ‘Global change reshapes marine microbial communities, functions and One Health outcomes’Posts Tagged 'respiration'
Global change reshapes marine microbial communities, functions and One Health outcomes
Published 10 November 2026 Science Leave a CommentTags: biogeochemistry, biological response, community composition, corals, nitrogen fixation, otherprocess, photosynthesis, physiology, phytoplankton, policy, porifera, primary production, prokaryotes, respiration, review, socio-economy
Metabolic dynamics of an offshore coral reef in the central Red Sea: observations from autonomous sensors
Published 9 November 2026 Science Leave a CommentTags: abundance, algae, biogeochemistry, biological response, calcification, chemistry, community composition, corals, dissolution, field, methods, otherprocess, photosynthesis, physiology, porifera, primary production, Red Sea, respiration
Abstract
Coral reefs are increasingly threatened by local and global stressors. Traditional visual reef monitoring methods are time-intensive and provide only a snapshot of reef condition. Recent efforts aim to measure reef metabolism, or the balance of net community production (NCP) and net community calcification (NCC), as coral reef carbonate budgets shift globally toward declining NCC and greater NCP influence. Resolving these metabolic changes requires comprehensive, high-resolution biogeochemical measurements unattainable by traditional sampling alone. This work reports the novel multi-month deployment of a high-resolution, autonomous total alkalinity (TA) sensor alongside pH, partial pressure of CO2, and dissolved oxygen (DO) sensors at Cement Wreck, a central Red Sea offshore reef. Observations from the back reef and fore reef revealed strong diel variability and distinct reef-zone biogeochemical dynamics linked to contrasting benthic compositions. On the back reef, pH and DO were tightly coupled and closely matched a Redfield-based model (𝑅2=0.943), while the fore reef relationship was weaker (𝑅2=0.145). TA observations allowed characterization of the back reef carbonate system, with TA–DIC stoichiometry yielding a slope of 0.26, indicating NCP accounted for approximately 87% of observed carbonate system variability. Compared to global reefs, Cement Wreck exhibits high % NCP contribution. However, the observed 2023 TA–DIC slope closely matches those from Red Sea observations from 1997 to 2013, suggesting that while reefs around the world shift, Red Sea reefs like Cement Wreck represent a persistent metabolic state. Scaled-up autonomous deployments, like the one presented here, will better enable predictions of global reef health in future conditions.
Plain Language Summary
Globally, coral reefs are threatened by rising temperatures, changes in seawater chemistry, pollution, and overfishing. The health of coral reefs is traditionally monitored by reef community composition through visual analysis, however changes in surrounding seawater chemistry can provide insight into reef processes and holistically monitor reef health. Here, we deploy a newly developed total alkalinity (TA) sensor, alongside commercially available pH and oxygen sensors on a coral reef in the Red Sea. Autonomous sensors allow the collection of high-resolution data on reef seawater chemistry, including daily cycles and changes over time, with a cost per data point much lower than traditional discrete samples. Furthermore, the TA sensor allows us to evaluate the relative balance between the reef-building processes and reef-eroding processes occurring, which are important parameters when evaluating a reef’s present and future health. We found that the reef studied here was strongly influenced by organic production, and that this signal closely matched Red Sea observations from the last 25 years. This suggests that some Red Sea reefs may represent a persistent metabolic state rather than a recent shift. The Red Sea lacks high-resolution carbonate-system observations, and this deployment contributes to baseline understanding of Red Sea reef metabolism and carbonate budgets.
Continue reading ‘Metabolic dynamics of an offshore coral reef in the central Red Sea: observations from autonomous sensors’Effects of ocean acidification on the energetics and larval development of a coastal fish, the California grunion (Leuresthes tenuis)
Published 6 November 2026 Science Leave a CommentTags: adaptation, biological response, fish, growth, laboratory, morphology, mortality, North Pacific, otherprocess, performance, physiology, reproduction, respiration
The burning of fossil fuels has increased atmospheric CO₂ at an unprecedented rate. The world’s oceans have absorbed much of this carbon dioxide, resulting in a decrease of pH and an increase in the partial pressure of CO2 in seawater in a process referred to as ocean acidification. Ocean acidification (OA) can cause a variety of detrimental effects on the physiology and ecology of larval fishes. Despite a preponderance of negative effects, studies of how OA affects the early life stages of fishes have produced mixed results and have tended to focus on a limited set of responses. In this study, I tested the effects of OA on energy intake, as measured by feeding rate, and energy expenditure, as measured by metabolic rate, then compared these results to growth and development in the California grunion (Leuresthes tenuis). I also created family groupings to analyze genetic variation underlying these responses. My pCO2 treatments ranged from a control with a central value of 550 μatm, followed by 1080 μatm, 1760 μatm, and 2820 μatm. Each experiment lasted for a period of 12 days, and I ran a total of 12 experiments. Within an experiment, measures of metabolic rate, feeding rate, growth, and development were conducted multiple times. Mortality rates were measured continuously. By analyzing the similarities in the responses of related larvae to CO2, I was able to estimate broad sense heritability’s for metabolic rate, feeding rate, growth, and mortality. I found that at 6-days post hatch, larvae developing in high CO2 conditions exerted significantly more energy on routine metabolic rate. This increase in energetic expenditure with CO2 was not matched by an increase in feeding. Paradoxically, however, growth in mass had a positive relationship with CO2. To explore the consequences of these results, I examined development via allometric analysis of organ growth. I found that the relative growth of the eyes and stomachs of larvae were significantly slower when larvae developed under high pCO2 conditions. Furthermore, I found that both growth and metabolic rates showed significant genetic variation in sensitivity to OA, suggesting considerable evolutionary potential in these traits. I also present evidence that maternal effects are highly influential within the first 6 days after hatch. Overall, my results suggest that OA can cause both an energy deficit and abnormalities in the development of California grunion. The developmental abnormalities observed may be a symptom of an allocation of resources that prioritizes growth at the expense of internal organ development. These changes are likely to have long-term effects on recruitment in natural populations. Additionally, our results suggest that there is appreciable standing genetic variation within the population for the phenotypes studied here.
Continue reading ‘Effects of ocean acidification on the energetics and larval development of a coastal fish, the California grunion (Leuresthes tenuis)’A microRNA catalogue for red abalone larvae reveals developmental and acidification-associated abundance patterns
Published 6 November 2026 Science Leave a CommentTags: biological response, laboratory, molecular biology, mollusks, North Pacific, physiology, reproduction, respiration
Larval development in marine mollusks requires coordinated gene regulation and is particularly sensitive to ocean acidification, yet post-transcriptional regulation remains poorly characterized in non-model gastropods. We characterized the microRNA (miRNA) repertoire and respiratory response of red abalone (Haliotis rufescens) larvae reared at pH 8.0 and 7.6. Small-RNA sequencing was performed at the trochophore (24 h post-fertilization, hpf) and competent veliger (110 hpf) stages, with three biological replicates per stage and pH treatment, while oxygen consumption was measured at 24, 48, 60, and 110 hpf. Genome-anchored annotation identified 147 precursor loci encoding 117 distinct mature miRNA sequences, including 70 matching reference databases and 47 candidate novel miRNAs. The developmental stage was the predominant source of variation in miRNA abundance, with the first principal component explaining 87.3% of the variation, whereas acidification affected a comparatively small subset of miRNAs. Cumulative oxygen consumption from 24 to 110 hpf was 57% higher at pH 7.6 than at pH 8.0. Both intergenic and intragenic miRNAs contributed to the acidification-associated response, with no significant preferential representation of either genomic-origin class. Computational predictions link pH-responsive miRNAs to genes associated with aerobic metabolism, morphogenesis, biomineralization, chromatin regulation, and stress responses. Because these miRNA–target relationships are computational predictions and the physiological and molecular measurements were not biologically paired, they do not establish a direct regulatory relationship. These results provide the first larval miRNA catalogue for H. rufescens and identify developmental- and acidification-associated miRNA abundance patterns and candidate miRNA–target relationships for future functional validation.
Continue reading ‘A microRNA catalogue for red abalone larvae reveals developmental and acidification-associated abundance patterns’Community metabolism generates chemical legacies that alter coral physiology
Published 3 November 2026 Science Leave a CommentTags: biogeochemistry, biological response, communityMF, corals, field, mesocosms, multiple factors, photosynthesis, physiology, primary production, respiration, South Pacific
Coral reefs are among the world’s most diverse ecosystems and contribute substantially to ocean productivity and the carbon budget. Disturbances are shifting reefs to altered community states, yet how these new communities indirectly alter organismal physiology by modifying the local biogeochemical environment remains largely unknown. We investigated this biogeochemical feedback in a 25-d mesocosm experiment in Mo’orea, French Polynesia. We exposed the common coral Porites rus to the biogeochemical environments generated by three distinct communities representative of recent benthic states in this system: coral-, macroalgae-, and crustose coralline algae-enriched relative to a seawater-only control. While net community production was similar among communities, net community calcification was lowest in the macroalgae-enriched state. Across treatments, community metabolism drove changes in the organic and inorganic carbon pool, with net community production increasing both pH and dissolved organic carbon. Using structural equation modeling, we tested how these community-generated chemical legacies propagated through coral physiology. Elevated pH increased chlorophyll a content, which increased endosymbiont density, tissue biomass, gross photosynthesis, and respiration through a series of indirect pathways. Dissolved organic carbon had no detectable effect on downstream corals at 25 d. These results reveal a mechanistic pathway linking disturbance-driven shifts in benthic communities to coral performance. Altered community metabolism modifies local carbon chemistry, which reshapes symbiont physiology and ultimately influences host metabolic function. By identifying the pathways through which community states engineer their chemical environment, this study provides a framework for predicting coral performance and ecosystem trajectories as reefs transition away from coral-enriched states.
Continue reading ‘Community metabolism generates chemical legacies that alter coral physiology’Surviving together: evolutionary dependency, community dynamics, and mortality in marine microbial communities
Published 26 October 2026 Science ClosedTags: abundance, adaptation, biological response, community composition, growth, laboratory, light, molecular biology, mortality, multiple factors, nutrients, otherprocess, photosynthesis, physiology, phytoplankton, primary production, prokaryotes, reproduction, respiration, temperature
Oligotrophic regions of the world ocean sustain vast phytoplankton populations despite extremely low nutrient levels. However, the mechanisms governing their coexistence, interdependence, and mortality are poorly understood. This dissertation investigates how evolutionary dependency, community feedback, and regulated cell death (RCD) jointly shape the stability of marine microbial communities using the Prochlorococcus/Parasynechococcus/Alteromonas model system.
In Chapter 1, I argue that the Black Queen (BQ) hypothesis—which posits that microbes lose costly metabolic functions supplied by community partners—provides a unifying framework for understanding phytoplankton ecology. This framework helps resolve longstanding puzzles, including the paradox of the plankton and the evolutionary maintenance of RCD in unicellular organisms. Building on this framework, Chapter 2 uses transcriptomic analysis of Alteromonas in co-culture with picocyanobacteria to demonstrate that community composition induces greater changes in gene expression than pCO₂ alone. Reduced 2-phosphoglycolate/glycolate exudation by Prochlorococcus under elevated pCO₂ may disrupt the helper heterotroph effect underlying this cyanobacterium’s BQ dependency.
Chapter 3 integrates co-culture experiments, RNA-seq, metabolomics, and mathematical modeling to demonstrate that the stable coexistence of Prochlorococcus and Parasynechococcus is maintained by an “Ouroboros network” of feedback loops. In this network, resource competition, carbon exudation, BQ dependency, and possibly RCD collectively stabilize the community across environmental gradients and during adaptation to changing conditions.
Chapter 4 resolves the cellular mechanisms underlying RCD in these cyanobacteria, showing that differences in cell death modes and the number of checkpoint-linked mortality events between taxa are associated with divergent life-history strategies. These findings suggest that carbon released at these checkpoints may shape interactions with helper Alteromonas, linking individual cell death to community-level interdependencies.
In conclusion, these findings converge on a new resolution to the paradox of the plankton: coexistence in resource-limited environments emerges from interdependent metabolic exchanges, feedback, and regulated cell death shaped by multilevel selection. I propose that together, these processes form an “altruistic bargain” in which stability arises from self-constraint rather than competition alone. Because these interactions are environmentally sensitive, climate change, including warming and acidification, may disrupt the dependencies that sustain microbial diversity and ecosystem function in the world ocean.
Continue reading ‘Surviving together: evolutionary dependency, community dynamics, and mortality in marine microbial communities’Physiological responses of Atlantic surfclams (Spisula solidissima) to moderate ocean acidification across thermal regimes
Published 23 October 2026 Science ClosedTags: biological response, chemistry, fisheries, growth, laboratory, mollusks, morphology, multiple factors, North Atlantic, performance, physiology, respiration, temperature
Highlights
- Interactive effects of warming and acidification tested in surfclams.
- Growth, feeding, and metabolic rates measured after 6-week exposure.
- Moderate acidification had limited effects under warming conditions.
- Surfclams showed resilience to near-future ocean acidification.
- Multi-stressor design improves ecological relevance of lab studies.
Abstract
Understanding marine organismal responses to co-occurring climate stressors is critical for predicting changes in ecosystems and commercial fisheries. The Atlantic surfclam supports a major commercial fishery in the Northeastern United States, where ocean warming and acidification are rapidly altering marine habitats. To evaluate how changing ocean conditions may affect bivalve physiology, surfclams were exposed to conditions reflective of ocean warming and acidification, respectively. One-year-old surfclams were exposed to nine conditions in a fully crossed design of temperature (ambient, +2 °C, and + 5 °C) and pH (7.88 ± 0.05, 7.76 ± 0.05, and 7.51 ± 0.07) for six weeks in a flow-through laboratory experiment using natural seawater. We quantified several physiological responses including growth, feeding, digestion, respiration rates, and shell weight and thickness to assess organismal performance across treatments.
Surfclams generally exhibited resistance to moderate ocean acidification across warming, but non-thermally stressful, temperatures. No effects of ocean acidification were observed on surfclam growth or respiration, although other physiological metrics (shell thickness and absorption rate) decreased with decreasing pH at some temperatures. These findings provide experimentally-derived insight into species-specific responses to interacting climate stressors. Further, the experimental design highlights the importance of integrating natural environmental variability into laboratory studies and studying multiple environmental stressors concurrently. This study contributes a basis for refining models of surfclam growth and distribution in potential future climate scenarios, with implications for sustainable fisheries management.
Continue reading ‘Physiological responses of Atlantic surfclams (Spisula solidissima) to moderate ocean acidification across thermal regimes’Ocean warming and acidification reveal transcriptional plasticity in the gastropod Hexaplex trunculus
Published 23 October 2026 Science ClosedTags: biological response, molecular biology, mollusks, multiple factors, performance, physiology, respiration, temperature
Coastal ecosystems, particularly in the rapidly warming Mediterranean Sea, are increasingly impacted by climate change driven by ocean warming and acidification. Calcifying marine invertebrates are especially vulnerable, yet their molecular responses remain poorly understood. Gene expression dynamics in the ecologically and commercially important gastropod Hexaplex trunculus were investigated under simulated scenarios combining elevated temperature and reduced pH. High-throughput RNA sequencing was used to generate a de novo assembly of the foot transcriptome, followed by differential gene expression analyses to characterize molecular responses to individual and interactive stressors under high-emission (RCP 8.5) projections. The foot tissue – central to locomotion, adhesion, and environmental interaction – exhibited pronounced transcriptional changes in genes associated with calcium signaling, ion transport, aerobic respiration, muscle contraction, and transmembrane transport. Ocean acidification emerged as the dominant driver of transcriptional change, inducing substantial shifts in metabolic demand and ion regulatory pathways, which might suggest increased energetic costs and potential functional constraints. The results demonstrate marked transcriptional plasticity in H. trunculus under combined climate stressors. By providing foundational transcriptomic resources for this species and mechanistic insight into its response to projected environmental changes, this study advances the understanding of molecular processes in vulnerable Mediterranean gastropods and informs ecological assessment efforts in rapidly warming marine ecosystems.
Continue reading ‘Ocean warming and acidification reveal transcriptional plasticity in the gastropod Hexaplex trunculus’Carry-over effects of low salinity during embryonic development modulate larval responses to combined salinity-pH stress in an estuarine crab
Published 21 October 2026 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, physiology, reproduction, respiration, salinity
Early life stages of estuarine organisms are exposed to concurrent environmental stressors, but the extent to which embryonic conditions shape larval responses to multiple stressors remains largely unexplored. We evaluated whether salinity during embryogenesis modulates larval responses to combined salinity and pH stress in the estuarine crab Neohelice granulata. Embryos were reared at two salinities (15 and 33), and larvae were subsequently exposed to combinations of pH (8 and 6.9) and salinity (15 and 33). Salinity during embryogenesis did not affect development duration or eye size, but altered other embryonic traits: embryos at low salinity showed higher heart rate, larger egg volume, and increased egg mass at late stages. In larvae, salinity was the main driver, strongly affecting development, survival, and metabolic performance, whereas pH alone had limited or stage-dependent effects. However, their interaction intensified responses, particularly increasing mortality. Low salinity during the larval stage increased intermolt duration and mortality, effects further exacerbated under low pH. The strongest negative responses occurred under combined low salinity and low pH, with delayed development, higher mortality, and reduced oxygen consumption rates. Although low salinity during embryogenesis influenced larval performance under low pH, larval responses were primarily driven by current environmental conditions. These results highlight that co-occurring stressors can outweigh early-life conditioning. Given that low salinity events and acidification frequently co-occur in estuarine systems, their interaction is critical for understanding organismal responses.
Continue reading ‘Carry-over effects of low salinity during embryonic development modulate larval responses to combined salinity-pH stress in an estuarine crab’Asymmetric metabolic responses of rockweed and herbivores reveal seasonal vulnerabilities to warming and acidification
Published 22 September 2026 Science ClosedTags: algae, biological response, BRcommunity, calcification, mollusks, multiple factors, photosynthesis, respiration, temperature
Macroalgal-herbivore interactions are fundamental to the stability of coastal ecosystems and their vulnerability to climate-driven shifts will affect biodiversity and ecosystem functioning. However, the effects of climate change on species interactions may be context dependent and vary by seasonal oceanographic processes. We examined the effects of warming and acidification on an intertidal primary producer foundation species, Silvetia compressa, and its herbivore, Agathistoma eiseni, under differing upwelling regimes in early (low upwelling) and late spring (high upwelling). We measured metabolic rates including photosynthesis, respiration, and calcification after four weeks of exposure to a range of nine pH levels (7.2–8.0) at two temperature levels (16°C, 20°C). Rockweed responded more to acidification than to warming, but showed different seasonal responses, decreasing photosynthetic rates in early spring and increasing rates during late spring. Their snail consumer, however, responded most strongly to temperature, increasing both respiration and calcification rates under warm conditions in late spring. Our findings demonstrate that seasonal differences can modulate responses of macroalgae and herbivores to changing environmental conditions. Warming may increase top-down effects through increased snail metabolism, while acidification affects rockweed production to affect bottom-up forcing. By assessing physiological responses across different ecological regimes, our study advances understanding of how top-down and bottom-up processes interact in intertidal ecosystems under global change.
Continue reading ‘Asymmetric metabolic responses of rockweed and herbivores reveal seasonal vulnerabilities to warming and acidification’Coral acclimatization to novel, co-varying stressors is associated with fitness trade-offs
Published 18 September 2026 Science ClosedTags: adaptation, biological response, calcification, corals, field, morphology, mortality, multiple factors, North Atlantic, oxygen, photosynthesis, physiology, respiration, temperature
Reef-building corals are under pressure to acclimatize and/or adapt to multiple co-occurring stressors, including climate change and declines in water quality. However, their capacity to do so is largely unknown. Yet, some corals naturally persist in habitats with multi-stressor conditions which can provide crucial insight into coral adaptive capacity under future ocean conditions. To assess the role of phenotypic plasticity and local adaptation in coral acclimatory responses to novel conditions, we reciprocally transplanted two coral species (Siderastrea siderea, branching Porites) between an inland bay characterized by multiple, co-varying stressors, including warmer seawater temperatures, higher pollution and more variable temperatures, pH and dissolved oxygen concentrations, and an environmentally less extreme, more stable fringing reef. We measured key phenotypic traits (e.g., calcification, tissue biomass, metabolic rates, chlorophyll concentrations) of all transplant groups after 0, 4 and 12 months. Reef-origin corals demonstrated high plasticity when transplanted to the bay, as both species maintained high survival and calcification, and matched bay natives’ other phenotypic traits. Yet, reef-to-bay transplants of both species had reduced photosynthesis-to-respiration ratios in the bay, highlighting the risk of metabolic trade-offs unless compensated for through increased heterotrophy. Conversely, bay-origin corals had enhanced photosynthetic performance but lower calcification on the reef. Reaction norms provided stronger evidence for environmental specialization in bay-origin than reef-origin corals, which could limit their use as stress-tolerant source corals for reef restoration. Overall, our findings suggest multi-stressor variability may promote specialized genotypes, rather than increased phenotypic plasticity, though this may also depend on predictability of environmental variability.
Continue reading ‘Coral acclimatization to novel, co-varying stressors is associated with fitness trade-offs’Ocean acidification drives species-specific and time-dependent pigment responses in three phytoplankton taxa
Published 9 September 2026 Science ClosedTags: biological response, BRcommunity, growth, laboratory, light, multiple factors, photosynthesis, physiology, phytoplankton, respiration
Phytoplankton are primary producers in marine ecosystems and play a central role in biogeochemical cycles, yet their physiological responses to altered seawater pH vary among taxa and over time. Here, we examined the effects of sustained pH manipulation on pigment composition, growth, and dark respiration in three ecologically important phytoplankton taxa – a diatom (Pseudo-nitzschia spp.), a dinoflagellate (Heterocapsa pygmaea), and a haptophyte (Emiliania huxleyi) – during a 15-day controlled laboratory experiment. Cultures were maintained at pH 8.1, 7.8, and 7.5, representing present-day and enhanced acidification conditions. Responses to pH were species-specific and strongly time-dependent. Growth and cell-specific respiration rates showed relatively small and often transient differences among pH treatments, suggesting short-term metabolic adjustment under altered pH. In contrast, pigment composition exhibited clearer and more consistent pH-related responses, primarily expressed as shifts in temporal patterns rather than uniform directional changes. In Pseudo-nitzschia spp. and H. pygmaea, several key pigments displayed pronounced pH-dependent trajectories, whereas E. huxleyi showed greater temporal variability and weaker separation among pH treatments. Overall, these results demonstrate that photophysiological traits respond sensitively to sustained pH changes even when population-level growth and respiration remain comparatively stable, highlighting pigment composition as a potentially sensitive indicator of short-term phytoplankton acclimation to ocean acidification.
Continue reading ‘Ocean acidification drives species-specific and time-dependent pigment responses in three phytoplankton taxa’Invasive macroalgae exert stronger effects than elevated CO₂ on seagrass (Posidonia oceanica) seedling performance and associated microbiomes
Published 11 August 2026 Science ClosedTags: algae, biological response, laboratory, Mediterranean, mesocosms, multiple factors, oxygen, phanerogams, physiology, primary production, reproduction, respiration
Highlights
- Invasive macroalgae reduced P. oceanica seedling biomass and leaf development.
- Macroalgal invasion depleted carbohydrate reserves in seedling roots and rhizomes.
- Elevated CO2 increased rhizome starch but did not mitigate invasion impacts.
- Root microbiome diversity declined markedly under macroalgal invasion.
- Future CO2 enrichment unlikely to buffer invasion stress at recruitment stage.
Abstract
Seagrass seedlings are key to meadow recovery under global change, as they enable recolonization of degraded areas and provide genetic variability needed for adaptation. While invasive macroalgae increasingly threaten seagrass communities, elevated CO2 has been proposed to enhance seagrass performance and potentially buffer other stressors. Here, we conducted a mesocosm experiment to test the combined effects of two invasive macroalgae (Lophocladia trichoclados and Caulerpa cylindracea) and elevated CO2 on Posidonia oceanica seedlings. CO2 enrichment increased carbohydrate reserves in rhizomes and induced subtle shifts in root-associated microbiomes. In contrast, invasive macroalgae had consistently negative effects on seedling development and physiology and strongly altered both above- and belowground microbial communities. Despite its potential to stimulate seagrass productivity, elevated CO2 did not mitigate the detrimental impacts of invasive macroalgae. These findings indicate that future CO2 conditions may not offset invasion-driven stress at the recruitment stage, highlighting the need for targeted management efforts to limit macroalgal proliferation and support seagrass meadow regeneration.
Continue reading ‘Invasive macroalgae exert stronger effects than elevated CO₂ on seagrass (Posidonia oceanica) seedling performance and associated microbiomes’Ocean acidification alters phytoplankton diversity and community structure in the coastal water of the East China Sea
Published 4 August 2026 Science ClosedTags: biological response, community composition, field, laboratory, mesocosms, North Pacific, otherprocess, physiology, phytoplankton, primary production, respiration
Anthropogenic CO2 emissions and their continuous dissolution into seawater lead to seawater pCO2 rise and ocean acidification (OA). Phytoplankton groups are known to be differentially affected by carbonate chemistry changes associated with OA in different regions of contrasting physical and chemical features. To explore responses of phytoplankton to OA in the Chinese coastal waters, we conducted a mesocosm experiment in a eutrophic bay of the southern East China Sea under ambient (410 µatm, AC) and elevated (1000 µatm, HC) pCO2 levels. The HC condition stimulated phytoplankton growth and primary production during the initial nutrient-replete stage, while the community diversity and evenness in both pCO2 treatments were reduced during this stage due to the rapid nutrient consumption and diatom blooms, and the subsequent shift from diatoms to hetero-dinoflagellates led to a decline in primary production during the mid and later phases under nutrient depletion. HC treatment suppressed the diatom-to-dinoflagellate succession and enhanced the subsequent remineralization of organic matter, thereby facilitating smaller phytoplankton to dominant and sustaining primary production. Our findings indicate that, the impacts of OA on phytoplankton diversity in the coastal water of the southern East China Sea depend on availability of nutrients, with primary productivity and biodiversity of phytoplankton reduced in the eutrophicated coastal water.
Continue reading ‘Ocean acidification alters phytoplankton diversity and community structure in the coastal water of the East China Sea’Experimental evidence of climate change effects on plankton community respiration in European coastal waters: current insights and knowledge gaps in tested disturbances and studied areas
Published 29 July 2026 Science ClosedTags: biological response, community composition, otherprocess, phytoplankton, respiration, review
Plankton community respiration (PCR) plays a central role in aquatic ecosystems, driving the breakdown of organic matter and influencing global carbon cycling through its contribution to the production and consumption of carbon and oxygen. Coastal areas are regarded as metabolic hotspots in the oceans, due to their intense biological and biogeochemical activities. This review synthesizes experimental evidence to explore how environmental constraints and climate drivers affect PCR in European coastal waters. In total, 46 studies were found in which PCR was measured during experiments testing the effects of one or multiple global climate change drivers in European coastal waters. Among them, the majority of experiments focused on changes in temperature, nutrient concentrations and stoichiometry, and/or pH, while other stressors were less studied. In addition to this qualitative synthesis, a quantitative meta-analysis was conducted on warming and acidification experiments, the only drivers for which comparable experimental designs were available. This analysis, based on 19 warming and 6 acidification studies, was used to perform a standardized comparison of effect sizes across studied areas and experimental set-ups. This review highlights critical knowledge gaps, notably regarding non- and understudied areas and understudied interactions between stressors that occurs jointly in ecosystems.
Continue reading ‘Experimental evidence of climate change effects on plankton community respiration in European coastal waters: current insights and knowledge gaps in tested disturbances and studied areas’Water mass-driven variations in primary production and bacterial respiration during the spring bloom in the Fram Strait
Published 23 July 2026 Science ClosedTags: Arctic, biological response, community composition, field, laboratory, modeling, multiple factors, otherprocess, oxygen, photosynthesis, primary production, prokaryotes, regionalmodeling, respiration
Highlights
- Remote sensing indicates declining bloom in cold and developing bloom in warm water
- Primary production peaks in polar and arctic surface water masses
- Bacterial production is coupled to primary production despite thermal sensitivity
- Oxygen-based community respiration is highest in warmer water masses
- Oxygen-based and INT-based respiration estimates differ by an order of magnitude
Abstract
The Fram Strait is the primary oceanic gateway to the Arctic Ocean and has highly dynamic oceanographic conditions. Oceanographic conditions can shape community compositions, which is increasingly shown using molecular studies, but rate measurements remain scarce, especially for respiration in the Arctic Ocean. Here, we assessed primary production (PP), bacterial production (BP), bacterial abundances (BA), and community respiration (CR) using Winkler titrations and in vivo Iodo-Nitro-Tetrazolium (INT) reduction within the upper 50 m across water masses of the Fram Strait that had varying bloom conditions in spring 2021. We complemented in situ observations with remote sensing of sea surface temperature (SST) and chlorophyll-a (SSC) to infer bloom phenology in warm (θ>2°C), intermediate (2>θ>0°C), and cold (θ<0°C) waters using remote sensing machine-learning. In the cold, nutrient-rich surface waters, a subsiding spring bloom was associated with elevated PP, BP, and BA alongside a high temperature sensitivity (Q10) that indicates active microbial turnover. In contrast, the warm Atlantic-influenced waters exhibit a relatively lower PP but moderate cell-specific BP, suggesting bacterial maintenance metabolism under pre-bloom conditions. Notably, bacterial respiration (BR) estimates differed by 5- to 80-fold between the Winkler and in vivo INT methods. Although the true BR likely lies between these estimates, our results highlight the substantial microbial activity and underscore the need for more accurate BR measurements in Arctic studies.
Continue reading ‘Water mass-driven variations in primary production and bacterial respiration during the spring bloom in the Fram Strait’Light and tidal inundation and exposure regulate the sensitivity of estuarine benthic greenhouse gas fluxes to warming and ocean acidification
Published 28 April 2026 Science ClosedTags: biogeochemistry, biological response, Indian, laboratory, light, multiple factors, physiology, primary production, respiration, sediment
Coastal sediments are globally significant sources and sinks of greenhouse gases (GHGs), yet their contributions to climate feedbacks of warming and ocean acidification remain uncertain, in part due to limited understanding of short-term variability. Here, we use a fully factorial laboratory experiment to disentangle how diel light–dark and tidal inundation and exposure interact with warming and elevated pCO2 to regulate benthic fluxes of CO2, CH4, and N2O in estuarine sediments, alongside concurrent changes in benthic oxygen exchange. While warming and pCO2 exerted strong independent effects, their influence was shaped by diel and tidal fluctuations in redox conditions and oxygen availability, reflecting shifts in metabolic balance between primary production and respiration. Light consistently limited CO2, CH4, and N2O emissions through enhanced autotrophic uptake and oxygenation, while dark promoted anaerobic production pathways. N2O showed the greatest sensitivity to the combined effects of climate forcing and redox dynamics. Despite warming-driven stimulation of benthic heterotrophy and the production of all GHGs, CO2 remained the dominant greenhouse gas, with minimal CH4 and N2O fluxes due to the limited organic matter availability within the sediment. This reflects the strong redox controls on CH4 and N2O production, which relies on both oxygen depletion and organic substrate supply. Our findings emphasize that fine-scale temporal variability can significantly shape both the magnitude and climate sensitivity of benthic GHG emissions. Capturing these fine-scale controls is essential for accurately modeling the contributions of estuarine sediments to global GHG budgets and their feedbacks.
Continue reading ‘Light and tidal inundation and exposure regulate the sensitivity of estuarine benthic greenhouse gas fluxes to warming and ocean acidification’Unravelling marine benthic functioning shifts under ocean acidification
Published 10 April 2026 Science ClosedTags: 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’Investigation of the adaptive mechanisms to ocean acidification in Patella species from CO2 vent systems of the Mediterranean Sea
Published 7 April 2026 Science ClosedTags: adaptation, biological response, field, Mediterranean, molecular biology, mollusks, morphology, otherprocess, physiology, respiration, vents
The continuous increase in anthropogenic carbon dioxide (CO2) emissions into the atmosphere is one of the main factors contributing to ocean acidification (OA). In fact, CO2 is partially absorbed by the oceans, where it alters carbonate chemistry and seawater pH, which is expected to decrease from the current level of 8.1 to 7.7 by 2100. OA exerts harmful impacts primarily on calcifying organisms, as it affects the availability of carbonates, which makes their calcareous structures thinner and more fragile. Moreover, several studies have described the detrimental effects of OA across many marine taxa, affecting important physiological and metabolic mechanisms. On the other hand, research conducted at CO2 vent systems, which are volcanic naturally acidified sites, showed that several organisms can survive under acidified conditions through specific tolerance and/or adaptive strategies. Among these organisms, the gastropod Patella spp. is one of the few calcifiers capable of inhabiting naturally acidified sites, such as the Castello Aragonese vent systems at Ischia Island and the San Giorgio vent systems at Sicily Island. Nonetheless, the complex mechanisms that allow survival and potential adaptation of these organisms to natural OA conditions need to be understood. Therefore, this PhD study aimed at investigating the potential molecular, physiological, metabolic, genetic, and epigenetic mechanisms that enable these organisms to tolerate and survive under OA conditions through a stepwise approach. Specifically, this PhD research attempted to answer the following questions: • Does OA entail a stressful condition in resident populations of Patella spp. living at reduced pH conditions, thereby affecting their overall well-being and health status? • Are there specific physiological, metabolic, and biochemical mechanisms that contribute in defining tolerance to OA? • Are limpets genetically adapted to OA? • Is DNA methylation contributing to promote tolerance to OA in limpets? • What is the role of environmental conditions in shaping the response to OA? The first chapter of this thesis considered three Patella species (P. caerulea, P. rustica, and P. ulyssiponensis) collected from the CO2 vent systems of the Castello Aragonese (Ischia Island). This vent system exhibits a natural acidification gradient ranging from ambient pH (N1: pH = 8.1), to intermediate pH (N2: pH = 7.7), and to extremely low pH (N3: pH < 7.4). Resident populations were collected along the gradient and at San Pietro, an additional ambient pH site (pH = 8.1), located at a distance of 4 km from the Castello vent. In addition, a 30-day in situ transplant experiment was conducted using P. caerulea, in order to evaluate the short-term responses induced by OA. Morphometric traits, such as shell length, height, width, and soft-tissue weight, were measured, and a set of biomarkers related to antioxidant system, energy metabolism, neurotoxicity, and biomineralization was applied. For resident populations, P. caerulea showed increased size and energy reserves at the extremely acidified site, likely related to a shift from erect calcified algae to biofilm, or to reduced competition and/or predatory pressure under acidified conditions. Biochemical endpoints measured in both P. caerulea and P. ulyssiponensis were not modified by OA. Conversely, P. rustica exhibited significant modulation of nearly all biochemical parameters, likely due to its different position on the rocky shore, which makes this species more exposed to tidal fluctuations and therefore to an additional source of disturbance, besides OA. Short-term exposure of P. caerulea to OA resulted in a decrease in protein content and an increase in glycogen content at the extremely acidified site, with the induction of superoxide dismutase and glutathione-S-transferase activities at intermediate pH, suggesting the activation of compensatory mechanisms to cope with reduced pH conditions. Overall, results revealed a distinct response to OA of the three species of Patella. Moreover, the increased size and energy-related endpoints observed in P. caerulea and P. rustica highlighted the need to further investigate energy metabolism aspects, in order to better understand the trade-offs between compensatory mechanisms and the energetic cost underlying tolerance to OA. Based on these evidences, the second chapter focused exclusively on P. caerulea, with the aim of deeply investigating metabolic and physiological stress-responses, comparing resident populations of the Castello Aragonese vent systems and transplanted organisms, similarly to the first chapter. Respiration and ammonia excretion rates were measured four times across the year. Additionally, untargeted metabolomics analyses were performed to investigate metabolic pathways potentially involved in response to OA. Only during summer, OA increased respiration rate in limpets from the most acidified site, while simultaneously reduced excretion rates, likely to allocate more energy resources to face the increasing temperature, besides OA. Furthermore, both resident and transplanted populations up-regulated carnitine metabolism, suggesting that OA induced an increase of energy production through β-oxidation and subsequent Krebs cycles. Moreover, several metabolites involved in osmoregulation, oxidative stress, and nucleic acid mechanisms were increased. Overall, results seem to confirm the presence of negative effects and of an energetic cost underpinning tolerance to OA. The third and final chapter investigated the potential influence of phenotypic plasticity, genetic adaptation, and DNA methylation in tolerance to OA in adult and juvenile populations of P. caerulea collected from two CO2 vent systems of the Mediterranean Sea. Adult and juvenile specimens were sampled along the acidification gradient of the Castello Aragonese vent systems of Ischia Island (San Pietro/N1: pH = 8.1; N2: pH = 7.7; N3: pH < 7.4) and from the San Giorgio vent systems of Sicily Island (Patti: pH = 8.1; San Giorgio: pH = 7.8). Following genomic DNA extractions from foot tissue and individual libraries preparation with the NEB Next® Enzymatic Methyl-seq Kit, samples were sequenced on the Illumina NovaSeq 6000 sequencer. Data processing and analyses were conducted on Euler platform mainly using biscuit tool, which enabled to simultaneously extract genomic and epigenomic information from DNA methylation sequencing. Population genomics and epigenomics analyses revealed divergent patterns between the Ischia and Sicily populations. Populations from the Ischia vent revealed marked signs of genomic differentiation, particularly in adults from the intermediate and extremely low pH sites, while reduced differences in DNA methylation levels were detected, especially in adults. These findings suggest a strong signature of purifying selection acting on standing genetic variation, through a within-generation response, likely driven by the more pronounced pH fluctuations occurring at these sites. Conversely, no genomic differentiation was observed between the Sicily populations, but greater differences in DNA methylation were detected between acidified and non-acidified sites at both adult and juvenile stages. These results revealed that this epigenetic mechanism, rather than genomic changes, may play a key role in the response to the milder pH variations of this vent and potentially enhance organisms’ tolerance to OA. In conclusion, this PhD project investigated tolerance to OA in limpets through a holistic approach that, for the first time, integrated morphological, physiological, metabolic, biochemical, genetic, and epigenetic analyses. Overall, findings revealed that Patella spp. has the ability to survive under acidified conditions even though with a physiological and metabolic cost, which could be partially compensated by more favorable environmental conditions. This study further highlights the importance of conducting research in naturally acidified environments, since it allows to formulate more realistic hypotheses about the ability of marine organisms to persist in future changing oceans.
Continue reading ‘Investigation of the adaptive mechanisms to ocean acidification in Patella species from CO2 vent systems of the Mediterranean Sea’
