Ocean acidification (OA) poses significant threats to marine calcifiers through multifaceted physiological disruptions. While bivalve mollusks are particularly vulnerable, the intestinal defense mechanisms against OA-induced stress remain poorly characterized. This study systematically investigated the intimate associations between the organismal physiological toxicity responses and intestinal homeostasis of Chlamys nobilis (C. nobilis) under simulated OA situations (pH 7.3-8.0) to reveal the potential physiological and biochemical damage. The results revealed that acidification stimulated pathogenic bacteria（Mycoplasma）colonization, disrupted microbiota homeostasis, and induced oxidative responses, thereby triggering intestinal inflammation and epithelial damage. Furthermore, the filtration rates and oxygen consumption rates of C. nobilis were significantly decreased in a pH-dependent manner across all the treatments, which might result from the intestinal dysfunction and the inhibition of acetylcholinesterase activities. These findings establish a link between OA-induced intestinal dysbiosis and organismal physiology, providing novel insights into the interplay between physiological performance and intestinal homeostasis under OA scenarios. The results advance our understanding of bivalve mollusk adaptation strategies and inform predictive models for its sustainability in acidifying marine ecosystems.
Continue reading ‘Effects of ocean acidification on intestinal homeostasis and organismal performance in a marine bivalve: from microbial shifts to physiological suppression’Posts Tagged 'community composition'
Effects of ocean acidification on intestinal homeostasis and organismal performance in a marine bivalve: from microbial shifts to physiological suppression
Published 25 April 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, mollusks, North Pacific, otherprocess, performance, physiology, prokaryotes, respiration
Long-term successional dynamics and response strategies of harmful algal blooms to environmental changes in Tolo Harbour
Published 18 April 2025 Science ClosedTags: biogeochemistry, biological response, BRcommunity, chemistry, community composition, communitymodeling, field, mitigation, modeling, North Pacific, otherprocess, physiology, phytoplankton, policy
Highlights
- Long-term monitoring reveals significant shifts in harmful algal bloom species and toxin dynamics in Tolo Harbour.
- Government actions reduced nutrient levels, but climate change and organic nutrients influenced HABs’ species succession.
- Number of HABs decreased, meanwhile frequency and types of new toxin species emerged, highlighting complex ecological changes.
- Balanced dual nutrient reduction strategies are essential for controlling HABs and restoring coastal ecosystem health.
ABSTRACT
The production and succession of harmful algae blooms (HABs) are attributed more to excessive nutrient concentrations and unbalanced nutrient stoichiometry than to other environmental drivers as the absence of long-term monitoring data. This study analyzed HABs succession patterns and key drivers in Tolo Harbour from 1986 to 2023, leveraging nearly 40 years of data. Effective governmental measures significantly improved water quality, with dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), 5-day biochemical oxygen demand (BOD5), and Escherichia coli (E. coli) concentrations decreasing by 53%, 80%, 45%, and 59%, respectively. Annual HABs events dropped from 28 to 3, and species diversity declined from 6 to 2. However, toxic species frequency rose from 21% to 46%. Dinoflagellates emerged as dominant initial species, with a shift in secondary dominance from diatoms to ochrophytes and toxin types from diarrhetic shellfish poisoning (DSP) to hemolytic toxins (HT). These shifts likely result from combined human and natural influences. Model simulations confirmed that red tide outbreaks, species succession, and shifts in toxin types were driven by declining pH, rising temperatures, unbalanced nitrogen-phosphorus ratios, organic nutrient increases, and algal antagonism. The study emphasizes the importance of the dual reduction of both DIN and DIP, meanwhile inorganic and organic nutrients, suggesting that overly focusing on or distract from one nutrient (e.g., DIP or DON) could lead to unintended ecological consequences, like the proliferation of rare and toxic species. We highlight the combined impacts of climate change (warming and ocean acidification) and anthropogenic activities (nutrient pollution and eutrophication) on HABs, particularly the number and toxin production. This research links policy changes to HAB dynamics, offering strategic recommendations for managing red tides and contribute novel perspectives on the impact of nutrient reduction in comparable bay ecosystems.
Continue reading ‘Long-term successional dynamics and response strategies of harmful algal blooms to environmental changes in Tolo Harbour’Ocean acidification disrupts the energy balance and impairs the health of mussels (Mytilus coruscus) by weakening their trophic interactions with microalgae and intestinal microbiome
Published 4 April 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, mollusks, North Pacific, otherprocess, performance, physiology, phytoplankton, prokaryotes
Highlights
- Ocean acidification disrupts mussel energy balance by weakening trophic interactions.
- Mussels exposed to acidified conditions show reduced energy gain from microalgae.
- Energy imbalance caused by acidification impairs mussel health and fitness.
- Ocean acidification can threaten mussel farming and marine ecosystem stability.
Abstract
Despite extensive research in the last two decades, exploring the potential mechanisms underlying the sensitivity and resistance of marine organisms to ocean acidification is still imperative. Species interactions can play a role in these mechanisms, but the extent to which they modulate organismal responses to ocean acidification remains largely unknown. Here, we investigated how ocean acidification (pH 7.7) affects energy homeostasis and fitness of mussels (Mytilus coruscus) by assessing their physiological responses, intestinal microbiome and nutritional quality of their food (microalgae). Under ocean acidification, the mussels had reduced feeding rates by 34 % and reduced activities of digestive enzymes (pepsin by 39 %, trypsin by 28 % and lipase by 53 %) due to direct exposure to acidified seawater and increased phenol content of microalgae. Richness and diversity of intestinal microbiome (OTU, Chao1 index and Shannon index) were also lowered by ocean acidification, which can undermine nutrient absorption. On the other hand, energy expenditure of mussels increased by 53 % under ocean acidification, which was associated with the upregulation of antioxidant defence (SOD, CAT and GPx activities). Consequently, energy reserves in mussels decreased by 28 %, which were underpinned by the reduction in protein, carbohydrate and lipid contents. Overall, we demonstrate that ocean acidification could disrupt herbivore-algae and host-microbe interactions, thereby lowering the energy balance and impairing the health of marine organisms. This can have ramifications on the population and energy dynamics of marine communities in the acidifying ocean.
Continue reading ‘Ocean acidification disrupts the energy balance and impairs the health of mussels (Mytilus coruscus) by weakening their trophic interactions with microalgae and intestinal microbiome’Eukaryotic phytoplankton drive a decrease in primary production in response to elevated CO2 in the tropical and subtropical oceans
Published 14 March 2025 Science ClosedTags: biological response, BRcommunity, community composition, field, North Pacific, phytoplankton, primary production
Significance
Marine phytoplankton, which contribute ~45% of global net primary production, are projected to be affected by ongoing ocean acidification (OA). However, the response of phytoplankton to acidification is not well constrained in ultraoligotrophic tropical and subtropical oceans where small (<20 µm) phytoplankton dominate. By conducting onboard microcosm experiments, we found community-level primary production decreased consistently following CO2 enrichment in the North Pacific Subtropical Gyre and northern South China Sea, while no significant changes were observed at the northernmost boundary of the subtropical gyre. Eukaryotic phytoplankton but not cyanobacteria were key drivers of these responses which occur primarily under nitrogen limitation. These findings enhance our understanding of OA impacts on phytoplankton and marine productivity in a changing climate.
Abstract
Ocean acidification caused by increasing anthropogenic CO2 is expected to impact marine phytoplankton productivity, yet the extent and even direction of these changes are not well constrained. Here, we investigate the responses of phytoplankton community composition and productivity to acidification across the western North Pacific. Consistent reductions in primary production were observed under acidified conditions in the North Pacific Subtropical Gyre and the northern South China Sea, whereas no significant changes were found at the northern boundary of the subtropical gyre. While prokaryotic phytoplankton showed little or positive responses to high CO2, small (<20 µm) eukaryotic phytoplankton which are primarily limited by low ambient nitrogen drove the observed decrease in community primary production. Extrapolating these results to global tropical and subtropical oceans predicts a potential decrease of about 5 Pg C y−1 in primary production in low Chl-a oligotrophic regions, which are anticipated to experience both acidification and stratification in the future.
Continue reading ‘Eukaryotic phytoplankton drive a decrease in primary production in response to elevated CO2 in the tropical and subtropical oceans’Climate-driven shifts in Southern Ocean primary producers and biogeochemistry in CMIP6 models
Published 26 February 2025 Science ClosedTags: Antarctic, biogeochemistry, biological response, BRcommunity, chemistry, community composition, modeling, otherprocess, phytoplankton, regionalmodeling
As a net source of nutrients fuelling global primary production, changes in Southern Ocean productivity are expected to influence biological carbon storage across the global ocean. Following a high-emission, low-mitigation pathway (SSP5-8.5), we show that primary productivity in the Antarctic zone of the Southern Ocean is predicted to increase by up to 30 % over the 21st century. The ecophysiological response of marine phytoplankton experiencing climate change will be a key determinant in understanding the impact of Southern Ocean productivity shifts on the carbon cycle. Yet, phytoplankton ecophysiology is poorly represented in Coupled Model Intercomparison Project phase 6 (CMIP6) climate models, leading to substantial uncertainty in the representation of its role in carbon sequestration. Here we synthesise the existing spatial and temporal projections of Southern Ocean productivity from CMIP6 models, separated by phytoplankton functional type, and identify key processes where greater observational data coverage can help to improve future model performance. We find substantial variability between models in projections of light concentration (>15 000 (µE m−2 s−1)2) across much of the iron- and light-limited Antarctic zone. Projections of iron and light limitation of phytoplankton vary by up to 10 % across latitudinal zones, while the greatest increases in productivity occurs close to the coast. Temperature, pH and nutrients are less spatially variable – projections for 2090–2100 under SSP5-8.5 show zonally averaged changes of +1.6 °C and −0.45 pH units and Si* ([Si(OH)4]–[NO3–]) decreases by 8.5 µmol L−1. Diatoms and picophytoplankton and/or miscellaneous phytoplankton are equally responsible for driving productivity increases across the subantarctic and transitional zones, but picophytoplankton and miscellaneous phytoplankton increase at a greater rate than diatoms in the Antarctic zone. Despite the variability in productivity with different phytoplankton types, we show that the most complex models disagree on the ecological mechanisms behind these productivity changes. We propose that a sampling approach targeting the regions with the greatest rates of climate-driven change in ocean biogeochemistry and community assemblages would help to resolve the empirical principles underlying the phytoplankton community structure in the Southern Ocean.
Continue reading ‘Climate-driven shifts in Southern Ocean primary producers and biogeochemistry in CMIP6 models’The nasal microbiota of two marine fish species: diversity, community structure, variability and first insights into the impacts of climate change-related stressors
Published 25 February 2025 Science ClosedTags: biological response, BRcommunity, community composition, fish, laboratory, molecular biology, multiple factors, otherprocess, prokaryotes, temperature
Vertebrate nasal microbiota (NM) plays a key role regulating host olfaction, immunity, neuronal differentiation, and structuring the epithelium. However, little is known in fish. This study provides the first comprehensive analysis of the NM in two marine fish species, the European seabass and the Atlantic cod. Given its direct environmental exposure, fish NM is likely influenced by seawater fluctuations. We analysed the community structure, specificity regarding seawater, and interindividual variability of 32 to 38 fish reared under ambient conditions. Additionally, we conducted an experiment to investigate the influence of acidification and a simplified heatwave on cod NM (3 fish per replicate). High-throughput 16S rRNA sequencing revealed species-specific NM communities at the genus-level with Stenotrophomonas and Ralstonia dominating seabass and cod NM, respectively. This suggests potential habitat- or physiology-related adaptations. The most abundant bacterial genera in seabass NM were also present in seawater, suggesting environmental acquisition. Alpha diversity was highest in Brest seabass NM and variability greatest in Tromsø cod NM. Simulated climate change-related scenarios did not significantly alter cod NM structure. We propose a minimum of 13 cod rosettes per replicate for future studies. This research establishes a foundation for understanding marine fish NM and its response to environmental changes.
Continue reading ‘The nasal microbiota of two marine fish species: diversity, community structure, variability and first insights into the impacts of climate change-related stressors’High-resolution temporal assessment of physicochemical variability and water quality in tropical semi-enclosed bays and coral reefs
Published 24 February 2025 Science ClosedTags: biological response, BRcommunity, chemistry, community composition, corals, field, North Atlantic, otherprocess
Highlights
- Mangrove, seagrass, and coral habitats are at risk from global and local stressors
- We assessed >20 (a)biotic parameters and pollution at high temporal resolution
- Strong diel and seasonal variability was recorded in semi-enclosed bays
- The bays showed higher nutrient levels and ecotoxicological risks than nearby reefs
- A water quality monitoring framework for reef-associated habitats is provided
Abstract
Tropical coastlines featuring mangrove, seagrass, and coral habitats are of immense ecological and socio-economic importance, supporting biodiversity, carbon storage, coastal protection, fisheries, and tourism. However, climate change, coastal development, and low water quality increasingly threaten these interconnected coastal ecosystems, particularly in semi-enclosed bays where the impacts of these stressors are often amplified. Yet, physicochemical conditions are rarely assessed at sufficient temporal resolution (i.e., diel and seasonal variation) and time-integrated pollution monitoring is rarely performed. Here, we used a multi-disciplinary approach to assess >20 abiotic parameters characterizing two mangrove- and seagrass-dominated inland bays and two nearby coral reefs in Curaçao (southern Caribbean) during the cool, dry season and warm, wet season. This was combined with time-integrated pollution monitoring using bioindicators to assess nutrients and trace metal pollution (inland bays only), and passive samplers and bioassays to assess organic chemical pollution (all four sites) during the wet season. This approach revealed a previously undocumented extent of strong diel and seasonal environmental variability in Curaçao’s inland bays, with temperature, pH, and dissolved oxygen frequently reaching values predicted under moderate-to-severe future climate scenarios as outlined by the IPCC (2021). In addition, the inland bays had greater nutrient concentrations (especially ammonium) and potential ecotoxicological risks than the nearby reefs during the wet season due to run-off and anthropogenic activities. These findings emphasize the importance of high-resolution monitoring to understand risks across appropriate temporal scales and establish an environmental baseline against which future monitoring can be benchmarked. Moreover, our study provides a robust water quality assessment framework that can be used by natural resource managers to monitor reef-associated habitats and conserve their high ecological and socio-economic value. Overall, our work highlights the urgent need to improve monitoring, water quality, and protection of these valuable reef-associated habitats.
Continue reading ‘High-resolution temporal assessment of physicochemical variability and water quality in tropical semi-enclosed bays and coral reefs’Carbon dioxide–induced acidification enhances short-lived brominated hydrocarbons production in oligotrophic oceans
Published 18 February 2025 Science ClosedTags: biogeochemistry, biological response, community composition, field, Indian, multiple factors, nutrients, otherprocess, physiology, phytoplankton, South Atlantic
Oceanic emission is a primary source of brominated very short-lived substances (BrVSLs) to the atmosphere, which have important effects on stratospheric ozone chemistry. Marine biogeochemical processes regulating BrVSLs are often sensitive to ocean acidification. Yet, the response of BrVSLs production to acidification remains poorly understood. Herein, the effects of acidification on the production of two main BrVSLs, dibromomethane (CH2Br2) and tribromomethane (CHBr3), were studied by ship-based incubation experiments at three stations in the South Atlantic and Indian Oceans. The average CH2Br2 and CHBr3 concentrations increased by 17.2–58.7% and 14.3–80.3% due to acidification under the in situ nutrient conditions with nutrient and/or iron limitation at the three stations, but the mechanisms driving these increases varied among different regions. The increased bromoperoxidase (BrPO) activity caused by acidification facilitated BrVSLs release in the Eastern Tropical Indian Ocean, where diatoms were dominant. CHBr3 increased due to acidification as a result of enhanced reactivity of dissolved organic matter (DOM) in the Eastern Tropical Atlantic, where dinoflagellates were dominant. Brominated very short-lived substances increased due to acidification as a result of a combined effect of the above two mechanisms in the Benguela Current Coastal with high phytoplankton abundance. Under the nutrient and/or iron addition conditions with nutrient and iron sufficiency, however, acidification did not promote BrVSLs production due to its only minor effect on the BrPO activity and reactivity of DOM, partly because the effect of increased oxidative stress was offset by that of changed phytoplankton composition. Our study provided a basis for future modeling on the impact of acidification on global BrVSLs emissions.
Continue reading ‘Carbon dioxide–induced acidification enhances short-lived brominated hydrocarbons production in oligotrophic oceans’Short-term negative effects of seawater acidification on the rhodolith holobionts metatranscriptome
Published 7 February 2025 Science ClosedTags: algae, biological response, BRcommunity, community composition, laboratory, molecular biology, otherprocess, prokaryotes, South Atlantic
Highlights
- Cyanobacteria dominate the microbial community in living rhodoliths.
- Vibrionales dominate dead rhodolith skeletons.
- Short-term (1 h) acidification affects the microbial community structure.
- Diverse functional genes modulate microbe-host interactions.
Abstract
Rhodolith holobionts are formed by calcareous coralline algae (e.g., Corallinales) and associated microbiomes. The largest rhodolith bank in the South Atlantic is located in the Abrolhos Bank, in southwestern Brazil, covering an area of 22,000 km2. Rhodoliths serve as nurseries for marine life. However, ocean acidification threatens them with extinction. The acute effects of high pCO₂ levels on rhodolith metatranscriptomes remain unknown. This study investigates the transcriptomic profiles of rhodoliths exposed to short-term (96-h) high pCO₂ levels (up to 1638 ppm). Metatranscriptomes were generated for both dead and alive rhodoliths (15.48 million Illumina reads in total). Alive rhodoliths showed an enrichment of gene transcripts related to environmental stress responses and photosynthesis (Cyanobacteria). In contrast, the metatranscriptomes of dead rhodoliths were dominated by heterotrophic (Proteobacteria and Bacteroidetes) metabolism and virulence factors. The rhodolith holobiont metatranscriptomes respond rapidly to short-term acidification (within 1 h), suggesting that these holobionts may have some capacity to cope with acute acidification effects. However, the negative impacts of prolonged ocean acidification on rhodolith health cannot be overlooked. Rhodoliths exposed to low pH (7.5) for 96 h exhibited a completely altered transcriptomic profile compared to controls. This study highlights the plasticity of rhodolith transcriptomes in the face of ocean acidification and climate change.
Continue reading ‘Short-term negative effects of seawater acidification on the rhodolith holobionts metatranscriptome’Submarine groundwater discharge impacts on coastal waters of southeastern Arabian Sea: changes to carbonate chemistry and plankton communities
Published 5 February 2025 Science ClosedTags: biological response, chemistry, community composition, field, Indian, laboratory, otherprocess, phytoplankton
Highlights
- Submarine groundwater discharge impacts on tropical coastal waters were studied.
- Nutrient sourced SGD input stimulate the growth of diatoms in the coastal waters.
- Acidification may alter the balance between plankton communities.
- Long term monitoring studies of interactive effects of potential drivers needed.
Abstract
Submarine groundwater discharge (SGD) is a significant contributor to effect phytoplankton community shift and marine ecosystem changes, yet little information is available about its influence in the Indian coastal waters. This microcosm study assessed the impact of groundwater input on carbonate chemistry changes, plankton community structuring and marine ecosystem dynamics in coastal waters off Kochi, southeastern Arabian Sea (SEAS), southwest India. The relatively high nutrient content (nitrate and silicate) and low nitrate to silicate ratio (N/Si < 1) in the groundwater favoured the growth and fast abundance of diatom species (Thalassiosira sp.). The increased growth rate of diatoms in coastal groundwater additions shifts the community composition towards higher microphytoplankton relative to picoplankton proportion. Increased heterotrophic thecate dinoflagellates such as Protoperidinium species with SGD might become the significant consumers of bloom forming diatoms in the coastal waters. The SGD driven acidification with increased nutrient supply may alter the balance between autotrophic and heterotrophic plankton communities, which becomes intense with the effective increase in atmospheric aerosols and anthropogenic inputs, amplifying the scope of coastal ocean acidification.
Continue reading ‘Submarine groundwater discharge impacts on coastal waters of southeastern Arabian Sea: changes to carbonate chemistry and plankton communities’The response mechanisms of kelp Macrocystis pyrifera holobiont to elevated temperature and CO2 concentration
Published 17 January 2025 Science ClosedTags: algae, biological response, BRcommunity, community composition, laboratory, multiple factors, otherprocess, physiology, prokaryotes, temperature
The kelp Macrocystis pyrifera, a crucial component of marine ecosystems, is significantly impacted by climate change and environmental stresses. Macrocystis pyrifera and its associated bacteria form a holistic functional unit (holobiont), yet the regulatory roles of bacteria in stress responses and acclimation are often overlooked. This study investigates the diversity of M. pyrifera associated bacteria and their chemical interactions under high temperature and elevated CO2 conditions. Our findings indicate that high temperatures significantly reduce associated bacterial diversity, while elevated CO2 does not alter community structure. Key microbial biomarkers identified include Pseudomonas, Sulfitobacter, and Olleya. However, it is unknown how they function in M. pyrifera. In metabolite analysis, we identified 18 metabolites with significant differences. These metabolites included phospholipids, antibacterial compounds, signaling molecules, and various compounds of unclear function. The changes in these compounds are probably connected to how M. pyrifera respond to climate change. These results will enrich the baseline data related to the chemical interactions between the microbiota and M. pyrifera and provide clues for predicting the resilience of M. pyrifera to future climate change.
Continue reading ‘The response mechanisms of kelp Macrocystis pyrifera holobiont to elevated temperature and CO2 concentration’Impacts of climate change on members of shallow water Antarctic communities
Published 16 January 2025 Science ClosedTags: algae, Antarctic, biological response, BRcommunity, community composition, crustaceans, laboratory, mortality, otherprocess, performance, physiology
Human-derived CO2 emissions have lowered the ocean’s pH and increased global temperatures. Low seawater pH can decrease the calcification, growth, and survival of calcifying invertebrates. Furthermore, low pH changes macroalgal growth and stress, possibly altering palatability to consumers. Global warming has decreased sea ice coverage, profoundly influencing photosynthetic organisms by altering subsurface irradiance. Shallow, hard-bottom communities along the Western Antarctic Peninsula are characterized by large macroalgal forests that shelter large numbers of mesograzers. Amphipods and macroalgae have a community-wide mutualistic relationship where macroalgae provide refuge from predatory fish while amphipods remove competing epiphytes. To understand how climate change could impact members of this relationship, macroalgal-associated mesograzers were collected near Palmer Station, Antarctica (64°46′S, 64°03′W) and maintained under three different pH treatments [ambient (pH 8.1), near-future (pH 7.7), and distant-future conditions (pH 7.3)] for 52 days. Total assemblage number and the relative proportion of each species were similar across the treatments, indicating possible resistance to short-term low pH exposure. The amphipods Djberboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were maintained under the pH treatments for 8 weeks. No difference in biochemical composition or survival was found between the treatments for any of the species. However, each species decreased molt activity between the ambient and pH 7.3 treatment. These results suggest that amphipods may maintain their survival in decreased pH by reallocating energy into compensatory behaviors and away from energy-expensive processes like molting. The palatability of the unpalatable Desmarestia menziesii and the palatable Palmaria decipiens were maintained under three pH treatments and then presented to the amphipod Gondogeneia antarctica in a feeding choice assay. Decreased seawater pH generally lowered the consumption of both species, suggesting that acidification may decrease the palatability of these macroalgae to consumers. Finally, biochemical composition, carbon and nitrogen percentages, and C:N were correlated with sea ice indices for the macroalgae D. menziesii, Himantothallus grandifolius, Sarcopeltis antarctica, and Iridaea sp. from a sea ice gradient. Surprisingly, most of the chemical components were not correlated with sea ice cover, indicating sea ice coverage does not change the nutritional contributions of macroalgae to food webs.
Continue reading ‘Impacts of climate change on members of shallow water Antarctic communities’Future climate change scenarios of increased CO2 and temperature strongly affect a coral reef meiobenthic harpacticoid (Crustacea) community
Published 15 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, crustaceans, laboratory, morphology, mortality, multiple factors, otherprocess, South Atlantic, temperature, zooplankton
Small metazoans, especially harpacticoid copepods, are an important component in the benthic food webs of benthic environments. However, studies on the effects of elevated CO2 and temperature on these animals are scarce and those that do exist focus mainly on the individual species level. A laboratory experiment was conducted to evaluate the impact of different climate change scenarios on a community of harpacticoid copepods from a coral reef environment. Samples were collected from the coral reef subtidal zone of Serrambi beach (Ipojuca, Pernambuco, Brazil), using colonized artificial substrate units. The units were exposed to control treatments and to three climate change scenarios and were collected after 14 and 29 days. A highly diverse community of harpacticoids was analyzed [H′(log2) = 4.37]. Changes in the community structure were observed, and the response of the copepod community structure to the different scenarios varied according to the sampling period. The maintenance of a highly diverse community enabled a complex pattern of responses to be observed at a species level with three different response patterns to the changing seawater conditions: sensitive species represented by Tisbe sp., Stenhelia sp. and Ameira sp.; mildly sensitive represented by Cyclopoida and Dactylopusia sp.; resistant or opportunist represented by Ectinosoma sp.1, Ectinosoma sp.2 and Mesochra sp. The increase in malformed adult animals in the most severe scenario indicated that species that do not suffer mortality are not exempt from sublethal symptoms. Harpacticoid organisms are shown as reliable tools to assess climate change in coral reef environments.
Continue reading ‘Future climate change scenarios of increased CO2 and temperature strongly affect a coral reef meiobenthic harpacticoid (Crustacea) community’The impact of climate change stressors on microbial respiration and community structure: ocean acidification and artificial upwellling
Published 14 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, field, mesocosms, multiple factors, North Atlantic, nutrients, otherprocess, physiology, phytoplankton, prokaryotes, respiration
Microbial community respiration significantly influences the oceans capacity to sequester CO2 in marine ecosystems. Despite its pivotal role, there remains limited understanding of the variability and magnitude of community respiration in marine ecosystems, especially regarding its sensitivity to climate change stressors. This knowledge gap hinders a comprehensive grasp of its contribution to the global carbon cycle. Traditional in situ approaches for measuring community respiration are subject to several methodological limitations, particularly that of sensitivity in oligotrophic ecosystems, which cover more than 40% of the Earth’s ocean surface. These limitations thus contribute significantly to the uncertainty in global estimates of carbon budgets. To address these challenges, enzymatic techniques such as ETSvitro offer a fast and sensitive method to assess respiratory activity rates at spatial scales that are difficult to cover using conventional approaches. The method involves reducing the tetrazolium salt, INT, within the respiratory chain under substrate saturation levels (i.e., NADH, NADPH, and succinate). However, the reliability of the ETSvitro method has been questioned because it measures potential respiratory activity rather than actual respiration. In response to these concerns, another enzymatic technique, ETSvivo, emerged presumably as a more realistic estimate of actual respiration. Unlike ETSvitro, ETSvivo measures INT under in vivo conditions, utilizing substrates naturally available inside the cell. Nevertheless, before these methods can be considered feasible proxies for community respiration, further evaluation is needed to determine their universal applicability in marine ecosystems. In this thesis, our objective was to improve our understanding of community respiration by addressing its methodological limitations and investigating the drivers responsible for its variability. We paid particular attention to planktonic community structure and the impact of two climate change stressors: ocean acidification and changes in nutrient fertilization. Simulating a typical ETSvivo assay in eight independent experiments using surface coastal and open ocean waters from the Canary region, we observed that INT alone significantly influences the physiological status of bacteria. Bacteria are considered the primary contributors to respiration in oligotrophic environments, but their physiological status is largely affected by the inherent toxicity of INT. Consequently, we question the applicability of the ETSvivo method as a proxy for community respiration in oligotrophic regions. On the other hand, we explore the temporal variability of respiratory metabolism through two mesocosm experiments conducted in the oligotrophic waters of the subtropical Eastern North Atlantic. In the first mesocosms experiment, we investigated the impact of changing community structure and biomass on the temporal variability of community respiration measured through the Winkler method (R), ETS activity, and their ratio (R/ETS) in response to increasing CO2 concentrations and nutrient fertilization (e.g., due to local upwelling events). Our results suggest that community respiration and ETS activity do not respond to CO2 during oligotrophic conditions. However, following fertilization, community respiration increased in the two high CO2 mesocosms coinciding with an increase in microplankton, primarily diatoms. Simultaneously, the R/ETS ratio showed no correlation with community structure or biomass, indicating its variability makes it unsuitable for application with communities undergoing abrupt changes in trophic conditions. In light of these findings, the second mesocosm experiment explored the influence of different upwelling intensities and frequencies (singular pulse versus recurring upwelling) on community respiration. Our results demonstrate that community respiration is sensitive to changes in upwelling intensities but more significantly to the mode in which nutrients are supplied to oligotrophic waters. The planktonic community structure significantly influenced the observed variability in community respiration, revealing notable differences under varying upwelling intensities.The results of this thesis underscore the significance of mitigating methodological uncertainties to achieve precise measurements of respiration rates. It is crucial to adequately assess the impact of climate change-induced stressors, especially ocean acidification and changes in nutrient fertilization, along with planktonic community structure, as drivers of temporal variability. This thorough examination is essential for gaining a deeper understanding and, consequently, making more accurate predictions of community respiration in marine ecosystems.
Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities
Published 10 January 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, otherprocess, photosynthesis, phytoplankton, protists, South Atlantic, zooplankton
Highlights
- Multi-interacting driver effects were evaluated on South Atlantic estuarine plankton
- Warming×pH×nutrients×UVR reduced the photosynthetic and resource use efficiencies
- A multi-driver change condition prompted a microzooplankton-phytoplankton uncoupling
- Altered trophic interactions could reduce the energy transfer efficiency in food webs
Abstract
Plankton communities are subjected to multiple global change drivers; however, it is unknown how the interplay between them deviates from predictions based on single-driver studies, in particular when trophic interactions are explicitly considered. We investigated how simultaneous manipulation of temperature, pH, nutrient availability and solar radiation quality affects the carbon transfer from phytoplankton to herbivorous protists and their potential consequences for ecosystem functioning. Our results showed that multiple interacting global-change drivers reduced the photosynthetic (gross primary production-to-electron transport rates ratios, from 0.2 to 0.6-0.8) and resource use efficiencies (from 9 to 1 μg chlorophyll a (Chl a) μmol nitrogen-1) and prompted uncoupling between microzooplankton grazing (m) and phytoplankton growth (μ) rates (μ > m). The altered trophic interaction could be due to enhanced intra-guild predation or to microzooplankton growing at suboptimal temperatures compared to their prey. Because phytoplankton-specific loss rates to consumers grazing are the most significant uncertainty in marine biogeochemical models, we stress the need for experimental approaches quantifying it accurately to avoid bias in predicting the impacts of global change on marine ecosystems.
Continue reading ‘Multi-interacting global-change drivers reduce photosynthetic and resource use efficiencies and prompt a microzooplankton-phytoplankton uncoupling in estuarine communities’Toxicity of PAHs-enriched sediments on meiobenthic communities under ocean warming and CO2-driven acidification scenarios
Published 6 January 2025 Science ClosedTags: annelids, biological response, BRcommunity, community composition, crustaceans, laboratory, mollusks, multiple factors, nematodes, otherprocess, platyhelminthes, sediment, South Atlantic, tardigrada, temperature, toxicants, zooplankton
Highlights
- Temperature rise reduced the densities of Copepoda and certain Nematoda groups.
- CO2 acidification prevented some Nematoda groups from increasing at high temperatures.
- CO2 acidification reduced Copepoda and nauplii densities, but increased Ostracoda.
- Complex interactions increased certain meiobenthic groups exposed to sediment PAHs.
- Global change and pollution showed interactive effects in meiobenthic communities.
Abstract
This study aimed to assess the interactive effects of CO2-driven acidification, temperature rise, and PAHs toxicity on meiobenthic communities. Laboratory microcosms were established in a full factorial experimental design, manipulating temperature (25 °C and 27 °C), pH (8.1 and 7.6), and PAH contamination (acenaphthene + benzo(a)pyrene spiked sediments and negative control). Temperature rise and CO2-driven acidification led to a decrease in the densities of Copepoda. The density of nematodes Pseudochromadora and Daptonema also decreased, while Sphaerotheristus and Sabatieria densities increased, particularly in the absence of CO2-driven acidification. Ostracoda densities increased in the acidified scenario. PAH contamination resulted in decreased Daptonema densities but increased Turbellaria and certain Nematoda genera (e.g. Pseudochromadora). Overall, the results indicate that the changes of meiobenthic communities caused by CO2 acidification, warming, and PAH contamination are shaped by the vulnerability and tolerance of each taxonomic group, alongside indirect effects observed in Nematoda assemblages.
Continue reading ‘Toxicity of PAHs-enriched sediments on meiobenthic communities under ocean warming and CO2-driven acidification scenarios’Extreme abiotics drive sediment biocomplexity along pH gradients in a shallow submarine volcanic vent
Published 3 January 2025 Science ClosedTags: biogeochemistry, biological response, BRcommunity, community composition, field, Mediterranean, otherprocess, phanerogams, prokaryotes, sediment, vents
Highlights
- Shallow CO2 vents generate pH gradients that influence sediment biogeochemistry
- Sedimentary organic matter (SOM) and prokaryotic community were analysed along a pH gradient
- Environmental gradients drive distribution and abundance of benthic prokaryotic communities and origin of SOM
- Vent-derived sources contributed largely to SOM up to 350 m from the vent
- CO2-driven benthic community shifts affect spatial dynamics of SOM origin and composition with expected rebounds on biota
Abstract
Volcanic emissions in shallow vents influence the biogeochemistry of the sedimentary compartment, creating marked abiotic gradients. We assessed the spatial dynamics of the sediment compartment, as for the composition and origin of organic matter and associated prokaryotic community, in a volcanic shallow CO2 vent (Vulcano Island, Italy). Based on elemental (carbon, nitrogen content and their ratio) and isotopic composition (δ13C, δ15N and δ34S), the contribution of vent-derived organic matter (microbial mats) to sedimentary organic matter was high close to the vent, while the marine-derived end-members (seagrasses) contributed highly at increasing distance. Chemoautotrophic Campylobacterota and hyperthermophilic Achaea prevailed close to the vent, whilst phototrophic and chemoheterotrophic members dominated at increasing distance. Abiotic gradients generated by the volcanic CO2 vent drive relevant changes in the composition, origin and nutritional quality of sedimentary organic matter, and influence the structure and complexity of associated prokaryotic communities, with expected relevant impact on the entire food-web.
Continue reading ‘Extreme abiotics drive sediment biocomplexity along pH gradients in a shallow submarine volcanic vent’Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines
Published 31 December 2024 Science ClosedTags: algae, biological response, BRcommunity, chemistry, community composition, corals, field, growth, North Pacific, reproduction, vents
The existence of shallow hydrothermal vents in Mabini, Batangas, Philippines, has been recognized to contribute to CO2-rich submarine groundwater discharges. However, little is known about the existing coral community structure in the area which provides valuable ecosystem goods and ecological services. We characterized the reef community in this unique microenvironment falls within the predicted future reef condition with low pH and aragonite saturation using coral recruitment tiles, examined coral life-history strategies and size frequency distribution, and measured calcification of transplanted fragments from the genus Goniopora sp., Pectinia sp., and Porites sp. The availability of larval supply has proven that corals can still settle (45–73 recruits m−2) due to the presence of hard substrate and settlement cues such as the crustose coralline algae. The existing coral colonies were mostly dominated by stress-tolerant groups and sizes ranging from 5 to 20 cm. Deployed coral fragments showed growth via extension, and calcification was negatively affected by local conditions, such as Porites sp. fragments. Higher nutrient input may have promoted coral growth, but combined with low carbonate chemistry, it likely made the corals more susceptible to physical damage, as seen on the fragments. This study highlights the importance of naturally occurring extreme environments to determine climate-resilient corals that can adapt to changing conditions and recover from disturbances over time.
Continue reading ‘Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines’Environmental determinants of reef fish community structure in Sempu Strait, East Java, Indonesia
Published 31 December 2024 Science ClosedTags: chemistry, community composition, field, fish, Indian, otherprocess
The Rumah Apung located in Sempu Strait, Malang District, East Java, Indonesia, is home to diverse coral reef ecosystems that provide vital ecological services and support local livelihoods. However, these ecosystems face significant threats from both natural environmental changes and anthropogenic activities. Understanding how environmental factors influence reef fish communities is critical to inform effective conservation strategies. This study investigated the influence of environmental factors on the community structure of coral reef fish in the Sempu Strait waters, East Java, using Underwater Visual Census (UVC) and Principal Component Analysis (PCA). Conducted from August 2023 to May 2024 at the Sempu Strait Floating House Station, this study aimed to assess the impact of water quality, substrate type, and food availability on the diversity and abundance of coral reef fish. The main results revealed a significant correlation between the community structure of coral reef fish and environmental variables such as water clarity, salinity (r=0.65, p<0.01), pH (r=0.55, p<0.05), dissolved oxygen (r=0.70, p<0.01), and sediment type. Seasonal variations significantly affected water quality, with cold nutrient-rich water during the east monsoon increasing fish biomass by about 30%. Human activities, especially recreational diving and fishing activities, were correlated with a 20% decline in coral reef fish populations, highlighting the anthropogenic pressure on this ecosystem. PCA provides insight into the complex interdependencies within coral reef ecosystems, illustrating how multiple environmental factors combine to influence reef fish dynamics. The study concludes that effective management and conservation strategies,such as establishing marine protected areas, implementing community-based monitoring programs, and promoting sustainable tourism practices, are essential, supported by regular environmental monitoring, are essential to maintain the biodiversity and ecological integrity of coral reefs in the Sempu Strait. These strategies should address both natural environmental changes and anthropogenic impacts to mitigate their adverse effects on coral reef ecosystem conditions.
Continue reading ‘Environmental determinants of reef fish community structure in Sempu Strait, East Java, Indonesia’Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities
Published 16 December 2024 Science ClosedTags: biological response, chemistry, community composition, field, North Pacific, otherprocess, phytoplankton, zooplankton
Highlights
- Untreated effluent caused decreases in seawater pH from 8.1 to lower than 7.5.
- Decreases in pH led to nonlinearly declined abundance of all plankton groups.
- Plankton abundance recovered as pH bounced back to normal levels.
- Negative impacts of decreases in pH on the marine planktons were reversible.
Abstract
An event of releasing untreated effluent caused serious decreases in surface seawater pH from 8.1 to lower than 7.5 in seven years and increased back to prior levels after 15 years. It gives us a rare natural experiment to examine the impacts of decreases in pH on the marine plankton communities (phytoplanktons, zooplanktons, shrimp larvae, crab larvae, fish eggs, and larvae) in the natural environment. Observed decreases in pH had a nonlinear effect ubiquitous on all plankton groups, leading to a reduction of approximately 50 % in their density and abundance compared to the level at pH 8.1. Non-linear responses of planktons implied the existence of specific groups more robust to decreases in pH. As pH bounced back to normal levels, the density and abundance of the plankton communities also recovered, further indicating that the negative impacts of decreases in pH on the marine plankton communities were reversible.
Continue reading ‘Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities’
