Coral reef development is influenced by a wide variety of factors, including temperature, salinity, nutrient concentrations, and carbonate chemistry. Studies focusing on physicochemical drivers of coral reef distribution and composition in the Eastern Tropical Pacific (ETP) are scarce, and carbonate chemistry and nutrient data for this region are limited. This study measured coral reef composition and physicochemical parameters along the Pacific coast of Costa Rica, over a one-year period at three locations: Santa Elena and Matapalo in the north, and Parque Nacional Marino Ballena in the south. Our results show high seasonal and spatial variability of physicochemical conditions with significant differences mainly explained by inorganic nutrient concentrations, with driving processes also having a strong influence on the variability of carbonate chemistry parameters. Coastal upwelling is the main driver of the seasonal variability in Santa Elena. Comparison of seasonal dissimilarity within locations confirms the presence of a geographical gradient, with stronger influence of the upwelling in Santa Elena relative to Matapalo, where several parameters displayed a lower seasonality and a carbonate system that supports reef development throughout the year. Conversely, in Marino Ballena the river discharges during rainy season exerted a strong control on the seasonal variability. The integrated analysis of coral reef composition and physicochemical parameters suggests that in addition to inorganic nutrients carbonate chemistry also plays a key role in coral distribution. Analyzing the spatial distribution of the main reef builders provides insights into the species-specific tolerance to varying conditions. Pavona clavus is widely distributed in both the northern and southern locations, suggesting that this massive coral is very tolerant to the high variability of physicochemical conditions. The dominant corals in the north (Pavona gigantea and Pocillopora spp.) are highly tolerant to nutrient-enriched cold waters with low aragonite saturation, while one of the main reef-builders in southern locations (Porites cf. lobata) cope better with low salinity, low aragonite saturation and low light intensity caused by river discharges. Understanding the preferences of individual coral species at our study locations can shed light on the environmental factors driving coral reef distribution in other locations of the ETP.
Continue reading ‘Environmental conditions and carbonate chemistry variability influencing coral reef composition along the Pacific coast of Costa Rica’Posts Tagged 'community composition'
Environmental conditions and carbonate chemistry variability influencing coral reef composition along the Pacific coast of Costa Rica
Published 10 October 2025 Science ClosedTags: biogeochemistry, BRcommunity, chemistry, community composition, corals, field, North Pacific, otherprocess
Interactions of multiple abiotic stresses exacerbate mollusk diversity loss in a high-discharge coastal mangrove wetland
Published 9 October 2025 Science ClosedTags: biological response, chemistry, community composition, field, mollusks, North Pacific, otherprocess
Highlights
- A long-term study of mangrove water and mollusk diversity in Chinses Daya Bay
- Water temperature, chlorophyll-a, total nitrogen and phosphorus rise significantly
- Water pH, salinity, dissolved oxygen and mollusk diversity reduce greatly
- Long-term high emission cause multiple stressors and biodiversity loss
- Interactions between multi-water factors exacerbate mollusk diversity loss
Abstract
Coastal regions, as a hotspot region of biodiversity and the most densely populated areas in the world, are increasingly threatened by anthropogenic disturbances, including warming, acidification, eutrophication, salinity fluctuation, and oxygen loss. Although massive single-factor studies have revealed the ecological catastrophe caused by these impacts, how these impact stressors interact to endanger coastal biodiversity that is critical for ecosystem stability and human well-being is still poorly understood. To investigate whether and how water warming, acidification, eutrophication, salinity fluctuation and oxygen loss interact with each other to impact the mangrove mollusk diversity, a long-term study was conducted in the mangroves of Chinese Daya Bay from 1987–1993 to 2017–2021. We found that water temperature, chlorophyll-a, total nitrogen (TN) and total phosphorus (TP) increased significantly, while the water pH, salinity, dissolved oxygen (DO) and mollusk species richness decreased obviously, reflecting water warming, eutrophication, acidification, salinity fluctuation, oxygen loss and biodiversity loss occurred in the Daya Bay. The mangrove mollusk diversity had a significant response to the water warming, eutrophication, acidification, salinity fluctuation, oxygen loss (p < 0.001). The average incidences of mollusk diversity loss due to the changes in water pH, temperature, TP, TN, chlorophyll-a, salinity and DO were 47.11 %, 35.56 %, 35.53 %, 34.48 %, 34.22 %, 34.15 % and 33.05 %, respectively. Moreover, the average effect of interactions between any two water factors on the mollusk diversity was 0.998, which was 22.5 % larger than their single effect on biodiversity of 0.814. The findings suggest that interactions between global change stressors can exacerbate biodiversity loss in coastal wetlands. Quantifying those effects in terms of multi-factor interactions will contribute to the coastal management and restoration based upon combined evidence rather than a one-sided single perspective.
Continue reading ‘Interactions of multiple abiotic stresses exacerbate mollusk diversity loss in a high-discharge coastal mangrove wetland’Relative enrichment of ammonium and its impacts on open-ocean phytoplankton community composition under a high-emissions scenario
Published 7 October 2025 Science ClosedTags: biogeochemistry, biological response, community composition, field, globalmodeling, modeling, otherprocess, phytoplankton
Ammonium (NH4+) is an important component of the ocean’s dissolved inorganic nitrogen (DIN) pool, especially in stratified marine environments where intense recycling of organic matter elevates its supply over other forms. Using a global-ocean biogeochemical model with good fidelity to the sparse NH4+ data that are available, we project increases in the NH4+: DIN ratio in over 98 % of the ocean by the end of the 21st century under a high-emission scenario. This relative enrichment of NH4+ is driven largely by circulation changes and secondarily by warming-induced increases in microbial metabolism, as well as reduced nitrification rates due to pH decreases. Supplementing our model projections with geochemical measurements and phytoplankton abundance data from Tara Oceans, we demonstrate that shifts in the form of DIN to NH4+ may impact phytoplankton communities by disadvantaging nitrate-dependent taxa like diatoms while promoting taxa better adapted to NH4+. This could have cascading effects on marine food webs, carbon cycling and fishery productivity. Overall, the form of bioavailable nitrogen emerges as a potentially underappreciated driver of ecosystem structure and function in the changing ocean.
Continue reading ‘Relative enrichment of ammonium and its impacts on open-ocean phytoplankton community composition under a high-emissions scenario’Effects of ocean acidification on intestinal homeostasis and organismal performance in a marine bivalve: from microbial shifts to physiological suppression
Published 18 September 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess, performance, physiology, prokaryotes
Highlights
- OA stimulates the colonization of the pathogenic bacterium Mycoplasma.
- Microbiota dysbiosis and oxidative damage trigger intestinal inflammation.
- OA causes significant epithelial damage to the intestines of C. nobilis.
- Physiological suppression of C. nobilis is decreased in a pH-dependent manner.
Abstract
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’The effects of ocean acidification on the epiphytic bacterial community of Sargassum thunbergii via high-throughput sequencing
Published 11 September 2025 Science ClosedTags: abundance, adaptation, algae, biological response, BRcommunity, community composition, laboratory, molecular biology, nitrogen fixation, North Pacific, otherprocess, physiology, prokaryotes
Marine macroalgae and their epiphytic bacteria have established a symbiotic relationship. Although the effects of ocean acidification (OA) on macroalgae have been extensively studied, its impact on these epiphytic bacteria remains unclear. This study investigated the OA-induced shifts in the epiphytic bacterial community of Sargassum thunbergii from Qingdao’s intertidal zone using 16S rDNA sequencing. The results indicated that elevated CO2 altered bacterial community structure and function, reducing diversity while maintaining dominant taxa but significantly changing their relative abundances. The abundances of Proteobacteria, Firmicutes, and Verrucomicrobiota declined, whereas Campylobacterota, Desulfobacterota, and Spirochaetota increased. The specific phyla like Cloacimonadota, Calditrichota and Entotheonellaeota also emerged. These shifts were linked to the environmental adaptability and stress resistance of epiphytic bacteria as well as the metabolic activities of the host algae, particularly in protein and fatty acid degradation.
Functional predictions revealed that OA primarily affected nitrogen and sulfur metabolism in the epiphytic bacterial community, with effects intensifying over time. Specifically, nitrogen fixation increased, while dark oxidation of sulfur compounds, dark sulfite oxidation, and dark sulfur oxidation decreased. In conclusion, ocean acidification directly induced changes in the abundance of epiphytic bacterial taxa with varying stress resistance and adaptability. Simultaneously, it promoted shifts in bacterial taxa closely associated with the host algal metabolic activities, ultimately reshaping the epiphytic bacterial community on S. thunbergii. These findings provided new insights into the macroalgae-epiphytic bacteria interactions under ocean acidification and provided important guidance for macroalgal cultivation.
Continue reading ‘The effects of ocean acidification on the epiphytic bacterial community of Sargassum thunbergii via high-throughput sequencing’Decreasing foraminiferal flux in response to ongoing climate change in the Santa Barbara Basin, California
Published 2 September 2025 Science ClosedTags: abundance, biological response, community composition, field, North Pacific, otherprocess, protists, review
The rapid response of foraminiferal assemblages to changing climate makes their shells an invaluable geological record of the past. However, the time frame over which foraminifera respond to climatic signals and the specific drivers influencing assemblage composition and abundance remain obscure. We focus on the impact of ongoing, anthropogenic climate change on planktic foraminifera in the California Current ecosystem, which would appear as a nearly instantaneous event in the sediment record. The Santa Barbara Basin sediment trap, located off the coast of California, USA since 1993, provides a record of more than 30 years of particulate and foraminiferal flux in the basin. The sediment trap captures the superposition of the annual cycle of seasonal upwelling, Pacific multiannual El Niño–Southern Oscillation-driven temperature changes, and anthropogenically forced climate change. We present data on planktic foraminiferal flux collected between 2014–2021, at two-week intervals (164 samples, 60 006 individuals) and compare results to previously published data from 1993–1998. Consistent with previous studies, the most abundant species from 2014–2021 were Globigerina bulloides, Neogloboquadrina incompta, and Turborotalita quinqueloba, with peak fluxes occurring in the spring and summer. Lower fluxes and an increase in the abundance of N. incompta and subtropical species characterize the winter season. We find a 37.9 % decrease in total foraminiferal flux relative to the 1990s, primarily driven by a decrease in G. bulloides abundance. This decrease is accompanied by a 21.0 % overall reduction in calcium carbonate flux. We also find a decrease in the relative abundance of subtropical species (Globigerinoides ruber, Orbulina universa, and Neogloboquadrina dutertrei) and their fluxes compared to the 1990s, opposite expectations if assemblages and fluxes were to follow anthropogenic warming signals. We hypothesize that the observed decrease in subtropical species abundance and flux is likely related to an increase in acidification and in the timing and magnitude of upwelling along the California coast. The extremely rapid responses of foraminifera to ongoing changes in carbonate chemistry and temperature suggest that climate change is already having a meaningful impact on coastal carbon cycling. The observed decrease in particulate inorganic carbon (PIC) flux relative to particulate organic carbon (POC) flux may facilitate increased oceanic uptake of atmospheric CO2.
Continue reading ‘Decreasing foraminiferal flux in response to ongoing climate change in the Santa Barbara Basin, California’Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal
Published 21 August 2025 Science ClosedTags: abundance, biological response, community composition, field, Indian, mollusks, otherprocess, protists, zooplankton
Anthropogenic greenhouse gas emissions have a detrimental impact on the carbon sequestration by the oceans. Pteropods, a crucial component of the ocean’s planktic community, secrete aragonite shells that are sensitive to increasing atmospheric carbon dioxide levels, making them the first indicators of ocean acidification. Therefore, pteropods are often used to observe the changes in aragonite compensation depth (ACD). Intriguingly, in the major parts of the northern Indian Ocean, the chemically defined ACD is < 800 m, but pteropods have been reported in surface sediments collected from much deeper depths in the same region, which raises questions about the use of pteropods to trace ACD in this area. To address this ambiguity, we conducted a systematic and detailed evaluation of pteropods to trace the changes in ACD in the western Bay of Bengal, which is the first-ever such study. The pteropods population dominated by Heliconoides inflatus was low on the inner shelf, and isolated pockets of high pteropod abundance were restricted to the upper slope. Based on the pteropod abundance in the surface sediments and the ratio of pteropods to planktic foraminifera, we report the baseline ACD in the western Bay of Bengal at ~ 500 m. The aragonite compensation depth based on the pteropod abundance in the surface sediments correlates well with the chemically defined ACD in this region. These findings will help to assess the impact of ocean acidification on aragonite compensation depth in the western Bay of Bengal.
Continue reading ‘Pteropods reliably record the aragonite compensation depth in the western Bay of Bengal’Ocean acidification and nitrate enrichment can mitigate negative effects of soft coral (Xenia) competition on hard coral (Stylophora pistillata) endosymbionts
Published 21 August 2025 Science ClosedTags: biological response, BRcommunity, community composition, corals, growth, laboratory, multiple factors, nutrients, otherprocess, physiology, phytoplankton
The combination of ocean acidification (OA) and eutrophication can undermine the physiological performance of reef-building corals during competition for benthic space, leading to shifts towards non-accreting organisms like soft corals. We conducted a 28-day laboratory orthogonal experiment to test if acidification (950 µatm pCO2) and moderate to high nitrate enrichment (4 and 8 µmolL−1) negatively affect the hard coral Stylophora pistillata while physically competing with the soft coral Xenia spp. We measured photosynthetic efficiency (PE) in hard corals and growth rate, Symbiodiniaceae density, and chlorophyll-a concentration in both hard and soft corals as proxies for their condition and responses to competition. Competition with the soft coral reduced PE, Symbiodiniaceae and chlorophyll-a contents of S. pistillata, while acidification alone and coupled with nitrate enrichment mitigated endosymbiont responses. The growth and chlorophyll-a concentrations of Xenia spp. were decreased by competition, but the soft coral was consistently benefited under nitrate enrichment. These results highlight that competition alone has a stronger negative impact on hard corals than on soft corals. Our study provides experimental evidence on how OA and eutrophication interact and shape coral dynamics, an overlooked but urgent topic in predicting reef futures under environmental change.
Continue reading ‘Ocean acidification and nitrate enrichment can mitigate negative effects of soft coral (Xenia) competition on hard coral (Stylophora pistillata) endosymbionts’Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans
Published 12 August 2025 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, bryozoa, community composition, communitymodeling, field, Mediterranean, modeling, molecular biology, morphology, mortality, otherprocess, prokaryotes, vents
Marine habitat-forming species provide crucial ecosystem functions and services worldwide. Still, the individual and combined long-term effects of ocean acidification and warming on bryozoan populations, structures, and microbiomes remain unexplored. Here, we investigate the skeletal properties, microbiome shifts, and population trends of two bryozoan species living inside and outside a volcanic CO2 vent, a natural analog to future ocean acidification conditions. We show that bryozoans can acclimatize to acidification by adjusting skeletal properties and maintaining stable microbiomes. However, we document a decrease in microbial genera playing essential functions under acidified conditions. Moreover, we show that ocean acidification exacerbates bryozoan cover loss and mortality caused by ocean warming. The observed shifts in the microbiome and cover suggest that, despite their morphological plasticity, bryozoan species will be heavily impacted by future ocean conditions, posing a threat to many benthic ecosystems in which they play a pivotal role.
Continue reading ‘Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans’Combined effects of ocean acidification and warming on phytoplankton productivity and community structure in the coastal water of Southern East
Published 17 July 2025 Science ClosedTags: biological response, community composition, laboratory, mesocosms, molecular biology, multiple factors, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, temperature
Highlights
- Ocean warming partly offsets acidification-driven impacts on primary productivity in a southern coastal water of China.
- Acidification alters phytoplankton communities with increased proportions of dinoflagellates and reduced that of diatoms.
- Combination of warming and acidification reduced overall microbial diversity in the coastal water.
Abstract
Progressive global ocean changes, including ocean acidification and warming, are expected to impact ecosystems differentially due to regional environmental differences that govern biogeochemical and ecological processes. In this study, we investigated the impacts of ocean acidification and warming on the phytoplankton community and primary productivity in the southern coastal water of the East China Sea by running land-based mesocosms controlled under current atmospheric pCO2 (∼430 μatm) and projected levels for the year 2100 (∼1000 μatm, HC, High CO2) at 27°C (ambient) and 30°C (warming, HT, High Temperature). Our results indicate that warming, acidification, and their combined effects (HCHT) initially enhanced community biomass as determined by chl a concentration; however, this effect diminished over time, ultimately resulting in lower biomass density compared to the control in later stages. Primary productivity per volume of seawater in the HT and HCHT treatments was initially suppressed but increased in the later stages compared to the control group, whereas the HC treatment appeared to suppress it consistently. While higher effective photochemical efficiency and non-photochemical quenching coincided with higher photosynthetic carbon fixation per chlorophyll an under the HT and HCHT treatments, their decline under the HC after the acclimation was concurrent with decreased photosynthetic carbon fixation. Analysis of 18S rDNA revealed that diatoms and dinoflagellates dominated under the treatments of HC, HT, and HCHT, but compared to the control, the proportion of diatoms decreased by 23%, 14%, and6 %, while that of dinoflagellates increased by 19%, 9%, and 11%, respectively, under the corresponding treatments. Plankton richness increased under warming, while diversity declined, particularly with combined warming and acidification, highlighting community sensitivity to the stressors. With reference to heterotrophic microbes, the relative abundance of Basidiomycota increased by 16%–18% under HT or HCHT, along with insignificant impacts on prokaryotic communities based on 16S rDNA analysis. In conclusion, the combination of ocean acidification and warming treatment during the experimental period ultimately reduced the phytoplankton biomass density and altered the microbial community structure.
Continue reading ‘Combined effects of ocean acidification and warming on phytoplankton productivity and community structure in the coastal water of Southern East’Shifts in coral reef holobiont communities in the high-CO2 marine environment of Iōtorishima Island
Published 15 July 2025 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, corals, field, molecular biology, North Pacific, otherprocess, phytoplankton, prokaryotes, vents
Ocean acidification (OA), driven by rising atmospheric CO2, presents a serious threat to marine biodiversity, especially within coral reef ecosystems. Natural analogue sites, such as the high-pCO2 seep at Iōtorishima Island in Japan, offer insights into future conditions. This study investigated the holobiont communities of Symbiodiniaceae and bacteria in the zoantharian Palythoa tuberculosa at Iōtorishima and compared them to specimens from control sites in Okinawa and Hawaiʻi. Using amplicon sequencing of the dinoflagellate internal transcribed spacer 2 (ITS2) region of ribosomal DNA and microbial 16S rRNA gene, we detected significant shifts in both Symbiodiniaceae and bacterial communities under high-pCO2 conditions at Iōtorishima. Specifically, P. tuberculosa at the seep site had reduced Symbiodiniaceae diversity, predominatly featuring Cladocopium C1 and C3 types. Additionally, its bacterial communities showed lower richness with distinct taxonomic profiles, including increased levels of Mollicutes and Vibrio spp. These results highlight the potentially adverse effects of OA on hexacoral holobionts and emphasize the need for detailed, high-resolution studies across various holobiont species and geographic locations. The shifts observed specifically in Symbiodiniaceae and bacterial communities at the Iōtorishima seep suggest that holobionts may exhibit plasticity in response to environmental stress, which has implications for resilience and adaptation of zoantharians and other reef organisms amid climate change. This research provides crucial baseline data for predicting future coral reef compositions in an OA-affected world.
Continue reading ‘Shifts in coral reef holobiont communities in the high-CO2 marine environment of Iōtorishima Island’Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification
Published 14 July 2025 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, mollusks, North Atlantic, otherprocess, vents
Highlights
- Ocean acidification can modify the structure of marine communities.
- The macroalga Halopteris sp. supports a rich community of associated molluscs.
- Halopteris sp. from an acidified site support fewer and less diverse assemblages.
- Most abundant species were present both at the acidified and reference sites.
- Biodiversity of molluscs will be simplified under acidified conditions.
Abstract
Ocean acidification can have profound effects on marine organisms, particularly those that rely on calcium carbonate for shell and skeleton formation, resulting in structural changes to marine ecosystems. Here, we contrast the structure of marine mollusc communities (epifauna) associated with an abundant shallow-water macroalga, Halopteris scoparia, in an area with seawater carbonated by natural CO2 seeps and three reference sites, off the Azores archipelago. Epifaunal mollusc abundance and diversity were significantly lower at the CO2 seep compared to reference sites whilst species accumulation curves and Jaccard multivariate analyses showed that the mollusc assemblage was consistently less diverse at the CO2 seep. Most of the abundant epifaunal species that were present at the CO2 seep were also found at reference sites, but less common or rare species were generally absent from the former. We conclude that while some molluscs are likely to cope with ocean acidification, the overall biodiversity of epifaunal molluscs will be simplified under these conditions in a future ocean.
Continue reading ‘Mollusc epifaunal assemblages are simplified due to habitat shifts under ocean acidification’Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, community composition, growth, laboratory, morphology, multiple factors, nutrients, otherprocess, physiology, phytoplankton, temperature
Abstract
The cumulative effects of multi‐faceted changes on the phytoplankton community of the Southern Ocean (SO) are not yet known, which is a major limitation to predicting the future direction of the biological carbon pump. Thus, our study aimed to estimate the effects of intensified Patagonian dust inputs, warming and acidification on the growth, composition and production of phytoplankton assemblages in the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region of the Indian sector of the SO during the austral summer 2022. Natural phytoplankton communities were incubated for 5‐day under 4 scenarios (present and future conditions, and 2 intermediate scenarios). In the PFZ, +3°C and acidification stimulated the growth of phytoplankton, mainly cyanobacteria, while intensified dust inputs alone did not have notable impact. Conversely, in HNLC waters, the addition of Fe‐dust alone increased the total chlorophyll a of diatoms (mainly F. kerguelensis), whereas the negative effect of acidification and +3°C counteracted the positive impact of dust input on the diatoms. In these waters, future conditions benefited smaller species (haptophytes and cyanobacteria). The net particulate organic carbon production (POC) was also unaltered by future conditions, suggesting that primary production may not change in the future SO. However the increase in the length and number of long‐chain diatoms under future HNLC conditions may indicate that POC export could intensify in the future.
Plain Language Summary
Phytoplankton in the Southern Ocean (SO) play a critical role in absorbing atmospheric carbon dioxide and supporting marine ecosystems, however their response to future environmental changes remains unclear. This study examined how increased dust inputs, warming, and acidification affect the phytoplankton community in two contrasted biogeochemical domains of the SO, the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region. In the PFZ, warming and acidification favored the smaller phytoplankton species, while in the HNLC region, iron‐rich dust stimulated diatom species, though this effect was attenuated by warming and acidification. While overall the production of organic carbon by phytoplankton remained unchanged, diatoms may enhance carbon export to deeper waters under future conditions due to increased number and length of chain‐forming species. These findings highlighted the complexity of phytoplankton responses, which vary across regions and are influenced by interactive environmental factors. Understanding the impact of these environmental factors on phytoplankton is critical to predicting how future changes will shape the role of the SO in the global carbon cycle.
Continue reading ‘Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean’CO2 enrichment enhances biomass density and C:N:P ratios in phytoplankton assemblage in the coastal water of the Taiwan Strait
Published 3 July 2025 Science ClosedTags: abundance, biogeochemistry, biological response, community composition, laboratory, North Pacific, otherprocess, phytoplankton
Seawater CO2 concentrations are steadily increasing in the Taiwan Strait of the Southeast China, while the effects of rising CO2 on carbon fixation and elemental composition of phytoplankton assemblages in this area are still poorly understood. Here, we enriched the seawater CO2 concentrations to 808 μatm and above to simulate the CO2–induced ocean acidification, and investigated the effects of CO2 enrichment on concentrations of chlorophyll (Chl) a, particulate organic carbon (POC), nitrogen (PON) and phosphorus (POP), the C:N:P ratio, and phytoplankton community composition in the coastal surface seawaters of the northwest Taiwan Strait in autumn 2023 and spring 2024 through an outdoor incubation experiment. After three days of incubation, CO2 enrichment increased the concentrations of Chl a by 1–14%, POC by 21–32% and PON by 21–56%, whereas reduced the POP concentrations by 1–37%, leading to elevated ratios of POC:POP and PON:POP. Furthermore, elevated CO2 level enhanced cell abundances of the dominant diatom genera at three stations. These results suggest that phytoplankton has the potential to buffer against rising atmospheric CO2 level and can help us to understand the elemental biogeochemistry in the Taiwan Strait under future ocean acidification scenarios.
Continue reading ‘CO2 enrichment enhances biomass density and C:N:P ratios in phytoplankton assemblage in the coastal water of the Taiwan Strait’Decreased dimethylsulfide and increased polybrominated methanes: potential climate effects of microplastic pollution in acidified ocean
Published 3 July 2025 Science ClosedTags: biogeochemistry, biological response, community composition, laboratory, multiple factors, otherprocess, phytoplankton, plastics
Microplastic (MP) pollution and ocean acidification (OA) are pressing marine environmental concerns, but their combined impacts on short-lived biogenic climate-active gases and the resulting climate effects remain unclear. To address this gap, a ship-based microcosm experiment was conducted, where OA and MP pollution were simulated under in situ conditions to explore their effects on the production of dimethylsulfide (DMS), bromoform (CHBr3), and dibromomethane (CH2Br2). The results indicated that both MP and OA inhibited phytoplankton growth and DMS concentration, with OA inducing further reductions in the production rate and yield of DMS. MP addition led to extra dissolved organic matter, and the acidified condition enhanced bromoperoxidase activity, both of which promoted the production of CHBr3 and CH2Br2. When OA and MP addition were combined, DMS concentrations decreased by 61%, whereas CHBr3 and CH2Br2 concentrations increased by 132% and 45%, respectively. Based on the results, MP pollution under OA conditions might directly reduce DMS accumulation or decrease the formation of DMS-derived sulfate aerosols by increasing CHBr3 and CH2Br2 levels, which finally weaken DMS’s climate-cooling capabilities. This study underscores the potential for MP pollution in future acidified oceans to exacerbate global warming by disrupting the cycle of marine biogenic climate-active gases.
Continue reading ‘Decreased dimethylsulfide and increased polybrominated methanes: potential climate effects of microplastic pollution in acidified ocean’Effects of different environmental stressors on marine biogenic sulfur compounds in the Northwest Pacific and Eastern Indian Oceans
Published 2 July 2025 Science ClosedTags: abundance, biogeochemistry, biological response, community composition, growth, Indian, laboratory, multiple factors, North Pacific, otherprocess, physiology, phytoplankton
Abstract
Key roles of marine dimethyl sulfoniopropionate (DMSP), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2) in the sulfur cycle and/or atmospheric chemistry, alongside the rapid environmental changes in marine ecosystems, underscore the need to understand their responses to dynamic ecosystem shifts. We conducted two ship-based incubation experiments in the Northwest Pacific and Eastern Indian Oceans to explore how dust deposition, ocean acidification, and microplastic exposure impact these compounds. Our results demonstrate that these stressors not only alter phytoplankton community but also modify per-cell DMSP production capacity and DMSP degradation pathways, subsequently influencing DMSP, DMS, and MeSH concentrations. CS2‘s response closely mirrors phytoplankton abundance and species. Initial physical-chemical conditions, such as carbonate system and nutrient availability, may mediate the sensitivity of phytoplankton and sulfur compounds to environmental shifts. This study enhances our understanding of biogenic sulfur responses in dynamic marine ecosystems and provides essential basis for future climate modeling.
Key Points
- External stressors alter algal communities and production and degradation of dimethyl sulfoniopropionate, thus affecting biogenic sulfides
- Response of carbon disulfide to different environmental stressors is closely linked to algal abundance
- Initial physical-chemical conditions of seawater mediate algae and biogenic sulfides’ sensitivity to environmental stressors
Plain Language Summary
Biogenic sulfur-containing compounds in the ocean, such as dimethyl sulfoniopropionate (DMSP), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2), play critical roles in the global sulfur cycle and have the potential to influence the Earth’s climate. For instance, DMS released from the ocean into the atmosphere contributes to cloud formation, which in turn affects weather patterns. Over recent decades, rapid environmental changes in marine ecosystems may have significantly impacted marine biogeochemical processes. To investigate how these compounds respond to such changes, we conducted two ship-based incubation experiments in the Northwest Pacific and Eastern Indian Oceans. We assessed the effects of dust deposition, ocean acidification (due to increased carbon dioxide), and microplastic pollution on the production of DMSP, DMS, MeSH, and CS2 by marine organisms. Our results demonstrate that these stressors alter phytoplankton growth and community composition and impact the pathways through which DMSP is degraded. Consequently, the concentrations of sulfur compounds in seawater are affected. Notably, changes in CS2 levels were more closely related to shifts in phytoplankton abundance. These findings enhance our understanding of how marine sulfur compounds may respond to future oceanic changes and offer valuable data for improving climate models.
Continue reading ‘Effects of different environmental stressors on marine biogenic sulfur compounds in the Northwest Pacific and Eastern Indian Oceans’Antarctic macroalgal-associated amphipod assemblages exhibit long-term resistance to ocean acidification
Published 19 June 2025 Science ClosedTags: abundance, algae, Antarctic, biological response, BRcommunity, community composition, crustaceans, laboratory, mortality, otherprocess
The pH of the world’s oceans has decreased since the Industrial Revolution due to the oceanic uptake of increased atmospheric CO2 in a process called ocean acidification. Low pH has been linked to negative impacts on the calcification, growth, and survival of calcifying invertebrates. Along the Western Antarctic Peninsula, dominant brown macroalgae often shelter large numbers of diverse invertebrate mesograzers, many of which are calcified. Mesograzer assemblages in this region are often composed of large numbers of amphipods which have key roles in Antarctic macroalgal communities. Understanding the impacts of acidification on amphipods is vital for understanding how these communities will be impacted by climate change. To assess how long-term acidification may influence the survival of different members in these assemblages, mesograzers, particularly amphipods, associated with the brown alga Desmarestia menziesii were collected from the immediate vicinity of Palmer Station, Antarctica (S64°46′, W64°03′) in January 2020 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.1), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 52 days then enumerated. Total assemblage number and the relative proportion of each species in the assemblage were found to be similar across the pH treatments. These results suggest that amphipod assemblages associated with D. menziesii may be resistant to long-term exposure to decreased pH.
Alleviation of competitive constraints through long-term adaptation to high CO2 in mixed cultures of two diatom species
Published 27 May 2025 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, growth, North Pacific, otherprocess, photosynthesis, physiology, phytoplankton, respiration
Highlights
- The resources competition of two diatoms reduced most performance parameters.
- High CO₂ adaptation partially alleviates the detrimental effects of competition.
- Resource competition changes phytoplankton’s adaptation strategy to high CO2.
Abstract
Diatoms play a pivotal role in marine ecosystems, contributing significantly to global primary production and carbon cycling. Understanding their responses to high CO₂ is critical for predicting oceanic changes under future climate scenarios. This study investigates the long-term adaptation of two diatom species, Thalassiosira weissflogii and Phaeodactylum tricornutum, to high CO₂ (1000 µatm) over 3.5–4 years and the consequences of their interactions in mixed cultures. Mono- and mixed-species cultures were maintained under both ambient (400 µatm) and high CO₂ conditions to assess various physiological performances. Our results revealed that most measured parameters (growth rate, photosynthesis and respiration rate, chlorophyll fluorescence parameters, and pigment concentration) were significantly reduced in mixed cultures compared to mono-cultures under both CO₂ conditions, underscoring the detrimental effects of interspecific competition. However, long-term adaptation to high CO₂ partially alleviated these reductions, particularly in photosynthesis, respiration, and chlorophyll-a content. These findings highlight the complex interplay between physiological adaptation and interspecific competition in shaping diatom responses to high CO₂. This study advances our understanding of the ecological and evolutionary implications of ocean acidification and underscores the importance of long-term experimental approaches for assessing the impacts of climate change on marine phytoplankton.
Continue reading ‘Alleviation of competitive constraints through long-term adaptation to high CO2 in mixed cultures of two diatom species’Exploring the land-ocean biogeochemical and microbial connectivity in the Ría de Vigo (NW Iberian Peninsula) through submarine groundwater discharge
Published 20 May 2025 Science ClosedTags: biogeochemistry, BRcommunity, chemistry, community composition, field, molecular biology, North Atlantic, otherprocess, prokaryotes
Highlights
- SGD affects the carbonate system, methane and nitrous oxide content of the embayment
- Solute composition of SGD largely impacted by subterranean estuary reactivity
- Contrasting poor microbial connectivity across the different aquatic environments
- Subterranean estuaries may act as microbial boundaries in the aquatic continuum
Abstract
Increasing evidence demonstrates the widespread occurrence of submarine groundwater discharge (SGD) in coastal zones, where it may influence biogeochemistry and microbial ecology. Here, we analyze the biogeochemical composition and microbial communities across diverse aquatic environments in a highly productive coastal system (Ría de Vigo, NW Iberian Peninsula), influenced by significant fresh SGD, to assess the extent of microbial and biogeochemical connectivity—i.e., mass transfer—among them. Samples were collected from surface and deep porewaters from two subterranean estuaries (STEs), surface seawater, riverine water, and continental groundwater. These samples were analyzed for a comprehensive set of microbial and biogeochemical variables, including radioisotopes used as SGD tracers. A significant correlation between SGD tracers and carbonate system parameters, N2O, and CH4 concentrations in surface seawater indicates SGD influences biogeochemistry of the embayment. However, some of these solutes do not originate from continental groundwater but are produced in the local STEs, which act as biogeochemical reactors modifying fresh SGD. The findings also reveal highly diverse microbial communities, with higher diversity in STEs due to the variety of niches present. Indicator taxa included the phyla Euryarchaeota, Chloroflexi, Omnitrophicaeota, and the family Nitrosopumilaceae in STEs; the phylum Cyanobacteria and the family Burkholderiaceae in freshwater endmembers; and the Flavobacteriaceae and Cryomorphaceae families in seawater. Most operational taxonomic units (∼87%) were unique to a single environment (river, continental groundwater, coastal water, or STE), showing STEs limit subterranean microbial transfer between groundwater and marine ecosystems. Our results highlight STEs as reservoirs of diversity and zones of intense biogeochemical reactivity.
Continue reading ‘Exploring the land-ocean biogeochemical and microbial connectivity in the Ría de Vigo (NW Iberian Peninsula) through submarine groundwater discharge’Pteropods as early-warning indicators of ocean acidification
Published 6 May 2025 Science ClosedTags: Antarctic, biological response, BRcommunity, chemistry, community composition, dissolution, field, mollusks, morphology, otherprocess, zooplankton
Aragonite undersaturation (Ωar < 1) events are projected to rapidly increase in frequency and duration in the Antarctic Weddell Sea by 2050. Thecosome pteropods (pelagic snails) are bioindicators of ocean acidification (OA) because their aragonite shell dissolves easily at low Ωar saturation states. Here, we describe the shell dissolution state of the pteropod Limacina helicina antarctica in relation to the water column Ωar in the southern Weddell Sea during austral summer 2018 as benchmark for future monitoring of ongoing OA. Ωar depth profiles at the sampling sites were consistently close to or in the range of threshold levels (Ωar ~ 1.1–1.3) for pteropod shell dissolution. Pteropods contributed up to 69% of total mesozooplankton biomass, and their distribution correlated positively with Ωar and chlorophyll a concentration. When analyzed with scanning electron microscopy, 78% of the investigated shells exhibited dissolution, and 50–69% showed the more severe Type II dissolution exceeding current projections of pteropod shell dissolution for the Southern Ocean. But importantly, in our study, only two specimens had the most severe Type III dissolution. Dissolution often co-occurred with and occurred in scratch marks of unclear origin supporting notions that an intact periostracum protects the shell from dissolution. Where dissolution occurred in the absence of scratches or absence of evidence of periostracum breaches, microscale/nanoscale breaches may have been an important pathway for dissolution commencement supporting recent findings of a reduction of the organic shell content caused by low Ωar/low pH. The dissolution benchmark we provide here allows future application of pteropods as early-warning indicators of presumably progressing OA in the Weddell Sea.
Continue reading ‘Pteropods as early-warning indicators of ocean acidification’
