Posts Tagged 'community composition'

« Previous Entries
Next Entries »

High-resolution temporal assessment of physicochemical variability and water quality in tropical semi-enclosed bays and coral reefs

Published 24 February 2025 Science Closed
Tags: , , , , , , ,

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 Closed
Tags: , , , , , , , , , ,

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 Closed
Tags: , , , , , , , ,

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 Closed
Tags: , , , , , , ,

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 Closed
Tags: , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , , , ,

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.

Continue reading ‘The impact of climate change stressors on microbial respiration and community structure: ocean acidification and artificial upwellling’

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 Closed
Tags: , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , ,

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 Closed
Tags: , , , , , , , , , ,

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 Closed
Tags: , , , , ,

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 Closed
Tags: , , , , , , ,

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’

Resource homogenisation drives niche convergence between generalists and specialists in a future ocean

Published 13 December 2024 Science Closed
Tags: , , , , , , , ,

Highlights

  • Do marine herbivores adjust their trophic niches under climate change?.
  • Specialist and generalist herbivore niches and their food were tested using stable isotopes.
  • Food resources were dominated by turf algae and SOM under climate change.
  • Niche breath of generalists narrowed under climate stress but widened in specialists.
  • Generalists and specialists appear to converge their trophic niches under climate change.

Abstract

When humans drive rapid environmental change, is it favourable to be a generalist or specialist? To address this question, we compare how specialist and generalist marine herbivores adjust their isotopic niches (used as proxy for trophic niche) in response to predicted resource alterations under the simulated effects of ocean warming and acidification (based on a 6-month mesocosm experiment). Here, we show that when exposed to multiple climate stressors, food resources homogenized towards dominance of turf algae and suspended organic matter, with generalists and specialists adjusting their trophic niches in opposing ways. Whilst the niche breath of most generalists narrowed under climate stressors, those of specialists generally broadened, causing increasing overlap between their niches. The magnitude of this change was such that some generalists turned into specialists, and vice versa. Under ocean acidification, there was a greater probability of generalists increasing and specialists maintaining their biomass, respectively, but under warming the biomass of both specialists and generalists had a greater probability of collapse. For specialists, this collapse occurred even though they had adequate thermal tolerance and the capacity to expand their trophic niche. Climate change constrains or liberates resources, but where they are homogenized, generalists and specialists are likely to converge their trophic niches so they can exploit transforming environments for their survival or adaptive advantage.

Continue reading ‘Resource homogenisation drives niche convergence between generalists and specialists in a future ocean’

Particulate inorganic carbon quotas by coccolithophores in low oxygen/low pH waters off the Southeast Pacific margin

Published 12 December 2024 Science Closed
Tags: , , , , , , ,

A predicted consequence of ocean acidification is its negative effect on the pools of Particulate Inorganic Carbon (PIC) that are essential for ‘ballasting’ the sinking of organic carbon, potentially leading to decreased subsurface oxygen. To explore such possible feedbacks, we investigated the relationships between PIC, coccolithophores, carbonate chemistry, and dissolved oxygen in the Southeast Pacific open ocean oxygen minimum zone, which naturally exhibits extremely low dissolved oxygen, low pH, and high pCO2 levels. Measurements of PIC and coccolithophore counts during late-spring 2015 and mid-summer 2018 revealed that coccolithophores, particularly Gephyrocapsa (Emiliania) huxleyi, significantly contributed to PIC through the shedding of coccoliths in the upper waters. On average, about a half of the PIC was attributed to countable coccoliths, with significantly diminished quotas observed below the euphotic depth. Temperature, oxygen, and pH were identified as key variables influencing PIC variation. PIC quotas were similar to those reported in other upwelling zones. However, PIC:POC ratios were substantially lower than what has been reported both in other open ocean and coastal margin areas, an effect that was more pronounced within the vertically defined oxygen minimum zone core. This study contributes to understanding the role of coccolithophores in PIC pools and suggests that the presence of low O2/low pH subsurface waters does not inhibit coccolithophore PIC quotas but may decrease the role of PIC in ballasting the export of organic carbon.

Continue reading ‘Particulate inorganic carbon quotas by coccolithophores in low oxygen/low pH waters off the Southeast Pacific margin’

Ocean acidification and plankton

Published 10 December 2024 Science Closed
Tags: , , , , , ,

Ocean acidification represents a significant and growing threat to some species of marine plankton, with wide-ranging implications for marine ecosystems and the services they provide. The alterations in plankton physiology, behavior, and community structure under acidified conditions exemplify the profound impact of anthropogenic CO₂ emissions on the ocean’s smallest, yet most essential inhabitants.

Continue reading ‘Ocean acidification and plankton’

Sea-air CO2 exchanges, pCO2 drivers and phytoplankton communities in the southwestern South Atlantic Ocean during spring

Published 3 December 2024 Science Closed
Tags: , , , , , , ,

Highlights

  • The southwestern Brazilian margin behaved as a weak CO2 outgassing zone in austral spring of 2014.
  • Haptophytes were conspicuous along the entire study area, while Trichodesmium was prominent at SBB and diatoms at SBS.
  • CaCO3 production was observed at SBB, whereas seawater dilution dominated the changes of sea surface pCO2 at SBS.
  • Nitrification by Trichodesmium likely allowed increased contribution of haptophytes seen at open ocean oligotrophic waters.
  • Net respiration was the main biogeochemical process regulating sea-air CO2 exchanges in the study area.

Abstract

Hydrographic properties and carbon dioxide partial pressure (pCO2) were measured through underway survey of surface waters during spring 2014, mainly along the Surface Haline Front in the continental shelf-break domain in the southwestern South Atlantic Ocean margin. Additionally, discrete seawater surface samples were collected along the ship track to identify the phytoplankton community and measure seawater chemical properties. This study aims to identify the drivers of the marine CO2‑carbonate chemistry and the role played by the phytoplankton composition on changes in the surface marine carbonate properties and the sea-air CO2 exchanges in two biogeochemical provinces (i.e., South Brazil Bight – SBB, and Southern Brazilian Shelf – SBS) governed by the dynamics of the Brazil Current system in the South Atlantic Ocean. The water masses identified on the surface of the region were Tropical Water (mostly present at offshore regions), Subtropical Shelf Water (mostly present over the continental shelf and slope), and Plata Plume Water (present in the south coastal domain of the SBS). On average, the study area behaved as a weak net CO2 outgassing zone of 1.2 ± 2.3 mmol m−2 d−1 during the spring, despite some subregions behaving as CO2 ingassing zones. The CO2 uptake verified in the SBB was related with mesoscale activity bringing cold waters in the region while CO2 uptake in the continental shelf domain of SBS was associated with the presence of cooler and fresher Plata Plume Water. Changes in total alkalinity and dissolved inorganic carbon at surface were mainly governed by CaCO3 production in SBB and seawater dilution in SBS, although other processes may also have influenced on their spatial variability. The dominant phytoplankton groups were haptophytes (31 %), Trichodesmium (21 %), and picocyanobateria (28 %), corresponding to Synechococcus (17 %) and Prochlorococcus (11 %). The dominance of the diatom group was associated with a decrease in sea surface pCO2 (mainly at coastal zones at southern areas), although the sea-air CO2 exchanges were regulated by cooling process due the presence of Plata Plume Water in that region. Changes in surface pH were related to high concentration of Trichodesmium slicks at offshore zones with the highest microalgae concentration, leading to pH drops of up to 0.4. Trichodesmium slicks likely allowed the development of haptophytes in offshore oligotrophic waters due to its role on N2 fixation. An increase of ∼20 % in the dominance of haptophytes contribution was verified in that situation, which was likely in a post-bloom development stage, since an increased dissolved inorganic carbon content was observed, associated with a prevalence of net respiration processes.

Continue reading ‘Sea-air CO2 exchanges, pCO2 drivers and phytoplankton communities in the southwestern South Atlantic Ocean during spring’

Seawater warming rather than acidification profoundly affects coastal geochemical cycling mediated by marine microbiome

Published 28 November 2024 Science Closed
Tags: , , , , , , , , ,

Highlights

  • The structure and function of coastal microbial communities are influenced by ocean warming and acidification.
  • Elevated temperature more profoundly impacts microbial communities than does acidification.
  • Warming promotes denitrification that may increase nitrogen loss.
  • The nitrogen, sulfur cycles, and carbon-fixation pathways exhibit distinct variation patterns under warming.

Abstract

The most concerning consequences of climate change include ocean acidification and warming, which can affect microbial communities and thus the biogeochemical cycling they mediate. Therefore, it is urgent to study the impact of ocean acidification and warming on microbial communities. In the current study, metagenomics was utilized to reveal how the structure and function of marine microorganisms respond to ocean warming and acidification. In terms of community structure, Non-metric Multidimensional Scaling analysis visualized the similarity or difference between the control and the warming or acidification treatments, but the inter-group differences were not significant. In terms of gene functionality, warming treatments showed greater effects on microbial communities than acidification. After treatment with warming, the relative abundance of genes associated with denitrification increased, suggesting that ocean nitrogen loss can increase with increased temperature. Conversely, acidification treatments apparently inhibited denitrification. Warming treatment also greatly affected sulfur-related microorganisms, increasing the relative abundance of certain sulfate-reducing prokaryote, and enriched microbial carbon-fixation pathways. These results provide information on the response strategies of coastal microorganisms in the changing marine environments.

Continue reading ‘Seawater warming rather than acidification profoundly affects coastal geochemical cycling mediated by marine microbiome’

Chemical interactions between kelp Macrocystis pyrifera and symbiotic bacteria under elevated CO2 condition

Published 26 November 2024 Science Closed
Tags: , , , , , , , ,

Kelps are pivotal to temperate coastal ecosystems, providing essential habitat and nutrients for diverse marine life, and significantly enhancing local biodiversity. The impacts of elevated CO2 levels on kelps may induce far-reaching effects throughout the marine food web, with potential consequences for biodiversity and ecosystem functions. This study considers the kelp Macrocystis pyrifera and its symbiotic microorganisms as a holistic functional unit (holobiont) to examine their collective response to heightened CO2 levels. Over a 4 month cultivation from the fertilization of M. pyrifera gametes to the development of juvenile sporophytes, our findings reveal that elevated CO2 levels influence the structure of the M. pyrifera symbiotic microbiome, alter metabolic profiles, and reshape microbe-metabolite interactions using 16S rRNA amplicon sequencing and liquid chromatography coupled to mass spectrometry analysis. Notably, Dinoroseobacter, Sulfitobacter, Methylotenera, Hyphomonas, Milano-WF1B-44 and Methylophaga were selected as microbiome biomarkers, which showed significant increases in comparative abundance with elevated CO2 levels. Stress-response molecules including fatty-acid metabolites, oxylipins, and hormone-like compounds such as methyl jasmonate and prostaglandin F2a emerged as critical metabolomic indicators. We propose that elevated CO2 puts certain stress on the M. pyrifera holobiont, prompting the release of these stress-response molecules. Moreover, these molecules may aid the kelp’s adaptation by modulating the microbial community structure, particularly influencing potential pathogenic bacteria, to cope with environmental 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 kelps to future climate change.

Continue reading ‘Chemical interactions between kelp Macrocystis pyrifera and symbiotic bacteria under elevated CO2 condition’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources