Global environmental change drives diversity loss and shifts in community structure. A key challenge is to better understand the impacts on ecosystem function and to connect species and trait diversity of assemblages with ecosystem properties that are in turn linked to ecosystem functioning. Here we quantify shifts in species composition and trait diversity associated with ocean acidification (OA) by using field measurements at marine CO2 vent systems spanning four reef habitats across different depths in a temperate coastal ecosystem. We find that both species and trait diversity decreased, and that ecosystem properties (understood as the interplay between species, traits, and ecosystem function) shifted with acidification. Furthermore, shifts in trait categories such as autotrophs, filter feeders, herbivores, and habitat-forming species were habitat-specific, indicating that OA may produce divergent responses across habitats and depths. Combined, these findings reveal the importance of connecting species and trait diversity of marine benthic habitats with key ecosystem properties to anticipate the impacts of global environmental change. Our results also generate new insights on the predicted general and habitat-specific ecological consequences of OA.
Continue reading ‘Functional changes across marine habitats due to ocean acidification’Posts Tagged 'abundance'
Functional changes across marine habitats due to ocean acidification
Published 15 January 2024 Science ClosedTags: abundance, biological response, BRcommunity, calcification, chemistry, community composition, communitymodeling, field, growth, Mediterranean, modeling, otherprocess, performance, photosynthesis, reproduction, vents
Extinction risk of the world’s chondrichthyan fishes: a global assessment of the interplay between anthropogenic factors and marine protected areas
Published 15 January 2024 Science ClosedTags: abundance, biological response, community composition, fish, fisheries, globalmodeling, modeling, otherprocess, socio-economy
Patterns of Chondrichthyes species richness (CSR) are widely recognized as being influenced by environmental conditions. However, untangling the intricate interplay between anthropogenic impacts and spatial patterns of CSR remains a challenging endeavor. In this study, we evaluate the influence of thirteen human-related variables, encompassing human-induced effects and marine protected areas, on global CSR. Additionally, we explore their effects on threatened species, those declining, those utilized and traded, and those facing direct human-induced threats. Utilizing simple, multiple, and simultaneous regression models, we comprehensively investigated the relationship between human-altered variables and marine protected areas on CSR across oceanic regions. Our findings distinctly reveal a compelling convergence of human-related variables with CSR. Notably, factors such as global ocean acidification, demersal destructive practices (e.g., bottom trawling), pelagic low bycatch techniques (e.g., hook and line), and demersal non-destructive high bycatch methods (e.g., pots, traps) exhibit robust negative associations. Intriguingly, a positive association emerges with the presence of marine protected areas. Furthermore, our study underscores the profound impact of diverse human activities on CSR, significantly heightening their vulnerability to threats and imminent extinction risks. These results accentuate the critical significance of conservation strategies centered on marine protected areas, maximizing the optimized preservation of Chondrichthyes across marine ecosystems. In light of these insights, we stress the paramount role of planners and managers in mitigating direct human impacts on marine ecosystems, which is crucial for ensuring the enduring presence of Chondrichthyes across the oceans.
Continue reading ‘Extinction risk of the world’s chondrichthyan fishes: a global assessment of the interplay between anthropogenic factors and marine protected areas’Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction
Published 15 January 2024 Science ClosedTags: abundance, BRcommunity, community composition, otherprocess, paleo, phytoplankton, review
The early Toarcian biotic crisis (∼ 183 Ma), characterized in marine environments by abrupt temperature fluctuations, included a hyperthermal event (Jenkyns Event) with sea-level fluctuations, a carbon cycle perturbation, a crisis of carbonate productivity, and oxygen depleted conditions in some basins, resulting in a second order mass extinction. We suggest that the early Toarcian biotic crisis was key in the evolution of primary producers, including chlorophycean Dasycladales. The effect of the Jenkyns Event on Dasycladales has not been studied previously despite the fact that the impact on many groups of organisms have been the subject of many articles. In this work the stratigraphic distribution of Dasycladalean species from Upper Triassic to end of Jurassic is presented, discussed and compared with climatic fluctuations and sea-level changes.
The end-Triassic Mass Extinction constitutes a main biotic crisis for Dasycladales. All Triassic species became extinct at the Rhaetian-Hettangian boundary, and Dasycladales are not recorded in the lower Hettangian. The diversity of Dasycladales increased after the end-Triassic Mass Extinction and reached a maximum in the Sinemurian. Abrupt climatic changes related to the Pliensbachian/Toarcian boundary and the Jenkyns Event strongly affected the diversity of Dasycladales, very sensitive to sea-level and temperature fluctuations, as sessile benthic organisms inhabiting very shallow marine environments. Dasycladales are not recorded during the Toarcian. Sea-water acidification, enhanced weathering and increased terrigenous input from emerged lands —as well as potentially increased turbidity related to eutrophic conditions in some basins— were additional unfavorable conditions for Dasycladales, augmenting their ecological stress during the early Toarcian. The fragmentation of carbonate platforms in many Tethys paleomargins limited the shallower-water carbonate areas available for Dasycladales.
Warm conditions persisted during the middle and late Toarcian, less severe than during the Jenkyns Event according to oxygen isotopic data, and Dasycladales did not recover until the Bajocian and Bathonian. This biotic crisis for Dasycladales was longer than that of the end-Triassic Mass Extinction. The Callovian-Oxfordian transition was characterized by a cooling episode and a sea-level fall that produced a new biotic crisis affecting Dasycladales. From the middle Oxfordian, the increased temperature and sea-level rise, along with the development of large epeiric platforms, favored the carbonate productivity and diversity of primary producers, including Dasycladales, calcareous nannoplankton, dinoflagellate, calcareous Udoteaceae, and charophyte Clavatoraceae.
Continue reading ‘Incidence of the early Toarcian global change on Dasycladales (Chlorophyta) and the subsequent recovery: comparison with end-Triassic Mass Extinction’Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation
Published 15 January 2024 Science ClosedTags: abundance, biological response, BRcommunity, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton
Increased anthropogenic emissions of carbon dioxide (CO2) have resulted in ocean acidification (OA) that is intertwined with enhanced ocean stratification. Diatoms are assumed to suffer from a more nutrient-limited condition in the future ocean. This study aimed to explore how OA affects the diatom dynamics under nutrient-poor conditions and the ability of diatoms to perceive nutrients (nitrogen, phosphorus, silicon, and trace metals) and cadmium (Cd) stimuli and assimilate nitrogen when receiving nutrients or Cd supplementation. Our study observed that diatom population grown under OA condition declined faster than those grown under ambient condition. Ocean acidification greatly lower intracellular Ca2+ concentration in diatom cells. Intracellular Ca2+ burst was involved in phosphorus accumulation but not in nitrogen, silicon, essential metals, and cadmium uptake. Our data demonstrate slower NO3– assimilation rates of diatoms grown in acidified seawater. Our study also indicates that diatoms have a poor perception of phosphorus availability under OA condition.
Continue reading ‘Survival of nutrient-starved diatoms under ocean acidification: perspective from nutrient sensing, cadmium detection, and nitrogen assimilation’Shallow-water carbonate facies herald the onset of the Palaeocene eocene thermal maximum (Hazara basin, Northern Pakistan)
Published 27 December 2023 Science ClosedTags: abundance, biological response, community composition, corals, otherprocess, paleo, protists, sediment
Highlights
- Pre-PETM-onset neritic carbonates show early signs of what will occur during PETM.
- Corals declined over the study period, whereas foraminifera and red algae increased.
- Similar patterns can be observed in most of the Neotethys.
- Quantitative data are crucial to better understanding palaeo-environmental changes.
Abstract
We investigate the Palaeocene succession of the Hazara Basin (Northern Pakistan) to better understand the impact of climate change on marine carbonate-producing organisms. These shallow-water carbonates, deposited during the Late Palaeocene, before the onset of the Palaeocene-Eocene Thermal Maximum, were studied using a quantitative approach to highlight changes in the skeletal assemblage. We recognise a decrease in the abundance of colonial corals and green calcareous algae and an increase in larger benthic foraminifera and red calcareous algae from the early Thanetian to the late Thanetian. Increasing temperatures may represent a plausible cause for the decline of the more sensitive colonial corals in favor of the more tolerant larger benthic foraminifera. A similar pattern is observed in most successions deposited along the margins of the Neotethys Ocean, suggesting a connection with the Late Palaeocene environmental changes that heralded the PETM hyperthermal event. Our stratigraphic analysis of the Hazara Basin strata suggests that the biotic turnovers occurred during the Palaeocene – Eocene transition started already before the onset of the Palaeocene Eocene Thermal Maximum as recorded by the geochemical proxies.
Continue reading ‘Shallow-water carbonate facies herald the onset of the Palaeocene eocene thermal maximum (Hazara basin, Northern Pakistan)’The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean
Published 18 December 2023 Science ClosedTags: abundance, biogeochemistry, biological response, field, mesocosms, North Pacific, otherprocess, performance, phytoplankton, primary production, reproduction, zooplankton
Gelatinous zooplankton are increasingly recognized to play a key role in the ocean’s biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.
Continue reading ‘The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean’Physio-biochemical and metabolomic analyses of the agarophyte Gracilaria salicornia indicates its tolerance to elevated pCO2 levels
Published 14 December 2023 Science ClosedTags: abundance, algae, biological response, growth, Indian, laboratory, otherprocess, photosynthesis, physiology
Gracilaria salicornia is an agar-producing red macroalga commonly found growing in the intertidal and upper subtidal on various substrates with distribution across the Indo-Pacific. The ability of G. salicornia to survive under harsh conditions suggests potential use as a candidate for sustainable farming and alternative source of livelihood for the local coastal communities under future climate conditions. An earlier study investigated the effects of future predicted pCO2 level on the photosynthesis and respiration of G. salicornia but studies on the metabolomic responses of this alga to constant elevated pCO2 level is lacking. Here, elevated pCO2 level was simulated on G. salicornia for 14 days to compare its growth, photosynthetic efficiency, pigment content, agar properties and metabolite composition under current pCO2 level (∼pH 8.1) and end-of-century future-predicted (∼pH 7.8) pCO2 level. The observed biomass growth, coupled with unaffected photosynthetic parameters and agar-related properties underscore G. salicornia’s ability to adapt to higher pCO2 levels. The modulation of metabolites showcases the alga’s adaptive strategies at elevated pCO2 whereby stress-mediating compounds such as gallic acid and oxalic acid were increased while stress-indicating metabolites such as serine, glycine, and ascorbic acid did not show significant changes. Interestingly, the metabolome profile imply that the alga regulates its metabolism according to culture duration rather than the pCO2 level.
Continue reading ‘Physio-biochemical and metabolomic analyses of the agarophyte Gracilaria salicornia indicates its tolerance to elevated pCO2 levels’Emergent properties of free-living nematode assemblages exposed to multiple stresses
Published 7 December 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, laboratory, mesocosms, metals, multiple factors, nematodes, otherprocess, sediment, South Atlantic, temperature
Highlights
- Co-occurring stressors have significant interactive effects on nematode assemblages.
- Metal contamination surpasses the effects of temperature rise and acidification.
- Temperature rise intensified contamination effects on nematodes.
- Acidification acted as a buffer to the contamination effects on nematodes.
- Nematode genera showed variable responses to contamination.
Abstract
Biological communities are currently facing multi-stressor scenarios whose ecological impacts are challenging to estimate. In that respect, considering the complex nature of ecosystems and types and interaction among stressors is mandatory. Microcosm approaches using free-living nematode assemblages can effectively be used to assess complexity since they preserve the interactions inherent to complex systems when testing for multiple stress effects. In this study, we investigated the interaction effects of three stress factors, namely i-metallic mixture of Cu, Pb, Zn, and Hg (control [L0], low, [L1] and high [L2]), ii- CO2-driven acidification (pH 7.6 and 8.0), and iii- temperature rise (26 and 28 °C), on estuarine free-living nematode assemblages. Metal contamination had the greatest influence on free-living nematode assemblages, irrespective of pH and temperature scenarios. Interestingly, whilst the most abundant free-living nematode genera showed significant decreases in their densities when exposed to contamination, other, less abundant, genera were apparently favored and showed significantly higher densities in contaminated treatments. The augmented densities of tolerant genera may be attributed to indirect effects resulting from the impacts of toxicity on other components of the system, indicating the potential for emergent effects in response to stress. Temperature and pH interacted significantly with contamination. Whilst temperature rise had potentialized contamination effects, acidification showed the opposite trend, acting as a buffer to the effects of contamination. Such results show that temperature rise and CO2-driven acidification interact with contamination on coastal waters, highlighting the importance of considering the intricate interplay of these co-occurring stressors when assessing the ecological impacts on coastal ecosystems.
Continue reading ‘Emergent properties of free-living nematode assemblages exposed to multiple stresses’Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia
Published 30 November 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, morphology, otherprocess, paleo, protists, sediment
The Arctic Ocean in general and the Barents Sea specifically, are highly affected by the human induced carbon dioxide (CO2) emissions and increasing temperatures. Atlantification, caused by an increase in warm Atlantic Water inflow, and polar amplification, caused by a higher impact of the increasing temperatures at high latitudes, have already been observed. Moreover, the Barents Sea has been described as a hotspot for ocean acidification. Ocean acidification is the decrease of pH, calcium carbonate saturation state, and carbonate ion concentration due to an increase in CO2 uptake from the atmosphere by the ocean. This alteration of the carbonate chemistry of the water affects the marine biota, especially planktonic marine calcifiers. They are organisms living in the water column with a shell made of calcium carbonate (CaCO3). They contribute significantly to the carbon cycle by exporting mainly CaCO3 from the surface water to the seabed when they die. The main goal of this thesis is to study the distribution of marine calcifiers (planktonic foraminifers and shelled pteropods) in the Barents Sea and the adjacent Arctic Basin. We have (1) investigated their distribution patterns and contribution to carbon dynamics in the north Svalbard margin and in a seasonal basin in the northern Barents Sea; and (2) reconstructed the foraminiferal production and preservation patterns from the late Holocene in sediment cores from the northern and southern Barents Sea. The results from this thesis show that pteropods are important contributors to the carbon dynamics in all seasons in the northern Barents Sea and northern Svalbard margin. Due to the higher sensitivity of their shells compared to foraminifers, they are more likely to be affected by ocean acidification. Moreover, the abundance of foraminifers in the sediment suggests higher productivity in the southern than in the northern Barents Sea. The almost zero abundances observed in the northern Barents Sea core, combined with the seasonality of marine calcifiers, the water carbonate chemistry, and the presence of agglutinated foraminifers suggest dissolution of CaCO3 in the sediment. Due to the use of their shells in paleoceanography, further investigations of CaCO3 dissolution are needed to use them as proxies for the reconstruction of the paleoenvironmental and paleoclimatic conditions in the Barents Sea.
Continue reading ‘Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia’Changes in the macrobenthic infaunal community of the Southern California continental margin over five decades in relation to oceanographic factors
Published 23 November 2023 Science ClosedTags: abundance, biological response, BRcommunity, mollusks, North Pacific
Climate change has altered the physiochemical conditions of the coastal ocean but effects on infaunal communities have not been well assessed. Here, we used multivariate ordination to examine temporal patterns in benthic community composition from 4 southern California continental shelf monitoring programs that range in duration from 30 to 50 yr. Temporal changes were compared to variations in temperature, oxygen, and acidification using single-taxon random forest models. Species richness increased over time, coupled with a decline in overall abundance. Continental shelf macrobenthic communities from the 2010s comprised a broader array of feeding guilds and life history strategies than in the 1970s. Changing water temperature was associated with northward shifts in geographic distribution and increases in species abundance, while acidification was associated with southward shifts and declines in abundance of other species. Acidification was also associated with changes in depth distribution of benthic fauna, with shelled molluscs declining in abundance at depths most associated with increasing exposure to acidification. This broad-scale community-level analysis establishes causal hypotheses that set the stage for more targeted studies investigating shifts in abundance or distribution for taxa that appear to be responding to climate change-related disturbances.
Continue reading ‘Changes in the macrobenthic infaunal community of the Southern California continental margin over five decades in relation to oceanographic factors’The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean
Published 22 November 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, chemistry, communitymodeling, field, mesocosms, modeling, morphology, North Atlantic, otherprocess, photosynthesis, phytoplankton, reproduction, zooplankton
Gelatinous zooplankton are increasingly recognized to play a key role in the ocean’s biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.
Continue reading ‘The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean’Short-term ocean acidification decreases pulsation and growth of the widespread soft coral Xenia umbellata
Published 20 November 2023 Science ClosedTags: abundance, biological response, corals, growth, laboratory, morphology, mortality, otherprocess, performance, photosynthesis, physiology, protists, respiration
Coral reefs may experience lower pH values as a result of ocean acidification (OA), which has negative consequences, particularly for calcifying organisms. Thus far, the effects of this global factor have been mainly investigated on hard corals, while the effects on soft corals remain relatively understudied. We therefore carried out a manipulative aquarium experiment for 21 days to study the response of the widespread pulsating soft coral Xenia umbellata to simulated OA conditions. We gradually decreased the pH from ambient (~8.3) to three consecutive 7-day long pH treatments of 8.0, 7.8, and 7.6, using a CO2 dosing system. Monitored response variables included pulsation rate, specific growth rate, visual coloration, survival, Symbiodiniaceae cell densities and chlorophyll a content, photosynthesis and respiration, and finally stable isotopes of carbon (C) and nitrogen (N) as well as CN content. Pulsation decreased compared to controls with each consecutive lowering of the pH, i.e., 17% at pH 8.0, 26% at pH 7.8 and 32% at pH 7.6, accompanied by an initial decrease in growth rates of ~60% at pH 8.0, not decreasing further at lower pH. An 8.3 ‰ decrease of δ13C confirmed that OA exposed colonies had a higher uptake and availability of atmospheric CO2. Coral productivity, i.e., photosynthesis, was not affected by higher dissolved inorganic C availability and none of the remaining response variables showed any significant differences. Our findings suggest that pulsation is a phenotypically plastic mechanism for X. umbellata to adjust to different pH values, resulting in reduced growth rates only, while maintaining high productivity. Consequently, pulsation may allow X. umbellata to inhabit a broad pH range with minimal effects on its overall health. This resilience may contribute to the competitive advantage that soft corals, particularly X. umbellata, have over hard corals.
Continue reading ‘Short-term ocean acidification decreases pulsation and growth of the widespread soft coral Xenia umbellata’The modulating role of natural variability in the biological response to ocean acidification
Published 16 November 2023 Science ClosedTags: abundance, biological response, calcification, echinoderms, growth, laboratory, morphology, mortality, North Atlantic, otherprocess, reproduction
Ocean acidification (OA) is the consequence of the uptake of excess carbon dioxide from the atmosphere. Along the coastal zone, ocean acidification is influenced by other processes such as biology and currents, leading to high levels of natural variability in pH. While the impact of pH on marine organisms is better resolved, the modulating role of this natural variability is poorly understood. This master’s thesis aimed at evaluating diel pH fluctuations using the larval stages of the brittle star Amphiura filiformis. Results revealed the importance of acknowledging pH variations with individuals exhibiting higher fitness. Diel analyses also underscored the existence of an intrinsic circadian cycle where larvae would grow more during the daytime than nighttime, possibly explained by better conditions encountered during the day. In addition, we demonstrated a carryover effect that could also be associated with a stage sensitivity. We suggest that future studies should integrate natural variations and delve into the different species’ adaptations as they have an important role in the biological responses to upcoming OA.
Continue reading ‘The modulating role of natural variability in the biological response to ocean acidification’Infestation of cultivated Pacific oysters by shell-boring polychaetes along the US West Coast: Prevalence is associated with season, culture method, and pH
Published 10 November 2023 Science ClosedTags: abundance, annelids, biological response, chemistry, community composition, field, molecular biology, mollusks, North Pacific, otherprocess, physiology
Shell-boring polychaetes have contributed to the collapse of several mariculture operations around the world. These pests burrow into the shells of bivalves, creating mud blisters that are unappealing to consumers and which make oysters less valuable on the half-shell market. The US Pacific region produces 38% of the farmed shellfish in the US, making it important to understand the prevalence and drivers of parasite infestation in this region. We sampled Pacific oysters (Crassostrea gigas; n = 4158) from 35 shellfish farms over four seasons (two winters and two summers) in four states (northern California (CA), Oregon (OR), Washington (WA), and Alaska (AK)) to document the prevalence of shell-boring polychaetes. We extracted worms from infested oysters and used mitochondrial (CO1, n = 139) and nuclear (18S rRNA, n = 224) markers to determine species identities. To identify the environmental correlates that were associated with infestation, we pooled environmental data from seven monitoring stations in Washington. We assessed whether seawater surface temperature (SST), salinity, and pH were associated with shell-boring polychaete infestation. Our sampling confirmed the presence of Polydora websteri in the study region, in addition to four other species of shell-boring polychaetes and seven unidentified haplotypes. The mean prevalences across all shell-boring polychaete species ranged from 23 to 45% across seasons between states. In general, prevalence was higher in the winter and among oysters cultured on the bottom versus in tumbled bags, but these results varied across states. We also found greater infestation by shell-boring polychaetes at less acidified sites (pH = 8–8.2). This work is the most comprehensive dataset to characterize shell-boring polychaetes along the US West Coast, providing an important baseline of prevalence, species distribution, and environmental associations.
Continue reading ‘Infestation of cultivated Pacific oysters by shell-boring polychaetes along the US West Coast: Prevalence is associated with season, culture method, and pH’Deciphering the evolvement of microbial communities from hydrothermal vent sediments in a global change perspective
Published 8 November 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, Mediterranean, mesocosms, otherprocess, physiology, prokaryotes, respiration, sediment, vents
Microbial communities first respond to changes of external environmental conditions. Observing the microbial responses to environmental changes in terms of taxonomic and functional biodiversity is therefore of great interest, particularly in extreme environments, where the already extreme conditions can become even harsher. In this study, sediment samples from three different shallow hydrothermal vents in Levante Bay (Vulcano Island, Aeolian Islands, Italy) were used to set up microcosm experiments with the aim to explore the microbial dynamics under changing conditions of pH and redox potential over a 90-days period. The leading hypothesis was to establish under microcosm conditions whether the starting microbial communities of the sediments evolved differently depending on their origin. To profile the dynamics of microbial populations over time, biodiversity, enzymatic profile, total cell abundance estimations, total/respiring cell ratio were estimated by using different approaches. An evident change in the microbial community structure was observed, mainly in the microcosm containing the sediment from the most acidified site, which was characterized by a highly diversified microbial community (in prevalence composed of Thermotoga, Desulfobacterota, Planctomycetota, Synergistota and Deferribacterota). An increase in microbial resistant forms (e.g., spore-forming species) with anaerobic metabolism was detected in all experimental conditions. Differential physiological responses characterized the sedimentary microbial communities. Proteolytic activity appeared to be stimulated under microcosm conditions, whereas the alkaline phosphatase activity was significantly depressed at low pH values, like those that were measured at the station showing intermediate pH-conditions. The results confirmed a differential response of microbial communities depending on the starting environmental conditions.
Continue reading ‘Deciphering the evolvement of microbial communities from hydrothermal vent sediments in a global change perspective’The response of tuna to ocean acidification in Indonesian waters (case study: Gulf of Bone)
Published 7 November 2023 Science ClosedTags: abundance, biological response, chemistry, fish, morphology, otherprocess, review, South Pacific
There is growing concern about ocean acidification (decrease in pH of the ocean as a result of increased atmospheric carbon dioxide absorption by ocean) as one threat of climate change that may have significant impacts on marine organisms, such as fish. Recent studies suggest that adult fish are not directly impaired by OA, however, for the earliest fish stages, a number of direct effects have been observed. Hence, we observed the response of OA on monthly larvae density of yellowfin tuna in the Indonesian water, especially in the Gulf of Bone. The pH on the total scale (pH) and surface aqueous partial pressure of CO2 (pCO2) data were derived from Copernicus Marine Environment Monitoring Service (CMEMS) model product; meanwhile, fish data from 2014-2016 were derived from daily Infrastructure Development for Space Oceanography (INDESO) tuna population model outputs. This study indicates that the variability of pCO2 tends to increase while the pH tends to decline. During the northwest monsoon periods, pH in the Gulf of Bone tends to be lower. The larvae and juvenile of yellowfin tuna in the Gulf of Bone waters have various spatial correlations with pH and pCO2. Both have the potential to decrease with the declined pH and elevated pCO2.
Continue reading ‘The response of tuna to ocean acidification in Indonesian waters (case study: Gulf of Bone)’CO2 enrichment and excess nitrogen supply synergistically increase toxicity of marine dinoflagellate Alexandrium minutum
Published 2 November 2023 Science ClosedTags: abundance, biological response, laboratory, multiple factors, North Pacific, nutrients, otherprocess, physiology, phytoplankton
Discharges of CO2 and nutrients by anthropogenic activities have notable contributions to CO2 enrichment and eutrophication in coastal systems. Following our previous study that toxic dinoflagellate Alexandrium minutum will increase their growth rate and cellular toxicity under elevated levels of CO2, we further examined the joint effects of CO2 enrichment and excess nitrogen supply through a 29-day experiment under three CO2 levels (400, 800 and 1200 ppm) with a high N/P ratio of 80. It was found that the two factors have synergistical effects in promoting the increase of cellular toxicity. There were remarkable increases in toxin biosynthesis of paralytic shellfish toxins when both intracellular and extracellular toxins were considered. Under the joint impacts of CO2 enrichment and excess nitrogen supply, the apparent transformation from gonyautoxins2/3 to gonyautoxins1/4, with much higher toxicity and lower rate of release, is likely to be another major factor accounting for the increasing toxicity. The increasing growth rate and cellular toxicity of A. minutum under the scenarios with elevated concentrations of both CO2 and nitrogen in coastal systems in the future will increase the risks associated with such toxic algal blooms.
Continue reading ‘CO2 enrichment and excess nitrogen supply synergistically increase toxicity of marine dinoflagellate Alexandrium minutum’Impact of ocean acidification on the gut histopathology and intestinal microflora of Exopalaemon carinicauda
Published 30 October 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, crustaceans, laboratory, molecular biology, morphology, North Pacific, otherprocess, physiology, prokaryotes
Marine crustaceans are severely threatened by environmental factors such as ocean acidification, but, despite the latter’s negative impact on growth, molting, and immunity, its effects on intestinal microflora remain poorly understood. This work studied the gut morphology and intestinal microflora of Exopalaemon carinicauda, grown in seawater of different pH levels: 8.1 (control group), 7.4 (AC74 group), and 7.0 (AC70 group). Ocean acidification was found to cause intestinal damage, while significantly altering the microflora’s composition. However, the α-diversity did not differ significantly between the groups. At the phylum level, the relative abundance of Proteobacteria decreased in the acidification groups, while at the genus level, the relative abundance of Sphingomonas decreased. Babeliales was a prominent discriminative biomarker in the AC74 group, with Actinobacteriota, Micrococcales, Beijerinckiaceae, Methylobacterium, and Flavobacteriales being the main ones in the AC70 group. The function prediction results also indicated an enrichment of pathways related to metabolism for the acidification groups. At the same time, those related to xenobiotics’ biodegradation and metabolism were inhibited in AC74 but enhanced in AC70. This is the first study examining the impact of ocean acidification on the intestinal microflora of crustaceans. The results are expected to provide a better understanding of the interactions between shrimp and their microflora in response to environmental stressors.
Continue reading ‘Impact of ocean acidification on the gut histopathology and intestinal microflora of Exopalaemon carinicauda’pCO2 decrement through alkalinity enhancement and biological production in a shallow-water ecosystem constructed using steelmaking slag
Published 25 October 2023 Science ClosedTags: abundance, algae, biological response, chemistry, field, mesocosms, mitigation, North Pacific, otherprocess
Ocean-based carbon dioxide removal has gained immense attention as a countermeasure against climate change. The enhancement of ocean alkalinity and the creation of new blue carbon ecosystems are considered effective approaches for this. To evaluate the function of steelmaking slag from the viewpoints of CO2 reduction and creation of new blue carbon ecosystems, we conducted a comparative experiment using two mesocosms that replicated tidal-flats and shallow-water ecosystems. Initially, approximately 20 seagrasses (Zostera marina) were transplanted into the shallow-water area in the mesocosm tanks. The use of steelmaking slag is expected to increase the pH by releasing calcium and mitigate turbidity by solidifying dredged soil. In the experimental tank, where dredged soil and steelmaking slag were utilized as bed materials, the pH remained higher throughout the experimental period compared with the control tank, which utilized only dredged soil. As a result, pCO2 remained consistently lower in the experimental tank due to mainly its alkaline effect (March 2019: −10 ± 6 μatm, September 2019: −130 ± 47 μatm). The light environment in the control tank deteriorated due to high turbidity, whereas the turbidity in the experimental tank remained low throughout the year. The number of seagrass shoots in the experimental tank was consistently approximately 20, which was higher than that in the control tank. Additionally, more seaweed and benthic algae were observed in the experimental tank, indicating that it was more conducive to the growth of primary producers. In conclusion, tidal-flat and shallow-water ecosystems constructed using dredged soil and steelmaking slag are expected to enhance CO2 uptake and provide a habitat for primary producers that is superior to those constructed using dredged soil only.
Continue reading ‘pCO2 decrement through alkalinity enhancement and biological production in a shallow-water ecosystem constructed using steelmaking slag’Assessing the impact of CO2 equilibrated ocean alkalinity enhancement on microbial metabolic rates in an oligotrophic system
Published 25 October 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, mesocosms, mitigation, North Pacific, otherprocess, photosynthesis, phytoplankton, primary production, prokaryotes, respiration
Ocean Alkalinity Enhancement (OAE) is a Negative Emissions Technology (NET) that shows significant potential for climate change mitigation. By increasing the bicarbonate ion concentration in ocean water, OAE could enhance long-term carbon storage and mitigate ocean acidification. However, the side effects and/or potential co-benefits of OAE on natural planktonic communities remain poorly understood. To address this knowledge gap, a mesocosm experiment was conducted in the oligotrophic waters of Gran Canaria. A CO2-equilibrated Total Alkalinity (TA) gradient was employed in increments of 300 µmol·L-1, ranging from ~2400 to ~4800 µmol·L-1. This study represents the first attempt to evaluate the potential impacts of OAE on planktonic communities under natural conditions. The results show that Net Community Production (NCP), Gross Production (GP), Community Respiration (CR) rates, as well as the metabolic balance (GP:CR), did not exhibit a linear response to the whole alkalinity gradient. Instead, significant polynomial and linear regression models were observed for all rates up to ∆TA1800 µmol·L-1, in relation to the Dissolved Inorganic Carbon (DIC) concentrations. Notably, the ∆TA1500 and 1800 µmol·L-1 treatments showed peaks in NCP shifting from a heterotrophic to an autotrophic state, with NCP values of 4 and 8 µmol O2 kg-1 d-1, respectively. These peaks and the optimum curve were also reflected in the nanophytoplankton abundance, size-fractionated chlorophyll a and 14C uptake data. Furthermore, abiotic precipitation occurred in the highest treatment after day 21 but no impact on the measured parameters was detected. Overall, a damaging effect of CO2-equilibrated OAE in the range applied here, on phytoplankton primary production, community metabolism and composition could not be inferred. In fact, a potential co-benefit to OAE was observed in the form of the positive curvilinear response to the DIC gradient up to the ∆TA1800 treatment. Further experimental research at this scale is key to gain a better understanding of the short and long-term effects of OAE on planktonic communities.
Continue reading ‘Assessing the impact of CO2 equilibrated ocean alkalinity enhancement on microbial metabolic rates in an oligotrophic system’
