Along with human activities, an overwhelming amount of carbon dioxide (CO2) has been released into the atmosphere and subsequently absorbed by the ocean through the air–sea interface, leading to a significant decrease in oceanic pH, known as global ocean acidification (OA). Over time, the continued pH decrease, together with a major change in the carbonate system, has created serious risks for a wide range of marine organisms and the ecosystem, and therefore the near-future OA scenario is increasingly and intensively emphasized. As the ecologically dominant species in various oceanic environments such as estuaries and the coral reef, marine mollusks are at great risk due to the altered innate immune response under the near-future OA condition. Furthermore, because infectious disease in marine mollusks is the result of the joint action of host and pathogenic microbes, the impacts of the OA on the host, microbes, and their interactions may also affect the immune response of marine mollusks. In addition, other environmental stressors, such as high temperature, hypoxia, and pollutants, may exert combined impacts of OA on the immunity of marine mollusks. Thus, this chapter focuses on the following fields: (1) the impacts of OA on the cellular and humoral immune response of marine mollusks; (2) the potential affecting mechanisms of OA on the immunity of marine mollusks; (3) the host–microbe interactions in marine mollusks under OA scenario; and (4) the combined effects of OA and other environmental stressors on the immunity of marine mollusks.
Continue reading ‘Chapter 5 – Impacts of ocean acidification on the immunity and host–microbe interactions in marine mollusks’Posts Tagged 'prokaryotes'
Chapter 5 – Impacts of ocean acidification on the immunity and host–microbe interactions in marine mollusks
Published 22 October 2024 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, mollusks, otherprocess, physiology, prokaryotes
Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum
Published 26 September 2024 Science ClosedTags: biological response, BRcommunity, growth, laboratory, morphology, performance, prokaryotes
The acidification of the ocean caused by the diffusion of anthropogenic carbon dioxide (CO2) into seawater has been believed to threaten the stability of the marine ecosystem. As one of the major contributors to the primary production in oligotrophic oceans, the response of Trichodesmium to the acidification of the ocean has attracted a lot of attention. Therefore, in this study, we applied physiological and biochemical methods to identify the influences of high pCO2 and low pH conditions on the growth of T. erythraeum. Our results showed that the low pH during the acidification of the ocean was the main factor inhibiting the growth of T. erythraeum. In addition, low pH caused oxidative stress to T. erythraeum, as evidenced by the increase of the reactive oxygen species and antioxidant enzyme’s activities. The activity of carbonic anhydrase (CA) enzyme is dually regulated by pCO2 and pH, and T. erythraeum can adapt to different levels of pCO2 and pH in seawater by flexibly adjusting CA enzyme activity. We also discovered that the stimulatory effect of high pCO2 on the exopolysaccharide (EPS) content of T. erythraeum outweighed the inhibitory effect of low pH during the process of ocean acidification. In conclusion, this study systematically revealed the effects of high pCO2 and low pH caused by the acidification of the ocean on the growth and EPS of T. erythraeum. These results provide new insights into the response mechanisms of T. erythraeum in the acidified ocean under future climate conditions.
Continue reading ‘Impact of low pH/high pCO2 on the physiological response and exopolysaccharide content in cyanobacteria Trichodesmium erythraeum’Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change
Published 19 September 2024 Science ClosedTags: biological response, laboratory, Mediterranean, mollusks, morphology, multiple factors, nutrients, physiology, prokaryotes
Climate change has presented a serious problem in recent times, which is why a new approach is being sought in terms of aquacultural food quality. In this study, the influence of temperature increase (by 2 °C) and pH decrease (by 0.2) was investigated on the queen scallop, Aequipecten opercularis (Linnaeus, 1758). Furthermore, the effect of a food-enriched diet with the probiotic culture Lactiplantibacillus plantarum I was assessed in climate-changed conditions. Scallops’ morphometric parameters were measured before the experimental setup and after one month of being kept in controlled conditions. Morphometric parameters included the elongation index, compactness index, convexity index, density index, condition index, meat yield, gonadosomatic index, adductor muscle index, and hepatosomatic index. Climate-changed conditions had no effect on the scallop condition index, meat yield, or hepatosomatic index. Nevertheless, the addition of probiotics to their diet had a positive effect on the queen scallops cultivated under conditions of climate change, influencing positive allometry and the increase of the gonadosomatic indices. On the other hand, the same conditions negatively affected the adductor muscle index of the scallops. To conclude, in the context of climate change conditions, queen scallops could be a good organism of choice that can be very well adapted to the changed environmental conditions, especially with the addition of the lactic acid bacteria culture Lpb. plantarum I.
Continue reading ‘Lactiplantibacillus plantarum I induces gonad growth in the queen scallop Aequipecten opercularis (Linnaeus, 1758) under conditions of climate change’Nearshore microbial communities of the Pacific Northwest coasts of Canada and the U.S.
Published 6 September 2024 Science ClosedTags: biological response, chemistry, community composition, field, molecular biology, North Pacific, otherprocess, phytoplankton, prokaryotes
A survey of marine pelagic coastal microbial communities was conducted over a large geographic latitude range, from Cape Mendocino in northern California USA to Queen Charlotte Sound in British Columbia Canada, during the spring to summer transition. DNA metabarcoding and flow cytometry were used to characterize microbial communities. Physical and chemical oceanography indicated moderate conditions during the survey with no widespread upwelling, marine heat wave, or other extreme conditions. However, four locations displayed features approaching acidified conditions: Heceta Head, Newport, Copalis Beach, and Cape Flattery. Although bacterial and archaeal communities at the Juan de Fuca canyon and northward had high similarity, those south of the Juan de Fuca canyon were well differentiated from each other. In contrast, eukaryotic microbial communities exhibited stronger geographic differentiation than bacterial and archaeal communities across the extent of the survey. Seawater parameters that were best predictors of bacterial and archaeal community structure were temperature, pH, and dissolved inorganic nutrients (nitrate, phosphate, silicate), while those that were best predictors of eukaryotic microbial community structure were salinity, dissolved oxygen, total alkalinity, and dissolved inorganic nutrients (nitrite, silicate). Although five bacterial and archaeal indicators for potentially corrosive waters were identified (Colwellia, Nitrosopumilus, Nitrosopelagicus, Sup05 cluster, Sva0996 marine group), no eukaryotic microbial indicators were found. Potentially pathogenic taxa detected in the survey included four disease-causing bacteria for mammals, finfish, and/or shellfish (Coxiella, Flavobacterium, Francisella, Tenacibaculum), sixteen genera of microalgae capable of producing biotoxins, and fifteen parasitic species. This study demonstrates the value of coordinating microbial sampling and analysis with broad-scale oceanographic surveys to generate insights into community structures of these important pelagic trophic levels.
Continue reading ‘Nearshore microbial communities of the Pacific Northwest coasts of Canada and the U.S.’Low pH enhances germination of eelgrass (Zostera marina L.) seeds despite ubiquitous presence of Phytophthora gemini
Published 28 August 2024 Science ClosedTags: biological response, BRcommunity, chemistry, laboratory, North Atlantic, phanerogams, prokaryotes, reproduction
Highlights
- Lowered pH levels positively influence eelgrass seed germination, indicating a potential adaptive response to ocean acidification.
- Despite favorable germination conditions, the virulence of Phytophthora gemini remains unaffected, leading to widespread infection in eelgrass populations regardless of pH levels.
- The study shows the persistent threat of Phytophthora gemini to eelgrass restoration efforts, emphasizing the need for innovative disease management strategies alongside considerations of ocean acidification impacts on coastal ecosystems.
Abstract
Seagrasses are foundation species in coastal ecosystems promoting biodiversity and community structure. Future marine carbonate chemistry under ocean acidification may enhance seagrass physiology, but little is known about how reproductive ecology and disease will integrate into future ocean conditions. A novel pathogen, Phytophthora gemini, infects >90% of eelgrass, Zostera marina, surveyed in Northern Atlantic and Mediterranean populations reducing annual germination 6-fold. Our study investigated the combined effects of ocean acidification and P. gemini infection on germination of eelgrass seeds. We conducted a two-level factorial experiment crossing four pH levels (∆0, – ∆0.3, – ∆0.6, -∆0.9; relative to the average pH at the sampling site) with three infection levels (infected, non-infected, exposed) to determine germination rate and infection response. Prior to experimentation, flowering shoots were collected and held in flow-through seawater tanks where seeds ripened naturally. Once collected, seeds were held in copper sulfate solution (27.37 ± 1.57 ppt) and stored in darkness to mimic winter dormancy (4 oC). Before the start of the experiment, viable seeds were cultured on oomycete selective growth media to determine infection status. By the end of the experiment, 100% of tested seeds, regardless of treatment, contained P. gemini. Germination rate significantly increased with decreased pH. Our findings indicate that P. gemini is not inhibited by ecologically relevant changes to carbonate chemistry and standard handling practices can result in effective and highly virulent disease transmission. These results confirm perennial populations of eelgrass are susceptible to infection and alerts conservationists to additional considerations necessary for successful eelgrass restoration.
Continue reading ‘Low pH enhances germination of eelgrass (Zostera marina L.) seeds despite ubiquitous presence of Phytophthora gemini’Assessing the effects of warming and carbonate chemistry parameters on marine microbes in the Gulf of Mexico through basin-scale DNA metabarcoding
Published 2 August 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, North Atlantic, otherprocess, physiology, prokaryotes
Ocean acidification and warming threaten marine life, yet the impact of these processes on microbes remains unclear. Here, we performed basin-scale DNA metabarcoding of prokaryotes (16S V4–V5) and protists (18S V9) in the Gulf of Mexico and applied generalized linear models to reveal group-specific environmental correlates of functionally diverse microbes. Models supported prior physiological trends for some groups, like positive temperature effects on SAR11 and SAR86, and a positive effect of pH on Prochlorococcus that implied a negative response to decreasing pH. New insights were revealed for protists, like Syndiniales and Sagenista (e.g., positive pH effects), which offset positive relationships with temperature and reinforced the importance of considering multiple stressors simultaneously. Indicator analysis revealed phytoplankton, like Ostreococcus sp. and Emiliania huxleyi, that were associated with more acidic waters and may reflect candidate indicators of ocean change. Our findings highlight the need for sustained microbial sampling in marine systems, with implications for carbon export, nutrient cycling, and ecosystem health.
Continue reading ‘Assessing the effects of warming and carbonate chemistry parameters on marine microbes in the Gulf of Mexico through basin-scale DNA metabarcoding’Organic matter decay and bacterial community succession in mangroves under simulated climate change scenarios
Published 24 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, morphology, otherprocess, physiology, prokaryotes, sediment, South Atlantic
Mangroves are coastal environments that provide resources for adjacent ecosystems due to their high productivity, organic matter decomposition, and carbon cycling by microbial communities in sediments. Since the industrial revolution, the increase of Greenhouse Gases (GHG) released due to fossil fuel burning led to many environmental abnormalities such as an increase in average temperature and ocean acidification. Based on the hypothesis that climate change modifies the microbial diversity associated with decaying organic matter in mangrove sediments, this study aimed to evaluate the microbial diversity under simulated climate change conditions during the litter decomposition process and the emission of GHG. Thus, microcosms containing organic matter from the three main plant species found in mangroves throughout the State of São Paulo, Brazil (Rhizophora mangle, Laguncularia racemosa, and Avicennia schaueriana) were incubated simulating climate changes (increase in temperature and pH). The decay rate was higher in the first seven days of incubation, but the differences between the simulated treatments were minor. GHG fluxes were higher in the first ten days and higher in samples under increased temperature. The variation in time resulted in substantial impacts on α-diversity and community composition, initially with a greater abundance of Gammaproteobacteria for all plant species despite the climate conditions variations. The PCoA analysis reveals the chronological sequence in β-diversity, indicating the increase of Deltaproteobacteria at the end of the process. The GHG emission varied in function of the organic matter source with an increase due to the elevated temperature, concurrent with the rise in the Deltaproteobacteria population. Thus, these results indicate that under the expected climate change scenario for the end of the century, the decomposition rate and GHG emissions will be potentially higher, leading to a harmful feedback loop of GHG production. This process can happen independently of an impact on the bacterial community structure due to these changes.
Continue reading ‘Organic matter decay and bacterial community succession in mangroves under simulated climate change scenarios’Impact of ocean acidification on the intestinal microflora of Sinonovacula constricta
Published 23 July 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess, physiology, prokaryotes
The intestinal microflora of host, vital for nutrient absorption and immune regulation, can experience dysbiosis under environmental stress, thereby potentially enhancing host susceptibility to pathogenic invasion. The impact of ocean acidification on bivalves is substantial, yet its effects on the intestinal microflora remain poorly understood. This study employed high-throughput 16S rRNA sequencing technology to investigate the variations in the intestinal microflora of Sinonovacula constricta between the control group (CON) and the seawater acidification group (OA) at different time points.After exposure to OA, changes in the composition of the intestinal microflora of S. constricta were observed, with no significant difference in α-diversity between the acidified and control groups. At the phylum level, there was an increase in the abundance of Proteobacteria, while Cyanobacteria decreased in the OA14d and OA35d groups. Additionally, the relative abundance of Firmicutes increased in the OA7d and OA35d groups. At the genus level, the relative content of Pseudomonas was lower than that in the control group, while the relative content of Flavobacterium, Acinetobacter, and Enterobacter showed a gradual increasing trendin the OA14d and OA35d groups.. LEfSe analysis identified Serpens as discriminative biomarkers in the OA7d group, while Enterobacteriales, Rhodobacteraceae and Martvita were biomarker in the OA14d group, and Serpens, Acidibacteria and Aeromonadaceae were biomarker in the OA35d group. Functional prediction results indicated significant enrichment in metabolic pathways at different time points following ocean acidification stress… The pathways involved in biosynthesis in the OA14d group and in sucrose degradation in the OA35d group were significantly disrupted. These results suggest that OA stress can have adverse effects on the intestinal microflora of S. constricta, but it does not cause obvious damage to the digestive system. This study provides new insights into the intestinal microflora of marine bivalves under acidification stress.
Continue reading ‘Impact of ocean acidification on the intestinal microflora of Sinonovacula constricta’Uptake of dissolved inorganic nitrogen and N2 fixation by Crocosphaera watsonii under climate change scenarios
Published 22 July 2024 Science ClosedTags: abundance, biological response, chemistry, growth, laboratory, multiple factors, nitrogen fixation, otherprocess, physiology, prokaryotes, temperature
The response of N2 fixation to projected future conditions in the ocean cannot be reliably predicted to date. We conducted a minicosm experiment with pre-acclimated cultures of the globally significant diazotroph Crocosphaera watsonii strain WH8501 (“Crocosphaera”). PH and temperature were altered simultaneously to match the RCP scenarios 4.5 and 6 and investigate a more realistic future scenario compared to studies that focus on changes of a single stressor only. The cell abundance and nitrogen metabolism of Crocosphaera was monitored over 5 days. Our results imply that Crocosphaera is able to simultaneously perform N2 fixation and assimilate dissolved inorganic nitrogen (DIN, i.e., nitrate and ammonium) under all the conditions tested and implies a competition with non-diazotrophic phytoplankton for DIN, which should be further investigated. Using NanoSIMS analysis of single cells, our results point towards a preference for DIN assimilation over N2 fixation under more acidic and warmer conditions. Overall, our results show that while the combined alteration of pH and temperature had a negative effect on the diazotroph’s growth and N2 fixation, Crocosphaera is likely to cope well with conditions in the future ocean. The high intra-population variability in nitrogen assimilation pathways may give this species the flexibility to quickly react to environmental changes.
Continue reading ‘Uptake of dissolved inorganic nitrogen and N2 fixation by Crocosphaera watsonii under climate change scenarios’Marine Roseobacter clade bacteria decelerate the conversion of dimethylsulfoniopropionate under ocean acidification
Published 2 July 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, laboratory, molecular biology, physiology, prokaryotes
Ocean acidification has been an alarming issue that is jeopardizing the marine environment and ecology. Marine Roseobacter clade bacteria mediate important biogeochemical cycles in the ocean and are an indispensable sector of marine ecology. However, seldom has research attempted to unveil the effects of ocean acidification on bacteria in the Roseobacter clade, leaving a gap in understanding the environmental and ecological impacts of global climate change and ocean acidification. Here, we evaluated the effects of acidification on Roseovarius nubinhibens, a representative strain in the marine Roseobacter clade. We found that a marginal decrease in pH was influential enough to inhibit cell growth and induce cellular responses at the system level. We determined the essential role of glutathione metabolism in response to a lower pH via combined RNA sequencing, biochemical analysis, and CRISPR-Cas genome editing. Finally, we observed that a lower pH decelerated the metabolism of dimethylsulfoniopropionate, a key precursor for the global sulfur cycle and the formation of clouds, which would probably hasten global climate changes. Taking together, we believe that our study provides a missing puzzle piece toward a comprehensive understanding of the effects of global climate change and ocean acidification on our planet.
Continue reading ‘Marine Roseobacter clade bacteria decelerate the conversion of dimethylsulfoniopropionate under ocean acidification’Response and acclimation of cyanobacteria to acidification: a comprehensive review
Published 26 June 2024 Science ClosedTags: physiology, prokaryotes, review
Highlights
- Examining the effects of acidification on both ecosystems and cyanobacteria
- Understanding cyanobacteria’s acclimation mechanisms and responses to acidification stress
- Strategies to enhance acid resistance in cyanobacteria and future research directions
Abstract
Cyanobacteria, as vital components of aquatic ecosystems, face increasing challenges due to acidification driven by various anthropogenic and natural factors. Understanding how cyanobacteria adapt and respond to acidification is crucial for predicting their ecological dynamics and potential impacts on ecosystem health. This comprehensive review synthesizes current knowledge on the acclimation mechanisms and responses of cyanobacteria to acidification stress. Detailly, ecological roles of cyanobacteria were firstly briefly concluded, followed by the effects of acidification on aquatic ecosystems and cyanobacteria. Then the review focuses on the physiological, biochemical, and molecular strategies employed by cyanobacteria to cope with acidification stress, highlighting key adaptive mechanisms and their ecological implications. Finally, a summary of strategies to enhance acid resistance in cyanobacteria and future directions was discussed. Utilizing omics data and machine learning technology to build a cyanobacterial acid regulatory network allows for predicting the impact of acidification on cyanobacteria and inferring its broader effects on ecosystems. Additionally, acquiring acid-tolerant chassis cells of cyanobacteria through innovative techniques facilitates the advancement of environmentally friendly production of acidic chemicals. By synthesizing empirical evidence and theoretical frameworks, this review aims to elucidate the complex interplay between cyanobacteria and acidification stressors, providing insights for future research directions and ecosystem management strategies.
Continue reading ‘Response and acclimation of cyanobacteria to acidification: a comprehensive review’Sulphate reduction and carbonate precipitation in a high-energy algal rim framework
Published 24 June 2024 Science ClosedTags: biogeochemistry, biological response, BRcommunity, chemistry, community composition, corals, laboratory, otherprocess, prokaryotes, South Pacific
Algal ridges are protective features for coral reefs that form through the accretion and encrustation of reef rubble and debris by crustose coralline algae (CCA) and processes of diagenetic cementation. Carbonate precipitation and dissolution dynamics on and within algal ridge frameworks are poorly understood. We studied the surface and subsurface geochemistry of the algal ridge framework at One Tree Island, Australia. Measurable quantities of hydrogen sulphide were detected in most porewater samples collected from bores, indicating a largely anoxic ridge framework. Total alkalinity (TA) and pH measurements indicate that the precipitation of carbonate minerals within the interior of the ridge framework occurs under largely anoxic conditions and is likely to be driven by TA changes associated with sulphate-reducing bacteria. Modelling of porewater hydrogen sulphide concentrations in combination with TA and dissolved inorganic carbon (DIC) indicates anoxic respiration processes produce alkalinity within the algal ridge framework. However, significantly more TA is removed via the precipitation of mineral carbonate, resulting in porewater TA concentrations falling below the open seawater values. The precipitation of mineral carbonate also lowers interstitial water pH, such that pH changes are not solely from organic carbon diagenesis. The simultaneous precipitation and dissolution of carbonate minerals within the algal ridge framework are key to forming and cementing algal ridges, which are important physical protective features for coral reefs.
Continue reading ‘Sulphate reduction and carbonate precipitation in a high-energy algal rim framework’Molecular bases and evolutionary constraints of cellular acid tolerance in cyanobacteria and invertebrates subjected to ocean acidification and other sources of stress (METASTRESS)
Published 14 June 2024 Science ClosedTags: biological response, chemistry, laboratory, Mediterranean, molecular biology, physiology, prokaryotes
The ongoing decreasing surface pH that seas and oceans are facing is termed ocean acidification (OA). The primary reason for this phenomenon is the emission of carbon dioxide (CO2) into the atmosphere from human activities, like the burning of fossil fuels, which has drastically increased since the industrial revolution, reaching higher levels during these decades. This environmental risk is considered among the most hazardous threats to marine ecosystems associated with global change and severely affects marine life worldwide. Responses of marine species to acidified seawaters have been deeply studied and adverse effects at different levels, from single species up to whole communities, have been pointed out. Although OA is clearly posing a threat to marine life, some species have demonstrated the ability to tolerate and thrive in such conditions. Information on the mechanisms driving the tolerance of adapted species to decrease seawater pH is limited, and new knowledge may be obtained from species inhabiting sites with naturally low pH, such as the volcanic CO2 system off the Castello Aragonese on the Ischia Island (Italy). Understanding the molecular mechanisms of adaptation enabling marine species to tolerate a lowered seawater pH could support predictions of the consequences of future OA scenarios for marine life. Growing evidence of the involvement of ABC transport proteins in resistance towards acid stress in bacteria and tumor cell lines has been demonstrated. Researchers have suggested that the tolerance to this kind of stress is due to the transport of substances that contribute to the maintenance of internal cell homeostasis carried out by the ABC proteins. Here, we aimed at elucidating the involvement of ABC transport proteins in tolerance to low-pH/high-pCO2 environments, by investigating their gene regulation, in species of marine microorganisms and metazoans considered tolerant to acidified environments. Halomicronema metazoicum is a marine filamentous cyanobacterium able to cope with hostile conditions and discovered in association with Posidonia oceanica leaves also in areas characterized by low pH. Mattes of this cyanobacterium were exposed in short- and long-term exposure experiments (7 and 30 d) to low seawater pH conditions (7.7, 7.2, 6.5), and the regulation of the ABC-like gene slr2019 was assessed. At day 7, slr2019 was up-regulated at pH 7.7 while no changes were observed at lower pH, compared to the controls (pH 8.2). However, after 30 d of exposure, a significant decrease in slr2019 transcript level was observed in all treatments. Furthermore, unchanged photosynthetic pigment content indicated that the species can tolerate all three lowered pH conditions. Platynereis dumerilii is a marine annelid extensively used as a model in genetics, single‐cell genomics, and ecotoxicology. It and its sibling, P. cfr massiliensis, were abundant in naturally acidified areas, such as the CO2 vents off Castello Aragonese. They are adapted to low-pH conditions, making them excellent models for studying acclimation and adaptation mechanisms to OA. Since its genome is completely sequenced, an attempt to identify ABC transport proteins in P. dumerilii has been made with the aim to investigate whether these proteins contribute to adaptation/tolerance to low-pH/high-pCO2 seawater conditions in the two sibling species P. dumerilii/cfr massiliensis before and after 30 d of in-situ transplant experiment. A total of 81 ABCs were found in P. dumerilii, belonging to seven distinct subfamilies (A–G) based on phylogenetic analysis. Furthermore, the distribution within the tissues of a subset of 40 ABC transport proteins from the subfamilies B, C and G was determined. Most of the analyzed ABCs were expressed in the annelid midgut but also found in the other organs and tissues: neurons, body epidermis and ectodermal cells, and somatic and visceral muscle. Based on these findings, we evaluated the expression profile of 7 genes belonging to the ABCB (ABCB_1, ABCB_2, ABCB_3), ABCC (ABCC_1, ABCC_2, ABCC_3) and ABCG (ABCG) subfamilies following a 30-d in-situ reciprocal transplant of specimens inhabiting normal-pH marine site (8.18 ± 0.005) and those living in naturally low-pH areas off Castello Aragonese (7.33 ± 0.312). Hypotheses on the involvement of each studied ABC gene in adaptation to low-pH were made based on the basal expression gene level of organisms inhabiting different pH environments and verified through the ABC transcription results of the in-situ transplant experiment. Three out of the 7 genes were confirmed to be involved in low-pH resistance. ABCB_1 and ABCG are up-regulated in worms living in low-pH sites compared to those from normal-pH areas while ABCB_3 were lower expressed. The results of transplant experiments supported these findings. ABCB_1 and ABCG gene expression increased in samples transplanted from normal-pH areas to acidified sites while decreased in the reverse transplant. On the contrary, ABCB_3 gene was down-regulated in organisms transferred from normal- to low-pH zones and was up-regulated in specimens subjected to the reverse transplantation. Taken together, our results demonstrate the capacity of the studied species to deal with low-pH environments and confirm previous findings on the involvement of ABC transporters in acid stress adaptation in marine organisms. These proteins were found to play a role in maintaining cellular homeostasis, buffering the internal cell pH and preventing cell death to guarantee the proper functioning of cellular activities. So, based on our findings, these functions may prevent negative effects following exposure to acidified conditions. This work will constitute a basis for further research on the physiological functions of ABCs behind the tolerance to low-pH/high-pCO2 environments to better understand how marine species can cope with OA and to provide vital information on the impact of climate change on marine biodiversity.
Continue reading ‘Molecular bases and evolutionary constraints of cellular acid tolerance in cyanobacteria and invertebrates subjected to ocean acidification and other sources of stress (METASTRESS)’Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm
Published 4 June 2024 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, mesocosms, otherprocess, photosynthesis, phytoplankton, prokaryotes, zooplankton
Highlights
- The communities were strongly affected by phytoplankton bloom stages.
- Ocean acidification (OA) affected some taxa as the phytoplankton bloom stages progressed.
- OA changed the co-occurrence network complexity and stability of microeukaryotes.
- OA altered the proportions of potential interactions between phytoplankton and their predators.
Abstract
Ocean acidification (OA) is known to influence biological and ecological processes, mainly focusing on its impacts on single species, but little has been documented on how OA may alter plankton community interactions. Here, we conducted a mesocosm experiment with ambient (∼410 ppmv) and high (1000 ppmv) CO2 concentrations in a subtropical eutrophic region of the East China Sea and examined the community dynamics of microeukaryotes, bacterioplankton and microeukaryote-attached bacteria in the enclosed coastal seawater. The OA treatment with elevated CO2 affected taxa as the phytoplankton bloom stages progressed, with a 72.89% decrease in relative abundance of the protist Cercozoa on day 10 and a 322% increase in relative abundance of Stramenopile dominated by diatoms, accompanied by a 29.54% decrease in relative abundance of attached Alphaproteobacteria on day 28. Our study revealed that protozoans with different prey preferences had differing sensitivity to high CO2, and attached bacteria were more significantly affected by high CO2 compared to bacterioplankton. Our findings indicate that high CO2 changed the co-occurrence network complexity and stability of microeukaryotes more than those of bacteria. Furthermore, high CO2 was found to alter the proportions of potential interactions between phytoplankton and their predators, as well as microeukaryotes and their attached bacteria in the networks. The changes in the relative abundances and interactions of microeukaryotes between their predators in response to high CO2 revealed in our study suggest that high CO2 may have profound impacts on marine food webs.
Continue reading ‘Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm’Decline of a distinct coral reef holobiont community under ocean acidification
Published 22 April 2024 Science ClosedTags: algae, annelids, biological response, BRcommunity, bryozoa, chemistry, cnidaria, corals, laboratory, molecular biology, physiology, porifera, prokaryotes, sediment, South Pacific
Background
Microbes play vital roles across coral reefs both in the environment and inside and upon macrobes (holobionts), where they support critical functions such as nutrition and immune system modulation. These roles highlight the potential ecosystem-level importance of microbes, yet most knowledge of microbial functions on reefs is derived from a small set of holobionts such as corals and sponges. Declining seawater pH — an important global coral reef stressor — can cause ecosystem-level change on coral reefs, providing an opportunity to study the role of microbes at this scale. We use an in situ experimental approach to test the hypothesis that under such ocean acidification (OA), known shifts among macrobe trophic and functional groups may drive a general ecosystem-level response extending across macrobes and microbes, leading to reduced distinctness between the benthic holobiont community microbiome and the environmental microbiome.
Results
We test this hypothesis using genetic and chemical data from benthic coral reef community holobionts sampled across a pH gradient from CO2 seeps in Papua New Guinea. We find support for our hypothesis; under OA, the microbiome and metabolome of the benthic holobiont community become less compositionally distinct from the sediment microbiome and metabolome, suggesting that benthic macrobe communities are colonised by environmental microbes to a higher degree under OA conditions. We also find a simplification and homogenisation of the benthic photosynthetic community, and an increased abundance of fleshy macroalgae, consistent with previously observed reef microbialisation.
Conclusions
We demonstrate a novel structural shift in coral reefs involving macrobes and microbes: that the microbiome of the benthic holobiont community becomes less distinct from the sediment microbiome under OA. Our findings suggest that microbialisation and the disruption of macrobe trophic networks are interwoven general responses to environmental stress, pointing towards a universal, undesirable, and measurable form of ecosystem change.
Continue reading ‘Decline of a distinct coral reef holobiont community under ocean acidification’Ocean acidification offsets the effect of warming on sediment denitrification and associated nitrous oxide production
Published 16 April 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, laboratory, otherprocess, prokaryotes, South Pacific
Rates of denitrification and associated nitrous oxide (N2O) production are expected to increase with global warming, leading to positive climate feedback. However, previous studies have not considered the combined effect of ocean acidification (OA, pCO2 ~ 900 µatm) and warming on denitrification rates and N2O production. Here we used a series of whole core incubation studies to assess the combined impact of warming and OA on estuarine sediment denitrification rates and N2O production. Strong warming (+5 °C over mean in situ conditions) increased N2O production by ~4.2 µmol-N m−2 d−1 and denitrification by ~43 µmol-N m−2 d−1, fuelled by water column nitrate (Dw), but decreased rates of nitrification-coupled denitrification in the sediment (Dn) by ~82 µmol-N m−2 d−1. While Dn was not affected by OA, Dw decreased significantly by 51 µmol-N m−2 d−1 when OA was coupled with warmer temperatures. We estimate that OA may offset the increase in estuarine sediment denitrification and N2O production expected from warming alone by up to 64% and reduce a potential positive climate feedback loop by inhibiting denitrification pathways.
Continue reading ‘Ocean acidification offsets the effect of warming on sediment denitrification and associated nitrous oxide production’Effects of CO2 on the nitrogen isotopic composition of Trichodesmium and Crocosphaera
Published 11 April 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, growth, laboratory, nitrogen fixation, physiology, prokaryotes
Biological nitrogen (N2) fixation is the main input of fixed nitrogen to ecosystems on Earth. Nitrogen isotope fractionation during this process is a key parameter for understanding the nitrogen cycle, however, relatively little is known about its regulatory mechanisms. Here we examine the effects of varying CO2 concentrations on biomass δ15N signatures of the cyanobacterial diazotrophs Trichodesmium erythraeum and Crocosphaera watsonii. We show that these organisms produce biomass up to ~3 ‰ lower in δ15N under either decreased (~180 µatm) or elevated (~1400 µatm) CO2 concentrations in comparison to modern levels (~380 µatm). Our results pointed towards changes in nitrogenase enzyme efficiency in response to CO2 perturbations impacting isotopic fractionation during N2 fixation and thus the biomass δ15N. This study contributes to an improved interpretation of the observed fluctuations in the δ15N records, and thus the past nitrogen cycle on Earth.
Continue reading ‘Effects of CO2 on the nitrogen isotopic composition of Trichodesmium and Crocosphaera’The prokaryotic and eukaryotic microbiome of Pacific oyster spat is shaped by ocean warming but not acidification
Published 28 March 2024 Science ClosedTags: biological response, mollusks, multiple factors, prokaryotes, socio-economy, temperature
Pacific oysters (Magallana gigas, a.k.a. Crassostrea gigas), the most widely farmed oysters, are under threat from climate change and emerging pathogens. In part, their resilience may be affected by their microbiome, which, in turn, may be influenced by ocean warming and acidification. To understand these impacts, we exposed early-development Pacific oyster spat to different temperatures (18°C and 24°C) and pCO2 levels (800, 1,600, and 2,800 µatm) in a fully crossed design for 3 weeks. Under all conditions, the microbiome changed over time, with a large decrease in the relative abundance of potentially pathogenic ciliates (Uronema marinum) in all treatments with time. The microbiome composition differed significantly with temperature, but not acidification, indicating that Pacific oyster spat microbiomes can be altered by ocean warming but is resilient to ocean acidification in our experiments. Microbial taxa differed in relative abundance with temperature, implying different adaptive strategies and ecological specializations among microorganisms. Additionally, a small proportion (~0.2% of the total taxa) of the relatively abundant microbial taxa were core constituents (>50% occurrence among samples) across different temperatures, pCO2 levels, or time. Some taxa, including A4b bacteria and members of the family Saprospiraceae in the phyla Chloroflexi (syn. Chloroflexota) and Bacteroidetes (syn. Bacteroidota), respectively, as well as protists in the genera Labyrinthula and Aplanochytrium in the class Labyrinthulomycetes, and Pseudoperkinsus tapetis in the class Ichthyosporea were core constituents across temperatures, pCO2 levels, and time, suggesting that they play an important, albeit unknown, role in maintaining the structural and functional stability of the Pacific oyster spat microbiome in response to ocean warming and acidification. These findings highlight the flexibility of the spat microbiome to environmental changes.
Continue reading ‘The prokaryotic and eukaryotic microbiome of Pacific oyster spat is shaped by ocean warming but not acidification’Adverse environmental perturbations may threaten kelp farming sustainability by exacerbating enterobacterales diseases
Published 25 March 2024 Science ClosedTags: algae, biological response, community composition, field, laboratory, light, molecular biology, morphology, mortality, multiple factors, North Pacific, otherprocess, physiology, prokaryotes, protists, reproduction
Globally kelp farming is gaining attention to mitigate land-use pressures and achieve carbon neutrality. However, the influence of environmental perturbations on kelp farming remains largely unknown. Recently, a severe disease outbreak caused extensive kelp mortality in Sanggou Bay, China, one of the world’s largest high-density kelp farming areas. Here, through in situ investigations and simulation experiments, we find indications that an anomalously dramatic increase in elevated coastal seawater light penetration may have contributed to dysbiosis in the kelp Saccharina japonica’s microbiome. This dysbiosis promoted the proliferation of opportunistic pathogenic Enterobacterales, mainly including the genera Colwellia and Pseudoalteromonas. Using transcriptomic analyses, we revealed that high-light conditions likely induced oxidative stress in kelp, potentially facilitating opportunistic bacterial Enterobacterales attack that activates a terrestrial plant-like pattern recognition receptor system in kelp. Furthermore, we uncover crucial genotypic determinants of Enterobacterales dominance and pathogenicity within kelp tissue, including pathogen-associated molecular patterns, potential membrane-damaging toxins, and alginate and mannitol lysis capability. Finally, through analysis of kelp-associated microbiome data sets under the influence of ocean warming and acidification, we conclude that such Enterobacterales favoring microbiome shifts are likely to become more prevalent in future environmental conditions. Our study highlights the need for understanding complex environmental influences on kelp health and associated microbiomes for the sustainable development of seaweed farming.
Continue reading ‘Adverse environmental perturbations may threaten kelp farming sustainability by exacerbating enterobacterales diseases’Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents
Published 22 March 2024 Science ClosedTags: adaptation, biogeochemistry, biological response, laboratory, Mediterranean, molecular biology, nitrogen fixation, otherprocess, phanerogams, physiology, prokaryotes, protists, vents
Seagrass meadows form highly productive and diverse ecosystems in coastal areas worldwide, where they are increasingly exposed to ocean acidification (OA). Efficient nitrogen (N) cycling and uptake are essential to maintain plant productivity, but the effects of OA on N transformations in these systems are poorly understood. Here we show that complete N cycling occurs on leaves of the Mediterranean seagrass Posidonia oceanica at a volcanic CO2 vent near Ischia Island (Italy), with OA affecting both N gain and loss while the epiphytic microbial community structure remains largely unaffected. Daily leaf-associated N2 fixation contributes to 35% of the plant’s N demand under ambient pH, while it contributes to 45% under OA. Nitrification potential is only detected under OA, and N-loss via N2 production increases, although the balance remains decisively in favor of enhanced N gain. Our work highlights the role of the N-cycling microbiome in seagrass adaptation to OA, with key N transformations accelerating towards increased N gain.
Continue reading ‘Accelerated nitrogen cycling on Mediterranean seagrass leaves at volcanic CO2 vents’
