Seagrass meadows play vital ecological roles in the marine ecosystem. Global climate change poses considerable threats to seagrass survival. However, it is unclear how seagrass and its associated bacteria will respond under future complex climate change scenarios. This study explored the effects of ocean warming (+2 °C) and ocean acidification (−0.4 units) on seagrass physiological indexes and bacterial communities (sediment and rhizosphere bacteria) of the seagrass Thalassia hemprichii during an experimental exposure of 30 days. Results demonstrated that the synergistic effect of ocean warming and ocean acidification differed from that of one single factor on seagrass and the associated bacterial community. The seagrass showed a weak resistance to ocean warming and ocean acidification, which manifested through the increase in the activity of typical oxidoreductase enzymes. Moreover, the synergistic effect of ocean warming and ocean acidification caused a significant decrease in seagrass’s chlorophyll content. Although the bacterial community diversity exhibited higher resistance to ocean warming and ocean acidification, further bacterial functional analysis revealed the synergistic effect of ocean warming and ocean acidification led to significant increases in SOX-related genes abundance which potentially supported the seagrass in resisting climate stress by producing sulfates and oxidizing hydrogen sulfide. More stable bacterial communities were detected in the seagrass rhizosphere under combined ocean warming and ocean acidification. While for one single environmental stress, simpler networks were detected in the rhizosphere. In addition, the observed significant correlations between several modules of the bacterial community and the physiological indexes of the seagrass indicate the possible intimate interaction between seagrass and bacteria under ocean warming and ocean acidification. This study extends our understanding regarding the role of seagrass associated bacterial communities and sheds light on both the prediction and preservation of the seagrass meadow ecosystems in response to global climate change.
Continue reading ‘Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification’Posts Tagged 'community composition'
Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification
Published 21 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, physiology, prokaryotes, temperature
Benthic foraminiferal response to the Aptian−Albian carbon cycle perturbation in the Atlantic Ocean
Published 13 July 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, North Atlantic, otherprocess, paleo, protists, South Atlantic
A planktic foraminiferal mass extinction, coeval with the major carbon cycle perturbation of Oceanic Anoxic Event (OAE) 1b, occurred at the Aptian−Albian boundary interval (AABI). However, the scarcity of high-resolution records across the AABI hampers an assessment of the impacts of OAE 1b on deep-water benthic foraminiferal assemblages. Here we present high-resolution benthic foraminiferal census counts at Deep Sea Drilling Project (DSDP) Site 511 (southern South Atlantic Ocean) and Ocean Drilling Program (ODP) Site 1049 (western subtropical North Atlantic Ocean) over the AABI. Our records at these bathyal sites provide conclusive evidence that there was no benthic foraminiferal extinction at the Aptian−Albian boundary, although marked reorganizations of relative abundances occurred. During the latest Aptian, cyclic increases in the abundance of infaunal species at both sites point to repeated pulses of reduced bottom water oxygenation and increased organic carbon flux to the ocean floor. Additionally, agglutinated and weakly calcified benthic foraminiferal species were relatively abundant during the latest Aptian, suggesting deep-water carbonate ion depletion in the Atlantic Ocean, although we did not identify signs of carbonate dissolution at these relatively shallow sites. At Site 511, abundances of infaunal foraminifera increased in tandem with the negative carbonate carbon isotope (δ13Ccarb) excursion of the Kilian sub-event within OAE 1b, suggesting decreased bottom water ventilation and increased organic carbon flux to the ocean floor during the sub-event. Bottom water ventilation and carbonate ion saturation improved during the earliest Albian in the Atlantic Ocean, followed by high-amplitude oscillations, as suggested by abundance trends of heavily calcified epifaunal foraminifera at Sites 511 and 1049.
Continue reading ‘Benthic foraminiferal response to the Aptian−Albian carbon cycle perturbation in the Atlantic Ocean’Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments
Published 12 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, phytoplankton, prokaryotes, temperature
Understanding the long-term response of key marine phytoplankton species to ongoing global changes is pivotal in determining how oceanic community composition will respond over the coming decades. To better understand the impact of ocean acidification and warming, we acclimated two strains of Skeletonema marinoi isolated from natural communities to three pCO2 (400 atm, 600 atm and 1000 atm) for 8 months and five temperature conditions (7°C, 10°C, 13°C, 16°C and 19°C) for 11 months. These strains were then tested in natural microbial communities, exposed to three pCO2 treatments (400 atm, 600 atm and 1000 atm). DNA metabarcoding of the 16S and 18S gene for prokaryotes and eukaryotes respectively was used to show differences in abundance and diversity between the three CO2 treatments. We found there were no significant differences in acclimated S. marinoi concentrations between the three pCO2 treatments, most likely due to the high variability these strains experience in their natural environment. There were significant compositional differences between the pCO2 treatments for prokaryotes suggesting that indirect changes to phytoplankton-bacteria interactions could be a possible driver of bacterial community composition. Yet, there were no differences for eukaryotic community composition, with all treatments dominated by diatoms (but not the acclimated S. marinoi) resulting in similar biodiversity. Furthermore, strain-specific differences in community composition suggests interactions between prokaryotic and eukaryotic taxa could play a role in determining future community composition.
Continue reading ‘Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments’Ocean acidification altered microbial functional potential in the Arctic Ocean
Published 30 June 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, mesocosms, molecular biology, otherprocess, physiology, prokaryotes
Ocean acidification (OA) has considerably changed the metabolism and structure of plankton communities in the ocean. Evaluation of the response of the marine bacterioplankton community to OA is critical for understanding the future direction of bacterioplankton-mediated biogeochemical processes in the ocean. Understanding the diversity of functional genes is important for linking the microbial community to ecological and biogeochemical processes. However, the influence of OA on the functional diversity of bacterioplankton remains unclear. Using high-throughput functional gene microarray technology (GeoChip 4), we investigated the functional gene structure and diversity of bacterioplankton under three different pCO2 levels (control: 175 μatm, medium: 675 μatm, and high: 1085 μatm) in a large Arctic Ocean mesocosm experiment. We observed a higher evenness of microbial functional genes under elevated pCO2 compared with under low pCO2. OA induced a more stable community as evaluated by decreased dissimilarity of functional gene structure with increased pCO2. Molecular ecological networks under elevated pCO2 became more complex and stable, supporting the central ecological tenet that complexity begets stability. In particular, increased average abundances were found under elevated pCO2 for many genes involved in key metabolic processes, including carbon degradation, methane oxidization, nitrogen fixation, dissimilatory nitrite/nitrate reduction, and sulfide reduction processes. Altogether, these results indicate a significant influence of OA on the metabolism potential of bacterioplankton in the Arctic Ocean. Consequently, our study suggests that biogeochemical cycling mediated by these microbes may be altered by the OA in the future.
Continue reading ‘Ocean acidification altered microbial functional potential in the Arctic Ocean’Microbial dynamics in shallow CO2 seeps system off Panarea Island (Italy)
Published 30 June 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, Mediterranean, otherprocess, physiology, prokaryotes, vents
Shallow-water hydrothermal vents are extreme environments characterized by high temperatures, low pH, and high CO2 concentrations; therefore, they are considered as suitable laboratories for studying the effect of global changes on marine microbes. We hypothesized a direct effect of vents on prokaryotic community structure and functioning in the Panarea Island’s hydrothermal system. Sampling was conducted along a 9-station transect characterized by three active emission points. The water column was stratified with a thermocline at 25 m depth and a deep chlorophyll maximum between 50 and 100 m. Prokaryotic abundance ranged from 0.2 to 1.5 × 109 cells L−1, prokaryotic carbon production from 2.4 to 75.4 ng C L−1 h−1, and exoenzymatic activities degrading proteins, phosphorylated compounds, and polysaccharides were on the order of 4–28, 2–31 and 0.2–4.16 nM h−1, respectively. While microbial abundance and production were shaped by the water column’s physical structure, alkaline phosphatase and beta-glucosidase activities seemed to be enhanced by hydrothermal fluids. The 16S rRNA gene amplicon sequencing analysis identified a surface, a deep, and a vent-influenced microbial community. In terms of relative abundance members of the SAR11 group dominated the water column, alongside Synechococcus and Prochlorococcus in surface and bottom samples, respectively. Vent-influenced stations were characterized by the presence of Thiomicrorhabdus, a sulfur-oxidizer chemolithoautotroph. Overall, this study provides insights on the coupling between microbial community structure and the biogeochemical cycling of nutrients in low-pH conditions (CO2 and H2S-based), thus addressing some of the opened questions about the response of microbes to acidification.
Continue reading ‘Microbial dynamics in shallow CO2 seeps system off Panarea Island (Italy)’Planktic foraminiferal resilience to environmental change associated with the PETM
Published 28 June 2023 Science ClosedTags: abundance, Arctic, biological response, chemistry, community composition, communitymodeling, modeling, North Pacific, otherprocess, paleo, protists, South Pacific
Carbonate-forming organisms play an integral role in the marine inorganic carbon cycle, yet the links 21 between carbonate production and the environment are insufficiently understood. Carbonate production is driven by the abundance of calcifiers, and the amount of calcite produced by each individual (their size and weight). Here we investigate how foraminiferal carbonate production changes in the Atlantic, Pacific and Southern Ocean in response to a 4-5°C warming and a 0.3 surface ocean pH reduction during the Palaeocene-Eocene Thermal Maximum (PETM). To put these local data into a global context, we apply a trait-based plankton model (ForamEcoGEnIE) to the geologic record for the first time. Our data illustrates negligible change in the assemblage test size and abundance of foraminifers. ForamEcoGEnIE resolves small reductions in size and biomass, but these are short-lived. The response of foraminifersshowsspatial variability linked to a warming-induced poleward migration and suggested differences in nutrient availability between open-ocean and shelf locations. Despite low calcite saturation at high latitudes, we reconstruct stable foraminiferal size-normalised weight. Based on these findings, we postulate that sea surface warming had a greater impact on foraminiferal carbonate production during the PETM than ocean acidification. Changes in the composition of bulk carbonate suggest a higher sensitivity of coccolithophores to environmental change during the PETM than foraminifers.
Continue reading ‘Planktic foraminiferal resilience to environmental change associated with the PETM’A glimpse into the climate, seasonality, hydrological cycle, carbonate chemistry and marine ecosystem shift of the pre-Petm and the Petm using Ncar Cesm1.2
Published 22 June 2023 Science ClosedTags: biological response, BRcommunity, chemistry, community composition, modeling, North Atlantic, paleo, phytoplankton, regionalmodeling, South Atlantic
The Paleocene-Eocene Thermal Maximum (PETM, ~56 my ago, 170,000y event) is characterized by a negative δ13C excursion into the atmosphere. This event caused global temperature to increase by about 5-6 °C, followed by climate responses such as marine acidification, ocean stratification, shoaling of calcite compensation depth (CCD), stronger hydrological cycle, and significant changes in marine ecosystems. It is one of the very few analogies of today’s global warming climate and thus is valuable to study. It still holds much potential for research, including using the state-of-the-art model CESM1.2. Proxy records are limited due to the nature of geological preservation and tectonic evolution. Modeling and simulations can provide insights to supplement the limited proxy records research. Here, we explore the seasonality, hydrological cycles, and controlling factors of their changes from pre-PETM to the PETM in the first paper; the ability of CESM1.2 to simulate carbonate chemistry, changes in lysocline and CCD in the Atlantic Ocean in the second paper; and the shift of phytoplankton functional groups, using the same preferendum to capture first-hand reactions to environmental changes, from pre-industrial pCO2 to pre-PETM in the third paper. All papers use CESM1.2 simulation results with or without BEC. Our results show that from pre-PETM to PETM, seasonality increases in mid-latitude continental interiors and decreases in high and low latitudes, along with globally enhanced moisture transfer in hydrological cycles. The main controlling factors of these areas are snow-albedo effect, soil moisture, and precipitation. CESM1.2 and ocean Biogeochemical (BGC) Elemental Cycling (BEC) can simulate the changes of carbonate chemistry of the Atlantic Ocean, with certain modifications in the code base and without the need of extra models. There are noticeable and significant changes in chlorophyll, nutrient and NPP from PETM in pre-industrial pCO2 and pre-PETM, but distinct variations from pre-industrial and PETM in pre-industrial pCO2 simulations. Proxy record scarcity is the main limitation of the studies on PETM and should be used with care. In the meantime, machine learning is encouraged for multi-disciplinary research of complicated topics such as carbon chemistry and phytoplankton functional group preferendum and ecosystem dynamics.
Continue reading ‘A glimpse into the climate, seasonality, hydrological cycle, carbonate chemistry and marine ecosystem shift of the pre-Petm and the Petm using Ncar Cesm1.2’Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification in the East Sea of Korea
Published 19 June 2023 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, community composition, crustaceans, field, nematodes, North Pacific, otherprocess, protists, zooplankton
This study aimed to investigate the meiofauna community characteristics in coastal waters highly affected by ocean acidification. Therefore, the meiofauna communities in the coastal waters of Hupo in Uljin-gun, a county bordering the East Sea of Korea, were monitored over five years. During the study period, the mean abundance of total meiofauna communities expressed in population density was 614.4 individuals (Inds.)/10 cm2, similar to the reported meiofauna abundance in the subtidal zone in the Yellow Sea of Korea, an area with sandy sedimentary facies. The most dominant taxa were nematodes (65–70%) and harpacticoids (7–20%); these two taxa accounted for approximately 80% of the total meiofauna abundance. Among the stations studied, station (St.) 10 showed the lowest seawater pH value, and in 2011, when the measured pH was the lowest at 7.82, St. 10 showed the lowest abundance values for total meiofauna and harpacticoids in the 5-year period. To examine the effect of ocean acidification on meiofauna communities at the species level, species of nematodes, the most dominant taxon, were analyzed. The results indicated that the number of nematode species at St. 10 in 2009, when the pH value was low, was 8, which was very low compared to that in the other years of the study period. According to the feeding type, epistrate feeders (2A) accounted for a remarkably high proportion at St. 10, which showed a low pH. This study provides various data on meiobenthic community characteristics to understand the effects of ocean acidification on coastal ecosystems.
Continue reading ‘Characteristics of meiofaunal community in the subtidal zone near Hupo, anticipating ocean acidification in the East Sea of Korea’Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis
Published 16 June 2023 Science ClosedTags: abundance, archaea, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, physiology, porifera, prokaryotes, South Pacific, temperature
Oceans are rapidly warming and acidifying in the context of climate change, threatening sensitive marine biota including coral reef sponges. Ocean warming (OW) and ocean acidification (OA) can impact host health and associated microbiome, but few studies have investigated these effects, which are generally studied in isolation, on a specific component of the holobiont. Here we present a comprehensive view of the consequences of simultaneous OW and OA for the tropical sponge Stylissa flabelliformis. We found no interactive effect on the host health or microbiome. Furthermore, OA (pH 7.6 versus pH 8.0) had no impact, while OW (31.5 °C versus 28.5 °C) caused tissue necrosis, as well as dysbiosis and shifts in microbial functions in healthy tissue of necrotic sponges. Major taxonomic shifts included a complete loss of archaea, reduced proportions of Gammaproteobacteria and elevated relative abundances of Alphaproteobacteria. OW weakened sponge-microbe interactions, with a reduced capacity for nutrient exchange and phagocytosis evasion, indicating lower representations of stable symbionts. The potential for microbially-driven nitrogen and sulphur cycling was reduced, as was amino acid metabolism. Crucially, the dysbiosis annihilated the potential for ammonia detoxification, possibly leading to accumulation of toxic ammonia, nutrient imbalance, and host tissue necrosis. Putative defence against reactive oxygen species was greater at 31.5 °C, perhaps as microorganisms capable of resisting temperature-driven oxidative stress were favoured. We conclude that healthy symbiosis in S. flabelliformis is unlikely to be disrupted by future OA but will be deeply impacted by temperatures predicted for 2100 under a “business-as-usual” carbon emission scenario.
Continue reading ‘Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis’Variations in the Southern Ocean carbonate production, preservation, and hydrography for the past 41, 500 years: evidence from coccolith and CaCO3 records
Published 15 June 2023 Science ClosedTags: abundance, Antarctic, BRcommunity, community composition, Indian, otherprocess, paleo, phytoplankton, sediment
Changes in ocean alkalinity affect atmospheric pCO2 (i.e., higher alkalinity lowers atmospheric pCO2). Ocean alkalinity is partly determined by sedimentary burial of carbonates, which is primarily controlled by carbonate flux and the degree of deep ocean carbonate saturation. In this study, we investigate the factors determining the coccolith burial in subantarctic sediments and the surface ocean changes in the subtropical South Indian Ocean. The downcore coccolith records from the subantarctic region (SK200/22a) of the Indian sector of the Southern Ocean display low coccolith concentration during the glacial period. A possible explanation for this is, 1) the low glacial production of coccolithophores due to the competition from diatoms and 2) dilution by biogenic silica in the glacial sediments. Additionally, reduced carbonate burial owing to the low carbonate saturation of the deep-water accounts for the decline in glacial coccolith concentration. This also explains the low coccolith dissolution index and enrichment of the large dissolution-resistant coccolith species, Coccolithus pelagicus subsp. braarudii in the glacial sediments. The low carbonate saturation is attributed to, 1) the replacement of carbonate saturated, North Atlantic Deep Waters by the undersaturated southern sourced water masses and 2) increased storage of dissolved CO2 in the deep glacial Southern Ocean. Our study suggests that changes in coccolith production and the deep ocean carbonate saturation determine their burial in subantarctic sediments for the last 41,500 years. Other than these changes, the study region also records the changes in the Agulhas Return Current via variation in the proportion of tropical-subtropical coccolith assemblage.
Continue reading ‘Variations in the Southern Ocean carbonate production, preservation, and hydrography for the past 41, 500 years: evidence from coccolith and CaCO3 records’The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts
Published 14 June 2023 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, primary production, prokaryotes, temperature
Reef-building corals, the foundation of tropical coral reefs, are vulnerable to climate change e.g. ocean acidification and elevated seawater temperature. Coral microbiome plays a key role in host acclimatization and maintenance of the coral holobiont’s homeostasis under different environmental conditions, however, the response patterns of coral prokaryotic symbionts to ocean acidification and/or warming are rarely known at the metatranscriptional level, particularly the knowledge of interactive and persistent effects is limited. Using branching Acropora valida and massive Galaxea fascicularis as models in a lab system simulating extreme ocean acidification (pH 7.7) and/or warming (32 °C) in the future, we investigated the changes of in situ active prokaryotic symbionts community and gene expression of corals under/after (6/9 d) acidification (A), warming (H) and acidification–warming (AH) by metatranscriptome analysis with pH8.1, 26 °C as the control.
Continue reading ‘The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts’Interaction matters: bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change
Published 9 June 2023 Science ClosedTags: abundance, biological response, community composition, communitymodeling, globalmodeling, light, modeling, multiple factors, otherprocess, phytoplankton, regionalmodeling, temperature
Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple-driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual-driver interactions (CO2 and temperature, CO2 and light), based on data of a published meta-analysis on multiple-driver laboratory experiments. The effect of this parametrization on phytoplankton biomass and community composition is tested using present-day and future high-emission (SSP5-8.5) climate forcing. While the projected decrease in future total global phytoplankton biomass in simulations with driver interactions is similar to that in control simulations without driver interactions (5%–6%), interactive driver effects are group-specific. Globally, diatom biomass decreases more with interactive effects compared with the control simulation (−8.1% with interactions vs. no change without interactions). Small-phytoplankton biomass, by contrast, decreases less with on-going climate change when the model accounts for driver interactions (−5.0% vs. −9.0%). The response of global coccolithophore biomass to future climate conditions is even reversed when interactions are considered (+33.2% instead of −10.8%). Regionally, the largest difference in the future phytoplankton community composition between the simulations with and without driver interactions is detected in the Southern Ocean, where diatom biomass decreases (−7.5%) instead of increases (+14.5%), raising the share of small phytoplankton and coccolithophores of total phytoplankton biomass. Hence, interactive effects impact the phytoplankton community structure and related biogeochemical fluxes in a future ocean. Our approach is a first step to integrate the mechanistic understanding of interacting driver effects on phytoplankton growth gained by numerous laboratory experiments into a global ocean biogeochemistry model, aiming toward more realistic future projections of phytoplankton biomass and community composition.
Continue reading ‘Interaction matters: bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change’Risk assessment of a coastal ecosystem from SW Spain exposed to CO2 enrichment conditions
Published 8 June 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, crustaceans, echinoderms, laboratory, mesocosms, mollusks, morphology, mortality, North Atlantic, otherprocess, physiology, sediment
The Weight-of-Evidence (WOE) approach uses multiple lines of evidence to analyze the adverse effects associated with CO2 enrichment in two stations from the Gulf of Cádiz (Spain) with different contamination degrees. Sediment contamination and metal (loid) mobility, toxicity, ecological integrity, and bioaccumulation from the samples exposed to different acidification scenarios (pH gradient from 8.0 to 6.0) were used in the WOE. The experiments were conducted under laboratory conditions using a CO2-bubbling system. Different integration approaches such as multivariate analyses were used to evaluate the results. The results indicated that the adverse biological effects under pH 6.5 were related to the mobility of dissolved elements (As, Fe, Cu, Ni, and Zn). Furthermore, the pH reduction was correlated to the increase of bioaccumulation of As, Cr, Cu, Fe, and Ni in the tissues of mussels at pH 7.0. The noncontaminated sediment showed environmental degradation related to the acidification at pH values of 7.0; whereas the sediment moderately contaminated showed both environmental risks, caused by acidification and the presence and the increase of the bioavailability of contaminants. The WOE approach supposes an effective tool to identify and distinguish the causes of adverse effects related to the enrichment of CO2 in marine environments.
Continue reading ‘Risk assessment of a coastal ecosystem from SW Spain exposed to CO2 enrichment conditions’Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study
Published 7 June 2023 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, laboratory, mesocosms, methods, multiple factors, otherprocess, performance, physiology, prokaryotes, temperature
Marine environments are expected to be one of the most affected ecosystems by climate change, notably with increasing ocean temperature and ocean acidification. In marine environments, microbial communities provide important ecosystem services ensuring biogeochemical cycles. They are threatened by the modification of environmental parameters induced by climate change that, in turn, affect their activities. Microbial mats, ensuring important ecosystem services in coastal areas, are well-organized communities of diverse microorganisms representing accurate microbial models. It is hypothesized that their microbial diversity and metabolic versatility will reveal various adaptation strategies in response to climate change. Thus, understanding how climate change affects microbial mats will provide valuable information on microbial behaviour and functioning in changed environment. Experimental ecology, based on mesocosm approaches, provides the opportunity to control physical-chemical parameters, as close as possible to those observed in the environment. The exposure of microbial mats to physical-chemical conditions mimicking the climate change predictions will help to decipher the modification of the microbial community structure and function in response to it. Here, we present how to expose microbial mats, following a mesocosm approach, to study the impact of climate change on microbial community.
Continue reading ‘Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study’Explosive volcanism periodicity past cycles record within the last 0.8 Mya evidenced by tephra and benthic foraminifera of IODP Hole U1485AA (Exp. 363 WPWP)
Published 5 June 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, field, otherprocess, paleo, protists, sediment, South Pacific
Volcanic eruptions with increase in the amount of carbon dioxide (CO2) and other gases are responsible for the extinction of many species because of decreased pH and carbonate availability which creates ocean acidification. Here we show how benthic foraminifera have evolved, by studying sediments from U1485A (1145 m water depth) core in the Papua New Guinea (PNG) collected during IODP Expedition 363 in the Western Pacific Warm Pool (WPWP), one of the warmest marine waters of the world. High-stressed environments dominated by low diversity of opportunistic species after volcanic activity was detected by the presence of tephra and volcanic ashes within the last 0.8 Mya. The decrease in the diversity patterns show an inverse correlation to the presence of tephra and ash right after Pleistocene volcanic eruptions in the past. Deep-water fauna is dominated by Cibicidoides pachiderma, from the early Oligocene through the Pleistocene, Uvigerina hispida from early Miocene through Pleistocene, U. prosbocidae from late Oligocene through Pleistocene, and an outer neritic upper bathyal Uvigerina mediterranea from high salinities, warm waters, low dissolved oxygen, and high organic matter. Bolivinita quadrilatera characteristic of 200-500m depth, Bolivina robusta from 3 to 900m, and the Rotalinoides compressiusculus, a shallow warm water species, from 2-37m depth show higher diversity peaks in interglacial cycles. High-stress conditions with mass extinction after volcanic eruptions leads to enhanced weathering, global warming and cooling afterwards, and ocean acidification, resulting in a crisis in the marine environment in terms of carbonate. Diversity gradients suggested that foraminiferal species responded to the cyclic pulses of volcanic eruptions, and its unstable ecological conditions created by the increase in the temperature and CO2. Here we show that tephra layers and ash record a periodicity of explosive volcanism within the last 0.8 Myr maintaining a strong 100 kyr periodicity, and that earth’s orbital cycles might trigger peaks of volcanic eruptions 41,000-year cycle.
Continue reading ‘Explosive volcanism periodicity past cycles record within the last 0.8 Mya evidenced by tephra and benthic foraminifera of IODP Hole U1485AA (Exp. 363 WPWP)’Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves
Published 5 June 2023 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, cnidaria, community composition, crustaceans, echinoderms, Indian, mollusks, otherprocess, phanerogams, phytoplankton, primary production, review, socio-economy
Highlights
- Overfishing and climate change show potential effects on MMI ES.
- MMI regulating ES can be quantified using species richness and functional traits.
- Digital platforms are valuable tools to retrieve data but have limitations.
- Baseline data and information on environmental changes and MMI ES is provided.
Abstract
This study aimed to investigate the impact of changing environmental conditions on MMI ES in seagrasses and mangroves. We used data from satellite and biodiversity platforms combined with field data to explore the links between ecosystem pressures (habitat conversion, overexploitation, climate change), conditions (environmental quality, ecosystem attributes), and MMI ES (provisioning, regulation, cultural). Both seagrass and mangrove extents increased significantly since 2016. While sea surface temperature showed no significant annual variation, sea surface partial pressure CO2, height above sea level and pH presented significant changes. Among the environmental quality variables only silicate, PO4 and phytoplankton showed significant annual varying trends. The MMI food provisioning increased significantly, indicating overexploitation that needs urgent attention. MMI regulation and cultural ES did not show significant trends overtime. Our results show that MMI ES are affected by multiple factors and their interactions can be complex and non-linear. We identified key research gaps and suggested future directions for research. We also provided relevant data that can support future ES assessments.
Continue reading ‘Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves’Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico
Published 26 May 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, dissolution, laboratory, morphology, North Pacific, otherprocess, protists, sediment
Ocean acidification is expected to negatively affect many ecologically important organisms. Here we explored the response of Caribbean benthic foraminiferal assemblages to naturally discharging low-pH waters similar to expected future projections for the end of the 21st century. At low pH (~7.7 pH units) and low calcite saturation, agglutinated and symbiont-bearing species were relatively more abundant, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics declined steeply with decreasing pH, despite exposure of this ecosystem for millennia to low pH conditions, suggesting that tropical foraminifera communities will be negatively impacted under acidification scenarios SSP3-7.0 and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean, was able to calcify at conditions more extreme than those projected for the late 21st century (7.1 pH units), but the calcified tests were of lower density than those exposed to higher-pH ambient conditions (7.96 pH units), indicating that reef foraminiferal carbonate budget might decrease. Smaller foraminifera were highly sensitive to decreasing pH and our results demonstrate their potential as indicators to monitor increasing OA conditions.
Continue reading ‘Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico’Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont
Published 26 May 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, otherprocess, oxygen, physiology, prokaryotes
Introduction:
Reef building oysters provide vast ecological benefits and ecosystem services. A large part of their role in driving ecological processes is mediated by the microbial communities that are associated with the oysters; together forming the oyster holobiont. While changing environmental conditions are known to alter the physiological performance of oysters, it is unclear how multiple stressors may alter the ability of the oyster holobiont to maintain its functional role.
Methods:
Here, we exposed oysters to acidification and hypoxia to examine their physiological responses (molecular defense and immune response), changes in community structure of their associated microbial community, and changes in water nutrient concentrations to evaluate how acidification and hypoxia will alter the oyster holobiont’s ecological role.
Results:
We found clear physiological stress in oysters exposed to acidification, hypoxia, and their combination but low mortality. However, there were different physiological trade-offs in oysters exposed to acidification or hypoxia, and the combination of stressors incited greater physiological costs (i.e., >600% increase in protein damage and drastic decrease in haemocyte counts). The microbial communities differed depending on the environment, with microbial community structure partly readjusted based on the environmental conditions. Microbes also seemed to have lost some capacity in nutrient cycling under hypoxia and multi-stressor conditions (~50% less nitrification) but not acidification.
Discussion:
We show that the microbiota associated to the oyster can be enriched differently under climate change depending on the type of environmental change that the oyster holobiont is exposed to. In addition, it may be the primary impacts to oyster physiology which then drives changes to the associated microbial community. Therefore, we suggest the oyster holobiont may lose some of its nutrient cycling properties under hypoxia and multi-stressor conditions although the oysters can regulate their physiological processes to maintain homeostasis on the short-term.
Continue reading ‘Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont’Contrasting life cycles of Southern Ocean pteropods alter their vulnerability to climate change
Published 16 May 2023 Science ClosedTags: abundance, Antarctic, biological response, chemistry, community composition, field, mollusks, morphology, otherprocess, physiology, reproduction, zooplankton
Pteropods are a key part of biogeochemical cycling and epipelagic food webs in the Southern Ocean. However, shelled pteropods are vulnerable to climate change, due to their aragonite shells being particularly sensitive to ocean acidification. Currently our understanding of pteropod responses to environmental change is hindered by uncertainties surrounding their life cycles and population dynamics. In this study, we describe polar shelled pteropod diversity in the north-eastern Scotia Sea, inferring life history and population structures of the dominant pteropod species, Limacina rangii (formerly Limacina helicina antarctica) and Limacina retroversa. An annual timeseries of Limacina shell morphometrics was derived from individuals collected in a moored sediment trap at 400 m depth. We found that L. rangii and L. retroversa have contrasting life history strategies. L. rangii has a continuous spawning and recruitment period from November to March and can overwinter as juveniles and adults. L. retroversa has discrete spawning events from November to May, producing non–overlapping cohorts of juveniles and adults. Their development to the adult stage takes between two and five months, upon which they overwinter as adults. Our findings suggest different vulnerabilities of L. rangii and L. retroversa to a changing ocean. For example, since all life stages of L. rangii co-exist, vulnerability of one cohort is not detrimental to the stability of the overall population whereas, if one L. retroversa cohort fails to recruit, the entire population is threatened. Changes in pteropod populations could have cascading ramifications to Antarctic ecosystems and carbon cycling.
Continue reading ‘Contrasting life cycles of Southern Ocean pteropods alter their vulnerability to climate change’Responses of biogenic dimethylated sulfur compounds to environmental changes in the northwestern Pacific continental sea
Published 11 May 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, North Pacific, nutrients, otherprocess, phytoplankton, prokaryotes
Continental seas are facing rapid environmental shifts, but how biogenic dimethylated sulfur compounds, including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), will respond to these environmental changes remains poorly understood. Here we investigated the effects of nutrient input, ocean acidification, and dust deposition on the phytoplankton community and organic sulfur cycle in the East China Sea. Nutrient input promoted phytoplankton growth and increased the concentrations of DMS, DMSP, and DMSO. With sufficient nutrients, especially nitrate, the dissolved DMSP degradation was inhibited, and the bacterial DMSP-cleavage pathway (inferred by dddP gene abundance) was enhanced, causing increased DMS production. The sensitivity of phytoplankton biomass and DMS to ocean acidification varied with different initial nutrient levels, demonstrating insensitivity under eutrophic conditions and negative responses under nutrient-limited conditions. The ocean acidification promoted the dissolved DMSP degradation and bacterial DMSP-demethylation pathway (inferred by dmdA gene abundance) and weakened the DMS production, causing the decreases of DMS and DMSP. The nutrient from dust deposition (2 mg L−1) was identified as the key factor in enhancing phytoplankton biomass and the organic sulfur compounds concentrations, but trace metals input from dust deposition had no significant effect. This study has identified environmental drivers and suppressors of phytoplankton and biogenic dimethylated sulfur compounds in a changing marine environment, which will enable the effective modeling of future climate change.
Continue reading ‘Responses of biogenic dimethylated sulfur compounds to environmental changes in the northwestern Pacific continental sea’
