Symbiosis establishment is a milestone in the life cycles of most broadcast-spawning corals; however, it remains largely unknown how initial symbiont infection is affected by ocean warming and acidification, particularly for massive corals. This study investigated the combined effects of elevated temperature (29 vs. 31 °C) and pCO2 (~ 450 vs. ~ 1000 μatm) on the recruits of a widespread massive coral, Platygyra daedalea. Results showed that geometric diameter and symbiosis establishment were unaffected by high pCO2, while elevated temperature significantly reduced successful symbiont infection by 50% and retarded the geometric diameter by 6%. Although neither increased temperature, pCO2, nor their interaction affected survival or algal pigmentation of recruits, there was an inverse relationship between symbiont infection rates and survivorship, especially at high temperatures, possibly as a result of oxidative stress caused by algal symbionts under increased temperature. Intriguingly, the proportion of Durusdinium did not increase in recruits at 31 °C, while recruits reared under high pCO2 hosted less Breviolum and more Durusdinium, indicating a high degree of plasticity of early symbiosis and contrasting to the previous finding that heat stress usually leads to the prevalence of thermally tolerant Durusdinium in coral recruits. These results suggest that ocean warming is likely to be more deleterious for the early success of P. daedalea than ocean acidification and provide insights into our understanding of coral-algal symbiotic partnerships under future climatic conditions.
Continue reading ‘Plasticity of symbiont acquisition in new recruits of the massive coral Platygyra daedalea under ocean warming and acidification’Archive Page 234
Plasticity of symbiont acquisition in new recruits of the massive coral Platygyra daedalea under ocean warming and acidification
Published 13 July 2021 Science ClosedTags: algae, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, morphology, mortality, multiple factors, North Pacific, otherprocess, protists, reproduction, temperature
Washington oyster farmer forced to relocate due to ocean acidification
Published 13 July 2021 Web sites and blogs Closed
When people think of climate change refugees, they usually think of island residents who have to move due to rising sea levels.
But climate change can alter the ocean in other ways that affect people — and their businesses.
Dave Nisbet is the owner of Hawaiian Shellfish LLC, a company that specializes in growing seed oysters for growers on the West Coast and Kaua‘i.
He moved to Hawai‘i Island from Washington State in 2009 because ocean acidification was causing deformation in his oysters.
The ocean absorbs roughly 30% of the atmosphere’s carbon dioxide. Excess CO2 becomes CO3 in saltwater. When the ocean absorbs too much CO2, the pH levels of the water decrease, he said.
“When it comes to acidification, areas that have upwelling and in the temperate zones and poles are the first to show the acidification. When you get into the tropics, that can occur later or is delayed,” Nisbet said.
“Hawaiʻi would have seen the issues that we see in the Northwest because we have the upwelling from the cold waters that come up from the bottom and go into the estuary and acidify,” he tells HPR.
Since the beginning of the Industrial Revolution over 200 years ago, the ocean’s acidity levels have increased by 30%. Acidic waters dissolve the shells and skeletons of shellfish and coral, and some species of fish experience difficulty navigating predators.
According to the National Ocean and Atmospheric Administration, with the pace of ocean acidification accelerating, ocean ecosystems will continue to die out before they can adapt.
Continue reading ‘Washington oyster farmer forced to relocate due to ocean acidification’GLOBALink | China’s research icebreaker sets sail for Arctic expedition (text & video)
Published 13 July 2021 Web sites and blogs Closed
Chinese scientists set sail from Shanghai aboard Xuelong 2 on Monday, the country’s first domestically built polar icebreaker, for China’s 12th Arctic expedition.
It marks the first scientific expedition to the Arctic in China’s 14th Five-Year Plan period (2021-2025). The vessel is expected to return to Shanghai in late September, after a trip of 15,000 nautical miles.
The expedition, organized by China’s Ministry of Natural Resources, will see a series of investigations conducted into climate change, ecosystems, ocean acidification, and new pollutants.
The findings are expected to further improve China’s scientific understanding of the mid-ocean ridge.
Continue reading ‘GLOBALink | China’s research icebreaker sets sail for Arctic expedition (text & video)’Microbiome diversity and host immune functions influence survivorship of sponge holobionts under future ocean conditions
Published 12 July 2021 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mortality, multiple factors, North Pacific, otherprocess, physiology, porifera, prokaryotes, temperature
The sponge-associated microbial community contributes to the overall health and adaptive capacity of the sponge holobiont. This community is regulated by the environment and the immune system of the host. However, little is known about the effect of environmental stress on the regulation of host immune functions and how this may, in turn, affect sponge–microbe interactions. In this study, we compared the bacterial diversity and immune repertoire of the demosponge, Neopetrosia compacta, and the calcareous sponge, Leucetta chagosensis, under varying levels of acidification and warming stress based on climate scenarios predicted for 2100. Neopetrosia compacta harbors a diverse microbial community and possesses a rich repertoire of scavenger receptors while L. chagosensis has a less diverse microbiome and an expanded range of pattern recognition receptors and immune response-related genes. Upon exposure to RCP 8.5 conditions, the microbiome composition and host transcriptome of N. compacta remained stable, which correlated with high survival (75%). In contrast, tissue necrosis and low survival (25%) of L. chagosensis was accompanied by microbial community shifts and downregulation of host immune-related pathways. Meta-analysis of microbiome diversity and immunological repertoire across poriferan classes further highlights the importance of host–microbe interactions in predicting the fate of sponges under future ocean conditions.
Continue reading ‘Microbiome diversity and host immune functions influence survivorship of sponge holobionts under future ocean conditions’Combined responses of primary coral polyps and their algal endosymbionts to decreasing seawater pH
Published 12 July 2021 Science ClosedTags: biological response, corals, Indian, laboratory, molecular biology, morphology, mortality, photosynthesis, physiology, protists, reproduction
With coral reefs declining globally, resilience of these ecosystems hinges on successful coral recruitment. However, knowledge of the acclimatory and/or adaptive potential in response to environmental challenges such as ocean acidification (OA) in earliest life stages is limited. Our combination of physiological measurements, microscopy, computed tomography techniques and gene expression analysis allowed us to thoroughly elucidate the mechanisms underlying the response of early-life stages of corals, together with their algal partners, to the projected decline in oceanic pH. We observed extensive physiological, morphological and transcriptional changes in surviving recruits, and the transition to a less-skeleton/more-tissue phenotype. We found that decreased pH conditions stimulate photosynthesis and endosymbiont growth, and gene expression potentially linked to photosynthates translocation. Our unique holistic study discloses the previously unseen intricate net of interacting mechanisms that regulate the performance of these organisms in response to OA.
Continue reading ‘Combined responses of primary coral polyps and their algal endosymbionts to decreasing seawater pH’Ocean acidification and mollusc settlement in Posidonia oceanica meadows: does the seagrass buffer lower pH effects at CO2 vents?
Published 12 July 2021 Science ClosedTags: biological response, BRcommunity, chemistry, community composition, communitymodeling, field, laboratory, Mediterranean, modeling, mollusks, morphology, otherprocess, phanerogams, physiology, vents
Ocean acidification has been broadly recognised to have effects on the structure and functioning of marine benthic communities. The selection of tolerant or vulnerable species can also occur during settlement phases, especially for calcifying organisms which are more vulnerable to low pH–high pCO2 conditions. Here, we use three natural CO2 vents (Castello Aragonese north and south sides, and Vullatura, Ischia, Italy) to assess the effect of a decrease of seawater pH on the settlement of Mollusca in Posidonia oceanica meadows, and to test the possible buffering effect provided by the seagrass. Artificial collectors were installed and collected after 33 days, during April–May 2019, in three different microhabitats within the meadow (canopy, bottom/rhizome level, and dead matte without plant cover), following a pH decreasing gradient from an extremely low pH zone (pH < 7.4), to ambient pH conditions (pH = 8.10). A total of 4659 specimens of Mollusca, belonging to 57 different taxa, were collected. The number of taxa was lower in low and extremely low pH conditions. Reduced mollusc assemblages were reported at the acidified stations, where few taxa accounted for a high number of individuals. Multivariate analyses revealed significant differences in mollusc assemblages among pH conditions, microhabitat, and the interaction of these two factors. Acanthocardia echinata, Alvania lineata, Alvania sp. juv, Eatonina fulgida, Hiatella arctica, Mytilys galloprovincialis, Musculus subpictus, Phorcus sp. juv, and Rissoa variabilis were the species mostly found in low and extremely low pH stations, and were all relatively robust to acidified conditions. Samples placed on the dead matte under acidified conditions at the Vullatura vent showed lower diversity and abundances if compared to canopy and bottom/rhizome samples, suggesting a possible buffering role of the Posidonia on mollusc settlement. Our study provides new evidence of shifts in marine benthic communities due to ocean acidification and evidence of how P. oceanica meadows could mitigate its effects on associated biota in light of future climate change.
Continue reading ‘Ocean acidification and mollusc settlement in Posidonia oceanica meadows: does the seagrass buffer lower pH effects at CO2 vents?’West Coast National Parks work with NOAA to better understand ocean acidification in the rocky intertidal and beyond
Published 12 July 2021 Web sites and blogs ClosedWhat is ocean acidification?
The ocean naturally absorbs over a quarter of the carbon dioxide (CO2) in the atmosphere. So as a result of rising atmospheric CO2 concentrations from burning fossil fuels, levels of CO2 in the ocean are also increasing. When CO2 enters the ocean it reacts with sea water and forms carbonic acid (H2Co3). Carbonic acid is a weak acid which separates or dissociates into a hydrogen ion (H+) and a bicarbonate ion (HCO3-). As more hydrogen ions are formed from this reaction, the pH of the ocean is decreasing, meaning it is becoming more acidic. This is called ocean acidification (OA).
Over the last 200 years, the ocean has become 30% more acidic. The last time it was this acidic was over 300 million years ago. This is presenting new challenges for marine life, and especially for organisms with hard shells and skeletons like oysters, mussels, crabs, and corals.
Learn more about OA and how it impacts marine life in national parks.
Continue reading ‘West Coast National Parks work with NOAA to better understand ocean acidification in the rocky intertidal and beyond’Carla Edworthy tells us about the threat to the world’s marine environment, and research advances in South Africa
It is now widely accepted that ever-increasing emissions of carbon dioxide (CO2) from fossil-fuel burning and other human activities are causing global climate change. Some of the better-known consequences for our oceans are increasing temperatures, sea level rise and more frequent or intense storm events. But by continuously releasing CO2 into the atmosphere, humans are significantly altering the chemistry of the oceans too. Although it is not as widely known, ocean acidification is considered the ‘evil twin’ of global climate change.
The oceans act as a giant sink for carbon because CO2 dissolves rapidly in seawater, initiating a succession of chemical reactions. The ultimate result of these reactions is a decline in the pH of seawater. Although the global average pH is currently about 8.1, this is slowly decreasing as CO2 continues to be absorbed by the oceans from the atmosphere. By the end of the century, the global average pH is predicted to fall to approximately 7.7 if global CO2 emissions continue unabated, which is considered a worst case scenario. Since pH is measured on a log scale, a drop in pH of one unit actually represents a tenfold decrease in acidity. This means that even a small change in pH significantly changes the acidity of seawater.
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Continue reading ‘Ocean acidification’Contrasting drivers and trends of ocean acidification in the subarctic Atlantic
Published 9 July 2021 Science ClosedTags: Arctic, chemistry, field, North Atlantic
The processes of warming, anthropogenic CO2 (Canth) accumulation, decreasing pHT (increasing [H+]T; concentration in total scale) and calcium carbonate saturation in the subarctic zone of the North Atlantic are unequivocal in the time-series measurements of the Iceland (IS-TS, 1985–2003) and Irminger Sea (IRM-TS, 1983–2013) stations. Both stations show high rates of Canth accumulation with different rates of warming, salinification and stratification linked to regional circulation and dynamics. At the IS-TS, advected and stratified waters of Arctic origin drive a strong increase in [H+]T, in the surface layer, which is nearly halved in the deep layer (44.7 ± 3.6 and 25.5 ± 1.0 pmol kg−1 yr−1, respectively). In contrast, the weak stratification at the IRM-TS allows warming, salinification and Canth uptake to reach the deep layer. The acidification trends are even stronger in the deep layer than in the surface layer (44.2 ± 1.0 pmol kg−1 yr−1 and 32.6 ± 3.4 pmol kg−1 yr−1 of [H+]T, respectively). The driver analysis detects that warming contributes up to 50% to the increase in [H+]T at the IRM-TS but has a small positive effect on calcium carbonate saturation. The Canth increase is the main driver of the observed acidification, but it is partially dampened by the northward advection of water with a relatively low natural CO2 content.
Continue reading ‘Contrasting drivers and trends of ocean acidification in the subarctic Atlantic’Positive species interactions strengthen in a high-CO2 ocean
Published 9 July 2021 Science ClosedTags: algae, biological response, community composition, field, fish, methods, multiple factors, performance, primary production, vents
Negative interactions among species are a major force shaping natural communities and are predicted to strengthen as climate change intensifies. Similarly, positive interactions are anticipated to intensify and could buffer the consequences of climate-driven disturbances. We used in situ experiments at volcanic CO2 vents within a temperate rocky reef to show that ocean acidification can drive community reorganization through indirect and direct positive pathways. A keystone species, the algal-farming damselfish Parma alboscapularis, enhanced primary productivity through its weeding of algae whose productivity was also boosted by elevated CO2. The accelerated primary productivity was associated with increased densities of primary consumers (herbivorous invertebrates), which indirectly supported increased secondary consumers densities (predatory fish) (i.e. strengthening of bottom-up fuelling). However, this keystone species also reduced predatory fish densities through behavioural interference, releasing invertebrate prey from predation pressure and enabling a further boost in prey densities (i.e. weakening of top-down control). We uncover a novel mechanism where a keystone herbivore mediates bottom-up and top-down processes simultaneously to boost populations of a coexisting herbivore, resulting in altered food web interactions and predator populations under future ocean acidification.
Continue reading ‘Positive species interactions strengthen in a high-CO2 ocean’The sensitivity of the marine carbonate system to regional ocean alkalinity enhancement
Published 9 July 2021 Science ClosedTags: Arctic, chemistry, globalmodeling, Indian, mitigation, modeling, North Atlantic, North Pacific, regionalmodeling, South Atlantic, South Pacific
Ocean Alkalinity Enhancement (OAE) simultaneously mitigates atmospheric concentrations of CO2 and ocean acidification; however, no previous studies have investigated the response of the non-linear marine carbonate system sensitivity to alkalinity enhancement on regional scales. We hypothesise that regional implementations of OAE can sequester more atmospheric CO2 than a global implementation. To address this, we investigate physical regimes and alkalinity sensitivity as drivers of the carbon-uptake potential response to global and different regional simulations of OAE. In this idealised ocean-only set-up, total alkalinity is enhanced at a rate of 0.25 Pmol a-1 in 75-year simulations using the Max Planck Institute Ocean Model coupled to the HAMburg Ocean Carbon Cycle model with pre-industrial atmospheric forcing. Alkalinity is enhanced globally and in eight regions: the Subpolar and Subtropical Atlantic and Pacific gyres, the Indian Ocean and the Southern Ocean. This study reveals that regional alkalinity enhancement has the capacity to exceed carbon uptake by global OAE. We find that 82–175 Pg more carbon is sequestered into the ocean when alkalinity is enhanced regionally and 156 PgC when enhanced globally, compared with the background-state. The Southern Ocean application is most efficient, sequestering 12% more carbon than the Global experiment despite OAE being applied across a surface area 40 times smaller. For the first time, we find that different carbon-uptake potentials are driven by the surface pattern of total alkalinity redistributed by physical regimes across areas of different carbon-uptake efficiencies. We also show that, while the marine carbonate system becomes less sensitive to alkalinity enhancement in all experiments globally, regional responses to enhanced alkalinity vary depending upon the background concentrations of dissolved inorganic carbon and total alkalinity. Furthermore, the Subpolar North Atlantic displays a previously unexpected alkalinity sensitivity increase in response to high total alkalinity concentrations.
Continue reading ‘The sensitivity of the marine carbonate system to regional ocean alkalinity enhancement’Ocean and atmospheric observations at the remote Ieodo Ocean Research Station in the Northern East China Sea
Published 9 July 2021 Science ClosedTags: chemistry, field, methods, North Pacific
For open ocean environments, it is rare to find continuous, simultaneous air and sea observation records due to the challenges of instrument installation and maintenance. The Ieodo Ocean Research Station (Ieodo ORS), a remote ocean site located in the northern East China Sea with its harsh oceanic and atmospheric environment, provides a platform for the concurrent monitoring of air and sea environments. Since 2014, the Korea Hydrographic and Oceanographic Agency has run the “Ieodo ORS field trip program,” via which researchers are able to stay at the station for a week or more. This work reports technical lessons learned over 5 years from five Ieodo ORS research projects launched in 2016. Over the course of these projects, Ieodo ORS has monitored sea surface temperature, temperature and salinity in the water column, seawater pH, air pollutants, and solar radiation. The purpose of this paper is to facilitate the success of future research activities in similar environments by sharing our experiences and “best practices.”
Continue reading ‘Ocean and atmospheric observations at the remote Ieodo Ocean Research Station in the Northern East China Sea’Influence of ontogenetic development, temperature, and pCO2 on otolith calcium carbonate polymorph composition in sturgeons
Published 8 July 2021 Science ClosedTags: biological response, fish, laboratory, morphology, multiple factors, North Atlantic, physiology, reproduction, temperature
Changes to calcium carbonate (CaCO3) biomineralization in aquatic organisms is among the many predicted effects of climate change. Because otolith (hearing/orientation structures in fish) CaCO3 precipitation and polymorph composition are controlled by genetic and environmental factors, climate change may be predicted to affect the phenotypic plasticity of otoliths. We examined precipitation of otolith polymorphs (aragonite, vaterite, calcite) during early life history in two species of sturgeon, Lake Sturgeon, (Acipenser fulvescens) and White Sturgeon (A. transmontanus), using quantitative X-ray microdiffraction. Both species showed similar fluctuations in otolith polymorphs with a significant shift in the proportions of vaterite and aragonite in sagittal otoliths coinciding with the transition to fully exogenous feeding. We also examined the effect of the environment on otolith morphology and polymorph composition during early life history in Lake Sturgeon larvae reared in varying temperature (16/22 °C) and pCO2 (1000/2500 µatm) environments for 5 months. Fish raised in elevated temperature had significantly increased otolith size and precipitation of large single calcite crystals. Interestingly, pCO2 had no statistically significant effect on size or polymorph composition of otoliths despite blood pH exhibiting a mild alkalosis, which is contrary to what has been observed in several studies on marine fishes. These results suggest climate change may influence otolith polymorph composition during early life history in Lake Sturgeon.
Continue reading ‘Influence of ontogenetic development, temperature, and pCO2 on otolith calcium carbonate polymorph composition in sturgeons’Contribution of maternal mRNA provisioning to embryonic stress response in a reef-building coral
Published 8 July 2021 Science ClosedTags: adaptation, biological response, BRcommunity, corals, laboratory, molecular biology, morphology, otherprocess, physiology, protists, reproduction
Prior to fertilization, mothers provision their oocytes with mRNA that regulates the early stages of development and may additionally include transcripts for proteins that support embryonic stress response early on. At some point during embryogenesis, however, these maternal transcripts are degraded as zygotic transcription activates and intensifies during a phenomenon known as the maternal-to-zygotic transition (MZT). Some evidence suggests that as the MZT progresses, and the effects of maternal transcripts are waning while the zygotic expression is being established, offspring of marine broadcast spawners become more vulnerable to environmental perturbations. In light of escalating threats to marine broadcast spawners, it is critical to understand their reproduction and development, which are essential processes for species resilience by repopulating and replenishing existing populations. Reef building corals, in particular, are under threat from multiple stressors at the local and global scales. Mass mortality has occurred in recent years due to a series of marine heatwaves. In addition, there is chronic stress occurring in the form of ocean acidification, or the decline in pH in surface waters due to the uptake of atmospheric carbon dioxide of anthropogenic origin. Here, we characterize the function of maternal mRNAs, the timeline of the MZT, and sensitivity of gene expression to ocean acidification (OA) in the reef- building coral, Montipora capitata to investigate role of the MZT in embryonic stress response in reef-building corals.
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Continue reading ‘Contribution of maternal mRNA provisioning to embryonic stress response in a reef-building coral’Researchers find ocean acidification threatens local fisheries
Continue reading ‘A microscopic killer lives in SF’s waters’Exposure duration modulates the response of Caribbean corals to global change stressors
Published 7 July 2021 Science ClosedTags: abundance, biological response, BRcommunity, calcification, community composition, corals, laboratory, multiple factors, North Atlantic, photosynthesis, physiology, protists, temperature
Global change, including rising temperatures and acidification, threatens corals globally. Although bleaching events reveal fine-scale patterns of resilience, traits enabling persistence under global change remain elusive. We conducted a 95-d controlled-laboratory experiment investigating how duration of exposure to warming (~28, 31°C), acidification (pCO2 ~ 343 [present day], ~663 [end of century], ~3109 [extreme] μatm), and their combination influences physiology of reef-building corals (Siderastrea siderea, Pseudodiploria strigosa) from two reef zones on the Belize Mesoamerican Barrier Reef System. Every 30 d, net calcification rate, host protein and carbohydrate, chlorophyll a, and symbiont density were quantified for the same coral individual to characterize acclimation potential under global change. Coral physiologies of the two species were differentially affected by stressors and exposure duration was found to modulate these responses. Siderastrea siderea exhibited resistance to end of century pCO2 and temperature stress, but calcification was negatively affected by extreme pCO2. However, S. siderea calcification rates remained positive after 95 d of extreme pCO2 conditions, suggesting acclimation. In contrast, P. strigosa was more negatively influenced by elevated temperatures, which reduced most physiological parameters. An exception was nearshore P. strigosa, which maintained calcification rates under elevated temperature, suggesting local adaptation to the warmer environment of their natal reef zone. This work highlights how tracking coral physiology across various exposure durations can capture acclimatory responses to global change stressors.
Continue reading ‘Exposure duration modulates the response of Caribbean corals to global change stressors’Ocean acidification amplifies multi-stressor impacts on global marine invertebrate fisheries
Published 7 July 2021 Science ClosedTags: abundance, biological response, crustaceans, fisheries, globalmodeling, individualmodeling, modeling, mollusks, otherprocess, physiology
Elevated atmospheric carbon dioxide (CO2) is causing global ocean changes and drives changes in organism physiology, life-history traits, and population dynamics of natural marine resources. However, our knowledge of the mechanisms and consequences of ocean acidification (OA) – in combination with other climatic drivers (i.e., warming, deoxygenation) – on organisms and downstream effects on marine fisheries is limited. Here, we explored how the direct effects of multiple changes in ocean conditions on organism aerobic performance scales up to spatial impacts on fisheries catch of 210 commercially exploited marine invertebrates, known to be susceptible to OA. Under the highest CO2 trajectory, we show that global fisheries catch potential declines by as much as 12% by the year 2100 relative to present, of which 3.4% was attributed to OA. Moreover, OA effects are exacerbated in regions with greater changes in pH (e.g., West Arctic basin), but are reduced in tropical areas where the effects of ocean warming and deoxygenation are more pronounced (e.g., Indo-Pacific). Our results enhance our knowledge on multi-stressor effects on marine resources and how they can be scaled from physiology to population dynamics. Furthermore, it underscores variability of responses to OA and identifies vulnerable regions and species.
Continue reading ‘Ocean acidification amplifies multi-stressor impacts on global marine invertebrate fisheries’Cod is a keystone species in marine ecosystems. It shapes the conditions for a large number of other species in the sea and is also of great importance both economically and culturally. However, the Swedish Atlantic cod stocks are on the verge of collapse with serious population declines observed in the Baltic Sea and on the Swedish west coast. Will the already weakened stocks meet another challenge; climate change?
Research based on the latest climate models shows that the temperature will rise and lead to local heat waves. Ocean acidification will increase, and salinity will reduce in the Baltic Sea and part of the west coast. Together, these climate effects will dramatically alter the marine environment around Sweden.
Climate effects cause physiological stress
Each of these changes can cause physiological stress in marine organisms. In order to better understand the anticipated fate of cod in a changing climate, this project aims to investigate how Atlantic cod (Gadus morhua) from coastal populations in the Baltic Sea and the North Sea respond to the cumulative effects of climate change factors such as reduced salinity (freshening), reduced pH (ocean acidification) and increased temperature (warming events).
Continue reading ‘Fish in a changing climate – can cod cope?’Ocean acidification and direct interactions affect coral, macroalga, and sponge growth in the Florida Keys
Published 6 July 2021 Science ClosedTags: algae, biological response, BRcommunity, calcification, corals, laboratory, morphology, North Atlantic, porifera
Coral reef community composition, function, and resilience have been altered by natural and anthropogenic stressors. Future anthropogenic ocean and coastal acidification (together termed “acidification”) may exacerbate this reef degradation. Accurately predicting reef resilience requires an understanding of not only direct impacts of acidification on marine organisms but also indirect effects on species interactions that influence community composition and reef ecosystem functions. In this 28-day experiment, we assessed the effect of acidification on coral–algal, coral–sponge, and algal–sponge interactions. We quantified growth of corals (Siderastrea radians), fleshy macroalgae (Dictyota spp.), and sponges (Pione lampa) that were exposed to local summer ambient (603 μatm) or elevated (1105 μatm) pCO2 seawater. These species are common to hard-bottom communities, including shallow reefs, in the Florida Keys. Each individual was maintained in isolation or paired with another organism. Coral growth (net calcification) was similar across seawater pCO2 and interaction treatments. Fleshy macroalgae had increased biomass when paired with a sponge but lost biomass when growing in isolation or paired with coral. Sponges grew more volumetrically in the elevated seawater pCO2 treatment (i.e., under acidification conditions). Although these results are limited in temporal and spatial scales due to the experimental design, they do lend support to the hypothesis that acidification may facilitate a shift towards increased sponge and macroalgae abundance by directly benefiting sponge growth which in turn may provide more dissolved inorganic nitrogen to macroalgae in the Florida Keys.
Continue reading ‘Ocean acidification and direct interactions affect coral, macroalga, and sponge growth in the Florida Keys’Ocean acidification may mitigate negative effects of warming on carbon burial potential in subtidal unvegetated estuarine sediments
Published 6 July 2021 Science ClosedTags: biological response, laboratory, mitigation, multiple factors, primary production, sediment
Estuarine sediments make an important contribution to the global carbon cycle, but we do not know how this will change under a future climate, which is expected to have lower pH oceans and frequent high-temperature days. Six combinations of warming and partial pressures of CO2 (pCO2) were chosen to investigate the combined and individual effects of short-term pressures on the diel metabolic response of shallow unvegetated sediments ex-situ. Whereas warming significantly increased respiration, making sediments more heterotrophic, high-pCO2 increased net primary productivity, resulting in less heterotrophic sediments. As a result, warming decreased the carbon burial potential of estuarine sediments and high-pCO2 had the opposite effect. High-pCO2 mitigates the negative effects of warming on benthic metabolism under the combined scenario, with carbon burial similar to that expected under high-pCO2 conditions alone. Climate scenarios also changed the diurnal pCO2 variation, with ranges increasing by 33% with warming, and almost doubling under high-pCO2 conditions. An additive response in pCO2 variability was observed under the combined scenario, increasing to 2.3× the current diel-pCO2 range, highlighting the reduced buffering capacity of the water associated with a high CO2 climate. Future carbon burial and export under increased frequencies of unseasonably warm days projected for mid and end of century (30% and 50% of days-per-year, respectively) were estimated with and without ocean acidification. By 2100, warming alone could decrease annual estuarine sediment burial potential by 25%. However, ocean acidification could mitigate the negative effects of more frequent high-temperature days and increase carbon burial potential over current conditions by ~18%.
Continue reading ‘Ocean acidification may mitigate negative effects of warming on carbon burial potential in subtidal unvegetated estuarine sediments’
