Foraminifera host diverse microbial communities that can shift in response to changing environmental conditions. To characterize climate change impacts on the foraminifera microbiome across life stages, we exposed adult Marginopora vertebralis (Large Benthic Foraminifera) to pCO2 and temperature scenarios representing present day, 2050 and 2100 levels and raised juveniles under present day and 2050 conditions. While treatment condition had no significant effect on the seawater microbial communities, exposure to future scenarios significantly altered both adult and juvenile microbiomes. In adults, divergence between present day and 2050 or 2100 conditions was primarily driven by a reduced relative abundance of Oxyphotobacteria under elevated temperature and pCO2. In juveniles, the microbial shift predominantly resulted from changes in the proportion of Proteobacteria. Indicator species analysis identified numerous treatment‐specific indicator taxa, most of which were indicative of present day conditions. Oxyphotobacteria, previously reported as putative symbionts of foraminifera, were indicative of present day and 2050 conditions in adults, but of present day conditions only in juveniles. Overall, we show that the sensitivity of the M. vertebralis microbiome to climate change scenarios extends to both life stages and primarily correlates with declines in Oxyphotobacteria and shifts in Proteobacteria under elevated temperature and pCO2.
Continue reading ‘Simulated future conditions of ocean warming and acidification disrupt the microbiome of the calcifying foraminifera Marginopora vertebralis across life stages’Posts Tagged 'laboratory'
Simulated future conditions of ocean warming and acidification disrupt the microbiome of the calcifying foraminifera Marginopora vertebralis across life stages
Published 27 October 2020 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, mesocosms, multiple factors, otherprocess, prokaryotes, protists, South Pacific, temperature
Ocean acidification disrupts the orientation of postlarval Caribbean spiny lobsters
Published 23 October 2020 Science ClosedTags: biological response, crustaceans, laboratory, North Atlantic, performance
Anthropogenic inputs into coastal ecosystems are causing more frequent environmental fluctuations and reducing seawater pH. One such ecosystem is Florida Bay, an important nursery for the Caribbean spiny lobster, Panulirus argus. Although adult crustaceans are often resilient to reduced seawater pH, earlier ontogenetic stages can be physiologically limited in their tolerance to ocean acidification on shorter time scales. We used a Y-maze chamber to test whether reduced-pH seawater altered the orientation of spiny lobster pueruli toward chemical cues produced by Laurencia spp. macroalgae, a known settlement cue for the species. We tested the hypothesis that pueruli conditioned in reduced-pH seawater would be less responsive to Laurencia spp. chemical cues than pueruli in ambient-pH seawater by comparing the proportion of individuals that moved to the cue side of the chamber with the proportion that moved to the side with no cue. We also recorded the amount of time (sec) before a response was observed. Pueruli conditioned in reduced-pH seawater were less responsive and failed to select the Laurencia cue. Our results suggest that episodic acidification of coastal waters might limit the ability of pueruli to locate settlement habitats, increasing postsettlement mortality.
Short-term effects of increased CO2, nitrate and temperature on photosynthetic activity in Ulva rigida (Chlorophyta) estimated by different pulse amplitude modulated fluorometers and oxygen evolution
Published 22 October 2020 Science ClosedTags: algae, biological response, laboratory, multiple factors, nutrients, photosynthesis, temperature
Short-term effects of pCO2 (700 – 380 ppm; HC-LC) and nitrate content (50-5 βM; HN-LC) on photosynthesis, estimated by different pulse amplitude modulated (PAMs) fluorometers and by oxygen evolution, were investigated in Ulva rigida (Chlorophyta) under solar radiation (ex-situ) and in the laboratory under artificial light (in-situ). After 6-days of incubation at ambient temperature (AT), algae were subjected to a 4 oC-temperature increase (AT+4oC) for 3 d. Both in-situ and ex-situ, maximal electron transport rate (ETRmax) and in situ gross photosynthesis (GP) measured by O2 evolution presented the highest values under HCHN, and the lowest under HCLN, across all measuring systems. Maximal quantum yield (Fv/Fm), and ETRmax of PSII (ETR(II)max) and of PSI (ETR(I)max), decreased under HCLN under AT+4°C. Ex situ ETR was higher than in situ ETR. At noon, Fv/Fm decreased (indicating photoinhibition), whereas ETR(II)max and maximal non-photochemical quenching (NPQmax) increased. ETR(II)max decreased under AT+4oC in contrast to Fv/Fm, photosynthetic efficiency (αETR) and saturated irradiance (EK). Thus, U. rigida exhibited a decrease in photosynthetic production under acidification, LN levels and AT+4oC. These results emphasize the importance of studying the interactive effects between environmental parameters using in-situ vs. ex-situ conditions when aiming to evaluate the impact of global change on marine macroalgae.
Early development and metabolic rate of the sea louse Caligus rogercresseyi under different scenarios of temperature and pCO2
Published 22 October 2020 Science ClosedTags: biological response, crustaceans, laboratory, mortality, physiology, reproduction, South Pacific, zooplankton
Highlights
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The temperature has a significant effect on the hatching time of C. royercresseyi.
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Combination of pCO2 and temperature has a significant effect on survival in C. rogercresseyi.
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The combination of pCO2 and temperature had no impact on the size of nauplius I, nauplius II and copepodid stage.
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Only the temperature has a significant effect on oxygen consumption rate of C. royercresseyi.
Abstract
Anthropogenic CO2 emissions have led to ocean acidification and a rise in the temperature. The present study evaluates the effects of temperature (10, 15 and 20 °C) and pCO2 (400 and 1200 μatm) on the early development and oxygen consumption rate (OCR) of the sea louse Caligus rogercresseyi. Only temperature has an effect on the hatching and development times of nauplius I. But both factors affected the development time of nauplius II (<temperature = longer development time). Copepodid survival time was also affected by temperature and pCO2, at 10 °C and 400 μatm, survival was 30 and 44% longer than at 15 and 20 °C. OCRs were impacted by temperature but not by pCO2. In all treatments, OCR was lower for nauplius II than for the copepodid. Our results show the need to further evaluate the effects of a combination of environmental drivers on the performance of C. rogercresseyi, in a changing and uncertain future.
Effects of temperature and pH on the egg production and hatching success of a common Korean copepod
Published 21 October 2020 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, North Pacific, reproduction, temperature, zooplankton
The recent accelerated ocean acidification and global warming caused by increased atmospheric carbon dioxide may have an impact on the physiology and ecology of marine animals. This study was conducted to determine the egg production rate (EPR) and hatching success (EHS) of Acartia ohtsukai in response to the combined effects of an increase in temperature and a lower pH. Acartiaohtsukai with fresh surface seawater were collected in the northwestern Yeoja Bay of Korea in September 2017. The temperature and pH conditions applied included two different pH levels (representing the present: 7.9 and the future: 7.6) and three temperature values (26 °C, 28 °C, and 30 °C). In the pH 7.9, EPR significantly increased with increased temperature, but in pH 7.6, it significantly decreased as the temperature increased. EHS was lower in pH 7.6 than in pH 7.9. These results suggest that changes in the marine environment due to global warming and ocean acidification may affect Acartia populations and cause overall fluctuations in copepods of the genus Acartia.
Lack of oxidative damage on temperate juvenile catsharks after a long-term ocean acidification exposure
Published 20 October 2020 Science ClosedTags: biological response, fish, laboratory, molecular biology, North Atlantic, physiology
Ocean acidification is a consequence of chemical changes driven mainly by a continuous uptake of carbon dioxide, resulting in pH decrease. This phenomenon represents an additional threat to marine life, with expected effects ranging from changes in behavioral responses and calcification rates to the potential promotion of oxidative stress. To unravel the impacts of ocean acidification on the antioxidant system of sharks, we performed a long-term exposure (9 months, since early embryogenesis) to high CO2 conditions (pCO2 ~ 900 μatm) on a temperate shark (Scyliorhinus canicula). The following biomarkers were measured: enzymatic antioxidant defense (superoxide dismutase, catalase and glutathione peroxidase), protein repair and removal (heat shock proteins and ubiquitin), and oxidative damage on lipids (malondialdehyde) and DNA (8-hydroxy-2′-deoxyguanosine). Changes in the antioxidant enzyme defense were restricted to an increase in catalase activity in the muscle, an enzyme that plays a major role in oxidative stress mitigation. On the other hand, no evidence of oxidative damage was found, indicating that the observed increase in catalase activity may be enough to neutralize the effects of potentially higher reactive oxygen species. These results further indicate that these sharks’ antioxidant system can successfully cope with the levels of carbon dioxide projected for the end of the century. Nonetheless, the interaction between ocean acidification and the rise in temperature expected to occur in a near future may disturb their antioxidant capacity, requiring further investigation.
Temperature affects the reproductive outputs of coral-eating starfish Acanthaster spp. after adult exposure to near-future ocean warming and acidification
Published 20 October 2020 Science ClosedTags: biological response, echinoderms, laboratory, mortality, multiple factors, reproduction, South Pacific, temperature
Highlights
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It is possible to keep adult COTS in modified conditions for several months with minimal losses.
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The natural peak of reproduction for COTS in New Caledonia is around the end of the calendar year.
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A +2 °C warming exposure of 3–4 months have detrimental effects on quality and quantity of COTS eggs along with fertilisation success.
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During sub-optimal spawning season, COTS fertilisation success drops by 3-fold for animals exposed to elevated temperature.
Abstract
Outbreaks of the coral-eating crown-of-thorns starfish Acanthaster spp. (COTS) have become to be amongst the most severe threats to coral reefs worldwide. Although most research has focused on COTS early development, it remains unclear how COTS populations will keep pace with changing ocean conditions. Since reproduction is a key process contributing to outbreaks, we investigated the reproductive success of adult COTS acclimated for 3–4 months to different treatment combinations of ambient conditions, ocean warming (+2 °C) and acidification (−0.35 pH). Our results suggest that the optimal breeding season in New Caledonia is concentrated around the end of the calendar year, when water temperature reaches >26 °C. We found negative effects of temperature on egg metrics, fertilisation success, and GSI, conflicting with previously documented effects of temperature on echinoderm reproductive outputs. Fertilisation success dropped drastically (more than threefold) with elevated temperature during the late breeding season. In contrast, we detected no effects of near-future acidification conditions on fertilisation success nor GSI. This is the first time that COTS reproduction is compared among individuals acclimated to different conditions of warming and acidification. Our results highlight the importance of accounting for adult exposure to better understand how COTS reproduction may be impacted in the face of global change.
Decreased pH impairs sea urchin resistance to predatory fish: a combined laboratory-field study to understand the fate of top-down processes in future oceans
Published 20 October 2020 Science ClosedTags: echinoderms, field, laboratory, Mediterranean, morphology, mortality, performance
Highlights
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Combined laboratory-field approach to study OA effects on predator-prey interactions.
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Adult sea urchins mechanical defence strategies are compromised by decreased pH.
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Field data confirm grater vulnerability to predation of sea urchins exposed to lower pH.
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Future more acidic seawaters will impair sea urchin resistance to predatory fish.
Abstract
Changing oceans represent a serious threat for a wide range of marine organisms, with severe cascading effects on ecosystems and their services. Sea urchins are particularly sensitive to decreased pH expected for the end of the century and their key ecological role in regulating community structure and functioning could be seriously compromised. An integrated approach of laboratory and field experiments has been implemented to investigate the effects of decreased pH on predator-prey interaction involving sea urchins and their predators. Our results suggest that under future Ocean Acidification scenarios adult sea urchins defence strategies, such as spine length, test robustness and oral plate thickness, could be compromised together with their survival chance to natural predators. Sea urchins represent the critical linkage between top-down and bottom-up processes along Mediterranean rocky reefs, and the cumulative impacts of global and local stressors could lead to a decline producing cascading effects on benthic ecosystems.
A new “business as usual” climate scenario and the stress response of the Caribbean coral Montastraea cavernosa
Published 16 October 2020 Science ClosedTags: abundance, biological response, community composition, corals, laboratory, molecular biology, multiple factors, North Atlantic, otherprocess, performance, photosynthesis, prokaryotes, protists, temperature
The climate change related decline of shallow (<30 m) coral reef ecosystems has been driven by the mortality of scleractinian corals caused primarily by the phenomenon known as “coral bleaching.” But despite pervasive phase shifts and macroalgal dominance on many coral reefs, some coral species have persisted. One of those species is Montastraea cavernosa which has been categorized as resilient to a range of biotic and abiotic stressors. In order to understand the mechanism(s) of resistance in this coral, we present the results of a thermal stress and ocean acidification (OA) experiment on M. cavernosa, both its brown and orange color morphs, representing conditions predicted by the Representative Concentration Pathway (RCP) 6.0 scenario in the year 2100. We assessed the community response of the prokaryotic microbiome, the photophysiological response of the endosymbiotic Symbiodiniaceae and the molecular responses of critical pathways in the host by quantifying transcript abundances of genes encoding fluorescent proteins, heat shock proteins, antioxidant enzymes and regulators of apoptosis. After a 12 d acclimatization experiment, no visible bleaching was observed in any treatment, and the excitation pressure on photosystem II of the symbiotic Symbiodiniaceae showed no effects of the independent or interactive effects of thermal stress and OA, while only minor, but significant, changes in the prokaryotic microbiome were observed when exposed to RCP 6.0 predicted OA conditions. At the end of the experiment, the host heat shock protein 90 showed an increase in transcript abundance under the combined effects of thermal stress and OA compared to high temperatures alone, but these treatment groups were not significantly different from treatments under normal temperatures. While Bax, an activator of apoptosis, was significantly higher under thermal stress alone compared to control samples. Taken together, M. cavernosa, exhibits ecological stability over time and this may be based on its physiological persistence, resistance and resilience when experimentally exposed to the ecologically realistic RCP 6.0 climate model predictions.
Long-term m5C methylome dynamics parallel phenotypic adaptation in the cyanobacterium Trichodesmium
Published 16 October 2020 Science ClosedTags: adaptation, biological response, growth, laboratory, nitrogen fixation, otherprocess, prokaryotes
A major challenge in modern biology is understanding how the effects of short-term biological responses influence long-term evolutionary adaptation, defined as a genetically determined increase in fitness to novel environments. This is particularly important in globally important microbes experiencing rapid global change, due to their influence on food webs, biogeochemical cycles, and climate. Epigenetic modifications like methylation have been demonstrated to influence short-term plastic responses, which ultimately impact long-term adaptive responses to environmental change. However, there remains a paucity of empirical research examining long-term methylation dynamics during environmental adaptation in non-model, ecologically important microbes. Here, we show the first empirical evidence in a marine prokaryote for long-term m5C methylome modifications correlated with phenotypic adaptation to CO2, using a 7-year evolution experiment (1000+ generations) with the biogeochemically-important marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly changed in response to high (750 µatm) CO2 exposure and were maintained for at least 4.5 years of CO2 selection. After 7 years of CO2 selection, however, m5C methylation levels that initially responded to high-CO2 returned to ancestral, ambient CO2 levels. Concurrently, high-CO2 adapted growth and N2 fixation rates remained significantly higher than those of ambient CO2 adapted cell lines irrespective of CO2 concentration, a trend consistent with genetic assimilation theory. These data demonstrate the maintenance of CO2-responsive m5C methylation for 4.5 years alongside phenotypic adaptation before returning to ancestral methylation levels. These observations in a globally distributed marine prokaryote provide critical evolutionary insights into biogeochemically important traits under global change.
Functionally redundant herbivores: urchin and gastropod grazers respond differently to ocean warming and rising CO2
Published 16 October 2020 Science ClosedTags: biological response, echinoderms, laboratory, mollusks, multiple factors, performance, physiology, temperature
Future ocean CO2 and temperatures are predicted to increase primary productivity across tropical marine habitats, potentially driving a shift towards algal-dominated systems. However, increased consumption of algae by benthic grazers could potentially counter this shift. Yet, the response of different grazer species to future conditions will be moderated by their physiologies, meaning that they may not be functional equivalents. Here, we experimentally assessed the physiological response of key grazers — the sea urchin Heliocidaris crassispina and 2 gastropod species, Astralium haematragum and Trochus maculatus— to predicted CO2 concentrations (400, 700 and 1000 ppm) and temperature conditions (ambient, +3 and +5°C). In line with metabolic theory, we found that urchin metabolic rate increased at future temperatures regardless of CO2 conditions, with evidence of metabolic acclimation to higher temperatures. The metabolic rate of A. haematragum was depressed only by CO2, whereas T. maculatus /i>initially had elevated metabolic rates at moderate CO2, which were depressed by the combination of the highest CO2 concentration and temperatures. Taxa showed differential survival, with no urchin mortality under any future conditions but substantial mortality of both gastropods under elevated temperatures regardless of CO2 concentration. Importantly, all species had substantially reduced algal consumption in response to elevated CO2, though the urchins only demonstrated an energetic mismatch under combined future CO2 and temperature. Therefore, despite sharing an ecological niche, these key grazers are likely to be differentially affected by future environmental conditions, potentially reducing the strength of eco logical compensatory responses depending on the functional redundancy in this grazing community.
The regulations of varied carbon-nitrogen supplies to physiology and amino acid contents in Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta)
Published 15 October 2020 Science ClosedTags: algae, biological response, fisheries, growth, laboratory, North Pacific, photosynthesis, physiology
Highlights
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Growth, photosynthesis, and amino acid accumulation of G. lemaneiformis increases with higher nitrogen application.
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Application of nitrogen fertiliser maybe an effective way to increase G. lemaneiformis yield with improved nutrient quality.
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Seawater nitrogen enrichment may alleviate the physiological stress caused by high CO2 on G. lemaneiformis in the future.
Abstract
Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta) is an important economic alga in Southern China. In the present study, G. lemaneiformis thalli collected from Nan’ao Island, China, were cultured in six different treatments with three carbon supply levels (20, 400 and 1000 μatm) and two nitrogen supply levels (15 and 300 μmol L−1). The thalli were used in the examination of the effects of altered carbon supply and high nitrogen content in seawater on the growth, photosynthetic characteristics and amino acid (AA) content of this farmed algal species. Regardless of nitrogen levels, the relative growth rate of G. lemaneiformis increased with CO2 supply. Decrease and increase in the carbon supply of the culture both decreased the maximum quantum yield of photosystem PS II (Fv/Fm), initial slope of the rapid light curves (ɑ), non-photochemical quenching, maximum relative electron transport rate and AA content of G. lemaneiformis thalli. Moreover, under low and high CO2 supply conditions, the growth rates, Fv/Fm, antioxidant activities (SOD, CAT and POD) and AAs of G. lemaneiformis increases with higher nitrogen application (300 μmol L−1). Our results indicated that the inhibition of growth, photosynthesis, and AA accumulation of G. lemaneiformis can be alleviated by appropriately increasing the concentration of nitrogen in seawater. We suggest that during G. lemaneiformis mariculture, the appropriate application of nitrogen fertiliser may be an effective way to increase algal yield with improved nutrient quality, and seawater nitrogen enrichment may alleviate the physiological stress caused by high CO2 on G. lemaneiformis in the future.
Response of bacterial communities in Barents Sea sediments in case of a potential CO2 leakage from carbon reservoirs
Published 15 October 2020 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, laboratory, mitigation, otherprocess, physiology, prokaryotes
Highlights
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Simulation of real conditions of a CCS site are essentials for environmental risk assessments.
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Marine bacteria may adapt to a new situation in case of acidification event for a short time.
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Marine bacteria community is altered in case of a CO2 leakage after 3 weeks in long-term simulation.
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Results did not show a potential recovery of marine bacteria when CO2 was stopped within the monitored period.
Abstract
Carbon capture and storage sites in Barents Sea shelf are currently in progress as part of climate change mitigation activities. However environmental impacts of a possible CO2 seepage on bacterial community are lacking knowledge. This work addressed potential consequences on bacterial communities from Snøvit region in Barents Sea sediments. Long-term experiment (92 days) was carried out mimicking realistic conditions of pressure (∼30 bars) using the unique hyperbaric chamber (Karl Erik TiTank). The experiment was divided in three stages: i) 21 days of no CO2, ii) 50 days of simulation of carbon dioxide leakage (depletion of pH to 7.0) and iii) 14 days emulating a leakage cessation. Results suggested that bacterial communities can adapt to a CO2 leakage in short term. However, bacteria showed negative effects in terms of activity, community structure, and number of cells after long term CO2 exposure. After CO2 leakage cessation, bacterial communities did not show a significant recovery. These findings highlighted that, even though marine bacteria showed adaptation to the new conditions (acidified environment), in case of a small but continuous CO2 leakage marine bacteria might not be recovered upon pre-exposure status.
Co-culture with Synechococcus facilitates growth of Prochlorococcus under ocean acidification conditions
Published 15 October 2020 Science ClosedTags: abundance, biological response, BRcommunity, community composition, growth, laboratory, otherprocess, phytoplankton
Anthropogenic CO2 emissions are projected to lower the pH of the ocean 0.3 units by 2100. Previous studies suggested that Prochlorococcus and Synechococcus, the numerically dominant phytoplankton in the oceans, have different responses to elevated CO2 that may result in a dramatic shift in their relative abundances in future oceans. Here we showed that the exponential growth rates of these two genera respond to future CO2 conditions in a manner similar to other cyanobacteria, but Prochlorococcus strains had significantly lower realized growth rates under elevated CO2 regimes due to poor survival after exposure to fresh culture media. Despite this, a Synechococcus strain was unable to outcompete a Prochlorococcus strain in co‐culture at elevated CO2. Under these conditions, Prochlorococcus‘ poor response to elevated CO2 disappeared, and Prochlorococcus’ relative fitness showed negative frequency dependence, with both competitors having significant fitness advantages when initially rare. These experiments suggested that the two strains should be able to co‐exist indefinitely in co‐culture despite sharing nearly identical nutritional requirements. We speculate that negative frequency dependence exists due to reductive Black Queen evolution that has resulted in a passively mutualistic relationship analogous to that connecting Prochlorococcus with the “helper” heterotrophic microbes in its environment.
Continue reading ‘Co-culture with Synechococcus facilitates growth of Prochlorococcus under ocean acidification conditions’Coastal acidification and deoxygenation enhance settlement but do not influence movement behavior of creeping polyps of the irukandji jellyfish, Alatina alata (cubozoa)
Published 14 October 2020 Science ClosedTags: biological response, cnidaria, laboratory, morphology, mortality, multiple factors, oxygen, performance, reproduction, South Pacific
Highlights
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Deoxygenation enhanced the survival of the creeping polyps of Alatina alata.
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More creeping polyps settled under low pH and low dissolved O2 (DO) treatments than under normal pH and DO conditions.
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Exposure to low pH and DO did not influence the number of tentacles, mobility or movement velocity of the creeping polyps.
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The Irukandji jellyfish may persist in coastal areas with coastal deoxygenation and acidification.
Abstract
Deoxygenation and acidification co-occur in many coastal ecosystems because nutrient enrichment produces excess organic matter that intensifies aerobic respiration during decomposition, thereby depleting O2, increasing CO2 and lowering pH. Despite this link between coastal deoxygenation (CD) and acidification (CA), and evidence that both stressors pose a risk to marine fauna, few studies have examined the effects of these drivers in combination on marine animals including invertebrates. Here, we studied the individual and combined effects of CD (∼1.5 mg L−1 O2) and CA (∼7.7 pH) on the survival, number of tentacles, settlement and movement behaviours of creeping polyps of the Irukandji jellyfish, Alatina alata. Low DO increased the survival rate (17% more) of the creeping polyps. 12% more creeping polyps settled in low pH than ambient pH and 16.7% more settled in low DO than ambient DO treatment. Exposure to CA and CD did not influence the number of tentacles, mobility or movement velocity of the creeping polyps, but after 4 h exposure to the treatments, they moved approximately half as fast. Our results indicate that CD can enhance survival and settlement success, but CA does not intensify these outcomes on A. alata creeping polyps.
Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosus
Published 14 October 2020 Science ClosedTags: Arctic, biological response, crustaceans, field, laboratory, multiple factors, physiology, salinity
Highlights
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Climate change is leading to changes in salinity and pCO2 in arctic/sub-arctic coastal ecosystems.
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We examined Gammarus setosus at 3 sites along a salinity gradient in the field and laboratory.
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Reduced salinity had more of an effect than elevated pCO2 by reducing energy budgets.
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Lower salinities increased ion transporting capacities in the laboratory but not in the field.
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G. setosus at lower salinity sites have lower energy budgets suggesting impacts on performance.
Abstract
Climate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-/Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2 (∼1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2 in the higher-salinity population. Elevated pCO2 did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2 in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).
Ocean acidification impedes gustation-mediated feeding behavior by disrupting gustatory signal transduction in the black sea bream, Acanthopagrus schlegelii
Published 14 October 2020 Science ClosedTags: biological response, fish, laboratory, molecular biology, North Pacific, performance
Highlights
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Gustation-mediated feeding behavior of sea bream was significantly affected by OA.
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Neurotransmitter levels and the expression of key genes were suppressed by OA.
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OA hinders feeding of sea bream by obstructing gustatory signal transduction.
Abstract
Growing evidence suggests that ocean acidification (OA) may affect animal behaviors such as feeding. Although gustation plays a crucial role in evaluating the quality and palatability of food and ultimately influences whether or not teleosts consume the food, the potential impact of OA on gustation-mediated feeding behavior remains unknown. In this study, gustation mediated-feeding behavior, as indicated by the consumption rate (CR) and swallowing rate (SR) of agar pellets with or without feed upon OA exposure was investigated in black sea bream (Acanthopagrus schlegelii). Results showed that the exposure to acidified seawater led to significant reductions in the CR and SR of feed-containing agar pellets. In addition, the in vivo contents of three neurotransmitters and expression of genes from the gustatory signal transduction pathway were all significantly suppressed by the OA treatment. In general, the data obtained indicated that OA may hinder the gustation-mediated feeding behavior of A. schlegelii by disrupting gustatory signal transduction, which may aggravate the issue of food shortage for wild populations of black sea bream.
Ocean acidification amplifies the olfactory response to 2-phenylethylamine: altered cue reception as a mechanistic pathway?
Published 14 October 2020 Science ClosedTags: biological response, crustaceans, laboratory, North Atlantic, performance, physiology
With carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. We demonstrate that this dietary predator cue for mammals and sea lampreys is an attractant for hermit crabs. Furthermore, we show that the potency of the cue increases at pH levels expected for the year 2100. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.
Combining mesocosms with models to unravel the effects of global warming and ocean acidification on temperate marine ecosystems
Published 13 October 2020 Science ClosedTags: biological response, BRcommunity, community composition, communitymodeling, fish, fisheries, laboratory, mesocosms, modeling, mortality, multiple factors, otherprocess, performance, primary production, temperature
Ocean warming and species exploitation have already caused large-scale reorganization of biological communities across the world. Accurate projections of future biodiversity change require a comprehensive understanding of how entire communities respond to global change. We combined a time-dynamic integrated food web modelling approach (Ecosim) with a community-level mesocosm experiment to determine the independent and combined effects of ocean warming and acidification, and fisheries exploitation, on a temperate coastal ecosystem. The mesocosm enabled important physiological and behavioural responses to climate stressors to be projected for trophic levels ranging from primary producers to top predators, including sharks. We show that under current-day rates of exploitation, warming and ocean acidification will benefit most species in higher trophic levels (e.g. mammals, birds, demersal finfish) in their current climate ranges, with the exception of small pelagic fish, but these benefits will be reduced or lost when these physical stressors co-occur. We show that increases in exploitation will, in most instances, suppress any positive effects of human-driven climate change, causing individual species biomass to decrease at high-trophic levels. Species diversity at the trailing edges of species distributions is likely to decline in the face of ocean warming, acidification and exploitation. We showcase how multi-level mesocosm food web experiments can be used to directly inform dynamic food web models, enabling the ecological processes that drive the responses of marine ecosystems to scenarios of global change to be captured in model projections and their individual and combined effects to be teased apart. Our approach for blending theoretical and empirical results from mesocosm experiments with computational models will provide resource managers and conservation biologists with improved tools for forecasting biodiversity change and altered ecosystem processes due to climate change.
Continue reading ‘Combining mesocosms with models to unravel the effects of global warming and ocean acidification on temperate marine ecosystems’The marine gastropod Crepidula fornicata remains resilient to ocean acidification across two life history stages
Published 12 October 2020 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess
Rising atmospheric CO2 reduces seawater pH causing ocean acidification (OA). Understanding how resilient marine organisms respond to OA may help predict how community dynamics will shift as CO2 continues rising. The common slipper shell snail Crepidula fornicata is a resilient marine gastropod native to eastern North America, which has been a successful invader along the western European coastline and elsewhere. To examine its potential resilience to OA, we conducted two controlled laboratory experiments. First, we examined several phenotypes and genome-wide gene expression of C. fornicata in response to pH treatments (7.5, 7.6, 8.0) throughout the larval stage and then tested how conditions experienced as larvae influenced juvenile stages (i.e. carryover effects). Second, we examined genome-wide gene expression patterns of C. fornicata larvae in response to acute (4, 10, 24 and 48 hours) pH treatment (7.5, 8.0). Both C. fornicata larvae and juveniles exhibited resilience to OA and gene expression responses highlight the role of transcriptome plasticity in OA resilience. Larvae did not exhibit reduced growth under OA until they were at least 4 days old. These phenotypic effects were preceded by broad transcriptomic changes, which likely serve as an acclimation mechanism for combating reduced pH conditions frequently experienced in littoral zones. Delayed metamorphosis was observed for larvae reared at reduced pH. Although juvenile size reflected larval rearing pH conditions, no carryover effects in juvenile growth rates were observed. Transcriptomic analyses suggest increased metabolism under OA, which may indicate compensation in reduced pH environments. Time course transcriptomic analyses suggest energetic burdens experienced under OA eventually dissipate, allowing C. fornicata to reduce metabolic demands and acclimate to reduced pH. This study highlights the importance of assessing the effects of OA across life history stages and demonstrates how transcriptomic plasticity can allow highly resilient organisms, like C. fornicata, acclimate to reduced pH environments.
