Ocean acidification and warming, identified as environmental concerns likely to be affected by climate change, are crucial determinants of algal growth. The ichthyotoxic raphidophytes Chattonella species are responsible for huge economic losses and environmental impact worldwide. In this study, we investigated the impact of CO2 on the thermal performance curves (TPCs) of Chattonella marina and Chattonella ovata grown under temperatures ranging from 13 to 34°C under ambient pCO2 (350 μatm) and elevated pCO2 (950 μatm). TPCs were comparable between the species or even between pCO2 levels. With the exception of the critical thermal minimum (CTmin) for C. ovata, CTmin for C. marina and the thermal optimum (Topt) and critical thermal maximum (CTmax) for both species did not change with elevation of pCO2 levels. While CO2 enrichment increased the maximum photosynthetic rates (Pmax) up to 125% at the Topt of 30°C, specific growth rates were not significantly different under elevated pCO2 for the two species. Overall, C. ovata is likely to benefit from climate change, potentially widening its range of thermal tolerance limit in highly acidic waters and contributing to prolonged phenology of future phytoplankton assemblages in coastal waters.
Continue reading ‘Effect of elevated pCO2 on thermal performance of Chattonella marina and Chattonella ovata (Raphidophyceae)’Posts Tagged 'laboratory'
Effect of elevated pCO2 on thermal performance of Chattonella marina and Chattonella ovata (Raphidophyceae)
Published 30 December 2020 Science ClosedTags: biological response, growth, laboratory, multiple factors, photosynthesis, phytoplankton, reproduction, temperature
Responses of branching reef corals Acropora digitifera and Montipora digitata to elevated temperature and pCO2
Published 30 December 2020 Science ClosedTags: abundance, biological response, calcification, corals, laboratory, molecular biology, morphology, North Pacific, otherprocess, photosynthesis, protists
Anthropogenic emission of CO2 into the atmosphere has been increasing exponentially, causing ocean acidification (OA) and ocean warming (OW). The “business-as-usual” scenario predicts that the atmospheric concentration of CO2 may exceed 1,000 µatm and seawater temperature may increase by up to 3 °C by the end of the 21st century. Increases in OA and OW may negatively affect the growth and survival of reef corals. In the present study, we separately examined the effects of OW and OA on the corals Acropora digitifera and Montipora digitata, which are dominant coral species occurring along the Ryukyu Archipelago, Japan, at three temperatures (28 °C, 30 °C, and 32 °C) and following four pCO2 treatments (400, 600, 800, and 1,000 µatm) in aquarium experiments. In the OW experiment, the calcification rate (p = 0.02), endosymbiont density, and maximum photosynthetic efficiency (Fv/Fm) (both p < 0.0001) decreased significantly at the highest temperature (32 °C) compared to those at the lower temperatures (28 °C and 30 °C) in both species. In the OA experiment, the calcification rate decreased significantly as pCO2 increased (p < 0.0001), whereas endosymbiont density, chlorophyll content, and Fv/Fm were not affected. The calcification rate of A. digitifera showed greater decreases from 30 °C to 32 °C than that of M. digitata. The calcification of the two species responded differently to OW and OA. These results suggest that A. digitifera is more sensitive to OW than M. digitata, whereas M. digitata is more sensitive to OA. Thus, differences in the sensitivity of the two coral species to OW and OA might be attributed to differences in the endosymbiont species and high calcification rates, respectively.
Continue reading ‘Responses of branching reef corals Acropora digitifera and Montipora digitata to elevated temperature and pCO2’Windows of vulnerability: seasonal mismatches in exposure and resource identity determine ocean acidification’s effect on a primary consumer at high latitude
Published 29 December 2020 Science ClosedTags: biological response, chemistry, field, laboratory, mollusks, morphology, multiple factors, North Pacific, nutrients, physiology
It is well understood that differences in the cues used by consumers and their resources in fluctuating environments can give rise to trophic mismatches governing the emergent effects of global change. Trophic mismatches caused by changes in consumer energetics during periods of low resource availability have received far less attention, although this may be common for consumers during winter when primary producers are limited by light. Even less is understood about these dynamics in marine ecosystems, where consumers must cope with energetically costly changes in CO2‐driven carbonate chemistry that will be most pronounced in cold temperatures. This may be especially important for calcified marine herbivores, such as the pinto abalone (Haliotis kamschatkana). H. kamschatkana are of high management concern in the North Pacific due to the active recreational fishery and their importance among traditional cultures, and research suggests they may require more energy to maintain their calcified shells and acid/base balance with ocean acidification. Here we use field surveys to demonstrate seasonal mismatches in the exposure of marine consumers to low pH and algal resource identity during winter in a subpolar, marine ecosystem. We then use these data to test how the effects of exposure to seasonally relevant pH conditions on H. kamschatkana are mediated by seasonal resource identity. We find that exposure to projected future winter pH conditions decreases metabolism and growth, and this effect on growth is pronounced when their diet is limited to the algal species available during winter. Our results suggest that increases in the energetic demands of pinto abalone caused by ocean acidification during winter will be exacerbated by seasonal shifts in their resources. These findings have profound implications for other marine consumers and highlight the importance of considering fluctuations in exposure and resources when inferring the emergent effects of global change.
Continue reading ‘Windows of vulnerability: seasonal mismatches in exposure and resource identity determine ocean acidification’s effect on a primary consumer at high latitude’Environmental changes affecting physiological responses and growth of hybrid grouper – the interactive impact of low pH and temperature
Published 28 December 2020 Science ClosedTags: biological response, fish, laboratory, morphology, multiple factors, physiology, respiration, temperature
Highlights
- Effects of warm temperature and/or low water pH were studied.
- Growth performance were negatively impacted.to either warm temperature or low pH exposure.
- Interactive exposure of warm temperature and low water pH induced high living cost of hybrid grouper.
- Hybrid grouper adjusted energy metabolism needs to cope with the changing environment.
Abstract
Rising of temperature in conjunction with acidification due to the anthropogenic climates has tremendously affected all aquatic life. Small changes in the surrounding environment could lead to physiological constraint in the individual. Therefore, this study was designed to investigate the effects of warm water temperature (32 oC) and low pH (pH 6) on physiological responses and growth of hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) juveniles for 25 days. Growth performance was significantly affected under warm water temperature and low-pH conditions. Surprisingly, the positive effect on growth was observed under the interactive effects of warm water and low pH exposure. Hybrid grouper exposed to the interactive stressor of warm temperature and low pH exhibited higher living cost, where HSI content was greatly depleted to about 2.3-folds than in normal circumstances. Overall, challenge to warm temperature and low pH induced protein mobilization as an energy source followed by glycogen and lipid to support basal metabolic needs.
Continue reading ‘Environmental changes affecting physiological responses and growth of hybrid grouper – the interactive impact of low pH and temperature’Futureproofing the green-lipped mussel aquaculture industry against ocean acidification
Published 25 December 2020 Newsletters and reports , Science ClosedTags: biogeochemistry, biological response, chemistry, dissolution, field, laboratory, mitigation, mollusks, review, South Pacific
Two mitigation strategies – waste shell and aeration – were tested in field experiments to see how effective they are at mitigating acidification around mussel farms. This report outlines the results and recommendations from this research.
Primary results:
- The inner Firth of Thames currently experiences the lowest seasonal pH of the sites monitored, with a daily minimum of 7.84 (7.79–7.96) in autumn, with short-term (15-minute) pH minima as low as 7.2. Time-series data in the inner and outer Firth of Thames, and also on a mussel farm in the western Firth, show episodic declines in carbonate saturation to the critical carbonate saturation state ΩAR = 1.0 at which solid aragonite (the form of carbonate in mussel shells) will start to dissolve. Consequently, mussels in the Firth of Thames experience episodic corrosive conditions.
- The mean pH in the Marlborough Sounds region is projected to decrease by 0.15–0.4 by 2100 depending on future emission scenario. The corresponding decline of 0.5–1.25 in the saturation state of aragonite (ΩAR), results in the critical threshold of ΩAR =1 being reached by 2100 under the worst-case scenario. These projections are based only on future CO2 emission scenarios and do not consider other coastal sources of acidity in coastal waters which may also alter in the future.
Integrated RNA-seq and proteomic studies reveal resource reallocation towards energy metabolism and defense in Skeletonema marinoi in response to CO2 increase
Published 25 December 2020 Science ClosedTags: adaptation, biological response, growth, laboratory, molecular biology, otherprocess, physiology, phytoplankton
Rising atmospheric CO2 concentrations are causing ocean acidification (OA) with significant consequences for marine organisms. Because CO2 is essential for photosynthesis, the effect of elevated CO2 on phytoplankton is more complex and the mechanism is poorly understood. Here we applied RNA-seq and iTRAQ proteomics to investigate the impacts of CO2 increase (from ∼400 to 1000 ppm) on the temperate coastal marine diatom Skeletonema marinoi. We identified 32,389 differentially expressed genes (DEGs) and 1,826 differentially expressed proteins (DEPs) from elevated CO2 conditions, accounting for 48.5% of total genes and 25.9% of total proteins we detected, respectively. Elevated pCO2 significantly inhibited the growth of S. marinoi, and the ‘omic’ data suggested that this might be due to compromised photosynthesis in the chloroplast and raised mitochondrial energy metabolism. Furthermore, many genes/proteins associated with nitrogen metabolism, transcriptional regulation, and translational regulation were markedly up-regulated, suggesting enhanced protein synthesis. In addition, S. marinoi exhibited higher capacity of ROS production and resistance to oxidative stress. Overall, elevated pCO2 seems to repress photosynthesis and growth of S. marinoi, and through massive gene expression reconfiguration induce cells to increase investment in protein synthesis, energy metabolism and antioxidative stress defense, likely to maintain pH homeostasis and population survival. This survival strategy may deprive this usually dominant diatom in temperate coastal waters of its competitive advantages in acidified environments.
Continue reading ‘Integrated RNA-seq and proteomic studies reveal resource reallocation towards energy metabolism and defense in Skeletonema marinoi in response to CO2 increase’Neuronal effects of ocean acidification in gilthead seabream (Sparus aurata)
Published 24 December 2020 Science ClosedTags: biological response, fish, laboratory, morphology, North Atlantic, performance, physiology
As atmospheric CO2 increases, so does the amount of CO2 dissolved in the ocean; this causes ocean acidification. The impact of ocean acidification on marine biodiversity and ecosystems has received considerable attention; however, study of its effects on fish physiology and behaviour is just beginning. Although there is evidence that the atmospheric CO2 concentrations predicted to occur by the end of this century have mal-adaptive effects on olfactory-mediated behaviour of reef fish, the cellular mechanism(s) involved is unclear. In the current study, we recorded the olfactory responses of gilthead seabream (Sparus aurata) to explore the effects of high pCO2 and low pH – separately – on olfactory sensitivity. Exposure to elevated pCO2 (but at normal pH) significantly decreased olfactory sensitivity to some odorants, such as L-serine, L-leucine and L-arginine. Moreover, low pH (but at normal pCO2) also decreased olfactory sensitivity to L-serine, L-leucine and L-arginine and L-glutamine. At the histological level, medium-term exposure to ocean acidificaiton increased the ratio between non-sensory epithelium/total length of the lamella significantly at one week, three weeks and four weeks. Furthermore, the number of mucous cells increased significantly after four weeks of exposure to high pCO2 water. These structural changes suggest that the olfactory epithelium can respond to the changes in low pH and/or high CO2 levels, but cannot fully counteract the effects of acidification on olfactory sensitivity. Together, these results show that both high pCO2 and low pH can independently reduce olfactory sensitivity in marine fish, and that although acidification can evoke structural changes in the olfactory epithelium, these changes cannot fully restore olfactory sensitivity.
Continue reading ‘Neuronal effects of ocean acidification in gilthead seabream (Sparus aurata)’Growth response of calcifying marine epibionts to biogenic pH fluctuations and global ocean acidification scenarios
Published 23 December 2020 Science ClosedTags: algae, Baltic, biological response, bryozoa, crustaceans, laboratory, morphology, multiple factors, substrate, temperature
In coastal marine environments, physical and biological forces can cause dynamic pH fluctuations from microscale (diffusive boundary layer [DBL]) up to ecosystem‐scale (benthic boundary layer [BBL]). In the face of ocean acidification (OA), such natural pH variations may modulate an organism’s response to OA by providing temporal refugia. We investigated the effect of pH fluctuations, generated by the brown alga Fucus serratus‘ biological activity, on the calcifying epibionts Balanus improvisus and Electra pilosa under OA. For this, both epibionts were grown on inactive and biologically active surfaces and exposed to (1) constant pH scenarios under ambient (pH 8.1) or OA conditions (pH 7.7), or (2) oscillating pH scenarios mimicking BBL conditions at ambient (pH 7.7–8.6) or OA scenarios (pH 7.4–8.2). Furthermore, all treatment combinations were tested at 10°C and 15°C. Against our expectations, OA treatments did not affect epibiont growth under constant or fluctuating (BBL) pH conditions, indicating rather high robustness against predicted OA scenarios. Furthermore, epibiont growth was hampered and not fostered on active surfaces (fluctuating DBL conditions), indicating that fluctuating pH conditions of the DBL with elevated daytime pH do not necessarily provide temporal refugia from OA. In contrast, results indicate that factors other than pH may play larger roles for epibiont growth on macrophytes (e.g., surface characteristics, macrophyte antifouling defense, or dynamics of oxygen and nutrient concentrations). Warming enhanced epibiont growth rates significantly, independently of OA, indicating no synergistic effects of pH treatments and temperature within their natural temperature range.
Continue reading ‘Growth response of calcifying marine epibionts to biogenic pH fluctuations and global ocean acidification scenarios’Ocean acidification and warming lead to increased growth and altered chloroplast morphology in the thermo-tolerant alga Symbiochlorum hainanensis
Published 18 December 2020 Science ClosedTags: biological response, growth, laboratory, molecular biology, morphology, multiple factors, photosynthesis, physiology, phytoplankton, temperature
Ocean acidification and warming affect the growth and predominance of algae. However, the effects of ocean acidification and warming on the growth and gene transcription of thermo-tolerant algae are poorly understood. Here we determined the effects of elevated temperature (H) and acidification (A) on a recently discovered coral-associated thermo-tolerant alga Symbiochlorum hainanensis by culturing it under two temperature settings (26.0 and 32.0°C) crossed with two pH levels (8.16 and 7.81). The results showed that the growth of S. hainanensis was positively affected by H, A, and the combined treatment (AH). However, no superimposition effect of H and A on the growth of S. hainanensis was observed under AH. The analysis of chlorophyll fluorescence, pigment content, and subcellular morphology indicated that the chloroplast morphogenesis (enlargement) along with the increase of chlorophyll fluorescence and pigment content of S. hainanensis might be a universal mechanism for promoting the growth of S. hainanensis. Transcriptomic profiles revealed the effect of elevated temperature on the response of S. hainanensis to acidification involved in the down-regulation of photosynthesis- and carbohydrate metabolism-related genes but not the up-regulation of genes related to antioxidant and ubiquitination processes. Overall, this study firstly reports the growth, morphology, and molecular response of the thermo-tolerant alga S. hainanensis to future climate changes, suggesting the predominance of S. hainanensis in its associated corals and/or coral reefs in the future.
Continue reading ‘Ocean acidification and warming lead to increased growth and altered chloroplast morphology in the thermo-tolerant alga Symbiochlorum hainanensis’Ocean-related global change alters lipid biomarker production in common marine phytoplankton (update)
Published 17 December 2020 Science ClosedTags: biogeochemistry, biological response, growth, laboratory, multiple factors, nutrients, physiology, phytoplankton, temperature
Lipids, in their function as trophic markers in food webs and organic matter source indicators in the water column and sediments, provide a tool for reconstructing the complexity of global change effects on aquatic ecosystems. It remains unclear how ongoing changes in multiple environmental drivers affect the production of key lipid biomarkers in marine phytoplankton. Here, we tested the responses of sterols, alkenones and fatty acids (FAs) in the diatom Phaeodactylum tricornutum, the cryptophyte Rhodomonas sp. and the haptophyte Emiliania huxleyi under a full-factorial combination of three temperatures (12, 18 and 24 ∘C), three N : P supply ratios (molar ratios 10 : 1, 24 : 1 and 63 : 1) and two pCO2 levels (560 and 2400 µatm) in semicontinuous culturing experiments. Overall, N and P deficiency had a stronger effect on per-cell contents of sterols, alkenones and FAs than warming and enhanced pCO2. Specifically, P deficiency caused an overall increase in biomarker production in most cases, while N deficiency, warming and high pCO2 caused nonsystematic changes. Under future ocean scenarios, we predict an overall decrease in carbon-normalized contents of sterols and polyunsaturated fatty acids (PUFAs) in E. huxleyi and P. tricornutum and a decrease in sterols but an increase in PUFAs in Rhodomonas sp. Variable contents of lipid biomarkers indicate a diverse carbon allocation between marine phytoplankton species in response to changing environments. Thus, it is necessary to consider the changes in key lipids and their consequences for food-web dynamics and biogeochemical cycles, when predicting the influence of global change on marine ecosystems.
Continue reading ‘Ocean-related global change alters lipid biomarker production in common marine phytoplankton (update)’Ocean acidification and ocean warming effects on Pacific Herring (Clupea pallasi) early life stages
Published 17 December 2020 Science ClosedTags: biological response, fish, laboratory, morphology, mortality, multiple factors, North Pacific, physiology, reproduction, temperature
Increasing green house gas emissions are expected to raise surface seawater temperatures and lead to locally intensified ocean acidity in the U.S. Pacific Northwest. Pacific herring (Clupea pallasi) are ecologically and economically important forage fish species native to this region. While the impacts of ocean acidification and ocean warming on organism physiology have been extensively studied, less is known on how concurrent climate change stressors will affect marine fish. Therefore, our study focused on the combined effects of ocean acidification and warming on Pacific herring early life history stages. Pacific herring embryos were incubated under a factorial design of two temperature (10°C or 16°C) and two pCO2 (600 μatm or 1200 μatm) treatments from fertilization until hatch (6 to 15 days depending on temperature). Elevated pCO2 was associated with a small increase in embryo mortality. Elevated temperature, as a single stressor, generated greater embryo mortality and embryo heart rates, larger yolk areas upon hatch, lower hatching success, and shorter larval lengths; compared with the same parameters measured under ambient temperature. The interaction of elevated temperature and pCO2 was associated with greater embryo heart rates and yolk areas compared to ambient conditions. This study suggests that while temperature is the primary global change stressor affecting Pacific herring embryology, interaction effects with pCO2 could introduce additional physiological challenges.
Continue reading ‘Ocean acidification and ocean warming effects on Pacific Herring (Clupea pallasi) early life stages’Physiological responses to temperature and ocean acidification in tropical fleshy macroalgae with varying affinities for inorganic carbon
Published 15 December 2020 Media coverage ClosedTags: algae, biological response, laboratory, mesocosms, morphology, mortality, multiple factors, photosynthesis, physiology, respiration, South Pacific, temperature
Marine macroalgae have variable carbon-uptake strategies that complicate predicting responses to environmental changes. In seawater, dissolved inorganic carbon availability can affect the underlying physiological mechanisms influencing carbon uptake. We tested the interactive effects of ocean acidification (OA) and warming on two HCO−3HCO3−-users (Lobophora sp. and Amansia rhodantha), a predominately CO2-user (Avrainvillea nigricans), and a sole CO2-user (Plocamium hamatum) in the Great Barrier Reef, Australia. We examined metabolic rates, growth, and carbon isotope values (δ13C) in algae at 26, 28, or 30°C under ambient or elevated pCO2 (∼1000 µatm). Under OA, δ13C values for the HCO−3HCO3−-users decreased, indicating less reliance on HCO−3HCO3−, while δ13C values for CO2-users were unaffected. Both HCO−3HCO3−-users decreased in growth across temperatures under ambient pCO2, but this negative effect was alleviated by OA at 30°C. A. nigricans lost biomass across all treatments and P. hamatum was most sensitive, with reduced survival in all physiological responses. Metabolic rates varied greatly to interacting temperature and OA and indicated a decoupling between the relationship of photosynthesis and growth. Furthermore, our findings suggest HCO−3HCO3−-users are more responsive to future CO2 changes, and highlight examining carbon physiology to infer potential responses to interacting environmental stressors.
Continue reading ‘Physiological responses to temperature and ocean acidification in tropical fleshy macroalgae with varying affinities for inorganic carbon’The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic sea
Published 14 December 2020 Science ClosedTags: abundance, biological response, BRcommunity, cnidaria, community composition, laboratory, Mediterranean, molecular biology, otherprocess, prokaryotes, respiration, sediment
Over the past several decades, jellyfish blooms have intensified spatially and temporally, affecting functions and services of ecosystems worldwide. At the demise of a bloom, an enormous amount of jellyfish biomass sinks to the seabed and decomposes. This process entails reciprocal microbial and biogeochemical changes, typically enriching the water column and seabed with large amounts of organic and inorganic nutrients. Jellyfish decomposition was hypothesized to be particularly important in nutrient-impoverished ecosystems, such as the Eastern Mediterranean Sea – one of the most oligotrophic marine regions in the world. Since the 1970s, this region has been experiencing the proliferation of a notorious invasive scyphozoan jellyfish, Rhopilema nomadica. In this study, we estimated the short-term decomposition effects of R. nomadica on nutrient dynamics at the sediment-water interface. Our results show that the degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production. These conditions favored heterotrophic microbial activity and bacterial biomass accumulation, and triggered a shift towards heterotrophic biodegrading bacterial communities, whereas autotrophic picophytoplankton abundance was moderately affected or reduced. This shift may further decrease primary production in the water column of the Eastern Mediterranean Sea. Deoxygenation, acidification, nutrient enrichment, and microbial community shifts at the sediment-water interface may have a detrimental impact on macrobenthic communities. Based on these findings, we suggest that jelly-falls and their decay may facilitate an additional decline in ecosystem functions and services.
Continue reading ‘The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic sea’Influence of ocean acidification on thermal reaction norms of carbon metabolism in the marine diatom Phaeodactylum tricornutum
Published 11 December 2020 Science ClosedTags: biological response, laboratory, multiple factors, photosynthesis, phytoplankton, respiration, temperature
Highlights
- The R/P of Phaeodactylum tricornutum increased with temperature in the suboptimal temperature range.
- In the supraoptimal temperature range, R/P decreased with temperature.
- The HC to LC ratio of R/P gradually increased with temperature in the supraoptimal temperature range.
Abstract
Under the present CO2 condition, the efficiency of biological pump mediating carbon sequestration is predicted to decline in the future because respiration tends to be more sensitive to rising temperature than is photosynthesis. However, it remains unknown whether the impacts of global warming on metabolic rates of phytoplankton can be modulated by elevated CO2 induced ocean acidification. Here we show that in the model diatom species Phaeodactylum tricornutum, Ea (activation energy) of photosynthesis (~0.5 eV) was significantly lower than that of respiration (1.8 eV), while CO2 concentration had no effect on the Ea value. Eh (deactivation energy) of respiration was increased to 2.5 eV, that was equivalent to Eh of photosynthesis in high CO2-grown cells and 28.4% higher than that in low CO2-grown ones. The respiration to photosynthesis ratio (R/P) was consistently higher in high CO2 condition, which increased with temperature at the beginning and subsequently decreased in both CO2 conditions. The ratio of R/P in high CO2 to R/P in low CO2 gradually increased with temperature above the optimal temperature. Our results imply that ocean acidification will aggravate the negative impacts or offset the alleviating effects of warming on the R/P ratio depending on the temperature range in Phaeodactylum tricornutum.
Magnitude and predictability of pH fluctuations shape plastic responses to ocean acidification
Published 10 December 2020 Science ClosedTags: adaptation, biological response, chemistry, field, laboratory, Mediterranean, molecular biology, mollusks, otherprocess, performance, physiology
Phenotypic plasticity is expected to facilitate the persistence of natural populations as global change progresses. The attributes of fluctuating environments that favor the evolution of plasticity have received extensive theoretical investigation, yet empirical validation of these findings is still in its infancy. Here, we combine high-resolution environmental data with a laboratory-based experiment to explore the influence of habitat pH fluctuation dynamics on the plasticity of gene expression in two populations of the Mediterranean mussel, Mytilus galloprovincialis. We linked differences in the magnitude and predictability of pH fluctuations in two habitats to population-specific gene expression profiles in ambient and stressful pH treatments. Our results demonstrate population-based differentiation in gene expression plasticity, whereby mussels native to a habitat exhibiting a large magnitude of pH fluctuations with low predictability display reduced phenotypic plasticity between experimentally imposed pH treatments. This work validates recent theoretical findings on evolution in fluctuating environments, suggesting that the predictability of fluctuating selection pressures may play a predominant role in shaping the phenotypic variation observed across natural populations.
Continue reading ‘Magnitude and predictability of pH fluctuations shape plastic responses to ocean acidification’Multi-stressor extremes found on a tropical coral reef impair performance
Published 10 December 2020 Science ClosedTags: adaptation, biological response, chemistry, echinoderms, field, laboratory, multiple factors, North Atlantic, otherprocess, oxygen, performance, temperature
Global change has resulted in oceans that are warmer, more acidic, and lower in oxygen. Individually any one of these stressors can have numerous negative impacts on marine organisms, and in combination they are likely to be particularly detrimental. Understanding the interactions between these factors is important as they often covary, with warming promoting hypoxia, and hypoxia co-occurring with acidification. Few studies have examined how all three factors interact to affect organismal performance, and information is particularly sparse for tropical organisms. Here we documented a strong relationship between high temperatures, low dissolved oxygen (DO), and low pH in and around a tropical bay. We used these field values to inform two multi-stressor experiments. Each experimental factor had two levels, one representing current average conditions and the other representing current extreme conditions experienced in the area. We used sea urchin righting response as a measure of organismal performance for an important reef herbivore. In the first experiment 2-h exposures to a fully factorial combination of temperature, DO, and pH showed that righting success was significantly depressed under low oxygen. To more fully understand the impacts of pH, we acclimated sea urchins to control and low pH for 7 days and subsequently exposed them to the same experimental conditions. Sea urchins acclimated to control pH had significantly reduced righting success compared to animals acclimated to low pH, and righting success was significantly depressed under hypoxia and high temperature, compared to normoxia and ambient temperature. These results show that short, 2 h exposures to the temperature and DO extremes that are already experienced periodically by these animals have measurable detrimental effects on their performance. The positive impact of reduced pH is evident only over longer, 7 days durations, which are not currently experienced in this area.
Continue reading ‘Multi-stressor extremes found on a tropical coral reef impair performance’Climate change doubles sedimentation-induced coral recruit mortality
Published 8 December 2020 Science ClosedTags: biological response, corals, laboratory, morphology, mortality, multiple factors, reproduction, South Pacific, temperature
Highlights
- Recruits grown under future climate are twice as sensitive to sediment deposition
- Older recruits survived higher sediment depositions events
- Only recruits grown in current climate survived the highest realistic sedimentation
Abstract
Coral reef replenishment is threatened by global climate change and local water-quality degradation, including smothering of coral recruits by sediments generated by anthropogenic activities. Here we show that the ability of Acropora millepora recruits to remove sediments diminishes under future climate conditions, leading to increased mortality. Recruits raised under future climate scenarios for fourteen weeks (highest treatment: +1.2 °C, pCO2: 950 ppm) showed twofold higher mortality following repeated sediment deposition (50% lethal sediment concentration LC50: 14 – 24 mg cm-2) compared to recruits raised under current climate conditions (LC50: 37 – 51 mg cm-2), depending on recruit age at the time of sedimentation. Older and larger recruits were more resistant to sedimentation and only ten-week-old recruits grown under current climate conditions survived sediment loads typical of dredging operations. This demonstrates that water-quality guidelines for managing sediment concentrations will need to be climate-adjusted to protect future coral recruitment.
Long-term environmental tolerance of the non-indigenous Pacific oyster to expected contemporary climate change conditions
Published 7 December 2020 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, physiology, respiration, salinity, temperature
Highlights
- Long-term effects of climate change on non-indigenous species are rarely studied
- Pacific oysters were exposed to warming, ocean acidification and reduced salinity
- Warming and ocean acidification predicted for the year 2100 did not affect fitness
- Low salinity reduced clearance rates and increased oxygen consumption rates
- Long-term observations highlighted potential seasonal trends in physiological rates
Abstract
The current global redistribution of biota is often attributed to two main drivers: contemporary climate change (CCC) and non-indigenous species (NIS). Despite evidence of synergetic effects, however, studies assessing long-term effects of CCC conditions on NIS fitness remain rare. We examined the interactive effects of warming, ocean acidification and reduced salinity on the globally distributed marine NIS Magallana gigas(Pacific oyster) over a ten-month period. Growth, clearance and oxygen consumption rates were measured monthly to assess individual fitness. Lower salinity had a significant, permanent effect on M. gigas, reducing and increasing clearance and oxygen consumption rates, respectively. Neither predicted increases in seawater temperature nor reduced pH had a long-term physiological effect, indicating conditions predicted for 2100 will not affect adult physiology and survival. These results suggest that M. gigas will remain a globally successful NIS and predicted CCC will continue to facilitate their competitive dominance in the near future.
Continue reading ‘Long-term environmental tolerance of the non-indigenous Pacific oyster to expected contemporary climate change conditions’Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol
Published 7 December 2020 Science ClosedTags: algae, biological response, laboratory, multiple factors, otherprocess, photosynthesis, physiology, South Atlantic, toxicants
Highlights
- Photosynthetic yield is affected by low pH in assays with and without Irgarol.
- Membrane damage and antioxidant activities increased in low pH added to Irgarol.
- H2O2 content and lipid peroxidation were not affected by low pH isolated.
- U.lactuca is tolerant to low pH by triggering photoprotector mechanisms.
- Protective mechanisms could not avoid the simultaneous effects of low pH and Irgarol.
Abstract
Anthropogenic changes such as ocean acidification, eutrophication, and the release of hazardous chemicals affect coastal environments and aquatic organisms. We investigated the effects of seawater pH (7.4 and 8.2) isolated and in combination with Irgarol on Ulva lactuca. Stress indicators such as membrane damage, lipid peroxidation, and hydrogen peroxide content were assessed. In addition, chlorophyll fluorescence and antioxidant enzyme activities were measured. The photosynthetic yield was affected by low pH in assays with and without Irgarol. However, the combination of low pH and Irgarol promoted photoinhibition, besides the induction of non-photochemical quenching (NPQ) and changes in photosynthetic pigment contents. The induction of NPQ was directly influenced by low pH. The membrane damage was increased in low pH with and without Irgarol exposure. Total soluble protein and carbohydrate contents decreased in low pH, and in presence of Irgarol. The H2O2 content and lipid peroxidation were not affected by low pH. In contrast, Irgarol exposure strongly increased lipid peroxidation in both pHs, suggesting a possible synergistic effect. To avoid the harmful effects of high H2O2, U. lactuca increased antioxidant enzyme activities in treatments under low pH and in presence of Irgarol. Our results indicate that U. lactuca is tolerant to low pH by inducing NPQ, changing pigment contents, and increasing antioxidant defenses. In contrast, these protective mechanisms could not avoid the harmful effects of the combination with Irgarol.
Continue reading ‘Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol’
