Posts Tagged 'multiple factors'

Juvenile Dungeness crab foraging behavior and lipid composition is altered more by food quantity than seawater pH in a multi-stressor experiment

Published 29 March 2023 Science Leave a Comment
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Highlights

  • We fed juvenile crab a maintenance- or low-quantity diet at ambient or reduced pH.
  • Foraging behaviors changed depending on diet and pH exposure but pH sensing did not.
  • Crab fatty acid composition was altered due to diet and pH exposure.
  • Crab lipid and fatty acid concentrations did not change due to pH exposure.
  • Crab in regions with pH and food supply variability may be resilient to reduced pH.

Abstract

Increases in atmospheric, anthropogenic carbon are driving reductions in seawater pH, a process referred to as ocean acidification. Reduced seawater pH can influence behavior of marine animals, but little is currently known about how juvenile crustaceans will respond. We conducted lab experiments to improve our understanding of the consequences of pH exposure and food quantity on juvenile Dungeness crab (Metacarcinus magister, (Dana, 1852)) behavior and nutritional condition. To understand the foraging and pH sensing behavior of juvenile crab, and how this interacts with their nutritional status, we exposed recently settled second instar juveniles to either ambient pH or reduced pH for 42-d, crossed with either a ‘maintenance’- or low-quantity ‘challenge’ diet treatment. After the experimental exposure period, we introduced crab into foraging and sensing pH behavior experiments. In the foraging experiment, we placed crab in a behavior arena with unidirectional flow, where we measured the food discovery time and time allocation of activities in 300-s trials for all individual crab. Food quantity and pH exposure influenced both the speed with which juvenile crab identified and allocation of activities but there was no interactive effect of experimental factors. For our pH sensing experiment, we used a two-current flume plumbed with both ambient and reduced pH seawater. This flow-through flume provided a choice between the pH treatment waters and allowed us to measure the amount of time individuals spent on either side of the arena in 300-s trials. There was no effect of prior diet or pH exposure on the amount of time juvenile crab spent in either seawater pH condition. In addition to the behavior trials, we evaluated crab nutritional condition by quantifying the total lipid content of whole-body tissues and fatty acid profile composition of juvenile crab fed either the maintenance or low-quantity diet during the experimental pH exposure period. The proportional fatty acid profiles differed for crab based on their diet and pH exposure, with no interactive effects. However, we did not detect differences in the concentrations of key summary categories of fatty acids (e.g., saturated, monounsaturated, or polyunsaturated) based on pH exposure. Our results indicate that reduced food availability has a greater impact on juvenile Dungeness crab foraging behavior and nutritional condition than reduced seawater pH exposure representing the 0.3 pH unit decrease predicted by 2100.

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Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818)

Published 29 March 2023 Science Leave a Comment
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Highlights

  • Cu and OA coexposures induce tissue-specific oxidative stress in clams.
  • OA exacerbates Cu toxicity and increases oxidative damage in tissues.
  • Gill is more vulnerable to oxidation than viscera with MDA and 8-OHdG as indicators.
  • PCAs usefully identify the contributions of biomarkers to antioxidant defences.
  • The results provide insights for assessing Cu toxicity under OA in wild bivalves.

Abstract

Toxicity of contaminants in organisms under ocean acidification (OA) has attracted increasing attention in ecotoxicological studies. This study investigated how pCO2-driven OA affected waterborne copper (Cu) toxicity in antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818). Clams were continuously exposed to Cu at ambient relevant (0/no metal exposure, 10 and 50 μg L−1) and polluted-high (100 μg L−1) concentrations in unacidified (pH 8.10) and acidified (pH 7.70/moderate OA and 7.30/extreme OA) seawater for 21 days. Following coexposure, metal bioaccumulation and responses of antioxidant defence-related biomarkers to OA and Cu coexposure were investigated. Results showed that metal bioaccumulation was positively correlated with waterborne metal concentrations but was not notably influenced by OA conditions. Both Cu and OA affected the antioxidant responses to environmental stress. Additionally, OA induced tissue-specific interactions with Cu on antioxidant defences, varying with exposure conditions. In unacidified seawater, antioxidant biomarkers were activated to defend against oxidative stress induced by Cu and prevented clams from lipid peroxidation (LPO or MDA), but failed to defend against DNA damage (8-OHdG). OA exacerbated Cu toxicity in antioxidant defences and increased LPO levels in tissues. Gills and viscera adopted adaptive antioxidant defence strategies to manage oxidative stress, with the former being more vulnerable to oxidative stress than the latter. MDA and 8-OHdG were sensitive to OA and Cu exposure, respectively, and were useful bioindicators for assessing oxidative stress. Integrated biomarker response (IBR) and PCA can reflect the integrative responses of antioxidant biomarkers to environmental stress and illuminate the contributions of specific biomarkers to antioxidant defence strategies. The findings provided insights for understanding antioxidant defences against metal toxicity in marine bivalves under OA scenarios, which is essential into managing wild populations.

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The clam before the storm: a meta analysis showing the effect of combined climate change stressors on bivalves

Published 28 March 2023 Science Leave a Comment
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Impacts of a range of climate change on marine organisms have been analysed in laboratory and experimental studies. The use of different taxonomic groupings, and assessment of different processes, though, makes identifying overall trends challenging, and may mask phylogenetically different responses. Bivalve molluscs are an ecologically and economically important data-rich clade, allowing for assessment of individual vulnerability and across developmental stages. We use meta-analysis of 203 unique experimental setups to examine how bivalve growth rates respond to increased water temperature, acidity, deoxygenation, changes to salinity, and combinations of these drivers. Results show that anthropogenic climate change will affect different families of bivalves disproportionally but almost unanimously negatively. Almost all drivers and their combinations have significant negative effects on growth. Combined deoxygenation, acidification, and temperature shows the largest negative effect size. Eggs/larval bivalves are more vulnerable overall than either juveniles or adults. Infaunal taxa, including Tellinidae and Veneridae, appear more resistant to warming and oxygen reduction than epifaunal or free-swimming taxa but this assessment is based on a small number of datapoints. The current focus of experimental set-ups on commercially important taxa and families within a small range of habitats creates gaps in understanding of global impacts on these economically important foundation organisms.

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The influence of ocean acidification and warming on responses of Scylla serrata to oil pollution: an integrated biomarker approach

Published 28 March 2023 Science Leave a Comment
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Graphical abstract

Highlights

  • The OAW conditions reduce tolerance capacity of crabs to acute pollution stress.
  • A greater degree of stress was experienced in oil exposure under OAW conditions.
  • Augmented antioxidant and detoxification enzyme activity was noted.

Abstract

Anthropogenic activities primarily combustion of fossil fuel is the prime cause behind the increased concentration of CO2 into the atmosphere. As a consequence, marine environments are anticipated to experience shift towards lower pH and elevated temperatures. Moreover, since the industrial revolution the growing demand for petroleum-based products has been mounting up worldwide leading to severe oil pollution. Sundarbans estuarine system (SES) is experiencing ocean warming, acidification as well as oil pollution from the last couple of decades. Scylla serrata is one of the most commercially significant species for aquaculture in coastal areas of Sundarbans. Thus, the prime objective of this study is to delineate whether exposure under ocean warming and acidification exacerbates effect of oil spill on oxidative stress of an estuarine crab S. serrata. Animals were separately exposed under current and projected climate change scenario for 30 days. After this half animals of each treatment were exposed to oil spill conditions for 24 h. Oxidative stress status superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), lipid peroxidation (LPO level) and DNA damage (Comet assay) were measured. Augmented antioxidant and detoxification enzyme activity was noted except for SOD but failed to counteract LPO and DNA damage. The present results clearly highlighted the detrimental combined effect of OWA and pollution on oxidative stress status of crabs that might potentially reduce its population and affect the coastal aquaculture in impending years.

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Effects of ocean acidification and warming on the specific dynamic action of California Grunion (Leuresthes tenuis) larvae

Published 27 March 2023 Science Leave a Comment
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Highlights

  • SDA was measured as the difference in metabolic rate of fed and non-fed fish.
  • SDA is ∼15% of the daily metabolic energy costs for California Grunion larvae.
  • OA conditions shifted the SDA response earlier.
  • Changes in SDA with climate can have downstream effects on larval growth.

Abstract

Ocean acidification (OA) and Ocean Warming (OW) are ongoing environmental changes that present a suite of physiological challenges to marine organisms. Larval stages may be especially sensitive to the effects of climate change because the larval phase is a time of critical growth and development. Of particular importance to growth is Specific Dynamic Action (SDA) – the energy used in digestion, absorption, and assimilation of food. Relatively little is known about the energetics of SDA for larval fishes and even less is known about how SDA may be affected by climate change. In this study we used feeding experiments and respirometry assays to characterize the functional form of SDA for California Grunion (Leuresthes tenuis). In a second set of experiments, we tested the independent and combined effects of ocean acidification and warming on SDA. Our first experiment revealed that an elevated metabolic rate was detectable within an hour of feeding, peaked at 3–6 h post feeding, and lasted about 24 h in total. Experiments testing the effects of acidification and warming revealed that temperature generally increased the maximum rate of postprandial respiration and the total amount of energy expended via SDA. In an experiment where feeding level was the same for fish held at different temperatures, elevated pCO2 increased the maximum rate of postprandial respiration and shortened the SDA response. However, in an experiment that allowed fish to consume more food at high temperatures, effects of pCO2 on SDA were minimal. The effects of OA on SDA may depend on a combination of temperature and food availability, and the disruption of SDA with OA may be part of a chain of events where digestion and assimilation efficiency are impaired with potential consequences for growth, survival, and population replenishment.

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Sensitivity of fishery resources to climate change in the warm-temperate Southwest Atlantic Ocean

Published 24 March 2023 Science Leave a Comment
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Climate change impacts on fishery resources have been widely reported worldwide. Nevertheless, a knowledge gap remains for the warm-temperate Southwest Atlantic Ocean—a global warming hotspot that sustains important industrial and small-scale fisheries. By combining a trait-based framework and long-term landing records, we assessed species’ sensitivity to climate change and potential changes in the distribution of important fishery resources (n = 28; i.e., bony fishes, chondrichthyans, crustaceans, and mollusks) in Southern Brazil, Uruguay, and the northern shelf of Argentina. Most species showed moderate or high sensitivity, with mollusks (e.g., sedentary bivalves and snails) being the group with the highest sensitivity, followed by chondrichthyans. Bony fishes showed low and moderate sensitivities, while crustacean sensitivities were species-specific. The stock and/or conservation status overall contributed the most to higher sensitivity. Between 1989 and 2019, species with low and moderate sensitivity dominated regional landings, regardless of the jurisdiction analyzed. A considerable fraction of these landings consisted of species scoring high or very high on an indicator for potential to change their current distribution. These results suggest that although the bulk of past landings were from relatively climate-resilient species, future catches and even entire benthic fisheries may be jeopardized because (1) some exploited species showed high or very high sensitivities and (2) the increase in the relative representation of landings in species whose distribution may change. This paper provides novel results and insights relevant for fisheries management from a region where the effects of climate change have been overlooked, and which lacks a coordinated governance system for climate-resilient fisheries.

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Swimming performance of sharks and rays under climate change

Published 21 March 2023 Science Leave a Comment
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Climate change stressors (e.g., warming and ocean acidification) are an imminent challenge to the physiological performance of marine organisms. Several studies spanning the last decade have reported widespread effects of warming and acidification on marine fishes, especially teleosts, but more work is needed to elucidate the responses in marine elasmobranchs, i.e., sharks and rays. Dispersal capacity, as a result of locomotor performance, is a crucial trait that will determine which group of elasmobranchs will be more or less vulnerable to changes in the environment. In fact, efficient and high locomotor performance may determine the capacity for elasmobranchs to relocate to a more favorable area. In this review we integrate findings from work on locomotion of marine sharks and rays to identify characteristics that outline potential vulnerabilities and strength of sharks and rays under climate change. Traits such as intraspecific variability in response to climatic stressors, wide geographic range, thermotaxis, fast swimming or low energetic costs of locomotion are likely to enhance the capacity to disperse. Future studies may focus on understanding the interacting effect of climatic stressors on morphology, biomechanics and energetics of steady and unsteady swimming, across ontogeny and species.

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Ocean acidification and warming modify stimulatory benthos effects on sediment functioning: an experimental study on two ecosystem engineers

Published 17 March 2023 Science Leave a Comment
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Many macrofauna have a stimulatory effect on sediment functioning through their burrowing, feeding and irrigation activities. Here, we investigated the single and combined effect of ocean acidification and warming on the stimulatory effect of two key-species inhabiting sandy seabeds in the Southern Bight of the North Sea; the bivalve Abra alba and the polychaete Lanice conchilega. The species were separately incubated in natural sediment in the laboratory under ambient, low pH (pH: -0.3), warm (T: + 3°C) and mimicked climate change (pH: -0.3, T: +3°C) conditions. After six weeks of incubation, nutrient and oxygen exchange were measured at the sediment-water interface to estimate aerobic sediment metabolism and nitrogen cycling. Both species facilitate sediment community oxygen consumption, nitrification and denitrification under ambient conditions. The stimulatory effect of A. alba disappeared in a low pH environment and decreased over time in the warmer treatments along with increased mortality. In contrast, L. conchilega stimulated sediment biogeochemical cycling more when seawater becomes acidified (+ 8 to 41%, depending on the function) but warming had no effect. We explain these species-specific climate change effects by different behavioral and physiological coping strategies that cascade on to sediment biogeochemical cycling, especially through altered oxygenation the sediment matrix.

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Effects of ocean acidification and eutrophication on the growth and photosynthetic performances of a green tide alga Ulva prolifera

Published 17 March 2023 Science Leave a Comment
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With the impact of fossil fuel burning and industrialization, atmospheric CO2 concentration will reach about 1000 ppmv in 2100, and more and more CO2 will be absorbed by ocean, resulting in ocean acidification. The Chinese coastal waters are showing unexpectedly high levels of acidification due to a combination of global ocean acidification and severe regional eutrophication, which is caused by natural accumulation or human activities such as aquacultural tail water input, potentially affecting macroalgal blooms. However, little is known about the combined effects of ocean acidification and entrophication on the eco-physiology of bloom-forming macroalgae. This study investigated Ulva prolifera, a dominant species causing green tide in the South Yellow Sea, and explored its growth and physiological responses under the combination conditions of ocean acidification and enriched nutrients. In this study, U. prolifera thalli were cultured under two CO2 conditions (air and 1000 μatm) and two nutrient conditions (High Nutrient, HN, 135 μmol L-1 N and 8.5 μmol L-1 P; Normal Nutrient, NN, 27 μmol L-1 N and 1.7 μmol L-1 P). The results showed that eutrophication conditions obviously enhanced the relative growth rate and photosynthetic performance of U. prolifera. Elevated pCO2 had no significant effect on U. prolifera growth and photosynthetic performance under normal nutrient conditions. However, under eutrophication conditions elevated pCO2 inhibited U. prolifera growth. Moreover, eutrophication conditions markedly improved the contents of chlorophyll a, chlorophyll b and nitrate reductase activity and inhibited the soluble carbohydrate content, but elevated pCO2 had no significant effect on them under nutrient-replete conditions. In addition, elevated pCO2 significantly reduced the carotenoid content under eutrophication conditions and had no effect on it under normal nutrient conditions. These findings indicate that seawater eutrophication would greatly accelerate U. prolifera bloom, which may also be suppressed to a certain extent by ocean acidification in the future. The study can provide valuable information for predicting the future outbreaks of U. prolifera green tide in nearshore regions.

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Symbiont composition and coral genotype determines massive coral species performance under end-of-century climate scenarios

Published 16 March 2023 Science Leave a Comment
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The recent decline of coral health and substantial loss of coral cover along Florida’s Coral Reef (FCR) results from local stressors such as degraded water quality and disease outbreaks in addition to anthropogenically driven global stressors including ocean warming and acidification. Intervention strategies intended for the restoration of degraded reef habitats need a better understanding of the influence of ocean warming and acidification on coral health to target coral species and individual genotypes that may be more resistant or resilient to such stressors. Here, we examined a suite of physiological traits (coral host and algal symbiont) in response to experimentally elevated water temperatures and pCO2 levels, both separately and in concert, using threatened reef-building corals Pseudodiploria clivosa and Orbicella faveolata reared within a land-based coral nursery. After two months of exposure, responses differed by coral species, where P. clivosa showed declined physiology in response to combined ocean warming and acidification stress and ocean warming alone, whereas O. faveolata showed a positive response under ocean acidification. Responses to temperature could be associated with the algal symbionts harbored, as P. clivosa was dominated by the thermally sensitive Breviolum, and O. faveolata was dominated by the thermally tolerant Durusdinium. Additionally, corals were raised in well-sourced seawater that was naturally high in pCO2, which could have led to corals acclimating to acidified conditions. Of the three P. clivosa genets tested, we determined a top-performing genotype under the combined warming and acidification treatment. O. faveolata, however, displayed high genet variation by treatment and phenotypic trait, making genotype performance rankings challenging to discern. The evidence provided in this study demonstrates that high phenotypic variation in nursery-reared corals contributes to variable warming-acidification responses, suggesting that high-standing genetic variation in nursery-reared corals could support diverse coral restoration population outcomes along FCR.

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Nanoplastics induce epigenetic signatures of transgenerational impairments associated with reproduction in copepods under ocean acidification

Published 15 March 2023 Science Closed
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Graphical abstract

Ocean acidification (OA) is one of many major global climate changes that pose a variety of risks to marine ecosystems in different ways. Meanwhile, there is growing concern about how nanoplastics (NPs) affect marine ecosystems. Combined exposure of marine organisms to OA and NPs is inevitable, but their interactive effects remain poorly understood. In this study, we investigated the multi- and transgenerational toxicity of NPs on copepods under OA conditions for ten generations. The findings revealed that OA and NPs have a synergistic negative effect on copepod reproduction across generations. In particular, the transgenerational groups showed reproductive impairments in the F1 and F2 generations (F1T and F2T), even though they were never exposed to NPs. Moreover, our epigenetic examinations demonstrated that the observed intergenerational reproductive impairments are associated with differential methylation patterns of specific genes, suggesting that the interaction of OA and NPs can pose a significant threat to the sustainability of copepod populations through epigenetic modifications. Overall, our findings provide valuable insight into the intergenerational toxicity and underlying molecular mechanisms of responses to NPs under OA conditions.

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Ocean acidification, warming and feeding impacts on biomineralization pathways and shell material properties of Magallana gigas and Mytilus spp.

Published 13 March 2023 Science Closed
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Highlights

  • Mytilus spp. source environmental carbon into the shell aragonite under low pH.
  • In Mytilus spp. biomineralization pathways differ between calcite and aragonite.
  • M. gigas carbon sourcing remains similar maintaining calcite growth.
  • M. gigas mantle δ15N is lower in low pH reflecting algae nitrogen uptake.
  • Calcite biomineralization pathway differs between the two species under low pH.

Abstract

Molluscs are among the organisms affected by ocean acidification (OA), relying on carbon for shell biomineralization. Metabolic and environmental sourcing are two pathways potentially affected by OA, but the circumstances and patterns by which they are altered are poorly understood. From previous studies, mollusc shells grown under OA appear smaller in size, brittle and thinner, suggesting an important alteration in carbon sequestration. However, supplementary feeding experiments have shown promising results in offsetting the negative consequences of OA on shell growth. Our study compared carbon uptake by δ13C tracing and deposition into mantle tissue and shell layers in Magallana gigas and Mytilus species, two economically valuable and common species. After subjecting the species to 7.7 pH, +2 °C seawater, and enhanced feeding, both species maintain shell growth and metabolic pathways under OA without benefitting from extra feeding, thus, showing effective acclimation to rapid and short-term environmental change. Mytilus spp. increases metabolic carbon into the calcite and environmental sourcing of carbon into the shell aragonite in low pH and high temperature conditions. Low pH affects M. gigas mantle nitrogen isotopes maintaining growth. Calcite biomineralization pathway differs between the two species and suggests species-specific response to OA.

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Aquatic productivity under multiple stressors

Published 13 March 2023 Science Closed
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Aquatic ecosystems are responsible for about 50% of global productivity. They mitigate climate change by taking up a substantial fraction of anthropogenically emitted CO2 and sink part of it into the deep ocean. Productivity is controlled by a number of environmental factors, such as water temperature, ocean acidification, nutrient availability, deoxygenation and exposure to solar UV radiation. Recent studies have revealed that these factors may interact to yield additive, synergistic or antagonistic effects. While ocean warming and deoxygenation are supposed to affect mitochondrial respiration oppositely, they can act synergistically to influence the migration of plankton and N2-fixation of diazotrophs. Ocean acidification, along with elevated pCO2, exhibits controversial effects on marine primary producers, resulting in negative impacts under high light and limited availability of nutrients. However, the acidic stress has been shown to exacerbate viral attacks on microalgae and to act synergistically with UV radiation to reduce the calcification of algal calcifiers. Elevated pCO2 in surface oceans is known to downregulate the CCMs (CO2 concentrating mechanisms) of phytoplankton, but deoxygenation is proposed to enhance CCMs by suppressing photorespiration. While most of the studies on climate-change drivers have been carried out under controlled conditions, field observations over long periods of time have been scarce. Mechanistic responses of phytoplankton to multiple drivers have been little documented due to the logistic difficulties to manipulate numerous replications for different treatments representative of the drivers. Nevertheless, future studies are expected to explore responses and involved mechanisms to multiple drivers in different regions, considering that regional chemical and physical environmental forcings modulate the effects of ocean global climate changes.

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Climate change effects on marine species across trophic levels

Published 10 March 2023 Science Closed
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Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. While there are numerous studies that have investigated the response of individual marine organisms to climate change, few studies have focused on differences in organismal responses across trophic levels. Such trophic differences in response to climate change may disrupt ecological interactions and thereby threaten marine ecosystem function. In addition, predation is known as a strong driver that impacts individuals and populations. Despite this, we still do not have a comprehensive understanding of how different trophic levels respond to climate change stressors, predation and their combined effects in marine ecosystems.

The main focus of this thesis is to identify whether marine trophic levels respond differently to climatic stressors and predation. To explore these questions, I have used a combination of traditional mesocosm experiments, together with a statistical method called meta-analysis. I initiated the research by study the responses of marine gastropods at two trophic levels to ocean acidification and predation using long-term mesocosm experiments together with a gastropod-specific meta-analyses. I focused on the amount of phenotypic plasticity in morphological traits of snails when exposed to the two stressors. In order to generalise and test these assumptions among a greater number of marine taxa, I used the meta-analysis approach to investigate the effects of ocean acidification and warming, as well as their combined effects on four marine trophic levels. Finally, to study the individual and combined effects of ocean acidification and predation with respect to inducible defences, I again applied a mesocosm experiment and used blue mussels as a model species.

By using long-term mesocosm experiments and the gastropod-specific meta-analysis on marine gastropods from two trophic levels, I showed that these trophic levels varied in their responses to both ocean acidification and predation. Gastropods at lower trophic levels exhibited greater phenotypic plasticity against predation, while those from higher trophic levels showed stronger tolerance to ocean acidification. Next, by using a meta-analysis, including a large number of species and taxa, examining the effects of ocean acidification and warming, I revealed that top-predators and primary producers were most tolerant to ocean acidification compared to other trophic levels. Herbivores on the other hand, were the most vulnerable trophic level against abiotic stress. Again, using the meta-analysis approach, but this time incorporating only factorial experimental data that included the interactive effects of ocean acidification and ocean warming, I showed that higher trophic levels again were the most tolerant trophic level, and herbivores being most sensitive, with respect to the combined effect of the two stressors. Contrary to previous discussions in the literature concerning multiple climate-related stressors, antagonistic and additive effects occurred most frequently, while synergistic effects were less common and which decreased with increasing trophic rank. Finally, by conducting a fully-factorial experiment using blue mussels, I found that mussels with previous experience contact with predator has developed greater inducible defences than ones without previous experience. However, levels of ocean acidification may mask predator cues, or obstruct shell material, and consequently disrupt blue mussels inducible defence from crab predation.

In summary, marine trophic levels respond differently to both biotic and climatic stressors. Higher trophic levels, together with primary producers, were often more robust against abiotic stress and may therefore be better prepared for future oceans compare species from lower trophic levels. These results may provide vital information for: implementing effective climate change mitigation, to understand which stressors to act on, and when and where to intervene for prioritizing conservation actions.

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Predicting effects of multiple interacting global change drivers across trophic levels

Published 8 March 2023 Science Closed
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Global change encompasses many co-occurring anthropogenic drivers, which can act synergistically or antagonistically on ecological systems. Predicting how different global change drivers simultaneously contribute to observed biodiversity change is a key challenge for ecology and conservation. However, we lack the mechanistic understanding of how multiple global change drivers influence the vital rates of multiple interacting species. We propose that reaction norms, the relationships between a driver and vital rates like growth, mortality, and consumption, provide insights to the underlying mechanisms of community responses to multiple drivers. Understanding how multiple drivers interact to affect demographic rates using a reaction-norm perspective can improve our ability to make predictions of interactions at higher levels of organization—that is, community and food web. Building on the framework of consumer–resource interactions and widely studied thermal performance curves, we illustrate how joint driver impacts can be scaled up from the population to the community level. A simple proof-of-concept model demonstrates how reaction norms of vital rates predict the prevalence of driver interactions at the community level. A literature search suggests that our proposed approach is not yet used in multiple driver research. We outline how realistic response surfaces (i.e., multidimensional reaction norms) can be inferred by parametric and nonparametric approaches. Response surfaces have the potential to strengthen our understanding of how multiple drivers affect communities as well as improve our ability to predict when interactive effects emerge, two of the major challenges of ecology today.

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Wanted dead or alive: skeletal structure alteration of cold-water coral Desmophyllum pertusum (Lophelia pertusa) from anthropogenic stressors

Published 7 March 2023 Science Closed
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Ocean acidification (OA) has provoked changes in the carbonate saturation state that may alter the formation and structural biomineralisation of calcium carbonate exoskeletons for marine organisms. Biomineral production in organisms such as cold-water corals (CWC) rely on available carbonate in the water column and the ability of the organism to sequester ions from seawater or nutrients for the formation and growth of a skeletal structure. As an important habitat structuring species, it is essential to examine the impact that anthropogenic stressors (i.e., OA and rising seawater temperatures) have on living corals and the structural properties of dead coral skeletons; these are important contributors to the entire reef structure and the stability of CWC mounds. In this study, dead coral skeletons in seawater were exposed to various levels of pCO2 and different temperatures over a 12-month period. Nanoindentation was subsequently conducted to assess the structural properties of coral samples’ elasticity (E) and hardness (H), whereas the amount of dissolution was assessed through scanning electron microscopy. Overall, CWC samples exposed to elevated pCO2 and temperature show changes in properties which leave them more susceptible to breakage and may in turn negatively impact the formation and stability of CWC mound development.

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Ocean acidification-mediated food chain transfer of polonium between primary producers and consumers

Published 7 March 2023 Science Closed
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Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify 210Po by 3–4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F20, 215 = 176.84, p < 0.001; time: F3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F2 = 169.15, p < 0.0001; algae species: F2 = 10.21, p < 0.0001; pH: F1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F2 = 19.48, p < 0.0001; copepod x pH: F2 = 10.54, p < 0.0001; algae x pH: F2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification.

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Enormously enhanced particulate organic carbon and nitrogen production by elevated CO2 and moderate aluminum enrichment in the coccolithophore Emiliania huxleyi

Published 6 March 2023 Science Closed
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Aluminum (Al) is abundant and ubiquitous in the environment. However, little information is available on its effects on photosynthetic microbes in alkaline seawater. Thus, we investigated the physiological performance in the most cosmopolitan coccolithophorid, viz., Emiliania huxleyi, grown under low (410 µatm) and high (1000 µatm) CO2 levels in seawater having none (0 nM, NAl), low (0.2 µM, LAl) and high (2 µM, HAl) Al concentrations. Under low CO2 conditions, the specific growth rate showed no significant difference between the NAl and LAl treatments, which was higher than the HAL treatment. Elevated CO2 inhibited the growth rate in the NAl and LAl cultures but did not affect the HAl cultures. The addition of Al had no effects on (LAl) or slightly elevated (HAl) the particulate organic carbon (POC) production rate under low CO2 conditions. With increasing CO2 concentration, the production rate of POC was enhanced by 55.3 % during the NAl treatment and further increased by 22.3 % by adding 0.2 µM Al. The responses of particulate organic nitrogen (PON) production rate, cellular POC, and PON contents to the different treatments revealed the same pattern as those of the POC production rate. The particulate inorganic carbon (PIC) production rate and PIC/POC ratio were not affected by Al under low CO2 conditions. They were significantly decreased by elevated CO2 in the LAl and HAl cultures. Our results indicate that high CO2 could increase carbon export to ocean depths by elevating the efficiency of the biological pump at low Al levels occurring in natural seawater (0.2 μM), with potentially significant implications for the carbon cycle of the ocean under accelerating anthropogenic influences.

Continue reading ‘Enormously enhanced particulate organic carbon and nitrogen production by elevated CO2 and moderate aluminum enrichment in the coccolithophore Emiliania huxleyi’

Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes

Published 3 March 2023 Science Closed
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This study assessed the energy budget for juvenile Atlantic Sea Scallop, Placopecten magellanicus, during a natural drop in temperature (15.6°C to 5.8°C) over an 8-week time period during the fall at three different enrichment levels of carbon dioxide (CO2). Every 2 weeks, individuals were sampled for ecophysiological measurements of feeding activity, respiration rate (RR) and excretion rate (ER) to enable the calculation of scope for growth (SFG) and atomic oxygen:nitrogen ratios (O:N). In addition, 36 individuals per treatment were removed for shell height, dry tissue weight (DTW) and dry shell weight (DSW). We found a significant decrease in feeding rates as CO2 increased. Those rates also were significantly affected by temperature, with highest feeding at 9.4°C. No significant CO2 effect was observed for catabolic energy processes (RR and ER); however, these rates did increase significantly with temperature. The O:N ratio was not significantly affected by CO2, but was significantly affected by temperature. There was a significant interaction between CO2 and temperature for ER and the O:N ratio, with low CO2 levels resulting in a U-shaped response that was not sustained as CO2 levels increased. This suggests that the independent effects of CO2 and temperature observed at low levels are different once a CO2 threshold is reached. Additionally, there were significant differences in growth estimators (shell height and DSW), with the best growth occurring at the lowest CO2 level. In contrast to temperature variations that induced a trade-off response in energy acquisition and expenditure, results from this research support the hypothesis that sea scallops have a limited ability to alter physiological processes to compensate for increasing CO2.

Continue reading ‘Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes’

Thanks mum. Maternal effects in response to ocean acidification of sea urchin larvae at different ecologically relevant temperatures

Published 3 March 2023 Science Closed
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Graphical abstract

Highlights

  • Ocean acidification and temperature differently influence larval development of Arbacia lixula and Paracentrotus lividus.
  • Larvae of the two A. lixula populations (ambient-pH vs vent sites) respond differently to ocean acidification and temperature.
  • Maternal buffer effect was observed in response to ocean acidification and temperature in both species.
  • A. lixula seems to be more tolerant to changes in temperature than P. lividus.

Abstract

Juvenile stages of marine species might be more vulnerable than adults to climate change, however larval vulnerability to predictable environmental changes can be mitigated by parental anticipatory buffer effects occurring during gametogenesis. In this study, ocean acidification effect were investigated on larval growth of two sea urchins, Arbacia lixula and Paracentrotus lividus, at different temperature levels. Results showed that altered pH and temperature affected larval development in both species, with significant length reductions of spicules and significant increases in abnormal larvae. Detrimental effects of reduced pH and high temperature were however dependent on the mother. Furthermore, the responses of A. lixula larvae from the ambient site (pH ∼ 8.0) were compared with those of larvae obtained from mothers collected from a natural CO2 vent (pH ∼ 7.7) in Ischia. Comparisons highlighted a transgenerational response, as the CO2 vent larvae proved to be more resilient to reduced pH, although more sensitive to increased temperature.

Continue reading ‘Thanks mum. Maternal effects in response to ocean acidification of sea urchin larvae at different ecologically relevant temperatures’
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