Posts Tagged 'crustaceans'



Effects of ocean acidification on the respiration and feeding of juvenile red and blue king crabs (Paralithodes camtschaticus and P. platypus)

Ocean acidification is a decrease in pH resulting from dissolution of anthropogenic CO2 in the oceans that has physiological effects on many marine organisms. Juvenile red and blue king crabs (Paralithodes camtschaticus and P. platypus) exhibit both increased mortality and decreased growth in acidified waters. In this study, we determined how ocean acidification affects oxygen consumption, feeding rates, and growth in both species. Juvenile crab were exposed to three pH levels: ambient (pH 8.1), pH 7.8, and pH 7.5 for 3 weeks. Oxygen consumption and feeding ration were determined immediately after exposure to treatment water and after 3 weeks’ exposure. Growth was calculated as a change in wet mass. Both species exhibited initially increased oxygen consumption at pH 7.5, but not after 3 weeks. Feeding rations did not vary with pH or exposure time. Red king crabs that moulted grew more in ambient water than in pH 7.5. The initial increase in oxygen consumption at pH 7.5 suggests the crab increased metabolism and expended more energy in osmo-/iono-regulation. Without an increase in feeding ration, it is likely the crab reduced energy expenditure in other areas, explaining the reduced growth and increased mortality observed in this and other studies.

Continue reading ‘Effects of ocean acidification on the respiration and feeding of juvenile red and blue king crabs (Paralithodes camtschaticus and P. platypus)’

Impact of seawater acidification on shell property of the Manila clam Ruditapes philippinarum grown within and without sediment

Although the impact of ocean acidification on marine bivalves has been previously investigated under mainly controlled laboratory conditions, it is still unclear whether the impact of acidification on sediment-burrowing species differs between those within or without sediment. In order to fill this gap in our knowledge, we compared shell properties of the infaunal Manila clam (Ruditapes philippinarum) exposed to three pH concentrations (7.4, 7.7, and 8.0), within and without sediments. In the first experiment (140 d), clams were exposed to seawater in an acidification system without sediment. A decrease in shell weight corresponding to the increase in dissolution rate was observed in the group of pH 7.4, at which shell color disappeared or whitened. SEM observations confirmed the changes of the external shell surface. In the second experiment (170 d), sediment was placed at the bottom of each exposure chamber. The effects were found obvious in shell dissolution rate and shell color in the shell specimens exposed to overlying seawater but not found in the shell specimens exposed to sediment. Although the experimental period was longer in the second experiment, shell specimens in the first experiment were more seriously damaged than those in the second experiment under acidic seawater conditions. Our results, in relation to the defense function of the shell, show that marine bivalves in burrowing behavior are more adaptable to seawater acidification than those who do not burrow into sediment.

Continue reading ‘Impact of seawater acidification on shell property of the Manila clam Ruditapes philippinarum grown within and without sediment’

Physiological effects of climate change on the American lobster, Homarus americanus

Increases in anthropogenic input of carbon dioxide into the atmosphere have caused widespread patterns of ocean warming and ocean acidification. Both processes will likely have major impacts on commercial fisheries and aquaculture, with acidification posing a particular threat to many marine calcifying invertebrates. In the State of Maine, commercial fisheries landings and a growing aquaculture industry have a combined value in excess of $600 million, 75% of which is sustained by marine calcifiers. Moreover, the American lobster (Homarus americanus) supports the most economically valuable fishery in the Gulf of Maine and Atlantic Canada. Previous research has documented a strong link between lobster biology and ocean temperature, but it is unclear how H. americanuswill respond to a rapidly changing environment. Additionally, previous efforts have focused primarily on the direct effects of a changing climate on lobsters (i.e., changes in growth, survival, and calcification), with little emphasis placed on the potential for sublethal effects to impact the population.

In this dissertation, I explore the effects of increasing ocean temperatures and acidification on H. americanus to understand how environmental changes can alter the health and physiology in multiple life stages of marine calcifying invertebrates. In Chapter 1, I introduce the global patterns and effects of climate change on marine calcifiers and review the current state of knowledge of my study species. In Chapter 2, I discuss how exposure to warming conditions impacts larval development, with a focus on potential trade-offs between enhanced growth and developmental instability. In Chapter 3, I continue to explore the sublethal impacts of warming on larval lobsters by examining changes in gene expression patterns in postlarvae exposed to varying temperatures during development. Chapter 4 explores how short-term exposure to acidified conditions impacts subadult (50 – 65 mm carapace length) lobster thermal physiology, hemolymph chemistry, and stress levels, a relatively understudied yet crucial life history stage. Finally, Chapter 5 summarizes the overarching themes of the dissertation, and concludes by providing suggestions for future research efforts.

Continue reading ‘Physiological effects of climate change on the American lobster, Homarus americanus’

Intraspecific variation in the response of the estuarine European isopod Cyathura carinata (Krøyer, 1847) to ocean acidification

Highlights

• Responses of the estuarine isopod Cyathura carinata to acidification were studied in the light of future OA scenarios.

• Survival, mortality, growth rate, and metabolic parameters were differentially affected by acidification depending on the pH habitat of origin of the animals.

• CO2-seawater acidification significantly affected the lifespan of C. carinata.

• Population of C. carinata from stable pCO2 environments could be vulnerable to ocean acidification, however, those from highly pCO2 variable habitats will be able to survive.

Abstract

In the present study the model isopod, Cyathura carinata were exposed to four pHNIST treatments (control: 7.9; 7.5, 7, 6.5) in order to determine the tolerance and pH threshold value this estuarine species withstand under future acidification scenarios. Seawater acidification significantly affected the lifespan of C. carinata, where population density was remarkably reduced at the lowest pH treatment. The longevity, survivorship and swimming activity (related to the acquisition of energy) of these isopods decreased with decreasing pH. Furthermore, to determine the possible metabolic plasticity of this species, the swimming activity, the Na+/K + -ATPase activity (relevant for osmoregulation process), and the RNA:DNA ratio (an indicator of fitness) were measure from two populations of C. carinata, one inhabiting a stable environment (pHNIST 7.5–8.0) and one inhabiting a fluctuating pCO2 regimes (pH 3.3–8.5) subjected to three pH treatments (7.9, 7.0 and 6.5). The population from high fluctuating pCO2 conditions showed capacity to withstand to pH 6.5, as well as higher longevity and metabolic plasticity, when compared with the population from the habitat with slight pCO2 variation. These results indicate that Cyathura population from stable environments could be vulnerable to ocean acidification because it could trigger detrimental effects on its survival energy budget, and growth. However, ocean acidification has limited effect on the energy budget and survival of C. carinata population from highly variable habitats, suggesting that they are able to cope with the elevated energy demand. The difference showed between populations is likely an indication of genetic differentiation in tolerance to ocean acidification, possibly attributable to local adaptations, which could provide the raw material necessary for adaptation to future conditions. In addition, our results suggest that when assessing marine crustacean responses to changing environments on a global scale, variability in population and metabolic responses need to be considered.

Continue reading ‘Intraspecific variation in the response of the estuarine European isopod Cyathura carinata (Krøyer, 1847) to ocean acidification’

Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs

Predator-prey interactions often drive ecological patterns and are governed by factors including predator feeding rates, prey behavioral avoidance, and prey structural defenses. Invasive species can also play a large ecological role by disrupting food webs, driving local extinctions, and influencing evolutionary changes in prey defense mechanisms. This study documents a substantial reduction in the behavioral and morphological responses of multiple gastropod species (Nucella lapillus, N. ostrina, Urosalpinx cinerea) to an invasive predatory crab (green crab Carcinus maenas) under ocean acidification conditions. These results suggest that climate-related changes in ocean chemistry may diminish non-lethal effects of predators on prey responses including behavioral avoidance. While snails with varying shell mineralogies were similarly successful at deterring predation, those with primarily aragonitic shells were more susceptible to dissolution and erosion under high CO2 conditions. The varying susceptibility to predation among species with similar ecological roles could indicate that the impacts of invasive species like green crabs could be modulated by the ability of native and invasive prey to withstand ocean acidification conditions.

Continue reading ‘Ocean acidification may alter predator-prey relationships and weaken nonlethal interactions between gastropods and crabs’

Multiple stressor effects on macrobenthic communities in Corpus Christi Bay, Texas, U.S.A.

At any moment in nature, organisms are likely being exposed to multiple stressors, the effects of which are difficult to separate. Often, however, environmental stressors are considered on an individual basis. In southeastern Corpus Christi Bay, TX, declines in benthic macrofaunal community abundance, biomass, diversity, species richness, and species evenness have largely been attributed to the occurrence of hypoxia, a condition of low dissolved oxygen (DO). This study proposes that multiple stressors contribute to these observed benthic macrofaunal declines in southeastern Corpus Christi Bay. Therefore, a 30-year time series of water quality data (salinity, temperature, DO, pH, phosphate, ammonium, nitrite+nitrate, sulfate) and benthic community data (abundance, biomass, species richness, species evenness) was analyzed to describe 1) water quality dynamics of the region and 2) relationships between water quality dynamics and benthic macrofaunal response. Principal component analysis indicated that a large variability in the water quality dataset (63%) could be summarized by three principal components representing a multiple stressor index, a nutrient index, and an acidification index. Seasonality was found to be confounded with the multiple stressor index but not the nutrient or acidification indexes. Spearman rank-order correlations indicated both the multiple stressor and acidification indexes were inversely related to benthic macrofaunal community abundance, biomass, and species richness. A stepwise multiple linear regression analysis on individual water quality variables specified DO, and possibly temperature, to be leading explanatory variables for predicting benthic abundance. Temperature, pH, and nitrite+nitrate were indicated as leading explanatory variables for predicting benthic biomass. Temperature was indicated to be the only leading explanatory variable for predicting species richness. Results demonstrate that multiple stressors, including high temperature, high salinity, and low DO concentrations, are collectively acting on benthic communities in southeastern Corpus Christi Bay.

Continue reading ‘Multiple stressor effects on macrobenthic communities in Corpus Christi Bay, Texas, U.S.A.’

No compromise between metabolism and behavior of decorator crabs in reduced pH conditions

Many marine calcifiers experience metabolic costs when exposed to experimental ocean acidification conditions, potentially limiting the energy available to support regulatory processes and behaviors. Decorator crabs expend energy on decoration camouflage and may face acute trade-offs under environmental stress. We hypothesized that under reduced pH conditions, decorator crabs will be energy limited and allocate energy towards growth and calcification at the expense of decoration behavior. Decorator crabs, Pelia tumida, were exposed to ambient (8.01) and reduced (7.74) pH conditions for five weeks. Half of the animals in each treatment were given sponge to decorate with. Animals were analyzed for changes in body mass, exoskeleton mineral content (Ca and Mg), organic content (a proxy for metabolism), and decoration behavior (sponge mass and percent cover). Overall, decorator crabs showed no signs of energy limitation under reduced pH conditions. Exoskeleton mineral content, body mass, and organic content of crabs remained the same across pH and decoration treatments, with no effect of reduced pH on decoration behavior. Despite being a relatively inactive, osmoconforming species, Pelia tumida is able to maintain multiple regulatory processes and behavior when exposed to environmental pH stress, which underscores the complexity of responses within Crustacea to ocean acidification conditions.

Continue reading ‘No compromise between metabolism and behavior of decorator crabs in reduced pH conditions’


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