Posts Tagged 'crustaceans'

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’

CO2 leakage simulation: effects of the decreasing pH to the survival and reproduction of two crustacean species

Highlights

• Both species show reduction in their fitness when exposed to CO2 acidification scenarios.

• The isopod Cyathura carinata survives at pH as low as 6.5, not the amphipod Elasmopus rapax

• The impairment observed in E. rapax was more severe than in C. carinata.

• Regardless the lengths of the lifespan, both species were unable to produce offspring.

Abstract

The effects of CO2-related acidification on two crustacean populations, the isopod Cyathura carinata and the amphipod Elasmopus rapax, were studied. Three pH levels were tested: artificial seawater without CO2 injection and two levels of reduced pH. Even though RNA:DNA ratio was reduced for both species, no statistical significant differences were found between the control and the treatments. Both species experienced a reduction in survivorship, longevity and the body length of surviving animals; although the impairment observed in E. rapax was more severe than in C. carinata. The long life span isopod and the short life span amphipod experienced a high degree of impairment in the reproduction, likely due to the reallocation of resources from reproduction to body maintenance and increasing survival by postponing the brood production. Regardless of the underlying processes and the energetic pathways, both experienced failure to reproduce, which could lead to the local extinction of these species.

Continue reading ‘CO2 leakage simulation: effects of the decreasing pH to the survival and reproduction of two crustacean species’

Ocean acidification alters thermal cardiac performance, hemocyte abundance, and hemolymph chemistry in subadult American lobsters Homarus americanus H. Milne Edwards, 1837 (Decapoda: Malcostraca: Nephropidae)

Increased anthropogenic input of carbon dioxide into the atmosphere has caused widespread patterns of ocean acidification (OA) and increased the frequency of extreme warming events. We explored the sublethal effects of OA on the hemolymph chemistry and physiological response to acute thermal stress in the American lobster (Homarus americanus H. Milne Edwards, 1837). We exposed subadult lobsters to current or predicted end-century pH conditions (8.0 and 7.6, respectively) for 60 days. Following exposure, we assessed hemolymph Llactate and calcium concentrations (as indicators of oxygen carrying capacity), ecdysterone concentrations, total protein content, and total hemocyte counts (THCs) as an indicator of immune response. We also assessed cardiac performance in the context of an acute warming event using impedance pneumography. Calcium, total protein, and ecdysterone concentrations were not significantly altered (P ≥ 0.10) by OA exposure. Control lobsters, however, had significantly higher levels of Llactate concentrations compared to acidified lobsters, suggesting reduced oxygen carrying capacity under OA. THCs were also 61% higher in control versusacidified lobsters, suggesting immunosuppression under chronic OA. Lobsters exposed to acidified conditions exhibited reduced cardiac performance under acute warming as indicated by significantly lower (P = 0.040) Arrhenius Break Temperatures compared to control lobsters. These results suggest that although some physiological endpoints of American lobster are not impacted by OA, the stress of OA will likely be compounded by acute heat shock and may present additional physiological challenges for this species in the face of future change.

Continue reading ‘Ocean acidification alters thermal cardiac performance, hemocyte abundance, and hemolymph chemistry in subadult American lobsters Homarus americanus H. Milne Edwards, 1837 (Decapoda: Malcostraca: Nephropidae)’

Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline–alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda

Carbonate alkalinity, salinity, and pH are three important stress factors for aquatic animals in saline–alkaline water. Carbonic anhydrases (CAs) catalyze the reversible reaction of CO2 reported to play an important role in the acid–base regulation in vertebrates. To explore the molecular mechanism of CAs efficacy in shrimp after their transfer into saline–alkaline water, the cDNAs of three CAs (EcCAc, EcCAg, and EcCAb) were cloned from Exopalaemon carinicauda. Sequence analysis showed that EcCAc and EcCAg both possessed a conserved α-CA domain and a proton acceptor site, and EcCAb contained a Pro-CA domain. Tissue expression analysis demonstrated that EcCAc and EcCAg were most abundantly in gills, and EcCAb was highly expressed in muscle. The cumulative mortalities remained below 25% under exposure to pH (pH 6 and pH 9), low salinity (5 ppt), or high carbonate alkalinity (5 and 10 mmol/L) after 72 h of exposure. However, mortalities increased up to 70% under extreme saline–alkaline stress (salinity 5 ppt, carbonate alkalinity 10 mmol/L, and pH 9) after 14 days of exposure. The EcCAc and EcCAg expressions in gills were significantly upregulated during the early period of pH and saline–alkaline stresses, while the EcCAb expressions showed no regular or large changes. The two-way ANOVA found significant interactions between salinity and carbonate alkalinity observed in EcCAc, EcCAg, and EcCAb expressions (p < 0.05). Furthermore, an RNA interference experiment resulted in increased mortality of EcCAc- and EcCAg-silenced prawns under saline–alkaline stress. EcCAc knockdown reduced expressions of Na+/H+ exchanger (EcNHE) and sodium bicarbonate cotransporter (EcNBC), and EcCAg knockdown reduced EcCAc, EcNHE, EcNBC, and V-type H+-ATPase (EcVTP) expressions. These results suggest EcCAc and EcCAg as important modulators in response to pH and saline–alkaline stresses in E. carinicauda.

Continue reading ‘Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline–alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda’

Interaction of short-term copper pollution and ocean acidification in seagrass ecosystems: toxicity, bioconcentration and dietary transfer

Highlights

• Toxicity and bioconcentration of copper in seagrasses were not affected by pH.
• Complex copper-pH interactions were observed in the seagrass photosynthesis.
• Seagrasses can act as a copper source in the food web via direct consumption.

Abstract

We aimed to show how the predicted pH decrease in the ocean would alter the toxicity, bioconcentration and dietary transfer of trace metal copper on seagrass ecosystems, on a short-term basis. Seagrass Zostera noltei was exposed to two pH levels (8.36 and 8.03) and three copper levels (nominal concentrations, <3, 30 and 300 μg Cu L−1) in a factorial design during 21 days, while Gammarus locusta amphipods were continuously fed with the treated seagrass leaves. We found that the toxicity and bioconcentration of copper in seagrasses were not affected by pH, yet complex copper-pH interactions were observed in the seagrass photosynthesis. We demostrated that seagrasses can act as a copper source in the food web via direct consumption by herbivores. Future research need to investigate the interactive effects on a long-term basis, and to include biochemical and molecular endpoints to provide additional insights to the complex phisiological interactions observed.

Continue reading ‘Interaction of short-term copper pollution and ocean acidification in seagrass ecosystems: toxicity, bioconcentration and dietary transfer’


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Ocean acidification in the IPCC AR5 WG II

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