Posts Tagged 'mollusks'

Ocean acidification decreases mussel byssal attachment strength and induces molecular byssal responses

Ocean acidification (OA) is a term describing the uptake of CO2 from the atmosphere, decreasing seawater pH and altering carbonate chemistry. Mussels are an ecologically and economically important taxon that attach to solid surfaces via the byssus. To date, little is known about the effects of OA on mussel byssal attachment and the underlying molecular byssal responses. This study demonstrated that after 1 wk of exposure to acidified seawater, both mechanical properties (such as strength and extensibility) and the numbers of byssal threads produced by Mytilus coruscus were significantly reduced, leading to a 60 to 65% decrease in mussel byssal attachment strength. Real-time PCR results suggested that OA also altered the expression of genes encoding the proximal thread matrix protein (PTMP), precursor collagen proteins (preCOL-P, -NG and -D) and mussel foot proteins (mfp-1, -2, -3, -4, -5 and -6). The down-regulation of some specific byssal proteins may be one of the reasons for the weakened mechanical properties of individual byssal threads under OA conditions. In contrast, the up-regulation of some other specific byssal proteins may be adaptive responses to minimize the adverse effect of OA on byssal attachment. OA may weaken mussel byssal attachment by reducing the production and mechanical properties of byssal threads and by inducing byssal molecular responses. The weakened byssal attachment induced by OA therefore could pose a substantial threat to both mussel aquaculture and mussel-bed ecosystems.

Continue reading ‘Ocean acidification decreases mussel byssal attachment strength and induces molecular byssal responses’

Effects of elevated carbon dioxide and temperature on locomotion and the repeatability of lateralization in a keystone marine mollusc

Recent work has shown that the behaviour of marine organisms can be affected by elevated pCO2, although little is known about the effect of multiple stressors. We therefore investigated the effect of elevated pCO2 and temperature on locomotion and behaviour during prey searching in the marine gastropod Concholepas concholepas, a predator characteristic of the southeastern Pacific coast. Movement duration, decision time, route finding and lateralization were measured using a T-maze tank with a prey positioned behind a barrier. Four treatments, representing present day and near-future scenarios of ocean acidification and warming were used in rearing the individuals for 6 months. Regardless of the treatment, no significant differences were found in relative and absolute lateralization before and after exposure for 6 months. However, relative lateralization was not repeatable for animals tested after 6 months at elevated pCO2 at both experimental temperatures, whereas it was repeatable in individuals kept at the present day level of pCO2. We suggest that these effects may be related to a behavioural malfunction caused by elevated pCO2. Movement duration, decision time and route finding were not repeatable. However, movement duration and decision time increased and route finding decreased in elevated pCO2 (at 15°C), suggesting that elevated pCO2 has negative effects on the locomotor and sensory performance of C. concholepas in the presence of a prey odour, thereby decreasing their ability to forage efficiently.

Continue reading ‘Effects of elevated carbon dioxide and temperature on locomotion and the repeatability of lateralization in a keystone marine mollusc’

Linking the biological impacts of ocean acidification on oysters to changes in ecosystem services: A review

Continued anthropogenic carbon dioxide emissions are acidifying our oceans, and hydrogen ion concentrations in surface oceans are predicted to increase 150% by 2100. Ocean acidification (OA) is changing ocean carbonate chemistry, including causing rapid reductions in calcium carbonate availability with implications for many marine organisms, including biogenic reefs formed by oysters. The impacts of OA are marked. Adult oysters display both decreased growth and calcification rates, while larval oysters show stunted growth, developmental abnormalities, and increased mortality. These physiological impacts are affecting ecosystem functioning and the provision of ecosystem services by oyster reefs. Oysters are ecologically and economically important, providing a wide range of ecosystem services, such as improved water quality, coastlines protection, and food provision. OA has the potential to alter the delivery and the quality of the ecosystem services associated with oyster reefs, with significant ecological and economic losses. This review provides a summary of current knowledge of OA on oyster biology, but then links these impacts to potential changes to the provision of ecosystem services associated with healthy oyster reefs.

Continue reading ‘Linking the biological impacts of ocean acidification on oysters to changes in ecosystem services: A review’

Mineralogical plasticity acts as a compensatory mechanism to the impacts of ocean acidification

Calcifying organisms are considered particularly susceptible to the future impacts of ocean acidification (OA), but recent evidence suggests that they may be able to maintain calcification and overall fitness. The underlying mechanism remains unclear but may be attributed to mineralogical plasticity, which modifies the energetic cost of calcification. To test the hypothesis that mineralogical plasticity enables the maintenance of shell growth and functionality under OA conditions, we assessed the biological performance of a gastropod (respiration rate, feeding rate, somatic growth, and shell growth of Austrocochlea constricta) and analyzed its shell mechanical and geochemical properties (shell hardness, elastic modulus, amorphous calcium carbonate, calcite to aragonite ratio, and magnesium to calcium ratio). Despite minor metabolic depression and no increase in feeding rate, shell growth was faster under OA conditions, probably due to increased precipitation of calcite and trade-offs against inner shell density. In addition, the resulting shell was functionally suitable for increasingly “corrosive” oceans, i.e., harder and less soluble shells. We conclude that mineralogical plasticity may act as a compensatory mechanism to maintain overall performance of calcifying organisms under OA conditions and could be a cornerstone of calcifying organisms to acclimate to and maintain their ecological functions in acidifying oceans.

Continue reading ‘Mineralogical plasticity acts as a compensatory mechanism to the impacts of ocean acidification’

Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors

Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO2 and examined the impacts of elevated CO2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO2 had a positive impact on larvae reared at elevated CO2 as a sole stressor, which were 8% larger and developed faster at elevated CO2 compared with larvae from adults exposed to ambient CO2. These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO2-exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors.

Continue reading ‘Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors’

Seawater acidification induced immune function changes of haemocytes in Mytilus edulis: a comparative study of CO2 and HCl enrichment

The present study was performed to evaluate the effects of CO2− or HCl-induced seawater acidification (pH 7.7 or 7.1; control: pH 8.1) on haemocytes of Mytilus edulis, and the changes in the structure and immune function were investigated during a 21-day experiment. The results demonstrated that seawater acidification had little effect on the cellular mortality and granulocyte proportion but damaged the granulocyte ultrastructure. Phagocytosis of haemocytes was also significantly inhibited in a clearly concentration-dependent manner, demonstrating that the immune function was affected. Moreover, ROS production was significantly induced in both CO2 and HCl treatments, and four antioxidant components, GSH, GST, GR and GPx, had active responses to the acidification stress. Comparatively, CO2 had more severe destructive effects on haemocytes than HCl at the same pH level, indicating that CO2 stressed cells in other ways beyond the increasing H+ concentration. One possible explanation was that seawater acidification induced ROS overproduction, which damaged the ultrastructure of haemocytes and decreased phagocytosis.

Continue reading ‘Seawater acidification induced immune function changes of haemocytes in Mytilus edulis: a comparative study of CO2 and HCl enrichment’

Conus Shell δ13C values as proxies for δ13CDIC in tropical waters

We use time-series δ18O and δ13C data from seawater and live-collected Conus shells from Panama’s Pacific coast to test the fidelity of the gastropod’s δ13C values as a proxy for the δ13C of marine dissolved inorganic carbon (DIC), and the potential of δ18O-δ13C correlations in shell profiles for resolving relative magnitudes of seasonal upwelling and freshening. Water samples were collected from March 2011 to August 2012 from Naos Island Marine Laboratory, and Conus specimens were collected from nearby Veracruz Beach in July 2013. In general, patterns corresponded with seasonal changes in rainfall and upwelling on the Pacific coast of Panama. During the long rainy season, the upwelling signal is absent and seawater salinity, δ18O, and δ13CDIC all decline. During the dry season, the upwelling signal increases and runoff declines increasing salinity, δ18O, and δ13CDIC values. Shell δ13C values strongly correlate with measured δ13CDIC values, but are lower than expected equilibrium for aragonite by approximately + 2‰ reflecting the incorporation of light metabolic C. The co-dependences of δ18O and δ13C provide reliable indicators of upwelling (negative correlation) and freshening (positive correlation) for nearshore environments, allowing for the study of historical climate change and upwelling based on beach-collected museum specimens.

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Ocean acidification in the IPCC AR5 WG II

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