Posts Tagged 'mollusks'

Effects of seawater acidification and salinity alterations on metabolic, osmoregulation and oxidative stress markers in Mytilus galloprovincialis

The impacts of seawater acidification and salinity shifts on metabolism, energy reserves, and oxidative status of mussels have been largely neglected. With the aim to increase the current knowledge for the mussel Mytilus galloprovincialis a 28-day chronic test was conducted during which mussels were exposed to two pH (7.8 and 7.3; both at control salinity 28) and three salinity (14, 28 and 35, at control pH, 7.8) levels. After exposure to different conditions, mussels electron transport system activity, energy reserves (protein and glycogen content) carbonic anhydrase activity, antioxidant defences and cellular damage were measured. Results obtained showed that mussels exposed to seawater acidification presented decreased metabolic capacity that may have induced lower energy expenditure (observed in higher glycogen, protein and lipids content at this condition). Low pH condition induced the increase of carbonic anhydrase activity that was related to acid-base balance, while no significant activation of antioxidant defence mechanisms was observed resulting in higher LPO. Regarding the impacts of salinity, the present study showed that at the highest salinity (35) mussels presented lower metabolic activity (also related to lower energetic expenditure) and an opposite response was observed at salinity 14. Carbonic anhydrase slightly increased at stressful salinity conditions, a mechanism of homeostasis maintenance. Lower metabolic activity at the highest salinity, probably related to valves closure, helped to mitigate the increase of LPO in this condition. At low salinity (14), despite an increase of antioxidant enzymes activity, LPO increased, probably as a result of ROS overproduction from higher electron transport system activity. The present findings demonstrated that Mytilus galloprovincialis oxidative status and metabolic capacity were negatively affected by low pH and salinity changes, with alterations that may lead to physiological impairments namely on mussels reproductive output, growth performance and resistance to disease, with ecological and economic implications.

Continue reading ‘Effects of seawater acidification and salinity alterations on metabolic, osmoregulation and oxidative stress markers in Mytilus galloprovincialis’

High pCO2 and elevated temperature reduce survival and alter development in early life stages of the tropical sea hare Stylocheilus striatus

Elevated temperature (ocean warming) and reduced oceanic pH (ocean acidification) are products of increased atmospheric pCO2, and have been shown in many marine taxa to alter morphology, impede development, and reduce fitness. Here, we investigated the effects of high pCO2 and elevated temperature on developmental rate, hatching success, and veliger morphology of embryos of the tropical sea hare, Stylocheilus striatus. Exposure to high pCO2 resulted in significant developmental delays, postponing hatching by nearly 24 h, whereas exposure to elevated temperature (in isolation or in combination with high pCO2) resulted in accelerated development, with larvae reaching several developmental stages approximately 48 h in advance of controls. Hatching success was reduced by ~20 and 55% under high pCO2 and warming, respectively, while simultaneous exposure to both conditions resulted in a nearly additive 70% reduction in hatching. In addition to these ontological and lethal effects, exposure of embryos to climate change stressors resulted in significant morphological effects. Larval shells were nearly 40% smaller under high pCO2 and warming in isolation and up to 53% smaller under multi-stressor conditions. In general, elevated temperature had the largest impact on development, with temperature-effects nearly 3.5-times the magnitude of high pCO2-effects. These results indicate that oceanic conditions congruent with climate change predictions for the end of the twenty-first century suppress successful development in S. striatus embryos, potentially reducing their viability as pelagic larvae.

Continue reading ‘High pCO2 and elevated temperature reduce survival and alter development in early life stages of the tropical sea hare Stylocheilus striatus’

Shelled pteropods in peril: Assessing vulnerability in a high CO2 ocean

The impact of anthropogenic ocean acidification (OA) on marine ecosystems is a vital concern facing marine scientists and managers of ocean resources. Euthecosomatous pteropods (holoplanktonic gastropods) represent an excellent sentinel for indicating exposure to anthropogenic OA because of the sensitivity of their aragonite shells to the OA conditions less favorable for calcification. However, an integration of observations, experiments and modelling efforts is needed to make accurate predictions of how these organisms will respond to future changes to their environment. Our understanding of the underlying organismal biology and life history is far from complete and must be improved if we are to comprehend fully the responses of these organisms to the multitude of stressors in their environment beyond OA. This review considers the present state of research and understanding of euthecosomatous pteropod biology and ecology of these organisms and considers promising new laboratory methods, advances in instrumentation (such as molecular, trace elements, stable isotopes, palaeobiology alongside autonomous sampling platforms, CT scanning and high-quality video recording) and novel field-based approaches (i.e. studies of upwelling and CO2 vent regions) that may allow us to improve our predictive capacity of their vulnerability and/or resilience. In addition to playing a critical ecological and biogeochemical role, pteropods can offer a significant value as an early-indicator of anthropogenic OA. This role as a sentinel species should be developed further to consolidate their potential use within marine environmental management policy making.

Continue reading ‘Shelled pteropods in peril: Assessing vulnerability in a high CO2 ocean’

Aerobic and behavioral flexibility allow estuarine gastropods to flourish in rapidly changing and extreme pH conditions

Despite efforts to understand marine organismal responses to ocean acidification (gradual change in pH/ pCO2pCO2 over decades), there is a lack of information about the capabilities of coastal organisms to endure rapid and extreme pH change (often full units within hours). We predicted that gastropods faced with estuarine acidification avoid extreme pH exposure through isolation and/or escape behavior, and energetically compensate for feeding and energy uptake limitations by facultative metabolic depression (FMD). To test this, we studied behavioral (organism activity) and aerobic (cardiac performance) responses to acidification in two closely related tropical intertidal species, the estuarine Indothais gradata (two populations) and the open-shore Reishia bitubercularis. Snails were exposed in the laboratory to either acutely declining or stable low pH conditions, using two acidification modes (HNO3-acidification and CO2-aeration). Under acutely declining pH, aerobic performance was regulated to unexpectedly low pH levels (4.5), effectively extending the field pH range for activity. This pH performance threshold marked the onset of behavioral isolation and FMD (as opposed to respiratory stress) and was lower in Indothais than Reishia snails during mineral acidification. Behavioral (in isolated gastropods) and environmental hypercapnic acidosis complicates interpretation of lowered metabolic performance. Stable reduced pH exposures resulted in different behavioral and physiological responses by the Indothais populations, including more prominent escape from water in the seaward population. Overall, these results suggest that aerobic and behavioral flexibility are crucial to organismal fitness in widely fluctuating pH circumstances. They further warn against overgeneralizing marine acidification consequences across physiological dispositions, taxonomic levels, and ecological systems.

Continue reading ‘Aerobic and behavioral flexibility allow estuarine gastropods to flourish in rapidly changing and extreme pH conditions’

Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure

The gymnosome (unshelled) pteropod Clione limacina is a pelagic predatory mollusc found in polar and sub-polar regions. It has been studied for its distinctive swimming behavior and as an obligate predator on the closely related thecosome (shelled) pteropods. As concern about ocean acidification increases, it becomes useful to compare the physiological responses of closely-related calcifying and non-calcifying species to acidification. The goals of this study were thus to generate a reference transcriptome for Clione limacina, to expose individuals to CO2 for a period of 3 days, and to explore differential patterns of gene expression. Our Trinity assembly contained 300,994 transcripts of which ~ 26% could be annotated. In total, only 41 transcripts were differentially expressed following the CO2 treatment, consistent with a limited physiological response of this species to short-term CO2 exposure. The differentially expressed genes identified in our study were largely distinct from those identified in previous studies of thecosome pteropods, although some similar transcripts were identified, suggesting that comparison of these transcriptomes and responses may provide insight into differences in responses to ocean acidification among phylogenetically and functionally distinct molluscan lineages.

Continue reading ‘Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure’

Ocean acidification and warming impacts the nutritional properties of the predatory whelk, Dicathais orbita

Ocean warming and acidification have the potential to impact the quality of seafood with flow on effects for future food security and ecosystem stability. Here, we used a 35-day experiment to evaluate how ocean warming and acidification may impact the nutritional qualities and physiological health of Dicathais orbita, a predatory muricid whelk common on the east coast of Australia, and discuss the broader ecological implications. Using an orthogonal experimental design with four treatments (current conditions [~ 23 °C and ~ 380 ppm of pCO2], ocean warming treatment [~ 25 and ~ 380 ppm of pCO2], ocean acidification treatment [CO2 ~ 23 °C and ~ 750 ppm of pCO2], and ocean warming and acidification treatment [CO2, ~ 25 °C and ~ 750 ppm of pCO2]), we showed that changes in moisture and protein content were driven by significant interactions between ocean warming and acidification. Elevated ocean temperature significantly decreased protein in the whelk flesh and resulted in concurrent increases in moisture. Lipid, glycogen, potassium, sulfur, and phosphorus content also decreased under elevated temperature conditions, whereas sodium, boron and copper increased. Furthermore, elevated pCO2 significantly decreased lipid, protein and lead content. Whelks from control conditions had levels of lead in excess of that considered safe for human consumption, although lead uptake appears to be lowered under future ocean conditions and will be site specific. In conclusion, while D. orbita has received research attention as a potential food product with nutritious value, ocean climate change may compromise its nutritional qualities and reduce sustainable harvests in the future. Furthermore, ocean climate change may have deleterious impacts on the longevity and reproductive potential of this important rocky shore predator.

Continue reading ‘Ocean acidification and warming impacts the nutritional properties of the predatory whelk, Dicathais orbita’

Biodiversity of gastropoda in the coastal waters of Ambon Island, Indonesia

Gastropods belonging to the mollusk phylum are widespread in various ecosystems. Ecologically, the spread of gastropoda is influenced by environmental factors, such as temperature, salinity, pH and dissolved oxygen. This research was conducted to determine the correlation between the factors of physico-chemical environment and the diversity of gastropoda in coastal water of Ambon Island, Indonesia. This research was conducted at two research stations, namely Station 1 at Ujung Tanjung Latuhalat Beach and Station 2 at coastal water of Waitatiri Passo. The results of a survey revealed that the average temperature on station 1 was 31.14°C while the average temperature of station 2 was 29.90°C. The average salinity at Station 1 was 32.02%o whereas the salinity average at Station 2 was 30.31%o. The average pH in station 1 and 2 was 7.03, while the dissolved oxygen at station 1 was 7.68 ppm which was not far different from that in station 2 with the dissolved oxygen of 7.63 ppm. The total number of species found in both research stations was 65 species, with the types of gastropoda were found scattered in 48 genera, 19 families and 7 orders. The most commonly found gastropods were from the genus of Nerita and Conus. 40 species were found in station 1 and 40 species were found in station 2. The results of the analysis showed the diversity value was very high with the diversity average of gastropoda in station 1 as much as 3.64 and in station 2 as much as 3.60 and classified into moderate category. In addition, the results of the correlation analysis showed that there was a significantly positive correlation between physical-chemical environmental factors (temperature, salinity, pH and dissolved oxygen) and the diversity of gastropoda in Coastal Waters of Ambon Island.

Continue reading ‘Biodiversity of gastropoda in the coastal waters of Ambon Island, Indonesia’

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Ocean acidification in the IPCC AR5 WG II

OUP book