Combined effects of seawater acidification and salinity changes in Ruditapes philippinarum

• Published in: Aquatic toxicology 2016-07, Vol.176, p.141-150
• Main Authors: Velez, Catia, Figueira, Etelvina, Soares, Amadeu M.V.M., Freitas, Rosa
• Format: Article
• Language: English
• Subjects: Animals; Biomarkers - metabolism; Bivalvia - physiology; Clams; Climate change; Hydrogen-Ion Concentration; Marine; Oxidative Stress; pH decrease; Physiological and biochemical performance; Ruditapes philippinarum; Salinity; Seawater - chemistry
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2016.04.016

•Under control pH (7.8) low salinity (14) induced oxidative stress in R. philippinarum.•Under pH 7.8 and salinity 35 clams showed no alterations compared to control salinity (28).•Clams under pH 7.3 were able to maintain their physio and biochemical performance among salinities.•At each salinity similar responses were found in clams under both pH levels.•Our results indicate that pH may have less impact on clams than salinity. Due to human activities, predictions for the coming years indicate increasing frequency and intensity of extreme weather events (rainy and drought periods) and pollution levels, leading to salinity shifts and ocean acidification. Therefore, several authors have assessed the effects of seawater salinity shifts and pH decrease on marine bivalves, but most of these studies evaluated the impacts of both factors independently. Since pH and salinity may act together in the environment, and their impacts may differ from their effects when acting alone, there is an urgent need to increase our knowledge when these environmental changes act in combination. Thus, the present study assessed the effects of seawater acidification and salinity changes, both acting alone and in combination, on the physiological (condition index, Na and K concentrations) and biochemical (oxidative stress related biomarkers) performance of Ruditapes philippinarum. For that, specimens of R. philippinarum were exposed for 28days to the combination of different pH levels (7.8 and 7.3) and salinities (14, 28 and 35). The results obtained showed that under control pH (7.8) and low salinity (14) the physiological status and biochemical performance of clams was negatively affected, revealing oxidative stress. However, under the same pH and at salinities 28 and 35 clams were able to maintain/regulate their physiological status and biochemical performance. Moreover, our findings showed that clams under low pH (7.3) and different salinities were able to maintain their physiological status and biochemical performance, suggesting that the low pH tested may mask the negative effects of salinity. Our results further demonstrated that, in general, at each salinity, similar physiological and biochemical responses were found in clams under both tested pH levels. Also, individuals under low pH (salinities 14, 28 and 25) and exposed to pH 7.8 and salinity 28 (control) tend to present a similar response pattern. These results indicate that pH may have a lower impact on clams than salinit