Mercury is a hazardous pollutant in the Bohai marine environments due to its high toxicity to the marine organisms and subsequent ecological risk. Manila clam Ruditapes philippinarum is one of important sentinel organisms in 'Mussel Watch Program' launched in China and therefore used as a bioindicator in marine and coastal ecotoxicology. There are dominantly distributed three pedigrees of clam (White, Liangdao Red and Zebra) in Yantai population endowed with different tolerances to environmental stressors. In this study, gill tissues were collected from both untreated and mercury exposed White, Liangdao Red and Zebra clams, and the extracts were analyzed by NMR-based metabolomics to compare the original metabolomes and the toxicological effects induced by mercury exposure in three pedigrees. The major abundant metabolites in White clam sample were branchedchain amino acids, lactate, alanine, arginine, acetoacetate, glutamate, succinate, citrate, malonate and taurine, while the metabolite profile of Liangdao Red clam sample comprises relative high levels of alanine, arginine, glutamate, succinate and glycogen. For Zebra clam sample, the metabolite profile exhibited relatively high amount of aspartate, acetylcholine and homarine. After 48 h exposure of 20 lg l -1 Hg 2? , the metabolic profiles from all the three pedigrees of clams commonly showed significant increases in alanine, arginine, glutamate, aspartate, a-ketoglutarate, glycine and ATP/ADP, and decreases in citrate, taurine and homarine. The unique metabolic differences between the metabolomes of gill tissues from Hg 2? -exposed White, Liangdao Red and Zebra clams were found, including elevated acetylcholine and branched-chain amino acids in White clams, and the declined succinate in both White and Liangdao Red samples as well as the declined betaine in Zebra and White clams. Overall, our findings showed the differential toxicological responses to mercury exposure and that White clams could be a preferable bioindicator for the metal pollution monitoring based on the metabolic changes from gill compared with other two (Liangdao Red and Zebra) pedigrees of clams.

a b s t r a c tOcean acidification (OA), caused by anthropogenic CO 2 emissions, has been proposed as one of the greatest threats in marine ecosystems. A growing body of evidence shows that ocean acidification can impact development, survival, growth and physiology of marine calcifiers. In this study, the immune responses of the Pacific oyster Crassostrea gigas were investigated after elevated pCO 2 exposure for 28 days. The results demonstrated that OA caused an increase of apoptosis and reactive oxygen species (ROS) production in hemocytes. Moreover, elevated pCO 2 had an inhibitory effect on some antioxidant enzyme activities and decreased the GSH level in digestive gland. However, the mRNA expression pattern of several immune related genes varied depending on the exposure time and tissues. After exposure to pCO 2 at~2000 ppm for 28 days, the mRNA expressions of almost all tested genes were significantly suppressed in gills and stimulated in hemocytes. Above all, our study demonstrated that elevated pCO 2 have a significant impact on the immune systems of the Pacific oyster, which may constitute as a potential threat to increased susceptibility of bivalves to diseases.

No abstract