Sublethal effects on the hard clam Mercenaria mercenaria after exposure to Aureococcus anophagefferens Chinese strain isolates

Abstract

Brown tides caused by Aureococcus anophagefferens occur frequently worldwide and have contributed to the collapse of Mercenaria mercenaria farming in the United States. This economically valuable hard clam has been used in China for more than 20 years. To date, it has remained unknown whether A. anophagefferens Chinese strain has an impact on hard clam cultivation in the coastal areas of China or other sea areas worldwide if it enters through ship ballast water and other ways. In this study, a Chinese strain of A. anophagefferens isolated from the brown tide waters of Bohai Bay, China, was selected to explore its influence on the feedback of hard clams. After being fed with A. anophagefferens, hard clams showed characteristics similar to starvation. The reduced feeding efficiency of hard clams leads to reduced energy intake. However, the immune response and oxidative stress, result in increased energy consumption. An imbalance in the energy budget may be an important reason for hard clam starvation. This study has described the response characteristics of the A. anophagefferens Chinese strain to M. mercenaria, explored the reasons for the negative impact of A. anophagefferens on hard clams, and provides ideas for reducing shellfish aquaculture caused by brown tides.

Keywords: Aureococcus anophagefferens; Immune responses; Mercenaria mercenaria; Oxidative stress; Sublethal effects.