Influence of CO2-induced seawater acidification on the development and lifetime reproduction of Tigriopus japonicus Mori, 1938

摘要

Ocean acidification is changing the carbonate system of the world's oceans and has been driving all marine organisms to live in increasingly acidic environments. Tigriopus japonicus is an ideal standard test animal in sea water. In the present study, we investigated the influence of carbon dioxide (CO2)-induced seawater acidification on the development and lifetime reproduction of T. japonicus to accumulate basic data for assessing the potential impact of ocean acidification. The harpacticoid copepods were exposed in seawater equilibrated with CO2 and air to reach pH 8.0 (control), 7.7 (the predicted ocean pH by 2100), 7.3 (the predicted ocean pH by 2300) and 6.5 (an extreme condition relevant to industrial acid waste discharge or leakage from CO2 seabed storage). Survival was found to be unaffected following the 56 day exposure period. Significant retardation of development rates of the nauplius stage was observed at pH 6.5, while the development time of the copepodite stage was unaffected. Acidification did not affect the number of broods but it significantly reduced the hatching success of egg sacs at pH 6.5. Total production of nauplii over the lifetime of female copepods was significantly reduced at pH 7.3. Over successive broods, nauplius production was significantly affected by exposure time, pH and their interaction. Shedding of unhatched egg sacs by females mainly occurred in the late breeding stage at pH 7.3 and 6.5. Our results indicated that T. japonicus adults are tolerant to the ocean acidification conditions predicted for the year 2100, but the early development and reproductive capacity of females could be impaired by long-term exposure to more severe acidification conditions (pH 7.3 and 6.5). More long-term studies on a wider range of copepod species from different taxa and different marine habitats are urgently required to predict the fate of marine copepod communities in future oceans.