Heat stress in the intertidal: comparing survival and growth of an invasive and native mussel under a variety of thermal conditions.

In the rocky intertidal, organisms frequently experience a wide range of daily body temperatures depending on the stage of the tide and the time of day. In the intertidal, the thermal adaption of a species and its ability to invade a new region may be closely linked. In this research, the physiological effects of thermal stress in both low tide and high tide conditions are compared between Mytilus galloprovincialis, a worldwide mussel invader, and M. trossulus, a sibling species. In a seawater tank, mussels were exposed to one of three aerial temperature treatments (20, 25, 30 degrees C) in a cycle with one of two water temperatures (18, 12 degrees C). In 18 degrees C water, there was no effect of the aerial treatments on growth or survival in either species. In contrast, in 12 degrees C water, aerial exposure affected the survival and growth of both species. Growth and survival rates of M. galloprovincialis were higher in all conditions than the rates of M. trossulus, especially in the 18 degrees C water experiments and in the aerial exposure treatments of the winter 12 degrees C water experiment. M. galloprovincialis appears to be warm-adapted with regard to both low tide and high tide thermal stress. These results when paired with previous research suggest that as climates shift due to global warming, the temperatures favorable to M. galloprovincialis will become more common.