Preparing the next generation for climate change: parental effects on larval thermal tolerance in the Pacific blue mussel (Mytilus trossulus)

Abstract

As ocean and atmospheric temperatures increase globally, marine organisms will need to cope with or adapt to changing temperatures in order to persist. This is especially important in sessile species which cannot move to avoid stress. Parental effects, where offspring responses to environmental change are influenced by environments experienced by parents, may include mechanisms of coping with thermal stress. This study evaluated the degree to which thermal tolerance of larvae of the mussel, Mytilus trossulus, is influenced by parental environments. Adult mussels were collected from two sites of varying thermal stress on San Juan Island: Friday Harbor Laboratories dock (low stress) and False Bay (high stress). Air, water, and body temperatures were recorded in the field, and thermal tolerance (LT50) trials were conducted on adults and on their veliger larvae raised in the laboratory. Thermal tolerance was higher in adults from the high stress environment than those from the low stress site. For mussels from the FHL site, larval thermal tolerance was ~2°C higher than that of the adults. The opposite was found for mussels and their larvae from FB. Larval tolerances were higher for mussels from the low stress environment. This study concluded that thermal acclimation may have occurred in the two study populations. In addition, larvae of parents from the high-stress environment may be more susceptible to thermal stress than those from low-stress parents. Finally, larval tolerances were similar to or higher than adult thermal tolerances which suggests larvae may not be as vulnerable as suspected.