After six months exposure, warmer temperatures, but not ocean acidification, significantly reduced the shell strength of blue mussels, which were fed for a limited period of only 4-6 hours per day. The rising temperatures seemed to affect shell strength indirectly, as the mussels apparently re-allocated energy from shell formation to maintain their bodies in the warmer temperature; this tradeoff may have been especially important in this study because the mussels were given limited access to food and therefore energy. The maintenance of shell strength despite seawater acidification suggests that formation of blue mussel shells may not be affected by ocean acidification. (Laboratory study)