The resilience of bivalves to environmental stress

Human activities and climate change are causing irreversible changes in almost all marine environments. In these changing environments, it is the resilience of organisms that may decide whether they succeed or fail. Marine bivalves are habitat forming organisms, the species they support are intrinsically linked to their distribution. This thesis sought to determine whether habitat forming bivalves will be resilient to stressors at a magnitude predicted for the next 100 years. To answer this overarching question, experiments were done to test hypotheses on how stressors will interact to affect bivalves. Oysters currently exist in Sydney Harbour despite a multiple stressor environment including the influence of anthropogenic pollution and construction. These stressors were found to be causing biological impacts at a local scale and influencing patterns of distribution of both native and invasive oysters in Sydney Harbour. How current and future stressors will interact to impact bivalve populations remains unknown. Climate change is predicted too warm and acidify the oceans, which will potentially exacerbate existing environmental stressors. Separate manipulative experiments found that both pollution from anthropogenic sources, and emersion of oysters at low tide will interact with climate change to have synergistically negative effects on the physiology and reproduction of oysters. Intertidal organisms such as oysters are predicted to be resilient. Deep sea organisms are, however, predicted to have a low capacity for resilience. Manipulative experiments on the deep sea bivalve Acesta excavata found that pollution and climate change will interact to cause negative effects on the physiology and energy budget of A. excavata. These results represent important findings into how oyster and other bivalve populations may behave in a future environment that is heavily influenced by anthropogenic practices