Shifting climate change research into Sydney Harbour – predictions for native and introduced species

As the climate warms and oceans are absorbing greater levels of carbon dioxide from the atmosphere, the estuarine environment is changing. It is predicted that ecological interactions between non-native and native species will... [ view full abstract ]

As the climate warms and oceans are absorbing greater levels of carbon dioxide from the atmosphere, the estuarine environment is changing. It is predicted that ecological interactions between non-native and native species will be affected by future climate change. The native hairy mussel, Trichomya hirsuta, is common on many intertidal rocky shores in Sydney Harbour. The introduced mussel, Mytilus galloprovincialis, is present in the harbour but its distribution and abundance is spatially and temporally patchy. Along with the mussels, species living within mussel beds will also be faced with an increasingly stressful environment. Using novel mesocosm experiments, manipulating temperature and CO2, this research investigated how native and introduced mussels, and the invertebrates colonising mussel beds will respond to future climate change. Preliminary findings have shown that clearance rates, subsequent rates of growth of mussels, and egg size were influenced by ocean acidification, temperature, and the presence of the other mussel species. The effect of CO2 was contingent on the species of mussel under investigation. For example, the introduced mussel, M. galloprovincialis showed little response to CO2. The native mussel, T. hirsuta, had increased clearance rates and produced larger eggs under elevated CO2, except when in tanks with M. galloprovincialis. These results are consistent with previous studies on ocean acidification, and suggest that the native mussel is able to give greater provisions to its offspring to survive in a stressful environment. The presence of the non-native species does, however, inhibit the ability for reproductive provisioning by T. hirsuta. Colonisation of native and non-native mussel beds occurred under all combinations of temperature and CO2. Findings will be discussed in terms of how future climate change and the presence of non-native species will influence native biodiversity in Sydney Harbour.