Marine ecosystem response to Mesozoic warming events

Predicting how marine ecosystems will respond to current climate change is a key scientific challenge. The fossil record of past warming events provides us with a means to test these predictions on local, regional and global scales, under a variety of different starting conditions, and with different magnitudes and rates of change. Marine biologists are particularly concerned with variables such as oxygen, temperature, pH and productivity, and how they may affect the diversity and functioning of marine ecosystems and the body size of marine animals. Using fossil and geochemical data from Mesozoic global warming events, we can test several of these predictions. Predictions that higher temperatures lead to lower levels of dissolved oxygen and smaller body sizes in marine animals are well supported by the fossil data. Changes in certain animal groups have implications for nutrient cycling and productivity. Direct evidence that pH became sufficiently low during these events to impair calcification in marine animals is lacking. To better understand these past events, we need to build multidisciplinary, high-resolution datasets, using the same samples from the same study sites, that combine palaeontological data and geochemical proxy data, so that relationships between environmental change and biological response can be properly tested using multivariate analyses and, potentially, at sub-millennial timescales.