Modern seawater acidification: the response of foraminifera to high-CO 2 conditions in the Mediterranean Sea

The seas around the island of Ischia (Italy) have a lowered pH as a result of volcanic gas vents that emit carbon dioxide from the sea floor at ambient seawater temperatures. These areas of acidified seawater provide natural laboratories in which to study the long-term biological response to rising CO 2 levels. Benthic foraminifera (single-celled protists) are particularly interesting as they have short life histories, are environmentally sensitive and have an excellent fossil record. Here, we examine changes in foraminiferal assemblages along pH gradients at CO 2 vents on the coast of Ischia and show that the foraminiferal distribution, diversity and nature of the fauna change markedly in the living assemblages as pH decreases.