WILL GLOBAL ENVIRONMENTAL CHANGES INFLUENCE PRODUCTION AND PRESERVATION OF LARGER BENTHIC FORAMINIFERAL SHELLS IN CARBONATE SEDIMENTS?

The shells of larger foraminifers are major contributors to carbonate sediments on subtropical and tropical beaches, reefs, shelves and oceanic banks worldwide. All of these environments are being affected by anthropogenically driven environmental changes; some more than others. Categories of environmental change include a) land use and nitrogen fixation that have altered sediment delivery and doubled the rate of nutrient flux to the oceans, b) stratospheric ozone depletion such that intensities of biologically damaging ultraviolet radiation now reaching the sea surface between April and August at temperate and subtropical latitudes were reached only around the summer solstice in 1960s, and c) rapidly increasing concentrations of atmospheric carbon dioxide is resulting in both climate change and ocean acidification. Not only are a myriad of physical, chemical and biological changes associated with each of these categories, but interactions among them and with local factors result in an often overwhelming complex of stressors. Foraminifers are finding increasing application in environmental research. I shall present case studies of larger foraminifers indicating that a) increased nutrient flux can result in changes in carbonate sediment composition, b) similarities and differences in responses to photo-oxidative stress (bleaching) between larger foraminifers and zooxanthellate corals can enhance prediction of reef resiliency, and c) ocean acidification may already be influencing calcification rates some larger foraminifers. Most pertinent to the session theme, all of these factors can compromise preservation potential of foraminiferal shells.