LARGER FORAMINIFERS AS INDICATORS OF GLOBAL ENVIRONMENTAL CHANGE

Human activities are altering marine environments globally. Ozone depletion has increased high energy, short wavelength radiation in the clearest euphotic environments. Rising concentrations of atmospheric carbon dioxide is likely responsible for climate changes, and is unquestionably responsible for declining carbonate saturation in aquatic systems. Human activities have doubled input of biologically available N, P and some trace nutrients into aquatic systems, with results ranging from community phase shifts to growing hypoxic zones. Rising temperatures and hypoxia are relatively easy to measure and their effects on marine communities are dramatic. Consequences of changes in solar radiation, nutrification, and declining carbonate saturation, in contrast, are more subtle and difficult to quantify or distinguish from natural variability. In warm, shallow, benthic marine environments, larger foraminifers provide potential bioindicators for these more subtle environmental changes. Research on populations of Amphistegina, which are abundant worldwide, has documented the sensitivity of these foraminifers to nutrification and changes in solar energy reaching the seafloor, and their insensitivity to temperature changes as compared to zooxanthellate corals. Archaiasine foraminifers are now being recognized as potential bioindicators of declining carbonate saturation. Despite ancestors in the Indo-Pacific, this lineage of Mg-calcite secreting foraminifers experienced Neogene proliferation in the higher salinity, more carbonate saturated tropical western Atlantic waters as compared to those of the Indo-Pacific. In recent years, etched or partially dissolved tests have become common among archaiasines collected live from Florida (USA) reef environments. Just as the amphisteginids have proven useful as indicators of the consequences of changing solar energy reaching the seafloor, the archaiasines show promise as bioindicators of declining carbonate saturation.