STUDIES OF LIVING MARSH FORAMINIFERA TO ENHANCE THEIR USEFULNESS AS PALEOENVIRONMENTAL INDICATORS

Salt marshes have extreme environmental variation of most physical parameters because of exposure times, especially in the upper limits. Few species of foraminifera survive there but they are distributed in discrete vertical zones worldwide. Additionally, they have a very long geologic history, with the first forms, similar to modern ones, found in Cambrian rocks in Nova Scotia (over 500 million years old). These species are resilient but do become stressed when they encounter certain intense environmental stressors, such as some types of pollution or extreme climates in polar areas. However, other than indirect evidence from examining distributions in natural settings, we know little about the exact stressors that inhibit life functions such as reproduction. Few biologic studies of marsh foraminifera have been done so little is known regarding environmental stress as limiting factors in these forms. In this study we use a controlled climate marsh system in which individual aspects of the marsh environment can be modified; this allows us to isolate certain factors that cannot be done in a natural setting. Preliminary results show our marsh system is similar to the natural environment and surprisingly still undergoes its own seasonal cycles of foraminiferal assemblages and plant growth. We can easily manipulate temperature, salinity and other variables to examine foraminiferal responses. Transmission Electron Microscopy allows us to look at individual specimens and determine their preferred food sources (a major question that has never been answered) and determine what triggers reproductive events. We know from one controlled field experiment that these foraminifera do respond negatively to relatively small amounts of petroleum (i.e. oil spills) by forming irregular tests; this response was also reproduced in the laboratory. We have also frozen pieces of living marsh for up to 3 months and found that foraminifera could survive up to 6 weeks of being frozen. Marshes are critical areas of high productivity; foraminiferal assemblages provide a proxy that is useful throughout the entire Phanerozoic-the present work gives marsh foraminifera even more potential to provide important paleoenvironmental information for the last 500 million years