T130 Quaternary Micropaleontology: Quantifying Environmental Change

Tuesday, 24 October 2006
8:00 AM - 12:00 PM

THE MARTYRDOM OF ST. LUCIE: THE IMPORTANCE OF A BASELINE FAUNAL ASSESSMENT

Paper number: T130-12
Program: Technical Sessions
Time: 10:25 AM – 10:40 AM

Authors

Abstract

St. Lucie, the southernmost inlet of the Indian River Lagoon, is affected by a variety of stresses including dumping from Lake Okeechobee, the second-largest freshwater lake in the U. S., through a system of canals. In 2005 a particularly large discharge of fresh pollutant-saturated water resulted in losses of seagrass, bivalves, and diseased and dying fish. A program to monitor the macrofauna and assess its future is now underway. A comparison with the past, of course, is only possible if a baseline exists. Unlike the macrofauna, in 1975/76, such a baseline was established for the foraminifera. Thirty years later in 2005, the same area was re-sampled for foraminifera. In 1975/76 the mean density was 280 per 20 ml of sediment. In 2005, we observed a mean of 46 per 20 ml of sediment, a decline of 83%. In 1975/76 we observed 62 species while in 2005 we observed 13, a decline of 79%. The most abundant species constituted 42% of the fauna in 1975/76; in 2005 it had risen to 76%, a dramatic increase in dominance. The dramatic difference between the baseline and the present is plotted on a biodiversity gram (BDG) which depicts the canonical ensemble of species richness, compound diversity and evenness against the number of individuals on a single diagram.