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Abstract

THE MARTYRDOM OF ST. LUCIE: DECIMATION OF A MEIOFAUNA

Lee-Ann C. Hayek and Martin A. Buzas
National Museum of Natural History
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St. Lucie, the southernmost inlet of 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. The foraminifera, a major component of the meiofauna, are utilized as a source of nutrition by a wide variety of deposit feeders in this area. Just as pollutants, spills and organic enrichment are obvious sublethal effects of estuarine health, so too is the disappearance of organisms constituting essential links in the food chain. Because the meiofauna is at the base of the food chain, the consequences of major declines and local extinctions clearly are indicators of serious damage to the health of the entire ecosystem. To establish a baseline, foraminiferal density, species richness, evenness and community structure were examined in 1975/1976. Thirty years later in 2005, the same area was sampled again. In 1975/1976 the mean density was 280 per 20 ml of sediment. In 2005, we observed a mean of 46 per 20 ml, a decline of 83%. In 1975/1976, we observed 62 species while in 2005 we observed 13, a decline of 79%. The most abundant species constituted 42% of the fauna in 1975/1976; in 2005 it had risen to 76%, a dramatic increase in dominance. Based upon our newly-developed 3-stage evaluation system of ecosystem decline over time, we find that the St Lucie area is nearing, if not at the beginning of Stage 3 (local extinction).