William H. Orem¹, Susan Newman², Dale E. Gawlik³, Debra Willard¹, Harry E. Lerch¹,
Anne L. Bates¹ and Margo D. Corum^1
1U.S. Geological Survey, National Center, Reston, VA, USA
²South Florida Water Management District, West Palm Beach, FL, USA
³Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL, USA

One of the principal goals of Everglades’ restoration is to reestablish hydrologic conditions within the ecosystem favorable for native biota to flourish. Wading birds are a key group of biological indicators that were used to identify good historic hydrologic conditions. One reason this group was so useful for understanding historic hydrologic conditions was that it was the subject of a long running data base. The first wood stork nest surveys were conducted in 1903 and thereafter, some measure of nesting effort was recorded in most years. Despite this long record of data, the surveys are limited in that even the first survey occurred after hydrologic modifications to the Everglades were underway. Also the spatial coverage was restricted to the coastal edge of the Everglades, where nesting colonies were known to exist and where they could be accessed by boats. The usefulness of the wading bird nesting data base could be greatly enhanced if there was some measure of temporal fluctuations prior to human alteration of the system and some measure of spatial extent of colonies beyond the accessible coastal areas.

The principal objective of this study was a preliminary examination of potential geochemical markers (biomarkers) of wading birds suitable for developing a chronology. Previous work by the U.S. Geological Survey had shown that tree island soils contain high levels of phophorus, hypothesized to originate from wading bird guano. Thus, tree island soils may contain an historical record of wading bird numbers from accumulated bird guano. We examined potential organic biomarkers in wading bird guano (Great Egret, Great Blue Heron, Little Blue Heron) collected from throughout the ecosystem. Markers of particular interest included: uric acid, various fatty acids, and various sterols. Soil cores collected from beneath a wading bird nesting colony on Rescue Strand tree island (northern water Conservation Area 3) were examined for the same suite of organic biomarkers examined in the guano samples. Soil samples from a marsh core (representing a background site) were also examined for these organic biomarkers. Organic markers identified in the guano samples were also identified in the tree island soil core, but not in the background marsh core. Uric acid, in particular, has potential as a biological marker of wading birds.

Contact Information: William H. Orem, U.S. Geological Survey, 956 National Center, Reston, VA 20192 USA, Phone: 703-648-6273, Fax: 703-648-6419, Email: borem@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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