The locations of the McKee-Mendelssohn team's 18 ground study sites across the Barataria-Terrebonne basin. (Click to enlarge)
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The locations of the McKee-Mendelssohn team's 18 ground study sites across the Barataria-Terrebonne basin. (Click to enlarge) |
Led by Karen McKee, a wetland ecologist with NWRC; IrvMendelssohn, an ecologist with Louisiana State University (LSU),;and Mike Materne, plant material specialist with NRCS, a team of investigators secured emergency funding from the Sea Grant program and immediately established 21 sampling stations (18 brown marsh sites and 3
control sites) in the fall of 2000. The team accessed sites by helicopter and measured percent plant cover by species and condition (live, standing dead, or stubble). To identify potential causes of plant dieback, they assayed the soils for texture, salinity, pH, redox potential, hydration, metals, toxins such as sulfide, and a variety of pathogens (work conducted by Ray Schneider, plant pathologist at LSU).
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Even at this early stage, however, it soon |
Even at this early stage, however, it soon became clear that there would be no single "smoking gun" in this ecological mystery. Instead, it was this field work that led to the working hypothesis that McKee and Mendelssohn would pursue in their subsequent search for causes in the laboratory: there was an additive--if not synergistic--interplay of factors at work, some combination of causes behind the phenomenon.
 The both the dehydrated soil and elevated metals that McKee and Mendelssohn observed and measured are seen above. The reddish coating seen at the base of the plant is oxidized iron, i.e. "rust," and vividly indicates the heightened level of iron they found in the soil. (Click to enlarge) |
An added bonus of having arrived on the scene so early was the opportunity it afforded the McKee-Medelssohn-Materne team to track the brown marsh trend across time. Although three sites had recovered completely by the close of 2001, five had recovered to a moderate degree, five had recovered only slightly, and five showed no recovery whatsoever. In other words, roughly 60% of the marsh in the team's sample tracts had shown little to no recovery.
Given these numbers, however, the "glass-is-half-full" perspective also meant that nearly half the marsh had rebounded fairly well of its own accord over the course of a year. But as tempted as they and other researchers may have been to investigate why some areas had recovered naturally and some had not, everyone involved with the project realized that the central question still remained and, of necessity, had to be answered first-what had caused the brown marsh phenomenon in the first place?
 Click to enlarge |