Soil and periphyton indicators of anthropogenic water-quality changes in a rainfall-driven wetland

P. V. McCormick
Leetown Science Center, United States Geological Survey, Kearneysville, WV 25430, USA

P. V. McCormick
Lake Okeechobee Division, South Florida Water Management District, P.O. Box 24680, West Palm Beach, FL 33416-4680, USA
e-mail: pmccormi@sfwmd.gov

Received: 6 August 2009 / Accepted: 19 July 2010 / Published online: 31 July 2010

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Surface soils and periphyton communities were sampled across an oligotrophic, soft-water wetland to document changes associated with pulsed inputs of nutrient- and mineral-rich canal drainage waters. A gradient of canal-water influence was indicated by the surface-water specific conductance, which ranged between 743 and 963 µS cm-1 in the canals to as low as 60 µS cm-1 in the rainfall-driven wetland interior. Changes in soil chemistry and periphyton taxonomic composition across this gradient were described using piecewise regressions models. The greatest increase in soil phosphorus (P) concentration occurred at sites closest to the canal while soil mineral (sulfur, calcium) concentrations increased most rapidly at the lower end of the gradient. Multiple periphyton shifts occurred at the lower end of the gradient and included; (1) a decline in desmids and non-desmid filamentous chlorophytes, and their replacement by a diatom-dominated community; (2) the loss of soft-water diatom indicator species and their replacement by hard-water species. Increased dominance by cyanobacteria and eutrophic diatom indicators occurred closer to the canals. Soil and periphyton changes indicated four zones of increasing canal influence across the wetland: (1) a zone of increasing mineral concentrations where softwater taxa remained dominant; (2) a transition towards hard-water, oligotrophic diatoms as mineral concentrations increased further; (3) a zone of dominance by these hard-water species; (4) a zone of rapidly increasing P concentrations and dominance by eutrophic taxa. In contrast to conclusions drawn from routine water-chemistry monitoring, measures of chemical and biological change presented here indicate that most of this rainfall-driven peatland receives some influence from canal discharges. These changes are multifaceted and induced by shifts in multiple chemical constituents.

Everglades, Mineral, Periphyton, Phosphorus, Soil, Specific conductance, Water quality, Wetlands