You are here:
DIATOMS AS INDICATORS OF ISOLATED HERBACEOUS WETLAND CONDITION IN FLORIDA, USA
Citation:
Lane, C R. AND M. T. BROWN. DIATOMS AS INDICATORS OF ISOLATED HERBACEOUS WETLAND CONDITION IN FLORIDA, USA. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 7(3):521-540, (2007).
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Benthic, epiphytic, and phytoplanktonic diatoms, as well as soil and water physical-chemical parameters, were sampled from 70 small (~1 ha) isolated depressional herbaceous wetlands located along a gradient of human disturbance in peninsular Florida to: 1) compare assemblage structure between types; 2) analyze the effects of ecoregion on diatom distribution; 3) develop biological indicators of wetland condition and ultimately an index of biological integrity using a single assemblage; and 4) examine autecological relationships between diatom structure and environmental variables. Collected diatom samples were enumerated to 250 valves and identified to species or subspecies. An on-site assessment of wetland condition was made using the Wetland Rapid Assessment Procedure (WRAP), and a landscape-scale human disturbance score (Landscape Development Intensity index, LDI) was calculated for each site using aerial photos and GIS. Compositional differences were found between samples from the same site, but no significant differences were found when comparing composition across sites. Results equivocated on differences in regional composition among types, suggesting possible dissimilarities between diatom flora of southern and northern Florida, driven by diversity within reference conditions. Impaired sites tended towards homogenization with increased disturbance. Metrics were developed using the full peninsular dataset. Mantel's test and non-metric multidimensional scaling (NMDS) identified epiphytic diatoms as the most responsive to human disturbance. Strong correlations were found between epiphytic NMDS scores and soil pH, specific conductivity, water total phosphorous, and LDI. Metrics to assess wetland condition were developed using epiphytic abundance data. Epiphytic taxa sensitive or tolerant to human landscape modification were identified using Indicator Species Analysis, and autecological indices relating diatom sensitivity to nutrients, pH, dissolved oxygen levels, saprobity, salinity, and trophic status were calculated. Fourteen final metrics were identified, scored on an ordinal scale, and combined into the Diatom Index of Wetland Condition (DIWC). The DIWC was highly correlated with both the WRAP and LDI scores (Spearman's rs = -0.68, p < 0.001 and rs = -0.71, p < 0.001, respectively), indicating the utility of epiphytic diatom taxa to assess isolated wetland condition in Florida.