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Benthic diatom composition in isolated forested wetlands subject to drying: implications for monitoring and assessment
Citation:
LANE, C. R., K. Reiss, SUSANNA J. DECELLES, AND M. T. Brown. Benthic diatom composition in isolated forested wetlands subject to drying: implications for monitoring and assessment . ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 9(6):1121-1128, (2009).
Impact/Purpose:
The EPA Office of Water has recognized a critical need for states and federal agencies to be able to quantitatively assess the condition of the Nation’s wetland resources. Currently, >85% of states, tribes, and territories are lacking even rudimentary biological assessment methodologies for wetlands. Additional important needs identified include obtaining base line nutrient and physical/chemical conditions to aid in understanding the role of wetland systems (isolated wetlands in particular) in ensuring aquatic life and beneficial uses of lakes, rivers, and streams in the watershed. To address these challenges, the following research on isolated wetlands is proposed: Within a region, 1) Develop a probabilistic sampling design that stratifies isolated wetlands by type and size (also targeting reference conditions); 2) Collect biotic data using macroinvertebrates, macrophytes, and diatoms; 3) Collect abiotic (water and soil chemistry) data to establish base line conditions, quantify wetland contribution to landscape nutrient dynamics, and establish a spectral library for future rapid assessment of nutrient sequestration abilities of isolated wetlands; 4) Assess wetland condition with Level 1 (geographic information systems - GIS) and Level 2 (rapid assessment) characterization methods; 5) Develop metrics and correlate biotic signature to local and landscape assessments; 6) Report on the condition of systems across region and recommend assessment methods to states and tribes; 7) Model isolated wetland contribution to landscape nutrient dynamics based on analyses using visual and near-infrared spectrometer (VNIRS) data. Key outputs for regions and states from the proposed research include: tools for remote GIS-based assessment, tools for rapid on-site assessment, and tools for intensive biological assessment of isolated wetlands; comparison between local and landscape assessment measures; functional assessment of isolated wetland contribution to landscape nutrient dynamics (using VNIRS); baseline water and soil physical/chemical conditions; baseline flora and fauna of isolated wetland systems; and a fuller understanding of watershed condition and regional environmental health.
Description:
The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological indicator of wetland condition in isolated forested wetlands of Florida, USA, 11 wetlands were sampled twice during a six month period, once when hydrated and once when dry. Dry sites had significantly higher diatom taxa richness at genus and species levels. Non-metric multidimensional scaling and multiple response permutation process analyses resulted in no obvious or significant wet/dry grouping of abuncance data. Five of seven diatom metrics of the Florida Wetland Condition Index (FWCI) for depressional forested wetlands were significantly linearly correlated, while only one of seven metrics (a dissolved-oxygen indicator) had a significantly different mean in paired t-test analyses. The final FWCI was significantly correlated between wet and dry sites, and no difference was found in mean FWCI score between wet and dry sites, and no difference was found in mean FWCI score between wet and dry sites, suggesting that benthic diatoms can be used to monitor and assess wetland condition regardless of season or site hydrologic conditions.