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Longitudinal variation and response to anthropogenic stress in diatom assemblages of the Lower Mississippi River, USA
Citation:
Bellinger, B., E. Reavie, T. Angradi, D. Bolgrien, T. Jicha, AND B. Hill. Longitudinal variation and response to anthropogenic stress in diatom assemblages of the Lower Mississippi River, USA. River Systems. E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany, 21(1):29-54, (2013).
Impact/Purpose:
This paper advances the scientific bases for assessing environmental conditions of the lower Mississippi River using algal assemblages. Such information is needed to understand, and then manage, nutrient loads from the watershed to the river and then from the river to the Gulf of Mexico
Description:
The Lower Mississippi River (LMR), below the confluence with the Ohio River, drains over 40% of the continental United States and is an important resource for anthropogenic and biotic use, both within the system and in the receiving Gulf of Mexico. As part of the National Rivers and Streams Assessment (NRSA) by the United States Environmental Protection Agency (USEPA), we used a common bioindicator, diatoms, to link assemblage structure with land cover and water quality by applying multivariate analyses, and European- and regionally-derived models. Periphytic (attached) and planktonic (free floating) diatom assemblage structure were related to land cover, notably sub-catchment development and agriculture, and variation in water salinity. Scale of land cover delineation (e.g., short-spatial area, watershed) was important in relation to diatom assemblage structure. European metric scores of ecological integrity classified the LMR as eutrophic as well as generally polluted, but indices were not well correlated with land cover or water quality metrics. A regionally derived stressor model corroborated the LMR as being highly eutrophic and influenced by high agriculture and development in the basin. Site score variability was small relative to the Upper Mississippi River Basin. Our study of the LMR corroborates diatom assemblages as effective indicators of physico-chemical stress, validating their use in large river assessments. Our data provide a robust baseline for future comparison of both biotic and abiotic condition of the LMR.
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Longitudinal variation and response to anthropogenic stress in diatom assemblages of the Lower Mississippi River, USA