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Spatial Assessment of a Biocriteria Applied to Texas Tidal Streams

DOI: 10.1155/2013/726594

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Abstract:

This study reports on a derived multivariate method for assessing ecosystem health within tidally influenced portions of river basins and coastal basins. These tidally influenced areas are highly productive transitional areas which serve as important nursery areas for many fish and shellfish species. Numerous Texas tidal streams under varying degrees of anthropogenic stressors were analyzed jointly with this new, standardized methodology. Physical and chemical constituents of the tidal systems, as well as their resident nekton communities, were compared with nonparametric ordination techniques in order to uncover a biocriteria that might have general applicability over large spatial scales. All of the tidal stream communities were dominated by only a few taxa that each displays tremendous euryhaline/physiological tolerances, and these abilities allow taxa utilizing tidal streams to adapt to a wide variety of environmental stressors. The absence of any clear connections between degraded water-bodies and any impaired nektonic communities should not automatically be viewed as a constraint inherent to the techniques of the methodology presented, but rather a verification that impaired tidal streams are not that common of an occurrence along the Texas coast, at least not when using nekton communities as the degradation indicator. 1. Introduction Tidal streams are highly productive transitional areas found in the mixing zones between the freshwater of the rivers and the increased salinities found within the estuary. Tidal streams also serve as important nursery areas for many fish and shellfish species, and a number of species have been shown to actively recruit to these important habitats [1–4]. Routine monitoring of several tidally influenced segments throughout the state of Texas has revealed that water quality standards are not currently being met (Texas Commission on Environmental Quality (TCEQ), 2010 [5]). Listed tidal segments, routinely cited as having increased bacterial loads and depressed dissolved oxygen measurements, and these excursions of low dissolved oxygen waters could have a detrimental effect on the early life history stages of finfish and shellfish utilizing these nursery areas. Water quality management of these areas has been difficult because currently there are no statewide criteria for assessing tidally influenced waterbodies, and these systems are naturally quite variable over time and space [6]. Inclusion on this impaired waterbody list initiates the total maximum daily load (TMDL) process. As a first step, it is necessary to assess

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