Abstract
ABSTRACTEvaluations of the composition and biomass of photoautotrophic periphyton, nutrient concentrations of water, and concentrations of total phosphorous of benthic organic matter at eight stream sites in Middle Tennessee were used to: (1) document the composition of soft-algae and diatom assemblages, (2) assess the trophic state of the stream sites, (3) correlate trophic state to percent composition of soft-algae taxa, and (4) construct biotic indices using soft-algae taxa to help monitor trophic state. The concentration of total phosphorous of benthic organic matter was a more accurate indicator of the trophic state of the stream sites we studied relative to nutrient concentrations of water as demonstrated by correlation coefficients for nutrient concentrations to benthic concentrations of chlorophyll a, ash-free dry mass of benthic organic matter, and biotic indices which denote trophic state using diatom and soft-algae taxa. The algae trophic index developed using soft-algae taxa abundance-weighted averages of benthic concentrations of chlorophyll a correlates significantly to all of the benthic characteristics used to denote trophic state. This index is the first to utilize periphyton characteristics, as opposed to nutrient concentrations of water, to assign trophic-indicator values to soft-algae taxa in lotic systems and does not require a computer program to compute.
Highlights
Algae are a major component of the trophic base of most shallow lotic systems and assemblage composition and functional integrity are key indicators of water quality (Stancheva & Sheath 2016)
The concentration of total phosphorous of benthic organic matter was a more accurate indicator of the trophic state of the stream sites we studied relative to nutrient concentrations of water as demonstrated by correlation coefficients for nutrient concentrations to benthic concentrations of chlorophyll a, ash-free dry mass of benthic organic matter, and biotic indices which denote trophic state using diatom and soft-algae taxa
Photoautotrophic periphyton was in excellent physiological condition as indicated by the low concentrations of pheophytin a relative to concentrations of chl a and the corresponding Optical density (OD) ratios of OD664 to OD665 1.5 at all sites other than the photoautotrophic periphyton sampled at the Suggs Creek site (Table 1)
Summary
Algae are a major component of the trophic base of most shallow lotic systems and assemblage composition and functional integrity are key indicators of water quality (Stancheva & Sheath 2016). The compositions of soft-algae assemblages of the vast majority of streams in the Interior Plateau Level III Ecoregion (Griffith et al 1997; USGS 2016) are unknown. This lack of basic knowledge of a major component of the trophic base limits the ability of watershed managers to measure and monitor the impacts of poor quality water. This work documents the composition of algae assemblages essential to monitor the effects of water quality in eight stream reaches in seven different watersheds in the central region of the Interior Plateau Level III Ecoregion. Estimation of the biomass of photoautotrophic periphyton by measurements of the concentration of benthic chlorophyll (chl) a is one of the most common methods to assess the trophic state of streams (Biggs 2000). Dodds et al (1998) suggested classification of temperate streams with
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