TROPHIC STATUS RELATED TO PERIPHYTON AND MACROPHYTE DISTRIBUTION AND ABUNDANCE ALONG THE NORTH BOSQUE RIVER IN NORTH CENTRAL TEXAS

摘要

A two-year survey was conducted to estimate periphytic algae and macrophyte diversity and abundance at 11 locations within the North Bosque River watershed. Ash free dry weight by species was used to measure biomass. A total of 30 different species were collected; 24 macrophytes, five periphyton, and one moss. Macrophytes comprised the largest portion of total biomass at most sites, while algae were most frequently collected. The most biomass was contributed by the macrophyte Justicia americana (L.) Vahl, while Cladophora sp. was the dominant algae. The majority of algae were found in riffles, while macrophyte biomass was fairly evenly distributed between pool and riffle habitats. Nutrient concentrations generally showed saturated conditions for periphyton growth indicating that factors other than nutrients, such as light, may be limiting periphyton and possibly macrophyte biomass along the river. In comparison to proposed trophic state indices for periphyton, mesotrophic or eutrophic conditions were indicated at four of 11 sites. In contrast, measurements of instream chlorophyll-α concentrations of phytoplankton indicated mesotrophic conditions at eight of 11 sites. These differences in tropic status based on periphyton and phytoplankton indicate a need to monitor attached, as well as free-floating algae, when evaluating for water quality impairment in small to intermittent sized creeks and rivers.