Eutrophication of the salt valley reservoirs, 1968–73 I. The effects of eutrophication on standing crop and composition of phytoplankton

Abstract

IntroductionA study was carried out over a period of six years to determine the effects of eutrophication upon standing crop and composition of the phytoplankton in four recently constructed flood control reservoirs in Nebraska. Water samples collected weekly during June, July, and August from 1968-73 were analyzed for chlorophyll a, phytoplankton composition, and phytoplankton abundance. Total volume of phytoplankton was calculated from appropriate dimensions and formulae. Inorganic turbidity in one reservoir was an important factor regulating the size and composition of the phytoplankton standing crop. In that reservoir diatoms were the most important component of the phytoplankton community during those years in which inorganic turbidity was greatest. When inorganic turbidity declined, bluegreen algae became dominant.In the clear-water reservoirs chlorophyll a, phytoplankton number, and phytoplankton volume were significantly correlated with reservoir age, with the oldest containing chlorophyll a concentrations up to 247 mg/m 3 and mean phytoplankton volumes up to 329 mm 3 /l, values sufficient to place it in the hypereutrophic category. The reservoirs had 2-6 times more chlorophyll a present at the end of the study than at the beginning, with the increase being greatest in the newest reservoir. Phytoplankton volume was significantly correlated with chlorophyll a in all the reservoirs.Blue-green algae quickly became established as community dominants in the reservoirs, making up over 8o percent of the phytoplankton volume in the newest reservoir by the second year of its existence. In the other clear-water reservoirs, blue-greens usually constituted over 95 percent of the total phytoplankton volume in summer. Three genera, Microcvstis, Aphanizomenon, and Anabaena, were responsible for virtually the entire standing crop of blue-greens in all the reservoirs.

Effects of algicide (Copper Sulfate) application on short-term fluctuations of phytoplankton in Lake Paranoá, Central Brazil

“…The decomposition process causes a decreasing oxygen concentration, particularly in bottom layers, as observed by Padovesi-Fonseca et al (2002) during this sampling period. According to Hergenrader (1980), decreasing OD can cause intense fish kills.…”

Eutrophication of the salt valley reservoirs, 1968–1973 II. Changes in physical and chemical parameters of eutrophication

“…In a previous paper (Hergenrader, 1980), I discussed the effects of eutrophication on phytoplankton standing crop and composition in the Salt Valley Reservoirs, a series of recently constructed flood control reservoirs near Lincoln, in southeastern Nebraska . Four of the reservoirs, Branched Oak, Pawnee, Stagecoach and Wagon Train, ranging in age from one to six years at the beginning of the study, were sampled over a six-year period from 1968-73 .…”

Food Habits of Stunted and Non-Stunted White Perch (Morone americana)

“…Branched Oak Lake, located in Lancaster County, is a 728-ha, hypereutrophic reservoir. This reservoir does not permanently stratify (Hergenrader 1980b). The fish community consists of walleye, hybrid striped bass (M. saurtilis x M. chrysops), largemouth bass (Micropterus salmoides), bluegill (Lepomis rnacrochirus), white crappie (Pomoxis annularis), black crappie (Pornoxis nigromaculatus), common carp (Cyprinus carpio), blue catfish (Ictalurus furcarus), channel catfish (I. punctahrs), flathead catfish (Pylodictis olivaris), gizzard shad (Dorosoma cepedianurn), brook silverside (Labidesthes sicculus), and white perch.…”

“…Like Branched Oak Lake, it does not thermally stratify (Hergenrader 1980b). The fish community at Pawnee Lake consists of walleye, sauger (Sander canadensis), white bass, largemouth bass, black crappie, white crappie, channel catfish, flathead catfish, freshwater drum (Aplodinotus grunniens), common carp, and white perch.…”