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  • Grazing  (1)
  • fathead minnow larvae  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 72 (1987), S. 1-7 
    ISSN: 1432-1939
    Keywords: Aufwuchs algae ; Campostoma ; Fertilizer ; Nutrients ; Grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have shown that an algivorous grazing minnow (Campostoma anomalum) is the major herbivore in Brier Creek, a hardwater stream in south central Oklahoma. In summer and autumn schools of Campostoma virtually eliminate algae from substrate surfaces in deeper areas of some pools. The pool-to-pool distributions of algae and Campostoma reported for this stream could occur if nutrient limitation permits grazing by Campostoma to “outrun” algal growth. To test this hypothesis, mesh pens were built to exclude Campostoma from substrates in each of four typical Campostoma pools. N+P+K lawn fertilizer was added daily to two of the four pools; the other two, which received no fertilizer additions and which were not visibly affected by fertilizer transported downstream from the pools enriched with nutrients, served as controls. Algae accumulated rapidly on natural substrates and on unglazed ceramic tiles in grazer-exclusion pens in pools receiving N+P+K additions and more slowly in pens in both control pools. Periphyton biomass on grazed substrates in all four pools remained low throughout the experiment. Hence, Campostoma at normal densities were able to outrun algal growth even when nutrients were added. Eleven days after the experiment started, I determined biomass, biomass-specific net primary productivity, and areal net primary productivity of periphyton on substrates exposed to all combinations of grazer (+,0) and nutrient (+,0) treatments. Grazing increased biomass-specific primary productivity, prevented accumulation of biomass, and decreased areal primary productivity of periphyton. Additions of N+P+K increased biomass-specific net primary productivity of grazed and ungrazed periphyton and markedly increased biomass of periphyton on substrates protected from Campostoma. Although food supply for Campostoma appeared to be greater with nutrient additions, condition of Campostoma in pools receiving N+P+K was not significantly different from Campostoma collected from control pools 35 days after the experiment started. I conclude that although nutrient supply limits biomass-specific primary productivity of periphyton in Brier Creek, nutrient limitation in this stream exacerbates, rather than causes, the visually conspicuous pool-to-pool complimentary distribution of algae and Campostoma: in this stream, grazing by Campostoma at natural densities can outrun periphyton growth even when nutrients are added.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Ecotoxicology 5 (1996), S. 377-393 
    ISSN: 1573-3017
    Keywords: ambient toxicity testing ; Ceriodaphnia ; fathead minnow larvae ; biological monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The purpose of this paper is to show how short-term laboratory tests, conducted according to US Environmental Protection Agency (EPA) procedures, can be used effectively to assess water-quality conditions in streams or rivers that receive pollutants from industry or municipal or agricultural areas. Standardized, short-term tests with fish, aquatic invertebrates or algae are commonly used to estimate the acute or chronic toxicity of wastewaters; this is referred to as effuent testing. The methods used for testing effluents also can be used to assess water quality in receiving streams: in this application, the procedures are referred to as ambient testing. Despite similarity in methods, the major objective of effluent testing differs importantly from that of ambient testing. In effluent testing, the key objective is to determine how toxic an effluent is; in ambient testing, the main objective usually is that of determining if the water at a site is toxic. This difference is subtle but very important: it shapes the strategy for cost-effective ambient testing, and determines the framework for effective statistical analysis and interpretation of ambient toxicity test results. Specific case-study examples are provided demonstrating the kinds of information that can be extracted from ambient toxicity testing by use of different statistical methods, including analysis of variance, contingency-table analysis, and two types of multivariate procedures (principal components analysis and logistic regression). Examples also are given supporting the idea that an effective ambient testing programme should be long-term, and contain a diagnostic-testing component analogous to the toxicity identification procedures used to supplement effluent-testing programmes. Recommendations derived as ‘lessons learned’ from largescale ambient toxicity testing programmes for receiving streams at Department of Energy facilities include: (1) testing more frequently with one species (preferably Ceriodaphnia) generally is more effective, in terms of information gained per dollar spent, than testing less frequently with two or more species; (2) use five or more sites per test period, plus two or more reference sites, whenever possible; (3) use four to six test periods per year; and (4) use diagnostic testing to supplement the ambient-testing programme. Various laboratory and in situ methods for environmental assessment are now under development, but these methods probably will not gain acceptance for use in regulatory situations for many years. Rapid growth in need for ecological risk assessments outstrips the rate at which new test procedures are approved for regulatory purposes. Thus, laboratory tests for estimating possible environmental impacts of toxic or disruptive pollutants are likely to be used more frequently during the next decade.
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