Response of Periphytic Algae to Gradients in Nitrogen and Phosphorus in Streamside Mesocosms |
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Authors: | Steven T Rier R Jan Stevenson |
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Institution: | (1) Department of Zoology, Michigan State University, Michigan, 48824, USA;(2) Department of Biological & Allied Health Sciences, Bloomsburg University, Hartline Science Center, 400 East 2nd Street, Bloomsburg, PA 17815, USA |
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Abstract: | In this study we manipulated both nitrogen and phosphorus concentrations in stream mesocosms to develop quantitative relationships
between periphytic algal growth rates and peak biomass with inorganic N and P concentrations. Stream water from Harts Run,
a 2nd order stream in a pristine catchment, was constantly added to 36 stream-side stream mesocosms in low volumes and then
recirculated to reduce nutrient concentrations. Clay tiles were colonized with periphyton in the mesocosms. Nutrients were
added to create P and N concentrations ranging from less than Harts Run concentrations to 128 μg SRP l−1 and 1024 μg NO3-N l−1. Algae and water were sampled every 3 days during colonization until periphyton communities reached peak biomass and then
sloughed. Nutrient depletion was substantial in the mesocosms. Algae accumulated in all streams, even streams in which no
nutrients were added. Nutrient limitation of algal growth and peak biomass accrual was observed in both low P and low N conditions.
The Monod model best explained relationships between P and N concentrations and algal growth and peak biomass. Algal growth
was 90% of maximum rates or higher in nutrient concentrations 16 μg SRP l−1 and 86 μg DIN l−1. These saturating concentrations for growth rates were 3–5 times lower than concentrations needed to produce maximum biomass.
Modified Monod models using both DIN and SRP were developed to explain algal growth rates and peak biomass, which respectively
explained 44 and 70% of the variance in algal response. |
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Keywords: | periphyton diatoms nutrient limitation Monod model growth rates peak biomass |
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