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Spatial and Temporal Variability of Nutrient Limitation in 6 North Shore Tributaries to Lake Superior
Andrew P. Wold and Anne E. Hershey
Journal of the North American Benthological Society
Vol. 18, No. 1 (Mar., 1999), pp. 2-14
Stable URL: http://www.jstor.org/stable/1468005
Page Count: 13
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Nutrient availability varies both spatially and temporally in temperate systems because of timing of seasonal and hydrological events (e.g., spring snowmelt). Most studies have found either N or P to be primarily limiting. A nutrient-diffusing bioassay was used to determine if N, P, neither nutrient, or both nutrients were limiting to periphyton growth (measured by chlorophyll a) in 6 tributaries to Lake Superior during the ice-free season of 1994. Molar ratios of dissolved inorganic nitrogen to soluble reactive phosphorus (DIN:SRP) were also calculated to predict potential limitation conditions and determine agreement with bioassay results. Co-limitation predominated (N + P > all other treatments). No limitation was also common during the late portion of the ice-free season. DIN: SRP ratios were not useful in predicting nutrient-limitation conditions. Results showed that nutrient limitation of periphyton biomass varied over space and time on a relatively small regional scale. This result is significant because many studies extrapolate results from a single stream or time period to a much larger spatial or temporal scale.
Journal of the North American Benthological Society © 1999 The University of Chicago Press