Dodds, W. k. Kansas State University,
Tank, J. k. University of Illinois,
Lohman, K. University of Idaho,
Smith, V. University of Kansas,

Nutrient releasing substrata were used to assess N and P limitation of microphytobenthos biomass in nine streams across North America. The most common response was co-limitation by N and P. Co-limitation was more common than in previously published bioassays, with nine streams limited by N+P, ten by N, and twelve by P. Literature review of periphyton chlorophyll and water column nutrients from approximately 200 sites in North America and New Zealand revealed total N explained 37% and total P an additional 6% of chlorophyll variance; both N and P explained more variance than either alone. The EPA National Eutrophication Survey (927 streams) revealed a mean molar total water column N:P of 80, suggesting a prevalence of P limitation (unlike bioassay and correlation approaches). The Survey probably concentrated on more turbid and agriculturally-influenced streams than our biomass and correlation approaches. Thus, more extensive datasets are necessary for a general picture of periphyton nutrient limitation. Still, limitation by N, or N and P should not be discounted in any individual stream. Our results also may apply to ecosystem function of streams dominated by heterotrophs since fungal bioassays from the nine periphyton bioassay sites yielded similar results.
Day: Friday, Feb. 5
Time: 09:00 - 09:15am
Location: Eldorado Hotel
Code: SS46FR0900E