2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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6/07/2017 | 10:00 AM - 10:15 AM | A LITTLE BIT OF ALGAE GOES A LONG WAY: NUTRIENT ENRICHMENT STIMULATES ALGAL GROWTH IN HEAVILY SHADED STREAMS | 302B

A LITTLE BIT OF ALGAE GOES A LONG WAY: NUTRIENT ENRICHMENT STIMULATES ALGAL GROWTH IN HEAVILY SHADED STREAMS

Algae are often limited by nitrogen (N) and/or phosphorus (P) but the strength of nutrient limitation is thought to vary with light availability. Here, we tested responses of algae to experimental N and P enrichment in five heavily shaded (light-limited) streams that were enriched along dual gradients of high to low P and low to high N concentrations. Mean annual biofilm chlorophyll-a increased during enrichment (6x-17x, e.g., from 1 mg/m2 to 20 mg/m2), whereas mean annual biofilm biomass only increased up to 1.8x. During high-light periods in spring, chlorophyll-a increased up to 33x and biomass up to 3.3x compared to pre-enriched conditions. Biomass and chlorophyll-a responded more to N than to P enrichment. Although responses of algae were temporally limited, high-magnitude, short-term biofilm production was positively correlated with biomass of diatom-consuming macroinvertebrates (R2 = 0.20), likely via increased proportions of diatoms consumed. Moreover, we found an increased importance of diatom-consumers in salamander diets. Our study suggests that nutrient enrichment can lead to seasonal pulses of biofilm production, with measurable effects at higher trophic levels, even in naturally light-limited, detritus-based ecosystems.

C24 Eutrophication
C01 Algae
C32 Primary and Secondary Production

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Presenters/Authors

Phillip Bumpers (), Odum School of Ecology, University of Georgia, bumpersp@gmail.com;