Shifts In Nutrient Limitations To Stream Biofilms Along An Urban Watershed Gradient
Class
Article
Department
Biology
Faculty Mentor
Michelle Baker
Presentation Type
Poster Presentation
Abstract
In Utah and other western states, stream biofilms are commonly limited by nitrogen or co-limited by both nitrogen and phosphorus. Our study explored how the relative balance of autotrophic and heterotrophic constituents in stream biofilms influences nutrient limitation at sixteen sites in three urban watersheds in Utah. We measured nutrient limitation with nutrient diffusing substrates containing nitrogen (NH4-N), phosphorus (PO4-P), both nitrogen and phosphorus, or no nutrients. Biofilm responses to nutrient additions were measured as chlorophyll a (autotrophs) and ash-free dry mass (autotrophs + heterotrophs). Nutrient additions affected chlorophyll levels at ten sites. Most commonly, autotrophs were co-limited by N and P (three sites) or primarily limited by N and secondarily limited by P (three sites). Nutrient additions suppressed chlorophyll levels at four sites. Nutrient additions affected ash-free dry mass at only three sites, suppressing biomass at two sites, and increasing biomass at one site. At a given site, chlorophyll a and ash-free dry mass never had the same response to nutrient additions. These preliminary results indicate autotrophs and heterotrophs respond differently to nutrient additions. Further analyses will consider how the relative balance autotrophs and heterotrophs, stream nutrient concentrations, and light availability affect nutrient limitation patterns along an urbanization gradient.
Start Date
4-9-2015 3:00 PM
Shifts In Nutrient Limitations To Stream Biofilms Along An Urban Watershed Gradient
In Utah and other western states, stream biofilms are commonly limited by nitrogen or co-limited by both nitrogen and phosphorus. Our study explored how the relative balance of autotrophic and heterotrophic constituents in stream biofilms influences nutrient limitation at sixteen sites in three urban watersheds in Utah. We measured nutrient limitation with nutrient diffusing substrates containing nitrogen (NH4-N), phosphorus (PO4-P), both nitrogen and phosphorus, or no nutrients. Biofilm responses to nutrient additions were measured as chlorophyll a (autotrophs) and ash-free dry mass (autotrophs + heterotrophs). Nutrient additions affected chlorophyll levels at ten sites. Most commonly, autotrophs were co-limited by N and P (three sites) or primarily limited by N and secondarily limited by P (three sites). Nutrient additions suppressed chlorophyll levels at four sites. Nutrient additions affected ash-free dry mass at only three sites, suppressing biomass at two sites, and increasing biomass at one site. At a given site, chlorophyll a and ash-free dry mass never had the same response to nutrient additions. These preliminary results indicate autotrophs and heterotrophs respond differently to nutrient additions. Further analyses will consider how the relative balance autotrophs and heterotrophs, stream nutrient concentrations, and light availability affect nutrient limitation patterns along an urbanization gradient.