Stream water numeric criteria developed for Illinois River Watershed (IRW) of 0.037 mg total P L-1, was based on the frequency distribution of flow-weighted P in undeveloped rivers. However, a recent independent review stated that the US EPA stressor-response approach is the most appropriate, scientifically based method for developing numeric nutrient criteria, as long as it used in conjunction with a ‘weight-of-evidence’ approach. Thus, it is essential that algal-response characteristics be determined as a function of in-stream P sources and processing to provide the needed ‘weight-of-evidence’ data for IRW streams. The objectives of this study were to examine the relationship fluvial P sources and algal biomass accumulation.
A mesocosm experiment was conducted which simulated the release of P during baseflow from sediment deposited in a stream. Periphyton biomass (as chlorophyll-a) was determined after 8 days after tiles inoculated in IRW stream were equilibrated with soils of varying P levels in 700 mL water. As expected, there was a positive linear relationship between the Mehlich-3 P content of stream sediment and stream P (R2=0.99) as well as biofilm chlorophyll-a (R2=0.75).
A mesocosm experiment was conducted which simulated the release of P during baseflow from sediment deposited in a stream. Periphyton biomass (as chlorophyll-a) was determined after 7 days after tiles inoculated in IRW stream were equilibrated with soils of varying P levels in 700 mL water. As expected, there was a positive linear relationship between the Mehlich-3 P content of stream sediment and stream P (R2=0.99) as well as biofilm chlorophyll-a (R2=0.75).