Nutrient-sestonic chlorophyl relationships in northern Ozark streams

We investigated relationships between sestonic chlorophyll (Chl), total phosphorus (TP), and total nitrogen (TN) at 23 sites an 13 streams in the Missouri Ozarks. There was a strong curvilinear relationship between mean sestonic Chi and both mean TP (R-2 = 0.78) and mean TN (R-2 = 0.70). Both models were improved when catchment area was included with either TP (R-2 = 0.90) or TN (R-2 = 0.84). Limited to 17 sites without point source nutrient additions, the relationship between sestonic Chi and both TP and TN was linear Including catchment area strengthened linear models with either TP (R-2 = 0.94) or TN (R-2 = 0.84). Land use (percent row crop or percent forest), together with catchment size, was also a good predictor of sestonic Chl in Ozark streams without point sources. When catchment area and TP or TN were used to predict sestonic Chi on specific dates following catastrophic flooding, models were less accurate than those based on long-term averages, but still explained 55-74% of the variance in sestonic Chi. Our results demonstrate that sestonic Chi is closely associated with nutrients and catchment area in Ozark streams and that nutrient - sestonic Chl models may have broad application in running waters.