Seven small tributary streams with drainage areas ranging from 12.6 to 71.9 square miles, representative of both limestone and freestone settings, in the Lower Susquehanna River Basin were sampled for algae, nutrients, water quality, habitat, land use, hydrology, fish, and invertebrates. Nutrients, site characteristics, and selected characteristics of the invertebrate and fish communities known to influence algal growth were compared to chlorophyll a concentrations. Nitrogen was not found limiting in these streams; however, phosphorus may have been limiting in five of the seven streams. Concentrations of chlorophyll a in riffles increased with the degree of open canopy and as bottom substrate reached the gravel/cobble size fraction. These increased chlorophyll a concentrations and the substrate size in turn raised the levels of dissolved oxygen in the streams. Freestone streams had increased chlorophyll a concentrations associated with increases in percentage of omnivorous fish and in pH and decreases in percentage of collector/gatherer invertebrates. Concentrations of chlorophyll a in limestone riffles decreased as the percentage of omnivorous fish increased. Depositional chlorophyll a concentrations increased as the Bank Stability Index decreased and as the riffle velocity increased. Depositional chlorophyll a concentrations increased in limestone streams as collector/gatherer invertebrates increased and as phosphorus concentrations decreased. No relations were seen between chlorophyll a concentrations and land-use characteristics of the basin.
In this study, there were too few sampling sites to establish statistically based relations between algal biomass and nutrient concentrations. Further study is needed to generate data suitable for statistical interpretation.
