Algal bioassay of the portage lakes, summit County, Ohio

Abstract

The Portage Lakes are a series of natural lakes and man-made reservoirs in the upper Tuscarawas River of northeastern Ohio. Algal assays with Selenastrum capriconutum Printz suggested that the temporal pattern of water fertility differed between the more lentic water bodies and those with more lotic characteristics, probably reflecting differences in nutrient availability. Algal growth rates in the lentic water bodies ranged from approximately 0·6 doublings a day in early summer to <0·2 doublings a day in late summer. In contrast, algal growth rates in the lotic water bodies increased from 0·2–0·3 doublings a day in June to 0·3–0·5 doublings a day in July, and then declined in August to <0·3 doublings a day. Nutrient enrichments with PO 4-P and NO 3-N indicated that P was usually the major limiting nutrient in both groups of lakes. NO 3-N additions sometimes stimulated algal growth in the lotic water bodies.