A quantitative study of the summer phytoplankton in four Central North Carolina ponds

Summary The phytoplankton of four ponds in the lower Piedmont and upper Coastal Plain of North Carolina was studied to find a possible correlation between bound phosphorus plankton numbers. No correlation was apparent therefore this paper reports a detailed study in relation to other habitat factors.The ponds are all shallow (2 m.). The Piedmont ponds are high in colloidal clay while the Coastal Plain ponds are much lower. The pH ranged around 7.0 except for one Coastal Plain pond which remained close to pH 6.4. Water temperature ranged from 30° C in June to 23° C near the end of August.Phytoplankton numbers were determined by the standard Sedgwick-Rafter method. Populations were low except for brief pulses. One Coastal Plain pond was typical of a fertilized pond and had several tremendous blooms of blue-green algae. The others supported a seemingly typical Caledonian flora, rich in species but low in number of individual organisms.There was no clear correlation between phytoplankton populations and any habitat factor except pH. This correlation is probably not direct but only an indication of water quality.This work was aided by Contract No. AT-(40-1) 2100 with the Division of Biology and Medicine, U. S. Atomic Energy Commission.