DIURNAL CHANGES IN SHALLOW AQUATIC HABITATS

Diurnal changes were studied at different times of the year in a variety of Louisiana ponds, swamps, ditches and streams by the following procedure. Collections were made between 0500 and 0600 and between 1500 and 1600 on one day, and at the same times several days later. Each sample was analyzed chemically and biologically. The times chosen measure the approximate high and low values of dissolved substances in the daily chemical cycle. The extent of change in chemical factors and plankton indicated the degree and role of oxidative processes in a shallow habitat, and provided a measure for comparing different habitats.

Plankton populations, predominantly protozoa, often changed during the day, and sometimes changed significantly within 2 hr after sunrise. The conditions and organisms found in shallow habitats may thus depend upon the time of sampling.