Phytoplankton Periodicity in an Urban Lake: Summit Lake, Akron, Ohio (USA)

ABSTRACT

Summit Lake, a small (37.4 ha), shallow (Zm = 13 m), hypertrophic, and normally dimictic lake, received inflowing heated water in mid-June 1977 partly disrupting thermal stratification. The water column was well-mixed to depths 4–5 X the depth of the photic zone (2–2.5 m). Phytoplankton cell volumes ranged from 1 mm³/L in late winter to 100 mm³/L in spring, averaging 12 mm³/L following destratification. A prominent autumnal phytoplankton maximum failed to develop. One hundred thirty-two (132) species of phytoplankton were identified. A prominent spring peak of cyanobacteria, green algae, and diatoms was followed by predominantly non-heterocystous cyanobacteria, Oscillatoria prolifica, Microcystis aeruginosa, and Gomphosphaeria lacustris. The dominance of cyanobacteria can be attributed to their ability to maintain buoyancy and to conditions favoring their growth—e.g. a turbid photic zone with high levels of phosphorus and ammonia probably derived from sanitary sewage inflows.