Aquatic vegetation commonly seen within the lake itself include widgeon grass ("Ruppia maritima"), filamentous green algae ("Enteromorpha" and "Cladophora" sp.), sea lettuce ("Ulva" sp.), dead man's fingers ("Codium fragile") and occasionally wireweed ("Sargassum muticum"). Growth of these aquatic plants reaches a peak in mid-June, and the subsequent die-off and decomposition can result in bad odors, unsightly appearance, and depletion of oxygen in the water column. To prevent this nuisance condition, the City uses a floating mechanical harvester to remove excess growth during the summer months. The most common aquatic plants in Lake Merritt are tiny, free-floating phytoplankton. Visitors often do not appreciate the sometimes-murky water in the lake, but the cloudiness represents a water column rich in microscopic life, providing a basis for a diverse and thriving web of animal life at the lake, both marine and avian.