Annual abundances, diversity and growth potential of gymnamoebae in a shallow freshwater pond

Abundance and diversity of gymnamoebae were assessed at monthly intervals for one year in the sediment surface layer of a shallow, highly productive, freshwater pond located in northeastern United States using laboratory culture enumeration techniques. The range in total abundance was 81/ml in January to 1,568/ml in June (spring peak) and 1,813/ml in October (autumn peak). The latter is equivalent to over 1.8 million per liter, one of the highest values reported for gymnamoebae from a freshwater pond. Maximum diversity (H = 3.3) occurred in April, July, and August. The growth potential of the gymnamoebae was determined in laboratory cultures (20 degrees C) containing only the pond water (control culture) and pond water emended with malt-yeast extract and glucose (nutrient culture) using pond water collected in December. The total abundance of gymnamoebae increased from 363/ml in the initial pond water sample to approximately 1,800/ml in each of the culture conditions in the first week. Thereafter, abundances reached 5,678/ml (control culture) and 8,016/ml (nutrient culture) by the third week indicating the vigorous growth potential from winter standing stock.