Relationships between planktonic, epiphytic, and epipelic diatom populations in selected ponds of Brazos County, Texas

Three ponds located in Brazos County, Texas, were sampled regularly for a period of one year, from August 1964 through August 1965, in order to study diatom populations on a seasonal basis. Samples were collected from each habitat of the ponds so that comparisons could be made among species which occurred as planktonic, epiphytic, or epipelic forms. Thirty-six species of diatoms were observed in the three ponds studied. Only seven of the species occurred frequently enough and in sufficient abundance to be considered major constituents. The majority of the species being entirely epipelic or planktonic. Most species occurred in all three of the pond habitats. The planktonic diatoms exhibited the greatest degree of fluctuation in abundance. There was a general increase in the winter, with maximum numbers attained during the months of February. The planktonic diatoms were lowest in abundance during the summer. The epiphytic and epipelic diatoms showed a low to moderate amount of fluctuation in abundance, with most of the major species showing some increase during April, May, and June. The planktonic diatoms were the least stable, both in the number of species present and in the number of individuals and showed the largest fluctuation form month to month while the epiphytic species were the most stable. As a general pattern, a species did not increase in abundance in more than one habitat at a time, even though the species was present in more than one habitat. The three ponds were similar physically and in the structure of their diatom associations. However, the timing and magnitude of the variations in numbers varied greatly from pond to pond. Where the same species was found in all three ponds, it reacted a different way in each pond