Microbial colonization of seston and free bacteria in an impounded river

Epifluorescent microscopy was used to compare microbial colonization of seston particles and the abundance of free microbes in the Dan river, Virginia, from March to November 1982, to determine the effects of impoundment on seston quality. Total counts of living bacteria (free plus attached) did not differ significantly between stations. Densities of attached bacteria at sites upstream and downstream of the impoundment were not significantly different, but were generally higher within the reservoir. At all stations, colonization density on particles less than 25 um was consistently greater than that on larger particles. Density of attached bacteria and individual particle surface area were correlated. Free bacteria were significantly more concentrated in the reservoir and 5 km below the dam than at stations upstream of the impoundment. Thirty-three references are appended.