Ecology of Sphaerotilus in an experimental outdoor channel

This paper describes ecological investigations performed in an outdoor experimental channel receiving Huron River water and beet sugar or crude molasses during two summers of operation (1965 and 1966).The channel was assembled in two lengths, 645 ft (1965) and 704 ft (1966), with sampling stations located one near the beginning, one in the middle and one near the end. At each station, three strands of knitting yarn were suspended and allowed to remain for 24 hr. After this time, the strands were removed, together with attached growth, and fresh strings replaced. The replicate strings were cut into 10 cm sections, with one-half of these sections used for dry weight determinations.The attached organisms were removed by violently shaking the strings suspended in a measured quantity of water. One drop was then removed and direct microscopic counts and identification made immediately. Dry weights were obtained by drying the strings in aluminum weighing pans overnight at 90[deg]C.A total of 12 experiments was run, the duration of each being in most cases five days.In the first series of experiments flow through the channel was at 100 g/min. at an essentially uniform velocity of 1 ft/sec. Nutrient concentration was varied from 1 mg/l as sucrose.In the last series of experiments, nutrient concentration was held at 5 mg/l and velocity varied at the three stations by altering the height of an overflow weir between 0.0 and 0.6 ft, and changing the flow between 25 and 200 g/min. This provided a range of velocities at the station from 0.09 to 1.49 ft/sec.The results of attached organism determinations are presented following each experiment and their response to nutrient concentration and velocity summarized in the Discussion.Sphaerotilus-dominated biological flocs were stimulated to bloom proportions within 30 hr after the addition of as little as 1 mg/l of sucrose. Maximum growth was obtained at a concentration of 5 mg/l at velocities from 0.58 to 1.49 ft/sec in the temperature range of 20-28[deg] C after around 72 hr of feeding. About this time, detaching and floating material was equivalent to new material being formed, and the term "saturation population" was proposed to describe this condition.The biological floc community was composed chiefly of Sphaerotilus natans, Melosira varians, M. granulata, Nitzschia sp., Navicula sp., Cosmarium sp., Euglena sp., and the protozoans, Bodo sp., Tetrahymena pyriformis, Colipidium colpoda, and Amoeba sp., tendipedid and simuliid larval forms also apparently found a mutualistic association within the flocs.Saturation population and classical Sphaerotilus flocs could not be obtained at temperatures below 17[deg] C. The typical form was replaced in dominance at low temperatures by an unidentified filamentous bacillus, the total mass of which never approached that of the classical growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33316/1/0000711.pd