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Microseston Dynamics in a Simple Sierra Nevada Lake‐Stream System

Maciolek, J. A., Tunzi, M. G.
Ecology 1968 v.49 no.1 pp. 60-75
algae, aquatic invertebrates, digestion, drainage, ecology, effluents, lakes, larvae, mountains, phytoplankton, seepage, streams, turbulent flow, vegetation
Suspended organic particles in a small, precipitous drainage were studied primarily in regard to trophic ecology. Headwater and seepage sources in the 6.5—km (4—mile) system contained minimal quantities (<2 gcal/liter or 0.5 mg/liter dry wt) mainly of organic detritus. Maximum concentration (>12 gcal/liter or nearly 3 mg/liter dry wt) appeared in the stream as effluent phytoplankton from the single lake located near the headwaters. A progressive decrease in cellular microseston below the lake was accompanied by an increase in detritus. The cell loss was due mostly to trophic uptake by filter—feeding simuliid larvae which were capable of removing 60% of the suspended algae within a 0.4—km section of stream. Downstream gain of organic detritus resulted from external contributions (e.g. streamside vegetation), abetted by decompositional processes within the stream, including digestion by aquatic invertebrates. Autochthonous material was considerably less important quantitatively as seston than allochthonous (lacustrine and terrestrial). Sedimentation and physiochemical loss were secondary to trophic uptake in seston removal. Destruction of cellular material by turbulent flow was directly proportional to stream gradient and was clearly evident only where a prolonged gradient existed in excess of 5%. Because all loss—causing factors operate selectively on cellular material, organic detritus would be expected as the chief microseston component of streams isolated from lake outflow.