A Model of Algal Exports in Some Iowa Streams

Abstract

The rivers of central Iowa carry high densities of suspended algae. Evidence is presented to support the hypothesis that these plants are derived from benthic populations on the streambed. In an analysis of several streams, a significant correlation was found between the amounts of algal chlorophylls being exported downstream and the areas of the wetted streambed upstream from the sampling points. In the warm months the algal exports amounted to 4.5 mg°m(—2)°day(—1) of chlorophyll a.

Spatial and temporal variations of Cocconeis placentula var. euglypta (Ehrenb.) 1854 Grunow, 1884 in drift and periphyton

“…Periphyton organisms that move from the substrate and are transported in the water column as algal drift are the most important components of plankton in streams (Swanson and Bachman, 1976;Allan, 1995). One of the hypotheses to explain algal drift is that daughter cells initiate a migration process during cellular reproduction (Stevenson and Peterson, 1991).…”

Chemical and physical influences on invertebrate drift in subarctic Alaskan streams

“…Recent studies (Cummins 1973, Vannote et al 1980) have shown the importance of allochthonous materials, particularly tree leaves, as food for some stream benthic invertebrates. It should, however, be noted that allochthonous inputs to the study streams are probably In this study, the benthic algal populations were assessed by measuring the amount of algae suspended in the water column assuming a and the size of the benthic algal standing crop (Swanson and Bachmann, 1976). Chlorophyll £ content, which is an indicator of biomass, and is relatively easy to measure, was utilized.…”

Algal communities of the Skunk River, Iowa, with special reference to the epipelon

“…Small tributaries of larger rivers then are probably the source of much of the suspended algae. Swanson and Bachmann (1976) noted that "There probably is an upper limit to the size of a stream system where this (model) would apply, with true plankton growth assuming a greater importance in larger The answer may lie in the fact that centric diatoms lying on sediments may be a much less stable association than true benthic species, i.e. those possessing the raphe.…”

“…These sediments either appeared as It is unlikely that individual cells become more bouyant as a result of Og accumulation from photosynthesis. However, it is a common observation (Blum, 195^» 1957;Swanson and Bachmann, 1976) that "wefts" of epipelic algae may rise to the surface of the water with the aid of bubbles of Op trapped in aggregates of sediment.…”

“…Little doubt remains, then, since Swanson and Bachmann (1976) showed that a high correlation exists between There may also be point sources contributing to the phytoplankton. The phytoplankton data from 17 October showed a large influx of centric diatom somewhere between stations 1 and 2 (Figures l6, 17).…”