SEDIMENT-TO-WATER BLUE-GREEN-ALGAL RECRUITMENT IN RESPONSE TO ALUM AND ENVIRONMENTAL-FACTORS

The sediment-to-water recruitment of blue-green algae was investigated in a shallow lake following treatment with aluminum sulfate and sodiu m aluminate to control sediment phosphorus (P) release. A comparison o f results from two summers each before and after treatment indicates t hat the treatment did not universally impact the recruitment of either sporulating or non-sporulating forms of blue-green algae. Blooms of A nabaena, Aphanizomenon, and Coelosphaerium resulted predominantly from growth in the water column following strong recruitment episodes last ing up to two weeks, while Microcystis populations were relatively ins ensitive to periodically high inputs from recruitment. The development of planktonic populations of Gloeotrichia echinulata, by contrast, we re largely dependent on sustained recruitment in response to adequate light and temperature regimes at the sediment surface. The cellular P content of recruited G. echinulata colonies was unaffected by the accu mulation of aluminum flee to the lake sediments. Both C. echinulata an d C. naegelianum showed elevated levels of cellular P in newly recruit ed colonies as compared to planktonic colonies, indicating P transport from the sediments to the water column. Total P translocation by blue -green algae was negligible in the absence of a substantial recruitmen t of G. echinulata. The recruitment of G. echinulata, and hence the ma gnitude of P translocation, was therefore more responsive to environme ntal conditions prevalent at the sediments than to direct effects of t he treatment itself.