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 sodium aluminate to control sediment phosphorus (P) release. A comparison of results from two summers each before and after treatment indicates that the treatment did not universally impact the recruitment of either sporulating or non-sporulating forms of blue-green algae. Blooms of Anabaena, Aphanizomenon, and Coelosphaerium resulted predominantly from growth in the water column following strong recruitment episodes lasting up to two weeks, while Microcystis populations were relatively insensitive to periodically high inputs from recruitment. The development of planktonic populations of Gloeotrichia echinulata, by contrast, were 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 accumulation of aluminum floc to the lake sediments. Both G. echinulata and C. naegelianum showed elevated levels of cellular P in newly recruited 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 recruitment of G. echinulata. The recruitment of G. echinulata, and hence the magnitude of P translocation, was therefore more responsive to environmental conditions prevalent at the sediments than to direct effects of the treatment itself.