A management alternative for Lake Apopka

Abstract

We examine the idea that whenever high levels of planktonic algae impair a lake, nutrient control is the first step to be taken regardless of what other management actions might be contemplated. Our example is Lake Apopka, a 12,500 ha, shallow (1.7 m), polymictic lake in central Florida. Prior to 1947, the lake was dominated by macrophytes, was reputed to have clear waters, and had a national reputation for its largemouth bass fishery. Following a hurricane in 1947, the lake switched to a turbid, algal state and the bass fishery is all but gone. For over 30 years, it was either implied or stated directly that nutrient enrichment from anthropogenic activities, especially farms along the north shore, was to blame for this change and the lack of macrophyte recovery. The current management plan is to remove the farm nutrient supply by purchasing the farms under the theory that this will lower the total phosphorus concentration in the water and thus restore the lake. We have developed the most probable phosphorus budgets for the lake based on the studies of others and have determined that a fluid mud layer that is frequently resuspended by the wind will lead to high internal loading and slow the drop in phosphorus concentration. The equilibrium phosphorus concentration will lie between 52 and 88 mg·m−3, so the lake will remain in its eutrophic state. We propose an alternative management plan using artificial reefs that will focus on restoring the largemouth bass fishery in the immediate future. This idea is attractive because bass fishing was the dominant use of this lake in the past, it can be accomplished without waiting for a change in trophic state, and it can produce results in a relatively short period of time.