Many lakes on Sanibel are at the point where they have continuous blooms of harmful algae. SCCF Marine Laboratory is currently conducting jar tests on water samples from several lakes experiencing harmful algae blooms. These tests involve taking small samples from the lakes and adding different treatment chemicals to multiple samples to determine if nutrients are reduced and the harmful algae blooms dissipate without adding additional harmful residuals to the water.

This isn’t unique to Sanibel. As South Florida’s lakes become more and more enriched with nutrients such as nitrogen and phosphorus, people are becoming concerned about the algae blooms happening in their backyard lakes. Many of Florida’s urban waterbodies have become polluted with nutrients due to the consequences of development. Septic systems, fertilized turf, decreased tree canopy, and more impervious surfaces are characteristics of conversion of natural landscapes which increase the amount of nutrients in our waterbodies and result in algae blooms.

Best management practices are encouraged by local governments and, in many cases, communities do implement these practices and have been reducing nutrient inputs through their efforts. However, the waterbodies are often so high in nutrients that reductions in nutrients won’t have a significant effect without some type of in-lake intervention.

Chemical treatment of hypereutrophic (very badly polluted) lakes is becoming more common. Chemicals such as alum (aluminum sulfate), ferric sulfate (iron), bentonite clay, hydrogen peroxide, and calcium carbonate can be used to kill algae, tie up nutrients, and settle out solids to clarify lake water. Some of these chemicals can have adverse effects to lake ecology if applied in large amounts.

That is why the SCCF Marine Lab is conducting these jar tests. Different chemicals at different doses are applied to each sample. The samples are then tested to see if nitrogen and/or phosphorus are reduced and if any residual aluminum or iron are left in solution. If nutrient levels can be reduced significantly without adding additional harmful residuals to the water, these treatments may be attempted on a larger scale to treat algae.

Caption: Jar testing water from two lakes using four different treatments. Results will be available by the first of March.