Lagoon Turnover and Fish Kills

Some lagoons located throughout the community have experienced weather-related stress over the past several weeks. This stress caused by the depletion of oxygen in shallow water bodiesoccasionally results in fish kills within the lagoon. There are several reasons for the low levels of dissolved oxygen. When we receive higher than normal tides, saltwater lagoons located around the island’s perimeter can be inundated by large quantities of saltwater flowing back into the system. This dramatic change in water temperature and chemistry caused some saltwater lagoons to turn a milky brown color and resulted in some fish dying. This natural phenomenon is commonly referred to as “Turnover”, which refers to the mixing of two water column layers. This occurrence happens when cool water layers over the top of the lagoon. Once a substantial amount of water collects on the lagoon surface, it will fall through the upper water column, resulting in a violent mixing of the two layers. Oxygen levels in the lagoon waters will decline significantly, causing the weaker fish to die. After the initial mixing occurs, the water columns will naturally start rebuilding oxygen levels as the lagoon stabilizes.

We recently were notified about a fish kill in the lagoon off Little Comfort Road (between Prescott and Windwalk lanes) early this week. We responded to the incident and continued monitoring the lagoon daily throughout the week, cleaning up any additional fish kills resulting from this occurrence. If you observe a fish kill in a lagoon, please call the Public Works Department (912-598-5506).