State of the Slough: Spring 2024

Summary of salinity, water level, vegetation, and fish communities in South Florida's Taylor Slough.

At the southern end of Everglades National Park, a series of sloughs convey fresh water to the Florida Bay estuary. Audubon researchers track these freshwater deliveries (or lack thereof) and their impacts on the ecology of Taylor Slough and the Bay. 

The 2023-24 water year started with record-high water levels in June and July. Since then, Taylor Slough has experienced higher-than-normal water levels. The drawdown that started in December was not sucient to bring water levels below 13 cm by the end of January. Roseate Spoonbills need water levels of 13 cm or less for prey fish to concentrate, which in turn helps them feed their voracious chicks. Higher water levels lead to lower nesting success.

Historically, Taylor Slough was a freshwater ecosystem. The salinity pulse in September—possibly the result of a storm—had the potential to negatively impact freshwater plant and fish communities that are sensitive to salt. However, with constant low salinity readings throughout the year, no direct negative eects were noted from this event. Freshwater levels have been stable and consistent—a trend we need to see more to see more of over the next couple of years to allow the system to have time to fully recover. 

The average plant coverage for January through March was 3.6%, which represents a slight decrease compared to last year. This region is still experiencing very low coverage even though freshwater levels have been consistent this water year. We believe that the seedbank (the seeds in the sediment from the freshwater plant species) is low due to several years of highly fluctuating salinity values in the area. It may take the submerged aquatic vegetation longer to recover than we previously expected. 

For the end of the 2023-2024 water year, we caught 72 fish that could be classified as a freshwater species, accounting for 22% of the total catch. Fish community structure shows us how the ecosystem is responding to restoration eorts. A 22% catch of freshwater species is halfway to the restoration target of freshwater species making up more than 40% of the prey base fish community. However, the fish community in this region is currently comprised of 11% Mayan cichlids, an invasive species that prey on native species. 

The freshwater fish population is showing signs of recovery, while the submerged aquatic vegetation may take longer to reach target levels. Our data highlight how important it is to keep salinity levels stable and low over long time periods, thus lengthening the period for these freshwater plants and fish species to establish. Their health is critical to the health of wading birds like a Roseate Spoonbill. 

This infographic originally appeared in the 2024 Spring State of the Everglades report. Click here for more information.

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