SBEP Director’s Note: Mangroves, Mangrove Trimming and Water Quality
From Sarasota Bay Estuary Program Director Dave Tomasko:
Recently, there has been a quite a bit of concern raised about the topic of mangrove trimming, and potential impacts to the bay’s health from what some refer to as “excessive” trimming. To be clear, the SBEP is not a regulatory agency – we issue no permits and have no formal role in the determination of what is and what is not allowed to occur with mangrove trimming. However, the recent attention to mangrove trimming is a good way for us to highlight the topic of mangroves and their importance, including benefits to water quality.
We all know that mangroves are important for the seabirds and wading birds in our region. I live on the shoreline of Terra Ceia Bay, and a mangrove island in the southeast part of that bay is magical place to see pelicans and egrets and roseate spoonbills in the wild. To reproduce, these birds need protection from predators such as outdoor cats (bad idea) and racoons, and mangrove islands provide the refuges from predation that allow them to continue to exist in our region. Simply put, lose the mangrove islands and you can lose our seabirds.
Mangroves are also incredibly important features for fish as well – as any angler knows. If you’re not aware of the importance of mangroves, fish along the mangrove fringe on a high tide. Spotted seatrout and red fish and mangrove/grey snapper are common, and early life stages of snook and tarpon use mangrove fringes as well.
Mangroves protect our shorelines from erosion and damage from storm surges – a topic well documented across the globe. Natural shorelines are much less impacted by storm surge than hardened shorelines – a fact obvious to anyone who has worked in hurricane relief efforts or who spends enough time on the water.
Mangroves are also important for water quality. The prop roots of red mangroves are attachment sites for oysters and barnacles and sponges and other filter feeders. Mangroves forests also filter out pollutants from upland sources. In the summer of 2020, more than 10 million gallons of raw sewage gushed out of a hole in the sewer line that takes wastewater from Longboat Key to Manatee County’s Southwest Treatment Plant. Perhaps because the spill occurred several hundred feet into a mangrove forest, no elevated levels of fecal indicator bacteria were found in the bay after the leak, even right next to the shoreline.