Seagrass: a healthy resource?
An algae bloom south of Tidy Island covers hundreds
of acres of once lush seagrass.
The seagrass beds that carpet Anna Maria Sound and extend south through Sarasota Bay harbor a tremendous array of living creatures. This critical and diverse ecosystem is mostly out of sight, except at extreme low tides. While it might be hard to believe, seagrasses are flowering plants that serve a number of important functions. Because they flower, seagrasses require sunlight and are limited to clear, shallow waters. They produce oxygen, bind sediments and baffle wave action while cleansing coastal waters.. Seagrass roots, their leaves and the epiphytes and micro algae that cling to them clean water by converting dissolved nutrients into plant matter. Besides giving us clean and clear water, sea grasses are home to the organisms that provide food and shelter for fish, crustaceans, shellfish, manatees and wading birds.
Of the 52 species of seagrasses worldwide, only seven are found in Florida. On Florida's west central coast they include turtle (Thalassia testudinum), shoal (Halodule wrightii) and manatee grasses (Syringodium filiforme). The historical loss of these species has been extensive throughout Florida. Tampa Bay has lost 81 percent of its historical cover, Sarasota Bay 35 percent and Charlotte Harbor 29 percent. Poor watershed management (storm water run-off and sewage disposal) dredge and fill operations and scaring from boats have taken a heavy toll on Florida's seagrasses.
Fortunately the influence of citizens through organizations like Tampa Bay Watch, the Tampa Bay Estuary Program, Sarasota Bay Watch and the Sarasota Bay Estuary Program have instituted programs that are beginning to turn the tide on water quality. The most important of these has probably been the elimination of small, poorly maintained regional sewage systems.
Anglers, from experience, are aware of the importance of these prolific, shallow beds. They experience first hand the myriad interactions that produce fertile fisheries. They may not understand the intricate web of existence that proceeds from the microscopic level to the fish on the end of their line, but they reap the benefits nonetheless. Government scientists (NOAA) consider seagrasses to be of such importance that they have adopted a no net loss policy to manage them. Despite this noble pronouncement seagrasses remain under assault.
Preventing the loss of valuable seagrass beds must be a higher priority. Watershed management, replanting, avoidance of direct impacts to existing grasses and mitigation are avenues to reach those goals.
Mitigation involves the replacement of seagrasses impacted by residential and commercial development. In theory there should be at least one acre (more is required) of seagrasses created (that flourishes and survives) for every acre that is destroyed. However the literature reveals that the effectiveness of mitigating seagrass damage is considered, even among the leading wetland scientists, as marginal at best.
We've heard a lot of pronouncements recently about how seagrass has rebounded in Sarasota Bay. Many reports have touted the increased acreage that has been recorded in recent years. I hope they are correct, but the condition of many flats from Cortez to Longbar has me concerned. An algae bloom just south of Tidy Island is the worst I've seen in 30 years. The algae has completely covered hundreds of acres of seagrass. These were recently some very healthy seagrass beds that have traditionally been home to healthy populations of snook, redfish and trout. In some places seagrass can be seen through the algae bed, while in other places they are completed covered. Blooms like this have come and gone in the past, but I'm concerned that we're not paying enough attention to the causes and effects of these insults to the bay.
Fortunately, I'm sure that with some input from the public and some changes in policy the bay will respond favorably. One thing I'm sure of, if we don't pay attention and demand action things will only get worse.
It is a foregone conclusion that development will continue to impact coastal areas and their seagrass resources. It is vital that decisions are made that will allow needed development while protecting the quality of our most valuable local resources. Enlightened citizens, anglers and their interest groups must take part in this decision making process. Cost considerations often eclipse concerns for seagrasses, but research reveals the true value of these resources. A study (Virnstein and Morris 1996) conducted in the Indian River Lagoon estimated the value of seagrass to be $12,500 per acre, per year, based solely on economic values derived from recreational and commercial fisheries.
Having established the importance, both ecologically and economically, of seagrasses, it is crucial that we develop rules and procedures that assure we maintain (no net loss) the current standing stock. A wiser decision would be to enact management policies mandating an increase in these "rainforests" of the sea.