Seagrass is essential to Keys life

A sea turtle rests in seagrass off the Upper Keys.
A sea turtle rests in seagrass off the Upper Keys.

What does seagrass have to do with diving in the Florida Keys? It seems a lot.

Florida takes its seagrass very seriously. If you are a visitor to the Keys and haven’t used your boat here before, it may be a good idea to obtain a booklet of regulations (see https://www.boat-ed.com/florida/handbook/page/36/Protect-Florida%E2%80%99s-Seagrasses) or view http://floridakeys.noaa.gov/regs/welcome.html.

Boaters can face federal and state fines as well as costs associated with restoration efforts and monitoring if they are caught destroying seagrass. A fine of up to $1,000 can be imposed under Florida law.

Bring in the feds and things get more serious. In 1997 federal judge ordered a treasure-hunting company to pay a fine of $589,311 for destroying sea grass while searching without a permit for shipwrecks in the Florida Keys National Marine Sanctuary.

Seagrass damage aside, running aground costs millions of dollars each year to boaters in towing fees, propeller replacement and engine repairs.  

So what is the big deal about seagrass?

It is valuable to the health of our ocean, marine life and Florida’s economy. Estimates are that more than 70 percent of all recreationally and commercially important fish species are dependent on sea grass at some point in their lives.  

The high level of productivity, structural complexity, and biodiversity of seagrass has led some researchers to describe it as the marine equivalent of tropical rainforests.

In 2014 alone, seagrass in Monroe County supported an estimated harvest of roughly $380.5 million for stone crab, spiny lobster, shrimp, yellowtail snapper, gray snapper and blue crab. (FFWCC, Annual Landings, 2014)

Florida’s approximate 2 million acres of seagrass (and the organisms that grow on them)   provide shelter and food for fish, crustaceans, shellfish marine mammals, like our friends the manatees, and birds. 

A single acre of seagrass can produce over 10 tons of leaves per year, providing food, habitat, and nursery areas, supporting as many as 40,000 fish, and 50 million small invertebrates (http://www.sms.si.edu/IRLspec/Seagrass_Habitat.htm).

Seagrass is recognized as an important indicator of water quality and the health of coastal ecosystems. It helps maintain water clarity by trapping fine sediments and particles and stabilizing the ocean the bottom.

Worldwide, there are 60 species of seagrass. Seven of those varieties grow in 2.7 million acres of seagrass meadows along Florida's extensive coastline, protected bays and lagoons.

Turtle grass, manatee grass, and shoal grass are the most common types of seagrass in the Keys.

The bad news is that seagrass are disappearing at an alarming rate from coastal development, climate change, pollution, harvesting and vessel damage.   

Damaging seagrass with a boat’s propeller fragments the grass, creates barren areas and restricts the movement of marine wildlife. 

If only leaves are damaged, seagrass can recover in a few weeks. But more extensive damage to the plant can lead to a recovery period of over seven years, if at all.

Because seagrass is so intertwined with the sea’s hard bottoms and coral, damaging seagrass has a negative effect on the coral reef.

Is seagrass really grass?

It turns out — no. Seagrass is a grass-like flowering plant that lives submerged in water. Most seagrasses have separate sexes and produce flowers and seeds, with embryos developing inside ovaries. They can also reproduce asexually by sending out shoots under the sediment. 

Unlike land plants, seagrasses do not have supportive stems and remain flexible in the actions of waves and currents.

The depth at which seagrass grows is controlled by water clarity, which determines the amount of light reaching the plant. Sufficient light is required for the plants to grow and make food through photosynthesis (a process to convert light energy into chemical energy stored in carbohydrate molecules such as sugars).

Seagrass also uses carbon dioxide and gives off oxygen, which is good for the ocean, you and me. 

If you are a diver it can be interesting to move off the reef above a bed of seagrass, especially on night dives. Many fish that find shelter on the reef during the day swim to the seagrass at night to feed.

Day visitors to grass beds include nurse sharks and southern stingrays.

Besides fish, who needs seagrass? Seems reptiles, birds and mammals do.   

The American crocodile, which lives in the shallow waters of Florida Bay and the northern Florida Keys, is known to feed in sea grass beds.

The main food of the green sea turtle is turtle grass. 

The Great White Heron, with a very small distribution that is restricted to Florida Bay and the Florida Keys, has undergone a substantial decline. This probably is due to decreasing fish availability, in turn is tied to losses of sea grass beds.

Manatees feed on seagrass and bottlenose dolphins go to the shallow depths of the grass beds to find prey.   

 “To give seagrasses a chance, we gotta take a stance. It’s up to you to choose; Or, we’ll be singing the bluegrass carbon blues.” (For full credits and to listen to song go to https://www.youtube.com/watch?v=U8KOOd9uzTE)

March is “Seagrass Awareness Month.” Preserving Florida's seagrass is critical to protecting marine life, water quality and Florida’s ocean-based economy.

Learn more about seagrass at: www.dep.state.fl.us/coastal/habitats/seagrass/ 

Don Rhodes, in addition to a career in government affairs, has taught scuba for 28 years. He and his wife retired to Tavernier three years ago, where he works as an instructor for Conch Republic Divers.