It’s been said that seagrass beds are the marine equivalent to tropical rainforests, and their function crucial to the ecological health of Florida’s inshore estuaries. Studies have shown that a single acre of seagrass can produce over 10 tons of leaves per year, supporting as many as 40 thousand fish and 50 million invertebrates. When protected and given the opportunity to flourish it can expand from sparse intermittent patches no larger than a doormat in size, to vast meadows blanketing thousands of acres of shallow bays and lagoon bottoms.
As the cornerstone of Florida’s inshore ecosystem, there’s currently around 2.2 million acres of seagrass, which provide both food and shelter for thousands of marine species including crustaceans, shellfish, finfish, manatees, turtles, birds and other organisms during various stages of development. It also functions as a water quality agent, by trapping sediments and absorbing nutrients from land runoff, providing bottom stabilization and also buffering wave energy.
Named after one of its consumers, the endangered green sea turtle, turtle grass is the most common seagrass found throughout Florida.
For many coastal economies and recreational and commercial fisheries, seagrass is an important commodity of sorts. The Florida Department of Environmental Protection has estimated that just a single acre of this natural resource has an economic value of approximately $20,500 per year, equating to a $45 billion dollar benefit annually statewide.
There are more than 50 recognized species of seagrass in the world, with seven varieties found in Florida. While not a true grass, seagrasses are actually flowering plants called angiosperms that have roots, stems and leaves that can grow in mud, sand and fragmented shell bottom. The roots anchor the plant to the bottom, and an underground organ called the rhizome grows horizontally from the base to provide additional stabilization. The shoots produce blades that conduct the majority of photosynthesis for the plant and provide the substrate of which smaller organisms attach to.
The depth in which seagrass grows is determined mainly by availability of light, with additional factors such as exposure during low tide events, wave action, turbidity and salinity conditions contributing as well. Many factors can influence seagrass health, but the most important is availability of sunlight. As with all green plants, seagrass needs sunlight for photosynthesis to occur, and any impacts that interfere with light transmission through the water column can be detrimental.
Vegetative cover is a common variable in any fish catching equation. When present, your odds of catching fish increase, and when not the opposite seems to occur. While you don’t need to be a marine biologist to determine what species of seagrass you’re casting at, a simple observation of a few indicators can increase your strike ratio.
Finding the right mix of grass and bare bottom is key. While some grass is better than none at all, venturing into a large, uninterrupted meadow of it may only result in more casts than catches. Generally, some type of break, outcropping or convergence of two different types is needed to draw in fish activity.
On the Gulf Coast, Captain Lynn Zirkle scans over the lush bottom of both turtle and manatee grass carpeting Terra Ceia Bay. Here redfish seem to love foraging within these mixed stands, leaving trails that connect back to the sandy potholes where trout prefer to roam. “Big trout will suspend just off the edge hidden back up in the grass and wait for anything that comes over that sand,” says Zirkle.
As always, potholes nestled anywhere within thick meadows of seagrass deserve investigation, but in very clear conditions a long fluorocarbon leader should be attached to your offering, as sandy spots give way to shadows that may prevent potential strikes from occurring.
While gin clear water flowing over waving blades of seagrass is what most of us visualize as fish utopia, Captain Bouncer Smith probes the shallows of Biscayne Bay looking for just the opposite. “I try to locate grass beds in water where I can see a stain over it, rather than being clear. You’ve heard of mullet muds, haven’t you?” He said. “Well, trout, ladyfish, pompano and even flounder will stir up the bottom in those grassy areas while feeding just like the large schools of mullet do, exposing tiny fish, shrimp, crabs and eventually themselves.”
In Stuart, near the mouth of the St. Lucie Inlet along the southern tip of the Indian River Lagoon, Captain Mark Nichols wades along the deeper edge of a tide-scoured bar, where only a few sparse patches of seagrass remain. “These days I’m looking for any grassy spots that I can find along the edge of the flats,” he tells me while casting across what appears to be just sand. “On the outgoing tide, baitfish are forced off the bar and into this area looking for any cover they can find, where hopefully we’ll find snook and trout.”
While some areas of the state, primarily along the Gulf Coast, are seeing wonderful improvements in seagrass recovery, other areas are diminishing. While many natural causes such as storms, droughts, flooding and overgrazing by sea turtles and manatees can degrade seagrass stocks, it’s the human impacts such as dredge and fill projects, prop scarring, industrial discharges and overland runoff sources that we must improve upon in order to mitigate for this precious resource. An estimate conducted in 1950 determined that Florida contained around five million acres of seagrass. Today, less than half of that remains. Class dismissed!
Named after one of its consumers, the endangered green sea turtle, turtle grass is the most common seagrass found throughout Florida. Recognizable by its wide, green blades, this species has the largest root system of all the seagrasses. It can grow into large mono‑specific stands in depths that range from barely a foot, to twenty feet or more depending on water clarity. Its range is limited by temperature and does not occur along the northeast coast of Florida. However, it thrives in warm tropical climates and in areas of high salinity, accounting for 95-percent of all the seagrass found in Florida Bay.
Endemic only to Florida, Johnson’s seagrass is the rarest of Florida’s seagrasses and is listed as threatened under the U.S. Endangered Species Act. It occurs only between Biscayne Bay and Sebastian Inlet on the East Coast of Florida.
While not a true seagrass, widgeon grass is actually a freshwater plant with a high salinity tolerance that can grow in both fresh and saltwater environments. It grows extensively in canals, estuaries, marshes and shallow areas where exposure to sunlight is high. Healthy beds can be found within the southern portion of the Mosquito Lagoon near Titusville.
The second most common seagrass found throughout Florida, manatee grass is distinguished by its cylindrical appearance with long, straight-leaf blades that can reach lengths of up to twenty inches. It can be found commonly growing with other species of seagrasses such as turtle and shoal, but will form large meadows as well.
Known as a pioneer species, shoal grass is a rapidly growing early colonizer that can be found in areas that have been previously disturbed. It is currently being used for the Indian River Lagoon Seagrass Transplant Project conducted by the St. Johns River Water Management District where since 2011, some 50,000 acres of seagrass were lost as a result of several large algae blooms. The restoration project harvests plugs of shoal grass from healthy beds located in Titusville and Vero Beach, and replants them within barren areas of the IRL and the Banana River Lagoon in an effort to study the viability of transplanting.
A small species standing less than two inches tall, paddle grass gets its name from its oblong paddle shaped leaves. It grows in deep water with low light levels in depths ranging from about 30 to 100 feet. It provides important habitat for offshore grouper and snapper fisheries, and serves as a migration corridor for other fish and shellfish species that migrate inshore.
A close relative to paddle grass, star grass is also diminutive in size, rarely exceeding four inches in height. Identifiable by its star-like whorl of five to seven leaf blades, it can tolerate lower light intensities and relatively high levels of turbidity. It is found in both shallow water and at depths close to 300 feet in clear waters. Found throughout the northern Gulf region of Florida, its habitat is generally in sandy and muddy substrates, but it can also be found in areas with rocky bottom.