Saving Seagrass From Scarring

Vital to marine ecosystems, seagrasses provide food, habitat, shelter, and numerous other services for humans and aquatic organisms. These include the fish, crustaceans, and shellfish essential for Florida's recreational and commercial fishing industries. Read on to learn how boaters can play a part in conserving seagrass communities.

Have you ever wondered what your boat's hull or motor is experiencing underwater? Chances are it might be damaging seagrass.

Seagrass scarring, sometimes referred to as prop scarring, is exactly what it sounds like. As boaters putter over shallow waters, their propellers may slash or otherwise disturb seagrass below, leaving visible "scars," or areas with no vegetation. Some injuries are only to the seagrass leaves and stems, but the boat's hull and motor can cause physical damage to the seagrass' crucial root systems. Seagrasses have an extensive network of roots that anchor them to the seafloor and allow them to form large meadows. When this more significant damage occurs, these scarred areas take years to recover and grow, and repeated damage can prevent recovery completely.

Damage to seagrass is especially considerable near high traffic areas such as channels, marinas, residential areas, and urbanized areas. In South Florida, for example, boat propellers have scarred over 30,000 acres of seagrass — that is about the size of 30,000 football fields! When boating activities increase, seagrass scarring likely also increases.

From the water, the extent of the damage to seagrass beds is sometimes difficult to see. From a birds-eye view, however, it becomes much clearer.

Healthy seagrass beds provide homes for marine organisms, play critical roles in improving water quality, and support local and regional economies! Amid much more complicated threats to seagrass, such as poor water quality, coastal development, and climate change, scarring is something we can work to address individually and as a community.

Seagrasses support commercial and recreational fishing and nature/wildlife tourism — two significant industries in Florida's economy. About 70% of fish species in the state spend at least part of their life cycle in seagrass communities, so to protect these resources, effective habitat and fisheries management is necessary.

Seagrasses also ...

• ... sequester about 10% of the carbon buried in ocean sediment annually.
• ... improve water quality by trapping fine sediments suspended in water that would otherwise lower water quality.
• ... stabilize sediments and prevent erosion along Florida's coastline, an especially critical function during hurricanes and storms.
• ... filter nutrients in the water coming from land-based stormwater runoff and industrial discharge.
• ... provide food and habitat for other marine organisms, including manatees and sea turtles. 

Explore the slides below to learn about the wildlife that depend on and interact with seagrass!

The St. Martins Marsh Aquatic Preserve is in the Homosassa and Crystal River areas in the Nature Coast region along Florida's Gulf coast about 1.25 hours north of Tampa. Both regions are frequently used for inshore recreational fishing due to their shallow clear water. As an important part of the local and regional economy, these areas benefit locals and visitors alike. Recent increases in fishing and boating traffic have also increased the likelihood of propeller scarring.

Results from a study conducted in 2021 indicated that propeller scars are present throughout the area, with severe scarring concentrated around certain islands. In fact, researchers identified more than 256,000 linear feet of light scars and an additional 109,500 linear feet of other scar types, mostly dark scars. The majority of these scars can be attributed to outboard motors.

Motors and propellers also caused significant disturbance to hardbottom communities. These are crucial habitats that consist of rocks and other hard surfaces that aquatic organisms like sponges and coral can attach to.

Explore the map below to view the results in further detail!

The best and easiest solution to this problem is prevention. Seagrass scarring is avoidable with a few good boating habits.

Research has shown that when people take a pledge to do a certain behavior, they are more likely to follow through. Take the following pledge to protect seagrass!

Marine habitats occur where they do based on factors such as salinity, water depth, temperature, and many others. The three habitats discussed here are mangroves, seagrasses, and coral and oyster reefs. All three provide wave/storm protection, reduce coastal erosion, provide habitat for numerous species, and play critical roles in Florida's fishing industries. Mangroves grow right near the water's edge. Seagrasses are in the middle, fully submerged in shallow waters. Their exact location and depth vary depending on water clarity, but most seagrasses need roughly 20% of incoming light to reach the bottom surface. If you can see the bottom from above the water, that usually means there's enough sunlight for seagrass! Coral and oyster reefs are the habitat farthest from the coast, and their location and depth also vary depending on the type of reef.

The image offers a closer look at seagrass' root systems and how they differ from those of algae. While both are underwater aquatic plants, they differ in many ways. Algae (seaweed) is much less complex than seagrass and have no flowers or veins. They do not have actual roots, only a root-like structure called a holdfast, and cannot absorb nutrients like seagrass! Seagrasses grow vertically and horizontally to capture sunlight and nutrients from the water and sand. Their blades grow up and their roots down and to the side.

• Sponsor an educational sign to be placed at your local boat ramp by emailing beseagrassafe@gmail.com!
• Read more about  St. Martins Keys  and the findings regarding seagrass scarring in the region.
• Learn more about ...
  • . .. seagrasses in Florida. 
  •  ... seagrass kill-off. 
  •  ... the importance of seagrass. 
  •  ... the wildlife that depends on seagrass. 

To find what is being done around your area, visit your  local aquatic preserve , contact Florida  Department of Environmental Protection  staff, or explore the Florida Fish and Wildlife Commission's  seagrass monitoring and mapping program .

Have more questions? Contact us at beseagrasssafe@gmail.com or (352) 325 - 6080.

Florida Sea Grant is a university-based program that supports research, education and extension to conserve coastal resources and enhance economic opportunities for the people of Florida.