When people think of Charlotte Harbor, they often look at the surface… and may or may not be disappointed by the often-brown water they see. Although this color is natural and results from staining by plant material (think tea), it may give the impression that the harbor is not healthy.

But the real story is happening below the surface. There, growing quietly in shallow water, are underwater plants called seagrasses. These plants are living indicators of water quality, and over the past six years, a group of local volunteers has been helping scientists monitor their health. Their work is part of a program called Eyes on Seagrass—and their story begins with a simple observation.

After Hurricane Irma in 2017, people who spent a lot of time on the water—especially fishing guides—started noticing something unusual. They were seeing more algae and less seagrass, and their fishing was suffering as a result! They shared their concerns with their local Florida Sea Grant Extension agent—at the time, Captain Betty Staugler. Working with scientists and local partners, she helped turn those concerns into a structured monitoring effort.

Why Seagrass is So Important

Seagrasses are built like most common land plants. They have roots and leaves, even flowers and pollen! They also have a few adaptations that allow them to survive underwater.

Examples include:

• thin, flexible leaves that allow them to bend and flow in the currents rather than break,
• an underground network called rhizomes that helps hold the plants in place and sprout new shoots.

These features also provide immense value to humans.

• The thin, flexible leaves dampen wave energy and prevent shoreline erosion. They also allow seagrasses to readily capture and store nutrients and carbon dioxide.
• Rhizomes also help capture and store nutrients as well as stabilize sediments, improving water quality.
• The vast underwater seagrass meadows supported by rhizomes are utilized by up to 90% of marine life.

A Shift Toward Algae

Since 2012, Charlotte Harbor (and Southwest Florida in general) has seen increases in macroalgae, sometimes called seaweed. Macroalgae is also a plant adapted to living in the same underwater conditions as seagrass, but it has a different survival strategy… guerrilla warfare. Where seagrasses are highly organized plants with specialized parts that each serve a purpose, algae are much simpler—more like a single multi-use structure. For example, seagrasses absorb nutrients through their roots and move them around their bodies with veins, while macroalgae absorbs nutrients across their entire bodies. With a much larger area for nutrient absorption, they can outperform seagrasses in higher-nutrient conditions, growing rapidly over seagrass and preventing light from reaching it.

Between 2018 and 2021, Charlotte Harbor and Lemon Bay lost an average of 23% of seagrass. The East Wall of Charlotte Harbor lost 50%, primarily due to dense blooms of the macroalgae Caulerpa fastigiata and cyanobacteria that blanketed the meadows and limited light. Think about what would happen if you put a tarp on your lawn!

This is Where Eyes on Seagrass Comes In

Volunteers began monitoring in 2019, before large-scale seagrass loss was detected by researchers. Sampling has occurred every year since, except for 2020. Twice a year, trained volunteers use their own vessels to access and survey seagrass beds using a procedure scientifically rigorous enough to integrate into existing monitoring efforts, but accessible enough to be completed by volunteers. They go out at times of year:

• that were previously unsampled by state agencies and
• that are ecologically significant for macroalgae.

Surveying in April and July provides before-and-after snapshots of seasonal algae growth, since blooms typically begin when waters start to warm up. After five years of sampling, Eyes on Seagrass has become a trusted resource for researchers and natural resource managers. Volunteer data has been:

• presented in local, national, and international research settings,
• used in the creation of regionwide seagrass maps,
• and used to inform research and habitat management in the Charlotte Harbor Estuary.

This weekly blog series is designed to help you get your “Eyes On” all elements of the program, including:

• what five years of data can tell us about the harbor,
• how volunteer data is being used to help manage seagrass habitat,
• the impact participation has had on volunteers,
• seagrass restoration
• Eyes on Seagrass programs in other regions of Florida.

Up next, how do we know we can trust the data?

A special thank you to Dr. Lisa Krimsky (UF/IFAS Florida Sea Grant) and Arielle Taylor Manges (FDEP/Charlotte Harbor Aquatic Preserves) for their input.

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