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photo by Erika Zambellophoto by Erika Zambello

It's a bright Florida day as Captain Gabrielle Mercado reverses her Lady Luck Adventure charter boat out of the slip and motors towards the Choctawhatchee Bay. The emerald green waters of the Gulf of Mexico are just over the dunes in the intracoastal waterway, and she keeps a close eye on her GPS as she moves against the waves.

Every month Captain Mercado collects water quality data and samples for local nonprofit Choctawhatchee Basin Alliance (CBA). CBA staff use the data to inform the public about the changing bay and improve swimmable, fishable waterways for future generations.

photo by - Brandon Foley

Captain Gabrielle Mercado taking water samples.

Captain Mercado grew up nearby: "When I was five years old, I grew a love for fishing with my dad." Today, she's one of the few women charter boat captains in Destin, dubbed "The World's Luckiest Fishing Village" and home to the largest charter fishing fleet in North America.

"When I was 23," she continued, "I was bartending at the time and really didn't care for it, so I was trying to figure out what I wanted out of life. I heard a quote saying 9 times out of 10, your passion is your favorite childhood pastime. That's when it hit me; I've never lost my love for fishing, so, why don't I fish for a living!"

CBA works with over 30 citizen scientist volunteers like Captain Mercado to monitor 132 sites in the Choctawhatchee Bay, Choctawhatchee River, and rare coastal dune lakes. CBA staff have collected and analyzed temperature, dissolved oxygen, conductivity, pH, chlorophyll, and water clarity for more than twenty years. Long-term monitoring allows the establishment of baseline water quality data, which can then be used to help identify areas of poor water conditions, the causes of water degradation, and identify solutions to mitigate poor quality. 

Located in the Northwest Florida Panhandle, the Choctawhatchee Bay is largely protected by a string of barrier islands, undulating with sugar sand dunes and waving sea oats. The white sand originates from quartz in the Appalachian Mountains and draws millions of tourists to the region each year. As Captain Mercado found her first sampling location, she kept the dunes on one side, and the pine trees and coastal neighborhoods on the other.

Aquatic conditions have an impact on fish populations, especially in the productive Choctawhatchee Bay estuary, where salt and fresh water meet. Here, recreational fish find refuge and forage for food as juveniles, dependent on the seagrass, marshes, and protected waters to act as a nursery. Adult fish life cycles follow annual fluctuations of temperature and other conditions within the bay.

For example, at one water quality monitoring site near the center of the bay, surface temperature arcs in a similar pattern every year: heat peaks around August, and reaches the low fifties during the coldest months. 

When locals notice fish kills, CBA can analyze recent water sample data as well as collect red tide samples for the Florida Fish and Wildlife Foundation to try to determine the potential causes and effects of these changes.

photo by - Erika Zambello

For those seeking fish in the bay, knowing general water characteristics helps anglers target hotspots and specific fish varieties. "Different species behave differently," says Alex Fogg, Marine Resources Coordinator for Okaloosa County, which borders the bay, "Flounder spawning is triggered by the cold. They move offshore in the winter to spawn." He continues, "Mullet spawning is triggered by the cold as well. They ball up during the winter."

If temperatures warm in the coming decades as a result of climate change, CBA will be able to analyze how far the new readings differ from historical averages. In addition to flounder and mullet, the bay is known for redfish, sheepshead, and sea trout. Other, non-recreational species, like giant Alligator Gar and Gulf Sturgeon, are also sensitive to estuary transformations.

Noticing change inspired Captain Mercado to join the CBA volunteer team. "I've first-hand noticed a decline in both fish and healthy grass over the years and really wanted to not only learn more but be involved in any way I could."

photo by - Sean Murphy

With a larger boat she uses for inshore chartering, Captain Mercado could take on water quality monitoring in the intracoastal waterway, which can experience high winds and large waves. "I love pretending to be a scientist when I filter the water samples and am really excited to see the results down the road so I can start learning more!"

After anchoring on the pre-determined water quality spot, she gathers two samples to take back to the CBA lab, then tosses a black and white Secchi disk over the side. After the disk disappears beneath the surface, she pulls it slowly back up, recording the distance at which she first makes out its spherical shape once more. Next up: a Hydrolab. Dropping the sensors overboard, she recorded her data on a specially prepared datasheet that CBA staff would later input into the larger database. One site down, five to go, including a trio along Okaloosa Island. Finishing all six stations each month usually takes a few hours. 

photo by - Sean Murphy

The water readings collected by the CBA staff and citizen scientists are available upon request but are also used in county and state reports analyzing ecosystem health, bacteria, and more.

"Without our volunteers and stakeholders like Captain Mercado," Alison McDowell, CBA Director, tells me, "We could never monitor so many sites in our region, across so many different watery environments. The heart of our community and our economy is the bay, and anglers understand that better than anyone."

photo by - Sean Murphy

To learn more about water quality monitoring in the Choctawhatchee Bay and how you can help, visit