Blue Crabs and Changing Habitats in the Indian River Lagoon

By Jackson Evans

Master of Science student, Integrated Environmental Science

Bethune-Cookman University

Photo courtesy of Jackson Evans

The Indian River Lagoon (IRL) on Florida’s east coast has seen big changes in recent years. Once covered in lush seagrass meadows, stretches of the lagoon floor are now dominated by seaweeds, or macroalgae, such as Gracilaria tikvahiae (red alga) and the non-native Caulerpa prolifera (green alga).

These changes have raised an important question for scientists and anglers alike: Can seagrass-dependent organisms such as blue crabs, who use seagrass beds as their refuge, feeding and nursery habitat, still find what they need when seagrass disappears?



Blue crabs (Callinectes sapidus) are a key species in the IRL, supporting local fisheries and playing an important role in the ecosystem as both predator and prey. My research looks at whether these new macroalgal habitats can provide the same shelter and food that seagrass beds once offered.

Using data from the Florida Fish and Wildlife Conservation Commission (FWC) and the St. Johns River Water Management District (SJRWMD), I’m examining how blue crab populations have changed as seagrass has declined. I also ran experiments at the Marine Discovery Center in New Smyrna Beach, where juvenile crabs were given a choice between seagrass and macroalgae habitats in a controlled environment. The seagrass and macroalgae used in the experiments were collected from nearby sites within the Indian River Lagoon, while the juvenile crab population was sourced from the Florida Panhandle near Panacea, Florida.

Based on my study so far, blue crabs appear to use both seagrass and macroalgae for shelter, suggesting that these seaweeds may offer a temporary refuge as seagrass struggles to recover. However, not all macroalgae provide the same benefits, as they are not rooted like seagrasses are. In addition, the structural provision to the juvenile crabs is different between macroalgae and seagrass beds. Therefore, understanding these differences would be key for managing the lagoon’s future.

By learning how crabs adapt to a changing habitat, this research output would inform conservation and fisheries management, helping to ensure that the Indian River Lagoon continues to support healthy ecosystems and coastal communities for years to come.