Development of Seaweed Aquaculture In the Northern Gulf of Mexico  

Seaweed production in the United States has gained attention among farmers and scientists alike due to its high nutritional value, bioremediation properties and potential for integration into multi-trophic aquaculture systems. While kelp farming is developing along the Atlantic and Pacific Coasts, little research has focused on open water cultivation of seaweed in the Gulf of Mexico. The northern Gulf of Mexico has potential to be an ideal location for seaweed aquaculture and could be integrated with existing oyster farms in protected coastal waters. In doing so, the integration of seaweed could benefit oyster farmers by providing a secondary cash-crop and benefit the ecosystem by reducing eutrophication in the surrounding waters.

To address the feasibility of seaweed farming in the northern Gulf, three species of macroalgae, Ulva lactuca, Grateloupia taiwanensis and Chondria littoralis were cultured on suspended long-lines in coastal Alabama and Florida at two different sites, between oyster cages and 30 m upstream from the cages. To prepare for grow-out of U. lactuca, an artificial seeding method was developed under controlled laboratory conditions to manage seeding density and biomass production. For artificial seeding, the collected thalli were first cut into 1 mm and 2.5 mm discs to induce zoospore release. Once a sufficient number of zoospores had been discharged, the suspension was added to prepared spools of polypropylene rope (24 m, 12 m/site) and cultured for 3 weeks to ensure successful attachment. G. taiwanensis and C. littoralis were prepared for grow-out by vegetative propagation of the thalli into equally sized fragments. The fragments were bundled at a density of 10 g, and spaced 10 cm apart on 12 m of polypropylene rope (6 m/site). Growth rates were determined by harvesting three meters of rope per species after four and six weeks in each season (summer, fall, spring). The cultured species were collected for tissue analysis and compared to water samples at the two sites to evaluate differences in nutrient uptake.

Trials during the summer and fall suggest that year-round cultivation of U. lactuca, G. taiwanensis and C. littoralis in the northern Gulf of Mexico is not feasible and is likely due to high water temperatures. Trials in spring 2017 are currently underway and results evaluating the growth potential of the species will be presented.