Development of Sustainable Seaweed Aquaculture on Alabama’s Gulf Coast

Development of Sustainable Seaweed Aquaculture on Alabama’s Gulf Coast

Summary

Seaweed production in the United States has gained attention among farmers and scientists alike due to the high nutritional value, bioremediation properties and potential for integrated aquaculture systems with fish, shrimp and shellfish. The northern Gulf of Mexico appears to be an ideal location for seaweed aquaculture to provide oyster farmers with a secondary product and to reduce eutrophication in the surrounding ecosystem. A variety of macroalgae species found in Alabama will be evaluated in terms of their suitability for culture. The candidate species include, Ulva lactuca, Grateloupia taiwanensis, Hydropuntia secunda, and Chondria littoralis. Each species will be cultured from an algal seed stock and grown out on suspended long­lines in coastal Alabama waters at two different sites. Seasonal algal growth rates will be compared between open water culture sites and sites around oyster cages, for all four tested species. Nutrient composition of the cultured seaweed will be analyzed to determine the nutrient removal capacity and nutritional value. The outcome of this work will be presented to oyster farmers, chefs and consumers to investigate the market acceptance and potential for seaweed aquaculture on the Gulf Coast as a standalone farm or integrated system with oysters.

Objectives/Performance Targets

Objective 1. Compare the growth rate of Ulva lactuca, Grateloupia taiwanensis, Hydropuntia secunda, and Chondria littoralis cultured in the vicinity of oyster cages and in the open ocean.

Objective 2. Compare variations in the seasonal growth rate of Ulva lactuca, Grateloupia taiwanensis, Hydropuntia secunda, and Chondria littoralis across each season.

Objective 3. Evaluate the nutrient removal efficiency and nutritional value of each species.

Objective 4. Present the results to oyster farmers, chefs and consumers to assess the market acceptance and potential for seaweed aquaculture on the Gulf Coast.

Accomplishments/Milestones

Objective 1. Compare the growth rate of Ulva lactuca, Grateloupia taiwanensis, Hydropuntia secunda, and Chondria littoralis cultured in the vicinity of oyster cages and in the open ocean at two locations in Alabama.

After four weeks, C. littoralis achieved a growth rate of 34.2 g/day inside the oyster farm and 29.3 g/day outside the oyster farm, but this difference was not significant. Growth rates did not significantly increase after an additional two weeks. This growth was observed at the location characterized by weak wave action and high turbidity, while the location characterized by stronger wave action and clearer water showed little growth and significant biofouling. Water and tissue analysis currently underway will help determine whether nutrient differences could also be a determining factor for growth at the two sites.

Sporulation and seeding methods of U. lactuca have been successful in culturing germlings attached to rope and field trials will begin in the upcoming weeks.

Objective 2. Compare variations in the seasonal growth rate of Ulva lactuca, Grateloupia taiwanensis, Hydropuntia secunda, and Chondria littoralis across each season.

Growth trials in the summer and fall of 2016 were unsuccessful in producing a viable crop for all four seaweed species, with results from spring trials pending. Out of the species cultured so far, C. littoralis and U. lactuca appear to have the most potential for growth. The species, G. taiwanensis and H. secunda, did not grow at either culture site.

Objective 3. Evaluate the nutrient removal efficiency and nutritional value of each species.

Samples are currently being processed.

Objective 4. Present the results to oyster farmers, chefs and consumers to assess the market acceptance and potential for seaweed aquaculture on the Gulf Coast.

All four species were presented to the executive chef of Fisher’s Upstairs in Orange Beach, Alabama for sampling. Based on his feedback, the species, G. taiwanensis and U. lactuca, have the most potential to be sold to restaurants. We recognize that this is an informal assessment of market acceptance, and hope to conduct similar qualitative interviews with other chefs later this year. 

Impacts and Contributions/Outcomes

This project provides an initial analysis of the potential of seaweed aquaculture in the gulf and aims to spark more interest on the subject. I plan to host a sampling event at Fisher’s to showcase the product to customers and try out different ways the seaweed could be presented at restaurants. I have received encouraging feedback and interest from both farmers and researchers in starting polyculture systems at oyster farms along the Gulf coast. The four species tested in this project will be ranked according to their suitability for culture which will create a framework that individuals in the field can base future projects off of.

Collaborators: