Quantifying Ecosystem Structure and Services Provided by Tropical Seaweed Farms

There is growing interest in large-scale seaweed farming of tropical seaweeds, for carrageenan to be used in food and pharmaceutical products, and potentially in fertilizer, animal feed, and biofuel feedstock. In particular, there is interest in exploring the possibility of implementing commercial Eucheuma isiforme farms in the Caribbean. While there is research ongoing to determine the best practices for the production and harvesting of a seaweed crop, there is little information regarding the potential impacts that large scale farms could have on the surrounding ecosystem. Here I estimate the effects of Eucheuma isiforme farms on the ecosystem structure and the ecosystem services provided by the introduction of significant seaweed biomass. The steady state biomass of fish under a 20 km² farm may range between 290 and 38,000 tonnes with an additional 2,200 to 4,900 tonnes of fish utilizing the farm as a nursery habitat. The availability of nitrogen could be a limiting factor in the structure and design of a seaweed farm. Carbon dioxide cycling may create a pH change as large as 0.3 pH units in the water down-current. The primary productivity of the model farm is comparable to overall aquatic tropical systems as well as surface pelagic waters in the Virgin Islands. Therefore, the introduction of a commercial Eucheuma isiforme farm has the potential to change the ecosystem where it is deployed in many positive ways.