COS 36-3 - Validating nitrogen mitigation potential of kelp farms in the Gulf of Maine nearshore marine ecosystem

Tuesday, August 8, 2017: 8:40 AM
B112, Oregon Convention Center
Gretchen Grebe, School of Marine Science, University of Maine, Orono, ME

Interest in farming seaweed using aquaculture techniques has skyrocketed in the Americas and Europe. While much of this new industry is focused on growing seaweed for final use in food products or pharmaceuticals, eco-entrepreneurs along more urbanized coastlines see the potential for seaweed farming to be used in nutrient mitigation banking schemes. The objective of this study was to validate the potential for marine farmers growing sugar kelp (Saccharina latissima) in the western Gulf of Maine to lay claim to the nutrient offset mitigation banking potential of their current activities. Existing studies have quantified the total nutrient removal offered by sugar kelp over a calendar year, but they do not take into account finer resolution fluctuations in the nearshore ecosystem. The Gulf of Maine is a prime location for continued research on this topic because it has significant tidal, meteorological, and nutrient variation and is also one of the most vulnerable U.S. coastlines when it comes to ocean acidification.


Sugar kelp samples were collected from three farm sites during the spring and winter of 2016. Each sample was analyzed for nitrogen and carbon content and stable isotope ratios. Preliminary results depict a clear spike in nitrogen isotope ratios found within the kelp samples after a rain event greater than 1 inch. They also show that nutrient use by cultivated sugar kelp is not consistent throughout the growing cycle. The preliminary results from this study suggest that more sophisticated calculations should be considered by both kelp farmers interested in claiming nutrient offset mitigation credits and resource managers facilitating these arrangements.