Ecological Effects of Rockweed (Ascophyllum nodosum) Harvesting

Ascophyllum nodosum, the dominant intertidal macroalgal species from Maine to Canada, plays an important role in buffering intertidal stresses and supports a variety of organisms such as molluscs, crustaceans, fish and birds. A. nodosum is harvested commercially for use in fertilizers and food additives, and landings have been increasing in Maine in recent years. The ecological impact of removing the rockweed canopy was assessed in a comparative study between Kent Island in the Bay of Fundy, New Brunswick, Canada and Orr’s Island in Harpswell, ME, USA. Paired 2x2m control and experimental plots were set up, harvested, and surveyed monthly during the summers of 2013 (15 plots on Kent Island) and 2014 (an additional 9 plots on Kent Island and 20 on Orr’s Island) in a BACI design (Before, After, Control, Impact). One square meter surveys were conducted to determine algal species richness, algal percent secondary cover, and megafauna abundance and diversity. Surveys were designed to assess the overall diversity within plots and count/identify all present species. Initial t-tests of Kent Island data show a short-term reduction in amphipods and isopods, Carcinus maenas (green crabs), and Littorina obtusata (smooth periwinkles) and a short-term increase in Littorina littorea (common periwinkles) (p

Final Report of research funded by the Rusack Coastal Studies Fellowship (2014).