Epiphytism on Blades of the Edible Kelps Undaria pinnatifida and Saccharina latissima Farmed under Different Abiotic Conditions

The kelps Undaria pinnatifida and Saccharina latissima are economically valuable edible seaweeds. Although epiphytism is a major problem affecting the productivity and quality of farmed seaweeds, studies of its effects on kelp aquaculture are scarce. We investigated the effects of epiphytism in two U. pinnatifida and S. latissima culture grounds located in two different parts (exposed and sheltered) of a bay (ria) in Galicia (NW Spain). Epiphytic organisms on blades were identified and their abundance was documented. The percentage of the total blade covered with epiphytes was measured for both kelp species in order to estimate the blade biomass that must be discarded during processing for human consumption. Algae, hydroids, and crustaceans were the most common epiphytic organism on kelp blades; colonies of the hydroid Obelia geniculata and harpacticoid copepods were the most abundant epiphytes. Abundance of epiphytes on the blades of both kelps was significantly higher for fronds growing in the sheltered area of the bay compared to those farmed at the exposed location. Different environmental conditions and other factors, such as the proximity of mussel cultures to kelp cultures, may be important contributors to epiphytism. The results presented here can be used to devise better ways for kelp aquaculture facilities to diminish the negative effects of epiphytism.