Studies on the ecological physiology of Porphyra abbottae and Porphyra torta (Rhodophyta): development of new species for mariculture in Alaska

Abstract

Environmental factors affecting the distribution and growth of Porphyra abbottae and Porphyra torta were studied in a research project on the feasibility of nori mariculture in southeast Alaska. In situ abundance of Porphyra abbottae was compared at sites in Sitka Sound, Cross Sound and Chatham Strait. Growth of laboratory cultured Porphyra torta gametophytes was studied in response to nutrients, salinity, crowding and substrate. The seasonal progression of abundance in Porphyra abbottae varied between study sites, with associated differences in water motion and temperature. Double sampling techniques improved accuracy of in situ abundance estimates. Germination and initial growth of cultured Porphyra torta gametophytes were dependent on plant density, and substrate texture affected recruitment. Nitrate positively affected growth and pigment concentration at environmental levels; negative effects of low nitrate were reversible. Porphyra torta gametophytes tolerated low salinity and inorganic carbon at least to half of normal levels.