Survey on harmful algae in the coastal areas of southern Iwate Prefecture

Representative Organization: Tohoku University

2015/04/01 - 2016/03/31
Every one / two month

Ofunato Bay and Okirai Bay

Field survey

In the Sanriku coast, aquaculture such as bivalves have been developed, however, shellfish poison phenomenon associated with the occurrence of toxic micro-algae has become one of the most serious problems. In Ofunato Bay, abundance of cyst of dinoflagellate that cause paralytic shellfish poison increased significantly, and degree of shellfish poison has become a serious problem. On the other hand, amnesic shellfish poisoning (ASP) is caused by domoic acid (DA) generated by Pseudo-nitzschia diatom, cause poisoning by poison accumulates in fish and shellfish through the food chain. P. multiceries, a highly toxic species is distributed around Sanriku coastal area, and scallop and mussels are poisoned by this diatom. The occurrence of these harmful algae is serious problems in fisheries. The present study aimed that to reveal the abundance and distribution of these harmful algal cysts and occurrence and toxicity of ASP diatom.

1. Harmful dinoflagellate (Benthic and sessil dinoflagellates) 14 species of dinoflagellate were appeared. Prorocentrum lima occurred year-round, however, other species appeared mainly in summer season. (Motile cell) Alexandrium tamarense appeared before summer, and A. catenella appeared between summer to fall. Abundance of Dinophysis fortii and D. tripos were enough to occurring DSP. These appearance patterns were similar to before 2011 great earthquake. Prorocentrum micans occurred high density in center of Okkirai Bay. 2. ASP microalgae research (P. multiseries) Domoic acid was detected from net samples collected in Ofunato Bay and Okkirai Bay. Potential of toxicity of P. multiseries was confirmed. (Toxicity analysis of shellfish) DA contents of scallop and mussels were analyzed, however, all under detection limit. (N.navis-varingica analysis) Showed a high of 2.9 pg / cell was examined the poison-producing ability. However, the distribution at the same point as before the Ofunato Bay its distribution have been previously validated earthquake was not observed.

FY2015 Survey on harmful algae in the coastal ares of southern Irate Prefecture