Permalink : http://hdl.handle.net/2115/68503

JaLCDOI : 10.14943/bull.fish.68.1.17

KEYWORDS : Alexandrium tamarense;Skeletonema;Nutrients;Bioavailability;Osaka Bay;Algal growth potential;Limiting

Alexandrium tamarense is a toxic dinoflagellate known to cause paralytic shellfish poisoning to human and marine animals. Previous studies observed the depletion of macronutrients during the A.tamarense blooming periods in Osaka Bay, Japan, and suggest the different nutrient availabilities between surface and bottom layers allow A.tamarense to grow. In this study, the field observation and Algal growth potential(AGP) bioassay with A.tamarence and non-toxic, dominant diatom Skeletonema sp. in Osaka Bay are conducted to compare the nutrient availabilities during the period of A.tamarense occurrences in the Bay. The field observations confirmed the depletion of dissolved inorganic nitrogen, PO4-P, and SiO2-Si concentrations with the A.tamarense occurences in spring. The phosphorous limitation to both speicies at surface layer were frequently determined by the AGP bioassay in spring. The bioassay also revealed the higher AGP of both species at deeper water than those at surface water and different limiting nutrients between surface and bottom waters or between A.tamarense and Skeletonema sp. These different nutrient availabilities probably allow A.tamarense and dominant diatoms to coexist and grow Osaka Bay during spring.