Possible involvement of hemolytic activity in the contact-dependent lethal effects of the dinoflagellate Karenia mikimotoi on the rotifer Brachionus plicatilis

We investigated the effects of two strains (SUO-1 and FUK) of the dinoflagellate Karenia mikimotoi on the rotifer Brachionus plicatilis. The SUO-1 strain was highly toxic to rotifers, whereas the FUK strain was less toxic. After 10-h incubations, the survivorship of rotifers exposed to SUO-1 and FUK was 20% and 95%, respectively. Both the cell-free culture supernatant and the ruptured cell suspension prepared from these strains were not toxic to rotifers. Furthermore, when direct contact between K. mikimotoi and rotifers was interrupted with a cell-impermeable membrane (3-μm pores), the toxicity of both the SUO-1 and FUK strains of K. mikimotoi to rotifers were completely inhibited even after a 24-h exposure. Cell suspensions of SUO-1 showed hemolytic activity toward horse erythrocytes, but the FUK strain did not. The cell-free supernatant and the ruptured cell suspension of SUO-1 showed no significant hemolytic activity. These results suggest that this highly toxic strain of K. mikimotoi causes lethality in rotifers by direct contact in which live cell-mediated hemolytic activity might be a contributing factor

Studies on the mechanism of red tide occurrences in Hakata Bay : I. On the regional distribution of organic matter in bottom mud

Fukuoka Bay can be divided into three main parts, viz., entrance of Fukuoka Bay, Imazu Bay and Hakata Bay. During February, May, and November, 1970, the bottom mud samples were collected from Fukuoka Bay, especially from Hakata Bay. Pigments content, ignition loss (%), and C/N value of these bottom muds were measured, and were deduced the distribution of organic matter from these results and discussed their characteristics in the water area where red tides occurred frequently. 1) About 90-100% of pigments contained in bottom mud were pheo-pigments, and distribution pattern of pigments content in each month were associated with the current in the water area. 2) Ignition loss (%) at 800℃ took a larger value as much as 60-120% in excess of that at 500℃. Distribution pattern of ignition loss (%) corresponded to that of pigments content. 3) Distribution pattern of C/N value was in relation to that of pigments content. 4) Basing on the special characters of bottom mud deduced from the relationship between ignition loss (%) and C/N value, it is possible to divide Fukuoka Bay into four areas, viz., a) Imazu Bay and sea route, b) West-Hakata Bay, c) East-Hakata Bay and the inside of harbor, and d) area with the mud of a plenty of organic matter content in East-Hakata Bay. 5) The water area where red tides occur frequently coincides with the above c) and d), where a plenty of organic matter content is in mud.福岡湾は湾口部,今津湾および博多湾の3つの水域に分けることが出来る.1970年2月・5月・11月の底泥試料が福岡湾主として博多湾から採取された. Pigments量,強熱減量(%)およびC/N値が測定され,これらの結果から有機物分布を推定し赤潮が頻発する海域の泥の特性について論議した. 1) 底泥中に含まれる色素の約90～100%がPheopigmentsで各月のPigments量の分布はこの水域の海流の流れと関連していた. 2) 800℃での強熱減量(%)は500℃でのものより60～120%程大きい値を示した.強熱減量(%)の分布はPigments量の分布と一致していた. 3) C/N値の分布もまたPigments量分布に似ていた. 4) 強熱減量(%)とC/N値の関係から導かれた底泥の特性にもとついて,福岡湾を4つの水域に分けることが出来る.すなわちa)今津湾および航路筋,b)西部博多湾,c)東部博多湾と港内,d)東部博多湾内で多くの有機物を含む泥をもつ水域. 5) 赤潮が頻発する水域は多量の有機物を含む泥をもつ上記c)とd)に相当する