Screening of nano- and pico-phytoplankton responsible for Diarrhetic Shellfish Poisoning

腹泻性贝类中毒不仅是公共卫生问题，也是双壳贝类养殖业的禁捕问题。目前，属于Dinophysis属的几种甲藻被认为是引起DSP的微生物。然而，也有一些情况下，在没有牙藻的情况下，双壳类的毒性增加，或者在牙藻开花期间，双壳类的毒性没有增加，例如尖叶杜鹃和福州杜鹃。因此，数字信号处理器的发生机制一直是个谜。最近的研究表明，Dinophysis spp.本研究从青森县木须湾采集水样，对小型浮游植物作为浮游植物的食物和DSP毒素的可能来源进行了筛选。采用消光稀释法分离出多种微米级和纳米级浮游植物。用酶联免疫吸附试验(EL ISA)检测这些菌株是否有毒。结果显示，163株细菌中有4株DSPs阳性，但其毒性尚需进一步的LC-MS鉴定。同时，用酶联免疫吸附试验(EL ISA)法检测了~lt；5μm的海水中的DSPs毒素。用ELISA法测定海水中小型浮游生物组分的毒性，结果与官方小白鼠测定扇贝的毒性相吻合。尖吻扇贝和福氏扇贝的发生与扇贝的毒性没有很好的相关性。结果表明，用ELISA法直接监测海水中浮游生物含量是预测近海养殖扇贝中DSP毒素污染的有效手段。

Diarrhetic shellfish poisoning (DSP) is not only the problem of public health but also of bivalve aquaculture due to the ban of harvest. Currently, several species of the dinoflagellates belonging to the genus Dinophysis are known to be causative organisms of DSP. However, there have been some cases in which the bivalave toxicity increased in the absence of Dinophysis, or in which the bivalve toxicity did not increase during blooms of Dinophysis such as D. acuminata and D. fortii. The mechanisms of DSP occurrences have been therefore enigma. Recent studies have indicated the mixotrophy of Dinophysis spp. The present study is a trial of screening of small-sized phytoplankton that are foods of Dinophysis and possible origin of DSP toxins.Water samples were collected from Mutsu Bay, Aomori Prefecture. Many strains of pico- and nano-phytoplankton were isolated by the extinction dilution method. These strain culures were examined whether toxic or not by Enzime Linked Immunosorbent Assay (ELISA) for DSP. As a result, four strains from 163 were DSP positive by ELISA, however, it is necessary to confirm their toxicity by using of LC-MS in the future.The cell numbers of Dinophysis spp. were counted, and simultaneously DSP toxins were assayed in seawater in size fraction of<5 μm by ELISA method. The results obtained by ELISA method for the toxicity of the fraction of small-sized plankton in seawater coincided with the toxicity of scallops by the official mouse assay. The occurrences of D. acuminata and D. fortii did not well correlated to the toxicity of scallops. It is suggested that the direct monitorings of plankton fraction in seawater by ELISA method is an effective tool to predict the DSP toxin contamination in scallops of aquaculture in the coastal areas.