Preliminary Study On The Effects Of "Brown Tide" In Qinhuangdao On Marine Organisms

The phytoplankton groups of the nano-sized and pico-sized phytoplankton samplecollected from the “brown tide” blooming sea area in Qinhuangdao on July2nd,2013(peak stage of “brown tide” bloom) and July,22nd,2013(decline stage) wereanalyzed. The effects of the “brown tide” sample from Qinhuangdao and three strainsof American “brown tide” algae on Argopecten irradians, Neomysis awatschensis,Artemia salina, Brachionus plicatilis, Calanus sinicus were studied by fieldexperiments and laboratory experiments in order to find out the reason why scallopstopped growing and the effects feature of “brown tide” in Qinhuangdao. Results ofthe study are as follows.“Brown tide” algae played a predominant role, constituting72.5%of the totalnano-sized and pico-sized phytoplankton biomass at the peak of “brown tide” bloom;while at the decline stage “brown tide” algae merely constituted2.6%of the totalbiomass.No mortality of marine animals tested was observed when exposed to “brown tide”seawater, except that survival of A. salina decreased to77%during48h exposure.However, the feeding of the bay scallop and zooplankton were significantly reducedwhen exposed to “brown tide” seawater. The clearance rate of A. irradians onpelagophytes was reduced when exposed to “brown tide” seawater when the densityof “brown tide” algae was as low as4.0×103cells/mL; clearance rate of A. irradianson other algae in “brown tide” seawater was reduced when the density of “brown tide”algae reached8×105cells/mL. The results indicate that “brown tide” algae appears tobe a poor food, and also inhibit the ingestion of bay scallop on other algae in “browntide” seawater. The ingestion of A. salina and rotifer in8hours were inhibited inmixed diets, reduced from5.5±0.4ng/ind to2.4±0.4ng/ind,1.5±0.2ng/ind to0.9±0.1ng/ind, respectively, indicating that “brown tide” in Qinhuangdao may also haveadverse effects on zooplankton.Laboratory experiments showed that feeding of A. irradians on CCMP1984,CCMP1850was reduced and that on other algae was also inhibited when the density of the two algae reached1.0×105cells/mL. A. irradians prefer Chlorella sp. to CCMP1984and CCMP1850in mixed diets, indicating that the adverse effects of “browntide” algae is due to toxin rather than small algae, which is likely to account for thereduced feeding of scallop when exposed to “brown tide” seawater. The effect ofCCMP1507on zooplankton is similar to that of CCMP1984and CCMP1850on A.irradians. The effects of different fractions from CCMP1507on the A. salina androtifer showed that the toxicity was mainly contributed by the algae cells.Results of field experiments combined with laboratory experiments showed that,when exposed to coastal waters where “brown tide” blooms for a long time, thefeeding of bay scallop can be inhibited significantly, that is probably the reason whybay scallop stopped growing in Qinhuangdao. Additionally,“brown tide” inQinhuangdao may also have adverse effects on other marine animals such aszooplankton. The adverse effects of “brown tide” in Qinhuangdao onshellfish aquaculture and the marine ecosystem deserves keen attention.