Spatial variation of lipophilic marine algal toxins and its relationship with physicochemical parameters in spring in Laizhou Bay,China

Lipophilic marine algal toxins(LMATs)are produced by some toxigenic microalgae,which pose a serious threat to marine ecosystem and even human health.The occurrence and environmental control factors of LMATs in the surface seawater and phytoplankton in spring in Laizhou Bay in which Huanghe(Yellow)River estuary is included,in Shandong,East China were investigated.Okadaic acid(OA),pectenotoxin-2(PTX2),dinophysistoxin-1(DTX1),pectenotoxin-2 seco acid(PTX2 SA),DTX2,7-epi-PTX2 SA,PTX11,and 13-desmethyl spirolide C(SPX1)were detected from the surface seawater samples,and PTX2,7-epi-PTX2 SA,OA,DTX2,DTX1,PTX2 SA,and PTX11 were discovered in the phytoplankton samples showed a decreasing trend.The concentrations of∑LMATs in the seawater and phytoplankton ranged 2.03-74.38 ng/L on average of 13.72 ng/L and 0.98-479.27 pg/L on average of 50.20 pg/L,respectively.The joint influence of terrigenous input and internal circulation could promote the growth,toxin production,and toxin release of toxin-producing algae,leading to a higher content of LMATs in the bay nearby the Huanghe River estuary in both seawater and phytoplankton.The concentration of LMATs in spring was higher than that in summer,showing obvious seasonal variation.In addition,no significant correlation between most of the physiochemical parameters and LMAT contents in seawater was revealed by correlation analysis except for the positive correlation between DTX2 and chlorophyll a,OA and NH4-N.However,the increase of dissolved inorganic nitrogen content in seawater could enhance the production of OA,DTX1,and DTX2 in phytoplankton due probably to that the inorganic N input could benefit the growth and stimulate toxin production of toxin-producing algae.The result also proved that some PTX2 may be originated from Procentrum spp.and OA,DTXs and part of PTX2 may be originated from Dinophysis spp.