Occurrence, distribution, source, and influencing factors of lipophilic marine algal toxins in Laizhou Bay, Bohai Sea, China

The composition, distribution, origin, and influencing factors of lipophilic marine algal toxins (LMATs) in surface seawater and phytoplankton in Laizhou Bay, China, were comprehensively investigated for the first time. Okadaic acid (OA), pectenotoxin-2 (PTX2), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), and pectenotoxin-2 seco acid (PTX2 SA) were discovered in surface seawater, whereas PTX2, OA, 7-epi-PTX-2 SA, DTX1, PTX2 SA, PTX11, and DTX2 were found in phytoplankton in a decreasing concentration order. Sigma LMAT concentrations in seawater and phytoplankton were 1.08-35.66 ng/L (mean: 7.31 ng/L) and 0-3609.75 ng/L (mean: 191.38 ng/L), respectively. LMAT contents in seawater and phytoplankton exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner and outer bays. Dinophysis fortii, D. acuminata, D. rotundata, Procentrum lima, and P. minimum were identified as the potential origins of LMATs in Laizhou Bay. Moreover, increased nutrient level and decreased pH in seawater could increase LMAT content.