Geographical and Annual Variation in Lipophilic Shellfish Toxins from Oysters and Mussels along the South Coast of Korea

Abstract

To better understand critical aspects of diarrhetic shellfish poisoning (DSP) occurrence in a chief producing region of bivalves in Korea, the geographical and annual variation of DSP toxins and other lipophilic toxins in mussels (Mytilus galloprovincialis) and oysters (Crassostrea gigas) were investigated by liquid chromatography-tandem mass spectrometry in an area on the south coast of Korea from 2007 to 2009. The total lipophilic shellfish toxin (LST) levels in bivalves showed geographical and annual variations. LSTs were detected mostly in the hepatopancreas of mussels from Jinhae Bay throughout the entire year, except in November and December of 2007, but were almost undetectable in all samples during the entire year in 2009. The peak DSP toxin (okadaic acid plus dinophysistoxin 1) levels in the hepatopancreas of mussels from Jinhae Bay and the Tongyeong region were 945.3 and 37.6 ng/g, respectively. The DSP toxin content was about 10 times higher in mussels than in oysters collected from the same region. The major toxins in bivalves were okadaic acid and dinophysistoxin 1; however, pectenotoxin 2 or yessotoxin was occasionally detected as a major component. The results of a quantitative analysis of phytoplankton showed that Dinophysis acuminata was the most probable source of the LSTs, with the exception of yessotoxin. When the highest DSP toxin level was measured (945.3 ng/g in the hepatopancreas of mussels from Jinhae Bay), the toxin concentration in whole mussel tissue was calculated to be 114.0 ng/g. The calculated highest DSP toxin level in whole oyster tissue from both regions was 15.0 ng/g. The calculated maximum toxicities in whole mussel and oyster tissues were lower than the regulatory limit (160 to 200 ng/g) in Korea, the European Union, and the United States. Korean oysters (242 samples) and mussels (214 samples) were thus deemed safe for consumption. But because such variation was detected in a relatively small area of the coast, it is possible that at some locations or during a specific period LST levels could exceed the standard and a few consumers could be at risk of experiencing DSP.

First Detection and Seasonal Variation of Lipophilic Toxins Okadaic Acid, Dinophysistoxin-1, and Yessotoxin in Korean Gastropods

“…In previous studies, we detected only low concentrations of lipophilic toxins in bivalves such as oysters (Crassostrea gigas) and mussels (Mytilus galloprovincialis) from the southern coast of Korea, but we found significant seasonal variation with peaks of toxicity in spring and summer (13, 19). Thus, the coast of Korea (13,19), the lack of PTX2 detection in this study is an interesting result. PTX2 may be rapidly converted into one of its derivative acids in gastropods, as has been shown in bivalves (29,30).…”

“…The concentrations of lipophilic toxins in gastropod tissues were lower than the regulatory safety limits of the EU. In previous studies, Korean bivalves were also found to contain lipophilic toxins in concentrations below the regulatory limit (13,15,19). Korean gastropods can apparently be deemed safe for human consumption considering DSP toxin contents.…”

“…Carnivorous gastropods prey on bivalves, such as mussels, clams, scallops, and oysters; R. venosa has been reported to consume about one bivalve per day (or 1.2 g wet weight per day) (27). Accumulation of lipophilic toxins by filter feeding shellfish is a well-known phenomenon in many countries, including Korea (13,15,19), Japan (35), The Netherlands (11,12), Portugal (33), Canada (23), and New Zealand (29,30). These findings strongly suggest that consumption of carnivorous gastropods may cause DSP incidents in the areas where lipophilic toxins are prevalent in bivalves.…”

“…Our previous studies found Dinophysis spp. in seawater and low levels of lipophilic toxins in bivalves off the southern coast of Korea (13,15,19). Carnivorous gastropods that prey on lipophilic toxin-containing bivalves may become vectors of these disease-causing toxins.…”

Distribution of Heavy Metals in Muscles and Internal Organs of Korean Cephalopods and Crustaceans: Risk Assessment for Human Health

“…(15) also reported that K orea ranked 3rd (292,405 tons) and 14th (135,720 tons) in the world for the production o f cephalopods and crustaceans, respectively, in 2012. These products are exported mainly to the U nited States, China, Japan, and the E uropean U nion (EU) (27). the aquatic environm ent and increase the contam inant load for hum ans consum ing these organism s (10,32,38).…”