Occurrence of okadaic acid in the feeding grounds of dugongs (Dugong dugon) and green turtles (Chelonia mydas) in Moreton Bay, Australia

1 2 Okadaic acid (OA) is a diarrhetic shellfish poison (DSP) produced by a number of marine organisms including the benthic dinoflagellate Prorocentrum lima, which are often found on seagrass. As seagrass forms the basis of the diet of dugong ( 3 4 Dugong dugon) and green turtle (Chelonia mydas), these herbivores may potentially be exposed to OA through ingestion of 5 P. lima found on the seagrass. In this study, the abundance of epiphytic 6 P. lima, on seagrass, and the concentration of OA produced by these epiphytic dinoflagellates was measured in Moreton Bay, Queensland, Australia. 7 8 Prorocentrum lima and OA were found on all four species of seagrass collected. OA was detected in epiphytic material collected from seagrass, with a maximum of 460 ng OA/kg(wwtSG) found on 9 10 Halophila spinulosa . From this information, the estimated maximum daily intake of OA by an adult dugong consuming 40 kg(wwtSG) /day was 18,400 ng/day, and an adult turtle consuming 2 kg(wwtSG) /day was 920 ng/day. Analysis by HPLC/MS/MS of 54 stranded dugongs and 19 stranded turtles did not yield OA above the detection limit of 10,000 ng/kg(animal tissue). OA was found on seagrass, however it was not detected in the tissue samples of dugongs and turtles. 11 12 13 14 15 16