Publications: Research reports and publications

Benthic dinoflagellate toxins in two warm-temperate estruaries; Ranguanu and Parengarenga Harbours, Northland, New Zealand

1 January, 2011
CITATION

MacKenzie L, Selwood A, McNabb P, Rhodes L 2011. Benthic dinoflagellate toxins in two warm-temperate estruaries; Ranguanu and Parengarenga Harbours, Northland, New Zealand. Harmful Algae 10(6): 559-566.

ABSTRACT

The analysis of a variety of environmental samples and the installation of passive solid phase adsorption devices (SPATT) in two warm-temperate estuaries (Rangaunu and Parengarenga Harbours), during consecutive summers (2009 and 2010), revealed the pervasive influence of bioactive polyether compounds secreted by benthic dinoflagellates within the mangrove and sea-grass habitats. Pinnatoxin (PnTx) analogues PnTx-E and PnTx-F and okadaic acid (OA) and its esters were the most abundant, though traces of other polyether compounds (dinophysistoxins, pectenotoxin, spirolides), were also detected. In sediments, algal mats and micro-algal films, the parent compound PnTx-F was the predominate analogue. In bivalves and gastropods PnTx-E and PnTx-F were either present in equivalent amounts or there was a predominance of the former, indicative of in vivo metabolism. Esterified OA was the predominant form of this toxin in the deposit feeding sea hare Bursatella leachii, however OA-toxins were only about 14% as abundant as the combined PnTx analogues in this animal. Conversely levels of PnTxs accumulated within the SPATT bags were only 50% of total-OA, about 10% of which was in the form of OA-esters. Neither OA nor OA-esters were observed in the oyster Crassotrea gigas. The levels of total-PnTxs in C. gigas were about 8% of that observed in B. leachii (200 and 2580 mu g/kg respectively). Although there was abundant OA in this environment, cultured oysters did not incorporate this toxin presumably because they were not exposed to Prorocentrum lima cells in the water column or were unable to digest these cells. The low levels of pinnatoxins sequestered by oysters in these estuaries, despite persistent and very abundant populations of the causative dinoflagellate, is probably also due to the general inaccessibility of these cells to the shellfish and therefore there appears to be a low risk to human consumers.

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