A new ecotoxicity tolerance index of macrobenthos associated with Zoanthus sansibaricus in the littoral zone of Hormuz Island, Persian Gulf, Iran

A general study with the objective to classify ecotoxicity status of macrobenthose associated with dominant toxic zoanthids in Hormuz Island is presented. Hence, a novel model based on hard bottom macrobenthos and the related substrate composition was suggested to be used for testing the accumulated palytoxin (PTX) in macrobenthose exposed to Zoanthus sansibaricus. Direct and rapid assessment index (Dara Index) of accumulated PTX in macrobenthos were re-evaluated for use in this classification. The new proposed ecotoxicity tolerance index (ETI) was tested and calculated based on the data of Dara Index. ETI was compared and evaluated against Dara Index for use in this classification. The macrobenthos groups of species included three categories, namely, sessile, sluggish and mobile species. The distribution of these three macrobenthose groups were grouped according to their presence or absence to associate with zoanthids and were weighted proportionately to obtain a formula rendering a six step numerical scale of ecotoxicity status classification. Its advantage against the former Dara Index lies in the fact that it reduces the clustering number of the sampling sites involved which makes it simpler and easier in its use. The usage of ETI as a classification tool of ecotoxicity status indicates that tolerance of marine animals to the PTX may enable it to enter food chains and to be followed by potential exposure to humans. Hence, the advantages of ETI include high discriminative power and simplicity in its use which make it a robust, simple and effective tool for application in the Persian Gulf.