Performance of two Patagonian molluscs as trace metal biomonitors: The overlap bioaccumulation index (OBI) as an integrative tool for the management of marine ecosystems

Abstract

In this study, we have investigated Cd, Cr, Cu, Ni, Pb and Zn in the biomonitors Mytilus chilensis and Nacella (P)magellanica sampled along seven selected sampling sites along 170 km of the coastal area of the Beagle Channel(Tierra del Fuego, Argentina) in four sampling campaigns: 2005, 2007, 2011 and 2012. The control charts werebuilt by applying Johnson?s probabilistic method for the first time in this marine area. We determined the metalconcentration overlap ranges in the selected biomonitors (as well as medians and distribution), and the overlapbioaccumulation index (OBI) with respect to the lowest (OBI-L1) and the highest (OBI-L) extreme values of theoverlap metal concentration ranges. The OBI can be used as an integrative tool in the management of prevailingunpolluted/polluted marine coastal ecosystems. It consents to identify the most suitable organisms for managingseveral environmental conditions where an ecosystem quality control is needed. The OBI-L1 index can be employedas a preventive signal of alarm when the contamination process is in its early stages. For Cd, Ni, Cu andCr, Nacella showed high OBI-L values that suggest its use as a biomonitor for mainly polluted marine ecosystems,in particular for Cd. Mytilus showed high Cd values for the OBI-L1 which means that this species is highlysensitive to a very low variation of the Cd levels in seawater. The OBI index enhances the observer?s informationvariety about the performance of the molluscs as metal biomonitors in marine ecosystems. Eventually, here wepropose to conceptualize the wide set of biomonitoring knowledge endowment as an open and evolutionaryendowment of information variety supporting the environmental management.