The ecofunctional quality index (EQI): a new tool for assessing lagoonal ecosystem impairment

A multimetric index for the evaluation of environmental quality (the ecofunctional quality index, EQI) has been developed using biotic data from three Italian coastal lagoons. Sampling programs were conducted between 1998 and 2000, on a yearly basis, with seasonal frequency at diverse sites in each lagoon. The rationale of the index is that certain attributes, selected on the basis of established principles of benthic ecology, are fundamental for lagoon ecosystem function. The chosen attributes were primary productivity, expressed as phytoplankton, seaweed and seagrass biomasses; structure and productivity of the benthic community, expressed as numerical abundance, biomass density, number of species, and taxonomic diversity of macrozoobenthos; and finally, trophic complexity, expressed as macrozoobenthic functional diversity. The EQI is constituted by the sum of weights given to these eight attributes, each transformed onto a dimensionless 0–100 quality scale. In this way, the use of EQI can derive a series of values yielding a functional classification of sites within a lagoon or between different lagoons. The proposed index is a low cost, flexible and robust routine indicator of lagoon ecosystem impairment and could be of particular benefit to environmental managers and policymakers who require tools capable of expressing the degree of degradation or environmental quality of different lagoon habitats. The process of developing and the initial testing of EQI reported in this paper is intended as preliminary, and until validation of this index is accomplished by incorporating data from a wider range of lagoon environments, we caution the use of this index in anything other than an exploratory manner.