Biotic indices for ecological status of transitional water ecosystems

Abstract

1 - The biological elements, proposed by the WFD as quality elements for the classification of ecological
\nstatus of the transitional waters are: composition, abundance and biomass of phytoplankton;
\ncomposition and abundance of other aquatic flora (i.e. macroalgae and angiosperms); composition
\nand abundance of benthic invertebrate fauna; composition and abundance of fish fauna.
\n2 - Although the directive proposed these biological elements, it doesn’t provide clear indication on the
\n“biocriteria” to achieve. WFD suggested that ecosystem health should be defined by comparison to
\nreference conditions.
\n3 - Recently, there has been a growing interest and need for sound and robust ecological indices to
\nevaluate transitional ecosystem status and condition, mainly under the scope of the Water Framework
\nDirective implementation.
\n4 - A good biotic index should reflect the biological integrity; respond to environmental stresses in
\nmonotonic way; be measurable with low error; be cost-effective; be not invasive (i.e. the measure
\nmethods do not significantly disturb or alter habitats and biota).
\n5 - Several indices have been developed for environmental quality assessment using macrobenthic
\nassemblages, ranging from the comparison of a single metric to complex multivariate analyses.
\nSome indices were developed for fish assemblages and for macrophytes, but only few indices were
\nproposed considering the phytoplankton.
\n6 - In this report, we shown and compare several biotic indices used for evaluating ecological status of
\ntransitional water ecosystems using the five biological quality elements.