I'd like to know more about indices based on chlorophyll content of water.
The implementation of the European Water Framework Directive resulted in the formulation of many phytoplankton based indexes, aimed at classifiying the ecological status of water bodies. These indexes are usually based on three metrics: chlorophyll, phytoplankton biomass and taxonomic composition. These are combined to obtain a single value, used to classify the ecological quality, according to a five classes scale, representing the degree of deviation from a pristine, undisturbed condition(from top to bottom: high, good, moderate, poor and bad). The boundaries values between two classes is strictly established for each metric and can be different according to water body typology. I cannot go into the details of each index: you can scroll the list of my publications here in Researchgate, where you can find references for a more detailed description of the phytoplankton indexes developed across EU. Please, ask me if you need further explanations.
the TRIX index (Vollenweider et al., 1998) is increasingly applied, especially in coastal lagoons. This is a multimetric index based on various parameters, productivity parameters (chlorophyll and dissolved oxygen) and nutritional factors (SRP or TP and DIN). Several authors show the application of this index and the index of Carlson in different lakes. My doctoral thesis, (you can find it on line if you write roderic.uv.es) show a comparison of results of the application of Carlson index and TRIX index in several mediterranean shallow lakes.
Thanks Giuseppe and Carmen.
I wonder whether taxonomic composition based indices can be used for comparative studies, as species composition can vary even in water bodies within same geographic area. In contrary, indices based on physico-chemical para have wider applicability in comparisons.
Hi Asanka, the rationale behind the use of biotic indexes is exactly what you pointed out, namely the comparison of different biotic communities. Of course, the comparison should be done among lakes with similar morphometric and morphologic features, located in the same geographic ecoregion. This is what the indexes developed in Europe allow to do, because their class boundaries are calibrated according to different lake typologies. Similar lakes host similar phytoplankton communities: the differences you find can be due, for instance, to a different degree of P load, if the biotic index was set up to respond to trophic gradient.
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