Regarding to the utility of macrophytes as biological indicators, less
data are available, comparing with those found about macroinvertebrates
or diatoms. Lainé et al. (2014) observed that taxonomic metrics
based on fish, macrophytes and benthic macroinvertebrates showed
similar responses (a strong decrease in species richness, diversity and
equitability) to toxic pollution, including metals and some nutrients.
Gonzalo and Camargo (2013) compared the impact of an industrial
effluent on macroinvertebrates and marophytes communities. In this
study, they concluded that the community of submersed macrophytes
exhibited slighter responses and lower discriminatory power than the
community of benthic macroinvertebrates, thus indicating that metrics
and indices based on macroinvertebrates may be more suitable for the
biological monitoring of water pollution and habitat degradation in
rivers receiving industrial effluents. The low relationship between
IVAM index and metal pollution may be due to the fact that most of
the macrophyte indices has been designed according to the tolerance
to water parameters such as nitrogen, phosphorous or gross organic
pollution, instead of other micropollutants. Specifically, IVAM index
has been developed according to the levels of phosphates and ammonium
of river water which have been considered the most appropriated parameters
to evaluate water eutrophication (Moreno et al., 2008).Moreover,
according to Demars et al. (2012b) more than 90% of the variability in
macrophytes indices has been attributed to factors others than human
pressure, such as hydromorphology, the characteristics of the riparian
forest or the presence of dead wood, river metabolism or the population
of fish.