A key step of European Water Framework Directive (WFD) implementation is the ecological status classification and the achievement of good water statuses for all waters, by 2015. In transitional waters, the changing environmental niche induces responses in the macroinvertebrate guilds and macroinvertebrate responses induce uncertainty in the metrics. In this case, the sources of uncertainty in the ecological classification with benthic macroinvertebrates, is addressed by focusing on two major potential sources: spatial heterogeneity and temporal heterogeneity. A coherent study of the series of correlation between the physics and chemistry parameters is needed in order to succeed in reaching a complete picture. In this paper we present a bi-dimensional regression analysis model dependence of chemistry component by two independent environment variables--temperature and pH. The consistent experimental data set and the regression computation approach lead to a series of interesting outcomes.