Nile-Trophic Diatom Index (TDI-Nile): a new constructed index for assessment eutrophication in River Nile basine in Egypt

In the present study, a new index (Nile-Trophic Diatom Index ,TDI-Nile) was constructed for the assessment of eutrophication in River Nile and its branches in Egypt depending on using the total phosphorus (TP) , total inorganic nitrogen (TIN) and diatoms.  Epilithic diatom samples wee collected from 40 locations during autumn-2013 and spring-2014. Over 224 diatom taxa were identified and 91 taxa (frequency ≥ 3) were sufficiently abundant to include in index development.
Multivariate data exploration revealed strong responses of the diatom assemblages to stressor variables, including total phosphorus (TP). Weighted average method was used to develop the TP and TIN indices. According to Nile-Trophic Diatom Index (TDI-Nile), most of the samples which classified in bad quality were belonging to Rosetta branch and Kema station.
Canonical correlation analysis revealed that the newly developed indices significantly well correlated (Canonical correlation = 0.79, p < 0.0001) with environmental variables which make them reliable indices of water quality and they can be suggested as the best indices for monitoring purposes in the River Nile.