The use of water chemistry and benthic diatom communities for qualification of a polluted tropical river in Costa Rica

Abstract

The water quality of several sections of a tropical river subjected to severe pollution was studied through physico-cbemical water analysis and benthic diatom assemblages. The methodology follows the concept of differential species groups and that of its modification for the groups of nutrient- differentiating species for rivers rich in both oxygen and inorganic nutrients. The trophic indication of the latter authors corresponded clearly with the results of chemical observations made in this study. The most abundant species found in this river were Navicula goeppertiana, Gomphonema parvulum, Gomphonema sp. aff. pumilum, Nitzschia palea, Nitzschia amphibia, Nitzschia clausii Nitzschia inconspicua, Navicula seminulum, Navicula sp. aff. cryptocephala, Navicula schroeterii var. escambia, Cymbella sinuata and Surirella sp. aff. roba. These species are known to be tolerant to organic pollution and eutrophication. Therefore we may conclude that diatoms are useful for biological monitoring of disturbed tropical rivers