INSTITUTO DE LIMNOLOGIA "DR. RAUL A. RINGUELET"
Unidad Ejecutora - UE
Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors
COCHERO J; LICURSI M.; GOMEZ N,
Año: 2015 vol. 51 p. 15 - 15
tBenthic diatoms are often used for assessing environmental conditions, such as water quality and habitatconditions in stream and river systems. Although laboratory experiments have shown that each diatomspecies have different levels of tolerance to different stressors, few studies have been conducted in labora-tory settings that analyze the responses of the diatom assemblage to the effects of multiple simultaneousvariables. The aim of this study was to evaluate some structural responses (such as species compositionand diversity) of the diatom assemblage on a short time scale to the effects of the simultaneous increase infour variables that are directly linked to the environmental changes affecting the Pampean streams: tur-bidity, nutrients (phosphorous and nitrogen), water velocity and temperature. To this end we conducted afive-week laboratory experiment using artificial channels where we simulated two environmental con-ditions (LOW and HIGH) employing epipelic biofilm from a mesotrophic stream. The results obtainedin the experiment show that the structure of the diatom assemblage in the epipelic biofilm is affectedby the simultaneous modification of temperature, water velocity, nutrient concentration and turbidity.These modifications in the assemblage included moderate decreases in diversity, small decreases in theproportion of species sensitive to eutrophication and saprobity, moderate increases in the IDP (PampeanDiatom Index) values and moderate changes in the percentages of the stalked growth-forms. The relativeabundance of species such as Luticola mutica, Navicula cryptocephala and Navicula lanceolata were neg-atively affected by both treatments; other species such as Planothidium lanceolatum, Caloneis bacillum,Encyonema minutum, Humidophila contenta, Luticola kotschyi, Nitzschia amphibia, Navicula veneta, Pinnu-laria subcapitata var. subcapitata were positively affected by the HIGH treatment; and Nitzschia fonticolawas positively affected by both treatments. The results suggest that, in the very short term of the bioas-say conducted, the diatom assemblage can modify its structure to respond in a sensitive manner to theabrupt changes in multiple physical?chemical variables.