Water quality index including periphyton chlorophyll-a in forested urban watersheds from Tierra del Fuego (Argentina)

MARÍA GRANITTO; SOLEDAD DIODATO; PATRICIA RODRIGUEZ

ECOLOGICAL INDICATORS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2021 vol. 126 p. 107614 - 107614

1470-160X

The city of Ushuaia, Argentina, has experienced a rapid and unorganized populationgrowth with possible consequences on the dynamics and functioning of urban loticecosystems. Urban expansion was not largely accompanied by the development ofinfrastructure for the provision of services such as drinking water and sewers to all thepopulation. Currently, only 65% of the population is connected to the main sewagesystem (pre-treatment) and the city does not have a secondary wastewater treatmentplant yet. We evaluated the impact of wastewater discharges and non-pointcontamination on the water quality of the three main water courses that cross the cityof Ushuaia: Pipo river (PR), Buena Esperanza stream (BES) and Arroyo Grande river(AGR). We sampled four sites per watershed from spring to autumn in two consecutiveyears (2018 and 2019): S1 (not urbanized at the upper section), S2 (transitional zone),S3 (urbanized at the middle-low section), and S4 (urbanized, close to the outlet). Wedeveloped the Fuegian Water Quality Index (F_WQI) as a tool for environmentalmonitoring in forest streams which includes several indicators of organic inputs(dissolved oxygen, nitrogen-ammonium, total phosphorus, fecal coliform bacteria) andperiphyton chlorophyll-a (Peri Chl-a). The variables were ranked and weighed, and theindex was constructed using a mathematical formula. Urbanization negatively impactedthe water quality of these ecosystems; the F_WQI showed ?very bad? and ?bad? waterquality categories at S4 in BES and AGR, both sites impacted by wastewaterdischarges and large percentage of urbanized area. Likewise, in the PR watershed,with less urbanization and sewage discharges, the F_WQI indicated ?very good? waterquality. The F_WQI summarizes the water quality of forested watersheds in a simplenumerical scale, resulting in a useful tool for monitoring studies in temperate rivers andstreams. We encourage the inclusion of Peri Chl-a in water quality indices, due to itsubiquity in these ecosystems and the fact that it increased the sensitivity of the index.