2024-02-23 18:31:17
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A group of Conicet researchers at the Esquel de Montañay Estepa Patagonian Research Center (Ciemep) studied the impact of residual effluent discharges on fish communities in five streams in Patagonia for an entire year. The work was published in the journal Science of the Total Environment.
The study focused on streams Quemquemtreu (The Bag), Mosquito (Cholila), Mines (Epuyén), Esquel (city of Esquel) and Percy (Trevelin). It was hypothesized that Wastewater Treatment Plants could have an effect on the fish community and the results revealed a decrease in habitat quality in all sectors downstream of the discharge entering the rivers (the impact zone).
According to the report, the exposure of fish communities to pollutants from wastewater puts their survival at risk. In turn, native fish are more affected than introduced ones.
“We live in the city of Esquel where an urban stream runs through us. And we have a sewage waste plant that is collapsed. We thought this must have some effect on the river’s biota. We decided to evaluate the abundance and distribution of fish before and after the plant†explained the doctor in Biology Cecilia Di Prinzio, associate researcher at Conicet.
A “white” stream
The researchers took as a parameter a “witness†stream that does not have the problems of plants.
“We decided not to limit the outlets to the Esquel stream but to extend them to all the nearby streams in the area that would have a sewage treatment plant. We did seasonal outings in summer, fall, winter and spring to evaluate changes in seasonal cycles,†Di Prinzio described.
The researchers did fish catches To know which species were present upstream and downstream of the plant, they measured the water temperature, current speed, PH, and conductivity. All this data allowed us to have estimates of the quality of the water. But at the same time, water samples were taken in order to process them in the laboratory.
“We compared the results and detected that there were high levels of phosphorus, nitrogen and ammonium downstream of the plants and not so much in upstream,” he said.
They detected that catfish species -a native species- were upstream well away from the plants. The trout, however, They could be in the area close to the plants and downstream. “The conclusion is that there are more tolerant, more plastic species: trout have a larger body size and greater mobility, and they can go close to the plant to eat (because there are more algae, more invertebrates as there is more nitrogen and phosphorus) and return to more pristine places. Catfish that have little mobility are in places where there is not so much pollution,†Di Prinzio specified.
He said that each stream has its particularity. The Esquel stream, for example, is an extreme case since although Around 2005 there were fish, after the installation of the plant, no specimens were found. The fish disappeared. “They are moving. It is a small stream that, as it has little flow, there is no dilution of the sewer effluents. By having more water, the Quemquemtreu dilutes this pollution faster,” he stated.
The researcher considered the existence of waste liquid plants to be extremely positive, although she stressed that the drawback is the population growth that exceeds the projection of the plants. “The plants work well, but the population is so large that they cannot process everything. There is the collapse. The systems should be updated with greater frequency and timeframe,†she indicated.
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