Background.

In 2012, a biologic water quality study was conducted in the central part of Río Puyo, in Pastaza Province. The river is characterized for an increasing environmental degradation due to a rise in population with a simultaneous housing development increase.

Goals.

To assess Rio Puyo water quality with macroinvertebrate monitoring and chemical parameters.

Methods.

The macroinvertebrates were collected at four different dates, and two biotic indexes, Biological Monitoring Working Party for Costa Rica (BMWP-CR) and Biological Family Index for El Salvador (IBF-SV), were determined for each site. The study was complemented with pH and dissolved oxygen sampling to determine their correlation with the biotic indices.

Results.

There were 14 orders, 40 families and 2 808 individuals identified, most of the especimens belong to Leptohyphidae (23.3%) and Hydropsychidae (18.7%) families. The indexes showed that the water quality in the river drops significantly between points 1 (Fátima) and 3 (La Isla), showing some increase at point 4 (Unión Base). A 5% significance correlation were established between dissolved oxygen and BMWP-CR index (r=0.915), and 1% significance correlation between BMWP-CR an IBF-SV index (-0.947).

Conclusions.

all indexes show a significant drop of quality at the urban areas, one of them (IBF-SV) shows some recovery when the river leaves the city.