The effect of organic pollution on the macroinvertebrate fauna of Ecuadorian highland streams
Archiv für Hydrobiologie Volume 143 Number 2 (1998), p. 179 - 195
published: Oct 20, 1998
ArtNo. ESP141014302003, Price: 29.00 €
The effect of organic pollution on macroinvertebrate communities was studied in five small streams located at 2600 to 3100 meters above sea level in the Andes of Ecuador. Sampling of invertebrates and measurements of physico-chemical parameters were performed at the end of the rainy season and at the end of the dry season at upstream unpolluted sites and at adjacent downstream polluted sites. At all upstream sites, more taxa were collected in the dry season, while at the polluted downstream sites, more taxa were collected in the wet season. Also values of two biotic indices (BMWP and ASPT) tended to increase at the upstream sites and decrease at the downstream sites in the dry season. Thus, the effect of organic pollution was most pronounced during the dry season. In addition, both biotic indices were highly correlated to minimum oxygen saturation and phosphate concentration in the dry season, while correlations were much weaker in the wet season. Overall, the shift in faunal composition with organic pollution resembled that described from temperate streams at higher latitudes. However, the main shift in the tropical highland fauna occurred abruptly at about 80 % oxygen air saturation, but because of the low partial pressure of oxygen at an altitude of 3000 meters, this corresponds to no more than 56 % of the oxygen partial pressure of air saturated water at sea level. I propose that tropical highland streams are more sensitive to further lowering of oxygen levels through organic pollution than their temperate counterparts.