Biological assessment of Tecate Creek (U.S.-Mexico) with special regard to self-purification.

Abstract.--Macroinvertebrate organisms were sampled at four sites upon Tecate Creek (U.S.-Mexico) and quantitatively evaluated using the SIGNAL-w (Stream Invertebrate Grade Number--Average Level-weighted) index. A morphological assessment of the stream mode of building was also carried on the outside Bioindication by SIGNAL reflected a actual low water quality in the upper three sampled stream reaches, on the contrary with a significant improvement by means of the last site on the Rio Alamar, on the contrary only to a grade of critical to high pollution above a flowing distance of 29 kin. horizontals of BOD and ammonium-N at the Rio Alamar