Assessing ecological impairments in Neotropical rivers of Mexico: calibration and validation of the Biomonitoring Working Party Index

Freshwater ecosystems are one of the most endangered and threatened ecosystems worldwide, particularly in developing countries, where population growth, industrialization, urbanization, and changes in land use are increasing. In Mexico, water ecosystems are severely impacted and an easy-to-use tool is needed for monitoring freshwater ecosystems. This study presents the development of a calibration and validation procedure for the Biological Monitoring Working Party Index using physical–chemical and biological data from Neotropical rivers in Mexico (Apatlaco and Chalma-Tembembe). Water quality and macroinvertebrates were monitored in four campaigns including the dry and rainy seasons (2012–2013). Calibration of the index was performed in the following steps: determination of a physicochemical quality index, identification of the abundance class for each family of macroinvertebrates, incorporation of abundances in the corresponding physicochemical quality index interval, and determination of bioindication values for each macroinvertebrate family. With the calibrated values, the index was assessed for each study site and period. The calibrated index was validated by a statistical test. Ranges for water quality categories were defined by three statistical procedures. The range of the Biological Monitoring Working Party Index was tested with study sites from adjacent sub-basins. The Chalma-Tembembe River in agricultural areas comprised the categories “Bad polluted” to “regular and moderately polluted,” whereas the largest portion of the Apatlaco River in urban zones comprised “Bad, very polluted” to “Bad, extremely polluted.” Thus, the calibrated index is a suitable biomonitoring tool, allowing the detection of zones that need urgent management and a recovery plan.