Aquatic Macroinvertebrates as Bioindicators of Water Quality: A Study of an Ecosystem Regulation Service in a Tropical River

In this study, aquatic macroinvertebrates were used as bioindicators to determine the ecological conditions of the Lapa River, located between the municipalities of Cayey and Salinas, Puerto Rico. The water quality of the river was evaluated through the calculation of the Puerto Rico Biological Monitoring Working Party (BMWP-PR), as well as its degree of contamination using the Puerto Rico Family Biotic Index (FBI-PR). Bimonthly sampling was conducted across four sampling sites for a period of 12 months. The sampling sites were positioned upstream and downstream within the nature reserve, and outside and downstream its borders. The BMWP-PR results showed that the site upstream-inside the nature reserve had good water quality, and the site downstream-inside the nature reserve had regular water quality, showing some areas with eutrophication. The water quality outside-downstream from the nature reserve was poor. The FBI-PR results showed that there was mild organic contamination inside the nature reserve, while there was substantial organic contamination in the site that was outside-downstream from the nature reserve. We concluded that the section of the river located within the nature reserve had better ecological conditions than the stretch of the river located outside-downstream of the nature reserve, because it is located within a protected area that has barely been impacted by human activity.