BENTHIC MACROINVERTEBRATES AS INDICATORS OF WATER QUALITY IN STREAMS OF COSTA RICA: USING AN ADAPTATION OF THE BMWP SCORE

Costa Rica is a tropical country that has adopted biological monitoring using macroinvertebrates and has adapted the BMWP score for its water bodies, where the new score is named BMWP-CR. In an experimental survey to assess the application of the BMWP-CR score, we considered seven study sites with a gradient of anthropogenic activities along the Dos Novillos river. The Shannon-Wiener Diversity and Pielou Evenness indexes were computed. The first study site was considered as the reference site. Four taxonomic groups were detected: Annelida, Platyhelminthes, Mollusca and Arthropoda. The last group was the most abundant and diverse. The Shannon-Wiener index ranged between 1.14 in a study site close to a banana processing facility, to 3.49 in a study site near to the confluence of the Dos Novillos River with the Parismina river. In such study sites, the Pielou Evenness index values varied from 0.57 to 0.83, respectively. The BMWP-CR scores ranged from 24 in the study site near the banana processing facility, to 116, in a downstream study site, reaching values higher than the reference site selected upstream in the Dos Novillos river far away from anthropogenic influence. Insects were the most diverse and abundant group. The correlation between the Shannon-Wiener Diversity index and the BMWP-CR scores presented a high significance value (R 2 = 0.927). Therefore, we suggest that the Shannon-Wiener index can be used alongside the BMWP-CR scores. The BMWP-CR method is sensitive enough for detecting changes in water quality reflecting differences in land uses along the studied river. RESUMEN: Macoinvertebrados taxonómicos: Anélidos, Platelmintos, Moluscos y Artrópodos. Este último fue el más abundante y diverso. El í​n​