Background.

Stream ecosystems reflect human impacts on the environment. An understanding of the threats affecting these ecosystems and the development of tools to assess them is key for the conservation and management of aquatic ecosystems. Puerto Rico is an oceanic island with dense human presence and strong pressures over freshwater resources that result in the degradation of water bodies. Aquatic macroinvertebrates respond to pollution and are good indicators of anthropogenic impacts on streams.

Goals.

To describe major threats to the ecological condition of streams in Puerto Rico and introduce two biomonitoring indices based on macroinvertebrates that allow for the assessment of stream condition on the island.

Methods.

We proposed a standardized methodology for the use of the Biological Monitoring Working Party (BMWP) and Family Biotic Index (FBI) modified for Puerto Rico.

Results.

Major threats to aquatic ecosystems in Puerto Rico are associated with urbanization, water extraction, and untreated water discharges. For the elaboration of the indices, a tolerance value was assigned to each of the 87 taxonomic groups reported for Puerto Rico. Based on stream sampling, impact scales were developed for the BMWP-PR and FBI-PR. In addition, a standardized methodology is proposed to avoid sampling biases.

Conclusions.

The conservation status of rivers in Puerto Rico is relatively good compared with other tropical regions. The indices proposed (BMWP-PR, FBI-PR) are the first developed for the island with the goal of evaluating the ecological condition of streams. The indices are proposed as a starting point, future efforts should focus on the development of additional tools.