Stream macroinvertebrate communities of the Republic of Palau and their use in watershed biomonitoring

Many archipelagoes of Pacific Oceania are undergoing rapid commercial development, especially island nations dependent on tourism for economic stability. The Republic of Palau is one such nation where coral reef and mangrove habitats are threatened by increasing sedimentation as a result of current and future prolific development on the island of Babeldaob, the sole source of perennial running surface waters in the nation. In 2003 we began stream macroinvertebrate collections with the objective of developing a watershed biomonitoring program for Palau. Our approach was to develop a biomonitoring program that did not require the taxonomic expertise (i.e., genus) or extensive field and laboratory commitments of those often used in mainland USA stream biomonitoring programs, but one that could be reviewed and amended by independent experts. Since that time, we have sampled stream macroinvertebrate communities regularly through August 2011. Since 2003 Babeldaob Island stream bedrock outcrop macroinvertebrate communities were dominated by neritid gastropods, atyid shrimps and lotic Lepidoptera, with minor representation by other insect taxa from pool and bank habitats. Changes in these communities in relation to the construction of a large road cirucum-island highway suggest that a biomonitoring is an ideal approach for monitoring watershed impact. Logistical constraints and safety considerations (e.g. crocodiles) provide additional rationale for focusing on bedrock outcrop communities for such a biomonitoring program that can be economically and practically executed for this island nation. The results and recommendations presented here provide the basis for a sustainable watershed biomonitoring program for the Republic of Palau.