Arroyo Seco Insect Survey -Evaluating the Ecological Restoration. Bonita Thibault & Jasmin Gonzalez

Abstract

We collected samples of aquatic insects living in the Arroyo Seco portion of the L.A. River. Samples collected in the soft-bottom, less disturbed part of the river were compared to those in a restored site alongside a concrete channel. Biodiversity, total individuals and species richness were compared in an attempt to evaluate the restoration. Although biodiversity (Shannon Weiner Diversity Index) was not statistically different between the two sites, the Restored site had a higher diversity index than the Natural site. This could indicate that the Restored site provides an equally/more suitable habitat for these insect populations. The majority of individuals found in the Natural site were concentrated in only a few of the total species found in that site indicating that it promotes the success of only a few species. Most of these individuals belong to Dipteran families known to be pollution tolerant. Perhaps the Restored site is a healthier habitat. The average rock size in the Restored site was statistically greater than that of the Natural site.The insect density per rock in the Restored site was statistically lower than that of the Natural site. Despite no positive correlation between rock size and insect density, trends may indicate that insects prefer smaller rocks or that rock size has no effect on insect diversity. Further analysis of all data collected, year-round sampling and a more pristine "Natural site" may allow for a more conclusive evaluation of the Restored site.