A Three Year Assessment of the Influence of Physical Habitat, Pyrethroids and Metals on Benthic Communities in Two Urban Calfornia Streams

Abstract

This three year study was designed to characterize benthic communities (macroinvertebrates) and physical habitat annually in two urban stream areas (Arcade Creek and Salinas streams) in California. Concurrent water quality evaluations, physical sediment parameters, pyrethroids, and bulk metals [including simultaneously extracted metals (SEM) and acid volatile sulfides (AVS) ratios] were also measured in both study areas. The relationship of various benthic metrics to physical habitat metrics, pyrethroids, and metals was evaluated for the the three year data set (2009 -2011) using univariate analysis, stepwise multiple regression analysis and canonical correlation analysis. Habitat conditions were determined to be poor in Arcade Creek and extremely poor in the Salinas streams. Tolerant benthic taxa were dominant in both study areas but degraded communities more apparent in Salinas streams. Canonical correlation analysis of the three year data set for Arcade Creek indicated that, while benthic community diversity was inversely related to toxicants (metals and pyrethroids) in the sediments, community composition appeared to be more closely related to physical habitat quality. The statistical analyses conducted on the three year data set from Salinas streams detected fewer and weaker relationships between benthic metrics and environmental variables than did the analyses of data from Arcade Creek, likely due to the greater degree of overall environmental degradation of the Salinas streams. However, habitat (particularly sediment deposition) appeared to be the most significant stressor. In summary the tthree year data sets for both streams showed more significant relationships with benthic metrics and habitat metrics than with pyrethroid or metals.