The Influence of Physical Habitat, Pyrethroids, and Metals on Benthic Community Condition in an Urban and Residential Stream in California

ABSTRACT

This study was designed to characterize benthic communities and physical habitat in both an urban (Kirker Creek) and residential (Pleasant Grove Creek) stream in California in late spring of 2006 and 2007. Concurrent water quality evaluations, physical sediment parameters, pyrethroids, bulk metals, and SEM/AVS ratios were also measured during both years of this study. The relationship of various benthic metrics to physical habitat metrics, pyrethroids, and metals was evaluated for each stream using stepwise multiple linear regressions with both years combined for each stream, as well as both years and both streams combined, to increase the statistical power for determining significant relationships. Physical habitat was determined to be poor in each stream during both years of sampling. More than 100 benthic taxa were reported annually for both streams based on 2006 and 2007 sampling. A significant result from the stepwise regression analysis combining data for 2 years across both streams is that when habitat metrics and to a lesser degree metals are considered in the statistical models pyrethroids do not display any significant relationships to the benthic metrics. In summary, it is apparent from this analysis that the health of benthic communities in both streams is primarily affected by habitat metrics.

Key Words:

• bioassessments
• pyrethroids
• metals
• physical habitat
• urban and residential streams

ACKNOWLEDGMENTS

We thank the Pyrethroid Working Group for supporting this study. Dr. Elgin Perry is acknowledged for conducting parts of the statistical analysis. Jim Harrington, Angie Louis Montalvo, and Dan Pickard of California Department of Fish and Game are acknowledged for directing the identification of benthic species. Morse Laboratories in Sacramento, California, is acknowledged for the pyrethroid analysis. Applied Marine Sciences Inc. in League City, Texas is acknowledged for total organic carbon (TOC) and grain size analysis. CRG Marine Laboratory in Torrance, California, is acknowledged for bulk metals and SEM/AVS analysis.

Notes

*p < .05.

*p < .05.

*p < .05.

*Variables that remained significant after the principal components associated with pyrethriods and metals were forced into the stepwise regressions prior to the testing of the habitat variables (see text for details).

**Variables that remained significant after the principal components associated with habitat metrics were forced into the stepwise regressions prior to the testing of the toxicant variables (see text for details).

*Variables that remained significant after the principal components associated with pyrethroids and metals were forced into the stepwise regressions prior to the testing of the habitat variables (see text for details).

^ast *Variables that remained significant after the principal components associated with the habitat metrics were forced into the stepwise regressions prior to the testing of the toxicant variables (see text for details).