Sediment Contaminants and Biological Effects in Southern California: Use of a Multivariate Statistical Approach to Assess Biological Impact

Abstract

Abstract-This study attempts to predict biological toxicity and benthic community impact in sediments collected from two southern California sites. Contaminant concentrations and grain size were evaluated as predictors using a two-step multivariate approach. The first step used principal component analysis (PCA) to describe contamination type and magnitude present at each site. Four dominant PC vectors, explaining 88% of the total variance, each corresponded to a unique physical and/or chemical signature. The four PC vectors, in decreasing order of importance, were: (1) high molecular weight polynuclear aromatic hydrocarbons (PAH), most likely from combusted or weathered petroleum; (2) low molecular weight alkylated PAH, primarily from weathered fuel product; (3) low molecular weight nonalkylated PAH, indicating a fresh petroleum-related origin; and (4) fine-grained sediments and metals. The second step used stepwise regression analysis to predict individual biological effects (dependent) variables using the four PC vectors as independent variables. Results showed that sediment grain size alone was the best predictor of amphipod mortality. Contaminant vectors showed discrete depositional areas independent of grain size. Neither contaminant concentrations nor PCA vectors were good predictors of biological effects, most likely due to the low concentrations in sediments.

Potential effects of storm-water run-off on assemblages of mobile invertebrates

“…Overall, as in some previous studies (Maxon et al 1997, Nipper et al 1998, Roberts et al 2007), we did not find evidence to support the model that stormwater run-off has strong, clear negative effects on invertebrate assemblages as suggested by laboratory tests (Skinner et al 1999, Carr et al 2000. Our mensurative sampling using AUHs revealed a pattern of difference in assemblages between locations receiving and those not receiving storm-water run-off.…”

“…This confirms that assemblages developing on AUHs respond to local environmental conditions and, thus, can be useful tools for detecting effects of disturbances in the field (Edgar 1991b, Edgar & Klumpp 2003, Gobin & Warwick 2006. The results obtained in this and in previous field studies (Maxon et al 1997, Nipper et al 1998, Morrisey et al 2003, Roberts et al 2007) contrast with the findings of laboratory and mesocosm studies, which suggest strong toxic effects of run-off on several species of marine and fresh-water invertebrates (Hatch & Burton 1999, Skinner et al 1999, Carr et al 2000, Grapentine et al 2008. Laboratory tests are not always good predictors of the ecological effects of a disturbance (e.g.…”

“…To date, the ecological effects of storm-water run-off in natural systems remain uncertain. Although negative effects of run-off have been found on invertebrate assemblages in fresh-water systems (Pedersen & Perkins 1986, Graves et al 1998, only weak biological effects have been observed in marine and estuarine systems (Maxon et al 1997, Nipper et al 1998, Morrisey et al 2003. Moreover, our current fieldbased knowledge is limited not only because few field studies have been done, particularly in marine systems, but, more importantly, because almost all of these studies have only involved mensurative tests (sensu Hurlbert 1984).…”

“…storm-water run-off), particularly when they suffer from limited spatial or temporal replication (Underwood 1989, Mayer-Pinto et al 2010. Several of these studies also tried to establish a quantitative correlation between observed differences in attributes of assemblages and concentration of contaminants from storm-water run-off (Maxon et al 1997, Nipper et al 1998, Morrisey et al 2003. This correlation must exist if the run-off causes the differences in assemblages, but the existence of the correlation does not demonstrate that contamination by run-off causes the patterns of differences.…”

Contribution of Trace Metals in Structuring in Situ Macroinvertebrate Community Composition Along a Salinity Gradient

“…Total metal concentrations are used in most sediment risk assessment procedures to evaluate the effects of trace metals on, e.g., macroinvertebrates [1,15,16]. However, it is well accepted that it is not total but rather bioavailable concentrations that cause the effects on the biota [17][18][19][20] and thus on the community.…”