Patterns in sediment metal, polycyclic aromatic hydrocarbon (PAH), chlorinated pesticide, and polychlorinated biphenyl (PCB) concentrations at 290 sites within coastal, port, harbor, and marina areas of the Southern California Bight (SCB) were evaluated using cluster analysis and principal components analysis (PCA). Cluster analysis identified five primary site groups, with two large groups representing 96% of the total area of the SCB. One of these two groups contained many of the open coastal sites, characterized by relatively coarse-grained sediments (∼30% fines), low organic carbon, and low contaminant concentrations. The second large cluster group included a higher proportion of the embayment, marina, and harbor sites, with finer-grained sediments (∼70% fines) and proportionately higher mean concentrations of most metals and trace organics. Both site groups were considered representative of SCB background conditions with minimal alterations from contaminant inputs. The other three site groups exhibited elevated concentrations of one or more contaminants, but accounted for only 4% of the total area of the SCB. In particular, two small cluster groups consisted mainly of port, harbor, and marina sites with elevated mean concentrations of certain metals (e.g., Cu, Pb, Sb, and Zn), as well as elevated chlordane, PAH, and PCB concentrations for one of the two site clusters. The fifth cluster group consisted of Palos Verdes Shelf sites that were characterized by high sediment DDT, PCB, Cd, and Ba concentrations, and clearly different from other open coastal sites in the SCB. PCA identified four principal components that explained 67% of the variance in the data set. The first two components (PC1 and PC2) accounted for 52% of the total variance. PC1 was highly loaded with a suite of metals (Cu, Pb, Hg, Zn, Al, and Fe), with high scores primarily for industrialized port and harbor sites. PC2 had high loadings for DDTs, PCBs, Cd, and Cr with highest scores for sites on the Palos Verdes Shelf. PC3 and PC4 each accounted for less than 10% of the total variance, with high loadings for low- and high-molecular weight PAHs and for a subset of metals (Ba, Ni, and Se) and fines, respectively. Although contaminant sources were not analyzed for this study, PC1 and, to a lesser extent, PC3 likely reflected recent industrial inputs to ports, commercial shipping and boatyard operations, and small marina activities. In contrast, PC2, reflected historical, wastewater-derived inputs to the Palos Verdes Shelf. Distinct sediment contaminant patterns were not evident for other large and small wastewater or riverine discharges.

The lower San Gabriel River is an urban watershed located on the border of Los Angeles and Orange Counties. It has a diversity of potential pollutant sources including five water reclamation plants (WRPs) that discharge treated wastewaters and more than 100 storm drains that discharge largely untreated urban runoff to the river. The goal of this study was to assess the magnitude of toxicity to Ceriodaphnia dubia throughout the lower San Gabriel River watershed during wet and dry weather, identify the responsible toxicants, and compare the magnitude of toxicity over time to evaluate the effectiveness of previous watershed management actions. Wet weather runoff was sampled from sites located at the end of the four main reaches of the lower San Gabriel River; Walnut Creek, San Jose Creek, Coyote Creek, and San Gabriel River mainstem. None of the samples collected over two wet seasons exhibited acute or chronic toxicity. Dry weather samples were tested from 16 locations distributed throughout the lower watershed for up to 18 months. None of the dry weather samples from Walnut Creek, San Jose Creek, or the San Gabriel River mainstem exhibited acute or chronic toxicity. Acute and chronic toxicity was intermittently measured in the Coyote Creek tributary. Toxicity identification evaluations suggested nonpolar organic constituents, likely diazinon and perhaps surfactants, as possible toxicants. Toxicity observed in this study was significantly reduced compared to a similar study of the watershed 12 years previously, especially in the San Gabriel River mainstem. Much of the reduction in toxicity was associated with upgrades in WRP treatment. Little to no change in toxicity was observed in Coyote Creek upstream of the WRP discharge where little to no control of dry weather urban runoff had occurred.

The effectiveness of a pilot post-impingement fish return program was studied at Los Angeles Department of Water and Power's Scattergood Generating Station during six heat treatments from February 2005 to August 2006. Species-specific total percent survival was computed for all individuals impinged, with an overall survival of 0.4% across all species impinged during monitored heat treatments, ranging from 30.2% for Paralabrax clathratus to 0.0% for Seriphus politus. Species-specific critical thermal maxima was inferred from surveys of the abundances returned by San Onofre Nuclear Generating Station's highly effective and unique Fish Return System during heat treatments from 2000–2005. Abundant species such as queenfish exhibited low thermal thresholds (15–20°C), while spotfin croaker and barred sand bass became stressed at higher temperatures (25–30°C).

In the Warner Mountains of California, two sympatric species of chipmunk partition their habitat primarily through the mechanism of competitive exclusion by social dominance and aggressive interactions. Forests are optimal habitats for both Neotamias amoenus and N. minimus. In this study N. amoenus actively excludes N. minimus from the forest through successful aggressive interspecific interactions, leaving N. minimus to occupy primarily the arid sagebrush scrub. Neotamias amoenus was observed to be the more social species. Neotamias minimus appears to lack the level of social structure of N. amoenus and was not observed to win any aggressive encounters. Neotamias minimus avoids interaction with N. amoenus.