In the past decade, several large programs that monitor currents and transport patterns for periods from a few months to a few years were conducted by a consortium of university, federal, state, and municipal agencies in the central Southern California Bight, a heavily urbanized section of the coastal ocean off the west coast of the United States encompassing Santa Monica Bay, San Pedro Bay, and the Palos Verdes shelf. These programs were designed in part to determine how alongshelf and cross-shelf currents move sediments, pollutants, and suspended material through the region. Analysis of the data sets showed that the current patterns in this portion of the Bight have distinct changes in frequency and amplitude with location, in part because the topography of the shelf and upper slope varies rapidly over small spatial scales. However, because the mean, subtidal, and tidal-current patterns in any particular location were reasonably stable with time, one could determine a regional pattern for these current fields in the central Southern California Bight even though measurements at the various locations were obtained at different times. In particular, because the mean near-surface flows over the San Pedro and Palos Verdes shelves are divergent, near-surface waters from the upper slope tend to carry suspended material onto the shelf in the northwestern portion of San Pedro Bay. Water and suspended material are also carried off the shelf by the mean and subtidal flow fields in places where the orientation of the shelf break changes abruptly. The barotropic tidal currents in the central Southern California Bight flow primarily alongshore, but they have pronounced amplitude variations over relatively small changes in alongshelf location that are not totally predicted by numerical tidal models. Nonlinear internal tides and internal bores at tidal frequencies are oriented more across the shelf. They do not have a uniform transport direction, since they move fine sediment from the shelf to the slope in Santa Monica Bay, but carry suspended material from the mid-shelf to the beach in San Pedro Bay. It is clear that there are a large variety of processes that transport sediments and contaminants along and across the shelf in the central Southern California Bight. However, because these processes have a variety of frequencies and relatively small spatial scales, the dominant transport processes tend to be localized and have dissimilar characteristics even in adjacent regions of this small part of the coastal ocean.

No abstract available.

More than 30 million dollars are expended annually to assess environmental quality of the Southern California Bight, yet only 5% of the Bight area is surveyed on an ongoing basis. Because decision makers lacked the data to make regional assessments of ecosystem condition, multiple stakeholders collaborated to create a Southern California Bight Regional Monitoring Program. The third survey in this program was conducted in 2003. A primary goal of this regional monitoring program was to determine the extent and magnitude of sediment contamination in the Southern California Bight, and to compare these assessments among several different habitats. A stratified random design was selected to provide unbiased areal assessments of environmental condition; 359 surficial sediments were collected, representing 12 different habitats that extend from shallow embayments and estuaries to deep offshore basins. Each sample was analyzed for grain size, total organic carbon and nitrogen, 15 trace metals, and a suite of persistent organic constituents (total dichloro-diphenyl-trichloroethane [DDT], total polychlorinated biphenyl [PCB], and total polynuclear aromatic hydrocarbon [PAH]). The greatest accumulated mass of these constituents (76% on average; range 70% to 87%) was located at depths >200 m, which was proportional to its relatively large area (67% of entire Southern California Bight). The greatest sediment concentrations of trace metals, total PAH, and total PCB were observed in embayments (e.g., marinas, estuaries draining urbanized watersheds, and industrialized port facilities). These shallow habitats also contained a disproportionately high mass of contaminants relative to their area. Despite the relatively widespread anthropogenic enrichment of Southern California Bight sediments, only 1% of the Southern California Bight was at a moderate to high risk of adverse biological effects based on empirically derived sediment quality guidelines. Risk, however, was not evenly distributed throughout the Southern California Bight. The greatest risk of adverse biological effects was found in sediments of marinas, Los Angeles estuaries, and large publicly owned treatment works (POTWs); these were the only habitats for which the mean effects range-median quotient exceeded 0.5. The least risk was observed in sediments associated with the Channel Islands and small POTWs, for which all sites were considered to be at low risk of adverse biological effects.

A comparison of foraminiferal faunal trends in pristine and impacted regions on the continental shelf and slope of the Southern California Bight, as well as variations in the temporal foraminiferal distribution patterns from 1955 to 1998, suggest that the benthic microfaunal communities have been greatly affected by the presence of contaminated sediment near the major outfall sites. Six species were most impacted: Trochammina pacifica, Bulimina denudata, Eggerella advena, Buliminella elegantissima, Nonionella stella, and Nonionella basispinata. The silver contaminant-tolerant and organic-waste indicating species Trochammina pacifica and Bulimina denudata dominated the outfall regions in the mid-century but declined in abundance in the 1990s after sewage treatment and sludge disposal activities improved. Over the same time period, the abundance of Eggerella advena, a pioneer colonizer of formerly impacted waste-discharge sites tolerant of most trace-metal and organic contaminants, increased dramatically on the shelf, whereas Buliminella elegantissima, a nitrogen-favoring taxon, dominated the nearshore regions except at the pristine site. In contrast, the contaminant-sensitive species Nonionella stella and Nonionella basi-spinata dominated the shelf assemblages in pristine to low-impacted areas in the late 1950s and early 1960s but were rare to absent near the outfalls, even after remediation efforts were put into effect. Although most other species patterns, as well as the amphipod survival and sea urchin fertilization tests, show that the enhanced sewage treatment programs improved sediment conditions, the inability of Nonionella stella and Nonionella basispinata to reinhabit formerly colonized areas suggests that not all faunal trends have returned to pre- or early-outfall levels even with remediation. The sensitivity of foraminifers to the presence of contaminated sediments suggests that they are a useful tool in evaluating the impact of anthropogenic contamination on microfaunal communities.

A unique opportunity to compare the structure of soft-bottom macrofaunal communities to environmental sediment characteristics arose during a multi-agency sampling survey in Santa Monica Bay. Macrofaunal species, sediment chemistry, highly partitioned sediment granulometry, and depth inventoried at 24 sites, were extensively analyzed to determine community relationships, natural species distributions, and response to anthropogenically derived sediment variables. By employing parsimony analysis, specifically a derived variant of parsimony analysis of endemicity utilizing step-matrices to accommodate species abundance, and multivariate methodologies launched from the branch-length distance matrix derived from the cladogram, community structure was assessed based on the hierarchical or nested spatial relationships of the species and sample areas. Since spatial autocorrelation is implied by the cladistic and hierarchical relationships of the sample localities, and because hierarchically related objects do not comprise independent nor identically distributed data points, the novel application of independent contrasts (correcting for the nonindependence of the data distributed on the cladogram) was used in combination with traditional statistical methods (that assume observation independence). Both approaches revealed moderate to strong correlations of several abiotic factors with community structure, and between the various phylodiversity and response indices to numerical effects-based sediment quality guidelines. Specifically, community relationships were correlated with depth, polychlorinated biphenyl, several clay-mineral species, and certain sediment phi size bins. Phylodiversity indices correlated more highly with sediment quality guidelines than did the benthic response index.