Southern California
Schiff, K.C.; Allen, M.J.; Zeng, E.Y.; Bay, S.M. (2000). Southern California, in: Sheppard, C.R.C. (Ed.) Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. pp. 385-404
In: Sheppard, C.R.C. (Ed.) (2000). Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. Pergamon: Amsterdam. ISBN 0-08-043207-7. XXI, 934 pp., more
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Document type: Review
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| Authors | | Top |
- Schiff, K.C.
- Allen, M.J.
- Zeng, E.Y.
- Bay, S.M.
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| Abstract |
The Southern California Bight (SCB) has undergone tremendous changes over the last 100 years resulting from natural and anthropogenic alteration of the coastal zone. A large influx of population during the 1900s has propelled the coastal community surrounding the SCB from a small pueblo (<2000 in 1900) to the largest metropolitan centre in the U.S. (> 17 million in 1998). This rapid urbanization has placed extreme pressures on marine resources including loss of habitat, discharge of pollutants, and overfishing. As the population has grown in the four counties bordering the shoreline of the SCB, so have discharges of pollutants to the ocean. The major source of pollutants in the early 1970s was publicly owned treatment works (POTWs). Regulation of these discharges has led to improved treatment, source control, and pretreatment programs. As a result, cumulative pollutant loads for POTWs have been reduced several fold, even orders of magnitude for some constituents. Similar to trends observed in many areas of the nation, non-point sources have become larger contributors of potential pollutants as POTWs have reduced their inputs. In the SCB, urban runoff contributes more trace metals (chromium, copper, lead, and zinc) and nutrients (nitrate and phosphorus) than all other sources combined. As the inputs of pollutants have declined and the dominant sources have shifted, the fate and distribution of pollutants in the SCB has changed over the last 30 years. Studies have observed decreasing concentrations in water, sediments, and biota. For example, decreasing concentrations in near-surface sediments are recorded in sediment core profiles. Also, fish tissue concentrations have decreased compared to similar measurements made in the 1970s and 1980s. However, legacy inputs continue to place both the marine ecosystem and public health at risk. Among the most important constituents of concern in the SCB is total DDT (o,p' and p,p' isomers of DDT, DDE, and DDD). Total DDT is widely dispersed; it is measured in 89% of the SCB sediments and has contaminated nearly 100% of Pacific and longfin sanddab populations. In regions where sediment concentrations of total DDT are highest (e.g. Palos Verdes Shelf), commercial fishing is prohibited and recreational anglers are warned about consuming tainted bottom-feeding fish. Along with reductions in pollutant inputs over the last 30 years, scientists have observed the recovery of some marine ecosystems. Five phylogenetic groups are evaluated in this article including kelp (algae), benthic invertebrates, fish, seabirds, and marine mammals. Among the most-studied groups are benthic infauna and fish communities. In 1994 approximately 91% of the SCB mainland shelf contained benthic communities classified as "reference." Although fish diseases (e.g., fin rot and epidermal tumours) were common in the 1970s, their occurrence is currently at background levels. In almost all cases, interactions have occurred between natural and anthropogenic factors. For example, kelp beds near large POTW discharges that were a fraction of their historical extent in 1970 have shown exceptional recruitment and are currently flourishing. However, during the same time period, natural events such as the 1987-88 El Niño negatively impacted the kelp and reduced bed extent to levels not observed since 1970. Ecosystem management of the SCB is improving as we enter the new millennium. The improvement began when resource managers recognized that traditional monitoring programs were not providing the information they needed to make responsible stewardship decisions. Regulatory and permitted discharge agencies have since created an open dialogue to identify the most important monitoring objectives. In addition, they have cooperatively designed and implemented a coordinated, integrated regional monitoring program. Regional monitoring has evaluated the full range of natural variability and cumulative impacts from multiple discharges, enabling assessment of the overall condition of the SCB. |
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