George Robertson

THE INFAUNAL TROPHIC INDEX (ITI): ITS SUITABILITY FOR MARINE ENVIRONMENTAL MONITORING

Macrobenthic invertebrate data from the San Pedro Shelf, California, were used to evaluate the Infaunal Trophic Index (ITI). The ITI is a numerical representation of the distribution of dominant feeding groups of benthic fauna that has been used to quantitatively model community response to organic material in the water column and/or substratum. Although ITI has been applied to various monitoring studies in the Southern California Bight and elsewhere and is used as a regulatory tool in management decisions, the index has not received detailed scrutiny. Long-term (1977–1993) benthic infauna data and associated sediment geochemistry (particle size, organic and inorganic contaminants) were used to examine variation in ITI. Results indicated that ITI was affected by water depth, granulometry, distance from an outfall of wastewater to the ocean, year and season, and numerically important species. Variation in ITI feeding groups was also affected by year, season, and station. We argue for a more critical applic...

San Pedro Shelf California: testing the Pearson-Rosenberg model (PRM)

Abstract Based on quarterly sampling ( n = 260) over four years (1985–1989) from Californias San Pedro Shelf, the Pearson-Rosenberg Model (PRM) or organic enrichment was tested for the Orange County ocean outfall. The null hypothesis was that test species, abundance, and biomass curves (SAB) from the shelf closely resemble those from the model. Principal areas of agreement between test curves and model curves include increased abundance and biomass approaching an ocean outfall. Major departures from the PRM include: (1) no sharp decline in SAB curves to azoic conditions, (2) displacement of SAB curves away from the outfall, and (3) opportunistic species did not exclude or eliminate rare species. Moreover, the role of local dominant species (bivalve— Parvilucina tenuisculpta , ostracod— Euphilomedes carcharodonta polychaetous annelid— Capitella capitata ) can greatly influence SAB curves within the model. Bioenhancement should not necessarily be viewed as a diagnostic feature of a polluted site. Since the PRM was originally developed for semi-enclosed, low energy depositional habitats with long residence times (fjords, sea lochs), open ocean, high energy, erosional habitats (coast and shelf) may not be the most appropriate sites to apply this model. Uncritical application of the PRM to the Orange County ocean outfall may lead to unnecessary and costly decisions.

Coefficient of pollution (p): the southern California shelf and some ocean outfalls

Abstract The coefficient of pollution (p) was applied to the southern California shelf including three major ocean outfalls (Whites Point, Orange County, San Diego City). P values from the shelf were considerably lower than those reported for portions of the Gulf of Saronikos for which the coefficient was originally developed. Corrections to an earlier application of p to Whites Point did not change major conclusions, but did change the magnitude of values, reducing them in this case. Within the California shelf there were regional differences in p at various outfalls. There was a significant reduction in p at Whites Point between 1973 and 1984. P values at the Orange County outfall were generally lower than at the other outfalls. In our opinion, the development of an integrated (abiotic- biotic) measure of pollution incorporating granulometry and depth and basic community parameters (number of species and number of individuals) is highly desirable.

Water quality at a major ocean outfall on the San Pedro Shelf, California: summary of a nine-year study

Water quality data (temperature, salinity, dissolved oxygen, pH, light transmission, ammonium, and fecal coliform bacteria) were collected from July 1985 to June 1994 to evaluate the relationship between the ocean outfall and ambient water quality and assess compliance with California Ocean Plan criteria. Data were collected as part of a routine monitoring program of a major ocean outfall on the San Pedro Shelf, California for the Orange County Sanitation District. Very small differences were detected near the outfall between the wastewater discharge and natural seawater for temperature, dissolved oxygen, light transmission, and pH. In contrast, values above ambient were observed almost every month for ammonium, and below ambient for salinity in the nearfield (/spl les/0.5 kilometer [km]; 0.3 miles [mi]) of the outfall in the longshore direction). Occasionally, ammonium was measured above background concentrations in the farfield (0.5-3.0 km; 0.3-1.9 mi). The largest differences from background (three orders of magnitude) were observed for fecal coliform bacteria. Most of the time the higher concentrations were found at depths greater than 10 meters (m) (33 feet [ft]), but they did reach waters at 5 m (16 ft) from December to mid-February when minimal or no water column density stratification existed. While changes due to the discharge of highly treated wastewater have been observed, the data from this long-term monitoring program indicated that there are no environmentally significant water quality effects from the districts discharge. In addition, compliance with state receiving water criteria was achieved well over 90% of the time and all observed values fell within the range of natural variability.