Research Areas > Regional Monitoring > Bight '94 to '03 Offshore Water Quality

Project: Bight '94 to '03 Offshore Water Quality

Background and Objectives

The Offshore Water Quality component of the Southern California Bight (Bight) Regional Monitoring Program focuses on assessing condition of the water column in the near coastal ocean. Offshore Water Quality was one of the initial elements of the Bight Regional Monitoring Program, initially implemented as part of the 1994 Regional Monitoring Pilot Project. The pilot project led to formation of the Central Bight Water Quality group, a collection of four large discharge agencies that now conduct coordinated Comparative Toxicogenomics Database (CTD) surveys between Ventura and Orange Counties on a quarterly basis. The Bight Offshore Water Quality program, conducted once every five years, builds from this existing collaboration to bring additional partners and expand the variety of parameters measured and questions addressed.

To date, this program has involved:

• Detecting the spatial extent of POTW outfall and urban runoff plumes;
• Estimating the relative contribution of nutrient loads from upwelling, wastewater effluent discharge, atmospheric deposition, and terrestrial runoff;
• Characterizing the spatial and temporal patterns of algal blooms using a combination of gliders, pier-based and ship-based sampling, and remotely-sensed ocean color and modeling, in order to determine correspondence between blooms and input sources of nutrients; and
• Piloting the use of nitrogen stable isotopes to discern major nutrient source(s) present during phytoplankton bloom conditions.

Status

This ongoing program was initiated in 1994.

Methods

The Offshore Water Quality component initially focused on assessing the spatial extent to which plumes from the four largest POTW outfalls in southern California could be detected. In 1998, the program was expanded to also assess the spatial extent of urban runoff plumes and how they interacted with plumes from POTW outfalls. The 2003 program addressed a similar question about the extent of stormwater plumes, but focused on wet weather and expanded on the 1998 effort in two ways. First, it expanded the number of parameters measured. Whereas the 1998 effort focused on CTD (conductivity, temperature, and depth) measurements that described the physical presence of the plume, the 2003 effort added toxicological and microbiological sampling to describe the offshore distance of plume impacts. Additionally, the 2003 program placed emphasis on evaluating how remote sensing and real-time measurement tools that were part of the Southern California Coastal Ocean Observing System (SCCOOS) could assist in detecting plume impacts.

In addition to the core sampling, the Bight Offshore Water Quality program typically includes a number of special studies conducted at a subset of sites to evaluate exploratory issues. In 2003, this involved sampling of Pseudo-nitzschia (a harmful alga that produces potentially toxic domoic acid) in the Los Angeles harbor and on the San Pedro shelf.

Findings

Plumes from river mouths were generally found not to be measurable in the ocean during dry weather. However, following storms, most of the major stormwater drainage systems created a spatially extensive freshwater plume that reached about 10 km offshore for small storms and 20 km for medium storms. These were often measurable for at least 3-5 days. The biological effects of the plumes were generally found to be spatially limited to the first 2 km offshore and the upper 5 m of the water column; they dissipated after about two days following storms. Remote sensing tools were found to be critical for interpreting the ship-based data, given the rapidity with which storm plumes evolved. However, remote sensing tools were mostly limited to predicting presence of the plume and were not found to be a suitable substitute for the in situ biological measures.

The 2003 harmful alga study found domoic acid concentrations in that area to be among the highest in US coastal waters. This finding led to a 2008 study assessing whether anthropogenic nutrient contributions to the coastal ocean exacerbate the frequency, magnitude or duration of harmful algal blooms in Southern California.

Partners

More than 30 organizations have participated in the Offshore Water Quality component of the Bight regional monitoring efforts.

Data

• Data from Bight '03
• Data from Bight '98
• Data from 1994 Bight Pilot Project