Research Areas > Regional Monitoring > Bight '08 Areas of Special Biological Significance

Project: Bight '08 Areas of Special Biological Significance

Background and Objectives

Some Marine Protected Areas are designated as Areas of Special Biological Significance (ASBS), where the discharge of waste is prohibited. There are 34 ASBS throughout the State of California, 14 of which are located in southern California. Despite these regulations, nearly 1,700 outfalls have been identified in ASBS statewide that could carry waste from nonpoint sources, especially in wet weather. Since zero waste discharge is allowed to ASBS, typical regulatory limits (i.e., effluent limits) do not apply. Instead, state regulatory statute stipulates the maintenance of “natural water quality.” However, little information exists on what would be considered natural water quality. Enforcing this objective is especially challenging due to the mix of natural and anthropogenic wastes that may be discharged during wet weather, compounded by large inherent variability in natural conditions.
 

The goal of this project was to answer three questions:

• What is the range of natural water quality at reference locations?
• How does water quality along ASBS coastlines compare to natural water quality at reference locations?
• How does the range of natural water quality conditions compare among ASBS with and without discharges?

Status

This project was initiated in 2008 and completed in 2011.

Methods

Nearly all of the ASBS stakeholders in southern California are participants in this project. A collaborative integrated sampling design was implemented during the 2008-09 wet season, where over 10 agencies collected and analyzed approximately 400 samples.

The project design included:

• A variety of reference locations, based on minimal development in the watershed (nearly all open space) and differences in watershed characteristics (e.g., size, slope, geology).
• A variety of storm events, based on differences in rainfall characteristics (e.g., rainfall quantity, intensity, antecedent dry period).
• A variety of measurements including suspended solids, nutrients, trace metals, organic contaminants, and aquatic toxicity.

In total, 16 locations were sampled before and after storm events ranging from 0.1 to 9.8 cm rainfall, for a total of 35 site-events.

Findings

Water quality did not differ greatly between reference and discharge locations. Geometric mean concentrations of total suspended solids (TSS), nutrients (ammonia, nitrate, nitrite, total nitrogen, total phosphorus), total and dissolved trace metals (arsenic, cadmium, chromium, copper, nickel, lead, silver, and zinc), and polycyclic aromatic hydrocarbons (PAH) from post-storm samples were similar at reference drainage and ASBS discharge sites, averaging a 3% difference across all parameters (except chlorinated hydrocarbons, which were almost entirely non-detectable).

A reference-based threshold was used as a proxy for distinguishing a “difference from natural water quality”. It was determined by asking: 1) if each constituent’s post-storm concentration at the ASBS was greater than the 85th percentile of post-storm concentrations at the reference sites; and 2) if the post-storm concentration at ASBS was greater than the pre-storm concentration. Though water quality was generally similar among sites, some individual ASBS sites did exceed the reference-based threshold, most frequently for nutrients and general constituents, followed by dissolved or total trace metals.

Partners

This project was conducted in collaboration with the State Water Resources Control Board, Regional Water Quality Control Boards 4 and 9, and regulated stakeholders.

Fact Sheet

• Bight '08 Areas of Special Biological Significance Fact Sheet