Water Quality: CBNMS

Cordell Bank National Marine Sanctuary provides habitat for a wealth of biological diversity. Every organism that resides within or moves through the sanctuary depends upon clean water, as do all our commercial and recreational uses.

The sanctuary is far enough offshore to be relatively free of any direct impacts associated with terrestrial inputs. As a result, it is thought that water quality within the sanctuary is relatively good.

The sanctuary’s eastern edge is located 10 kilometers (6.2 miles) from shore and is adjacent to Marin and Sonoma Counties, which are sparsely populated and rural in character. About 80 kilometers to the southeast is the major San Francisco-Oakland metropolitan area, with a population of about 8 million people.

The San Francisco Bay plume, a trail of fresh water that extends out through the Golden Gate, is typically pushed to the south and away from the sanctuary. The plume from the Russian River, which is located 21 kilometers from the sanctuary boundary, may enter the sanctuary in spring, but typically this flow is inshore of Cordell Bank. Due to depth, resuspension of bottom sediments is not thought to substantially affect sanctuary resources.

Water quality within the sanctuary may vary seasonally, due to precipitation and current patterns. For instance, San Francisco Bay water may intrude into the sanctuary during peak runoff in the winter, when ocean currents flow to the north.

As an example, in January 2006, researchers on a pelagic monitoring cruise observed impacts at Cordell Bank from the severe flooding of coastal counties due to heavy rainfall. Debris such as large logs, dock pilings, floats, bottles, balloons, plastic sheets and bags littered the surface waters over Cordell Bank – all likely originating from San Francisco Bay. This event was an indicator that extended El Niño conditions with heavy rains could affect water quality at Cordell Bank sanctuary as water and debris from San Francisco Bay intrude into the sanctuary.

There is no evidence of eutrophication or harmful algal blooms (HABs) within the sanctuary. Chlorophyll levels spanning seven years (1997 to 2004) have been summarized, and it does not appear that chlorophyll levels in the sanctuary during this time approached values that would indicate eutrophication.

Monthly estimates of chlorophyll-a in recent years (2004 to the present) demonstrate similar patterns. In addition, water samples are taken from the sanctuary during monthly monitoring cruises for the California Department of Health Services. The goal is to identify early warning signs of HABs, focusing on the dinoflagellate Alexandrium catenella (which causes paralytic shellfish poisoning) and the diatom Pseudonitzschia spp (domoic acid carriers). To date, there have been no indications of elevated levels of either species.

There is a threat to sanctuary water quality from an accidental oil spill or other discharges from vessels, particularly if a catastrophic spill were to occur from a larger vessel. The northern shipping lane for commercial vessels going into and out of San Francisco Bay terminates within the sanctuary, and an average of 2,000 commercial vessel transits take place each year through this lane. Also, over 100 cruise ships transits into and out of San Francisco Bay each year, with a portion of these passing through the sanctuary heading to or coming from the Pacific Northwest or Alaska. Accidental spills are reported to the USCG’s National Response Center. Most routine, operational vessel discharges allowed by law are not tracked, however.

Oceanographic conditions can influence the impact of an oil spill on the marine environment, affecting the dispersal and accumulation of oil. For example, convergent fronts have been shown to capture oil slicks and influence their movement and dispersion. Thus, fronts could potentially increase the probability of wildlife coming in contact with oil and consuming contaminated prey within the offshore environment.

Monitoring

Cordell Bank Ocean Monitoring Program 
The Cordell Bank Ocean Monitoring Program (CBOMP) collected information on the spatial and temporal variability in the oceanographic system of the Cordell Bank region from 2004 to 2010. Data on the abundance of seabirds, marine mammals, other vertebrates and marine debris were collected by trained observers along six 12-kilometer east-west transects centered on Cordell Bank. Physical and biological characteristics of the pelagic system were measured along transects using a CTD (vertical profiles of salinity, temperature, chlorophyll-a, and light levels at set stations), TSG (continuous surface values of salinity, temperature, chlorophyll-a) and echo sounder (continuous measurements of relative abundance of zooplankton).

Starting in 2010, CBOMP was replaced by the Applied California Current Ecosystem Studies (ACCESS) program.

Marine Biotoxin Monitoring and Control Program
The sanctuary collects samples during the monthly ocean monitoring program (CBOMP) that contribute to the Marine Biotoxin Monitoring and Control Program – a state-wide effort, managed by the California Department of Health Services, that involves a consortium of volunteer participants.

This program is designed to detect toxin-producing species of phytoplankton in ocean water before they harm the public. The phytoplankton monitoring and observation effort can provide an advanced warning of a potential toxic bloom, allowing agencies to focus sampling efforts in the affected area before California’s valuable shellfish resources or the public health are threatened.

Cordell Bank Oceanographic Buoy
The Cordell Bank buoy was deployed in the spring of 2007, through a collaboration between University of California-Bodega Marine Laboratory and Cordell Bank National Marine Sanctuary. The system is comprised of sensors for water velocity, water temperature, salinity, turbidity, chlorophyll fluorescence and wind velocity.

The mooring is located at a depth of 85 meters on the northern part of Cordell Bank, about 20 nautical miles west of Point Reyes. This buoy provides near-real-time data that are linked with regional coastal ocean observing systems and are used by sanctuary staff, research oceanographers and local communities to understand offshore ocean conditions better. Further, over time, this mooring will provide an invaluable record of fluctuations and change in the ocean environment that supports the highly productive marine ecosystem in this region.