Photo: Benjamin L. SaenzThe vast majority of the Cordell Bank National Marine Sanctuary consists of open waters - three-dimensional habitat not associated with the seafloor. These waters are categorized by depth into three zones: the epi-, meso- and bathypelagic zones. The epipelagic zone, which includes the upper 200 meters (650 feet) of the water column, is the focus of this habitat section. (For waters deeper than 200 meters, see the Deep Sea section.)
The upper portion of the epipelagic zone receives sunlight that drives photosynthesis in microscopic floating plants called phytoplankton. Phytoplankton form the base of the complex and diverse open-ocean food web.
Upwelling in the spring and summer fuels blooms of phytoplankton, which in turn feed zooplankton and some planktivorous fishes such as anchovies and sardines. Zooplankton such as larvae, copepods, krill and gelatinous organisms are eaten by a wide variety of large, highly mobile animals, including squid, fishes, sea turtles, seabirds and mammals. Check out this 2.5 min animated video about krill.
Coastal upwelling occurs within about 50 kilometers (31 miles) of shore, but upwelling does not occur uniformly along the central California coast. Instead, there are upwelling centers often associated with coastal promontories or headlands where upwelling is intense and localized.
Point Arena, located northeast of Cordell Bank, is one such upwelling center. Nutrient-rich water upwelled at Point Arena is then transported south along the Sonoma coast by wind-driven surface currents and the south-flowing California Current, where it is delivered into the sanctuary and offshore areas over Cordell Bank. The Point Reyes headlands also deflect the south-flowing surface waters out toward Cordell Bank and the sanctuary. Localized upwelling may also occur at Bodega Canyon and Cordell Bank.
The productivity in the open ocean, driven by the infusion of nutrients from upwelling, sustains a dynamic marine system in the waters around Cordell Bank. Foraging hotspots in the vicinity of the bank have been identified for a number of fish, marine mammal and seabird species. This community includes both resident species and migratory animals traveling thousands of miles across the Pacific Ocean that are lured by these food-rich coastal waters.
El Niño events affect the composition and structure of open-ocean communities off northern California. Some of the resulting changes are related to reduced upwelling and associated declines in primary production and a subsequent reduction in the biomass of zooplankton and forage fishes.
Decreased food supply during El Niño conditions contributes to mortality and decreased reproductive success of local predatory fish and seabird populations. In addition, changes in current patterns and increased water temperature are related to immigration of warm-water species and emigration of cold-water species.
Changes in oceanographic conditions due to Pacific Decadal Oscillations and interannual changes in intensity and timing of upwelling in the spring/summer also change the presence, distribution and abundance of marine organisms in the sanctuary. One such change in the sanctuary's open-ocean ecosystem is the recent appearance and persistence of Humboldt squid - a voracious top-level predator that could alter the pelagic and benthic communities.
Commercial, recreational and other human interests play an important role in the open ocean, since many economically valuable resources - such as salmon, some rockfish species and occasionally tunas and billfishes that demand fair to high market value - are sustained by and caught in this ecosystem. These areas that are productive for fisheries also attract marine organisms that are not harvested, such as seabirds, leatherback sea turtles, and whales. Therefore, in some cases conflicts develop between human use and resource protection.
Human impacts, such as commercial vessel traffic and marine debris, have the potential to harm or disturb the natural behavior of open-ocean animals. Vessel spills, for example, are a serious potential threat to Cordell Bank's resources.
Historically, the total number of oil spills from transiting vessels has been small, but the potential impacts may be enormous, given the number and volume of vessels and the sensitivity of resources in the area. Monitoring the distribution, behavior and movement patterns of animals within the sanctuary relative to human activities and potential threats will help to identify activities that may negatively impact animal populations in sanctuary waters.
The Great White Shark (Carcharodon carcharias) is one of the most-feared predators in the sea, but has more to fear from man. Copyright Monterey Bay Aquarium. Photo taken by Steve K Webster.
<em>Citharichthys sordidus</em> (Pacific Sanddab; Paralichthyidae) collected during mesopelagic fishes survey aboard NOAA SHIP Bell M. Shimada, offshore Santa Cruz (SESA 6), 0-168 meters, May 2015. Identified by Robert N. Lea (CAS) and Erica J. Burton (MBNMS). Scale: Centimeter ruler.
The sanctuary is far enough offshore to be relatively free of direct impacts associated with terrestrial inputs, and as a result, it is thought that water quality within the sanctuary is relatively good. There is no evidence of eutrophication or HABs within this sanctuary.
MonitoringThe open ocean encompasses more area than any other habitat in the sanctuary, and it is one of the most difficult to study. The dynamic and ephemeral nature of short-term processes are nested within coast-wide processes occurring on decadal and even longer time scales.
Unlike intertidal systems, which are easy to access and lend themselves to manipulative experiments, the open ocean is vast, and rough conditions make research difficult. Furthermore, many open-water organisms are very difficult to study either due to their large size and high mobility (often swimming from one region to another) or their small size and fragility.
Open-ocean monitoring programs in the sanctuary study a wide variety of issues such as physical oceanography, krill abundance, and seabird and marine mammal distribution and abundance. Several agencies and research groups are actively studying the physical, chemical and biological properties of the California Current. In addition, a number of efforts are underway to understand the migration patterns of large predators in the North Pacific basin and how the animals act and interact in open-ocean habitats.
Applied California Current Ecosystem Studies (ACCESS)
ACCESS is a research partnership to support integrated ocean management in northern and central California. Point Blue, Cordell Bank and Greater Farallones National Marine Sanctuaries have been investigating the spatial and temporal relationships between oceanographic processes, zooplankton, and marine birds and mammals in the region surrounding Cordell Bank and the Gulf of the Farallones. This project has several objectives, including: 1) Understand how the timing, intensity, and duration of upwelling influences the distribution and abundance of euphausiids (better known as krill) thus affecting the distribution and abundance of krill predators in the region; 2) Identify persistent locations of predator and prey aggregations and potential areas of high trophic transfer in the Gulf of the Farallones region that may be associated with bathymetric and hydrographic features; 3) Monitor physical and biological characteristics of the pelagic ecosystem, with the goal of developing indicators of ecosystem health, to understand change on a variety of scales and detect natural and anthropogenic impacts.
Research cruises have been conducted in spring, summer and fall (three to five cruises per year) from 2004 to the present. This study has shown large inter-seasonal and inter-annual differences in lower trophic level abundance as well as predator presence in the sanctuaries. This assessment of the pelagic system specifically meets the sanctuary's mandate to conduct long-term monitoring of the resources within the sanctuary and provides important information for resource protection and management.
Cordell Bank Ocean Monitoring Program
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.
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.
CSCAPE: Collaborative Survey of Cetacean Abundance and the Pelagic Ecosystem
CSCAPE was a collaboration between the National Oceanic and Atmospheric Administration (NOAA) Fisheries and the National Marine Sanctuary Program to assess the abundance and distribution of marine mammals and characterize the pelagic ecosystem off the U.S. West Coast. Cruises were conducted every three years and cover the entire West Coast, from the northern boundary of Washington to the southern boundary of California, including concentrated sampling within the West Coast sanctuaries.
The project had three objectives:
- to conduct a marine mammal assessment survey within approximately 300 nautical miles of the shore, with additional fine-scale surveys within the sanctuary boundaries
- to characterize the pelagic ecosystem within the study area through the collection of underway and station-based biological and oceanographic data, seabird studies and acoustic sampling
- to conduct biopsy sampling and photo-identification studies of special-interest species
Tracking Black-Footed Albatross Movements and Conservation
The Black-footed Albatross, Phoebastria nigripes, has been recently listed as endangered by the World Conservation Union (IUCN). Assessing albatross movements and habitats during the post-breeding season is a top conservation priority.
Since 2004, the sanctuary has been supporting research by Oikonos Ecosystem Knowledge to study the post-breeding migration patterns and movements of Black-footed Albatross in the eastern Pacific Ocean. Twenty-eight birds were tagged in central California during the first three years of this study (2004-2005, 2007). Males and females were found to occupy different oceanic regions during the post-breeding season, with males venturing farther west than females. Data from 2004-2005 indicate that the tracked birds spent approximately 60 percent of their time in the high seas beyond national Exclusive Economic Zones. Of the time spend in U.S. territorial waters, 42 percent was spent within the three central California national marine sanctuaries.
Rockfish Mid-Water Trawl Pre-Recruit Survey
Rockfish productivity is tightly related to recruitment success. During May and June every year since 1983, the NOAA Fisheries Southwest Fisheries Science Center (SWFSC) has performed an annual survey of the distribution and abundance of pelagic juvenile young-of-the-year (YOY) rockfishes. The survey extends from San Diego in the south to the northern boundary at Delgada, just south of Cape Mendocino.
YOY rockfish catches show a large degree of temporal variability. The temporal abundance patterns were found to be similar among many of the different rockfish species. This survey also collects information on marine mammal and seabird distributions.
Tagging of Pacific Pelagics (TOPP)
A pilot program of the Census of Marine Life, the Tagging of Pacific Pelagics (TOPP) research project is part of an international endeavor to determine what lives in the world's ocean. TOPP scientists explore the Pacific using satellite-tagged animals to gather data about their world. The results coming from these satellite-based research projects are expanding our understanding of marine wildlife and the role of the sanctuary in their feeding and migratory patterns. Animals that are tagged include various species of marine mammals, seabirds, fishes, reptiles and invertebrates.