Open Ocean

The majority of the three northern California sanctuaries consists of open waters – three-dimensional habitat not associated with the seafloor. 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, which form the base of the complex and diverse open-ocean food web.

The open-ocean habitat in these sanctuaries is strongly influenced by the oceanographic patterns of the northern California coast – such as upwelling, which occurs in the spring and summer and fuels phytoplankton blooms. Coastal upwelling, which occurs within roughly 45 to 50 kilometers (28 to 31 miles) of shore, does not occur uniformly. For example, there are two upwelling centers in Monterey Bay National Marine Sanctuary: one near Point Año Nuevo and one south of Point Sur. There is one such center north of Cordell Bank National Marine Sanctuary, near Point Arena, that influences oceanographic conditions within the sanctuary.


The productivity in the open ocean, driven by the infusion of nutrients from upwelling, sustains dynamic marine systems in the sanctuaries. The phytoplankton blooms feed zooplankton and some planktivorous fishes such as anchovies and sardines. Zooplankton (such as larvae, copepods, krill and jellies) are eaten by a wide variety of large, highly mobile animals, including squid, fishes, sea turtles, seabirds and mammals.

Lyopsetta exilis (Slender Sole; Pleuronectidae) 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.
In Cordell Bank sanctuary, foraging “hotspots” exist in the vicinity of the bank for a number of fish, marine mammal and seabird species. In Monterey Bay sanctuary, Point Año Nuevo is such a spot for a number of marine mammal and seabird species that use the island for breeding and resting. The upwelling shadow within northern Monterey Bay is another hot spot – this one for pelagic organisms, including leatherback turtles and harbor porpoises.

In terms of sheer number and diversity, invertebrates rule the region’s open waters. These spineless creatures – including the euphausiid shrimp (krill) and copepods, make up about 95 percent of all described animal species.

Conservation and Management Issues

Many human activities, such as commercial vessel traffic, motorized personal watercraft, whale watching and aircraft overflights, have the potential to harm or disturb the natural behavior of open-ocean animals. Other issues include:

  • Non-point source pollution: Water quality in offshore regions can be threatened or affected by large or continuous discharges from the shore, spills by vessels, illegal dumping activities or residual contaminants from past dumping activities.
  • Oil: Oil and other discharges from sunken vessels as well as illegal discharges from oil tankers and cargo vessels have negatively affected marine organisms from time to time. The threat of an offshore spill is constant.
  • Marine debris: Plastic, in particular, is a worldwide problem. Marine wildlife may ingest plastic particles or become entangled in plastic debris.
  • Introduced species: These “invading” organisms, which are often transported on commercial and recreational vessels and other vectors, are a concern because they can out-compete native species for space and other resources.
  • Harmful algal blooms: A rapid increase in algal species can produce extremely potent toxins, which can cause injury or death to other organisms.


In some cases, monitoring efforts span multiple sanctuaries. For example, the Tagging of Pacific Pelagics (TOPP) ) and CSCAPE studies involve all three northern California sanctuaries. In another example, both Greater Farallones and Monterey Bay sanctuaries are involved in the Wind to Whales project.

Many other monitoring projects focus on the open ocean. Other examples, by sanctuary, include:

Cordell Bank:

  • Distribution and Abundance of Marine Birds, Mammals and Zooplankton Relative to the Physical Oceanography of the Greater Farallones and Cordell Bank
  • Cordell Bank Ocean Monitoring Program
  • Cordell Bank Oceanographic Buoy

Greater Farallones:

  • Sanctuary Ecosystem Assessment Surveys (SEA Surveys)

Monterey Bay: