Core Area One of the Proposed Marine Sanctuary Expansion
Santa Lucia Bank, Santa Lucia Escarpment, Arguello Canyon
and the Persistent Upwelling between Point Conception and Point Sal

by Carol Georgi and Karl Kempton, 
former Energy Planner for San Luis Obispo County 
and Lead Author of "Proposed Central Coast National Marine Sanctuary, 1990"        

Introduction and Overview

In a marine sanctuary, a core area is usually an internationally or nationally significant ecological unit that needs primary protection and becomes the central focus of a sanctuary. Vital ecosystems supporting significant marine life are clear candidates for protection. Nationally significant historical and cultural features are also nominated for protection. For example, within our proposed area of expansion, Chumash underwater archaeological sites could qualify for core area designation. Within this proposed expansion area, there are several core areas. This article will focus on Core Area One, which is arguably the most important unprotected oceanographic complex feature along the California coast. 

Core Area One 

* Includes the Santa Lucia Bank, a cetaceous uplift block to within 400 meters of the surface  

* Includes the five-fingered Arguello Canyon, running NE-SW to a depth of 3000 meters 

* Contains a vast array of marine life: benthic (deep water) community of world-wide significance, simultaneous gathering of 13 whale and porpoise species, and large numbers of birds and fish

* Includes an internationally and nationally significant persistent nutrient-rich upwelling passing through the Arguello Canyon and rising between Point Sal and Point Conception * feeds the entire web of life along the eastern rim of the Pacific Basin

Some of the following details have been gathered from the 1990 Proposed Central Coast Marine Sanctuary Document, posted online, SLO Surfrider.org.  Additional details have been added to include areas the document was unable to describe at the time of its writing.

On clear days, Point Arguello can be seen as the prominent western-most point from viewing locations along the northern end of San Luis Bay. From higher ground, Point Conception is visible. The land on which one stands to gaze at this scene is only 25 million years dry. The tectonic, other geologic, oceanographic, and meteorological forces shaping the land are the same forming and shaping the upwelling ocean terrain. This is the southern portion of the Santa Maria Basin; bound on the east by the coastal range, and west on the ocean floor by the upthrust block, the Santa Lucia Bank, 40 miles offshore between Point Sal and Morro Bay. The northern end of the basin ends in the Monterey Bay National Marine Sanctuary at Point Sur. The southern boundary of the basin is the Arguello Canyon. The southern boundary of the Monterey Bay National Marine Sanctuary at Santa Rosa Creek is not a change in either oceanographic features nor ecosystem.

Transition Zone

The persistent, nutrient-rich upwelling flows up the Arguello Canyon, enriching the Santa Lucia Bank, the Arguello Canyon and coastal waters from Point Sal to Point Conception. Here, in a transition zone, blending upwelling nutrients with warm water from the south and cold water from the north, a unique, complex interaction of species and natural phenomena occurs. Feeding the web of life along the eastern rim of the Pacific Basin, the nutrients spread through and beyond both the proposed sanctuary expansion area and designated sanctuary areas, feeding plankontic communities, plants of the kelp forests, and various life stages of marine flora and fauna.

The northern portion of the transition zone between Southern California's warm waters and Northern California's cold waters begins at Point Conception and extends two degrees north to 36 degrees north latitude (20 miles south of Point Sur at Mill Creek Canyon). The proposed sanctuary expansions cover this area north to Santa Rosa Creek. The area is the meeting place of the Oregonian Temperate Eastern Pacific and the Californian Subtropical American Eastern Pacific climates and waters. The region is dependent upon, as well as a cause of, the complex interaction of the southward moving California current, the warmer northward moving subcurrent, the near-shore northward moving seasonal Davidson Current, and the upwelling. The dynamics are not fully understood. Systematic, ecosystem-based research is needed.

The Oregonian weather pattern brings strong northwesterly winds during the spring, a cool marine layer with much fog during the summer, and generally strong wet storms during the winter. The warm, clear autumn months are generally dominated by the California Subtropical climate, which also tempers colder winter weather from the north.

The California Current system flows from the North Pacific and is driven by planetary rotation and large scale winds. Offshore circulation is dominated by this current for most of the annual cycle. The current flows along and near surface at the edge of the continental shelf. It is generally comprised of low-temperature, low-saline, subarctic waters. The current's position and intensity varies with season and latitude; several coastal currents oppose it. 

At the inner edge of this system is the California Undercurrent, characterized by warm saline water. The undercurrent ranges to within 100 kilometers of the coast; it runs from Baja California to Washington State. The undercurrent surfaces in the winter along the coast of Central California.

Closer to land, between the months of October and April, the Davidson Current flows northward along the surface from Point Conception to British Columbia. Its rate, strength, and position vary according to wind patterns caused by dominant seasonal northwesterlies from the Oregonian regime.

Marine Life 

Benthic (deep water) communities of world-wide significance thrive in the area. The high diversity and density of benthic populations resemble the North Sea and the Georges Bank, which have been two of the most productive regions in the world. The meiofaunal (small benthic invertebrates) community is among the highest density reported world-wide. The macroinfauna diversities and abundances are much larger than those north or south along the coast of California. The abundance of benthic populations appears related to the area's unique combination of characteristics: the transition zone, the geology of the area, composition of the sea floor, complex currents, and the upwelling itself.

The Santa Lucia Bank area is frequently visited year round by cetaceans (whales, porpoises, dolphins). During the fall season at least 13 species of cetaceans have been observed, including simultaneous feeding bouts among humpback, Baird's, fin, blue, and sperm whales and smaller species.

Numerous fish species are harvested commercially. Among harvested species are sablefish, dover sole, shortspine, longspine, and rex sole. Flora and fauna of the area are associated with two distinct oceanographic and climatic provinces. The habitat is the southern boundary of the range for many northern species, and the northern boundary for southern species.

Further research is needed to study the number of bird and fish species found at the Santa Lucia Bank during different seasons. Large numbers of birds have been observed by fishermen during feeding periods. Density maps of seabird populations illustrate the richness of the area. Eastward of the Santa Lucia Bank are a number of unanalyzed spawning areas for fish. 

Some of the Threats to the Nutritious Persistent Upwelling 

There are many threats to the upwelling as a nutrient source.  First and foremost is an oil spill. Despite safety assurances, earthquake or human error can cause a spill. There is no existing cleanup technology for the rough, wind-driven seas of the Santa Maria Basin. Drilling operations add toxins to the ocean environment. With rising ocean levels, the nation's largest underground spill by Unocal in the Oceano-Guadalupe Dunes continues to be a threat.  (See Slo Coast Journal, July, 2010)

Another threat is the constant chemical run-off into rivers and streams from commercial farming operations in the forms of fertilizers, pesticides, fungicides, herbicides, and pharmaceutical-laced animal urine. Sewer treatment plants along the Santa Ynez River need to be upgraded to capture all household chemicals and pharmaceuticals. Urban run-off is an additional problem.

Other threats to the upwelling area north of Point Sal include the Santa Maria River watershed that has tested positive for high levels of human and animal fecal bacteria. "Twenty-eight out of 31 monitoring sites in the Santa Maria watershed—which is spread throughout the Santa Maria Valley, Nipomo, Guadalupe, and a portion of the Los Padres National Forest—were considered "impaired" due to high levels of FIB (E.Coli, Coliform, or Enterococcus). (See Santa Maria Times)

Within the watershed, high levels of pesticides have been reported in fish in the Oso Flaco Lakes and ocean shore fish south of the Pismo Pier. (See San Luis Obispo Tribune) Also, pollutants in ocean currents moving north around Point Conception from the Southern California Bite are a growing threat as populations continue to increase while sewer treatment plants fail to capture industrial and household chemicals and pharmaceuticals.

Additionally, as the Davidson current moves nutrients northward of this area, all sewer outfalls add these chemical cocktails to the ocean waters, affecting filter feeders and those who eat them. Recent studies of cancer in gobi fish in Morro Bay National Estuary (MBNE) are linked to the California Men's Colony sewer treatment plant waters flowing into Chorro Creek, which empties into the MBNE. The studies underscore that these pollutants affect California waters and the ineffective mechanical/traditional treatment plants are probable sources of these chemicals. (See eScholarship)

Lastly, is the threat of toxins moving through the geologic sedimentary formation layers from the closed class one Casmalia Dump in Santa Barbara County? It is a super fund cleanup site that may be leaking. The public has not been informed as to how much is leaking, nor if the toxic materials may be migrating towards the ocean upwelling area, given the slant of the sedimentary formation.

All of these threats, as well as others not mentioned, underscore the importance to expand a national marine sanctuary to protect, study, and sustain Core Area One.

Banner Image of Otter & Pup by Cleve Nash