Introduction
Important ocean areas can become a National Marine Sanctuary or a Marine National Monument for the preservation and sustainability of the vital ecosystems and oceanographic features. Otherwise, man's destructive activities can destroy such vital areas. Between the Channel Islands and the Monterey Bay National Marine Sanctuaries lies such an area, known as "Core Area One" in the "Proposed Central Coast National Marine Sanctuary, 1990" document.
Proposed: The Santa Lucia Bank and the Arguello Canyon with its Persistent Upwelling become part of a National Marine Sanctuary or become designated a Marine National Monument.
Protection of this area is vital to maintain and sustain the ecosystem-based web of life in the Pacific Ocean on the West Coast of the U.S. This area should become part of a National Marine Sanctuary or a Marine National Monument.
Description
The unique oceanographic combination of the mile deep Arguello Canyon, the pathway for California's—also the West Coast's—only persistent upwelling, the Santa Lucia Bank uptrust block, and the Rodriguez Seamount (a submerged island) create the ideal conditions for an internationally and nationally significant diverse density of marine life. Whales and birds come from as far as Hawaii to feed during the fall at the Santa Lucia Bank. The density and diversity of life is equivalent to the former abundant life of Georges Bank, offshore between Cape Cod, Massachusetts (USA) and Cable Sable Island, Nova Scotia (Canada).
Proposed Marine Sanctuary Extension or National Marine Monument
Location
Located off the California Central Coast between the Channel Islands and Monterey Bay National Marine Sanctuaries, the Santa Lucia Bank is an uptrust block rising to within 400 meters of the ocean surface 30 miles offshore from the north face of the Arguello Canyon to offshore Morro Bay. This area lies within the Oceanographic and Meteorological transition zone of the Oregonian and Californian Providences at the complex meeting place of south and north moving major warm and cold ocean currents.
The area includes:
• The Santa Lucia Bank, a cetaceous uplift block to within 400 meters of the surface
• The five-fingered Arguello Canyon, running NE-SW to a depth of 3000 meters
• The Rodriguez Seamount, similar to and south of the Davidson Seamount
• The West Coast's internationally and nationally significant persistent nutrient- rich upwelling passing through the Arguello Canyon and rising between Point Sal and Point Conception that feeds the web of life of two National Marine Sanctuaries, waters in between and beyond
• The 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, all of which come from near and far in the Autumn.
Oceanographic Summary
Our local geography is currently made up of two microplates forming an important complex sea floor terrane providing rich and diverse habitat for abundant and diverse marine life.
Geography is shaped by geology and the variety of natural forces Mother Nature uses as calligraphy brushes to write her works, including the occasional asteroid punctuation mark. Our local geography is a meeting place of three major tectonic plates. The Farallon Plate, moving eastward was subducting beneath the North American Plate. As the Pacific Plate moved northwest, the subduction eventually ceased in our area as microplate remnants of the Farallon Plate were captured by the Pacific Plate beneath the North American Plate; continental margins of the North American Plate became part of the Pacific Plate. That is, all land and sea floor west of the San Andreas Fault that was part of the North American Plate, became part of the Pacific Plate.
As the Pacific Plate continued its northwest migration subducting under Alaska, it rotated the Arguello Microplate to our immediate south, also known as the Transverse block. It is bordered on its eastern side by the Transverse Range, on the west side by the Channel Islands with the Ventura-Santa Barbara Basin in the middle, and on its northern side, the Arguello Canyon. The rotation ended with the capture of Baja that now presses against this block causing folding and uplift.
The microplate from the Farallon Plate upon which we dwell, the Monterey Microplate, is bordered on the west by the Santa Lucia Bank and the Santa Lucia Escarpment. This microplate is deformed with a subsistence slant from the coastline to the Santa Lucia Bank. At the eastern edge of the Santa Lucia Bank is the Santa Lucia Fault. The Bank is tilted with the uptrust on its eastern most side. The last diagram illustrates the magnitude of the crack in our microplate. Running nearshore is the Hosgri Fault, another huge crack in this microplate. There are many more fault lines known and probably unknown or if known not nearly studied in enough detail. See page 5 of Chapter 2 and Microplate capture, rotation of the western Transverse Ranges . . . (In PDF format.)
Murray Fracture Zone
Schematic Block Diagrams
"Microplate capture, rotation of the western Transverse Ranges, and initiation of the San Andreas transform as a low-angle fault system." Authors: Craig Nicholson, Christopher C. Sorlien, Tanya Atwater, John C. Crowell, Bruce P. Luyendyk: Institute for Crustal Studies and Department of Geological Sciences, University of California, Santa Barbara, California
 Six Part Tectonic Model
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 Magnetic Anomalies Offshore
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Persistent Upwelling
Nearly all upwellings are seasonal and cover only one per cent of the ocean surface, usually near coastlines. Even rarer, perhaps as few as ten world wide, are constant or persistent year round upwellings.
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. This upwelling is ranked as the most important of all the West Coast upwellings. As one of the few persistent upwellings in the world, it is critically important because it is the feeding hotspot for marine life migrating through the West Coast National Marine Sanctuaries. Supporting documentation can be found in NOAA's Biogeographic Assessment of Channel Islands National Marine Sanctuary.
Persistent Upwelling
Transition Zone
The transition zone of the Oregonian and Californian (or San Diegan) Providences is the complex meeting place of south and north moving major warm and cold ocean currents and a blending of upwelling nutrients with warm water from the south and cold water from the north.
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 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 nearshore northward moving seasonal Davidson Current, and the upwelling. The dynamics are not fully understood. Systematic, ecosystem-based research is needed.
Within this zone, 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 Channel Islands and the Monterey Bay National Marine sanctuary areas, feeding plankontic communities, plants of the kelp forests, and various life stages of marine flora and fauna.
Area in Need of Protection
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 worldwide. 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.
Ecosystem-based Research
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.
A detailed description of this area is in our "Core Area One" Marine Sanctuary article, and in the document, "Proposed Central Coast National Marine Sanctuary, 1990."
