Ecology of the Southern California Bight: A Synthesis and Interpretation
Ecology of the Southern California Bight: A Synthesis and Interpretation
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| ISBN-13: | 9780520322400 |
|---|---|
| Publisher: | University of California Press |
| Publication date: | 11/15/2023 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| File size: | 36 MB |
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Ecology of the Southern California Bight
A Synthesis and InterpretationUniversity of California Press
Copyright © 1994 Murray Donald Dailey, Donald J. Reish, and Jack W. AndersonAll right reserved.
ISBN: 0-520-07578-1
Chapter One
The Southern California Bight: Background and SettingMurray D. Dailey, Jack W. Anderson, Donald J. Reish, Donn S. Gorsline Introduction 1 Exploration and Early Human Inhabitants of the SCB 2 Early Spanish Explorers 2 Spanish Colonization 4 Present Geologic, Climatic, and Oceanographic Setting 5 Geology 5 Winds 7 Currents and Water Properties 8 El Niño 10 Biological Setting 11 Human Impact and Marine Science 14 Population Growth 14 Development of Marine Science 14
Introduction
This work represents a major new effort by experts in many disciplines to contribute to a better understanding of the Southern California Bight (SCB) ecosystem. No other book has attempted to encompass the available literature on the SCB in all the areas of expertise represented in this volume. Toward this goal, each chapter in the work stands alone as a thorough and valuable update on pertinent findings in the field and as a major contribution toward our understanding of the SCB ecosystem.
This book endeavors to provide marine scientists of all disciplines a basic review of recent information gathered in their fields of study from the SCB. Furthermore, the authors of each chapter were challenged to furnish a combined summary and prospectus that serves two valuable purposes. First, it identifies study areas within the field that require further investigation, thus leading the next generation of researchers toward productive and essential study topics. Second, in the final chapter, it supplies the reader with the information needed to understand the synthesis of ecosystem interactions at work in the SCB. We also try to present the material so that those responsible for environmental management within the region will find the information to be a useful tool in future decision making concerning growth and development of the SCB.
The SCB is one of the most studied areas of the United States. Although the name Southern California Bight is a regional name that has not been defined in geologic terms (bight is defined as a bend or curve in the coastline), it is used in this book to describe the southern California continental borderland. The SCB includes an area of about 78,000 km2 of the California borderland. It encompasses that body of water stretching from Point Conception, north of the Santa Barbara Channel, to a point just south of the border between the United States and Mexico (fig. 1.1). The SCB measures about 1000 km in length and has a maximum width from shore to the base of the Patton Escarpment of about 300 km (fig. 1.2). The basin floor depths range from 600 m to over 3000 m. Basin sills deepen progressively south and west to the area of the Santo Thomas Fault, where they then shoal to the south (Doyle and Gorsline 1977).
Exploration and Early Human Inhabitants of the SCB
The body of water making up the SCB, the Pacific Ocean, was first seen by Balboa in 1513. He defined the shoreline for what was the most heavily populated part of the North American continent at that time: California. During that period, the early 1500s, an estimated 700,000 Indians were thought to be living within the boundaries of the present state. Many of the native southern Californians were organized as loose family units, not as tribes. Those inhabiting the Channel Islands and southern coastal areas lived in "wikiups," small grass-covered huts, which were grouped in settlements called "rancheria" by the Spanish. Their diet consisted primarily of seafood, such as fish, abalone, and sea mammals, supplemented with acorn meal and small terrestrial animals such as birds, reptiles, and insects (Narlon 1913).
The last known Indian inhabitant of the Channel Islands was Juano Maria, called the "Lone Woman" of San Nicolas. Reported to have jumped overboard while being evacuated from San Nicolas by priests in 1835, she was discovered by otter hunters nearly 20 years later (1853). She was taken to Santa Barbara where she died a few weeks after her rescue (Smull 1989).
Early Spanish Explorers
The first European explorers to set foot in what is now southern California were a small company of Spanish adventurers commanded by Juan Rodríguez Cabrillo. Cabrillo and his men landed at what is now San Diego Bay on September 28, 1542 (Hartman 1968). When Cabrillo first encountered the San Pedro Bay coastline a week later on October 8, 1542, it offered little or no positive features potential for future use. In the words of Richard Henry Dana, who visited the same area nearly 300 years later (in 1835), 1769 the San Antonio, under the command of Juan Pérez, brought the first European settlers who came to make a permanent home in the SCB area. This was the first of a threefold "occupation" to be carried out by the Spanish government. This occupation incorporated a religious, military, and civil approach that was intended to stem the Russian occupation of Alta California, then encroaching from the north. The execution of this plan was entrusted to José de Galvez, the Royal Visitador of Mexico. The plan called for four military divisions, two to arrive by land and two by sea. Gaspar de Portolá was placed in command as military and civil governor, and Junípero Serra, as Father-President of the Franciscans, would oversee the religious mission (Lavender 1976). On Sunday, July 16, 1769, the first mission in California was founded by Father Serra in what is now known as Old Town in San Diego. Here Mission San Diego de Alcalá was formally dedicated.
During Serra's lifetime, there would be 9 missions established. By the end of the eighteenth century, there would be 18, and with the founding of San Francisco Solano in 1823, the total number reached 21. All 21 missions and their surrounding lands had been established in the southern California area under Spanish rule without expense to the royal treasury. The entire cost had been borne by private parties through what became known as the "Pious Fund." The Pious Fund consisted of money and property given by devout Catholics to the cause of proselytizing the California Indians. By 1768, the fund had reached over $1,273,000 and yielded an income of $50,000 per year to be invested almost entirely in land (Hartman 1968).
Spanish Colonization
At this time, the late 1700s, Spain was attempting to colonize the area bordering what is presently considered to be the SCB. Eleven families recruited from the Mexican provinces of Sonora and Sinaloa followed the trail northward for seven months to become the first settlers in El Pueblo de Nuestra Señora La Reina de Los Angeles de Porciúncula. The new town was founded on September 4, 1781, at a spot near the Indian village of Yang-na, later to become known as Pueblo de Los Angeles (Hartman 1968).
In 1784, the first of the vast California ranchos was established in the area around San Pedro Bay by Juan José Domínguez, a 65-year-old bachelor and veteran of the Portolá expedition. For his devoted service to Spain, Domínguez received a land grant of 74,000 acres, extending from what is now Redondo Beach south to include the entire Palos Verdes Peninsula and some distance eastward. Known as Rancho San Pedro, the original grant encompassed present-day Palos Verdes Estates, Rancho Palos Verdes, Rolling Hills Estates, San Pedro, Torrance, Gardena, Compton, Redondo Beach, Wilmington, Lomita, Harbor City, and Carson.
Other large land grants were doled out in the vicinity of the new pueblo of Los Angeles. Among the recipients was José María Verdugo, who received a large grassland area that covered the present-day city of Glendale and part of Burbank. Another huge grant, adjoining Rancho San Pedro and including present-day Long Beach and other nearby communities, went to Manuel Pérez Nieto. The founding fathers of Los Angeles were given title to their original holdings on the town's fifth anniversary in 1786. Along with the rancheros (those given land grants), these were the first private landholders in the pioneer province (Queenan 1983).
On May 13, 1846, the United States declared war on Mexico and moved American naval units into every port in California. Not long afterward, an uprising took place in Los Angeles when the pueblo inhabitants pobladores grew tired of petty tyrannies imposed by occupation leader Archibald Gillespie. The pobladores chased Gillespie and his soldiers out of Los Angeles and caused the resistance to spread throughout southern California. The resistance ended on December 6, 1846, near the Indian town of San Pasqual. By 1847 the pobladores had capitulated to the United States and the war in the West was over, although it would be another year before Mexico yielded and signed the peace treaty of Guadalupe Hidalgo (Hartman 1968).
Present Geologic, Climatic, and Oceanographic Setting
Geology
The Pacific margin along the western United States is a plate collision boundary that includes the typical narrow shelf (average width 25 km) fronting high-relief, coastal ranges. The shelf passes seaward to a steep slope and marginal trench. This morphology is characteristic of most of the Pacific rim except off southern California and northern Baja California, where continued large- scale overriding of the North American plate by the Pacific plate has produced movements along a major fault zone (San Andreas Fault System) (Teng 1985). The resulting Pacific margin is wide (up to 300 km) and is composed of a series of laterally shifted blocks that produce a roughly checkerboard pattern (Howell et al. 1980) (fig. 1.3).
This checkerboard pattern is formed by basins that are arranged in rough rows trending northwest-southeast and converging to the south. Off California, the depressions are grouped as inner, central, and outer basins relative to the mainland. For the entire province, 23 depressions have been named (Emery 1960), 16 of which are located in the U.S. portion of the borderland. The actual continental slope at the seaward margin is the Patton Escarpment (Uchupi and Emery 1963).
Rivers along the Pacific coast of the United States typically drain tributary basins that are steep in gradient, are small in area, and produce a large amount of sand discharge (table 1.1). Southern California is noted for its mild temperatures, short wet winters, and long dry summers. There are only relatively small changes in these conditions between Santa Barbara to the north and San Diego to the south. Mean rainfall at Santa Barbara and Los Angeles is about 38.1 cm per year, while San Diego has a lower mean of 25.4. Mean annual air temperatures are also similar from north to south. They vary only from 17.8°C in Los Angeles to 15°C and 16.7°C in Santa Barbara and San Diego, respectively. The largest recorded river discharges occur at about 20- to 30-year intervals. The major southern California sediment discharge is delivered by the Santa Clara River in Ventura County, which has its sources in the San Gabriel Mountains at elevations of 2000 m (table 1.1).
This discharge is first sorted by wave action at the coast into coarser particles, usually sands and gravels, which move in traction or in short-term, near-bottom suspension. The coarse fraction travels along the shore within the beach and inshore zone, and offshore to the inner and central shelf at times of strong storm surging. Where submarine canyons cut into the nearshore, as at the ends of each coastal cell, they intercept much of this transport (Inman and Frautschy 1966). Silts and clays are transported as suspended load and follow the water circulation during their slow fall. The influx of fine sediment particulates is generally low except for times of winter runoff and the multi-year cycle of major flooding. Therefore, during much of the year and during dry years, the predominant suspension particulates are of biological origin (biogenic).
Biogenic components undergo extensive recycling before they reach the ocean bottom. Much of this material is probably aggregated in the form of pellets and aggregates of planktonic origin and may be degraded by bacterial action as they sink. Additional aggregation occurs from ingestion by benthic organisms and infaunal reworking. This component reaches the bottom principally by particle or aggregate settling. The process is continuous, but it occurs at varying rates related to the cycle of seasonal blooms. Biogenic particulates contribute about 20% of the total borderland sediment, which also includes carbonate, opaline silica, and other organic matter. During floods or wet seasons, the flux of terrigenous material dominates the deposited sediments.
We can simplify the description of the physical characteristics of the submarine canyons by considering them in relationship to the three environments that they cross: shelf, slope, and basin (trough floor). Emery (1960) states that there are 13 large named canyons and 19 smaller unnamed canyons in southern California. Of this total of 32 submarine canyons, 20 border the mainland, 10 border islands, and 2 are located off submarine banks. The canyons exert an influence on shelf water circulation because of the pumping of water by tide-driven flows up and down the canyon axis. This action draws some of the suspension load to the canyon circulation systems (Drake and Gorsline 1973; Shepard et al. 1979). Much also passes over the shelves in complex circulations and is ultimately concentrated in nepheloid plumes (Karl 1976). These are found in surface waters, in the water column, and as near-bottom turbid layers.
Sandy sediments initially deposited in nearshore canyon heads are progressively transferred downslope by mass movement processes and sediment gravity flows (Nardin et al. 1979). Fine sediments also initially accumulate in canyon walls and deeper canyon floors, where they are then incorporated and carried out of the canyons to submarine fans and basin floors (Sherpard and Dill 1966). This process can be seen in the contours of the seafloor of the SCB (fig. 1.4).
The surface water circulation of the SCB tends to move fine suspended sediment into the Santa Barbara Basin from the California Current system to the west and through the Anacapa Passage from the southeast (Thornton 1981a, b). These conditions produce high rates of fine clay-silt sedimentation in Santa Barbara Basin. As clay content increases, organic carbon content increases. Oxygen demand for the decay of this material utilizes oxygen faster than the rate of recharge.
Continues...
Excerpted from Ecology of the Southern California Bight Copyright © 1994 by Murray Donald Dailey, Donald J. Reish, and Jack W. Anderson. Excerpted by permission.
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Table of Contents
California Bight: Background and Setting
Physical Oceanography
Chemical Oceanography and Geochemistry
Microbiology
Phytoplankton
Zooplankton
Benthic Macrophytes
Benthic Invertebrates
Fishes
Birds
Marine Mammals
Human Impacts
Governance
Ecosystem Interrelationships