Natural Oil and Gas Seeps: An Environmental Disaster Happening in Slow Motion

Seep Facts

How Seeps Start
Crude oil and natural gas seeps naturally out of fissures in the ocean seabed and eroding sedimentary rock. These seeps are natural springs where liquid and gaseous hydrocarbons leak out of the ground (like springs that ooze oil and gas instead of water). Whereas freshwater springs are fed by underground pools of water, oil and gas seeps are fed by natural underground accumulations of oil and natural gas.  Natural oil seeps are used in identifying potential petroleum reserves. (Global Marine Oil Pollution Gateway)

How Seeps Spread
Seeps release gas as bubbles or oil and gas as oily bubbles or oil as droplets that rise through the water column (bubbleology.com).

This photo shows gas bubbles from the tar seeps in the Coal Oil Point area near the underwater seep tents.   http://www.mms.gov/omm/pacific/enviro/submarine-oil-seep-study/submarine-seeps.htm 

Viewed at the sea surface, seeps range from being so diffuse that they are undetectable to appearing on the surface as areas of effervescence or boiling, measuring 1 to 10 meters in diameter. [6]   A large amount of seepage takes the form of gas bubbles that emerge from the seafloor, carrying a thin coating of oil on their surfaces. Seepage also occurs as discrete oil droplets and as tar that oozes out and forms tar mounds on the seafloor. (Santa Barbara County Energy Division)

How Seeps Pollute
The Ocean/The Air
To understand the impact of seeps on the environment and global climate requires significant interdisciplinary advances in a range of areas. These include spatial and temporal distributions of seep emissions globally, bubble and bubble plume processes, the interaction of currents and winds and waves with seep plumes and surface oil slicks, multiphase migration through fractured rocks and faults, and improvement in numerical modeling efforts. Additionally, seeps provide a bioavailable energy source, which supports chemosynthetic communities, but the carbon cycle pathways are just beginning to be understood. Fortunately, recent studies are rapidly increasing our knowledge and understanding (bubbleology.com).

The Ocean: As seep bubbles rise to the ocean surface, substantial amounts of hydrocarbons dissolve in the water column, forming a subsurface gradient of dissolved hydrocarbons, principally methane.  As the hydrocarbon-rich zone spreads out, methane concentrations decrease due to dilution and probably outgassing to the atmosphere. Part of the dissolved fraction may be carried hundreds of kilometers out to sea. Oil slicks of varying thickness form on the sea surface and spread out under the influence of wind and currents. As the oil loses its lighter fractions and undergoes weathering, some of it sinks to the ocean floor, some is dispersed by wave agitation into the water column, and some eventually washes up on shore or sticks to rocks near the high tide line (Santa Barbara County Energy Division).

Even though the quantities released are comparable, there are differences in the impacts from the pollution from single-event, catastrophic oil spills and ongoing, chronic natural gas and oil seeps. However, many researchers use natural seep areas as living laboratories for the study of the fate and effects of oil spills.

It is also worth noting that there is the potential for earthquakes to account for unusually large flows from some seeps (Levorsen 1967). Following the 1971 San Fernando Valley earthquake, several of the previously inactive oil seeps in the area resumed activity. (Mandel 2004)

The Air: The remaining seep bubbles that do not dissolve continue to the surface and burst, releasing the gaseous components to the atmosphere. The more volatile liquid seep constituents soon enter the atmosphere by evaporation (SB County Energy Division). Air pollution caused by the natural seeps is related to the amount of reactive hydrocarbons contained in the seep gas that escapes from the ocean floor and rises to the surface like carbonated soda bubbles. These hydrocarbons, known as reactive organic compounds (ROC), react with sunlight to create smog. Hydrocarbon seeps comprise the largest source of marine methane emissions. (Judd and Hovland 1992)

How Seeps Impact Santa Barbara

Huge, natural seeps have been spewing oil and gas into the Santa Barbara Channel for centuries. According to the Minerals Management Service (MMS) and other sources, the resulting tar was used by the Chumash and other native populations for water-proofing baskets and pitchers and for caulking small boats. Early California pioneers (circa 1850) used the oil from natural seeps to grease their wagon wheels and settlers and ranchers, especially in the Santa Barbara, Ventura, Los Angeles, and Orange county areas, used seeped oil for lubricating farm machinery, for tarring roofs, and for illumination.

Scientists have been studying the effects of the intense offshore oil and gas seepage in the Santa Barbara Channel since the 1940s. Studies have shown that seeps are a major source of pollution in Santa Barbara County.  Click here to see striking photographs taken during MMS studies of the seeps offshore Santa Barbara.
 http://www.mms.gov/omm/pacific/enviro/submarine-oil-seep-study/submarine-seeps.htm 

Tar seeps visible from the surface at Gaviota come from seeps that resemble flat patties on a predominately sandy ocean floor.

Tar "whips" on the ocean floor (left) break off and float to the surface

Ocean
Hydrocarbon seepage from the world's continental shelves affects ocean chemistry.   Methane bubbles dissolve other gases, notably hydrogen sulphide and carbon dioxide, during their ascent. Under suitable temperature-pressure conditions, gas hydrates may be formed close to or at the seabed.  Black sulphide-rich sediments and mats of sulphur oxidizing bacteria are frequently observed close to the sediments surface at seep sites, where there might be a sharp oxygenated/anoxic boundary (Dando and Hovland 1992).

Beach
The natural oil and gas seeps beneath the Santa Barbara Channel cause oil to drift to the ocean's surface, producing a persistent oil slick that's usually carried north and west by ocean currents, generally coming ashore between Santa Barbara and Gaviota. As the oil rises to the surface and floats, it coagulates and biodegrades into tar. This is the same tar that is found on the beaches along the Santa Barbara coastline.

As a result of weather and ocean conditions, the greatest amount of tar appears on Santa Barbara beaches during the summer months. The amount of tar that ends up on the beach is also affected by wave activity, since high surf conditions tend to break up the oil slick and prevent it from reaching the beaches.

To the dismay of local beach-goers, sticky globules of tar lap up onto our coastline every day. This tar is an annoyance to many of us and is often perceived to be a man-made pollutant. In fact, the tar results from huge, natural seeps that have been spewing oil and gas into the Santa Barbara Channel for centuries.

The natural oil and gas seeps beneath the Santa Barbara Channel cause oil to drift to the ocean's surface, producing a persistent oil slick that's usually carried north and west by ocean currents, generally coming ashore between Santa Barbara and Gaviota. As the oil rises to the surface and floats, it coagulates and biodegrades into tar. This is the same tar that is found on the beaches along the Santa Barbara coastline.

As a result of weather and ocean conditions, the greatest amount of tar appears on Santa Barbara beaches during the summer months. The amount of tar that ends up on the beach is also affected by wave activity, since high surf conditions tend to break up the oil slick and prevent it from reaching the beaches.

The most heavily impacted beaches are those between Goleta Point and El Capitan Beach, although wind and currents oftentimes take the oil slick northeast onto Santa Barbara city beaches and as far away as Los Angeles beaches. Surprisingly, scientific evidence indicates that the Coal Oil Point seeps are responsible for half of the tar that washes up on the Los Angeles County beaches.

Marine Wildlife
Our coastal waters are home to rich and diverse marine environments.  Point Conception is often identified as the transition point between two biogeograhic provinces: the colder Oregonian Province and the warmer California Province. Because of the confluence of these two bioregions, the areas offshore Santa Barbara support a great diversity of marine species, many of which are extremely rare and afforded special protection under federal and state law.  These include over 195 species of birds that use the open water, shore, or island habitats in the area; at least 33 species of cetaceans; 7 species of pinnipeds; and the southern sea otter.  All can be negatively impacted by oil pollution.

Oil pollution, in general, can have a smothering effect on marine life, fouling feathers and fur. It is a toxic poison that birds and mammals often ingest while trying to clean themselves. Fish absorb it through direct contact and through their gills. The fumes and contact with oil can also cause nausea and health problems for people in affected areas and influenced by weather, temperature and wind.

Even when the oil does not kill, it can have more subtle and long lasting negative effects. For example, it can damage fish eggs, larva and young — wiping out generations. It also can bio-accumulate up through the food chain as predators (including humans) eat numbers of fish that have sub-lethal amounts of oil stored in their bodies.
Although seep-related fatalities are rare, low-level hydrocarbon exposure might be a significant stressor for animals living in seep areas. Systemic poisoning from chronic exposure could weaken the animals, making them more vulnerable to disease and other perils, including oil spills (SB County Energy Division).

Marine Mammals:  The natural oil seeps in Santa Barbara's Channel produce a persistent oil slick on the ocean's surface. It is the same oil that is extracted from formations in the area.

The lethargic behavior of oiled seals following the Exxon Valdez oil spill was not attributed to blanketing effects from a catastrophic spill, but rather to brain damage from inhalation of volatile fumes, since they breathe just above the water's surface. This was suggested as being especially threatening with less weathered oil on the calm waters and on haulouts early in the spill (Parks Canada 1999).  The seeps at Coal Oil Point provide a constant supply of fresh oil and associated volatile fumes in an area frequented by harbor seal and other pinnipeds.

Recent studies on possible effects of oil on marine mammals have focused on the behavioral effects, thermal effects, and physiological effects due to contact, inhalation, and ingestion of oil.

Fur-Bearing Marine Mammals (MMS.gov/omm/pacific/enviro/calseaotter.htm):  Fur-bearing marine mammals such as sea otters and fur seals are especially vulnerable to the effects of crude oil.

Fur seal pups drown if oil sticks to their flippers or to their bodies, and when it sticks to their fur it reduces or destroys the insulation of their wooly fur (called lanugo) and causes hypothermia. Adult fur seals have blubber and would not suffer from hypothermia if oiled.

Sea otters are the marine mammals most sensitive to the effects of oil contamination since they do not have a layer of blubber to protect them from cold water.  Therefore, they must maintain a layer of warm, dry air in their dense (300,000 hairs per square inch) under-fur to insulate against the cold. Oil compromises this protective coat and even a small oiled area of their fur can cause hypothermia and potentially death of the sea otter.

Gray Whales:  Twice each year, from December to May, the population of the California, or eastern North Pacific, gray whale passes through southern California on its migration between breeding and calving lagoons in Mexico and summer feeding grounds off Alaska. During this journey, most gray whales stay close to the coastline and pass through the Santa Barbara Channel and the Santa Maria Basin—areas where most of southern California's natural oil and natural gas seeps are located.

Studies have shown that cetacean skin is nearly impenetrable to even the highly volatile components in oil. However, the toxic, volatile fractions in fresh crude oils could irritate and damage cetacean soft tissues, such as the mucous membranes of the eyes and airways and the effects could be as severe as death in extreme cases.

Oil could also adhere to the fringed baleen plates that gray whales use to filter their food, blocking the flow of water and interfering with feeding. Gray whales are among the most vulnerable of the baleen whales to effects of ingesting oil-contaminated prey or bottom sediments since they are mainly bottom feeders

Birds: Oil can be especially harmful to our seabirds—particularly diving birds, which must get their nourishment by entering the water.  In the case of species such as the common loon and western grebe, oil interferes with the bird's ability to maintain its body temperature by reducing or destroying the insulation and waterproofing properties of their feathers, which can result in death from hypothermia. They also lose body weight as their metabolism tries to combat low body temperature.  Oiled birds also become easy prey, as they are unable to fly when their feathers are matted from oil.

Chronic, low-level pollution may have a greater effect on bird populations than episodic spills (Camphuysen 1989; Wiens et al. 1996). Also, oil is particularly threatening at locations where seabirds are attracted, such as continental shelf and upwelling areas and areas of other ocean processes that concentrate fish and plankton feed (Berger 1993 b). Therefore, the chronic nature of the continuing release of oil and Coal Oil Point and its location on the Continental Shelf make it a particularly threatening area for seabirds that frequent the Santa Barbara Channel.

When it comes to natural seepage, where crude oil bubbles up from the depths, the most common species to be found oiled and stranded on Malibu beaches is the grebe—Western and  Clark's. One reason is that grebes float together offshore in  "rafts," in the hundreds, even thousands... The State does not help rescue birds that are injured by natural seep... Lampert-Keene-Seastrand Oil Spill Prevention and Response Act that  called for better response and protection of wildlife injured by  petroleum products resulting in the creation of OSPR in the  first place.  In California, the International Bird Rescue Research Center bears the expense of these injured birds. Each year, 75 to 100 birds oiled by natural seeps survive to be admitted into one of two facilities and it is estimated that each bird, its care and feeding, costs an average of $200 each.  (Malibu Surfside News).

Air Quality

Hydrocarbon Seeps are the Largest Source of Air Pollution in Santa Barbara County

The natural gas and oil seeps beneath the Santa Barbara Channel cause gas to escape from the ocean floor and float to the surface like carbonated soda bubbles, releasing methane, a potent greenhouse gas, into the atmosphere. This phenomenon may explain an important piece about the historical global warming cycles and provide new, essential information on current climate changes.

Santa Barbara County's air quality has historically violated both state and federal ozone standards. According to the county's 2007 Clean Air Plan, offshore natural gas and oil seeps is a major source of the county's air pollution and responsible for putting more than 22 tons of reactive organic gases into Santa Barbara's air every day. By comparison, all of the motor vehicle trips in Santa Barbara County produce 18 tons of hydrocarbons each day.

The seep oil that is emitted with the seep gas forms natural oil slicks on the ocean surface that rapidly evaporate and further contribute to air pollution in Santa Barbara County. [Journal of Geophysical Research, Vol. 104, NO. C9, pages 20,703-20,711, September 15, 1999]

The ROG emission rates from the Coal Oil Point seeps are a large source of hydrocarbon pollution in Santa Barbara County (equal to twice the emission rate from all the on-road vehicle traffic in the county in 1990.) In 1977 it was estimated that the Coal Oil Point seep field contains only half of the marine seeps in Santa Barbara County. The official Santa Barbara County Air Pollution Control District estimate of seep ROGs in the entire county was therefore too low by at least a factor of 4. Reaching EPA air quality attainment status in Santa Barbara County may require an effective means of containing or remediating the natural seeps. [Journal of Geophysical Research, Vol. 104, NO. C9, pages 20,703-20,711, September 15, 1999]

An estimate of current seepage for the entire Coal Oil Point offshore area suggests oil seepage is presently on the order of 20,000 - 30,000 liters/day and gas emission on the order of 1-2 x 105 m3/day. This includes emission of methane, a greenhouse gas (2.4-5 x 1010 g/year), and ROGs which are precursors to smog forming ozone (20-20 metric tons/day). This confirms the notion that seepage is a significant natural source of hydrocarbons in the local environment and strengthens the case that such processes may also be important at the global scale  (OCS Study / MMS 2003-2004: Coastal Marine Institute, Marine Science Institute, University of California - Santa Barbara)

Air pollution:  Air pollution caused by the natural seeps is related to the amount of reactive hydrocarbons contained in the seep gas that escapes from the ocean floor and rises to the surface like carbonated soda bubbles. These hydrocarbons, known as reactive organic compounds (ROC), react with sunlight to create smog. Hydrocarbon seeps comprise the largest source of marine methane emissions. [Judd and Hovland, 1992]

Methane Emissions: The addition of methane to the atmosphere can have the following negative impacts (Wikipedia.org/Methane):

• Methane is a relatively potent greenhouse gas with a high global warming potential (i.e., warming effect compared to carbon dioxide).
  
  
• The major source of methane is extraction from geological deposits known as natural gas fields, which includes [offshore] natural gas seeps.

Methane and Global Warming ...

• Methane in the Earth's atmosphere is an important greenhouse gas with a huge global warming potential--1 ton methane emission will have 25 times the impact on temperature of a 1 ton carbon dioxide emission during the following 100 years.
  
  
• Methane has a large effect for a brief period (about 10 years), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20-year time period is far greater (25 times more) than that of carbon dioxide.  
  
  
• Since 1750, the methane concentration has increased by about 150% and it accounts for 20percent of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases.
  
  
• One source estimates the size of the methane hydrate deposits of the oceans at ten trillion tons (10 exagrams). Theories suggest that should global warming cause them to heat up sufficiently, all of this methane could again be suddenly released into the atmosphere. Since methane is twenty-five times stronger than CO2.
  
  
•  At high pressures, such as are found on the  bottom of the ocean, methane forms a solid clathrate with water, known as methane hydrate.  An unknown, but possibly very large quantity, of methane is trapped in this form in ocean sediments.  The sudden release of large volumes of methane from such sediments into the atmosphere has been suggested as a possible cause for rapid global warming events in the earth's distant past, such as the Paleocene-Eocene thermal maximum of 55 million years ago.