Background on Petroleum
Archived page: © 2001 Environmental Legal Information Systems (ELIS). All rights reserved. The information contained in this site is for demonstration and educational purposes, and while every effort has been made to simulate a potential real response to an oil spill, the storyline is not based on actual events. Developed by Kenneth J. Markowitz for the 2nd International Symposium on Digital Earth, Fredericton, New Brunswick, Canada (June 25, 2001). The external links on this page may no longer be functional.
| Chesapeake Bay Ecosystem |
The Chesapeake Bay has nearly 6,000 miles of shoreline, making it the largest inland body of water on the Atlantic Coast. According to the EPA, the sensitive ecosystem of the Bay is filled with oysters and other shellfish, blue crabs and other crustaceans, and many species of both resident and migratory fish. The Chesapeake Bay area is also a critical nesting and ‘fly through’ area for hundreds of bird species, including bald eagles, herons, and mallard ducks. The region has always been a favored winter residence or stopover for many species of waterfowl on the way south from their summer breeding grounds. The shallow waters and wetlands of the Bay and its temperate climate offer a fertile and diverse environment for waterfowl. Diamond-backed and loggerhead turtles, dolphins, manatees, snakes, and frogs also inhabit the Bay.
The State of the Bay 2000 reports that the health of the Chesapeake Bay in the years 1999 and 2000 rated 28 on a scale from 0 to 100. The number, determined by Chesapeake Bay Foundation scientists, represents an average of health measurements for various indicators in three categories: pollution, habitat, and fish and shellfish (fisheries). Recent positive advances have included improved habitat restoration efforts and a marked improvement in the shad population. The health of the Chesapeake relies on intricate natural systems that filter water and provide habitats that sustain diverse and abundant life. Unfortunately, these advances have been met with trends including declines in the blue crab population, poor water clarity, and high levels of nitrogen pollutants in the water. On June 28th, 2000, the Chesapeake Bay Program adapted a new policy, referred to as Chesapeake 2000: A Watershed Partnership, which will guide the next decade of restoration in the Chesapeake Bay watershed.
Chesapeake Bay Foundation Glossary of Terms .
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Background on Petroleum |
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Petroleum is a complex mixture of hydrocarbons (carbon-hydrogen molecules) and nonhydrocarbons (molecules containing carbon, hydrogen, sulfur, nitrogen, and other elements) that result from the break down of biomass over the past millennia. While all petroleums are generally of natural origin and have low water solubility, the variations in molecular composition can cause individual reserves of crude oil to possess unique physical and chemical properties. These differences are important for predicting the potential environmental impact from oil spills.
Petroleum hydrocarbons are classified into five groups by their molecular composition. The molecular composition is, with some exceptions, related to the toxicity of the compound. However, the toxicity of petroleum in a marine environment is very difficult to assess because of the synergistic and additive effects of the components. The most acutely toxic compounds are simple in their carbon rings and include benzene and naphthalene. These compounds are highly volatile (evaporate rapidly), but are likely to have acutely toxic effects when first released. Larger petroleum compounds, including some carcinogens, are less volatile and therefore more persistent and more likely to have chronic (long-term) effects.
| Petroleum
Impacts on the Marine Environment In the aftermath of an oil spill, marine organisms may be affected by one or more routes of exposure, including ingestion, inhalation, dermal contact, and, potentially, bioconcentration through the food chain. |
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Water birds are most commonly affected by oil spills because they are dependent on the water for food and protection. Waterfowl exposure primarily occurs through fouling of plumage, resulting in a loss of water repellency and buoyancy and decreased insulation. Furthermore, the birds ingest petroleum while attempting to remove it from their feathers resulting in anemia, kidney damage, decreased growth, and decreased egg production and viability. |
Larger mammals are rarely exposed to oil slicks, and have, in fact, been known to alter their routes to avoid the oil. Inhalation of oily water is a recognized problem for marine mammals that affects their circulatory and respiratory systems. Their blubber protects marine mammals, such as whales, from dermal contact, except in sensitive places like the eyes and nostrils. Ingestion can occur through consumption of contaminated food and by grooming to remove petroleum, resulting in kidney failure, destruction of intestinal lining, and neural disorders.
Oil primarily affects fish by decreasing the viability of the eggs and larvae, but has limited effects on the adults. Sensitivity varies with species. Fish have a strong enzyme system that can rapidly metabolize hydrocarbons and remove the toxins from their tissues.
Mollusks, including oysters, clams, and scallops, are not directly effected by oil spills because of their hard shells. However, they have no enzymatic system for ridding their bodies of the oil, and therefore bioaccumulate the toxins, resulting in reduced feeding ability and growth reductions. For crustaceans including as shrimp, crabs, lobsters, and zooplankton, the results are acute and cause high mortality rates. The crustaceans are chronically affected as well.
Note: Petroleum text paraphrased from Chapter 7: “Toxicity of Petroleum” Basic Environmental Toxicology (1994). Eds. L. G. Cockerham and B. S. Shane. Boca Raton, FL: CRC Press.
