87 12.6 Marine Pollution
Major types of ocean pollution include:
* Petroleum
* Sewage
* Solid Waste
* Heavy metals and toxic chemical compounds.
Critical factors relating to ocean pollution:
*There are many ways these substance end up in the ocean ranging from intentional dumping, acts of ignorance, to impacts of disasters (natural and otherwise).
* The majority of pollutants come from land. According to NOAA studies, about 80 percent of marine pollution comes from sources on land.
* Man-made products become pollution when exposed to natural processes that move them through the natural environment. Materials like paper and metals typically decay, but plastic and glass can survive indefinitely. Plastic bags, nets, and fishing lines can trap, injure, and strangle marine creatures. Small plastic objects are consumed and block digestion. Inks, dyes, metals, and toxins from cigarette butts can poison sea life on all tropic levels.
Pollution and Pollutants
Pollutants comes in many forms and from many sources. The impact of pollutants depends on many factors: chemical properties, concentrations, what they react with, what they can convert into, and where and how they may become concentrated through both physical or biological processes. Some chemicals are purely toxic, poisoning organisms in small concentrations, loss of biomass, interfering with reproduction, growth, neurological and respiration function, and causing organ failure, and death. Some chemical pollutants make it more difficult for water to hold gases (such as O2 and CO2). Solids in silt or clay form can cover benthic animal, clog filter feeders, and block sunlight.
Some chemicals bio-amplify. Biologic amplification involves a toxin that does not metabolize and accumulates in an organism, and possibly increases in concentrations as it moves up the food chain. For example the banned insecticide DDT goes through biologic amplification as it is consumed in a contaminated ecosystem. DDT is an example of a chemical pollutant that goes through biologic amplification as it moves up the food chain (Figure 12.6.1).
|
Tropic Level in Food Chain |
DDT concentration |
| Phytoplankton | 0.000003 ppm. |
| Zooplankton | 0.04 ppm |
| Small fish | 0.5 ppm |
| Large fish | 2.0 ppm |
| Birds | 25 ppm |
Figure 12.6.1. Biologic amplification is illustrated by DDT. Through political action it was finally banned in 1972 by the United States Environmental Protection Agency. DDT is discussed more below.
Point and Non-Point Sources of Pollution
All pollution has a source of origin. Point sources are visibly obvious sources. The U.S. Environmental Protection Agency (EPA) defines point source pollution as “any single identifiable source of pollution from which pollutants are discharged, such as a sewage outfall, a ship, or a smokestack.” Strict laws and regulations implemented in recent decades have helped reduce pollution from point sources in most developed countries (mostly because they are visibly obvious and can be linked directly to an original fiscally-responsible source). However, the major contributions to marine pollution come from non-point sources associated with runoff from land. Some ocean pollution starts as air pollution. Non-point sources include small sources (cars, trucks, boats, septic tanks, chimney smoke), and larger sources including agricultural wastes (pesticides, herbicides, fertilizer, and animal wastes) from farms, ranches, and harvesting forest areas. Runoff from industrial and urban areas (roads, parking lots, roofs), faulty managed industrial operations, and poorly-designed waste-water treatment facilities contribute pollutants and garbage to marine settings.
Pollution, and the secondary effects of pollution (causing harmful bacterial and algal blooms), can be very harmful to both wildlife and humans. About a third of shell-fish growing coastal waters are adversely impacted by pollution. Coastal waters and beaches are often unsafe for swimming after storm runoff.
Environmental Concerns with Petroleum Industry Activities
As discussed in previous chapters, most scientists point to fossil fuel consumption as a primary cause for global warming and associated climate change—a topic of greatest concern for the future fate of humanity and the quality and biodiversity of the world’s physical environments. More discussion related to petroleum pollution is discussed below under Marine Pollution. The burning of fossil fuels (oil, gas, coal) are a primary factor impacting climate change. Although alternative energy sources are gradually reducing the demand for fossil fuels in the United States, the consumption worldwide is still gradually increasing..
Petroleum exploration, production, and consumption are the leading causes of pollution affecting the oceans. Petroleum includes crude oil, refined oil products, oil, gas, and tars (asphalt), petroleum derivatives (plastics, waxes, etc.), and greenhouse gases and toxins released by the production and burning of fossil fuels.
Sources of Carbon Dioxide (CO2) Emissions
Carbon dioxide entering Earth’s atmosphere comes from the oceans, soil, plants, animals and volcanoes. Greenhouse gases and pollution from the consumption of fossil fuels is now considered a major cause of climate change and changes in ocean chemistry detrimental to sea life. Climate change investigations show that although human sources of carbon dioxide are much smaller than natural emissions. However, human-source CO2 emission have been significantly increasing since the Industrial Revolution began in the 19th Century. Human activities are offsetting the balance between “sources” of emissions and “sinks” that remove CO2 from the atmosphere. Currently carbon dioxide emissions from fuel combustion include about 43% from coal, 36% is produced by oil, and 20% from natural gas. Destruction of natural “sinks” on land are cause by deforestation and degradation of organic-rich soils in developing agricultural regions which are also releasing large quantities of CO2 into the atmosphere.
Crude oil is a natural resource. Petroleum (gas, oil, and tar) form naturally in the Earth’s crust and are derived from sedimentary deposits, mostly from the continental margin regions of the world (both ancient and modern settings. Crude oil and gas forms from the slow biological and thermal decay of organic remains and residues buried in sediments. It typically takes many millions of years for organic-rich sediments deposited in coastal swamp regions, continental shelves, or the deep ocean to go through the processes to be converted to petroleum resources. The conversion involves: how much organic matter occurs in sediments, how much heat the sediments are exposed to, and for how long it is exposed. The more time organic matter is exposed to heat, the more it breaks down to by-products of gases, fluids (oil), and heavy carbon-rich residues (tar). Most of these materials remained trapped in sediments, but gas and oil can migrate to underground reservoirs or escape to the surface.
Unrefined crude oil is generally biodegradable. Many microscopic organisms (chiefly bacteria) will consume crude oil, however, refine oil products are generally non-biodegradable and are more toxic to wildlife. Light, volatile components will gradually evaporate. Heavier, carbon-rich residues can take much longer. Crude oil breaks down faster with higher temperatures, so spills in cold-water settings take much longer to break down.
Tar balls are a common feature found on beaches around the world. It must be noted that roughly half of the tar balls found on beaches come from natural sources (oil seeps on the seafloor). The other half comes from human activity (pollution). Natural tar seeps are typically common in oil production regions. For instance, anyone visiting the beaches in and around Santa Barbara, California will note that their shoes will become covered with tar after walk on the beach. Although there is oil drilling and production operations both offshore and onshore in the region, the tar on the local beaches mostly comes from natural sources: seeps on the seafloor.
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