Marine Water Quality

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Marine Water Quality


Marine water quality refers to the presence or absence of any number of pollutants in ocean waters. Some of the more important pollutants include oil, sedimentation, sewage, nutrients, heavy metals, and thermal pollution. Water quality monitoring relies on taking a suite of measurements of ocean water. These include temperature, salinity, density, light transmission, the concentration of dissolved oxygen, and the concentration of chlorophyll (an indicator of the amount of phytoplankton in the water). Water samples are analyzed in the laboratory for the presence and concentration of various forms of bacteria, chlorophyll, phaeopigment (an indicator of the amount of dead phytoplankton in the water), nitrate, nitrite, ammonium, orthophosphate, and silicate. Significant legislation has been enacted to improve marine water quality such as the Clean Water Act, the Water Quality Act, and the Ocean Dumping Act. Several non-profit organizations also monitor ocean water quality and educate the public on marine water quality issues.

Historical Background and Scientific Foundations

Human activities influence water quality in numerous ways and as a result the concept of water quality has emerged, both as a scientific term and as a term that can be used for legislation of environmental policy. Water quality in the marine environment has a different emphasis than water quality in the freshwater environment where one of the concerns has to do with the quality of drinking water. In the marine environment, water quality is most often tied to the presence or absence of pollutants. Pollutants are substances or energy that affect any component of the ecosystem, be they chemical, biological, or physical substances. Some of the more influential pollutants in marine waters are oil, sediments, sewage, nutrients, heavy metals, and thermal pollution.

Oil seeps naturally into the ocean, however the amount of oil that reaches the ocean has well exceeded natural concentrations. As early as 1970, oceanographic ecologists noted that they could rarely pull a net through the surface of the ocean without collecting some form of tar or oil. About one-quarter of a percent of the oil produced each year, or about 6 million metric tons of oil, ends up in the ocean. A significant amount of oil input results from shipping oil from one place to another. Another important input is runoff from urban streets and sewers. The presence of oil in marine waters severely degrades water quality by clogging an animal’s feeding-structures, killing larvae, and blocking available sunlight for photosynthesis.

Sediments are small particles of soil or sand that enter the ocean because of erosion. Erosion occurs because of natural weathering of rocks, and human activities often exacerbate erosion. Deforestation and overgrazing of range land can expose soils that get washed into the ocean. Construction generates sediments that also contribute to sedimentation. When sediments enter the water they absorb light, reducing the amount of photosynthesis that plants can perform. Because plants are the base of the food web in most marine systems, sedimentation has an effect on the overall ecosystem. Sediments can also cover the delicate tentacles of sessile species, disrupting or destroying their ability to filter food out of the water. This is of particular significance for coral reefs, which are often near shore in places where significant construction for recreation occurs. Sediments can also act as vehicles for other forms of marine pollution: toxic compounds and disease-causing agents.

Sewage is human waste along with water, food, detergents, and other material that people wash down drains. Sewage treatment facilities usually separate the liquid portion of sewage from the solid portion and then


EUTROPHICATION: The process whereby a body of water becomes rich in dissolved nutrients through natural or man-made processes. This often results in a deficiency of dissolved oxygen, producing an environment that favors plant over animal life.

FOOD WEB: An interconnected set of all the food chains in the same ecosystem.

SESSILE: Any animal that is rooted to one place. Barnacles, for example, have a mobile larval stage of life and a sessile adult stage of life.

THERMAL POLLUTION: Industrial discharge of heated water into a river or lake, creating a rise in temperature that is injurious to aquatic life.

treat the components to remove harmful organisms. However, when heavy rains overwhelm sewer systems, raw sewage can enter the ocean. Disease-causing organisms can then be released into ocean water. In these cases, beachgoers and swimmers run the risk of becoming infected with bacteria or viruses that have contaminated the water. Sewage also releases heavy metals as well as organic and inorganic nutrients into ocean waters.

The addition of nutrients containing nitrogen and phosphorus to ocean waters can result in a condition known as eutrophication. Nutrients most often enter the ocean as runoff from agricultural land and through sewage. In eutrophic waters, the additional nutrients act as fertilizer stimulating the growth of phytoplankton (microscopic ocean plants). This often allows a single species, and in some cases a harmful species, to overgrow the rest of the phytoplankton community. In the wake of the outburst of growth, bacteria on the decaying phytoplankton coupled with cellular respiration of phytoplankton at night deplete the water of dissolved oxygen. When the oxygen concentrations in water decrease, aquatic animals, which rely on dissolved oxygen for respiration, can become stressed or die.

Heavy metals often enter the ocean through industrial pollution and in residues from burning fossil fuels. The most dangerous to the ecosystem are mercury and lead, which lead to neurological disorders in both humans and other animals. Human activity contributes about 5 times as much mercury and about 17 times as much lead to ocean waters, as do natural sources. In addition, copper, which is extremely toxic to marine invertebrates, has had negative impacts on numerous benthic communities.

Thermal pollution occurs when heated water that is produced by industry is released into the ocean. Many electrical power plants use seawater to produce steam and to cool moving parts. The water returned to the ocean is significantly warmer than ambient water. When this occurs, the organisms that usually live in an environment are unable to grow and reproduce optimally. Organisms from more tropical ecosystems take over available habitats. This changes the ecosystem dynamics in the region.

In order to measure water quality, ocean scientists use sampling equipment that measures some basic parameters of the water. The equipment may consist of a moored instrument that takes water quality measurements continuously. These instruments can also be lowered from the surface to the bottom of the ocean, giving a sense of how the water quality changes spatially. Some of the typical measurements made by these types of instruments include temperature, salinity, density, light transmission, the concentration of dissolved oxygen, and the concentration of chlorophyll (a proxy for the amount of phytoplankton in the water). In other cases, water samples are taken and analyzed in a laboratory. Often laboratory samples are measured for the presence and concentration of various forms of bacteria, chlorophyll, phaeopigment (a proxy for the amount of dead phytoplankton in the water), nitrate, nitrite, ammonium, orthophosphate, and silicate. Another measurement known as Secchi disk depth is an assessment of the particulate material such as sediments, phytoplankton, and bacteria in the water.

Temperature, salinity, and density are basic oceanographic measurements that determine what types of marine animals and plants can easily grow in a particular location. Dissolved oxygen helps scientists determine if the water has become eutrophic. Light transmission tells scientists how far light can penetrate into the water and how deep in the water phytoplankton are able to perform photosynthesis. Chlorophyll and phaeopigment measure the amount of living and dead plant material suspended in the water, respectively. The concentration of different types of bacteria are often measured in water samples and may include total coliform, fecal coliform, fecal strep, Enterococcus, and Clostridia. All of these bacteria are found in the gastrointestinal tract of humans. These bacteria are not necessarily harmful in and of themselves, but may indicate the presence of disease-causing organisms such as the microorganisms that cause hepatitis, dysentery, and cholera.

Impacts and Issues

Public awareness that water quality is affected by dumping refuse into the water has influenced policy for more than a century. In 1899, the United States passed the Refuse Act, which was intended to reduce dumping pollution into public waterways. Since then numerous laws have been passed that attempt to impact water quality. The Clean Water Act of 1977 was initially passed as the Water Pollution Control Act in 1972 and was amended in 1981 and 1987. This act regulates the maximum quantity of pollutants that can be discharged into the ocean from point sources such as factories and sewage treatment plants. The Clean Water Act has had reasonable success at improving water quality. The Water Quality Act of 1987 has provisions to limit pollution from non-point sources, such as agricultural and urban runoff, however these forms of pollution are much more difficult to regulate. In 1991, the Ocean Dumping Ban Act was passed. This act forbids dumping sewage sludge and industrial waste into the ocean.

On a state level, many regions have additional regulations that mandate both the quantity of pollutants released into ocean water and the type of monitoring required to protect visitors to beaches. California has regulations that require local officials to monitor ocean water quality at highly trafficked beaches. These beaches are tested for total coliform bacteria, fecal coliform bacteria, and Enterococcus every week between April and October. A 1996 epidemiology study at the University of Southern California showed that when concentrations of these bacterial indicators are high, the probability that people entering the water will contract stomach flu, upper respiratory infections, and major skin rashes increases greatly. In addition, local law mandates that warning signs must be placed on beaches to indicate when water quality standards are not met.

In response to degraded water quality on popular beaches, several non-profit organizations have developed programs that perform independent water quality monitoring and provide public education and advocacy. In Southern California, the environmental group “Heal the Bay” posts weekly and monthly report cards of water quality at local beaches. The Surfrider Foundation has raised awareness of ocean water quality issues throughout the United States. They have lobbied state and local governments to improve and increase the frequency of water quality monitoring and have established water quality monitoring programs in many communities.

Primary Source Connection

Marine debris is a recurring problem and poses a grave threat to the pristine marine environment. It is a considerable hazard to marine life and is a constant danger for marine navigation.

Disasters like shipwrecks, oil tanker accidents, and offshore oil rig fires contribute to this problem, as does the disposal of urban garbage into oceans, dumping of waste oil by passing ships, commercial coastal and off-shore entertainment, and deep-sea industrial and nuclear waste dumps.

Expanding oil and gas exploration activities into deeper seas are a serious threat to the marine environment. Over a prolonged period, accumulated debris fouls the seas and kills marine life. Marine debris, which is also a growing problem for fishing communities and shipping, causes a loss in fishing harvest, a vital source of sustenance for many fishing communities. Vessels damaged by marine debris collisions can cost a shipping company a fortune to repair.

To mitigate this danger and damage to the environment, Congress passed the Marine Debris Research Prevention and Reduction Act that was signed into law on December 22, 2006.



(a) FINDINGS. The Congress makes the following findings:

  1. The oceans, which comprise nearly three quarters of Earth’s surface, are an important source of food and provide a wealth of other natural products that are important to the economy of the United States and the world.
  2. Ocean and coastal areas are regions of remarkably high biological productivity, are of considerable importance for a variety of recreational and commercial activities, and provide a vital means of transportation.
  3. Ocean and coastal resources are limited and susceptible to change as a direct and indirect result of human activities, and such changes can impact the ability of the ocean to provide the benefits upon which the Nation depends.
  4. Marine debris, including plastics, derelict fishing gear, and a wide variety of other objects, has a harmful and persistent effect on marine flora and fauna and can have adverse impacts on human health.
  5. Marine debris is also a hazard to navigation, putting mariners and rescuers, their vessels, and consequently the marine environment at risk, and can cause economic loss due to entanglement of vessel systems.
  6. Modern plastic materials persist for decades in the marine environment and therefore pose the greatest potential for long-term damage to the marine environment.
  7. Insufficient knowledge and data on the source, movement, and effects of plastics and other marine debris in marine ecosystems has hampered efforts to develop effective approaches for addressing marine debris.
  8. Lack of resources, inadequate attention to this issue, and poor coordination at the Federal level has undermined the development and implementation of a Federal program to address marine debris, both domestically and internationally.

(b) PURPOSES. The purposes of this Act are:

  1. to establish programs within the National Oceanic and Atmospheric Administration and the United States Coast Guard to help identify, determine sources of, assess, reduce, and prevent marine debris and its adverse impacts on the marine environment and navigation safety, in coordination with other Federal and non-Federal entities;
  2. to re-establish the Inter-agency Marine Debris Coordinating Committee to ensure a coordinated government response across Federal agencies;
  3. to develop a Federal information clearinghouse to enable researchers to study the sources, scale and impact of marine debris more efficiently; and
  4. to take appropriate action in the international community to prevent marine debris and reduce concentrations of existing debris on a global scale.


(a) ESTABLISHMENT OF PROGRAM—There is established, within the National Oceanic and Atmospheric Administration, a Marine Debris Prevention and Removal Program to reduce and prevent the occurrence and adverse impacts of marine debris on the marine environment and navigation safety.

(b) PROGRAM COMPONENTS—Through the Marine Debris Prevention and Removal Program, the Under Secretary for Oceans and Atmosphere (Under Secretary) shall carry out the following activities:

(1) MAPPING, IDENTIFICATION, IMPACT ASSESSMENT, REMOVAL, AND PREVENTION—The Under Secretary shall, in consultation with relevant Federal agencies, undertake marine debris mapping, identification, impact assessment, prevention, and removal efforts, with a focus on marine debris posing a threat to living marine resources (particularly endangered or protected species) and navigation safety, including—

  1. the establishment of a process, building on existing information sources maintained by Federal agencies such as the Environmental Protection Agency and the Coast Guard, for cataloguing and maintaining an inventory of marine debris and its impacts found in the United States navigable waters and the United States exclusive economic zone, including location, material, size, age, and origin, and impacts on habitat, living marine resources, human health, and navigation safety;
  2. measures to identify the origin, location, and projected movement of marine debris within the United States navigable waters, the United States exclusive economic zone, and the high seas, including the use of oceanographic, atmospheric, satellite, and remote sensing data; and
  3. development and implementation of strategies, methods, priorities, and a plan for preventing and removing marine debris from United States navigable waters and within the United States exclusive economic zone, including development of local or regional protocols for removal of derelict fishing gear.

(2) REDUCING AND PREVENTING LOSS OF GEAR—The Under Secretary shall improve efforts and actively seek to prevent and reduce fishing gear losses, as well as to reduce adverse impacts of such gear on living marine resources and navigation safety, including—

  1. research and development of alternatives to gear posing threats to the marine environment, and methods for marking gear used in specific fisheries to enhance the tracking, recovery, and identification of lost and discarded gear; and
  2. development of voluntary or mandatory measures to reduce the loss and discard of fishing gear, and to aid its recovery, such as incentive programs, reporting loss and recovery of gear, observer programs, toll-free reporting hotlines, computer-based notification forms, and providing adequate and free disposal receptacles at ports.

(3) OUTREACH—The Under Secretary shall undertake outreach and education of the public and other stakeholders, such as the fishing industry, fishing gear manufacturers, and other marine-dependent industries, on sources of marine debris, threats associated with marine debris and approaches to identify, determine sources of, assess, reduce, and prevent marine debris and its adverse impacts on the marine environment and navigational safety. Including outreach and education activities through public-private initiatives. The Under Secretary shall coordinate outreach and education activities under this paragraph with any outreach programs conducted under section 2204 of the Marine Plastic Pollution Research and Control Act of 1987 (33 U.S.C. 1915).

(c) Grants—

(1) IN GENERAL—The Under Secretary shall provide financial assistance, in the form of grants, through the Marine Debris Prevention and Removal Program for projects to accomplish the purposes of this Act.

(2) 50 percent matching requirement—

  1. IN GENERAL—Except as provided in subparagraph (B), Federal funds for any project under this section may not exceed 50 percent of the total cost of such project. For purposes of this subparagraph, the non-Federal share of project costs may be provided by in-kind contributions and other noncash support.
  2. WAIVER—The Under Secretary may waive all or part of the matching requirement under subparagraph (A) if the Under Secretary determines that no reasonable means are available through which applicants can meet the matching requirement and the probable benefit of such project outweighs the public interest in such matching requirement.

(3) Amounts paid and services rendered under consent—

  1. CONSENT DECREES AND ORDERS—The non-Federal share of the cost of a project carried out under this Act may include money paid pursuant to, or the value of any in-kind service performed under, an administrative order on consent or judicial consent decree that will remove or prevent marine debris.
  2. OTHER DECREES AND ORDERS—The non-Federal share of the cost of a project carried out under this Act may not include any money paid pursuant to, or the value of any in-kind service performed under, any other administrative order or court order.

(4) ELIGIBILITY—Any natural resource management authority of a State, Federal or other government authority whose activities directly or indirectly affect research or regulation of marine debris, and any educational or nongovernmental institutions with demonstrated expertise in a field related to marine debris, are eligible to submit to the Under Secretary a marine debris proposal under the grant program.

(5) GRANT CRITERIA AND GUIDELINES—Within 180 days after the date of enactment of this Act, the Under Secretary shall promulgate necessary guidelines for implementation of the grant program, including development of criteria and priorities for grants. Such priorities may include proposals that would reduce new sources of marine debris and provide additional benefits to the public, such as recycling of marine debris or use of biodegradable materials. In developing those guidelines, the Under Secretary shall consult with:—

  1. the Interagency Marine Debris Committee;
  2. regional fishery management councils established under the Magnuson-Stevens Fishery Conservation and Management Act (16 U.S.C. 1801 et seq.);
  3. State, regional, and local governmental entities with marine debris experience;
  4. marine-dependent industries; and
  5. non-governmental organizations involved in marine debris research, prevention, or removal activities.

(6) PROJECT REVIEW AND APPROVAL—The Under Secretary shall review each marine debris project proposal to determine if it meets the grant criteria and supports the goals of the Act. Not later than 120 days after receiving a project proposal under this section, the Under Secretary shall:—

  1. provide for external merit-based peer review of the proposal;
  2. after considering any written comments and recommendations based on the review, approve or disapprove the proposal; and
  3. provide written notification of that approval or disapproval to the person who submitted the roposal.

(7) PROJECT REPORTING—Each grantee under this section shall provide periodic reports as required by the Under Secretary. Each report shall include all information required by the Under Secretary for evaluating the progress and success in meeting its stated goals, and impact on the marine debris problem.


The Commandant of the Coast Guard shall, in cooperation with the Under Secretary, undertake measures to reduce violations of MARPOL Annex V and the Act to Prevent Pollution from Ships (33 U.S.C. 1901 et seq.) with respect to the discard of plastics and other garbage from vessels. The measures shall include—

  1. the development of a strategy to improve monitoring and enforcement of current laws, as well as recommendations for statutory or regulatory changes to improve compliance and for the development of any appropriate amendments to MARPOL;
  2. regulations to address implementation gaps with respect to the requirement of MARPOL Annex V and section 6 of the Act to Prevent Pollution from Ships (33 U.S.C. 1905) that all United States ports and terminals maintain receptacles for disposing of plastics and other garbage, which may include measures to ensure that a sufficient quantity of such facilities exist at all such ports and terminals, requirements for logging the waste received, and for Coast Guard comparison of vessel and port log books to determine compliance;
  3. regulations to close record keeping gaps, which may include requiring fishing vessels under 400 gross tons entering United States ports to maintain records subject to Coast Guard inspection on the disposal of plastics and other garbage, that, at a minimum, include the time, date, type of garbage, quantity, and location of discharge by latitude and longitude or, if discharged on land, the name of the port where such material is offloaded for disposal;
  4. regulations to improve ship-board waste management, which may include expanding to smaller vessels existing requirements to maintain ship-board receptacles and maintain a ship-board waste management plan, taking into account potential economic impacts and technical feasibility;
  5. the development, through outreach to commercial vessel operators and recreational boaters, of a voluntary reporting program, along with the establishment of a central reporting location, for incidents of damage to vessels caused by marine debris, as well as observed violations of existing laws and regulations relating to disposal of plastics and other marine debris; and
  6. a voluntary program encouraging United States flag vessels to inform the Coast Guard of any ports in other countries that lack adequate port reception facilities for garbage.

U.S. Congress


See Also Algal Blooms; Aquatic Ecosystems; Bays and Estuaries; Benthic Ecosystems; Clean Water Act; Coastal Ecosystems; Coastal Zones; Coral Reefs and Corals; Hazardous Waste; Industrial Water Use; Marine Ecosystems; Nonpoint-Source Pollution; Oceans and Coastlines; Oil Pollution Acts; Real-Time Monitoring and Reporting; Runoff; Toxic Waste; Wastewater Treatment Technologies; Water Pollution



Garrison, Tom. Oceanography: An Invitation to Marine Science, 5th ed. Stamford, CT: Thompson/Brooks Cole, 2004.

Raven, Peter H., Linda R. Berg, and George B. Johnson. Environment. Hoboken, NJ: Wiley, 2002.

Web Sites

Environmental Science and Technology Online. “Marine Waters.” January 19, 2005. (accessed February 28, 2008).

Heal the Bay. “Beach Report Card.” January 16, 2007. (accessed February 28, 2008).

Los Angeles County Department of Public Health. “State Ocean Water Quality Standards.” (accessed February 28, 2008).

Surfrider Foundation. “Water Quality.” (accessed February 28, 2008).

U.S. Congress. “Marine Debris Research Prevention and Reduction Act,” February 10, 2005. (accessed April 10, 2008).

Washington State Department of Ecology. “Marine Waters.” (accessed February 28, 2008).

Juli Berwald

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Marine Water Quality

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