Artificial Reefs

man-made artificial reef structure; Photo by Ron Lukens

It has historically been known that certain species of fish are found around man-made items that were either accidentally or purposefully placed in the marine environment. Ship wrecks have a long history of supporting fishing activities for species of marine fish known as reef fish. These include the snappers and groupers, economically valuable species. So what can be done when there are no naturally occurring hard bottom features in areas like the northern Gulf of Mexico, for example, typified by flat, gently sloping mud-silt-sand bottom? Build artificial reefs. Artificial reefs are just what the name implies, man-made materials placed in the marine environment for the purpose of altering the habitat to encourage the development of hard-bottom communities.

Coastal communities have been building artificial reefs for decades, generally in an effort to stimulate increased fishing and diving to the benefit of residents and tourists alike, at the same time stimulating the local economies. The practice of building artificial reefs has evolved from using inappropriate scrap material, such as car bodies and white goods (washing machines, etc.) to using manufactured structures especially designed for use as artificial reefs. Regulatory agencies caution that artificial reefs should be developed in a responsible manner, consistent with fisheries management programs regulating reef fish species.

Marine Habitats

Sea grass - Courtesy of Paige Gill Rocky Shore - Courtesy of the UN Atlas of the Oceans Coral - Courtesy of the Office of Naval Research Beach - Courtesy of the Office of Naval Research
Vent - Courtesy of the Office of Naval Research Mangrove Open Ocean - Courtesy of Pam Fuller Salt Marsh - Courtesy of
Mud Flat - Courtesy of English Nature Kelp Estuary - Courtesy of the South Florida Water Management District Open Ocean - Courtesy of St. Croix EMS

The oceans cover 71% of the world's surface and contain 97% of the world's free water (the other 3% is on land or in the atmosphere) and is responsible for generating 29% of the earth's oxygen.

The average depth of the world's oceans is 4 km; the deepest spot is the Mariana Trench in the Pacific Ocean at 11.7 km.

There are four major oceans of the world: Atlantic, Pacific, Indian, and Arctic. Some consider a fifth ocean - the Southern Ocean or Antarctic Ocean.

There are many types of marine habitats. Habitats are classified using a variety of factors such as vegetation, substrate, depth, salinity, and wave action. Below are some of the habitats found in the oceanic environment. These may be useful key words to use when searching for resources listed below.

  • Beaches
  • Rocky Shores
  • Mudflats
  • Salt Marsh
  • Mangrove Swamp
  • Estuaries
  • Sea grass beds
  • Coral Reefs
  • Kelp Forest
  • Deep Sea
  • Pelagic (Open Ocean)
  • Hydrothermal Vents

Dead Zones

Dead zones are defined as areas with severely low dissolved oxygen levels or devoid of dissolved oxygen altogether. Such zones have been noted by scientists worldwide since the 1970s and range in size from a square kilometer to about the size of the State of Massachusetts. Currently, the most publicized dead or hypoxic zone is located in the northern Gulf of Mexico just south and west of Louisiana. It is thought to be driven by the outflow of the Mississippi River, which carries sediments and nutrients from agricultural run-off from upstream in the Midwest. The effect of low to no dissolved oxygen on biota has been studied, and it results in lower reproductive capability to a lack of spawning. Obviously, in areas devoid of dissolved oxygen, living organisms that are mobile enough will attempt to escape. This results in vast expanses where organisms are either dead or gone. How does this affect human activities? The primary impact of the dead zone on human activities is a displacement of fishing activities. Fishers who typically fished the area for shrimp are no longer able to catch shrimp there, and as a consequence are forced to travel to other areas to fish. In a climate where expenses often exceed income, this displacement can make or break a fishing operation.

Can dead zones be fixed? Apparently so. A well-known dead zone in the Black Sea largely disappeared between 1991 and 2001 when fertilizer use was severely curtailed due to economic hardship. As a result of reversing the dead zone, fisheries returned as an economic force in the area. What will it take to reverse the dead zone in the northern Gulf of Mexico? Our agricultural belt is quite active, and it isn't likely that the use of fertilizers will cease in the foreseeable future. We may be able to implement better farming practices, such as the establishment of riparian buffers along the river banks that will absorb fertilizer run-off before it can reach the river. Under any circumstance, it will take considerable political will to implement changes that will begin to diminish the Gulf of Mexico dead zone.

Conferences of Interest

  11th National Conference on Science, Policy and the Environment
1/19/2010 - 1/21/2010
Washington, District of Columbia
United States

Biodiversity Database

You can search NBII Marine data, display, and map results within the OBIS-USA region, which includes all USA territorial waters.

These organism occurrence data are part of the Ocean Biogeographic Information System. They conform to the OBIS data schema (an extension of DarwinCore-II) and consist of scientific name, geographic location, source institution and other associated information.

NBII and OBIS-USA serve as a gateway for data that reside at, and are maintained by provider institutions in the USA region.

The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey
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