Copper and Aquatic Life
Copper Applications in Health & Environment
Oceans, tidal pools, lakes, rivers, and ponds --all bodies of water that sustain life-- have copper present as a vital, naturally occurring element. Its presence as a basic component of the process that spawns the abundant species that swim, scurry, wiggle and wallow in the waters of the world has been established by Nature and confirmed by scientists.
It is, simply stated, indispensable because it is necessary for normal growth in living beings.
"The role of copper in small quantities is essential to marine life," says Dr. Karl D. Shearer, Research Fisheries Biologist with the National Marine Fisheries Service, at the Northwest Fisheries Science Center in Seattle, Washington.
"It is a key component of enzymes, compounds that act as catalysts in the metabolism of organisms," says Dr. A. G. Lewis, an oceanographer and Professor in the Department of Oceanography and Zoology at The University of British Columbia in Vancouver, B. C., Canada. "Because it is an essential metal, an adequate supply is necessary for normal metabolism," he explains
"Copper's main role in the body is through metalloenzymes and enzymes catalyze many different chemical reactions," says Dr. Kathryn Michel, Assistant Professor of Nutrition at the University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania.
Dr. Michel adds that "the body is full of enzymes and any chemical reaction in the body has possibly enzymes associated with it. Copper is a very important component and absolutely essential to the performance of the enzymes"
She explains that "enzymes are critical to the development of bone tissue and the production of red blood cells. A copper deficiency would contribute to anemia."
Put simply, "enzymes won't function without trace minerals such as copper, which means there's no metabolism," says Dr. Shearer, the National Marine Fisheries Services biologist, who has worked extensively in the analysis and development of food for fish. With no metabolism there would be no energy to fuel the vital processes that sustain life in creatures.
Aquatic plants, which play an important role in marine life, are no less reliant on copper. It plays an important role in photosynthesis and respiration. Like marine animal life, plants get copper from copper that is dissolved in the water, copper that is present in other particles or sediment found in the water and copper in their food.
Levels of copper in fresh water and salt water have been found to be generally low. In the United States studies of raw, untreated surface water have shown copper content ranging from 0.001 milligrams per liter to 0.28 milligrams per liter. The mean was 0.015 milligrams per liter. In open oceans, copper levels ranged from 0.1 milligrams per liter to 0.39 milligrams per liter, with an average of 0.8 milligrams per liter.
These figures show how copper is effective in small quantities. Dr. Shearer says that "the normal level of copper in whole fish tissue is one to two parts per million." To measure such tiny amounts requires a spectro photometer, an instrument that gauges matter by zeroing in all the way down to atoms in molecules. Scientists heat animal tissue to extremely high temperatures until atoms begin to emit light. Different atoms produce light at different wavelengths. So "we measure (light) wavelength to get to know what elements are present in the tissue of the fish and we measure the intensity of the light, which tells us the amount present," says Dr. Shearer.
They amount of copper and other trace minerals in the growth and development of fish, crustaceans (shellfish) and mollusks such as oysters and clams may be minute in quantity but enormous in economic terms. Many of these species are part of the renewable foundation of fishing, a vast worldwide activity that helps meet a growing demand for protein.
Commercial and recreational fishing is practiced just about every where in the world, including such land-locked countries as Bolivia, in South America, and Azerbaijan, in Asia. Bolivians have been fishing the waters of Lake Titicaca for centuries, and the valuable caviar industry of the world is centered in Azerbaijan, on the Caspian Sea. The Food and Agriculture Organization (FAO) of the United Nations estimated that in 1997 the world's food fish production reached 90 million tons, an almost threefold increase since 1960. Almost a third of that catch was raised on fish farms in a fast-growing commercial process known as aquaculture. Fish grow under controlled conditions within enclosures and are fed a carefully balanced diet that invariably includes copper.
At Bio-Oregon, in Warrenton, Oregon, a producer of formulated food for fish farms, Dr. Dennis Roley, says that "copper has always been a supplemental trace element." Because copper can be virtually recycled from healthy animal tissue, fish food industries find copper in organic forms such as copper sulfate in the offal of edible fish such as salmon that has already been processed.
By including copper in fish food, fish farmers are replicating what nature does so well in the wild: providing an environment that nurtures life and growth. In this respect marine life is similar to other species.
"The requirements for trace minerals such as copper are pretty steady among vertebrate animals," says Dr. Shearer. Interestingly, he adds, crustaceans, such as shrimp, lobster and crab, are in particularly need of copper because its serves as an oxygen carrier in their blood.
Dr. Lewis, the University of British Columbia oceanographer, notes that "copper concentrations in crustaceans may be elevated compared with other groups since many crustaceans use copper in a blood pigment�"
That is why, if you look closely, blood on an uncooked shrimp looks bluish, a typical color of certain forms of oxidized copper. Copper in marine invertebrates plays the role that among humans is performed by iron, which is present in blood as hemoglobin.
It doesn't take much copper to perform its critical role in marine species. Data supplied by Dr. Shearer shows that Atlantic salmon and Channel catfish require 3 milligrams of copper per kilogram of feed. Rainbow trout and carp make do on 3 milligrams per kilogram of feed.
Although requirements have not been determined for every marine species, scientists do know that copper deficiencies in certain species can result in reduced growth and cataracts, among other symptoms. Conversely, scientists have observed that overly high presence of copper in natural waters, due to pollutants or produced experimentally, may badly damage gills, adversely affect the liver and kidneys of fish or cause some neurological damage."
Scientists are frequently frustrated in their efforts to study more closely the effects of too little or too much copper on aquatic species in the wild because it is unusual to find whole fish that have died slowly as a result of malnutrition. "In the wild animals with deficiencies get quickly eaten or decompose," says Dr. Shearer.
Dr. Lewis, who every year prepares a review of copper in the environment for the International Copper Association, says that copper plays an important role in other aquatic environments, too. It is a key component of marine plant life. It is commonly used to purify and distribute drinking water. It combats the growth of unwanted organisms that foul water intake lines, aquaculture facilities and the hulls of vessels.
Copper's Dual Role in Aquaculture
Copper is essential to the growth and development of aquaculture species. It also plays a frequent role in the supply of water that makes fish farming possible.
To insure healthy development of fish, water has to flow easily in and out of the enclosures were they are raised. Undesirable growths can impair the flow of water by blocking or "fouling" ducts, pipes, grates and other conduits. The reduced flow will result in less life-sustaining oxygen being circulated in the waters.
To keep fish farms operating at an optimal level, operators resort to copper-containing compounds, known as antifouling agents, as a weapon against the growth of organisms that impair the flow of water. When properly used, these agents -copper alloys, metal-containing plastic and copper-containing paints and coatings-create a durable antifouling surface that reduces maintenance and eliminates the need for more hazardous types of coatings.
Also in this Issue:
- Alloy 171 for Electronic Interconnects
- Copper's Role in the Safe Disposal of Radioactive Waste: Copper's Relevant Properties - Part I
- Q & A With Hans-Erhard Reiter of the ADSL Forum
- Copper and Aquatic Life
- Research on Copper Joining Techniques Evaluates New Designs and Brazing Methods