Biomagnification

Bioaccumulation vs Biomagnification Bioaccumulation: increase in concentration of a pollutant from the environment to the first organism in a food chain Biomagnification: increase in concentration of a pollutant from one link in a food chain to another There are two basic terms we are discussing here. Bioaccumulation refers to how pollutants enter a food chain; biomagnification refers to the tendency of pollutants to concentrate as they move from one trophic level to the next. Here are some definitions of these terms: Bioaccumulation: increase in concentration of a pollutant from the environment to the first organism in a food chain Biomagnification: increase in concentration of a pollutant from one link in a food chain to another We are concerned about these phenomena because together they mean that even small concentrations of chemicals in the environment can find their way into organisms in high enough dosages to cause problems. In order for biomagnification to occur, the pollutant must be: long-lived mobile soluble in fats biologically active If a pollutant is short-lived, it will be broken down before it can become dangerous. If it is not mobile, it will stay in one place and is unlikely to be taken up by organisms. If the pollutant is soluble in water it will be excreted by the organism. Pollutants that dissolve in fats, however, may be retained for a long time. It is traditional to measure the amount of pollutants in fatty tissues of organisms such as fish. In mammals, we often test the milk produced by females, since the milk has a lot of fat in it and because the very young are often more susceptible to damage from toxins (poisons). If a pollutant is not active biologically, it may biomagnify, but we really don't worry about it much, since it probably won't cause any problems.

Why use DDT? Not particularly harmful to humans- therefore could be handled with few negative side effects Very effective at killing insects- used extensively during World War I to kill lice and mosquitos- limited malaria and louse-born diseases among refugees DDT stands for dichloro, diphenyl trichloroethane. It is a chlorinated hydrocarbon, a class of chemicals which often fit the characteristics necessary for biomagnification. DDT has a half-life of 15 years, which means if you use 100 kg of DDT, it will break down as follows: This means that after 100 years, there will still be over a pound of DDT in the environment. If it does bioaccumulate and biomagnify, much of the DDT will be in the bodies of organisms. DDT actually has rather low toxicity to humans (but high toxicity to insects, hence its use as an insecticide). Because it could be safely handled by humans, it was extensively used shortly after its discovery just before WW II. During the war, it was used to reduce mosquito populations and thus control malaria in areas where US troops were fighting (particularly in the tropics). It was also used on civilian populations in Europe, to prevent the spread of lice and the diseases they carried. Refugee populations and those living in destroyed cities would have otherwise faced epidemics of louse-born diseases. After the war, DDT became popular not only to protect humans from insect-borne diseases, but to protect crops as well. As the first of the modern pesticides, it was overused, and soon led to the discovery of the phenomena of insect resistance to pesticides, bioaccumulation, and biomagnification. By the 1960's, global problems with DDT and other pesticides were becoming so pervasive that they began to attract much attention. Credit for sounding the warning about DDT and biomagnification usually goes to the scientist Rachel Carson, who wrote the influential book Silent Spring (1962). The silent spring alluded to in the title describes a world in which all the songbirds have been poisoned. Her book of course was attacked by many with vested interests.

The Problem: Peregrine Falcons Extirpated from much of U.S. locally extinct) from much of U.S. http://www.iowaccess.org/main/news/newsimages/peregrine.jpg

Osprey and Bald Eagles were declining, as well. http://www.state.tn.us/twra/graphics/BLDEAGLE.jpg http://www.state.tn.us/twra/graphics/OSPREY.jpg

Meanwhile, in Borneo: Why were roofs falling on people’s heads? Gecko-eating cats had begun to die, and thriving rats brought plague and typhus The World Health Organization began to parachute cats into Borneo, but what was causing these problems? http://www.herpafauna.com/pics/geckos/a-felinus.jpg

Finding the cause: Roof collapse traced to disappearance of parasitic wasp which had controlled thatch-eating caterpillars. http://www.life.umd.edu/classroom/bsci124/img/parisitoid.jpg

It seemed to be a chain: Wasps disappeared because DDT had been sprayed to kill mosquitos, which carried malaria - number one killer of humans worldwide

Cat Parachuted into Borneo http://www.freewebs.com/an4rkia/DDT.jpg

The data suggested DDT: Measurements of DDT levels seemed to multiply as the compound moved up the food chain: Case study in Long Island Estuary: Water to zooplankton: 800x Zooplankton  to fish #1 = 31x Fish #1 to fish #2 = 1.7x Fish #2 to gull = 4.8x Overall = 202,368x Case study: Long Island Estuary (Figure 22.1 in Cox) In your textbook, Cox reports on a study done in 1967 on Long Island Sound. The levels of DDT in tissues of various animals in the sound showed bioaccumulation factors of 800x, and biomagnification factors up to 31 times. When we look at the whole food chain, the overall magnification is over 200,000x! water to zooplankton: 800x zooplankton to fish #1: 31x fish #1 to fish #2: 1.7x fish #2 to gull: 4.8x overall: 202,368x While DDT isn't particularly lethal (except to insects, and we need many of them around), it has a number of sub-lethal effects. Most prominent is the phenomenon of shell-thinning in birds, particularly carnivorous birds (raptors) - birds that eat other birds, birds that eat carrion (dead animals), and birds that eat fish. Ospreys are one of the raptors that have been adversely affected, as have bald eagles. Other fish-eating water birds have been affected as well. Because of the DDT, the shells are too thin to brood. Many populations have recovered following the banning of DDT in the US, but migratory birds may be exposed to pesticides in other countries. Recently, some studies have shown effects on sex ratios in some species of birds, with the males becoming "feminized", presumably the result of compounds in the environment mimicing the female hormone estrogen.

More evidence against DDT: Sub-Lethal Effects: Eggshells from Peregrines with high DDT levels showed significant thinning http://www.kodak.com/US/images/en/corp/features/birdcam2000/gallery/04_03/13_32__2000_04_03_fullcam2.jpg

How does biomagnification work? DDT, a synthetic molecule, cannot be broken down or excreted – Life doesn't have enzymes that "know" how. Thus, it concentrates as animals higher on the food chain eat more and more food.

Solutions: Ban DDT "Hack out" captive-bred peregrine chicks Build nest platforms for Osprey

How effective were these solutions? Peregrines, Osprey, and Bald Eagles recovered However, Other countries still use DDT DDT isn't the only chemical that biomagnifies!

The problem magnifies: MethylMercury concentrates just like DDT and damages human Nervous Systems A person who eats one meal of lake trout from Lake Michigan will be exposed to more PCBs in one meal than in a lifetime of drinking water from the lake!

The Problem is ongoing: PCBs (polychlorinated biphenyls) PAHs (polynuclear aromatic hydrocarbons) Heavy metals: mercury copper cadmium chromium lead nickel zinc tin TBT (tributyltin) mercury from gold mining cyanide selenium The number of new molecules we introduce into our environment continues to increase. DDT is not the only toxin to biomagnify. All of the following have the potential to biomagnify: Substance Use & Problems Links PCB's polychlorinated biphenyls insulators in transformers plasticizer fire retardant biomagnifies impairs reproduction widespread in aquatic systems as airborne contaminants in sediments in the Mississippi River PAH's polynuclear aromatic hydrocarbons component of petroleum products carcinogenic Heavy metals: mercury copper cadmium chromium lead nickel zinc tin (TBT or tributyltin) mercury from gold mining many from metal processing may affect nervous system may affect reproduction from an interesting student project heavy metals in the Mississippi River - great source! cyanide used in leaching gold used in fishing toxic effects on coral reefs health information proposed gold mine and its effects report of a spill of cyanide selenium concentrated by farming desert soils reproductive failures selenium at a wildlife refuge in Wyoming

The Ultimate Solution? Models are being developed to predict toxicity of new chemicals Pollution control must be intensified: Zero Tolerance in the Great Lakes? Education: Increase awareness so everyone will decrease use and dispose of chemicals properly. Modern pesticides, such as carbamates and organophosphates, are "safer" in that they are not persistent, one of the requirements for biomagnification. They are, however, more toxic, and insects are developing resistance to them. It must be remembered that we use pesticides for more that making pretty produce. Pesticides are sometimes necessary to protect a basic food supply and to protect human health. The concept of integrated pest management, or IPM, has been developed to improve control of pests while decreasing the need for pesticides. IPM uses a variety of methods to control pests. These include biological controls, and cultural practices such as timing planting and harvest to avoid periods of peak activity by pest species, and scouting to determine how big a problem the pests are actually causing (rather than just spraying to prevent a problem that may never arise). Economics are watched closely; pesticides are never used if the cost of the pesticide would exceed the cost of the crops being saved (you'd be amazed at how often people have spent more on pesticides than the crop was worth). IPM relies heavily on information, and the internet is being used extensively.

Laws and Regulations Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 1972 requires registration of pesticides for specific uses London Dumping Convention 1972 ratified by 64 countries bans deliberate discharge of various toxic or other wastes International Convention for the Prevention of Pollution from Ships (MARPOL) 1988 prohibits dumping of plastics at sea ratified by 40 countries

"This we know: The earth does not belong to man; man belongs to the earth. Whatever befalls the earth befalls the sons of the earth. Man did not weave the web of life; he is merely a strand in it. Whatever he does to the web he does to himself." - Chief Seattle

Bibliography… "ToxFAQsTM for DDT, DDE, and DDD," ATSDRIC Information Center Division of Toxicology, Agency for Toxic Substances and Disease Registry, Atlanta, GA, June 11, 2001. <http://www.atsdr.cdc.gov/tfacts35.html> 2/21/02 Mader, Sylvia S. 1996. Biology - 5th Ed. WCB and Cox, G.W. 1997. Conservation Biology - 2nd ed. WCB < http://www.marietta.edu/~biol/102/2bioma95.html> 2/21/02 "Chapter 4: The Great Lakes Today – Concerns" Government of Canada (Toronto, Ontario) and United States Environmental Protection Agency, Great Lakes National Program Office (Chicago, Illinois) The Great Lakes: An Environmental Atlas and Resource Book, Third Edition, 1994, http://www.epa.gov/glnpo/atlas/glat-ch4.html> 2/20/02 "Mercury: In Your Community and the Environment." PUB-CE-239 98 Wisconsin Department of Natural Resources and the Pollution Prevention Partnership; Last Modified: November 29, 1999 Environment Canada : http://www.on.ec.gc.ca/glimr/classroom/millennium/mercury/mystery-e.html "Great Lakes Initiatie," Wisconsin Sea Grant, 2001 http://seagrant.wisc.edu/Communications/Publications/One-pagers/CriticalPollutants.html 2/20/02 Mader, Sylvia S. 1996. Biology - 5th Ed. WCB and Cox, G.W. 1997. Conservation Biology - 2nd ed. WCB retrieved from 1/29/13 http://www.marietta.edu/~biol/102/2bioma95.html