Question

casestudy ddt in an aquatic food chain in the 1960s and 1970s, something strange was happening in the estuaries near long island sound, near new york and connecticut. birds of prey, such as ospreys and eagles, that fed on fish in the estuaries had high concentrations of the pesticide ddt in their bodies. but when the water in the estuaries was tested, it had low concentrations of ddt. what accounted for the high levels of ddt in the birds? poisons that dissolve in fat, such as ddt, can become more concentrated as they move up a food - chain in a process called biological magnification. when the pesticide enters the water, algae and bacteria take in the poison. when fish eat the algae and bacteria, the poison dissolves into the fat of the fish rather than diffusing back into the water. most of the poison remains in an animals body once it is eaten. each time a bird feeds on a fish, the bird accumulates more ddt in its fatty tissues. in some estuaries on long island sound, ddt concentrations in fatty tissues of organisms were magnified almost 10 million times from the bottom to the top of the food chain. large concentrations of ddt may kill an organism, weaken its immune system, cause deformities, or impair its ability to reproduce. a high concentration of ddt decreases the thickness and the strength of eggshells of many birds of prey. poisons such as ddt have the greatest effect on organisms at the top of food chains. for example, the osprey shown here would have a greater concentration of ddt in its body than the perch its about to eat. ddt can also weaken the shells of bird eggs. when eggs break too soon, bird embryos die. therefore, the effects of these chemicals cause a huge drop in the population of carnivorous bird species. the u.s. government recognized ddt as an environmental contaminant and in 1972 banned its sale except in emergencies. the aquatic food chains immediately started to recover, and the populations of ospreys and eagles started to grow. food chains are still not free of ddt. ddt is still legal in some countries where, for example, it is sometimes used in large quantities to eliminate mosquitoes that carry the disease malaria. 22. what is the impact of ddt on the environment? 23. even though ddt is harmful to the environment, why is it still used in some countries?

Explanation:

DDT accumulates in food - chains through biological magnification. It can kill organisms, weaken immune systems, cause deformities, impair reproduction, and thin bird egg - shells. In some countries, it's used to control malaria - carrying mosquitoes despite its environmental harm.

Answer:

DDT has several negative environmental impacts. It accumulates in organisms through biological magnification in food - chains. High concentrations can kill organisms, weaken their immune systems, cause deformities, and impair their ability to reproduce. It also weakens the shells of bird eggs, leading to a drop in the population of carnivorous bird species. However, it is still used in some countries to eliminate mosquitoes that carry malaria.