1. Mercury in the environment: Mercury enters the environment from natural sources, such as volcanic activity and erosion of rocks, as well as from human activities like industrial emissions and coal burning.
2. Mercury in water: Mercury can be deposited into water bodies through atmospheric deposition, runoff from contaminated land, and industrial discharges. It exists in different chemical forms, including elemental mercury, inorganic mercury salts, and organic mercury compounds like methylmercury.
3. Phytoplankton and algae uptake: Phytoplankton and algae absorb and accumulate mercury from water. As primary producers, they form the base of the aquatic food chain.
4. Zooplankton consumption: Zooplankton feed on phytoplankton and algae, concentrating the mercury present in their prey.
5. Small fish consumption: Small fish consume zooplankton and accumulate higher levels of mercury.
6. Large fish consumption: Larger fish, such as tuna, swordfish, and shark, prey on smaller fish and accumulate even higher levels of mercury.
7. Biomagnification: As mercury moves up the food chain, its concentration becomes magnified at each trophic level. This is because predators consume and retain the mercury present in their prey.
8. Long lifespan and slow excretion: Some fish species, such as tuna and shark, have relatively long lifespans and slow metabolic rates, allowing for a longer period of mercury accumulation and a reduced rate of excretion.
9. Human consumption: When humans consume fish that contain accumulated mercury, it enters the human body. Mercury can have adverse effects on the nervous system, kidneys, liver, and developing fetus.
Therefore, mercury can become concentrated and magnified as it moves through the food chain, resulting in higher levels of mercury in certain fish species and potential health risks for humans who consume them regularly.