Water Pollution

The correct answer is:

Option 2: Seagull

Explanation:

Biomagnification refers to the increasing concentration of a substance, such as DDT, as it moves up through successive trophic levels of a food chain. This occurs because the substance is not easily metabolized or excreted by organisms, leading to its accumulation in the food web.

Aquatic Food Chain Example:

Phytoplankton (primary producers) absorb DDT from the water.

Small fish consume phytoplankton and accumulate DDT.

Larger fish eat smaller fish, further increasing DDT concentration.

Seagulls, being apex predators, consume large fish and thus have the highest concentration of DDT in their tissues.

This pattern of increasing concentration at higher trophic levels is a classic example of biomagnification.

Why Other Options Are Incorrect:

Option 1: Phytoplankton – As primary producers, they have the lowest concentration of DDT in the food chain.

Option 3: Crab – While they are consumers, they are not at the top of the food chain and thus have lower DDT concentrations.

Option 4: Eel – Eels are higher in the food chain than crabs but still not at the top, so their DDT concentration is lower than that of seagulls.

Therefore, the highest DDT concentration in the aquatic food chain occurs in seagulls, the apex predators.