Organisms in Increasing Order of Concentration of Heavy Metals in their Body:

d) Phytoplankton

Phytoplankton are microscopic photosynthetic organisms that form the foundation of the aquatic food chain. They are primary producers, converting sunlight and nutrients into energy through the process of photosynthesis. Phytoplankton are at the base of the food chain and are consumed by larger organisms, such as zooplankton and fish.

Phytoplankton generally have low concentrations of heavy metals in their bodies. This is because they are at the beginning of the food chain and directly absorb heavy metals from their surrounding environment, such as water. However, their small size and fast growth rate allow them to quickly excrete or dilute these metals, resulting in low levels of accumulation.

c) Zooplankton

Zooplankton are small, drifting animals that feed on phytoplankton as well as other zooplankton. They are primary consumers in the aquatic food chain and serve as an important food source for many larger organisms, including fish.

Zooplankton can accumulate heavy metals in their bodies through feeding on phytoplankton or through direct absorption from the water. As they are higher up in the food chain compared to phytoplankton, they may have slightly higher concentrations of heavy metals in their bodies.

b) Smelt

Smelt are small, schooling fish that primarily feed on zooplankton. They are secondary consumers in the food chain and are preyed upon by larger fish, birds, and mammals.

Smelt can accumulate heavy metals in their bodies through their diet of zooplankton. Since they are higher up in the food chain compared to zooplankton, they may have higher concentrations of heavy metals in their bodies.

a) Herring Gull

Herring gulls are seabirds that feed on a variety of prey, including fish, invertebrates, and even garbage. They are tertiary consumers in the food chain and are often found in coastal areas.

Herring gulls can accumulate heavy metals in their bodies through their diet of fish and other prey. As they are higher up in the food chain compared to smelt, they may have even higher concentrations of heavy metals in their bodies.

In conclusion, the correct order of organisms in increasing order of concentration of heavy metals in their body is:

Phytoplankton < zooplankton="" />< smelt="" />< herring="" gull="" herring="" />

The concentration of heavy metals in the body of the organisms increases with the increase in trophic level. Since phytoplanktons are present at the lowermost trophic level, the concentration of heavy metals in phytoplanktons will be the minimum, while the concentration of heavy metals in herring gull will be the highest as it is present at the highest trophic level. Hence, the correct order of organisms with increasing levels of heavy metals is Phytoplankton < zooplankton="" />< smelt="" />< lake="" trout="" />< herring="" gull.="" herring="" />