Chesapeake Bay

Chesapeake Bay is an estuary located in the west coast of the United States. It receives water from over 100,000 streams and rivers and empties in the Atlantic Ocean. It is home to around 350 species of fish, dozens of species of shellfish and crabs, 16 species of underwater grasses. Waterfowl, ospreys, and shorebirds also inhabit nearby areas.

All of these species interact in this ecosystem, and form a very complex food web (made up of many food chains). As explained previously, the food chain begins with a producer, which in this case is the phytoplankton, which is then eaten by a number of first consumers, which are then eaten by other predators.

The main purpose of the food chain is to see how energy is transferred from one organism to another. However, pyramids are ways to obtain more data. They represent graphically how energy, matter, and population are distributed in a system. Two of them are the pyramid of biomass and the pyramid of productivity.

The pyramid of biomass shows the amount of biomass at each trophic level, which is calculated by multiplying the mass of an organism times the amount of organisms. The dry weight of an individual is roughly the same as the energy it contains.

The pyramid of productivity shows the flow of energy over time. Since energy is lost as it moves from 1 trophic level to another, the upper levels are always smaller than the lower ones. Only 10% of the energy in one trophic level is passed on to the next one.

Trophic Levels

A trophic level is a hierarchical position that an organism occupies in an ecosystem. This is based on its source of energy. It is also known as feeding level. Trophic levels are represented through food chains, which show the flow of energy from one organism to another with the sun being the first source of energy.

Let's use as an example a food chain in a kelp forest. Here, the kelp would be the producer, which is eaten by blacksmith fish, who in turn is eaten by otters, who are then eaten by sharks.

The kelp is the producer and occupies the first trophic level. Being an autotroph, it is able to convert the Sun's energy into food for itself, and thus supporting the rest of the food chain.

Blacksmith fish would be the first consumers (herbivores), occupying the second trophic level. Otters are the second consumers (carnivore eating a herbivore), and are placed at the third trophic level. Finally, sharks are third consumers (carnivore eating a carnivore), and occupy the fourth trophic level. If we consider that when the shark dies it remains are broken down by bacteria, they would act as decomposers, placing them at a fifth trophic level.