FOOD WEBS FOR MARINE LIVING ORGANISMS
Feeding relationships are often shown as simple food
chains – in reality, these relationships are much more complex, and the term food web more accurately shows the links
between producers, consumers and decomposers.
Trophic Levels:
Organisms in most food webs are commonly divided into trophic levels. These
levels can be shown through a pyramid or web where organisms are grouped by the
role they play in the food web. The first level forms the base of the pyramid
and is made up of producers. The second level is made up of herbivores and
consumers. On average, only 10% of the energy of an organism is transferred to
its consumer. The rest is lost as waste, heat energy and movement energy. As a
result each trophic level supports a smaller number of organisms. It has less
biomass which means a top-level consumer, such as a shark is supported by
millions of primary producers from the base of the food web or trophic
pyramid.
Producers:
Producers are described as
autotrophic, which means they are able to make their own food. Producers in the
marine environment convert energy from the sun into food energy through
photosynthesis. Phytoplankton are the most abundant and widespread producers in the
marine environment. Other producers include seaweeds and sea grasses.
Consumers:
Consumers
are described as heterotrophic, which means they are unable to make their
own food and rely on consuming other organisms or absorbing dissolved organic material in the water column.
Decomposers:
Decomposers
exist on every trophic level. They are mainly bacteria that break down dead organisms. This process
releases nutrients to support the producers as well as the
consumers that feed through absorbing organic material in the water column.
This process is very important and means that even top-level consumers are
contributing to the food web as the decomposers break down their waste or dead
tissue.
