Notes # 8 - Energy Flow in Ocean Ecosystems
An organism’s energy role is determined by how it obtains energy and how it interacts with the
other living things in its ecosystem. An organism’s energy role may be that of producer,
consumer, or decomposer.
Producers are organisms that can make or produce their own food. They are the source of all
the food in an ecosystem. In almost all ocean ecosystems phytoplankton are the primary
producers. These organisms contain specialized parts of their cell called chloroplasts, which
convert carbon dioxide and water into oxygen and sugars through a process called
photosynthesis. The chemical equation for this reaction is 6 CO2 + 6 H2O 6 O2 + C6H12O6
In some ocean ecosystems, organisms live where there is no light. One such example is around
deep sea vents on the ocean floor, part of the deep zone. Because there is no light, there can
be no photosynthesis. Instead, bacteria and other single celled organisms produce their own
food using the energy found in the chemicals and minerals coming out of the deep sea vent.
This process is called chemosynthesis.
Consumers are organisms that obtain energy by feeding on other organisms. Some of the
smallest consumers in the ocean are called zooplankton; these tiny one-celled organisms eat
the phytoplankton. Just like in land ecosystems, ocean ecosystems can have herbivores,
carnivores, and omnivores.
Decomposers also play an important role in ocean ecosystems. They break down wastes and
dead organisms and return the raw materials to the environment.
Energy enters most ecosystems as sunlight and is converted to sugars by producers. The
energy is transferred to each organism that eats a producer, and then to organisms that eat the
consumers. The movement of energy can be shown in diagrams called food chains and food
webs. A food chain shows one possible path along which energy can move through an
ecosystem. A food web consists of many overlapping food chains and shows multiple paths.
When you draw food chains and food webs, the arrows always point TOWARDS the organism
that is getting the energy. For example,
Redhead grass  Redhead ducks
NOT
Redhead ducks  Redhead grass