Oceans notes
How do ocean organisms get their nutrition?
Producers
Some organisms are photosynthetic. They use energy from the sun to produce their own
food through the process of photosynthesis. Since photosynthesis requires light, these
organisms live either near the surface or in very shallow water.
Photosynthetic organisms are autotrophs (or “self” “feeders”). Some autotrophs have
adapted to dark conditions in the ocean and use heat or chemicals from volcanic vents to
produce their own food. This process is called chemosynthesis.
Consumers
Other organisms cannot synthesize their own food. They must eat other organisms. These
are heterotrophs. They can be herbivores (plant eaters), carnivores (animal eaters) or
omnivores (both).
Decomposers
Some organisms eat dead and decaying material. These are called decomposers. Bacteria
and fungi make up the bulk of organisms in this category.
The Food Web
Most producers in the ocean are microscopic algae and plant-like protists that form a
floating mass called phytoplankton. This mass is found near the surface, where there is
ample sunlight.
Zooplankton are microscopic animals, mostly in larval stages, and animal-like protests.
These feed on phytoplankton and are also found in drifting masses near the surface.
Nekton are macroscopic organisms that live among and feed on the plankton. These
include krill, tiny shrimp-like creatures that are a favorite of smaller fishes and baleen
whales.
In summary a food chain would look like this:
phytoplankton→zooplankton→nekton (ex. Krill)→small animals (ex. Herring)→bigger
animals (squid) →top predators (tuna)