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Home >> Marine Life >> Aquatic Food Webs
Aquatic Food Webs
Resources
Multimedia
Chemosynthetic Food Web Interactive
Census of Marine Life Biodiversity
Get to Know Your Seafood­ video
Lessons and Activities
A Food Web Mystery
The Game of Life
Chemical Energy and Food Chains Unit
Estuary Food Pyramid
Real World Data
Global Science Investigator: Ocean Color
Tagging of Pacific Predators
Fish Watch: US Seafood Facts
Background Information
Interactive Chesapeake Bay Food Web
Tiny Krill: Giants in a Marine Food Chain
Phytoplankton: The Base of the Food Web
Phytoplankton
Plankton: Why are they Important?
Big fish eat little fish; that's how the food cycle works. Of course,
there’s more to it than that. A whirlwind spiral up an aquatic food
chain goes like this: Phytoplankton feed the zooplankton that feed
the small fish and crustaceans that feed the larger fish that feed the even bigger
fish that feed us.
Taking it a little more
slowly and stopping at
each trophic level
(feeding level), we start
with the primary
producers. Microscopic
phytoplankton floating in
the upper layers of the
ocean use the sun’s
energy to
photosynthesize
carbohydrates. These
carbohydrates can be
eaten for energy, and
these plants ­ mostly
diatoms and algae ­ are
the foundation of the
majority of the ocean’s
biological community. In
areas of the ocean where
Phytoplankton is the base of several aquatic food webs.
there is not light, some
Source: NOAA Alaska Fisheries Science Center MESA Project
producers can even
create energy by using the process of chemosynthesis instead of photosynthesis.
Zooplankton—animal planktonic forms—drift through the water grazing on the phytoplankton. These
"grazers" include copepods and larval stages of fish and benthic, or bottom­dwelling, animals that make up
A Biogeochemist Studying Food Webs
the second trophic level. Copepods and other plankton, both animal and plant, nourish filter­feeding
organisms that strain their food directly from the water such as bivalves, tube worms, and sponges. This
third trophic level also includes other organisms which feed on plankton such as amphipods, larval forms of fish and crustaceans, jellies, and many types of small
fish.
Career Profiles
Schools of larger fish create the next trophic level. They feast on the smaller fish, wasting as much as they consume. The uneaten fish parts and waste sink to
the bottom, where it may be eaten by bottom­dwelling carnivores or decomposed by bacteria and ultimately returned to nutrients usable by plants. At higher
trophic levels, these large fish are food for even higher level predators called top predators. Top predators can be birds, reptiles, mammals, or even larger fish
and many are opportunistic feeders. This means that they may eat anywhere within the food chain and sometimes they even eat each other.
In reality, many different food chains interact to form complex food webs. This complexity may help to ensure survival in nature. If one organism in a chain
becomes scarce, another may be able to assume its role. However, some changes in one part of the food web may have effects at various trophic levels, or any
of the feeding levels that energy passes through as it continues through the ecosystem. Humans play an important role as one of the top predators in these food
webs. It is our responsibility to ensure that our fisheries are sustainable and that we are not polluting the ocean with toxins that bio­accumulate in food chains.