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The words phytoplankton and
zooplankton come from the ancient
Greek word planktos, which means
”wandering.“ The prefix zoo- comes
from the ancient Greek word for
”living being,“ while the prefix
phyto- comes from the ancient Greek
word for “plant.” This last prefix is
misleading in the sense that
phytoplankton are not plants but
protists. There are no real marine
plants as such. However,
phytoplankton do carry out
photosynthesis, a trait commonly
associated with plants.
trace changes in diatom populations, to determine the age of the sediment,
and even to hypothesize water temperature at the time the diatoms lived.
Marine Animal Life
Many animals rely on phytoplankton for nourishment. The first step in the
food chain occurs when zooplankton eat phytoplankton. Zooplankton are
microscopic animals that drift in ocean water and eat phytoplankton or
smaller zooplankton. Other animals, in turn, eat the zooplankton; species
from small fish and birds to giant whales feed on these tiny animals.
Zooplankton come in many varieties. Some are very small crustaceans
with hard outer shells, such as Daphnia. Other zooplankton are simply the
larvae or immature forms of larger animals, such as squid, crab, or jellyfish.
Zooplankton help maintain balance in ocean environments. Besides
serving as food for other animals in the food chain, they help moderate the
ocean’s salinity by absorbing mineral ions with which they build their hard
body parts, and by returning them back to the water when they die and
decay. Further, wastes from zooplankton fall, promoting the flow of
nutrients and minerals from the surface to deeper parts of the ocean.
The coral is another important marine life form. This tiny sea animal
lives in colonies fastened to rocky sea floors. The word coral can also refer
to the animal’s skeletal remains. Corals live in waters with temperatures
between 18°C and 21°C and at depths no greater than 90 meters—where
sunlight reaches. Since corals do not move, they depend on ocean currents
to bring in part of their food supply.
Marine Biologist
S
ome oceanographers focus their
work on studying the life forms
found in the oceans. Marine
biologists discover and study marine
plants and animals and their
interaction with their environments.
Some may study the population
growth of species in a given area,
while other researchers focus on the
effects of fishing or pollution. Marine
biologists also can be involved in
organizing ocean cleanup efforts or
marine rescue operations for
dolphins, whales, and manatees that
may become stranded on land. One
way marine biologists share their
500
Unit 6 Earth’s Oceans
findings with their peers and the
public is by publishing their
research in scientific journals.
Marine biologists typically have
a bachelor’s degree or higher in
marine biology or a related field
such as biology, zoology, or
ecology. Scuba diving and being
comfortable in the water, on boats,
and in submersible vessels are often
necessary for those seeking a career
in marine biology. Students exploring
a career in marine biology may find it
worthwhile to volunteer or intern at
aquariums or laboratories or aboard
research ships.
Image not available.
Please refer to the
image in the textbook
or in the eEdition CD.
MARINE BIOLOGISTS study all kinds
of marine life. This biologist, equipped
with an underwater notepad and
marker, is observing a manatee.
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Keycode: ES2204