Plants
True plants are multicellular and perform
photosynthesis. Photosynthesis takes place
in the chloroplasts and plant cells are
protected by cell walls. Plants take many
different forms, and the floating seeds and
fruit of some can travel along with the
plankton population. For example, a
coconut from a palm tree might float to
another island where it takes root and a
new tree grows.
In the ocean, true plants, such as
cordgrass, are limited to coastal areas and
more shallow water, because they require
light to make food. They get nutrient
through their roots, which grow in to the soil. The most important marine
producers, phytoplankton, are not true plants. The majority of phytoplankton are
considered to be Bacteria and Protists, even though they do photosynthesis.
Animals
When we think of ocean animals, we often think of animals like
those we can track: whales, dolphins, sea turtles, fish, etc.
However, some of the most
important animals in the ocean
are tiny members of the
plankton community. The
large majority of animals on
Earth are unlike humans and
other mammals. These animals
include jellyfish, sea stars,
clams, squid, and many more. These animals are called invertebrates and none of these animals
have a backbone. Most marine invertebrates spend at least a part of their lifetime within the
plankton community. Many marine invertebrates do not move very fast, if at all. To ensure the
survival of their species, invertebrates must find a way to
reproduce, even if they never meet another of their kind.
Corals are one type of invertebrate animal that does not move.
Their reproduction strategy is to release eggs and sperm directly
into the water. When these two cells meet, the egg is fertilized,
and the cell begins to divide. The baby, or larval stage, floats
within the plankton community until it gets too big and settles
on the ocean bottom. This is a way for organisms that move
slowly, or not at all, to colonize new habitats. Other
organisms that you might
not think of as animals, but
are, follow the same
strategy. These include
sponges, clams, and
anemones. Animals have true organelles, including a nucleus.
They feed on other organisms.
Fungi
You are probably familiar with mushrooms
and mold. These are both examples of fungi.
Fungi latch onto other organisms and eat
them by absorbing the food through their cell
wall. For example, you have probably seen a
mushroom growing on a tree. This fungus is
taking nutrition away from the tree through
its cell wall and membrane. Fungi have true
organelles, making them eukaryotic. Fungi
on land and in estuaries are important decomposers. They break down waste and
dead organisms, releasing nutrients back into the ecosystem. In the ocean, fungi can
be very harmful. Some types of
marine fungi make fish very
sick by invading their tissues.
These fungi can remain in the
plankton population until they
latch onto a victim. Most
marine fungi can only be seen
with a microscope.
Protists
Protists are very strange organisms and a
very diverse group. Some protists
photosynthesize; others are heterotrophic.
Some can cause diseases, such as malaria.
Most protists have cell walls, some have
chloroplasts, and all have a nucleus and
cell membrane. Diatoms and
dinoflagellates are important marine
producers. These protists are unicellular.
Other protists are multicellular.
Interestingly, most seaweeds, such as kelp
and rockweed, are not plants at all; they are
multicellular protists.
Bacteria
Bacteria are also known as true bacteria.
These microorganisms are the most
abundant organisms in the ocean.
Cyanobacteria are a type of
photosynthetic bacteria that are thought to
maybe be the first producers on Earth. Not
all bacteria are producers, however. True
bacteria live in most Earth habitats,
including inside our bodies. For example,
there are bacteria that live inside our
intestines that help us to produce
vitamins. These bacteria are heterotrophs
that get their nutrition from your body, but
your cells use the vitamins created to help
complete the body’s processes. Many of the true bacteria are decomposers. They
break down dead organisms and waste and return their nutrients to the Earth
system.
Some of the true bacteria are not as helpful. Some
cause diseases that infect humans and other
organisms. For example, some types of true bacteria
cause strep throat, pneumonia, and ear infections.
True bacteria are unicellular, but they reproduce
quickly so there will be a lot of them, fast, if they are
meeting their needs.
Archaea
Archaea are similar to Bacteria in
that they are single-celled microbes.
Their cells do not have nuclei or
true organelles. They differ from
the true bacteria in biochemical
ways. For example, they have
different enzymes and mechanisms
for building proteins within their
cells.
When they were first identified,
these organisms were also known as they “extreme bacteria” because of the extreme
habitats in which they are found. Archaea live in some of the harshest environments
on Earth, including hot spring, super salty lakes, and places with absolutely no
oxygen. Prior to the discovery of these types of organisms, scientists assumed that
nothing could live under such extreme conditions.
Archaea can be autotrophs or
heterotrophs. The autotrophic
Archaea do not only
photosynthesize, however.
Insteead of using sunlight to
make energy, some of these
unique organisms use
chemicals. The process of
using chemicals to make
energy is called
chemosynthesis.
Archaeans that live and thrive in very salty seas and lakes are called halophiles.
Those that thrive on natural gas (methane) are called methanogens and are found in
the deep ocean. Archaeans found in very hot conditions are called thermophiles.
Most recently, scientists have learned that Archaea are found in almost every Earth
environment and are especially abundant in the ocean.