There are many animals in the ocean ecosystem. Here are some that I remember from the top of my head for right now. They are:
Some of the keystone species are penguins.
Some of the keystone species in salt marshes are:
Fiddler crabs
Ribbed Mussels
and
Harvest mice.
An ecosystem is a place where plants and animals ( maybe humans ) live and animals and plants live in the desert so … 
plants and animals in a healthy ecosystem
The tropical rainforest biome or environment has the most plants and animals in it.
In an ecosystem plants and animals have mutually supportive relationships.
There are changes brought up in animals and plants. It is due to evolution.
An ecosystem is a place where plants and animals ( maybe humans ) live and animals and plants live in the desert so … 
This answer is not very simple. You see there really are no exotic animals in the ocean ecosystem. Mabye a couple sharks and all.
Show a ecosystem diagrams about animals rain forest rivers plants?
plankton
by cooperating
animals role in the ecosystem is to produce carbon dioxide(C02) and then the plants breathe the co2 in and produce oxygen that we breathe oxygen=animals breathe in co2 =plants breathe in co2 =animals breathe out oxygen = plants breathe out
Ecosystem.
plants and animals in a healthy ecosystem
How does what influence animals in the ocean?
The tropical rainforest biome or environment has the most plants and animals in it.
In an ecosystem plants and animals have mutually supportive relationships.
So the animals that eat plants can eat plants and won't run out.