because they help trap oxygen from the atmosphere in the water for animals to breathe, ______ are important to sea life.

3 answers

What are your choices?
i don't have any choices
Since this is not my area of expertise, I searched Google under the key words "trap oxygen in sea" to get this:

http://www.google.com/search?client=safari&rls=en&q=trap+oxygen+in+sea&ie=UTF-8&oe=UTF-8

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.