Besides the biology and chemistry departments, perhaps try the labs associated with the medical school at UCLA, and labs in other related fields, such as mathematics and physics. As long as the student can demonstrate commitment and competence in a lab, then not having done research in the field that aligns exactly with one’s interest is not a big disadvantage when applying to graduate schools. Many professors like to include students with diverse academic background in their labs.
Some labs hesitate to take in undergraduate students as researchers because they lack the manpower to mentor the undergraduates in doing research; in fact, some graduate students and post-docs see it as a big time-draining chore to show another newcomer around in the lab. Perhaps ask if he can volunteer to do menial jobs, such as washing glassware or help with cleanup, to get his foot in the door first.
I am not discounting that undergraduate research is helpful, but It is much more important that your son has performed solidly for all the courses required by the marine biology department, when applying to graduate schools, and of course, GRE, if required.