Marine biologists suspect that the threat of acidification is most serious to an animal when it is a small, planktonic larva.
Economist(Dec 01, 2016)
Their nematocysts contain minute poisonous barbs; these they use to spear tiny planktonic prey, which they then stuff into their mouths.
The New Yorker(Apr 18, 2016)
Planktonic organisms are minute, but together they make up 90% of the mass of all of the marine life in the oceans.
BBC(May 21, 2015)