Hi John, Interesting,
It seems pretty certain that Antartica ice, (prehaps all ice) contains many millions of living Microbes. which when they melt in seawater provide the halo of nutriments to the plankton which you mention, and provide food for plant and marine life.
Some of the living Microbes found by the Russians, when drilling down to lake Vostok, include:- Beauveria bassiana,-Archaea,-M.burtonnii,-and a Penicillium bacteria.As well as other yeast and fungi.
http://science.nasa.gov/newhome/headlines/ast12mar98_1.htmAlso more here.
http://www.science.psu.edu/alert/Loveland-Curtze5-2008.htmIt must be difficult to estimate the the particulates of dead life that eventually drop to the sea floor, requiring the investigation of a top marine biologist to bring up a samples of mud?