Marine Snow

Marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the ocean toward the deep sea, made up of dead organisms, phytoplankton remains, fecal matter, and grains of sand and dust, bound together by natural polymers released by phytoplankton and bacteria and by mucus from zooplankton such as salps and pteropods; the resulting aggregates can grow to several centimeters across over the weeks it takes them to sink. The process, called the biological pump, is a major way that energy and organic carbon are exported from the sunlit surface layer to the dark waters and seafloor below, forming the base of deep-sea mesopelagic and benthic ecosystems and feeding microbial communities along the way. Between about 1 and 40 percent of surface ocean primary production is exported downward as marine snow, though only around 1 percent of it typically reaches the seafloor, the rest being consumed or broken down on the way down.