Page 31 - living-ice

PHOTO: Morten Iversen, AWI
Marine snow is food for
benthos
Under the sea ice, oating algae look like dancing snow akes. Above the surface, snow and hail fall towards the earth at different speeds. The same occurs with ma- rine particles beneath the surface. They sink towards the seabed at various speeds, with many algae eaten immediately in the uppermost water layers. These algae constitute a huge food source for zooplankton, sh, birds and whales. The remains sink towards the seabed like snow akes of various sizes. Individual algal cells sink less than one meter per day, but if several algal cells collide and clump together, they sink 10–100 meters per day. In comparison, the excrement of algae-eating zooplankton and krill can sink 100–1000 meters per day.
Sinking particles form a food source for life at greater depths of the ocean. Although half the algae sink beneath the bright ocean surface, just 1–2% reach the sea oor (benthic zone) in the deep ocean and create food for the sea oor organisms. Just as delivery times affect the quality of the food we eat, the quality of the food arriving in the benthic zone is determined by how quickly it sinks. Rapidly sinking particles reach a depth of 4000 meters within four days and are still nutritious food. Slowly sinking particles can take 100–1000 days to reach the seabed. They lose much of their nutritious value along the way. Consequently, the type of animals and plants at the ocean surface and the particles they produce have determine the amount of food that reaches the deep ocean.