Marine snow

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MARINE SNOW

Marine snow are millimetre to centimetre sized aggregations of smaller particles, mainly phytoplankton and detritus. They occur ubiquitously in the ocean, at times in very high concentrations, and they are supposed to be the main vehicles for vertical material transport in the ocean. They are porous and fragile, and they easily disintegrate to primary particles when sampled by traditional means. They can be collected and visualised, e.g., in the Sea Core Sampler (Kiørboe 2007).

Formation of marine snow

Physical coagulation Marine snow may form by physical coagulation: Turbulence or other processes bring particles to collide. If the particles are "sticky", they may stick together upon collision, and eventually form large aggregates (animation by A. Visser).
Discarded mucus feeding webs Marine snow may also form from discarded mucus feeding webs, e.g., the mucus houses that larvaceans produce. The video shows a feeding larvacean (Oikopleura sp.) and the illumination emphasises the mucus house with its outer and inner filters. The animal itself consists mainly of a small "head" and a long, beating tail, that produces the water current. Large particles are retained on the outer filter, whereas smaller particles are captured by the inner filter and eaten. Because the outer filter clogs eventually, houses are renewed every few hours.
Collaps of discarded mucus feeding webs Initially, the discarded house can be recognised, but after a while it collapses into a rather dense structure with high sinking velocity. The fecal pellets stemming from the larvacean reveals the origin of the marine snow aggregate.