Microscopic Photos of the Deep Ocean Flux
Very small particulates make up the bulk of the sinking flux material. This fine fraction is composed of the carbonate and siliceous skeletal remains of phytoplankton and zooplankton, fecal pellets and other detrital plankton debris, and suspended clays and other lithogenic material. Its composition is revealed by its chemical signature and by microscopy, such as this Scanning Electron Micrograph (SEM) of coccoliths and diatom fragments imbedded in a fecal pellet.
Foraminifera are a group of amoeboid protists that produce an elaborate shell often made of calcium carbonate. Incorporating their surrounding elements into their shells, foraminifera deposited in sediments are extremely useful in paleoceanography, and are used to reconstruct the ocean conditions and climate of the past. Pteropods (Thecosamata), a suborder of pelagic sea-snails, are composed of aragonite, an easily dissolvable form of calcium carbonate. The intricate shells of radiolaria are composed of silicate.
Many gelatinous zooplankton such as Salps and even some of the smaller hunters of the mesopelagic community, the pteropods, utilize feeding webs, which are often a sticky mucus consistency, for concentrating and collecting prey. When these structures become clogged, they can be discarded and rapidly sink to depth, playing an important role in the aggregation and relatively rapid transfer of particles from the surface waters to the depths of the ocean. Large particles (such as pieces of Sargassum from the surface) and biogenic aggregates (such as fecal pellets) also provide a rapid transfer of elements to the deep.
While not a major component of the trap samples, macro-zooplankton can find their way into the samples where they are immediately preserved by the mercuric chloride poisoned seawater brine. These “swimmers” are removed and archived during the processing. The zooplankton and occasional small fish collected in the trap samples represent a snapshot of the surrounding community at that time. The traps often capture reproductive events such as larval “blooms” of midwater species.