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What in the Hell is PNS YelloSno™?

Updated: Jan 15

Not too long after we released our flagship product PNS ProBio™ (a live culture of purple non-sulfur bacteria) in 2018, we introduced its companion product PNS YelloSno™ (a food for corals and other filter-feeding invertebrates). While more than a few coral foods had just entered the market around that time, PNS YelloSno is markedly different. Thus, we’ve gotten a lot of inquiries about it over the last couple of years. And still get a lot of questions! Thus, we here present a short article describing the content and suggested use of this unusual product.


For sure, the best way to begin is to explain what marine snow is, how it is formed and where it fits into reef food webs.


Snowball effect

Marine snow is a heterogeneous organic aggregate of mostly biogenic origin. Aggregates form from the colloidal fraction. Usually comprised of particles no larger than 1 nm to a few micrometers, most of the organic matter in marine colloidal fraction is not readily available to grazers. Indeed, while this fraction has a substantially higher total mass than either bacterioplankton or phytoplankton, its miniscule particle sizes make it mostly unavailable potential consumers. Therefore, to become more bioavailable, the colloidal fraction must aggregate.

The remains of dead phytoplankton (e.g. cellulose-based cell walls) and zooplankton (e.g. chitin-based exoskeleton fragments), fecal matter or even inorganic dust can make up the bulk of marine snow. Mucus and other sticky exudates (i.e. extrapolymeric substances(EPS)) secreted by bacteria, algae, corals, etc. help to promote aggregation. Particles and small organisms floating through the water column can become trapped within aggregates. As marine snow aggregates are porous, some particles are able to pass through them. Aggregates grow over time (often >0.5 mm in diameter with porosities>95%).


Trapped in the EPS, particulate organic matter is much more available to grazers than it is when drifting freely. Marine snowflakes begin to accumulate bacteria as particles aggregate to several micrometers in diameter (large enough to feed and reproduce on). It is also at this size that the flakes are large enough to flocculate and begin sinking.