Concentration of floating biogenic material in convergence zones

Abstract

:Some organisms that live just below the sea surface (the neuston) are known more as a matter of curiosity than as critical players in biogeochemical cycles. The hypothesis of this work is that their existence implies that they receive some food from an upward flux of organic matter. The behavior of these organisms and of the associated organic matter, hereafter mentioned as floating biogenic material (FBM) is explored using a global physicalbiogeochemical coupled model, in which its generation is fixed to 1% of primary production, and decay rate is of the order of one month. The model shows that the distribution of FBM should depart rapidly from that of primary production, and be more sensitive to circulation patterns than to the distribution of primary production. It is trapped in convergence areas, where it reaches concentrations larger by a factor 10 than in divergences, thus enhancing and inverting the contrast between high and low primary productivity areas. Attention is called on the need to better understand the biogeochemical processes in the first meter of the ocean, as they may impact the distribution of food for fishes, as well as the conditions for air-sea exchange and for the interpretation of sea color.

Transparent exopolymer particles: Effects on carbon cycling in the ocean

“…However, studies in various marine systems have reported that large marine snow particles could be retained in surface waters for several days (Stachowitsch et al 1990, Riebesell 1992, Kiørboe et al 1998, and even ascend and lead to the formation of organic-rich surface films at the airsea interface, called "slicks", which are visible at the ocean's surface (Ryan et al 2010, Cunliffe et al 2013, Wurl et al 2016. While this retention pathway has been acknowledged for POM, and a corresponding upward POM flux hypothesized (Tsunogai et al 1980, Obernosterer et al 2005, Dandonneau et al 2008, field measurements to estimate upward POM fluxes were only conducted at great depths (e.g. Smith et al 1989).…”