Evidence for non-selective preservation of organic matter in sinking marine particles

Abstract

The sinking of particulate organic matter from ocean surface waters transports carbon to the ocean interior, where almost all is then recycled. The unrecycled fraction of this organic matter can become buried in ocean sediments, thus sequestering carbon and so influencing atmospheric carbon dioxide concentrations. The processes controlling the extensive biodegradation of sinking particles remain unclear, partly because of the difficulty in resolving the composition of the residual organic matter at depth with existing chromatographic techniques. Here, using solid-state 13C NMR spectroscopy, we characterize the chemical structure of organic carbon in both surface plankton and sinking particulate matter from the Pacific Ocean and the Arabian Sea. We found that minimal changes occur in bulk organic composition, despite extensive (>98%) biodegradation, and that amino-acid-like material predominates throughout the water column in both regions. The compositional similarity between phytoplankton biomass and the small remnant of organic matter reaching the ocean interior indicates that the formation of unusual biochemicals, either by chemical recombination or microbial biosynthesis, is not the main process controlling the preservation of particulate organic carbon within the water column at these two sites. We suggest instead that organic matter might be protected from degradation by the inorganic matrix of sinking particles.

Microbial mediation of benthic biogenic silica dissolution

“…The data show a negative relation, with opal being enriched with increasing water depth, reflecting fast organic matter degradation and slow BSi dissolution during water column transit. It has been hypothesized by Lee et al (2000) and Hedges et al (2001) that mineral ballast (BSi, CaCO 3 , and terrigenous compounds) inhibit carbon mineralization before reaching the sediment surface. Then, the correlation of benthic Si release and O 2 uptake in the dataset could be a result of BSi protecting the cytoplasmic OM from decay, as proposed by Armstrong et al (2002) and Moriceau et al (2009) for sinking particles in the water column.…”

Characterization of methyl sugars, 3-deoxysugars and methyl deoxysugars in marine high molecular weight dissolved organic matter

“…Chromatographic analyses have identified glucosamine and galactosamine in HMWDOM, but at concentrations of ≤ 2% HMWDOC (Aluwihare et al, 1997;. Similar inconsistencies have also been reported for plankton and sinking particulate organic matter (Hedges et al, 2001;.…”

Impact of mineral micropores on transport and fate of organic contaminants: A review

“…It has been observed that silicate and calcium carbonate biominerals and aluminosilicates in marine environment play an important role in protecting organic carbons, such as amino acids and proteins, from hydrolytic enzymes throughout the water column and surface sediments, leading to their non-selective preservation (Hedges et al, 2001;Ingalls et al, 2003;Mayer, 1994a;Ransom et al, 1998;Tosca et al, 2010). Micropores and mesopores in soil minerals have a similar role in the preservation of soil organic carbon (SOC) (Knicker, 2004;Krull et al, 2003;Mayer, 1994b;Mayer et al, 2004).…”