The Detritus Nitrogen Problem: New Observations and Perspectives from Organic Geochemistry

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Abstract
Studies of the decompositional chemistry of 5 types of estuarine macrophyte detritus were undertaken to examine relations among detrital N, protein and other decompositional products. Protein and N contents of the detritus correlated poorly. Although the total mass of protein in all detritus decreased after 150 days of aging, there was a net increase in the mass of detrital N in some vascular plant detritus. During decomposition, detritus becomes richer in reactive phenolic and carbohydrate groups which may form condensation products with amino acids, yielding precursors to complex nitrogenous humic geopolymers. The existence of a significant positive relation between N accumulation and the production of humic substances suggests that much of the N accumulated during detritus decomposition is non-labile humic N rather than living microbial protein. The process of N enrichment often observed in detritus studies is consistent with the chemical behavior of N during humification. Biological availability of this humic N probably depends upon the extent to which proteinoid subunits are retained in the humic macromolecular structure.