Abstract
Fluorescent dissolved organic matter (FDOM) in open surface waters ( 70%) than for the amino acid-like components ( 200 m), the relationships of C1 and C2 with AOU indicate a higher C1/AOU and C2/AOU ratios of the humic-like substances in the dark ocean than in the surface ocean where a net effect of photobleaching is also detected. C3 (tryptophan-like) and C4 (tyrosine-like) variability was mostly dictated by salinity (S), by means of positive non-linear relationships, suggesting a primary physical control of their distributions at the global surface ocean scale that could be related to the changing evaporation-precipitation regime.
Remarkably, bacterial biomass (BB) only contributed to explain a minor part of the variability of C1 and C4.