Analysing the controls over DOM quality in two contrasting sub polar marine environments

Sammanfattning: In this study, Dissolved Organic Matter (DOM) quality was analysed through its optical properties. Samples from the estuarine waters of the Beagle Channel and oceanic ones of the Burdwood Bank were examined in order to understand how DOM quality was changing. The focus of the study was to determine whether the environmental variables or the microbial community were the main driver in DOM composition in the two study areas. The DOM composition was different between the two locations. The majority of DOM in the ocean was composed of protein-like, autochthonous material microbially produced while the contribution from the humic-like peaks was very low. A different pattern was observed in the Beagle Channel, where the contribution from the different peaks seemed to be more equally distributed with significant amounts of humic material of terrestrial origin and high amounts of protein material as well. The organic matter in the Beagle Channel was characterised by higher amounts of chromophoric DOM, high molecular weight material and more recalcitrant DOM while in the Burdwood Bank, DOM was more labile and bioavailable. Statistical analysis showed that both the physical conditions of the water column as well as the composition of the microbial community were influencing the quality of DOM. The variable importance in projection (VIP) scores revealed that in the Burdwood Bank the microbial community had greater influence on the DOM composition while the environmental variables were the main driver in the Beagle Channel. This study allowed the characterisation of DOM in these two environments and gave better understanding of the different controls.