The final dry DOM mass was 1.06 g, equivalent to 0.71 g DOM L -1 seawater extracted. DOC accounted for 41 % of the extracted DOM, equivalent to 0.29 g DOC L -1 seawater extracted (24.2 µM SPE-DOC). DOC typically comprises ~ 50 % DOM in humics which are likely to be highly phenolic and aromatic in character, and ~ 45 % in freshwaters, where humics are mixed with the rest of the aquatic DOM pool . The aged, recalcitrant DOM typically found in seawater is thought to be dominated by alicyclic and linear compounds which are rich in carboxylic acids , and the increased abundance of oxygen from carboxyl groups likely decreases the percentage of carbon in marine DOM relative to the terrestrial systems.