Chemical, isotopic and microbial characterization of dissolved and particulate organic matter in estuarine, coastal and open ocean systems.

摘要

Dissolved and suspended particulate organic carbon (DOC, POC), nitrogen (DON, PON), phosphorus (DOP, POP) and inorganic nutrient distributions and elemental ratios were measured and evaluated for the Atlantic, Southern, and Pacific Oceans. Results indicate that DOC is remineralized during mean deep-water transport from the North Atlantic to the North Pacific. Elemental ratios for both dissolved organic matter (DOM) and particulate organic matter (POM) indicate that organic N is preferentially remineralized compared with organic C, while organic P is preferentialy remineralized relative to both organic C and N. Comparison between the DOM and POM pools further suggests that surface POM may be less refractory than concurrently sampled DOM.; Major compound class compositions of ultrafiltered DOM (UDOM) in the North Atlantic, North Pacific and Chesapeake Bay indicate that the majority of UDOM was comprised mainly of a molecularly-uncharacterized fraction, followed by carbohydrates, proteins and lipids. Δ14C and δ 13C results of UDOM compound classes suggest that UDOM in Bay mouth and surface open ocean waters were similarly dominated by old, marine sources, while UDOM from the freshwater endmember was influenced by much younger terrestrial sources. Results indicate that DOM is comprised of different aged organic fractions and provide evidence for a potential organic “size”-age continuum; from low-molecular weight DOM (oldest) to UDOM (intermediate age) to POM (youngest).; Lipid biomarker results indicate that North Atlantic and Pacific UDOM and POM were relatively more reactive at the surface compared with greater depths, coinciding with elemental C:P and N:P ratios greater than Redfield. Factor analyses suggest that there exists a “lability continuum” spanning from surface ocean POM to riverine and deep ocean UDOM. Terrigenous organic material was found at all Bay sites although autochthonous sources of organic matter were also important.; Dark microbial incubations of DOM from the Pacific Subtropical Front and South Atlantic Bight indicate that open ocean DOM is relatively refractory over short time scales (less than 2 months). Experiments with plankton leachate DOM show that this sub-pool of DOM is relatively labile and is converted to refractory DOM within days. DOP is preferentially remineralized in all experiments compared with DOC or DON.