Estimation and Fate of New Production in the Marine Environment

Abstract

The fate of carbon in the ocean determines both the amount of CO_(2) that can be sequestered and the amount of sustainable biomass. Compartmentalization into new and regenerated production allows a first order estimate of carbon available to the local community versus the amount exported. The goal of this project was to study sources and sinks of production in order to test the general hypothesis that new production is underestimated in the marine environment. Specifically we looked at pulsed new nutrients and the effect on the ecosystem, the effect of currents on our measurements and estimates of export (equivalent to new production), and finally development of a new method which will allow in situ determination of new production in the majority of the global ocean.

Specifically, the role of a Pacific herring spawn was investigated as an important stimulant to ecosystem wide carbon and nitrogen cycling in Simpson Bay, Alaska. A consistent pattern was observed each year: a large bloom in June corresponded to the timing of the herring spawn and low nutrients, low phytoplankton diversity, and high POC concentrations; elucidating a previously unidentified pulse of new nutrients to the system.

Estimates of carbon export are affected by the physical environment. The model presented and validated herein is used to improve our understanding of C export by including the effect of horizontal transport. We show that measurements of export to shallow water traps are less impacted by currents than deep traps. Spatial extent of variable primary production necessary to affect deep water traps is greater, as such, over half of the traps analyzed in this study are affected by up-current productivity regimes.

A method to simultaneously quantify the C and N fixing community in the same sample was developed, eliminating many assumptions introduced when using different techniques and incubations. Cultured and environmental samples were successfully hybridized using TSA-FISH. Strong correlations between positively tagged community abundance and ^(14)C/^(15)N measurements are presented. The findings of this work support the general hypothesis that new production is under-accounted for in marine systems.