Budgeting major elements in pelagic mesocosm studies

• Main Author: Czerny, Jan
• Format: Thesis
• Language: English
• Published: 2013
• Subjects: Ocean acidification; Svalbard
• Online Access: https://oceanrep.geomar.de/id/eprint/23052/; https://oceanrep.geomar.de/id/eprint/23052/1/Diss.%202013%20Czerny,J.pdf

This thesis deals with the optimisation of a marine pelagic mesocosm set-up for quantitative measurement of biogeochemical fluxes of matter within plankton ecosystems. The KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation) mesocosms are cylindrical transparent plastic bags designed to enclose representative samples of the naturally occurring plankton food web. Nine independent, rugged flotation frames support the 20 to 25 m deep watertight bags - depending on the specific experiment set-up - thereby covering the most productive part of the surface water layer. The data presented in this thesis were recorded in the context of an experiment designed to examine the effects of a projected future anthropogenic rise of aquatic CO2 concentrations. This rise was simulated through graded addition of CO2 across nine mesocosms. The objective was to trace natural carbon fluxes from the atmosphere into plankton biomass and via sinking of particles into deeper water layers. Changes in this biological carbon transport caused by increased CO2 concentrations could have far-reaching consequences for the ocean in its function to naturally absorb large parts of the anthropogenic carbon emissions. Measuring the development of full budgets of carbon, nitrogen, phosphorus and silica over time in mesocosms of this size is unprecedented and could provide valuable quantitative data connecting ecology to biogeochemistry. In a short introduction, an outline of the mesocosm approach as well as implementation options with particular regard to pelagic fluxes will be presented on the basis of examples. Three technical publications and a publication discussing measured carbon fluxes and budgets in the Svalbard 2010 ocean acidification study constitute the body of the thesis. The first technical note describes the mesocosm set-up; while the second manuscript deals with the measurement of the enclosed water volume in flexible wall mesocosms. A technique for tracer-based estimates of gas exchange with the atmosphere is described in a ...