Endres, Sonja , Karthäuser, Clarissa and Engel, Anja (2014) Combined effects of temperature and CO2 on organic matter dynamics in the surface microlayer and consequences for air-sea gas exchange. [Poster] In: BIOACID Annual Meeting 2014. , 10-11.09.2014, Kiel, Germany .

Abstract

The extent and abundance of gel particles in the surface microlayer (SML) are suggested to influence gas exchange properties at the ocean surface as well as the formation and emission of cloud condensation nuclei to the overlying atmosphere. Thereby, they play an important role in modelling our future climate. Gel particles may be of polysaccharidic or proteinaceous composition and are therefore referred to as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP). They find their origin in dissolved organic matter (DOM) precursors released by phyto- and bacterioplankton. At the same time, gels represent hotspots for intense microbial activity, which may be an important process implied in the continuous recycling of these particles in the SML.
In order to study the formation and degradation of gel particles as well as their effect on air-sea gas exchange under combined future ocean conditions, an indoor mesocosm experiment was carried out from August to September 2013. Twelve mesocosms were filled with ~1400L of fjord water including the natural plankton community up to mesozooplankton and adjusted to two temperatures (16.5 and 22.5°C) and six pCO2 levels (500 to 2500 µatm CO2 ).
Samples were taken twice per week to analyse DOM (sugars, amino acids, coloured DOM) and gel particles dynamics as well as bacterial biomass production both in the SML and in the underlying bulk water. The extent and abundance of TEP and CSP was analysed microscopically. Simultaneously, gas exchange rates over the sampled SML were quantified using N2O as a tracer gas. N2O is considered to behave similarly to CO2 in the atmosphere and therefore enables estimations concerning the future CO2 uptake in the ocean via air-sea gas exchange. These gas chromatography (GC) measurements were carried out weekly using SML samples from two selected mesocosms.

Actions (login required)

View Item