PEECE II mesocosm experiment: Dynamics of extracellular enzyme activities in seawater under changed atmospheric pCO2, 2011

As part of the PeECE II mesocosm project, we investigated the effects of pCO2 levels on the initial step of heterotrophic carbon cycling in the surface ocean. The activities of microbial extracellular enzymes hydrolyzing 4 polysaccharides were measured during the development of a natural phytoplankton bloom under pCO2 conditions representing glacial (190 µatm) and future (750 µatm) atmospheric pCO2. We observed that (1) chondroitin hydrolysis was variable throughout the pre-, early- and late-bloom phases, (2) fucoidanase activity was measurable only in the glacial mesocosm as the bloom developed, (3) laminarinase activity was low and constant, and (4) xylanase activity declined as the bloom progressed. Concurrent measurements of microbial community composition, using denaturing-gradient gel electrophoresis (DGGE), showed that the 2 mesocosms diverged temporally, and from one another, especially in the late-bloom phase. Enzyme activities correlated with bloom phase and pCO2, suggesting functional as well as compositional changes in microbial communities in the different pCO2 environments. These changes, however, may be a response to temporal changes in the development of phytoplankton communities that differed with the pCO2 environment. We hypothesize that the phytoplankton communities produced dissolved organic carbon (DOC) differing in composition, a hypothesis supported by changing amino acid composition of the DOC, and that enzyme activities responded to changes in substrates. Enzyme activities observed under different pCO2 conditions likely reflect both genetic and population-level responses to changes occurring among multiple components of the microbial loop.

Atmospheric electric measurement in the troposphere and stratosphere on the Atlantic Ocean during 1965 and 1969

One main point of the air electric investigations at the atlantic 1965 and 1969 was the record of the potential gradient in the troposphere with free and captive balloon ascents. The course of the field vs. altitude above the sea differs from that over land. A remarkable enlargement of the field strength occurs at the altitude of the passat inversion. The electric voltage between ionosphere and earth could be obtained by integrating the potential gradient over the altitude. Such computations have been made by balloon ascents simultaneous over the ocean and at Weissenau (South Germany), From 15 simultaneous measurements the average value of the potential of the ionosphere over the ocean is 214 kV and over South Germany 216 kV, that means very close together. Because of the small differences also between the single values it can be concluded that in generally the ionosphere potential has an equal value over these both places at one moment. From the potential of the ionosphere VI, the field strength E0 and the conductivity lamda o, both measured at the sea surface, the columnar resistance R could be derived to 2.4 x 10**17 Ohm x m**2. By correlation of the single values of the ionosphere potential with the potential gradient measured simultaneously at the surface of the sea a linear proportional relationship exists; it follows from this result, that R is nearly constant. The mean value of the air-earth current density over the ocean could be calculated by using the measured values of the small ion density with respect to the electrode effect prooved at the equator station. The current density was only 0.9 x 10**-12 A/m**2, which means, a three and a half times smaller value than estimated by Carnegie and accepted up to now. Therefore it seems to be necessary to correct the former calculations of the global current balance.