Potential impact of DOM accumulation on fCO2 and carbonate ion computations in ocean acidification experiments

Culture and mesocosm experiments are often carried out under high initial nutrient concentrations, yielding high biomass concentrations that in turn often lead to a substantial build-up of DOM. In such experiments, DOM can reach concentrations much higher than typically observed in the open ocean. To the extent that DOM includes organic acids and bases, it will contribute to the alkalinity of the seawater contained in the experimental device. Our analysis suggests that whenever substantial amounts of DOM are produced during the experiment, standard computer programmes used to compute CO2 fugacity can underestimate true fCO2 significantly when the computation is based on AT and CT. Unless the effect of DOM-alkalinity can be accounted for, this might lead to significant errors in the interpretation of the system under consideration with respect to the experimentally applied CO2 perturbation. Errors in the inferred fCO2 can misguide the development of parameterisations used in simulations with global carbon cycle models in future CO2-scenarios. Over determination of the CO2-system in experimental ocean acidification studies is proposed to safeguard against possibly large errors in estimated fCO2.

Biological and chemical oceanographic profiles from the equatorial Atlantic

The volume presents planktological and chemical data collected during cruise No. 51 of RV "Meteor" to the equatorial Atlantic (FGGE '79) from February to June 1979. A standard section along the meridian 22° W across the equator was sampled ten times between 2° S and 3° N. Together with a temperature and salinity profile, concentrations of oxygen, nutrients and chlorophyll a were analyzed in water samples down to a depth of 250 m. Solar radiation and light depths were measured for determination of primary productivity of the euphotic zone according to the simulated in situ method. Zooplankton biomass was estimated in 5 depth intervals down to 300 m by means of a multiple opening and closing net equipped with a mesh size of 100 µm.