(Table 1) Concentration of iron, DIP and silicic acid in water samples taken during Nathaniel B. Palmer cruises NBP06-01 and NBP06-08 (CORSACS I+II), Ross Sea

The Ross Sea polynya is among the most productive regions in the Southern Ocean and may constitute a significant oceanic CO2 sink. Based on results from several field studies, this region has been considered seasonally iron limited, whereby a "winter reserve" of dissolved iron (dFe) is progressively depleted during the growing season to low concentrations (~0.1 nM) that limit phytoplankton growth in the austral summer (December-February). Here we report new iron data for the Ross Sea polynya during austral summer 2005-2006 (27 December-22 January) and the following austral spring 2006 (16 November-3 December). The summer 2005-2006 data show generally low dFe concentrations in polynya surface waters (0.10 ± 0.05 nM in upper 40 m, n = 175), consistent with previous observations. Surprisingly, our spring 2006 data reveal similar low surface dFe concentrations in the polynya (0.06 ± 0.04 nM in upper 40 m, n = 69), in association with relatively high rates of primary production (~170-260 mmol C/m**2/d). These results indicate that the winter reserve dFe may be consumed relatively early in the growing season, such that polynya surface waters can become "iron limited" as early as November; i.e., the seasonal depletion of dFe is not necessarily gradual. Satellite observations reveal significant biomass accumulation in the polynya during summer 2006-2007, implying significant sources of "new" dFe to surface waters during this period. Possible sources of this new dFe include episodic vertical exchange, lateral advection, aerosol input, and reductive dissolution of particulate iron.

Phytoplankton biomass, chlorophyll concentration, and variability of lipid content in Calanus euxinus in the Black Sea in June 1991

During field studies relationships between chlorophyll concentrations, phytoplankton biomass (total, individual sizes and species) and level of accumulation of total lipids, wax esters, triacylglycerols, and phospholipids in C. euxinus (copepodites V and females) were studied. These relationships allowed to display not only simple trophic relations between isolated parts of the C. euxinus population and phytoplankton, but also selective role of individual algae species in forming lipid reserves too. Besides it was found that geographical variability of chlorophyll concentration and phytoplankton biomass correlates closely only with those lipid fractions (wax esters and phospholipids) of C. euxinus, which accumulated and kept in a body for a fairly long time. No correlation was found between phytoplankton and for rapidly metabolized triacylglycerols, which have to be utilized within few hours.

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.