MEAD: an interdisciplinary study of the marine effects of atmospheric deposition in the Kattegat.

This paper summarises the results of the EU funded MEAD project, an interdisciplinary study of the effects of atmospheric nitrogen deposition on the Kattegat Sea between Denmark and Sweden. The study considers emissions of reactive nitrogen gases, their transport, transformations, deposition and effects on algal growth together with management options to reduce these effects. We conclude that atmospheric deposition is an important source of fixed nitrogen to the region particularly in summer, when nitrogen is the limiting nutrient for phytoplankton growth, and contributes to the overall eutrophication pressures in this region. However, we also conclude that it is unlikely that atmospheric deposition can, on its own, induce algal blooms in this region. A reduction of atmospheric nitrogen loads to this region will require strategies to reduce emissions of ammonia from local agriculture and Europe wide reductions in nitrous oxide emissions.

A novel modeling tool with multi-stressor functionality for organic contaminant transport and fate in the Baltic Sea.

The coupled physical-biogeochemical model BALTSEM, previously used to assess nutrient/carbon cycles and eutrophication in the Baltic Sea, has been expanded to include algorithms for calculations of organic contaminant environmental transport and fate. This novel model version (BALTSEM-POP) is evaluated for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and hexachlorobenzene (HCB) in Baltic Sea surface water and sediment. Modeled dissolved concentrations are usually within a factor of 2-4 of observed concentrations, however with larger deviations for furans. Calculated concentrations in particulate organic matter are less accurate (within factors of 1-700), likely due to errors in estimated pelagic biomass, particulate matter-water partitioning, and large natural variability in field data. Concentrations in sediments are usually predicted within a factor of 6. The good performance of the model illustrates its usefulness for exploration of contaminant fate in response to variations in nutrient input and climatic conditions in the Baltic Sea marine environment.

Asymmetrical effects of increases in hydrostatic pressure on macromolecular movement across the airway mucosa. A study in guinea-pig tracheal tube preparations.

This study employed isolated guinea-pig tracheal tube preparations in order to examine effects of increases in hydrostatic pressure on the movement of macromolecular solutes (fluorescein isothiocyanate-conjugated dextran; FITC-D, MW 70 kD; kept either in serosal or mucosal bathing fluids) across the mucosa. An asymmetry of the mucosal barrier was demonstrated by the finding that under baseline zero-pressure difference conditions luminal entry of serosal FITC-D was greater than serosal entry of luminal FITC-D. Furthermore, an increased serosal pressure (5 cm H2O) moved significant amounts of serosal FITC-D into the lumen, whereas a corresponding pressure applied on the luminal side only marginally increased mucosal crossing of luminal FITC-D. By raising the luminal pressure to 10 and 20 cm H2O (which may be used as positive end-expiratory pressures (PEEP) in vivo in patients) mucosal penetration of luminal FITC-D was as marked as that induced in the opposite direction by the low (5 cm H2O) serosal pressure increase. Another aspect of the asymmetry of the airway mucosal barrier was evident from experiments examining the effect of a serosal pressure increase on mucosal penetration of luminal FITC-D. Neither during nor after the period of sustained serosal pressure increase was luminal FITC-D crossing the mucosa to a greater extent than under baseline zero-pressure conditions. This finding agrees with in-vivo data demonstrating that plasma exudation into the airway lumen may not be associated with an increased absorption of luminal solutes.(ABSTRACT TRUNCATED AT 250 WORDS)