Concentrations of dissolved organic carbon and particulate organic nitrogen in the Eastern North Pacific

Data are presented on concentration of dissolved organic carbon and particulate organic nitrogen in sea water at four stations, and also of dissolved and particulate amino acids at a deep-sea station above the Japan Trench. Concentration of Corg ranged from 0.79 to 2.00 mg/l, reaching maximum in the upper productive layers, while that of particulate Norg varied from 0.0018 to 0.037 mg/l, the maximum being in the upper layer (0-100 m). Water and particulate matter contained 18 amino acids in concentrations varying from 0.150 to 0.177 mg/l in the former and from 0.010 to 0.048 mg/l in the latter. Amino acid composition is variable. Vertical distribution of dissolved Corg and particulate Norg, as well as of dissolved and particulate amino acids is greatly dependent on water dynamics.

Increased CO2 modifies the carbon balance and the photosynthetic yield of two common Arctic brown seaweeds: Desmarestia aculeata and Alaria esculenta

Ocean acidification affects with special intensity Arctic ecosystems, being marine photosynthetic organisms a primary target, although the consequences of this process in the carbon fluxes of Arctic algae are still unknown. The alteration of the cellular carbon balance due to physiological acclimation to an increased CO2 concentration (1300 ppm) in the common Arctic brown seaweeds Desmarestia aculeata and Alaria esculenta from Kongsfjorden (Svalbard) was analysed. Growth rate of D. aculeata was negatively affected by CO2 enrichment, while A. esculenta was positively affected, as a result of a different reorganization of the cellular carbon budget in both species. Desmarestia aculeata showed increased respiration, enhanced accumulation of storage biomolecules and elevated release of dissolved organic carbon, whereas A. esculenta showed decreased respiration and lower accumulation of storage biomolecules. Gross photosynthesis (measured both as O2 evolution and 14C fixation) was not affected in any of them, suggesting that photosynthesis was already saturated at normal CO2 conditions and did not participate in the acclimation response. However, electron transport rate changed in both species in opposite directions, indicating different energy requirements between treatments and species specificity. High CO2 levels also affected the N-metabolism, and 13C isotopic discrimination values from algal tissue pointed to a deactivation of carbon concentrating mechanisms. Since increased CO2 has the potential to modify physiological mechanisms in different ways in the species studied, it is expected that this may lead to changes in the Arctic seaweed community, which may propagate to the rest of the food web.