Atlantic Ocean biological processes

Measures, C.I. and J.D. Burton. 1980. The vertical distribution and oxidation states of dissolved selenium in the northeast Atlantic ocean and their relationship to biological processes. Earth Plan. Sci. Lett. 46 385-396. Medeiros, L.C., R.P. Belden, and E.S. Williams. 1993. Selenium content of bison, elk and mule deer. Jour. 

This model was first applied to dissolved oxygen gas (O2) profiles to estimate the rate of aerobic respiration. This biological process is responsible fiar the presence of a pronounced mid-depth O2 concentration minimum in the mid- and low latitudes throughout all the ocean basins. The concentration minimum in the Atlantic can be seen in Figure 4.l4e. The solution to Eq. 4.14, in the presence of an upward vertical advection, is... 

PO4 (Broecker and Maier-Reimer, 1992). While the deep Indian and Pacific values follow the slope expected for biologic processes, deep waters which form in the North Atlantic and Southern Ocean have, respectively, lower and... 

On time scales of oceanic circulation (1000 y and less) the internal distribution of carbonate system parameters is modified primarily by biological processes. Gross sections of the distribution of Aj and DIG in the world s oceans (Fig. 4.4) and scatter plots of the data for these quantities as a function of depth in the different ocean basins (Fig. 4.5) indicate that the concentrations increase in deep waters (1-4 Ion) from the North Atlantic to the Antarctic and into the Indian and Pacific Oceans following the conveyer belt circulation (Fig. 1.12). Degradation of organic matter (OM) and dissolution of GaGOs cause these increases in the deep waters. The chemical character of the particulate material that degrades and dissolves determines the ratio of At to DIG. 

Experience gained during the last decade in the determination of CBs in off-shore surface and deep waters has shown that concentrations are extremely low, much lower than reported earlier (see Table 22-1). Concentrations reported for the Mediterranean Sea (Tolosa et al, 1997 Schulz-Bull et al., 1997), the North Sea Schulz-Bull et al., 1991) and the Baltic Sea Schulz-Bull et al., 1995) were well above those found in surface waters of the open ocean Iwata et al., 1993 Schulz-Bull et a/.,1998). In deep-ocean water Schulz et al., 1988 Petrick et al, 1996 Schulz-Bull et al, 1998) much lower concentrations were found than in surface waters. In North Atlantic Deep Water, values of individual CBs were found to be < 0.01 pg/L, yet concentrations in solution were higher than those in suspended material on an equal volume basis. It turns out that the distribution of CBs between solution and suspension is determined primarily by molecular properties (characterized by octanol/water distribution coefficients). However, biological processes disturb the establishment of equilibria. This phenomenon has been observed in river water, in estuarine and coastal waters and during biologically active periods in the surface layer of the open ocean. 

Nitrate is the largest pool of combined nitrogen in the ocean, with deep water concentrations around 20 to 30 pmol L in the Atlantic and up to 45 pmol in the Pacific. The isotopic composition of the NOs" pool is affected by a variety of processes that move N in and out of the ocean or its biota (Fig. 29.3), and subsurface N03 acts as a critical isotopic end member for biological production in the upper water column. Of the processes shown in Fig. 29.3, pelagic denitrification and N2-fixation are generally viewed as the major, long-term controls on the size and isotopic composition of the oceanic pool of NOs" (Brandes and Devol, 2002). 

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