Pacific Ocean biological processes

Fig. 14-6 Profiles of potential temperature and phosphate at 21 29 N, 122 15 W in the Pacific Ocean and a schematic representation of the oceanic processes controlling the P distribution. The dominant processes shown are (1) upwelling of nutrient-rich waters, (2) biological productivity and the sinking of biogenic particles, (3) regeneration of P by the decomposition of organic matter within the water column and surface sediments, (4) decomposition of particles below the main thermocline, (5) slow exchange between surface and deep waters, and (6) incorporation of P into the bottom sediments.

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... 

Figure 4 Vertical profiles of total dissolved inorganic carbon (TIC) in the ocean. Curve A corresponds to a theoretical profile that would have been obtained prior to the Industrial Revolution with an atmospheric CO2 concentration of 280 ixmol mol The curve is derived from the solubility coefficients for CO2 in seawater, using a typical thermal and salinity profile from the central Pacific Ocean, and assumes that when surface water cools and sinks to become deep water it has equilibrated with atmospheric CO2. Curve B corresponds to the same calculated solubility profile of TIC, but in the year 1995, with an atmospheric CO2 concentration of 360 xmol moPk The difference between these two curves is the integrated oceanic uptake of CO2 from anthropogenic emissions since the beginning of the Industrial Revolution, with the assumption that biological processes have been in steady state (and hence have not materially affected the net influx of CO2). Curve C is a representative profile of measured TIC from the central Pacific Ocean. The difference between curve C and B is the contribution of biological processes to the uptake of CO2 in the steady state (i.e. the contribution of the biological pump to the TIC pool.) (courtesy of Doug Wallace and the World Ocean Circulation Experiment).

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. 

The process of enrichment of trace metals in these non-biologically produced sediments is probably adsorption to the surface of iron and manganese oxides that form on virtually all particle surfaces in the ocean. This is also the process that forms manganese nodules in vast areas of deep-ocean sediments. Manganese nodules actually accrete on the sea floor at a rate of approximately 1 mm per million years, primarily in areas where there is little accumulation of CaCOs and opal-rich sediments, e.g. the vast red clay provinces of the North Pacific Ocean. Manganese nodules are enriched in the same metals that are found authigenically in the sediments (Table 12.4) to such an extreme... 

Masuzawa and Koyama (1989) attributed the positive Ce anomalies of their sediment trap samples (Japan Sea) to a biologically-mediated oxidation process associated with the presence of Mn oxide particles. This process is discussed in detail in the subsection on Ce redox chemistry. The shale-normalized patterns of Masuzawa and Koyama (1989) do not show any consistent form from which to draw conclusions about lanthanide(lll) fractionation. Only their 2750 m sample is slightly light-element enriched the other four samples have flat or heavy-enriched patterns. Sediment trap particles from the eastern equatorial Pacific Ocean (Murphy and Dymond 1984) are strikingly different in that their shale-normalized patterns are like those of seawater heavy-lanthanide enrichment and negative Ce anomalies. 

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). 

Emerson, S. (1997) Net biological oxygen production a global estimate fix>m oceanic measurements. In Biogeochemical Processes in die North Pacific (ed. S. Tsunogai), pp. 143-55. Tokyo Japan Marine Science Foundation. 

Concentrations of many trace element nutrients (zinc, cadmium, iron, copper, nickel, and selenium) increase with depth in the ocean, similar to increases observed for major nutrients (nitrate, phosphate, and silicic acid) (Figures 2—4). In the central North Pacific, filterable concentrations of zinc and cadmium increase by 80-fold and 400-fold, respectively, between the surface and 1000-m depth. The similarity between vertical distributions of these trace elements and major nutrients indicates that both sets of nutrients are subject to similar biological uptake and regeneration processes. In these processes, both major and trace element nutrients are efficiently removed from surface waters through uptake by phytoplankton. Much of these assimilated nutrients are recycled within the euphoric zone by the coupled processes of zooplankton grazing and excretion, viral lysis of cells, and bacterial degradation of organic... 

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