The Deep Sea

As previously mentioned, the primary processes responsible for variations in the deep sea C02-carbonic acid system are oxidative degradation of organic matter, dissolution of calcium carbonate, the chemistry of source waters and oceanic circulation patterns. Temperature and salinity variations in deep seawaters are small and of secondary importance compared to the major variations in pressure with depth. Our primary interest is in how these processes influence the saturation state of seawater and, consequently, the accumulation of CaC03 in deep sea sediments. Variations of alkalinity in deep sea waters are relatively small and contribute little to differences in the saturation state of deep seawater. 

Saturation State of Deep Seawater with Respect to CaC03 

Millero et al. (1979) summarized data of their own and of other investigators on the carbonate chemistry of the Mediterranean Sea. This sea is interesting, because its waters are supersaturated everywhere with respect to both calcite and aragonite. Both minerals are found in abundance in the sediments. The carbonate system in the Mediterranean Sea may be similar to that found in ancient epicontinental seas. 

---

Deep-Sea Manganese Nodules. A potentially important future source of manganese is the deep-sea nodules found over wide areas of... 

Campbell, A. K., and Herring, P. J. (1987). A novel red fluorescent protein from the deep sea luminous fish Malacosteus niger. Comp. Biochem. Physiol. 86B 411-417. 

Herring, P. J. (1990). Bioluminescence response of the deep-sea scyphozoan Atolla wyvillei. Mar. Biol. 196 413-417. 

Johnsen, S., Balser, E. J., Fisher, E. C., and Widder, E. A. (1999). Bioluminescence in the deep-sea cirrate octapod Strauroteuthis syrtensis Verrill (Mollusca Cephalopoda). Biol. Bull. 197 26-39. 

Shimomura, O., Masugi, T., Johnson, F. H., and Haneda, Y. (1978). Properties and reaction mechanism of the bioluminescence system of the deep-sea shrimp Oplophorus gracilorostris. Biochemistry 17 994-998. 

The formation and dissolution of CaCOa in the ocean plays a significant role in all of these effects (34)- CaCOa is produced by marine organisms at a rate several times the supply rate of CaCOa to the sea from rivers. Thus, for the loss of CaCOa to sediments to match the supply from rivers, most of the CaCOa formed must be redissolved. The balance is maintained through changes in the [COa] content of the deep sea. A lowering of the CO2 concentration of the atmosphere and ocean, for example by increased new production, raises the [COa] ion content of sea water. This in turn creates a mismatch between CaCOa burial and CaCOa supply. CaCOa accumulates faster than it is supplied to the sea. This burial of excess CaCOa in marine sediments draws down the [COa] - concentration of sea water toward the value required for balance between CaCOa loss and gain. In this way, the ocean compensates for organic removal. As a consequence of this compensation process, the CO2 content of the atmosphere would rise back toward its initial value. 

The elements Na, K, Cl, SO, Br, B, and F are the most conservative major elements. No significant variations in the ratios of these elements to chlorine have been demonstrated. Strontium has a small (< 0.5%) depletion in the euphotic zone (Brass and Turekian, 1974) possibly due to the plankton Acantharia, which makes its shell from SrS04 (celestite). Calcium has been known since the 19th century to be about 0.5% enriched in the deep sea relative to surface waters. Alkalinity (HCOf") also shows a deep enrichment. These elements are controlled by the formation... 

The carbonate system plays a pivotal role in most global cycles. For example, gas exchange of CO2 is the exchange mechanism between the ocean and atmosphere. In the deep sea, the concentration of COi ion determines the depth at which CaCOs is preserved in marine sediments. 

To a first approximation the deep ocean distributions shown in Fig. 10-20 can be reproduced if the particulate material dissolving in the deep sea has the ratio of 1 mol CaCOs to 4 mol organic carbon (Broecker and Peng, 1982). 

The inadequacy of the two-box model of the ocean led to the box-diffusion model (Oeschger et al, 1975). Instead of simulating the role of the deep sea with a well-mixed reservoir in exchange with the surface layer by first-order exchange processes, the transfer into the deep sea is maintained by vertical eddy diffusion. In... 

Douglas, G. and Savin, S.M. (1973) Oxygen and carbon isotope analyses of Cretaceous and Tertiary foraminifera from the central North Pacific. Washington, D.C. U.S. Govt. Printing Office, Initial Reports of the Deep Sea Drilling Project, 17, 591-605. 

The main problem of hydrate formation will arise in pipelines transporting natural gas, because gas hydrates are solids and will leave deposits. The solid deposits reduce the effective diameter of the pipeline and can therefore restrict or even clog the flow properties. Furthermore, the formation of condensates, hydrates, or ice may occur in the course of decompression of natural gas stored in natural reservoirs (e.g., in salt caverns). The operation of oil and gas pipelines in the deep sea is significantly complicated by the formation of gas hydrates [1204]. Experience indicates that large gas hydrate plugs in gas and oil pipelines form most actively during the period of an unforeseen long shut-down. In static conditions, three types of hydrate crystals can be formed [1153] ... 

Bacon MP, Anderson RF (1982) Distribution of thorium isotopes between dissolved and particulate forms in the deep sea. J Geophys Res 87 2045-2056... 

Efforts to apply Equations (6) and (7) to distributions of Th isotopes in the oceans showed that the situation was more complex. For example. Bacon and Anderson (1982) measured vertical distributions of Th in the deep sea and found that both the particulate and dissolved fractions increased linearly with depth. While the former observation is predictable from Equation (7) if sinking particles continue to scavenge Th during their descent, the latter is inconsistent with Equation (6). Bacon and Anderson (1982) suggested that the data could best be explained by a reversible scavenging equilibrium maintained between dissolved and particulate Th. Thus Equation (6) must be modified to ... 

Values of Db determined by " Th profiles commonly range from 1 to 50 cm7y in estuarine and slope sediments (Aller and Cochran 1976 Aller et al. 1980 Sun et al. 1994 Gerino et al. 1998 Green et al. 2002) to < 10 cm7y in the deep sea (Aller and DeMaster 1984 Pope et al. 1996). Although there is some overlap, mixing rates in the deep sea tend to be lower than those in nearshore sediments. This trend has been documented with °Pb profiles as well (e.g., Henderson et al. 1999). 

Aller RC, DeMaster DJ (1984) Estimates of particle-flux and reworking at the deep-sea floor using Th-234/U-238 disequilibrinm. Earth Planet Sci Lett 67 308-318 Amid D, Cochran JK, Hirschberg DJ (2002) disequihbrium as an indicator of the seasonal... 

Bacon MP, Spencer DW, Brewer PG (1976) Pb-210/Ra-226 and Po-210/Pb-210 disequilibria in seawater and snspended particulate matter. Earth Planet Sci Lett 32 277-296 Bacon MP, Anderson RF (1982) Distribution of thorium isotopes between dissolved and particulate forms in the deep sea. J Geophys Res 87 2045-2056... 

A correlation exists between the flux of particles collected by sediment traps and the ( Paxs/ °Thxs) of these particles (Kumar et al. 1995). In pelagic regions, particulate material settling through the deep sea is almost entirely of biogenic origin. A... 

Yang H-S, Nozaki Y, Sakai H (1986) The distribution of h and Pa in the deep-sea sttrface sediments of the Pacific Oceaa Geochim Cosmochim Acta 50 81-89 Yokoyama T, Esat TM, Lambeck K (2001) Coupled chmate and sea-level changes deduced from Huon Peninsttla coral terraces of the last ice age. Earth Planet Sci Lett 193 579-587 Yu E-F, Francois R, Bacon MP, Fleer AP (2001a) Flttxes of h and Pa to the deep sea Implicatiotts for the interpretation of excess °Th and Th profiles in sediments. Earth Planet Sci Lett 191(3-4) 219-230... 

Sarmiento JL, Rooth CG (1980) A comparison of vertical and isopycnal mixing models in the deep-sea based on Rn measurements. J Geophys Res 85 1515-1518 Shaw TJ, Moore WS, Kloepfer J, Sochaski MA (1998) The flux of barium to the coastal waters of the Southeastern United States the importance of submarine groundwater discharge. Geochim Cosmochim Acta 62 3047-3052... 

---