Antarctica Southern Ocean

Effect of UV on Productivity of the Southern Ocean. Has ozone depletion over Antarctica affected the productivity of the Southern Ocean There is no easy answer. First, one has to take into account the fact that the drastic decrease of ozone over Antarctica has been reported as recently as 1976, a relatively short time in the evolution of the organisms to develop mechanisms to cope with elevated UV. One of the most vexing problems in studying the effects of UV radiation on productivity, is a dearth of historical data on the level of UV. Without these baselines, normal fluctuations could easily be interpreted as decline in productivity. Second, there is a host of biotic and abiotic factors that play significant roles in governing the productivity of the Southern Ocean (40). Ultraviolet radiation is but one more complicating factor to be considered in an already stressful environment. 

Because temperature (T) and salinity (S) are the main factors controlling density, oceanographers use T-S diagrams to describe the features of the different water masses. The average temperature and salinity of the world ocean and various parts of the ocean are given in Fig. 10-3 and Table 10-3. The North Atlantic contains the warmest and saltiest water of the major oceans. The Southern Ocean (the region around Antarctica) is the coldest and the North Pacific has the lowest average salinity. 

MSA and SOl histories from Antarctica (Legrand et al, 1991) imply a very different response (Fig. 18-18) for the southern oceans than for those of the north. While not... 

Evidence of the fall dump of giant diatoms. Sediment layers from (a) the Gulf of California dominated by cell walls of Stephanopyxis palmeriana (diameter <70 ji,m) (b) the Southern Ocean, showing a tangled mass of the rod-shaped species Thalassiothrix antarctica, which grows up to 4 mm in length. Source From Kemp, A. E. S., et al. (2000). Deep-Sea Research II, 47, 2129-2154. 

Figure 7.1. View of Earth from Apollo 17 showing the African continent, the Southern Ocean and portions of the Atlantic and Indian Oceans, Antarctica, and extensive cloud cover. It emphasizes interfaces between continents and oceans (solid-liquid), continents and atmosphere (solids and gases), and oceans and atmosphere (liquids and gases). From NASA (http //visibleearth.nasa.gov/view-rec.php id = 12907).

DMS emission fluxes from Antarctic inshore waters may be important for the tropospheric sulfur budget of Antarctica during summer. The contribution of the Southern Ocean to the global atmospheric sulfur budget (ca. 0.2 Tmol yr1) is consistent with present estimates of the total global DMS emission from the world s oceans (0.5-1.2 Tmol yr1). 

Phaeocystis antarctica recurrently produces large blooms in the Southern Ocean such as in Prydz Bay and the southern Ross Sea (e.g., El-Sayed et al. 1983 Davidson and Marchant 1992 Smith et al. 1996). In the Ross Sea, P. antarctica blooms early in the season, in waters characterized by relatively high Fe levels (Sedwick et al. 2000). Among the phytoplankton community, P. antarctica showed indeed the strongest response to Fe addition, increasing its relative abundance from <5 up to 20% in 2.5 nM Fe-enriched seawater (Coale et al. 2003). 

The question of the fate of the carbon produced by P. antarctica in the Southern Ocean is still unresolved. Bacterial degradation has been proposed to be a major pathway in polar waters. However, several... 

Nichols PD, Skerratt JH, Davidson A, Burton H, McMeekin TA (1991) Lipids of cultured Phaeocystis pouchetii signatures for food-web, biogeochemical and environmental studies in Antarctica and the Southern-Ocean. Phytochemistry 30 3209-3214... 

Daly KL, DiTullio GR (1996) Particulate dimethylsulfoniopropionate removal and dimethylsulfide production by zooplankton in the Southern Ocean. In Kiene RP, Visscher PT, Keller MD, Kirst GO (eds) Biological and environmental chemistry of DMSP and related sulfonium compounds. Plenum Press, New York, pp 223-238 Davidson AT, Marchant HJ (1987) Binding of manganese by Antarctic Phaeocystis pouchetii and the role of bacteria in its release. Marine Biol 95 481-487 DiTullio GR, Smith WO (1995) Relationship Between Dimethylsulfide And Phytoplankton Pigment Concentrations In The Ross Sea, Antarctica. Deep-Sea Res Part 142 873-892... 

Annual patterns of P. antarctica in the Southern Ocean may thus be determined by the interplay between variable micronutrient concentrations and irradiance availability. In contrast, patterns in high latitudes in the northern hemisphere, where iron is not typically limiting, are primarily determined by nutrient conditions and large-scale hydrographical phenomena. 

For instance, nitrate and phosphate penetrate much further north than does sihcate in the Southern Ocean, the polar ocean surrounding Antarctica (Figures 5(b)-(d)). As silicate is needed by diatoms but not other types of phytoplankton, this difference has major implications for the ecology of the Southern Ocean, present and past. Moreover, since surface water from 40-50° S is fed into the thermocline that... 

Most petrels and shearwaters nest on isolated islands in the southern oceans, some as far south as Antarctica. Several species, however, breed in Hawaii, the northwestern United States (including Alaska), Maine, and Canada. These birds frequently range far from their birthplace, covering thousands of miles in an endless search for food. The greater shearwater, for example, nests on the Tristan da Cunha islands in the South Atlantic Ocean but may be found in the North Atlantic from Florida to Newfoundland during the northern summer. Other species may spend months circumnavigating the Pacific. 

The majority of the investigations were carried out in the Weddell Sea, the Weddell/Scotia confluence and the Indian sector of the Southern Ocean (125, 127, 129, 132, 135). Very few data are available on trace metal distribution in the Ross Sea area early measurements on Cu distribution in surface waters between New Zealand and the Ross Sea were reported by Boyle and Edmond and more recently some investigations were carried out by Martin et ah, also during the oceanographic campaigns as a part of the Italian National Programme of Researches in Antarctica (PNRA) (35, 57, 69, 124, 130, 131, 133, 134, 136, 137). 

P. A. Berckman, M. Nigro, Trace metal concentrations in the scallops around Antarctica extending the Mussell Watch Program to the Southern Ocean, Mar. Pollut. Bull., 24 (1992), 322-323. 

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