OXYGEN Baltic

Season of collection (Fowler and Oregioni 1976 Sanders etal. 1991) and latitude (Anderlini 1974) also influenced silver accumulations. Seasonal variations in silver concentrations of Baltic clams (Macoma balthica) were associated with seasonal variations in soft tissue weight and frequently reflected the silver content in the sediments (Cain and Luoma 1990). Oysters from the Gulf of Mexico vary considerably in whole-body concentrations of silver and other trace metals. Variables that modify silver concentrations in oyster tissues include the age, size, sex, reproductive stage, general health, and metabolism of the animal water temperature, salinity, dissolved oxygen,... 

Figure 11.10 Negative correlations between dissolved inorganic phosphorus (pM) and oxygen (mL L-1) concentrations in bottom waters of the Baltic Sea. (Modified from Conley et al., 2002.)...

The suboxic zone is defined as the region between where oxygen decreases to near zero (O2 < 10 xM) and where sulfide first appears (H2S > 1 iM) [16, 17]. Many important redox reactions involving Fe, Mn, N, and other intermediate redox elements occur in the suboxic zone. Similar redox reactions take place in sediments throughout the world s oceans, but they are easier to study in the Black Sea because they are spread out over a depth scale of tens of meters (rather than centimeter or millimeter scales as in sediments). The Black Sea suboxic layer hydrophysical structure is very stable compared with other ocean redox regions such as Cariaco Trench, which is influenced by mesoscale eddies, or the Baltic Sea that is influenced by inflows of the North Sea saline oxygenated waters in cold winters. 

Amber consists basically of carbon, hydrogen and oxygen, with traces of other elements. Baltic amber contains a much hi er percentage of sucdnic add than any other amber and is therefore sometimes named sucdnite. (To some purists, only succinite is real amber. Other ambers, which contain no sucdnic add, are then called retinites .)... 

N2O profiles from oceanic regions with suboxic zones such as the Arabian Sea and the eastern tropical North Pacific Ocean, which are sites of intense denitrification activities, generally show a two-peak structure (Fig. 2.3) N2O maxima are found at the upper and lower boundaries of the oxygen minimum zone (OMZ), whereas in the core of the suboxic zone, N2O concentrations are considerably depleted (Bange et ah, 2001b Cohen and Gordon, 1978). In anoxic water masses such as found in the central Baltic Sea, the Cariaco Basin, and Saanich Inlet, N2O concentrations are close to the detection limit or not detectable (Brettar and Rheinheimer, 1991 Cohen, 1978 Hashimoto et ah, 1983 Ronner, 1983 Walter et ah, 2006b). 

Ronner, U., and Sorensson, F. (1985). Denitrification rates in the low-oxygen waters ofthe stratified Baltic Proper. Appl. Environ. Microbiol. 50, 801—806. 

Pers, C., and Rahm, L. (2000). Changes in apparent oxygen removal in the Baltic Proper deep water. J. Mar. Syst. 25, 421—429. 

Stigebrandt, A. (1991). Computations of oxygen fluxes through the sea surface and the net production of organic matter with application to the Baltic and adjacent seas. Limnol. Oceanogr. 36, 444—454. 

However, it should be noted that the oxygen isotopic signature of the present Baltic Sea water is approximately — 8.5%o. This is very different from the samples with Baltic like 5 C1 shown in the figures. One explanation is that the paleo-Baltic signature would most likely have been much more negative during periods immediately... 

The first evidence that this assumption was incorrect was provided by observations of carbon tetrachloride (CCI4) removal in the Baltic Sea under anoxic conditions (Krysell et al., 1994). A later investigation in the Black Sea found that reductions in CCI4, CHCI3, CH3CCI3, dibromo-methane and dibromochloromethane, and bromo-dichloromethane were related to oxygen/ hydrogen sulfide concentrations (Tanhua et al.,... 

An obvious consequence of increasing Nr inputs to coastal waters over the past few decades has been an increase in the size of water masses that are anoxic (completely devoid of oxygen) or hypoxic (concentrations of oxygen less than 2-3 mg L ). These dead zones can be found in the Gulf of Mexico, Chesapeake Bay, Long Island Sound, Florida Bay, the Baltic Sea, the Adriatic Sea, and many other coastal areas (Diaz and Rosenberg, 1995 NRC, 2000). 

The isolated deep waters of the Baltic have probably always had low oxygen concentrations. However, the declining trend over recent years means that, in some areas, oxygen concentrations have fallen to zero (anoxic). Under anoxic conditions, respiration of organic matter by microbial sulphate (SO4-) reduction has produced hydrogen sulphides (HS ) (plotted as negative oxygen in Fig. 6.30). 

Fig. 6.30 Oxygen and phosphorus concentrations in the Baltic Sea. Dark line through data is a regression line and thin line marks zero 02 concentration. DIP, dissolved inorganic phosphorus. Data plots after Fonselius (1981) and Nehring (1981), with permission from Elsevier Science.

The Baltic contrasts with the nearby North Sea, where oxygen concentrations rarely fall to low levels, despite large inputs of nutrients. This is because the North Sea is shallow and its waters exchange freely with those of the North Atlantic providing a constant supply of oxygen-rich surface water to the North Sea deeper waters. 

Hundreds of other waterways around the globe can tell similar and even more dramatic tales. From the Chesapeake Bay to the Baltic Sea and the estuaries of southern China, runaway nutrients from farmers fields are feeding blooms of algae that cloud the water, suck up oxygen, and suffocate fish. When the fish die, birds that feed on them soon disappear. 

Major Baltic inflows cause a renewal process in the central Baltic deepwater. Salinity and oxygen concentration increase below the permanent halocline. The increase in salinity depends on the amount and salinity of the inflowing water and on the salinity of the ambient... 

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