Shallow water sediments

Particular attention has been focused on the toxic effects of aromatic hydrocarbons because these chemicals have proven highly carcinogenic to humans and marine life. Of greatest concern are the PAHs, which are toxic to the benthos at the ppb level. The most common compounds are shown in Figure 28.20 their structures are based on fused aromatic rings. These high-molecular-weight compoimds are very nonpolar and, hence, have low solubilities. Once in seawater, they tend to adsorb onto particles and become incorporated in the sediments. The toxicity of PAHs is enhanced by photochemical reaction with UV radiation. Photo-activated toxicity is especially problematic in shallow-water sediments, such as found in estuaries. 

Base upon studies of diurnal fluctuations at a shallow water sediment in the Kiel Bight (cf. above), a bacterial net production of 80 mg of carbon per m2 per day was calculated. Further estimates of bacterial production were derived from investigations of seasonal varaitions in bacterial biomass at two sediment stations in deeper waters of the Kiel Bight. As response to the input of the phytoplankton bloom in autumn, bacterial production amounted to 140 and 370 mg of carbon per m2 per day (sandy-mud and muddy sediment, respectively). The corresponding values in spring were 300 and 120 mg of carbon per m2 per day, respectively (cf. Table 1). As it was pointed out above, these values well... 

Nuclear weapons testing in the atmosphere introduced excess l4C that has proven to be an excellent tracer for processes that will be important in the uptake of fossil fuel CO2. For example, Peng (1986) mapped global uptake patterns of excess 14C and used these to calculate fossil fuel CO2 uptake by the oceans. His results indicate that about 10% of the fossil fuel CO2 is "missing". In the next chapter we will discuss the possibility that this missing CO2 may be the result of dissolution of highly soluble magnesian calcites from shallow water sediments. Also, Feely and... 

Morse J.W., Zullig J.J., Bernstein L.D., Millero F.J., Milne P Mucci A. and Choppin G.R. (1985) Chemistry of calcium carbonate-rich shallow water sediments in the Bahamas. Amer. J. Sci. 285, 147-185. 

Hopkinson, J. (1987). Nutrient regeneration in shallow-water sediments of the estuarine plume region of the nearshore Georgia Bight, USA. Mar. Biol. 94, 127—142. 

The rocks of the Belingwe belt span a range of ages, but the sequence that carries the most detailed evidence for life (Figures 4 and 5), the Ngesi Group, is 2.7 Ga old. The base of the Group includes shallow-water sediment locally rich in... 

Above the komatiites are thick basalt pillows and flows. At the top of the sequence is a further sequence of shallow-water sediments, including limestones that locally have extensive and very well preserved stromatolites (Figure 4). These too have evidence for mbisco fractionation (see Section 8.01.7.2), both in kerogen carbon, and in carbonate with Q%o. 

A new compound, bonactin 243, was isolated from the liquid culture of a Streptomyces sp. BD21-2 obtained from a shallow-water sediment... 

Two new indole nucleosides kahakamides A 256 and B 257 were isolated from the actinomycete Nocardiopsis dassonvillei which is obtained from a shallow water sediment sample collected from the island of Kauai, Hawaii. Compound 256 exhibited anti-microbial activity toward the Gram positive bacterium Bacillus subtilis. 

Carbon isotopes in shallow-water sediments Spring Valley, Shavi and Cheshire stromatolites and black shales... 

F. Garcia-Pichel, B.M. Bebout (1996). Penetration of ultraviolet radiation into shallow water sediments High exposure for photosynthetic communities. Mar. Ecol. Prog. Ser., 131,257-262. 

Table 1 Oxidants and reductants in shallow-water sediments ...

Hamilton, E.L., Bachman, R.T., Berger, W.H., Johnson, T.C., and Mayer, L.A. 1977. Acoustic and related properties of calcareous deep-sea sediments. Journal of Geophysical Research, 52(3) 733-753. Hamilton, E.L., Shumway, G., Menard, H.W., and Shipek, C.J. 1956. Acoustic and other properties of shallow-water sediments off San Diego. Journal of the Acoustical Society of America, 28 1-15. 

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