Algal material, sedimentation

The committee thus recommends that a limited number of carefully chosen matrix reference materials be prepared (based on seawater, sediments, and algal materials) to respond to a significant portion of the current pressing needs. Such materials, certified for a limited number of key... 

Most of the reference materials discussed are based on natural matrices (seawater, algal cells, sediment) and would initially only be certified for a limited number of constituents. Nevertheless, it is apparent that such materials provide a resource for the investigation of a much wider variety of constituents, and it is important that the ocean science community be encouraged to investigate these materials further. In particular, the existence of these materials would facilitate a wide variety of necessary interlaboratory method comparisons that have been neglected to date. Eventually these intercomparisons will result in consensus values for other constituents, which can then be assigned to the reference materials. 

For the removal of Zn from the water column by sedimentation, both algal material and manganese oxides are likely to be important carrier phases. The Zn sedimentation rates show maxima from June to August, at the time of the maximum sedimentation of P (indicating the sedimentation of algal material), and in December, in line with the sedimentation of manganese oxides (86). 

There is no indication of a release of Zn from the sediments during the development of anoxia, unlike the release of phosphate and dissolved silicate. Zn bound to algal material may be dissolved upon mineralization of this material and Zn bound to manganese oxides upon dissolution of manganese oxides. It appears, however, that Zn is efficiently retained in the sediments, probably through bonding to other less soluble particles, such as iron oxides and silica parts of diatoms. In the presence of sulfide, Zn is probably retained in association with sulfide-containing particles. 

Enoksson, V. (1993). Nutrient recyling in coastal sediments Effects of added algal material. Mar. Ecol. Prog. Ser. 92, 245-254. 

The fate of trace ELEMENTS in a eutrophic lake is strongly linked to biological processes, as has been demonstrated for the oceans (1-3). Photo-svnthetic production of algae and the subsequent sedimentation of algal material affect the removal of metal ions to the sediments (4). High sedimentation rates in eutrophic lakes indicate efficient mechanisms for elimination of metal ions. As a result, low concentrations of trace metals are found in the water column. 

Both the NP + A9PEOi+2 concentrations in sediment with and without overlying macroalgae and the increased concentrations in resuspended material during the algal bloom showed the important role played by algae in the environmental fate of A9PE0. 

Sediment reference materials should be developed for both open-ocean and coastal areas. Open-ocean sediments should include carbonate-rich, silicate-rich, and clay mineral-rich types. Coastal sediments should be of the same types and should include a deltaic sediment that has not been in contact with seawater. Taken together with the algal-based materials, these sediment materials would represent a wide range of diagenetic states. The committee recommends that each of these solid... 

FIGURE 3 Depth profiles for 14C age and sulfur-to-carbon (S/C) ratios for fulvic acid samples isolated from Lake Fryxell, a permanently ice-covered lake in the McMurdo Dry Valleys, Antarctica (from Aiken et al., 1996). In the upper water column, the fulvic acids have a modern signal. This young fulvic acid derives from perennial algal mats in glacial meltwater streams. At depth, the fulvic acids are quite old (about 3000 years) and are possibly derived from organic material in sediments. The ratio of S/C increases with depth as conditions in the water column become anoxic. 

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