Microalgae water column

As discussed earlier, not only does deposition of POM to the sediment surface typically vary over time in estuaries, but there are also issues of POM actively growing at the sediment-water interface, such as benthic microalgae. This is an important issue because the rate of supply of POM is assumed to be equal to the depositional flux from the water column (Berner, 1980). More details on diagenetic models addressing the surface boundary condition constraints as well as POM lability can be found in Aller (1982) and Rice and Rhoads (1989). When examining biological mixing as a one-dimensional... 

Benthic microalgae in and on reef sediments may derive some of their nutrients from the sediments as appreciable ammonium levels have been reported (Capone et al., 1992 Heil et al., 2004 Johnstone et al., 1990). Increases in benthic microalgae with nutrient enrichment suggest that these populations can also access nutrients in the water column, which result from regenerative processes within the water column. Benthic microalgae are also net O2 producers which may influence nutrient dynamics, particularly nitrification and denitrification by changing redox profiles as weU as the nutrient exchange across the sediment water interface. 

This model shows the aquatic ecosystem where phytoplankton, epiflora, macrophytes, and benthic microalgae all compete for limited availability of light and nutrients. Competition for the light occurs through direct shading, while nutrient competition involves two separate sources of nitrogen (water column and sediment... 

Fig. 2.31. Chromatogram of crude lutein from the microalga Chlorella vulgaris by HPLC analysis, A = lutein. Conditions column reversed-phase C18 column (250 X 4.6 mm i.d., 5 pm) mobile phase methanol-dichloromethane-acetonitrile-water (67.5 22.5 9.5 0.5, v/v) flow rate l.Oml/min detection at 450 nm (a). Chromatogram of crude lutein from the microalga Chlorella vulgaris by preparative HSCCC separation, A = lutein. Conditions column multilayer coil of 1.6mm i.d. PTFE tube with a total capacity of 230ml rotary speed 800rpm solvent system ra-hexane-ethanol-water (4 3 1, v/v) mobile phase lower phase (ethanol-water) flow rate lml/min detection at 254 nm sample size 200 mg retention of the stationary phase 58 per cent (b). Reprinted with permission from H.-B. Li el al. [70].

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