Determination of Consumption Rates and Benthic Fluxes

1 Fluxes and Concentration Profiles Determined by In Situ Devices 

Under normal deep-sea oxygen eonditions, the nitrate flux is generally direeted out of the sediment due to nitrifieation and lower denitrifieation as shown by results reported by Hammond et al. 

The result of the phosphate measurement shown in Fignre 6.15 indicates that flux chamber measurements are restricted to a certain number of measurable parameters. Even more, this is true for profiling lander systems. Apart from oxygen, only pH-, pCOj-, H S and Ca-electrodes have been successfully employed on in situ lander systems (Cai et al. 1995 Hales and Emerson 1997 Wenzhofer et al. 2001a de Beer et al. 2005). There is, however, another microelectrode technique 

2 Ex-Situ Pore Water Data from Deep-Sea Sediments 

A further aspect of decompression that should be kept in mind is the degassing of CO and the resulting precipitation of CaCO, which might affect pore water concentrations of phosphate by adsorption or co-precipitation (Jahnke et al. 1982). This effect can even imply negative fluxes as discussed below (see Section 6.5.1). 

---