Euphotic zone organic matter productivity

As shown in Fig. 10-13, there is also a flux of O2 produced during net photosynthesis from the ocean to the atmosphere and an export flux of particulate and dissolved organic matter out of the euphotic zone. For a steady-state system, new production should equal the flux of O2 to the atmosphere and the export of organic carbon (Eppley and Peterson, 1979) (when all are expressed in the same units, e.g., moles of carbon). Such an ideal state probably rarely exists because the euphotic zone is a dynamic place. Unfortunately, there have been no studies where all three fluxes were measured at the same time. Part of the difficulty is that each flux needs to be integrated over different time scales. The oxygen flux approach has been applied in the subarctic north Pacific (Emerson et al, 1991) and subtropical Pacific (Emerson et al, 1995, 1997) and Atlantic (Jenkins and Goldman, 1985). The organic carbon export approach has... 

Despite these observations, exceUent correlation is found between the d N of bulk surface sedimentary N and that of the local sub-euphotic zone nitrate at sites where export production is high and/or organic matter preservation is good (many of which are from continental margins. Fig. 34.6) (ThuneU et al, 2004). In these... 

Among the questions that coagulation theory can help answer are how organisms feed on each other and how biological production leaves the euphotic zone. Coagulation theory and the related filtration theory have, in fact, been used to understand the nature of feeding in both planktonic and benthic animals (1 1). This chapter addresses the transport of organic matter downward, out of the euphotic zone. 

Considerable attention has been directed to particulate organic matter (POM) in the marine environment that is plausibly derived from organisms in the euphotic zone. This is supported by MS comparison of pyrolysis products from samples collected in sediment traps in the Mediterranean Sea with that from the diatom Biddulphia sinensis. Although the structures are unknown, a wide variety of compounds have been identified in the pyrolysates including aliphatic hydrocarbons and nitriles, pyrroles, indoles, and aromatic hydrocarbons (Peulve et al. 1996). 

With these conditions and c [uestions in mind, why is P more often limiting in lakes than on land, at least in the temperate zone P limits lake productivity because (a) unlike C and N, there are no mechanisms that can increase inputs of P when it is in short supply, as discussed above (b) P is relatively immobile within and through terrestrial ecosystems, so inputs of P to lakes are small and (c) lakes have an uncontrollable loss of P, in the sinking of particulate organic matter out of the euphotic zone. 

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