Zone, euphoric

Saino and Hattori (1980) first observed distinct vertical changes in the N content of suspended particulate ifitrogen and related these changes to particle diagenesis. A sharp increase in N below the base of the euphoric zone has been ubiquitously observed (Altabet and McCarthy 1985 Saino and Hattori 1987 Altabet 1988). These findings imply that the vertical transport of organic matter is... 

Chrost, R. J., U. Munster, H. Rai, D. Albrecht, P. K. Witzel, and J. Overbeck. 1989. Photosynthetic production and exoenzymatic degradation of organic matter in the euphoric zone of a eutrophic lake. Journal of Plankton Research 11 223-242. 

Andreae et al. (231 reported two profiles from the Florida Straits. These profiles were characterized by subsurface maxima (-20-25 m) and a gradual decrease in DMS to less than 0.1 nmol L 1 below die euphoric zone. A profile of DMS obtained in the Atlantic (471 appeared not to have a distinct subsurface maximum (no surface value of DMS was reported). The 5 m sample contained 3.1 nmol L 1. The concentration decreased through 200 m, where it remained approximately 0.16 nmol L 1, to 4000 m where it was 0.03 nmol I/1. 

Johnstone, J. (1908) Nitrate flux into the euphoric zone near Bermuda. Nature 331, 521-523. 

Zubkov MV, Fuchs BM, Archer SD, Kiene RP, Amann R, Burkill PH (2002) Rapid turnover of dissolved DMS and DMSP by defined bacterioplankton communities in the stratified euphoric zone of the North Sea. Deep-Sea Res Part II 49 3017-3038... 

Putz (1997) estimated production as uptake of i C by periphyton that grew on artificial cellulose-acetate substrata suspended in several habitats near Manaus. Her results could not be used to compute an areal value for periphyton associated with floating macrophytes due to the complex surface of the natural substrata. To extrapolate her results to areal rates in floodplain forests requires an estimate of leaf area in the euphoric zone per unit area of water. Alves (1991) reported between about 0.5 and 1.5 m2 of leaves in the euphoric zone of flooded forest per m2 of water for simplicity we used 1.0. Based on net productivities measured by Putz (1997) at a site dominated... 

The primary engine that drives these ocean interior variations is the photosynthetic fixation of carbon into organic matter by marine phytoplankton in the fight-illuminated upper ocean (euphoric zone) (see Fig. 1.1). Along with carbon, nutrient elements such as nitrogen, phosphorus, iron and many others are taken up and assimilated. Most of the resulting organic matter is either respired or reminerafized... 

Hamanaka, J., Tanoue, E., Hama, T., and Handa, N. (2002). Production and export of particulate fatty acids, carbohydrates and combined amino acids in the euphoric zone. Marine Chemistry 77(1), 55-69. 

Recent research has found low, but measurable rates of N2 fixation in cooler surface waters (Table 4.6) (Needoba et al., 2007). If this is a general observation in colder waters, it would further close the gap. Similarly, while they predominate in surface waters (Church et al., 2008), diazotrophs can also be found below the euphoric zone (Hewson et al., 2007), and do exhibit low levels of activity (Hamers-ley, Capone, Montoya et al. in prep). 

Dore,. E., and Karl, D. M. (1996). Nitrification in the euphoric zone as a source for nitrite, nitrate, and nitrous oxide at station ALOHA. Limnology and Oceanography 41, 1619—1628. 

Nitrate was thought to be the predominant source of new N to the euphoric zone and so its uptake has been more widely measured that any other N compound (Table 7.1). That said, NOs upweUed from the deep ocean is not new N in the context of oceanic N inventories in general (see discussion of N2 fixation below and Chapter 4 by Carpenter and Capone, this volume)... 

Generally speaking, when N02 is abundant in the euphoric zone, N02 uptake can be significant (e.g., Glibert et al, 1991), however, N02 uptake is measured far less routinely than NOs and NH4+ uptake. N02 concentrations are generally low, but can at times accumulate throughout the entire euphoric zone (Al-Qutob et al, 2002 Lomas and Lipschultz, 2006) as well as at the base of the euphoric zone in what has been termed the primary N02 maximum (e.g., Rakestraw, 1936). Further, high N02 concentrations have been found in estuaries and coastal systems at least seasonally (Filippino et al, in revision Morse et al, in preparation Bronk, personal... 

CoUos, Y., and Slawyk, G. (1984). C and N uptake by marine phytoplankton. III. Interactions in euphoric zone profiles of stratified oceanic areas. Mar. Ecol. 19, 223—231. 

Sahlsten, E. (1987). Nitrogenous nutrition in the euphoric zone of the Central North Pacific Gyre. Mar. Biol. 96, 433-439. 

While zooplankton fuel primary production in the surface waters, they can also contribute to N regeneration at depth. A process that has received attention in the last two decades is the transport of regenerated N below the euphoric zone by diel... 

Carlson, C. A., Ducklow, H. W., and Michaels, A. F. (1994). Annual flux of dissolved organic carbon from the euphoric zone in the northwestern Sargasso Sea. Nature 371, 405—408. 

Singler, H., and ViUareal, T. A. (2005). Nitrogen inputs into the euphoric zone by vertically migrating Rhizosolenia mats. J. Plankton Res. 27(6), 545-556. 

Bjorkman, K. M., and Karl, D. M. (2003). Bioavailability of dissolved organic phosphorus in the euphoric zone at Station ALOHA, North Pacific Subtropical Gyre. Limnol. Oceanogr. 48, 1049-1057. 

Dore, J. E. (1995). Microbial Nitrification in the Marine Euphoric Zone Rates and Relationships with Nitrite Distributions, Recycled Production and Nitrous Oxide Generation, Ph.D. Dissertation. University of Hawaii, Honolulu. 

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