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ULTRAVIOLET-B RADIATION EFFECTS ON INORGANIC NITROGEN UPTAKE BY NATURAL ASSEMBLAGES OF OCEANIC PLANKTON
Citation:
Behrenfeld, M., D. Lean, AND H. II. ULTRAVIOLET-B RADIATION EFFECTS ON INORGANIC NITROGEN UPTAKE BY NATURAL ASSEMBLAGES OF OCEANIC PLANKTON. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/429.
Description:
Ultraviolet-B radiation (UVBR: 290-320 nm) inhibited ammonium uptake (PNH4) and nitrate uptake (PNO4) in natural plankton assemblages collected during a transect from 37 degrees N in the Pacific Ocean. omparison of responses in PNH4 to ambient solar- and lamp-enhanced UVBR spectra allowed calculation of an action spectrum for PNH4 inhibition. he slope of the action spectrum for PNH4 is half as steep as action spectra for UVBR inhibition of photosynthetic carbon uptake. onsequently, UVBR-induced photoinhibition of PNH4 extends to greater depths than inhibition of carbon fixation due to the greater relative effect of longer UVBR wavelengths. nhibition of PNH4 was dependent upon UVBR dose when doses were weighted by the PNH4 action spectrum. ependence of UVBR inhibition of PNH4 on dose rate was not apparent. e found that near-surface PNH4 and PNO3 can be overestimated in excess of 50% when measured using standard incubation vessels made of UVBR-absorbing materials such as polycarbonate.