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Free Content Nitrogen recycling in coastal waters of southeastern U.S. during summer 1986

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Abstract:

Summer-time pelagic nitrogen recycling using an 15NH4+ tracer technique was studied for important biological pathways, sinks, and residence times in the microbial food web of coastal Georgia, U.S.A. Results showed that estimated rates of NH4+ regeneration by a variety of microheterotrophs and microzooplankton balanced rates of NH4+ assimilation by the microbial community, i.e., phytoplankton, bacteria and other microheterotrophs, in surface waters. In bottom water below the 1% light level, NH4+ regeneration exceeded community NH4+ assimilation by 3.5 times. However, over a period of 2 weeks, high NH4+ concentrations rarely occurred in bottom waters, and this was attributed to rapid mixing of the water column by winds and tides. Estimated mixing times from time-dependent numerical models were on the order of NH4+ turnover times of 5 to 10 hours. Overall, rates of community NH4+ assimilation exceeded rate estimates of phytoplankton N demand by 1.8 to 2.7 fold, which were made from rates of 14CO2 incorporation into proteins. In bottom samples where phytoplankton were light limited, rates of NH4+ assimilation exceeded the phytoplankton N demand by 3.6 to 11.1 fold. Calculations concerning the role of dissolved organic nitrogen in N cycling suggest that only 10% is recycled to NH4+ daily. This N could support 12 to 29% of the estimated phytoplankton N demand. Residence times of particulate nitrogen pools, based on rates of NH4+ regeneration, were on the order of 3–10 days. During summer-time hydrographic conditions and despite other losses, particulate nitrogen could recycle as often as 100 times before autumn removal processes occur off southeastern U.S.

Document Type: Research Article

Publication date: August 1, 1990

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  • The Journal of Marine Research publishes peer-reviewed research articles covering a broad array of topics in physical, biological and chemical oceanography. Articles that deal with processes, as well as those that report significant observations, are welcome. In the area of biology, studies involving coupling between ecological and physical processes are preferred over those that report systematics. Authors benefit from thorough reviews of their manuscripts, where an attempt is made to maximize clarity. The time between submission and publication is kept to a minimum; there is no page charge.
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