Nitrogen recycling in coastal waters of southeastern US during summer 1986

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Journal of Marine Research (Sears Foundation for Marine Research); (United States)

DOI:https://doi.org/10.1357/002224090784984704· OSTI ID:7014376

Hanson, R B; Robertson, C Y; Yoder, J A; Verity, P G; Bishop, S S ^[1]

---

1. Skidaway Inst. of Oceanography, Savannah, GA (United States)

Summer-time pelagic nitrogen recycling using an {sup 15}NH{sub 4}{sup +} 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 NH{sub 4}{sup +} regeneration by a variety of microheterotrophs and microzooplankton balanced rates of NH{sub 4}{sup +} assimilation by the microbial community. In bottom water below the 1% light level, NH{sub 4}{sup +} regeneration exceeded community NH{sub 4}{sup +} assimilation by 3.5 times. However, over a period of 2 weeks, high NH{sub 4}{sup +} concentrations rarely occurred in bottom waters, and this was attributed to rapid mixing of the water column by winds and tides. Estimated mixing time from time-dependent numerical models were on the order of NH{sub 4}{sup +} turnover times of 5 to 10 hours. Overall, rates of community NH{sub 4}{sup +} assimilation exceeded rate estimates of phytoplankton N demand by 1.8 to 2.7 fold, which were made from rates of {sup 14}CO{sub 2} incorporation into proteins. In bottom samples where phytoplankton were light limited, rates of NH{sub 4}{sup +} 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 NH{sub 4}{sup +} daily. This N could support 12 to 29% of the estimated phytoplankton N demand. Residence times of particulate nitrogen pools, based on rates of NH{sub 4}{sup +} 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 US.

• DOE Contract Number: FG09-85ER60311; AS09-76EV00936
• OSTI ID: 7014376
• Journal Information: Journal of Marine Research (Sears Foundation for Marine Research); (United States), Journal Name: Journal of Marine Research (Sears Foundation for Marine Research); (United States) Vol. 48; ISSN 0022-2402; ISSN JMMRA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
560300 -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMMONIUM COMPOUNDS
AQUATIC ORGANISMS
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
COASTAL WATERS
DEVELOPED COUNTRIES
GEORGIA
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MATHEMATICAL MODELS
NITROGEN 15
NITROGEN CYCLE
NITROGEN ISOTOPES
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
PLANKTON
PRODUCTIVITY
SEASONAL VARIATIONS
SINKS
STABLE ISOTOPES
SURFACE WATERS
TIME DEPENDENCE
TRACER TECHNIQUES
USA
VARIATIONS