Dissolved organic nitrogen dynamics and bacterial amino acid metabolism in Castle Lake, California
Heterotrophic bacterioplankton can play an important role in the mineralization of dissolved organic nitrogen (DON) in aquatic ecosystems. During the summer growing season, dissolved inorganic nitrogen in the epilimnion of Castle Lake is often below detection, thus phytoplankton production is dependent upon N-regeneration mechanisms. The specific objectives were threefold: (1) analyze seasonal variation of dissolved organic nitrogen in relation to primary productivity and biomass, (2) determine the fraction of dissolved organic nitrogen composed of dissolved free amino acids, and (3) determine mineralization rates of amino acid nitrogen. The concentration and composition of DON varied seasonally. Dissolved free amino acids comprised 5-8% of the DON. Sediment release appeared to be the most important source of the observed increase of DON. The mineralization of amino acid carbon and nitrogen was measured with /sup 14/C- and /sup 15/N-labeled amino acids. Total amino acid nitrogen flux was calculated and a conservative estimate showed that amino acid mineralization could supply a minimum of 2% of the phytoplankton N-requirements. However, amino acids are only one component of DON and there are many other substrates available for bacterial mineralization. Further research on the differential carbon and nitrogen metabolism of other components of DON are still needed. This approach provides useful information on the role of DON in the nitrogen dynamics of aquatic ecosystems.
- Research Organization:
- California Univ., Davis (USA)
- OSTI ID:
- 5942764
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
AMINO ACIDS
MINERALIZATION
LAKES
NITROGEN CYCLE
ORGANIC NITROGEN COMPOUNDS
ECOLOGICAL CONCENTRATION
AQUATIC ECOSYSTEMS
BACTERIA
CALIFORNIA
CARBON 14 COMPOUNDS
INFORMATION NEEDS
METABOLISM
NITROGEN 15
PHYTOPLANKTON
SEASONAL VARIATIONS
AQUATIC ORGANISMS
CARBOXYLIC ACIDS
ECOSYSTEMS
FEDERAL REGION IX
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MICROORGANISMS
NITROGEN ISOTOPES
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PLANKTON
STABLE ISOTOPES
SURFACE WATERS
USA
VARIATIONS
520200* - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)