Biological cycling of nitrogen in a Rocky Mountain alpine lake, with emphasis on the physiological and ecological effects of acidification

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5672665

Angelo, R T

This study examined nitrogen cycling interactions occurring among the heterotrophic and autotrophic plankton of a softwater, oligotrophic alpine lake. Its major objectives were (1) to compare the influences of internal (regenerative) and external nitrogen supply processes on watercolumn primary production, (2) to identify the food web components contributing most to regenerative and assimilative fluxes of nitrogen, and (3) to evaluate the sensitivity of the limnetic nitrogen cycle to lake acidification. Field and laboratory experiments were based on isotopic tracer ({sup 15}N, {sup 14}C, {sup 3}H) methodologies plankton size-fractionation and metabolic inhibitor techniques, and short-term bioassay procedures; supporting data were gathered on lake physicochemical and biological properties. Measured aqueous nutrient concentrations, the results of {sup 14}CO{sub 2}-based snowmelt and nutrient enrichment bioassays, and physiological indicators of algal nutrient status collectively demonstrated that phytoplankton nitrogen demand greatly exceeded nitrogen supply. Both NH{sub 4}{sup +} and NO{sub 3}{sup {minus}} were quantitatively important forms of assimilatable nitrogen under ambient conditions. Mass balance considerations indicated that within-lake biogeochemical processes constituted a net sink for NO{sub 3}{sup {minus}}, whereas NH{sub 4}{sup +} production and consumption rates were approximately in balance on an ecosystem scale. Water-column regenerative and assimilative fluxes of NH{sub 4}{sup +} were strongly correlated. Meta- and protozooplankton were the principal sources of regenerated NH{sub 4}{sup +}; heterotrophic bacterioplankton were net consumers of NH{sub 4} {sup +}. Experimental reductions in metazooplankton populations markedly enhanced rates of NH{sub 4}{sup +} regeneration.

• Research Organization: Montana State Univ., Bozeman, MT (United States)
• OSTI ID: 5672665
• Country of Publication: United States
• Language: English

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ACID RAIN
ACIDIFICATION
AMMONIUM COMPOUNDS
ATMOSPHERIC PRECIPITATIONS
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CHEMICAL PROPERTIES
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL EFFECTS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LAKES
MOUNTAINS
NITRATES
NITROGEN COMPOUNDS
NITROGEN CYCLE
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLLUTION
RAIN
ROCKY MOUNTAINS
SURFACE WATERS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
WATER POLLUTION