Dissolved inorganic nitrogen composition, transformation, retention and transport in naturally phosphate-rich and phosphate-poor tropical streams.
Abstract: The composition,
transformation, and transport of dissolved inorganic nitrogen (DIN) was
compared in waters associated with two lowland streams in Costa Rica. The
Salto River is enriched by geothermal-based soluble reactive phosphorus
(SRP), which raises the concentration up to 200 mug/L whereas Pantano Creek,
an unimpacted tributary, has an SRP concentration <10 mg/L. Ammonium
concentration in springs adjacent to the Salto and Pantano was typically
greater than channel water (13 of 22 locations) whereas nitrate concentration
was less (20 of 22 locations). Ground waters were typically high in ammonium
relative to nitrate whereas channel waters were high in nitrate relative
to ammonium. Sediment slurry studies indicated nitrification potential
in two sediment types, firm clay (3.34 mg N.cm-3.d-1) and uncompacted organic-rich
sediment (1.76 mg N.cm-3.d-1). Ammonium and nitrate amendments to each
stream separately resulted in nitrate concentrations in excess of that
expected after correction for dilution using a conservative tracer. SRP
concentration was not affected by DIN amendment to either stream. SRP concentration
in the Pantano appeared to be regulated by abiotic sediment exchange reactions
whereas DIN composition and concentration were regulated by a combination
of biotic and abiotic processes.
Triska, F. J., C. M. Pringle, G. Zellweger, J. H. Duff and R. J. Avanzino. 1993. Dissolved inorganic nitrogen composition, transformation, retention and transport in naturally phosphate-rich and phosphate-poor tropical streams. Canadian Journal of Fisheries and Aquatic Sciences 50: 665-675.
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