Allochthonous Organic Carbon of a Marl Lake
Wetzel, Robert G.; Otsuki, Akira
published: Feb 27, 1974
ArtNo. ESP141007301004, Price: 29.00 €
Influxes of allochthonous dissolved (< 0.4, µm) and particulate (>0.4, µm) detrital organic carbon to a small hardwater lake were analyzed over an annual period in relation to their fate within and losses from the lake. Changes both in absolute concentration and on an annual volumetric basis were determined in inputs as the streams traversed through marshes, from groundwater, and of outlet losses. A detailed water budget of the lake was estimated by direct measurements. Groundwater inputs were determined by two independent methods (magnesium mass balance and winter flow characteristics) that agreed closely. Particulate organic carbon (POC) of influxes, within the lake basin, and in outflow water was ca. 10% of the dissolved organic carbon (DOC) fraction. Both POC and DOC surface inputs were minimal during the summer period of low precipitation and active marsh growth and increased markedly in the autumn and spring. POC and DOC concentrations of groundwater influxes were low but on an annual basis constituted over 25% of allochthonous input. Over half the amount of POC entering the lake allochthonously leaves the lake by outflow and represents about 5% of the gross production of POC of the lake. In contrast, much more DOC (net loss of 15g C m-2 year-1) is exported from the outflow than enters allochthonously and this output represents a major pathway of carbon removal from the lake. Humic fractions of DOC, analyzed by UV absorption and fluorescence of yellow organic acids, of influxes were similar to total DOC patterns and demonstrated a loss to the hypolimnion in part related to adsorption on CaCO3 precipitating during epilimnetic decalcification.