ABSTRACT: The leakage of urea, ammonium, dissolved organic nitrogen, and dissolved organic carbon from Zostera marina root-rhizomes during different porewater extractions was examined. In addition, the concentrations of these compounds were measured in root-rhizomes to estimate the potential leakage from root-rhizomes during sediment handling. The concentrations of ammonium, urea, and dissolved organic nitrogen in root-rhizomes were 22 to 51 times higher than the respective average porewater concentrations within the upper 5 cm of the sediment. Up to 70% of the compounds in question leaked from root-rhizomes during sediment handling, with a resultant, up to 8-fold, increase in the respective porewater concentrations. The porewater concentrations of ammonium, urea, and dissolved organic nitrogen and carbon were on average overestimated by a factor of 2 within the upper 5 cm of the sediment due to leakage from root-rhizomes. Thus, it is recommended that roots and rhizomes are removed from the sediment before porewater extraction by conventional methods.

KEY WORDS: Zostera marina · Roots · Rhizomes · Sediment · Porewater · Leakage · Nitrogen · Carbon

Published in AME Vol. 16, No. 3 (1999) on February 24
ISSN: 0948-3055. Copyright © Inter-Research, Oldendorf/Luhe, 1999