Distributions, cycling and recovery of amino acids in estuarine waters and sediments
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Acid hydrolysis of estuarine water samples for the determination of amino acids (AAs) was tested and found to be effective at high (250 μM) nitrate concentrations when the anti-oxidant, ascorbic acid, was added to the samples. Hydrolysable AA concentrations were then determined in surface sediments collected from low and high salinity regions of the Tamar Estuary (UK) during winter 2003 and 2004, and in overlying water when simulated resuspension of sediment particles was performed. Concentrations of AAs in sediment samples comprised <50% of particulate nitrogen, fitting the paradigm that most sedimentary nitrogen is preserved within an organic matrix. When sediment samples were resuspended in overlying water (salinity 17.5), the rapid, measured increase in dissolved AA concentrations almost equalled the reported nitrate concentration in the lower estuary, with the subsequent decrease in the total dissolved AA levels suggested that bacterial uptake was occurring. Our data concur with previous studies on nitrogen desorption from sediments and suggest that an understanding of organic nitrogen cycling will be an important aspect of future effective estuarine management.
KeywordsAmino acids Tamar estuary Particulate nitrogen Acid hydrolysis Recovery Nitrate-rich water Sediment Resuspension Bacterial uptake
We thank Andrew Tonkin for particulate carbon and nitrogen analyses and Patrick Allen and Stephanie Handley for help with the amino acid analyses. This study was funded by the Leverhulme Trust (grant F/00568/H), for which it is gratefully acknowledged.
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