A seasonal study of amino acids in marine and estuarine waters
The fluram method for the analysis of amino acids was modified for use in sea and estuarine waters. No evidence for environmental coprecipitation of amino acids was found and any possible removal process from the Tamar estuary was most likely to be by some different mechanism. An HPLC method for the analysis of amino acids in natural waters suitable for shipboard use was developed. The method was used to determine the seasonal variation of amino nitrogen in coastal and estuarine waters in order to test the hypothesis that phytoplankton could use such compounds as a source of nutrient nitrogen when nitrate was absent. The levels found were generally an order of magnitude higher than those previously reported. This work has gone some way in accounting for some of the previously unidentified fraction of the total dissolved nitrogen in coastal waters. Similarities of amino acid spectra between coastal and estuarine waters were found and the dominant acids were serine, glycine tyrosine and ornithine. Tyrosine occurred very erratically. The patchy distribution, seasonal variation and levels of the dissolved free amino acids in coastal and estuarine waters may support the theory that phytoplankton use them as a source of nutrient nitrogen. Whilst it was not possible to show that the hypothesis was true it was considered likely that at least some amino acids might sometimes be utilised as nutrient nitrogen.