SEASONAL-VARIATIONS IN CONCENTRATION AND MICROBIAL UPTAKE OF METHYLAMINES IN ESTUARINE WATERS

Concentrations and heterotrophic uptake rates of monomethylamine, dime thylamine, and trimethylamine in estuarine seawater were measured. The re was a strong seasonal variation in the abundance and biological upt ake of these compounds. Both concentrations and heterotrophic uptake r ates of the 3 methylamines (MA) are higher in summer than in winter. T urnover times of the MA are shorter in summer (several hours) than in winter (thousands of hours). DMA is the most abundant (15 to 180 nM) a nd has the fastest uptake rate (0.1 to 12 nM h-1), while MMA and TMA h ave lower concentrations (5 to 60 nM) and slower uptake rates (0.01 to 2.4 nM h-1). Uptake rates of MA were not inhibited by addition of 1 m uM ammonium. Changes in seasonal distributions of MA and their uptake rates suggest that biological production of MA is greatest in the summ er months and is lower in the winter.