Distribution of phyto- and bacterioplankton growth and biomass parameters, dissolved inorganic nutrients and free amino acids during a spring bloom in the Oosterschelde basin, The Netherlands

Publisher Website
Google Scholar
Abstract
Distribution of phtyo- and bacterioplankton growth and biomass parameters were followed during a spring bloom in the marine Oosterschelde basin, Netherlands. Several other biotic and abiotic parameters were measured. During the measuring period from April 4 until June 4, concentrations of the dissolved nutrients silicate, ammonium and nitrate decreased, while dissolved phosphate tended to increase. Concentrations of chlorophyll a increased with a distinct maximum in mid May during a bloom of the haptophycean Phaeocystis pouchetii. In the shallower part of the basin maxima of particulate primary production and bacterioplankton production were reached at the end of April during mixed bloom of diatoms of the genera Cryptomonas, Skeletonema and Thalassiosira as well as small flagallates. In the central basin, the most pronounced particulate primary production was observed during the P. pouchetii bloom. Relatively low percentages of extracellular release of total primary production were observed during and after this bloom. Percentage of bacterial incorporation of total exudates was high at the beginning of the experiment and decreased until the P. pouchetii bloom, when it increased again. Maximum bacterial productivities and biomasses were recorded during the decline of the P. pouchetii bloom. Overall O2 consumption rates seemed to be determined by phytoplankton biomass and by bacterioplankton production, but not by phytoplankton production or bacterioplankton biomass. Concentrations of dissolved free amino acids (DFAA) tended to decrease until the end of the large P. pouchetii bloom when an increase was observed; lowest concentrations were during this bloom. Alanine, aspartate, glycine, leucine and serine were always quantitatively the most important amino acids: during the P. pouchetii bloom also glutamate. Mole percentages of aspartate and methionine increased at the end of this bloom.