Urea degradation rates by size-fractionated plankton populations in a temperate estuary |
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| Institution: | 1. Southern California Coastal Water Research Project, Costa Mesa, CA, USA;2. University of California, Santa Cruz, CA, USA;3. Orange County Sanitation District, Fountain Valley, CA, USA;1. Institute of Marine Science and Technology, Shandong University, Jinan 250100, China;2. State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China;3. College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China;4. Key Laboratory of Global Change and Marine-Atmospheric Chemistry of State Oceanic Administration (SOA), Third Institute of Oceanography, SOA, Xiamen 361005, China;1. University of Vienna, Department of Ecogenomics and Systems Biology, Archaea Biology and Ecogenomics Division, Althanstrasse 14, A-1090 Wien, Austria;2. Uppsala University, Department of Cell and Molecular Biology, Science for Life Laboratory, Box 596, SE-75123, Uppsala, Sweden;1. Advanced Water Management Centre, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia;2. School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia;1. Physical Research Laboratory, Navrangpura, Ahmedabad, India;2. Centre for Marine Living Resources and Ecology, Ministry of Earth Sciences, Kendriya Bhavan, Kakkanad, Cochin, India;3. Department of Marine Sciences, University of Gothenburg, Göteborg, Sweden;4. College of Fisheries, Karnataka Veterinary, Animal & Fisheries Sciences University, Mangalore, India;5. Department of Science, Kristianstad University, Kristianstad, Sweden;6. WEAQ Lab, Ängelholm, Sweden |
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| Abstract: | The distribution of the rates of remineralisation and assimilation of labelled urea by bacteria was determined in a temperate estuary in winter and related to the activities of planktonic populations separated by filtration into a large fraction (LF > 3 μm) and small fractions (SF < 3 μm). A significant relationship was established between remineralisation activity of the SF in situ and the ambient urea concentrations, whereas corresponding relationships between the LF in situ and urea concentrations were inconsistent. A series of comparable artificial dilution experiments demonstrated consistent effects of salinity on rates of urea remineralisation with opposing relationships observed for the LF and SF. However interpretation of the data obtained from the in situ samples in relation to those obtained experimentally indicated only minimal control of the in situ rates of urea remineralisation by salinity, thus confirming the greater influence on these rates of the ambient urea concentrations. Remineralisation activity was approximately an order of magnitude greater than the assimilation activity with no clear trends being shown between assimilation rates and environmental variables. Highest ambient concentrations of urea were consistently recorded adjacent to the freshwater inflow. |
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