Temporal and spatial variability in phytoplankton ammonium and nitrate uptake in the Delaware Estuary |
| |
Authors: | Jonathan R Pennock |
| |
Institution: | 1. Dept. Geología, Universidad de Oviedo, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain;2. Geological Institute, NO G59, Department of Earth Sciences, Sonneggstrasse 5, ETH, 8092 Zurich, Switzerland;3. Lamont Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA;4. Marine Research Centre, Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia;1. Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain;2. Centre for Ecology and Evolution in Microbial Model Systems – EEMiS, Linnaeus University, SE-39182 Kalmar, Sweden;3. IIM-CSIC, Insituto de InvestigaciónsMariñas, Eduardo Cabello 6, 36208 Vigo, Spain;4. School of Environmental Science, University of East Anglia, Norwich NR4 7TJ, UK;1. Mountain Research Centre (CIMO), School of Agriculture, Polytechnic Institute of Bragança, Campus of Santa Apolónia, PO Box 1172, 5301-855 Bragança, Portugal;2. Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal;1. College of Materials Science and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China;2. Ocean College, Zhejiang University, Hangzhou 310058, China |
| |
Abstract: | Phytoplankton NH4+ and NO3− uptake was examined along the longitudinal salinity gradient of the Delaware Estuary over several seasonal cycles using 15N-tracer techniques. Saturated nitrogen uptake rates increased directly with water temperature and reached a maximum of 380 nmol Nl−1h−1 during summer. This temperature dependence was related primarily to changes in the rate of maximum chlorophyll specific uptake, which varied exponentially between 2 and 70 nmol N μg Chl h]−1 over a temperature range of 2–28°C. Despite these high uptake rates, balanced growth (C:N7:1) could be maintained over the diel light cycle only by highly efficient nitrogen uptake at low light intensities and dark uptake below the photic zone and at night (dark UPTAKE=25% maximum uptake).Ammonium fulfilled 82% of the annual phytoplankton nitrogen demand in the estuary despite dominance of NO3− in the ambient dissolved inorganic nitrogen pool. The predominance of NH4+ uptake occurred because of the general suppression of NO3− assimilation at NH4+ concentrations in excess of 2 μ
. This suppression, however, was not as universal as has been reported for other systems, and it is suggested that the extremely high NO3− concentrations found in the estuary contribute to this pattern. Nitrate was a significant source of nitrogen only during periods of high phytoplankton production in summer, and when NH4+ concentrations were low towards the end of the spring bloom. |
| |
Keywords: | Phytoplankton nitrogen plankton production uptake estuaries Delaware Bay |
本文献已被 ScienceDirect 等数据库收录! |
|