Uptake kinetics and storage capacity of dissolved inorganic phosphorus and corresponding N:P dynamics in Ulva lactuca (Chlorophyta) |
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Authors: | Alexander Lubsch Klaas Timmermans |
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Institution: | 1. NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems, Utrecht University, Yerseke, the Netherlands;2. Department Ocean Ecosystems, University of Groningen, Groningen, the Netherlands |
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Abstract: | Dissolved inorganic phosphorus (DIP ) is an essential macronutrient for maintaining metabolism and growth in autotrophs. Little is known about DIP uptake kinetics and internal P‐storage capacity in seaweeds, such as Ulva lactuca (Chlorophyta). Ulva lactuca is a promising candidate for biofiltration purposes and mass commercial cultivation. We exposed U. lactuca to a wide range of DIP concentrations (1–50 μmol · L?1) and a nonlimiting concentration of dissolved inorganic nitrogen (DIN ; 5,000 μmol · L?1) under fully controlled laboratory conditions in a “pulse‐and‐chase” assay over 10 d. Uptake kinetics were standardized per surface area of U. lactuca fronds. Two phases of responses to DIP ‐pulses were measured: (i) a surge uptake (VS ) of 0.67 ± 0.10 μmol · cm?2 · d?1 and (ii) a steady state uptake (VM ) of 0.07 ± 0.03 μmol · cm?2 · d?1. Mean internal storage capacity (ISCP ) of 0.73 ± 0.13 μmol · cm?2 was calculated for DIP . DIP uptake did not affect DIN uptake. Parameters of DIN uptake were also calculated: VS = 12.54 ± 1.90 μmol · cm?2 · d?1, VM = 2.26 ± 0.86 μmol · cm?2 · d?1, and ISCN = 22.90 ± 6.99 μmol · cm?2. Combining ISC and VM values of P and N, nutrient storage capacity of U. lactuca was estimated to be sufficient for ~10 d. Both P and N storage capacities were filled within 2 d when exposed to saturating nutrient concentrations, and uptake rates declined thereafter at 90% for DIP and at 80% for DIN . Our results contribute to understanding the ecological aspects of nutrient uptake kinetics in U. lactuca and quantitatively evaluating its potential for bioremediation and/or biomass production for food, feed, and energy. |
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Keywords: | nitrate uptake phosphate uptake storage capacity
Ulva lactuca
uptake kinetics |
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