THE RELATIVE IMPORTANCE OF WATER MOTION ON NITROGEN UPTAKE BY THE SUBTIDAL MACROALGA ADAMSIELLA CHAUVINII (RHODOPHYTA) IN WINTER AND SUMMER1 |
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Authors: | Louise T Kregting Catriona L Hurd Conrad A Pilditch Craig L Stevens |
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Institution: | 1. Department of Botany, University of Otago, PO Box 56, Dunedin, New Zealand;2. Author for correspondence: e‐mail .;3. Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand;4. National Institute for Water and Atmospheric Research, PO Box 14, Wellington, New Zealand |
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Abstract: | The influence of seawater velocity (1.5–12 cm · s?1) on inorganic nitrogen (N) uptake by the soft‐sediment perennial macroalga Adamsiella chauvinii (Harv.) L. E. Phillips et W. A. Nelson (Rhodophyta) was determined seasonally by measuring uptake rate in a laboratory flume. Regardless of N tissue content, water velocity had no influence on NO3? uptake in either winter or summer, indicating that NO3?‐uptake rate was biologically limited. However, when thalli were N limited, increasing water velocity increased NH4+ uptake, suggesting that mass‐transfer limitation of NH4+ is likely during summer for natural populations. Uptake kinetics (Vmax, Ks) were similar among three populations of A. chauvinii at sites with different mean flow speeds; however, uptake rates of NO3? and NH4+ were lower in summer (when N status was generally low) than in winter. Our results highlight how N uptake can be affected by seasonal changes in the physiology of a macroalga and that further investigation of N uptake of different macroalgae (red, brown, and green) during different seasons is important in determining the relative influence of water velocity on nutrient uptake. |
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Keywords: | Adamsiella chauvinii ammonium nitrate nitrogen uptake subtidal macroalgae water velocity |
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