Nitrogen ecophysiology of intertidal seaweeds from New Zealand: N uptake, storage and utilisation in relation to shore position and season

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 264:31-48 (2003) - doi:10.3354/meps264031 Nitrogen ecophysiology of intertidal seaweeds from New Zealand: N uptake, storage and utilisation in relation to shore position and season J. C. Phillips1,2,*, C. L. Hurd1 1Department of Botany, University of Otago, PO Box 56, Dunedin, New Zealand 2Present address: CSIRO Marine Research, Private Bag No. 5, Wembley, Western Australia 6913, Australia *Email: julia.phillips@csiro.au ABSTRACT: The nitrogen ecophysiology of 4 intertidal seaweeds (Stictosiphonia arbuscula, Apophlaea lyallii, Scytothamnus australis, Xiphophora gladiata) from southeastern New Zealand is described in terms of N status, N uptake rates and N utilisation. The species growing in the highest shore position had large internal NO3- and NH4+ pools. For all species, tissue NH4+ pools were greater than tissue NO3- pools. Total tissue N was directly related to shore position with high intertidal species having highest tissue N, while the opposite trend was observed for C:N ratios. The ability to take up inorganic (NO3-, NH4+) and organic (urea) N when one or all N forms were present in the culture medium was measured using time-course uptake experiments at initial concentrations of 5 and 30 µM. Nitrate uptake did not vary over time for any of the species. S. arbuscula and S. australis exhibited a surge phase of NH4+ uptake at both concentrations. Urea uptake at 5 µM was generally low and consistent over time; uptake at 30 µM was highly variable. All species were capable of simultaneous uptake of all N forms. The relative importance of each N form to overall N nutrition indicated that NH4+ was an important N source in winter for all species. Urea was an important N source in summer, contributing 27 to 33% to the total N acquisition for most species. A relative preference index indicated that in winter N sources were utilised in the order NH4+ > NO3- > urea, while in summer the order was NH4+ = NO3- > urea. Estimates of the amount of N that each species could acquire during a tidal cycle indicated that the high intertidal S. arbuscula had the greatest capacity for N acquisition, regardless of season. KEY WORDS: Macroalgae · Intertidal seaweed · Nitrogen uptake · Nitrate · Ammonium · Urea · Season · Zonation · New Zealand Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 264. Online publication date: December 15, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.