IR Home
MEPS
Home
Editors
Forthcoming
Information
Subscribe
Journals
Home
MEPS
AME
CR
DAO
ESEP
Search
Subscribe
Book Series
EE Books
Top Books
ESEP Books
Order
EEIU Brochures
(pdf format)
Discussion Forums
Home
Research
Endangered Species Programs
Institutions
International Ecology Institute
Eco-Ethics International Union
Foundation
Otto Kinne Foundation
| |
MEPS 264:31-48 (2003)
|
Abstract
|
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
Published in MEPS Vol.
264
(2003) on December 15
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2003
|