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- Title
Seasonal variations in nitrate reductase activity and internal N pools in intertidal brown algae are correlated with ambient nitrate concentrations.
- Authors
YOUNG, ERICA B.; DRING, MATTHEW J.; SAVIDGE, GRAHAM; BIRKETT, DARYL A.; BERGES, JOHN A.
- Abstract
Nitrogen metabolism was examined in the intertidal seaweeds Fucus vesiculosus, Fucus serratus, Fucus spiralis and Laminaria digitata in a temperate Irish sea lough. Internal NO3- storage, total N content and nitrate reductase activity (NRA) were most affected by ambient NO3-, with highest values in winter, when ambient NO3- was maximum, and declined with NO3- during summer. In all species, NRA was six times higher in winter than in summer, and was markedly higher in Fucus species (e.g. 256 ± 33 nmol NO3- min−1 g−1 in F. vesiculosus versus 55 ± 17 nmol NO3- min−1 g−1 in L. digitata). Temperature and light were less important factors for N metabolism, but influenced in situ photosynthesis and respiration rates. NO3- assimilating capacity (calculated from NRA) exceeded N demand (calculated from net photosynthesis rates and C : N ratios) by a factor of 0.7–50.0, yet seaweeds stored significant NO3- (up to 40–86 µmol g−1). C : N ratio also increased with height in the intertidal zone (lowest in L. digitata and highest in F. spiralis), indicating that tidal emersion also significantly constrained N metabolism. These results suggest that, in contrast to the tight relationship between N and C metabolism in many microalgae, N and C metabolism could be uncoupled in marine macroalgae, which might be an important adaptation to the intertidal environment.
- Subjects
IRISH Sea; PLANT metabolism; MARINE algae; NITROGEN; FUCUS; LAMINARIA; MICROALGAE; INTERTIDAL organisms; NITRATES
- Publication
Plant, Cell & Environment, 2007, Vol 30, Issue 6, p764
- ISSN
0140-7791
- Publication type
Article
- DOI
10.1111/j.1365-3040.2007.01666.x