Seasonal changes in C, N and major organic compounds and their significance to morpho-functional processes in the endemic Antarctic brown alga Ascoseira mirabilis |
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Authors: | I Gómez C Wiencke |
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Institution: | (1) Alfred-Wegener-Institut für Polar- und Meeresforschung, Am Handelshafen 12, D-27515 Bremerhaven, Germany Fax: 0049 (471) 4831 149; e-mail: cwiencke@awi-bremerhaven.de, DE |
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Abstract: | The seasonal and intra-thallus variations in the contents of C, N, proteins and amino acids, as well as in the storage carbohydrates
mannitol and laminaran, were measured in the endemic Antarctic brown alga Ascoseira mirabilis between September and February and related to seasonal changes in dark respiration and photosynthesis. Carbon contents between
31 and 37% DW were relatively constant throughout these months and no variations were detected among thallus regions. Nitrogen
contents, by contrast, were higher in September/October (3.1% DW) and decreased in January and February (1.8% DW). In general,
the basal regions had the lower N contents. Proteins reached maximum values of 13% DW in November and February and were inversely
correlated to photosynthesis (net Pmax). The amino acid content was also higher in October and November (maxima close to 10% DW), but low between December and February
(close to 5% DW), probably related to a seasonal pattern of N allocation in the alga. The storage carbohydrates mannitol and
laminaran exhibited inverse seasonal changes: low mannitol values close to 5% DW in September were coupled with high laminaran
contents varying between 7 and 15% DW. The existence of high laminaran contents in the distal blade region during September
and February suggests that this compound was effectively accumulated in this region. The low P/R ratios in spring and the
existence of a significant relationship between mannitol content and seasonal photosynthetic activity in the basal region
appear to support the hypothesis of a possible utilization of carbohydrates to power growth in A. mirabilis.
Received: 7 November 1996 / Accepted: 28 August 1997 |
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