Carbon and Nitrogen Isotopic Ratios of the Seagrass Posidonia oceanica: Depth-related Variations

✍ Scribed by Lepoint, G.; Dauby, P.; Fontaine, M.; Bouquegneau, J.-M.; Gobert, S.

• Book ID: 118118759
• Publisher: Walter de Gruyter GmbH & Co. KG
• Year: 2003
• Tongue: English
• Weight: 148 KB
• Volume: 46
• Category: Article
• ISSN: 0006-8055
• DOI: 10.1515/bot.2003.058

✦ Synopsis

Nitrogen (δ 15 N) and carbon (δ 13 C) isotopic compositions of Posidonia oceanica were determined during three seasons along a bathymetric gradient (4-38 m depth). The δ 15 N values are low (2.2±0.9 ‰) and variable. They do not show any relation to depth or sampling dates. There is a significant difference between the δ 15 N values of the youngest and the oldest leaves, probably as a result of N resorption and senescing during leaf ageing. The δ 13 C values of young Posidonia leaves vary with depth, showing the relationship between δ 13 C values and primary productivity rate, and the use of a bicarbonate/CO 2 mixture as an inorganic carbon source. The δ 13 C values of the oldest P. oceanica leaves are depleted in 13 C compared to those of young leaves. This modification of the 13 C signatures in relation to leaf age is particularly important between 20 and 29 m depth. This modification could be related to photosynthetic rate change during ageing, but also to change in carbohydrate composition and content.