ABSTRACT: Seagrass delta¹³C values reported in the literature show variation over a range of approximately 20o/oo. A frequency histogram constructed on the basis of the collected data set shows a unimodal distribution, with values between -10 and -11o/oo (relative to the PDB standard) found with the highest frequency. Seagrasses thus have stable carbon isotope signatures which are typically less depleted in ¹³C than those of other groups of aquatic primary producers. This points to a characteristic set of physiological, anatomical and perhaps environmental features shared by all seagrasses. A significant negative correlation exists between seagrass delta¹³C values and geographical latitude of the sampling location, indicating that from tropical to temperate regions seagrasses tend to become more ¹³C depleted. The physiological and environmental causes of variability are discussed. The most relevant environmental factors inducing variation in seagrass delta¹³C values appear to be, in order of decreasing importance, source carbon, irradiance and temperature. The integrated information reflected in the natural delta¹³C values of seagrasses can be used in support of the reconstruction of environmentally related growth dynamics on the scale of individual shoots and that of entire populations. In addition, ¹³C may be used experimentally as a tracer of carbon flow in short term carbon allocation and production studies.

KEY WORDS: Stable carbon isotopes · Seagrasses · Isotope signatures · Variability

Published in MEPS Vol. 140 (1996) on September 12
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996