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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13096

Variability in stable isotope values of South African Laminariales, Ecklonia maxima and Laminaria pallida, over different spatial and temporal scales

David C. Dyer*, Mike J. Butler, Albertus J. Smit, Robert J. Anderson, John J. Bolton

*Corresponding author:

ABSTRACT: Kelp forests are some of the most productive habitats in the oceans, supporting diverse, ecologically and often commercially important ecosystems. This study of 8 geographically separate sites in 2 seasons highlights the natural variability of stable isotope values (δ13C and δ15N), at different spatial and temporal scales, within the 2 dominant kelp species along the west coast of South Africa. Additionally, stable isotope variability was investigated within and among different tissues within both kelp species. Within a kelp plant, δ13C values had a range of 1.7‰ for E. maxima and 1.5‰ for L. pallida. The δ15N values had a range of 3.8‰ for E. maxima and 4.2‰ for L. pallida. There were also consistent variability patterns along the length of a single frond in both species, for both isotopes. Among the localities, E. maxima and L. pallida were highly variable with ranges in δ13C (9.4‰ and 11.2‰) and δ15N (3.4‰ and 4.5‰) for the 2 species respectively. The δ13C values of L. pallida and E. maxima displayed a clear pattern coinciding with depth, particularly for L. pallida. Within-site variability was a major contributor to the overall spatial variability for both species. This study provides further evidence for the importance of understanding basal variability of stable isotope values when determining the carbon sources of bottom-up controlled ecosystems.