Natural Isotopic Composition of Carbon (δ¹³C) Correlates with Colony Size in the Planktonic Cyanobacterium Gloeotrichia echinulata

• Published in: Limnology and oceanography 2009-05, Vol.54 (3), p.925-929
• Main Authors: Vuorio, Kristiina, Meili, Markus, Sarvala, Jouko
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Earth sciences; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; Geovetenskap; NATURAL SCIENCES; NATURVETENSKAP; Synecology
• ISSN: 0024-3590; 1939-5590; 1939-5590
• DOI: 10.4319/lo.2009.54.3.0925

To assess variability in carbon isotope signatures (δ¹³C) between and within populations under natural conditions, with a particular emphasis on colony size, we repeatedly collected planktonic colonies of a freshwater cyanobacterium Gloeotrichia echinulata in two lakes, Pyhäjärvi (southwest Finland) and Erken (southeast Sweden). Despite substantial differences in the average δ¹³C signature of Gloeotrichia between lakes (–6.9‰ in Pyhäjärvi and –20.7‰ in Erken), a similar, systematic increase in δ¹³C with colony size was observed in both lakes (of 2–3‰ in Pyhajarvi and 3–5‰ in Erken). This suggests declining isotope fractionation with increasing colony size, probably related to diffusion limitation of carbon availability. Temporal variation explained a minor fraction of total subsample variability (range δ¹³C ~4‰ in Pyhäjärvi and ~6‰ in Erken). Isotopic ¹³C fractionation in Gloeotrichia was likely affected both by carbon source and by colony size.