JPR Advance Access originally published online on February 3, 2006
Journal of Plankton Research 2006 28(4):419-427; doi:10.1093/plankt/fbi130
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Monitoring microbial predatorprey interactions: an experimental study using fatty acid biomarker and compound-specific stable isotope techniques
1 British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK, 2 Scottish Association for Marine Science, Dunstaffnage Marine Laboratory Oban, Argyll PA37 1QA, UK and 3 Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, UK
* Corresponding Author: dwpo{at}bas.ac.uk
Received April 3, 2005; accepted in principle January 18, 2006; accepted for publication January 27, 2006; published online February 3, 2006
Communicating editor: K.J. Flynn
Naturally occurring microbial communities are complex, with autotrophs and heterotrophs often similarly sized and impossible to separate by conventional size fractionation approaches. However, if it was possible to identify specific compounds that are characteristic of particular groups of microbes and determine the stable isotope composition of these biomarkers, the requirement for size fractionation could potentially be negated. This work considered the usefulness of such an approach by analysis of a simple laboratory predatorprey system comprising Nanochloropsis oculata, an autotrophic flagellate prey and Oxyrrhis marina, a heterotrophic flagellate predator. In growth-grazing experiments the fatty acids 20:5(n3) and 22:6(n3) were used as biomarkers for N. oculata and O. marina respectively. Interpretation of
13C values of these predator and prey fatty acid biomarkers was not straightforward since although isotopic signature of the O. marina biomarker was consistently enriched compared to that of its N. oculata prey, the magnitude of enrichment in 13C increased with age of culture (1.05.4 %). Given the variability we observed in our experimental cultures, it will be difficult to apply this approach to complex field situations without a comprehensive understanding of the factors determining the
13C values of specific biomarker molecules.