SEMINAR: MBF 602 seminar- Marc Nadon Friday, April 30th, 2010 4:00pm S/A seminar room

[Cary Rios <crios@rsmas.miami.edu>]

The stable isotope ecology of subtidal food webs in northern Canada

In temperate and polar marine food webs, total primary production typically originates from

three sources: phytoplankton, kelp, and benthic microalgae. Since phytoplankton and benthic

algae often have different carbon stable isotope ratios (Î13C), past research efforts have used the

Î13C of consumers to infer on the relative important of these sources of primary production.

These studies have found that kelp detritus and/or benthic microalgae are important sources of

energy in these ecosystems (ex. 20-40% of total production). I examined the hypothesis that the

Î13C of benthic consumers is depleted in offshore, deeper waters where kelp and benthic

microalgae are absent by analysing the Î13C (and Î15N) of consumers in three settings (1) along a

nearshore-offshore gradient in the field, (2) in consumers placed in cages at various depths and

distances from shore, and (3) by re-examining published stable isotope values for consumers

taken at various depths from studies around the world. In all three situations, I did not observe

the predicted change in Î13C values of benthic consumers. In both the literature and in my field

measurements, the Î13C values for consumers were on average separated from the values for

suspended particulate organic matter by 4â, irrespective of depth, indicating that factors other

than the feeding on 13C-rich benthic primary producers may explain the enriched carbon ratios in

benthic consumers (e.g., selective feeding on enriched particles). The hypothesis that the high

Î13C ratio in suspension and deposit feeders reflects feeding on benthic primary producers is thus

tenuous and requires further investigation.

Marc Nadon

B.Sc. Biology

McGill University, Montreal, Canada

M.Sc. Marine Ecology

Laval University, Quebec City, Canada

Entered PhD: Fall 2009

Advisor: Dr. Jerry Ault

Cary Rios 
Graduate Studies Office
University of Miami
Rosenstiel School of Marine & Atmospheric Science

4600 Rickenbacker Cswy
S/A 132
Miami, FL 33149
Locator Code: VK
P. 305.421.4920
F. 305.421.4771
http://www.rsmas.miami.edu
crios@rsmas.miami.edu 

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