Parasites and ecosystem ecology

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ResearchBlogging.org OK. I'll admit it. I don't think about parasites much. In fact, I probably wouldn't think about them at all if it weren't for my friend and colleague, Janine Caira, who right now is in Borneo collecting tapeworms from sharks, skates, and rays and who just received a grant from the NSF Planetary Biodiversity Inventories program for a survey of worldwide tapeworm biodiversity. Why do I mention this? Because I suspect I'm pretty typical. We all know that most plants and animals have parasites, but we tend to forget about them. When we do think about them we tend to think that they don't matter that much (so that we can go on ignoring them). Well, I don't think I'll be able to do that any more.

One of Janine's students, Maria Pickering, is a co-author on a paper that just appeared in Nature. The authors found that "parasite biomass exceeded that of top predators". They show that parasites matter and that they matter a lot.
nature06970-f1.2.jpgBiomass of parasites relative to the total biomass of different animal groups in three estuaries. (from Kuris et al. Nature 454:515-518; 2008)
The authors studied three estuaries on the Pacific coast of California and Baja California for five years. In each estuary they estimated both the total biomass in each group and the fraction of the total biomass accounted for by parasites. The graph to the left shows the results. Total biomass of both trophically transmitted and castrator parasites was between 1 and 10 kg per hectare across the three estuaries. The biomass of winter birds in these same estuaries was 4.1 kg per hectare, which includes most of the top predators. There's as much mass of parasites in these ecosystems as there is of birds.

Wow! I never would have guessed that. But it's hard to argue with the conclusion:

The substantial biomass and productivity attributed to parasites in these estuaries calls for the full integration of parasite ecology into the general body of ecological theory.
UPDATE: Maria just e-mailed me to tell me that Armand Kuris was interviewed about the study on NPR.1

1Kuris was Maria's undergraduate advisor/mentor.
Kuris, A.M., Hechinger, R.F., Shaw, J.C., Whitney, K.L., Aguirre-Macedo, L., Boch, C.A., Dobson, A.P., Dunham, E.J., Fredensborg, B.L., Huspeni, T.C., Lorda, J., Mababa, L., Mancini, F.T., Mora, A.B., Pickering, M., Talhouk, N.L., Torchin, M.E., Lafferty, K.D. (2008). Ecosystem energetic implications of parasite and free-living biomass in three estuaries. Nature, 454(7203), 515-518. DOI: 10.1038/nature06970

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