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Using Bayesian Stable Isotope Mixing Models to Enhance Marine Ecosystem Models
Citation:
Pacella, S., N. Niquil, P. Richard, AND T. H. DEWITT. Using Bayesian Stable Isotope Mixing Models to Enhance Marine Ecosystem Models. Presented at Pacific Estuarine Research Society, Astoria, OR, March 03 - 05, 2011.
Impact/Purpose:
The use of stable isotopes in food web studies has proven to be a valuable tool for ecologists.
Description:
The use of stable isotopes in food web studies has proven to be a valuable tool for ecologists. We investigated the use of Bayesian stable isotope mixing models as constraints for an ecosystem model of a temperate seagrass system on the Atlantic coast of France. δ13C and δ15N isotope data from the system was used in Bayesian mixing models (SIAR) to estimate the relative contribution of diet sources to food web compartments. The ranges of these diet contributions were then translated as inequality constraints into an inverse analysis model of the seagrass ecosystem. We hypothesized that incorporating the diet information gained from the atable isotope information would result in a more constrained and ecologically meaningful food web model. In order to test this, two standard inverse analysis models were created of the seagrass system. The models were identical, with the exception of one model including the diet constraints from the bayesian stable isotope mixing models. The models were run using a Markov Chain Monte Carlo technique for 25,000 solutions each. Comparisons between the output of the models show that the addition of the isotopic diet constraints further constsrained the solution range of all food web flows on average by over 30%. Flows that were directly affected by an isotopic diet constraint were 57% further constrained on average. These initial results confirm our hypothesis, while also showing the benefit of utilizing stable isotope information in ecosystem models. The relative importance of phytoplankton, seagrass, and microphytobenthos production to the system was also investigated. The food web of the seagrass bed was found to be most dependent on the production by microphytobentos. Further analysis of the models I being carried out to investigate effects of the stable isotope information on model output structure and function.