Document: SAM-3-78-1

Assessing the individual and population level effects of a disturbance using a dynamic state variable model.

FORDE, S.*

University of California, Santa Cruz, CA 95064, USA ¹

Abstract:
Empirically addressing the influence of a disturbance at both the individual and population level is often logistically unfeasible. Modeling provides a format in which such effects can be addressed at a number of scales, which would be intractable using experiments. I present the results of a dynamic state variable model developed to assess how the probability of a disturbance, specifically an oil spill, influences the life history trade-off between growth and reproduction in an intertidal invertebrate. I used the results of the individual model to address how the probability of oiling in a source population interacts with recruitment variation to influence the dynamics of a focal population. The model predicted that increased exposure to oil results in earlier age and/or size of reproduction and reduced lifespan. Surprisingly, there was very little difference in individual fecundity and the total reproductive output of the population under low and high probabilities of oiling. However, when different probabilities of oiling were combined with variation in recruitment, differences between the dynamics of impacted and non-impacted populations were considerable. This result points toward a need for further research quantifying the amount of recruitment to open populations if we are to accurately evaluate the effects of disturbances.

Keywords: dynamic state variable model, rocky intertidal, Chthamalus fissus, disturbance, life history trade-off, recruitment dynamics, population model

This abstract is being presented at: 2:30 PM in session:
Oral Session #46: Modeling Populations and Statistical Ecology.