Changing seascapes, stochastic connectivity and marine metapopulation dynamics

Background/Question/Methods

The probability of dispersal from one habitat patch to another is a crucial quantity in our efforts to understand and predict the dynamics of natural populations. Unfortunately, an often overlooked property of this potential connectivity is that it may change with time. In the marine realm, transient landscape features such as mesoscale eddies and along-shore jets produce potential connectivity that is highly variable in time. We assess the impact of this temporal variability by comparing simulations of nearshore metapopulations dynamics when potential connectivity is constant through time (i.e. when it deterministic) and when it varies in time (i.e. when it is stochastic). We use mathematical analysis to reach general conclusions, and realistic biophysical modeling to determine the actual magnitude of these changes for a specific system - nearshore marine species in the Southern California Bight.

Results/Conclusions

We find that in general the temporal variability of potential connectivity affects two important quantities: metapopulation growth rates when the species is rare and equilibrium abundances. Our biophysical models reveal that stochastic outcomes are almost always lower than their deterministic counterparts, sometimes by up to 40%. Further, we identify groups of synchronized connections that are responsible for the difference between stochastic and deterministic outcomes. These results have implications for a how we use spatial information, such as connectivity, to manage nearshore (and other) systems.