Source-sink dynamics may define the patterns in distribution and abundance of many marine and estuarine species. In source habitats there is a demographic surplus (births + emigration > deaths + immigration), whereas in sinks a demographic deficit (deaths + immigration > births + emigration) leads to local extinction, without immigration from sources. Moreover, total production in linked sources and sinks may be higher than in either alone, due to subsidies to sinks by emigrants from sources. Hypotheses based on source sink dynamics implicitly incorporate recruitment processes, physical transport mechanisms, dispersal behavior, post settlement demography and habitat heterogeneity across various scales of space and time. Many of the current paradigms of marine ecology can be subsumed or applied within the conceptual framework of source sink dynamics. Matrix population models that incorporate spatial heterogeneity, age or stage structure, and dispersal provide a theoretical construct for the generation of hypotheses to test source sink dynamics in the field. The investigators will perform a comprehensive experimental investigation of source sink dynamics in a model system for marine and estuarine species. They will use extensive population data and a stage structured, spatially explicit matrix population model with dispersal to generate testable hypotheses concerning survival, growth, reproduction and dispersal between subpopulations in putative source and sink habitats. Mesocosm flume experiments will begin to examine the mechanisms underlying the dynamics, with particular regard to post settlement dispersal and reproductive success in relation to food and population density, respectively. Matrix models will be used to evaluate the importance of dispersal, and stage specific growth, survival and fecundity to population growth rate in linked and independent source and sink habitats. This research represents a comprehensive test of the existence and consequences of source sink dynamics in a marine system.