Linking ecological connectivity to population resilience in a marine system

The ecosystems of our planet are changing at an unprecedented rate due to multiple, co-occurring pressures from human activities, such as climate warming, habitat degradation, and invasions by non-native species. In theory, the ability of species distributed in patches to persist through changing conditions and to exhibit resilience to pressures may depend in part on the movement of individuals between patches, which enables replenishment of local populations. This theory has been developed and applied mainly to terrestrial systems; supporting empirical evidence is largely lacking in the marine environment. In the ocean, unlike on land, physical boundaries impeding individual movement generally are absent, and this may limit the applicability of current theory in marine systems. We propose to examine the conditions under which dispersal of individuals (referred to as connectivity) affects the persistence and resilience of marine populations, using kelp beds as a model system. Kelp beds are highly productive coastal marine ecosystems that provide habitat for a wide range of invertebrates and fishes. Dispersal distance of individual kelps is less than the distance between kelp patches, while dispersal distances of resident invertebrates are much greater. Thus, conditions under which movement regulates population persistence are expected to vary between the habitat engineer (kelp) and species it supports. We will evaluate the importance of the size of a patch that a population occupies, and the distance between patches that individuals need to traverse, in the persistence and resilience of kelps and an invasive invertebrate that attaches and grows on the kelps. To achieve this, we will use historical data collected in the last 30 years to parameterize population models and experimental manipulations in the field. Understanding the role of connectivity on ecological timescales is essential for predicting shifting ranges and population extinctions. Using kelp beds as a tractable model system, our research will advance our understanding of resilience of a highly valuable coastal ecosystem and service provisioner, currently under pressure by ocean warming and invasive species. Establishing networks of Marine Protected Areas is the most common marine conservation action, in which connectivity is considered a key design element. Our findings will contribute to ongoing local and global discussions by providing specific recommendations on the conditions (species traits, habitat types) under which to incorporate connectivity in the design process.