Project: Temporal and spatial scales of variability in bivalve connectivity

Temporal and spatial scales of variability in bivalve connectivity

Larval connectivity, the extent to which sub-populations exchange larvae, has emerged as a fundamental concept within the diverse arenas of population ecology, biotic resource management, biodiversity conservation, invasive species control, and habitat restoration. However, determining dispersal trajectories of larvae and their scales of variability remain a major challenge. Project investigators Levin, Muccino and Rasmussen will use an integration of prospective modeling and retrospective (elemental fingerprinting) approaches to assess variability in larval connectivity and its demographic consequences for mytilid mussel populations in southern California. This project builds on initial studies of mytilid connectivity to address in greater depth and with a more strongly coupled physical/biological approach, questions of variability and its causes.

These collaborating scientists will address hypotheses concerning the spatial and temporal scales of connectivity for mussels, Mytilus californianus and Mytilus galloprovincialis, examining their consistency among sites and species. This will be accomplished through (a) larval out-planting at 18 locations in San Diego County several times a year to generate reference signatures for trace elemental fingerprinting, (b) collection of recruits and elemental analyses of their larval shells to determine sites and regions of origins, and (c) high frequency data collection at 2 bay locations for M. galloprovincialis and 2 open coast locations for M. californianus to carry out weekly analysis of recruitment variability, its link to chemical signals and recruit origins, and for collection of demographic data (size-specific survivorship, growth and fecundity).

Through numerical dispersal simulations of the coastal ocean and bays, and subsequent comparisons to fingerprinting based assessment of recruit origins, they will examine the roles of circulation, local vs. remote forcing, bay-ocean interaction, episodic events, and larval attributes (vertical behavior, release times, planktonic duration) in defining the variability of connectivity. Demographic data will be combined with connectivity data to model the population and meta-population level fitness consequences of observed mytilid connectivity patterns.

The results of connectivity studies have direct applicability to conservation and management of commercial and natural bivalve populations, and given the key structural role of mussels, to the conservation of rocky shore habitats.