Collaborative Research: Connectivity in western Atlantic seep populations: Oceanographic and life-history processes underlying genetic structure

Intellectual Merit. This project integrates studies of oceanographic circulation, larval dispersal, invertebrate life histories, population genetics, and phylogeography to explore questions of contemporary and historical connectivity in relatively unexplored deep-sea chemosynthetic ecosystems. Five deep-sea seep systems in the Intra- American Sea (IAS) are targeted: Blake Ridge, Florida Escarpment, Alaminos Canyon, Brine Pool, Barbados (El Pilar, Orenoque A, Orenoque B). This project will evaluate connectivity on spatial scales that match those at which vent systems are being studied (3500 km), with a set of nested seeps (within the Barbados system) within which connectivity can be explored at more local spatial scales (30 to 130 km), and with species that span depth (600 m to 3600 m) and geographic ranges (30 km to 3500 km) and that have diverse life-history characteristics. The primary objective is to advance our general knowledge of connectivity in the deep sea. The focus is on species and processes occurring in the IAS, with attention to oceanographic circulation, life histories, and genetics. Questions that apply in shallow-water systems motivate this study:

1. What phylogeographic breaks occur in the system? It is important to distinguish between phylogeographic history and connectivity. A phylogeographic break with no shared alleles between populations implies a long history of isolation or possibly cryptic speciation.

2. Are populations connected by ongoing migration? This is the fundamental question about connectivity and the scale of genetic variation in marine species with planktonic larvae.

3. What biophysical processes underlie observed connectivities? Biological processes (e.g., larval distributions in the water column, timing of reproduction, and planktonic larval duration) and physical processes of transport and dispersion interact to determine connectivity.

The oceanographic model for the IAS will be improved and coupled to a Lagrangian larval transport model. The field program includes time-series sampling of larvae at seeps with records of current velocities, water column sampling to determine larval distribution potential, shipboard studies of larval biology and behavior, and sampling of benthic target species. Phylogenetic and population genetic tools will be used to explore historical and contemporary gene flow. Iterative interactions among the science teams will advance our understanding of connectivity in the deep sea and to develop effective and best methods for hypothesis testing under the constraints of working in a relatively inaccessible environment. Since their discovery, deep-sea chemosynthetic ecosystems have been novel systems within which to test the generality of paradigms developed for shallow-water species. This study will explore scale-dependent biodiversity and recruitment dynamics in deep-sea seep communities, and will identify key factors underlying population persistence and maintenance of biodiversity in these patchy systems.

Broader Impacts. Building capacity (knowledge and expertise) in studying spatial and temporal scales of connectivity and the oceanographic and life-history processes that underlie genetic subdivision in the deep sea is critical in light of emergent policy regimes in both Exclusive Economic Zones and on the High Seas related to marine spatial planning. A seascape genetic approach will be adopted to advance beyond the state-of-the-art through inclusion of biophysical modeling, observations of larval biology and ecology, and a comprehensive suite of molecular tools. Results will be broadly disseminated to advance scientific understanding through peer-reviewed publications and will enhance the capacity to undertake coupled oceanographic-life history-genetic studies through (i) training of 6 graduate students and 1 post-doc, (ii) through incorporation of approaches and results in presentations at professional meetings and workshops, and (iii) through presentations and discussions seminars and classes for graduate and undergraduate students. Results of this work will be used to inform policymakers engaged in the design of deep-sea networks of marine reserves. In addition, two innovative activities will be undertaken: a field-oriented interdisciplinary deep-sea research course for advanced PhD students and post-docs, and an artist-in-residence at sea that enhance the broad impact of the research.