Project: Recovery of Seamount Precious Coral Beds From Heavy Trawling Disturbance

Resilience, and the related concept of recovery, provides insights into ecosystem function, connectivity, and succession. In the marine realm, most resilience studies have focused on shallow-water ecosystems but increasing anthropogenic impacts in the deep-sea are making studies of resilience and recovery in the deep-sea time-critical, with deep-sea hard-substrate habitats and large-scale disturbances having received the least attention. Ironically one of the key anthropogenic impacts to the seafloor, fish trawling, provides an experimental design to understand processes of recovery from large-scale disturbance. Seamounts, with a high proportion of hard-substrate habitat, discreet locations for sampling, and extensive disturbance from fish trawling, provide an excellent natural laboratory to study the recovery aspect of resilience. Additionally, the abundance, numerical dominance, high biomass, and diversity of deep-sea corals on seamounts make them ideal model organisms for these studies.

The goal of this project is to examine a series of locations in the far Northwestern Hawaiian Islands (NWHI) and the Emperor Seamount Chain (ESC) to address the hypothesis, based on predictions of low resilience and decadal recovery times for disturbed seamounts, that deep-sea coral beds in the NWHI have not recovered despite the end of trawling 30+ years ago. To test this hypothesis, the PIs will survey a series of replicate seamounts at three levels of fish trawling intensity using autonomous and remote underwater vehicles to conduct surveys and targeted sampling of the seamount fauna and especially deep-sea corals. The PIs will focus on three specific aspects of the seamount communities: community structure, age structure of precious corals using a verified size-age curve, and genetic structure of precious corals using DNA microsatellites. Using these methods the PIs will be able to predict the time since coral colonization on any particular seamount as well as source populations of the recent colonizers.

These seamounts represent a natural experiment with the added factor of time since the establishment of the exclusive economic zone, and provide an unparalleled opportunity to address seamount recovery on decadal time scales. The powerful combination of aging tools and microsatellites will allow the PIs not only to constrain time scales of deep sea coral colonization, but also rates of recruitment and source of the colonizers. The results will provide significant insights into key ecological processes on seamounts, thus serving to inform further science as well as management.