Deepwater Emergence of Red Tree Coral, Primnoa pacifica, in Glacier Bay, Alaska

Stone, R.; Mondragon, J.; Andrews, A.

Brief Description: In 2003, red tree corals (Primnoa) were observed in shallow water (< 25 m depth) during videographic habitat surveys in Glacier Bay National Park in southeastern Alaska. This fortuitous discovery provided a valuable opportunity to advance our knowledge about the bathymetric and geographical distribution, ecology, and habitat requirements of Primnoa. Full Description: Red tree corals (Primnoa) are large, structure- forming gorgonians with a broad distribution in Alaska. They are dominant biotic components of benthic habitats in some areas of the Gulf of Alaska (GOA) where they form dense thickets. There is much evidence that red tree corals provide important structural habitat for many species, particularly rockfish (Sebastes spp.) includinggravid females and juveniles. Unfortunately, red tree corals are highly susceptible to disturbance from fishing activities, and the recovery rate of disturbed habitats (based on reported growth rates) is likely on the order of many decades. In recognition of their importance, the North Pacific Fisheries Management Council recently approved closure of five small Primnoa-rich areas in the eastern GOA to all bottom contact fishing gear.In 2003, red tree corals were observed in shallow water (< 25 m depth) during videographic habitat surveys in Glacier Bay National Park in southeastern Alaska. This fortuitous discovery provided a valuable opportunity to advance our knowledge about the bathymetric and geographical distribution, ecology, and habitat requirements of Primnoa.Glacier Bay is a large, y-shaped fjord with multiple tidewater glaciers that was formed by rapid glacial retreat during the past 220 years. An accurate record of deglaciation in the upper reaches of the Bay provided a timeline gradient (chronosequence) with which to examine community succession and validate the growth rate previously estimated for Primnoa.