Month: July 2015

2015 Deep Sea Coral Exploration in the Gulf of Maine

NURTEC conducted 26 tows using its ISIS2 towed camera system from July 1-10, 2015, continuing its partnership with NOAA Fisheries Northeast Fisheries Science Center and University of Maine to explore the Gulf of Maine for Deep Sea Corals (DSC’s). The ISIS2 camera sled was equipped with both down and forward-looking hi-def video cameras and a down-looking digital still camera. For 2015 NURTEC integrated two thrusters onto the sled to provide much improved and much needed maneuverability that allowed the system to be better positioned in the rugged topography and deal with the strong currents of the Gulf of Maine. The system was operated off the RV Connecticut, which again provided the perfect support ship for this type of operation with its dynamic positioning capabilities.

 

This was the third expedition, funded by NOAA’s Deep Sea Coral Research and Technology Program, to explore for DSC’s in the Gulf, with each year finding new areas that support these ecologically sensitive and vulnerable, slow-growing animals that were likely much more ubiquitous in the region. In addition, some sites from previous years were revisited to assess the condition of the corals from previous surveys. Three main areas were surveyed this year: Outer Schoodic Ridge, the Mount Desert Rock area and the Georges Basin region. The following provides some highlights from this expedition.

Several areas on Outer Schoodic Ridge did appear, based on coarse resolution bathymetry, to be similar to areas previously found to support dense coral communities. Nonetheless, they turned out to be steep sediment slopes with evidence of impacts from both mobile and fixed fishing gear (e.g., tracks on sonar, displaced cobbles and boulders). One site that was revisited from a previous cruise, with dense coral and sponges on both horizontal surfaces and steep vertical walls, had a tremendous abundance of haddock. Noteworthy is that pollock was the primary gadiform species in 2014 and silver hake in 2013. All appeared to search for and capture prey amongst the structure-forming fauna, including corals. While some of this activity is due to the attraction of prey and predators to the underwater vehicle, the variation in dominant fish species observed from year to year reflects variability in the presence of particular taxa. This suggests that DSC habitat can serve as the ecological stage for multiple players depending on current conditions.

Two spectacular coral walls were discovered in the Mount Desert Rock area on this cruise, with hanging gardens of red tree coral (Primnoa), fan coral (Paramuricea) and multiple species of sponge. A very rare pom pom anenome was observed enroute to one of the vertical walls. Noteworthy here were the dense patches of sea pens (Pennatula), including many smaller size classes (i.e., assumed younger age classes), encountered in fine-grained sediment habitats interspersed between rock ledges. This was perhaps the highest density of sea pens observed throughout this project.

Finally, no corals were observed at the base of the slope stretching from Georges Bank into Georges Basin. However, Lindenkohl Knoll, that forms a northern boundary to Georges Basin, did have sparse corals in multiple locations (mostly Paramuricea) along with evidence of extensive impacts from fishing. Steep vertical rock outcrops, like those in the northern Gulf that supported dense coral gardens, were nearly denuded of fauna and exhibited marks from fishing gear (extensive markings from ground-line components). Noteworthy is that such marks stretched from the base of one outcrop to over 6 m in vertical relief. In general, Paramuricea and associated epifauna were often small and virtually all occurred in physical refugia such as cracks and crevices of outcrops and along the sediment-rock interface of large cobbles and boulders. The one exception was an approximately 2 m deep by 4-5 m wide feature in a large outcrop with dense Paramuricea.

The results of this cruise, together with data collected during previous cruises, will provide the New England Fisheries Management Council and NOAA Fisheries important information for crafting a new Coral Amendment focused on conservation of these sensitive and vulnerable species.