From Plant Press Vol. 16 no. 4, October 2013
To better understand the longevity ecology of the coralline algae, Clathromorphum compactum, a prime Arctic/Subarctic climate archive species, Walter H. Adey spent 10 weeks during the 2013 summer on a cruise of the R/V Alca i in northern Labrador, Canada. The cruise was funded largely through a Canadian Natural Sciences and Engineering Research Council (NSERC) grant to himself and his two colleagues, Jochen Halfar at the University of Toronto and Patrick Gagnon at Memorial University of Newfoundland. Halfar and Gagnon did not participate in the cruise at sea, but each provided a graduate student/diver, both of which were also carrying out their personal doctoral research as part of the cruise.
The vessel crew totaled seven: Adey serving as vessel captain and chief scientist on the cruise, a chief engineer, an administrative officer, a cook and three Ph.D. student/SCUBA divers—Thew Suskiewicz of Laval University, David Belanger of Memorial University, and Michael Fox of Scripps Institute of Oceanography. Suskiewicz carried out experimental analyses of sea urchin feeding rates on kelp and Belanger analyzed infauna within the coralline rhodoliths Lithothamnion glaciale and Lithothamnion tophiforme.
Approximately 80 SCUBA dives to depths of up to 30 meters were carried out, two thirds with two divers and one third with three divers. During most of the work season, bottom working temperatures ranged from -1.5ᵒ C to +2ᵒ C, limiting dives to about 50 minutes.
The cruise was specifically dedicated to the establishment of ecological parameters allowing the collection of specimens of Clathromorphum compactum exceeding 1,000 years in age. While pursuing this objective, it was possible to identify an entirely new sub-community of the rocky Subarctic benthos. This common cobble-boulder, glacial lag-till community allows the achievement of great age in C. compactum. At the prime work site in Kingitok Islands, where they spent about one third of their total field time, the mean thickness of the collected 51 samples was 105 mm, and the maximum was over 200 mm. Since Adey estimates the growth rate to be between 110-120 µm per year, based on the research cruises of 2010-2011, they now have 17 samples thicker than 115 mm (approximately 1,000 years old); the oldest at over 200 mm is nearly 1,700 years old. These specimens more than double their Arctic/Subarctic climate archive potential and are invaluable additions to the herbarium’s coralline climate archive collection, and add to the determination of past sea ice cover, ambient temperature and salinity, as well as carbon and oxygen isotope levels.
The identification of a new benthic community, based in fine sedimentation into a lag till of cobbles and boulders with Lithothamnion rhodoliths that enhances great age in this climate archive species, presages a new era of collection and the beginning of significant herbarium expansion. It also allows Adey to once again bring his Pleistocene geology background together with his coralline research. While both the sea urchin and rhodolith components of the cruise are independent doctoral thesis efforts, both directly relate to his C. compactum research.
A secondary objective of Adey’s personal research on this cruise was the obtaining of abundant samples of Leptophytum species for phylogenetic work. From pebble/shell bottoms mostly over 25 m, approximately 100 samples of Leptophytum laeve and Leptophytum foecundum were taken. These are critically needed for the phylogenetic studies of the Melobesiaceae currently in progress. Extracting DNA from samples currently in the herbarium has been difficult. This large number of dives, some dedicated to this need for the coralline herbarium, produced many mollusk shell encrustations solely occupied by each of the Leptophytum species. It is expected that this will solve a serious analysis problem with this genus.