Conlan and Kvitek 2005

Conlan KE, Kvitek RG. 2005. Recolonization of soft-sediment ice scours on an exposed Arctic coast. Marine Ecology Progress Series 286: 21-42.

These authors monitored the occurrence, aging, and biotic recolonization of ice scours in the Barrow Strait near Resolute, Nunavut. Ice structures with deep keels, such as icebergs locked in pack ice, can scour the soft bottom even at depths approaching 100m. Scours can be 10 to 15 meters deep, hundreds of meters wide, and kilometers long, though many are smaller than that. A scour forms a characteristic geomorphology, with a deep trough that may include multiple parallel sub-troughs, bordered by berms that may be 4-5m tall relative to unscoured adjacent seabed. The benthos of Barrow Strait is hard-packed clay armored with cobble, a glacial till that lies about 5m thick above the bedrock.

Ice scours remove the cobble, and the berms are much softer than either the troughs or adjacent unscoured seabed. These authors, and a large crew of assistants, sampled the macroinvertebrates of the seabed by cores collected by SCUBA. The faunal analysis was by seiving the samples, fixing specimens in 4% Formalin and preserving them in 70% Ethanol. Most specimens were identified to family or genus, but a large sample of collected polychaetes were sent to experts in Ottawa for species-level identification. Faunal composition was compared across scours, troughs and berms, unscoured seabed, and scours of various ages, monitored over a 9-year period.

Biotically, the examined portion of the Barrow Strait constitues “urchin barrens”. Sea urchins, primarily Strongelocentrotus droebachiensis and S. pallidus, are present in high density and graze on most other epibenthic and shallow-infaunal invertebrates as well as consuming most of the available algae. The invasion by urchins may be recent, as suggested by the presence of Balanus crenatus only in areas where urchins are absent, but crushed shells of this barnacle in many areas. Other macroinvertebrates found included brittle stars, gastropods, soft corals, anenomes, sea cucumbers, etc, as well as several species of bottom dwelling fishes.

In general, the authors found a pattern of biodiversity consistent with the intermediate-disturbance hypothesis. Total species richness and biomass were both higher in areas of scours compared to unscoured areas. A patch of seabed protected from most scours behind a large berm had lower total diversity. No suite of climax species was found in any undisturbed area. One species of polychaete was found only in relatively young scours, but all other species occurred in all habitats, though relative abundances varied. This pattern suggests that ice scours and their associated habitat variation may be maintaining relatively high biodiversity in this region.

Ice scours occur with a frequency of about 1.1 events per kilometer per year, similar to some other ice-scoured habitats in other polar regions. This rate may either increase or decrease with climate warming. Warmer temperatures may increase the rate of iceberg calving, increasing the supply of deep-keel ice structures. Alternately, warmer temperatures may reduce the thickness, strength, or movements of winter pack ice and associated scouring structures.