Research 31 (2011) S69–S84

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Continental Shelf Research

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Geological features supporting deep-sea coral habitat in Atlantic

Evan N. Edinger a,n, Owen A. Sherwood b,1, David J.W. Piper c, Vonda E. Wareham d, Krista D. Baker f, Kent D. Gilkinson d, David B. Scott e a Departments of Geography, Biology and Earth Sciences, Memorial University of , St. John’s, NL, Canada A1B 3X9 b Departments of Biology and Earth Sciences, Memorial University of Newfoundland, St. John’s, NL, Canada A1B 3X5 c Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, NS, Canada B2Y 4A2 d Northwest Atlantic Fisheries Centre, 80 East White Hills, St John’s, NL, Canada A1C 5X1 e Department of Earth Sciences, Dalhousie University, Halifax, NS, Canada B3H 4J1 f Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada A1B 3X9 article info abstract

Article history: Geological features supporting cold-water coral habitat in are reviewed and Received 16 June 2009 exemplified using qualitative field observations from the Scotian margin and Southwest Grand Banks, Received in revised form Newfoundland, in the context of regional geology of the Atlantic Canadian . Coral 15 February 2010 habitats are concentrated in areas of shelf-crossing troughs and trough-mouth fans associated with Accepted 8 July 2010 glacial ice streams. Most habitat types are supported by glacial or glaciomarine depositional features, Available online 11 July 2010 although some are supported by erosional features, probably related to subglacial meltwater erosion. Keywords: Shelf-break and upper continental slope moraine deposits, subject to strong currents, form current- Deep-sea corals swept cobble-boulder pavements, forming the principal habitats for the large gorgonian corals Primnoa Ice streams resedaeformis and Paragorgia arborea. At greater depths, upper slope till tongues are upper continental Till tongues slope gravelly mud deposits, exposed at the surface as isolated cobbles and boulders in a muddy sand Subglacial meltwater erosion Newfoundland and matrix. Common skeletal corals in these environments include the large long-lived gorgonian Keratoisis Scotian shelf ornata, the smaller gorgonian Acanthogorgia armata, and, in muddy sand between rocks, the small gorgonian Acanella arbuscula. Erosional environments including friable Tertiary mudstones and semi- consolidated Quaternary sediments, colonized by large gorgonians and other corals, were observed in The Gully, the Stone Fence, and the Southwest Grand Banks. Weak bedrock strength may limit the size of large gorgonian coral colonies. Authigenic carbonate crusts, possibly related to cold seeps, may be locally important in supporting coral growth. Predictive models of coral distribution should consider Quaternary and surficial geology. & 2010 Elsevier Ltd. All rights reserved.

1. Introduction 2007). Deep-sea scleractinian and gorgonian corals have also attracted attention as paleoceanographic monitors, as annually Deep-sea corals have gained considerable scientific and resolved paleoclimate data can be encoded in the skeletal conservation attention in the past decades as long-lived and chemistry of their centuries-old skeletons (reviewed by Sherwood vulnerable habitat-structuring organisms (Hall-Spencer et al., and Risk, 2007). The great life-spans of deep-sea corals (Sherwood 2002; Roberts et al., 2006). The worldwide decline of fisheries et al., 2006; Sherwood and Edinger, 2009) and their susceptibility has prompted an examination of the role deep-sea corals serve as to damage from fisheries and other activities have made them habitat for fish (Husebø et al., 2002; Auster, 2005; Costello et al., objects of great conservation concern in Atlantic Canada (Gass, 2005; Stone, 2006; Edinger et al., 2007a) and invertebrate 2003; Mortensen et al., 2006a; Edinger et al., 2007b) and biodiversity (Krieger and Wing, 2002; Buhl-Mortensen and elsewhere (Fossa˚ et al., 2002; Hall-Spencer et al., 2002; Ardron Mortensen, 2005; Metaxas and Davis, 2005; Henry and Roberts, et al., 2007; and many others). Because many types of corals require hard substrates, surficial geology has considerable influence on their distributions. The n Corresponding author. Tel.: +1 709 737 3233; fax: +1 709 737 3119. geological origins of the features that create coral habitat have E-mail addresses: [email protected] (E.N. Edinger), [email protected] been an object of study in the European margin (Freiwald et al., (O.A. Sherwood), [email protected] (D.J.W. Piper), [email protected] 2002; Hovland and Risk, 2003; Noe´ et al., 2006) and the Gulf of (V.E. Wareham), [email protected] (K.D. Gilkinson), [email protected] (D.B. Scott). Mexico (Schroeder et al., 2005; Schroeder, 2007), but not 1 Current address: 904 Memorial Dr. NW, Calgary, AB, Canada T2N 3C9. previously in Atlantic Canada. Some Norwegian deep-sea reefs

0278-4343/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.csr.2010.07.004 S70 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 have grown on the berms left by Pleistocene iceberg scours Paramuricea spp. (a mix of Paramuricea placomus and Paramuricea (Freiwald et al., 1999), similar to the berms that support some grandis), the small gorgonians Acanthogorgia armata, Acanella hexactinellid sponge reefs in British Columbia (Conway et al., arbuscula, and Radicipes gracilis, the antipatharian coral Stauro- 2005). The nature of the features that support coral growth varies pathes arctica, and the solitary cup corals Desmophyllum dianthus considerably among regions, particularly between paraglacial and Flabellum spp. Most of these species are thought to tolerate continental margins, continental margins not subject to glacial low-current settings more effectively than Primnoa and Paragorgia effects, and or other non-continental margin settings. (Bryan and Metaxas, 2007; Cogswell et al., 2009). This paper has three objectives. First, we review the distribu- Unfortunately, many areas of known coral habitat have been tion of skeletal deep-water coral species and in relation to geology extensively fished by trawl, gillnet, and bottom longline (Kulka of the continental margin in Atlantic Canada. Second, we and Pitcher, 2002; Mortensen et al., 2005; Edinger et al., 2007b) qualitatively describe the nature and origins of several kinds of and much of the original coral habitat may have been damaged or geological features that provide habitat for deep-sea corals in destroyed. Efforts at coral conservation depend on accurate Atlantic Canada as observed during recent ROV cruises in Atlantic distribution data, an understanding of the factors controlling Canada. Finally, we briefly compare the geological features distribution, and the anthropogenic threats to corals (Breeze and supporting coral growth in Atlantic Canada with the features that Fenton, 2007). Statistical approaches to defining the factors support cold-water coral growth on paraglacial and non-para- controlling coral distribution in Atlantic Canada have identified glacial settings in other regions of the world. substrate and bottom water temperature as key variables (Mortensen et al., 2006b). Ecological niche factor analysis modeling identified slope, temperature, surface chlorophyll A 1.1. Corals in Atlantic Canada concentration, and bottom current strength as the dominant predictors of large gorgonian coral distribution (specifically Deep-sea corals in Atlantic Canada include more than 30 Primnoa and Paragorgia, Bryan and Metaxas, 2006, 2007), species of gorgonian octocorals with calcitic and/or organic while recognizing that slope may be a proxy for distribution of skeletons (‘‘gorgonians’’), non-skeletal alcyonacean octocorals hard substrates, rather than a biologically meaningful variable (‘‘soft corals’’), pennatualcean octocorals (‘‘sea pens’’), antipathar- (Metaxas and Bryan, 2007). Similar analysis with geographically ians with organic skeletons (‘‘black corals’’), and solitary and weighted regression found slope to be significant to gorgonian colonial scleractinians (‘‘stony corals’’) (MacIsaac et al., 2001; coral distributions in the Newfoundland and Labrador region at Gass and Willison, 2005; Wareham and Edinger, 2007). Large the regional scale, because corals are concentrated along the gorgonian, antipatharian, and most scleractinian corals are continental slope, but not important at the local scale (Jones, generally dependent on hard substrates, while sea pens, some 2008). Because finely resolved continuous spatial data on surficial small gorgonians, and some soft corals can occupy sand and mud geology are not available for most parts of Atlantic Canada, most bottoms, along with reclining solitary scleractinians such as attempts to analyze factors controlling coral distribution either Flabellum. have not considered substrate at all (Bryan and Metaxas, 2007), or Using fishermen’s knowledge, museum collections, and coral consider substrate only by grain size, without consideration of the bycatch data from scientific surveys and commercial fisheries, geological origins of hard substrate features (Mortensen et al., the distribution of 430 species of octocoral, antipatharian, and 2006b). scleractinian corals has been mapped off Nova Scotia and This article reviews the geology of the Atlantic Canadian Newfoundland (Breeze et al., 1997; MacIsaac et al., 2001; Gass continental margin, and compares the geology with the broad and Willison, 2005; Mortensen et al., 2006b; Wareham and distribution of cold-water corals in Atlantic Canada. This paper Edinger, 2007; Fig. 1). Habitat characteristics of coral-rich areas also presents qualitative in-situ observations of the geological shallower than 1000 m have been described from the shallow features that support coral habitat, and using bottom photographs (Mortensen and Buhl-Mortensen, 2004, 2005a) and deeper from the 2007 cruise to the eastern Scotian Shelf and Southwest (Watanabe et al., 2009) areas of the Northeast Channel, and The Grand Banks. Observations presented here include the nature of Gully (Mortensen and Buhl-Mortensen, 2005b; Cogswell et al., the habitat-supporting features, and the coral species observed on 2009), but not from other locations. each type of feature. This paper does not present quantitative Most large gorgonian corals are concentrated along the shelf results of video analyses of coral abundance, depth distribution, break from 200 to 800 m depth, but the depth ranges of many of and species composition (e.g. Baker et al., 2008; Cogswell et al., the smaller gorgonians and sea pens extend well below 1000 m, 2009), which will be published separately. and some species live deeper than 2000 m (Wareham and Edinger, 2007; Baker et al., 2008). Areas with greatest density of deep-sea coral records coincide with submarine canyons such as The Gully, 2. Geological setting and the mouths of shelf-crossing troughs of the Scotian Shelf, Grand Banks, Northeast Newfoundland Shelf, and Labrador Shelf. The entire continental margin of Atlantic Canada has been Major deep-sea coral sites in Labrador waters include the Hudson affected by Pleistocene glaciations, which eroded the continental Strait and northern edge of Saglek Bank, and sites close to the shelf and strongly influenced depositional features both on the mouth of Okak Saddle, Hopedale Saddle, Cartwright Saddle, and shelf and in deep water beyond the ice limit (Boyd et al., 1988; Hawke Channel (Fig. 1). Coral assemblages in the Northeast Scott et al., 1989; Shaw et al., 2002; Piper, 2005; Shaw et al., Channel, The Gully, and the Stone Fence, which have been 2006). Glacial ice reached the shelf edge at the last glacial identified as the key areas for deep-sea corals in Nova Scotia, are maximum (LGM) along much of the eastern Canadian margin (e.g. dominated by two large gorgonian corals, Primnoa resedaeformis Stea et al., 1998; Piper and Brunt, 2006) but may not have crossed and Paragorgia arborea, but these species are rare in most parts of wide shelves such as the Grand Banks since the previous glacial Newfoundland and Labrador, with the exception of the Hudson maximum in marine isotope stage 6 (Huppertz and Piper, 2009). Strait coral hotspot near the northern tip of Labrador (Mortensen Major erosional physiographic features left by glaciation include et al., 2006b; Wareham and Edinger, 2007; Wareham, 2009). The shelf-crossing troughs associated with ice streams across the most common skeletal corals in other parts of Newfoundland and Scotian Shelf, Grand Banks, Northeast Newfoundland Shelf, and Labrador waters are the large gorgonians Keratoisis ornata and Labrador Shelf (Piper, 2005; Shaw et al., 2006). The largest of E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S71

70 BB N corals per cell 26-125 6-25 1-5 DS 65

HS 60 SB

OS

HP

Labrador CS 55 HK

OK 50 TP

Newfound- land FP FC GB

45 Scotia LC HC Nova SS SF DC SG

GB NC

o 40 N o 70 W656055504540

Fig. 1. Map of the continental margin of Atlantic Canada. from ETOPO2. Colored hexagons indicate abundance of skeleton-forming deep-sea corals (Acanella arbuscula, Acanthogorgia armata, Desmophyllum dianthus, Flabellum alabastrum, Keratoisis ornata, Paragorgia arborea, Paramuricea spp., Primnoa resedaeformis, Radicipes gracilis, Stauropathes arctica, Vaughnella margaritata) per each 0.51 cell collected off the continental margin of Atlantic Canada by research survey trawl and fisheries observers, 2003–2008. Newfoundland and Labrador data from Wareham and Edinger (2007), Gilkinson and Edinger (2009); Nova Scotia data from Gass and Willison (2005). Coral density values are consistent within the Newfoundland and Labrador region, and within the Nova Scotia region, but density values are not directly comparable between regions due to differing density of sampling effort, particularly after fisheries closures to protect corals after 2002. X on Orphan Knoll indicates non-quantified occurrence of corals, mostly Desmophyllum dianthus, both subfossil and recent (see Smith et al., 1997). Bold arrows mark positions of ice streams during last deglaciation (after Piper, 2005; Shaw et al., 2006). Features referred to in text include (BB) Baffin Bay, (DS) Davis Strait, (HS) Hudson Strait, (SB) Saglek Bank, (OS) Ogak Saddle, (HP) Hopedale Saddle, (CS) Cartwright Saddle, (HK) Hawke Channel, (TP) Tobin’s Point, (OK) Orphan Knoll, (FC) Flemish Cap, (FP) Flemish Pass, (GB) Grand Banks, (DC) Desbarres Canyon, (HC) Haddock and Halibut Channels, (LC) Laurentian Channel, (SF) Stone Fence, (SG) Sable Gully, (SS) Scotian Shelf, (NC) Northeast Channel, (GB) Georges Bank. S72 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 these include the Northeast Channel, the Laurentian Channel, and Newfoundland and Labrador, eastward and northward from the Hudson Strait, which contained the principal ice streams in Halibut Channel, there has been Quaternary progradation of Atlantic Canada. In contrast, ice domes formed on some of the glacial till, and bedrock outcrops are rare or absent. Strong tidal outer banks (Gipp, 1994; Fig. 1). currents in Northeast Channel and The Gully have kept eroded Almost the entire upper continental slope off Atlantic Canada bedrock, and at the shelf-edge also till, free of surficial cover. is underlain by glacial till. It is lacking only off parts of the Elsewhere, late Pleistocene and Holocene sediment has mantled southern Grand Banks and at Flemish Cap. In places, the till is the floors and walls of most channels, yielding mud and fine sand buried up to tens of metres beneath younger proglacial and surficial cover atop the underlying dendritic drainage (Piper and Holocene sediment. It is recognized in seismic-reflection profiles Campbell, 2002; Mosher and Piper, 2007b). as wedge-shaped acoustically incoherent sediment packages, commonly termed till tongues, that pinch out generally between 500 and 700 mbsl (King and Fader, 1986; Piper et al., 2005; Piper, 3. Methods 2005). Where sampled, till tongues are either not penetrated by a 1 tonne piston corer, or return overconsolidated diamict with In 2001, 2006 and 2007 researchers from Dalhousie University, shear strengths of 60–100 kPa characteristic of lodgement till. Memorial University of Newfoundland and Fisheries and Oceans Only at the seaward pinch out of the till tongues does the diamict Canada surveyed deep-sea coral habitat in Atlantic Canada with appear normally consolidated (Piper and Macdonald, 2002). These the remotely operated submersible ROPOS. Surveys were con- upper slope till tongues thus differ from similarly named features ducted along the upper continental slope between southwest in continental shelf basins that are principally debris-flow Nova Scotia and the southwest Grand Banks of Newfoundland deposits (Stravers and Powell, 1997). Locally, debris flow deposits (Fig. 1). apparently derived at least in part from glacial till are found immediately downslope from till tongues, for example off St. 3.1. Qualitative photographic and video observations. Pierre Slope (Bonifay and Piper, 1988) and off Whale Bank (Piper and Gould, 2004). Seaward of some transverse troughs, notably off Surveys were performed with the remotely operated vehicle Hudson Strait (Rashid and Piper, 2007) and off Trinity Trough (ROV) Remote Operated Platform for Ocean Science (ROPOS), (Tripsanas and Piper, 2008), upper slope till tongues pass directly deployed from CCGS Martha Black (2001) and CCGS Hudson (2006, into continuous glacigenic debris-flow deposits. Many sampled 2007). The 2001 cruise was limited to a depth of 500 m, while tills on the continental shelf and upper slope are sandy or muddy, during the 2006 and 2007 cruises, the vehicle was configured to a substantially derived from reworking of Pleistocene or Late maximum depth of 2500 m. In Nova Scotia waters, surveys Tertiary sediments on the shelf, but include a small proportion targeted known areas of coral abundance in the Northeast Channel, of bedrock pebbles to boulders. Such large clasts are also The Gully and Stone Fence, based on previous reports (Breeze et al., transported to the continental slope by icebergs. In many cases, 1997; MacIsaac et al., 2001; Gass and Willison, 2005), and upper slope till has been scoured and pitted by icebergs, and the following upon previous in-situ investigations using drop-video surface commonly has been reworked by shelf-edge currents and (Mortensen and Buhl-Mortensen, 2004, 2005a, b; Mortensen et al., storms (Mosher et al., 2004). 2006b). In Newfoundland, knowledge of coral distribution was Within transverse troughs, acoustically incoherent stacked tills more limited (Wareham and Edinger, 2007), so depth-stratified commonly have been deposited at the seaward end of the trough 1 km transects for fish abundance and diversity (along contour) near the shelf break, creating a low ridge that is shallower than and up-slope transects (for invertebrate identification and collec- the trough on the central part of the shelf (King, 1996; Stea et al., tions) were carried out along pre-determined routes, based on 1998; Piper and MacDonald, 2002; Rashid and Piper, 2007). In the reports of coral bycatch (Wareham and Edinger, 2007; Edinger case of the Laurentian Channel, late glacial and Holocene et al., 2007b). Depth-parallel transects in the Newfoundland were sediment has covered the stacked till in the center of the channel generally conducted at 1000, 800, 700, 600, 500, and 400 m depths, (Josenhans and Lehman, 1999), but strong currents at the SW with intervening up-slope transects for megafauna identification margin of the channel maintain cobble-boulder environments at and collections. Additionally, at least 1 dive to 2000 m or greater an area called the Stone Fence, where thick tills have been was conducted in the Northeast Channel, The Gully, the Stone plastered over the bedrock edge of Laurentian Channel. Similarly, Fence, Haddock Channel, and Desbarres Canyon. strong tidal currents in the Northeast Channel sweep the end Video was recorded continuously during each dive, and digital moraine (Ramp et al., 1985), and outflow of Arctic water still photographs were taken opportunistically. Parallel lasers generates strong currents seaward of Hatton Basin off Hudson placed 10 cm apart were used to indicate scale, and to estimate Strait (Straneo and Saucier, 2008). sizes of substrates coarser than sand, and of corals, other Seaward of the till tongues, the heads of submarine canyons macrofauna, and fishes. Manipulator arms and collection boxes show dendritic drainage patterns, which are particularly evident fitted on the vehicle were used to collect samples for species in multibeam sonar-derived bathymetry (Fader and King, 2003; identification and for biological and paleoceanographic studies. Mosher et al., 2004; Piper, 2005). Some canyons appear to connect Video analysis of substrates at sea, and post-processed in the with buried tunnel valleys on the adjacent shelf (Piper et al., 2007, lab, used the Bedford Institute of Oceanography’s in-house video their Fig. 13) and have flat broad floors, interpreted to result from analysis program ‘‘Class-Act Mapper’’, in which substrates, corals, erosion by subglacial meltwater. Similar broad valleys extending sponges, other invertebrates, fishes, and anthropogenic features from near the shelf break are found seaward of some transverse such as lost fishing gear were recorded, along with position, troughs, including Laurentian Channel and Halibut Channel depth, and any other qualitative observations. The field of view (Mosher and Piper, 2007a). In places, these broad valleys diverge was quantified from the lasers, allowing estimates of the total into spillover channels and have eroded residual buttes (Hughes- area surveyed, and the relative abundance of different substrates. Clarke et al., 1990). The deep incision of canyons at the mouth of Substrates were identified and described visually, with some Northeast Channel and The Gully has also been ascribed to the collection of rocks where attached to corals. Visual identification effect of subglacial meltwater (Piper et al., in press). In these of substrates used the scaling lasers, relative to the Udden– settings and in the fan valleys off Laurentian Channel, eroded Wentworth grain size scale for substrates coarser than sand. bedrock is widespread. Seaward of the shelf-crossing troughs of Substrates were classified as bedrock, boulders, cobbles, gravel, E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S73 sand, and fine-grained sediment (muddy sand and mud); relative structures. Positions of seismic lines and bottom photographs abundance of substrate types was estimated visually to the presented here are indicated in the location map and insets in nearest 10% throughout each dive, with up to three substrates Fig. 2. Multibeam bathymetry in inset maps of Fig. 2 is derived recorded at any one time. Rock types were assessed visually, and from previously published datasets (Mosher and Piper, 2007b; with rare collections. Dip angle of exposed bedrock or semi- Cameron and King, 2008; also available at http://gdr.ess.nrcan.gc. consolidated sediments was assessed visually in relation to the ca/multibath/e/viewer.htm). position of the ROV, and checked against the attitude sensors (roll, pitch, heave) of the ROV. Coral species were identified visually using colour photo- 4. Qualitative field observations graphic identification guides, with collection of some species for verification by spicule analysis or reference to taxonomic experts Four principal types of geological features were observed to (Baker et al., 2008; Cogswell et al., 2009; Wareham, 2009). Coral support coral growth on hard substrates along the Scotian Margin species lists and depth distributions were compiled for each and Southwest Grand Banks of Newfoundland. These were (1) location studied (Baker et al., 2008; Wareham, 2009; Cogswell current-winnowed moraine-derived till deposits on the outer et al., 2009). Relative and absolute abundance of coral taxa, while continental shelf and uppermost slope; (2) till tongues on the not presented in this paper, were quantified as N colonies/m2, upper slope; (3) eroded friable Tertiary bedrock and Quaternary using the estimated area of each video transect. consolidated glaciomarine sediments; and (4) authigenic carbo- Precise tracking of ROV position allowed matching of in-situ nate crusts. Unconsolidated post-glacial sediments supported geological observations with archival sub-bottom profiles and corals not dependent on hard substrates. The geological features multibeam bathymetric data of three- dimensional geological supporting coral habitat are described in order below.

65°W 60°W 55°W Newfoundland

Laurentian Channel

46°N

nnel Cha but i al H

Nova Scotia

44°N Stone Haddock Channel Fence The Gully Desbarres Canyon

Northeast Chan nel mbsl 42°N 1000 1500 2000 2500

150 10 km 57°10’W 57°0’W 55°30’W 55°10’W 42°0’N 10 km 40 200

0m 10 km 300 44°30’N 7 45°0’N 5 4 13 100 m 300 m 1214 15 m0 3 8 150 m 11 m 44°0’N

1000 9 10 41°50’N

m 6 50 m 44°20’N 44°40’N

100 65°50’W 65°40’W 59°10’W 59°0’W 20 km

Fig. 2. (A) Location map showing areas of in-situ qualitative observations, and positions of figures. Inset maps show positions of sub-bottom profiles or bottom photographs in relation to detailed bathymetry. (B) Northeast Channel, Fundian Channel. (C) The Gully. (D) Stone Fence. (E) Haddock and Halibut Channels. Multibeam bathymetry courtesy of Geological Survey of Canada and Canadian Hydrographic Service. S74 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84

4.1. Shelf-break and upper slope winnowed till Southwest Grand Banks (Figs. 2Eand8). Till tongues are recognized in sub-bottom profiles as downslope continuations of acoustically Winnowed till, or ice-contact sediments, derived from end incoherent reflecting bodies that have since been buried by post- moraines, provides the primary habitat for large gorgonian corals glacial sediment. In acoustic profiles, these acoustically incoherent in the Northeast Channel and the Stone Fence along the Scotian sediment bodies extendie to about 650 m water depth (Fig. 8). The Margin. These till deposits are visible in sub-bottom profile as surficial expression of the till tongues is pebbles, cobbles, and acoustically incoherent deposits with a rough seabed expression (Figs. 2Band3). Lithology, assessed visually, included abundant crystalline basement rocks resembling granite and gneiss. Visually assessed grain size in these environments was mostly cobbles, small boulders, and pebbles, with coarse sand patches in places between cobbles and boulders (Fig. 4; Mortensen and Buhl-Mortensen, 2004; Watanabe et al., 2009). These areas are swept by strong currents that keep them clear of fine-grained sediments and maintain the habitat suitable for growth of large gorgonian corals. Corals were observed growing on the tops and sides of boulders and cobbles. Lophelia pertusa corals were also observed in the current-swept boulder environment at the Stone Fence, mostly in the form of dead Lophelia rubble (Fig. 5).IntheupperreachesofthethalwegofTheGully,in both side feeder canyons (Figs. 2Cand6) and the main thalweg (Figs. 2Cand,7) boulders of crystalline basement rock were observed. Many of these boulders had been colonized by large colonies of Paragorgia, Primnoa, Keratoisis, and other corals (Figs. 6 and 7).

4.2. Deep-water till tongues

Deep-water till tongues, provide large gorgonian coral habitat Fig. 4. Current-swept cobble-boulder habitat supporting abundant small colonies seaward of Halibut and Haddock Channels, and in Desbarres Canyon, of Primnoa resedaeformis. Stone Fence, 305 m.

SOUTH NORTH 100 SCOTIAN SLOPE NORTHEAST CHANNEL 200

progradational till sheets 200 numerous buried canyons at shelf edge

stratified proglacial sediment Till 300 400 )m(htpedretaW ROPOS 2001 DIVE AREA youngest till tongue

400 stratified proglacial sediment 600 Two-way travel time (ms)

500

600 Tertiary “ bedrock” 800 1km

Fault in Tertiary strata 700

1000 41°52.432’N 41°56.278’N 65°40.995’W 65°45.022’W

Fig. 3. Seismic profile crossing the outer edge of Northeast Channel and the adjacent upper slope. Shows progradational till sheets and the youngest seismically resolvable till tongue. The upper slope is cut by canyons and gullies both at the seafloor and in the subsurface (GI sleeve gun profile from cruise HU2005023). E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S75

boulders resting in a matrix of sand and mud (Fig. 9). In examples along the margins of Haddock and Halibut Channels, on the southwest Grand Banks, cobbles and boulders in a mud matrix, interpreted as till tongues or their related dropstone or debris-flow deposits, extended to approximately 800 m depth. In this facies, individual cobbles and boulders were commonly covered by single or multiple colonies of hard-substrate dependent corals, especially the gorgonians K. ornata and A. armata and the soft corals Anthomastus grandiflorus and Duva florida (Fig. 9). The scattered boulder and cobble in muddy sand matrix facies, interpreted as till tongues, was also observed at Desbarres Canyon, to the southeast of Haddock Channel, along the southwest margin of the Grand Banks (Fig. 2), where nearby seismic profiles show well-developed till tongues (Piper and Gould, 2004, their Fig. 3). The gorgonian coral fauna commonly observed at Desbarres Canyon included the smaller rock-inhabiting gorgonian A. armata and the soft-sediment inhabiting gorgonians A. arbuscula and R. gracilis,butK. ornata was only rarely observed in Desbarres Canyon.

Fig. 5. Remnants of the only known Lophelia pertusa reef in Atlantic Canada, now completely reduced to rubble. Stone Fence, 297 m. 4.3. Eroded friable bedrock and Quaternary glaciomarine sediments

Eroded bedrock was commonly observed in The Gully, and in a few locations in approximately 1000 m water depth near the Stone Fence. In both these environments, corals were observed growing on vertical and steeply inclined surfaces. In The Gully, it was often difficult to determine the orientation of bedding planes in the friable bedrock, although some locations appeared to have shallowly dipping bedding (Fig. 10). Where bedding planes were visible in the exposed mudstone and sandstone bedrock in the deeper areas of the Stone Fence, many of the outcrops appeared to have near-vertical dip (Fig. 11). On the eroded friable bedrock in The Gully, large gorgonians (Paragorgia, Primnoa, Keratoisis) and attached scleractinian cup corals (Desmophyllum) were commonly observed growing hor- izontally from eroded bedrock walls. Soft corals (Anthomastus, Duva, Drifa) were observed growing on the pinnacle tops (Fig. 10). Corals observed on these bedrock exposures near the Stone Fence included a large antipatharian coral, the soft coral A. grandiflorus, and Desmophyllum (Fig. 11). A small ‘gully’ eroded into horizontal, thinly bedded, semi- consolidated sediments was observed at approximately 800 m Fig. 6. Thicket of Keratoisis ornata growing on boulder habitat in the thalweg of the Gully feeder canyon, 600 m. depth seaward of Haddock Channel (Figs. 2E and 12). Although the gully was less than 10 m deep, its exposed walls were covered with a variety of corals, including the gorgonian Keratoisis, the soft coral Anthomastus, and the scleractinian cup corals Desmophyllum and Javania cailleti. Similarly, semi-consolidated slumped sediments in the same area provided firm substrates for the gorgonian Keratoisis, the solitary scleractinians Desmophyllum and Javania, and the large antipatharian S. arctica (Fig. 13).

4.4. Authigenic carbonate crusts

Thin authigenic crusts of cemented sediment, probably calcium carbonate, were observed immediately adjacent to the small gully excavated into the flat-lying semi-consolidated glaciomarine sediments seaward of Haddock Channel (Fig. 14). The crusts appeared to be less than 2.5 cm thick, where exposed in cross-section along the margins of the small gully. The solitary cup corals D. dianthus and J. cailleti were observed growing on the underside of eroded crusts of partially lithified surficial sediment (Fig. 14). Attempts to collect the crust for mineralogical and stable Fig.7. Large Paragorgia arborea, and other coral species growing on crystalline isotopic analysis were unsuccessful, as were attempts to collect boulders, probably glacially transported. Upper part of The Gully, 600 m. the cup corals growing on its lower side. S76 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84

NORTHWEST SOUTHEAST near-seabed till tongue with iceberg scours 400 tips of older youngest till tongues till tongue

400 1km 600

detail in Huntec 800 sparker profile 600 below Water depth (m) 1000

Two-way travel time (ms) 5° 800

44°53.527’N 1200 55°41.726’W 44°48.108’N 55°37.034’W

youngest till tongue

transitional 700 500 (ice-margin) 1km facies

stratified proglacial sediment 800 retrogressive 600 slump

top of proglacial sediment section 900 between till tongues 700 Water depth (m)

Two-way travel time (ms)

1000 800

Fig. 8. Till tongues on the southeast edge of St. Pierre Bank, adjacent to Halibut Channel, shown in airgun seismic profile (above) and detail in Huntec sparker profile (below). Till tongues pass downslope into a short interval of transitional seismic facies and then to well stratified muddy proglacial sediment that in places has undergone retrogressive slumping (data from cruise HU99036; transect N of Piper and Brunt, 2006).

4.5. Fine-grained post-glacial sediments colonies (Mortensen and Buhl-Mortensen, 2005a, b; Watanabe et al., 2009). Fine-grained post-glacial sediments were observed in many Below 750 m in the valleys off Northeast Channel, asymme- areas of the Stone Fence, Haddock and Halibut Channels, and trically rippled sand dominates, with rare large boulders and Desbarres Canyon. Some of these fine-grained sediments sup- outcrops of friable bedrock, which are colonized by gorgonian and ported dense aggregations of sea pens (Pennatulaceans; Fig. 15), other corals (Sameoto et al., 2008; Watanabe et al., 2009). referred to as meadows (cf. Brodeur, 2001), as observed in Although the abundance of hard substrates and the abundance Desbarres Canyon (Fig. 15) and several species of the solitary of Primnoa and Paragorgia corals were significantly correlated, scleractinian cup coral Flabellum. Watanabe et al. (2009) concluded that hard substrate was not limiting to corals in the current-swept boulder environments, because uncolonized hard substrates were observed at most depths. 5. Discussion The current-swept boulder environment of the Stone Fence also hosts the only known Atlantic Canadian deep-water coral 5.1. Shelf-break and upper slope winnowed till reef, built by the colonial scleractinian L. pertusa (Mortensen et al., 2006a). This reef, covering an area of roughly 1 km2, has been Coral assemblages in these environments are dominated by severely damaged by trawling, and is now mostly reduced to the large bushy or fan-shaped gorgonians P. resedaeformis and rubble (Mortensen et al., 2006a; Cogswell et al., 2009). The P. arborea, with lesser abundances of the organic-skeleton boulders composed of crystalline basement rock observed in the gorgonians A. armata and Paramuricea spp. Cobble size may limit upper part of The Gully were probably derived from downslope the size of coral colony, as current drag on corals causes smaller transport of till from the shelf (cf. Fader and King, 2003). The cobbles to overturn, hence limiting the growth of the coral lithology of large clasts in the apparent end moraines observed at E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S77

Fig. 9. Large (41 m tall) colony of Keratoisis ornata, and smaller colony of Fig. 11. Vertically dipping bedrock outcrop colonized by deep-sea corals: large Acanthogorgia armata (yellow) and the soft coral Anthomastus grandiflorus (red) (41 m long) antipatharian coral (possibly a new species of Parantipathes, see growing on small boulder in a till tongue environment of Halibut Channel, Cogswell et al., 2009) along with soft corals (Anthomastus grandiflorus; upper left Southwest Grand Banks, 667 m. Note redfish (Sebastes sp.) and wolffish and lower middle) and cup corals (Desmophyllum dianthus; upper left). Stone (Anarhichas sp.). (For interpretation of the references to color in this figure legend, Fence, 1074 m. the reader is referred to the web version of this article.)

Fig. 12. Eroded horizontal semi-consolidated sediments colonized by deep-sea corals. This small gully approximately 10 m wide and 5–10 m deep was eroded Fig. 10. Eroded mudstone outcrop colonized by deep sea corals: Duva florida into horizontally exposed sediments. The walls of the small gully were colonized (brown soft coral) at upper left, Paragorgia arborea and Primnoa resedaeformis by a variety of corals, including the isidid gorgonian Keratoisis ornata, the large red (pink) in upper center and upper right, long colony of Keratoisis ornata in center- soft coral Anthomastus grandiflorus, and solitary cup corals, mostly Desmophyllum right. Green lasers indicate 10 cm. The Gully, 510 m. (For interpretation of the dianthus. Green lasers are 10 cm apart, and point approximately to the top of the references to color in this figure legend, the reader is referred to the web version of sediment filling the bottom of the gully. Haddock Channel, 797 m. (For this article.) interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) the Northeast Channel, The Gully, and the Stone Fence can be Newfoundland and Labrador region (Gilkinson and Edinger, compared with clast lithologies reported from cores by Piper and 2009). The very high abundance of the large gorgonians Primnoa deWolfe (2003) and Hundert and Piper (2008), derived principally and Paragorgia in the Hudson Strait coral hotspot (MacIsaac et al., from Appalachian basement. 2001; Gass and Willison, 2005; Wareham and Edinger, 2007; Seismic profiles and drop camera studies suggest that the high Edinger et al., 2007a, b) contrasts dramatically with the rest of the abundance of corals in the Hudson Strait coral hotspot is probably shelf break and slope off Newfoundland, where these two species supported by a combination of moraine-derived current-swept are quite rare (Wareham and Edinger, 2007; Wareham, 2009). The boulders and deep-water till tongues (Josenhans and Barrie, 1989; marine geological studies in the area (Andrews et al., 1994, 2001; Andrews et al., 1994, 2001; Rashid and Piper, 2007). This area has Rashid and Piper, 2007) and oceanographic predictions of high the highest coral bycatch rates observed in Newfoundland and current flow (Straneo and Saucier, 2008) suggest that the Hudson Labrador waters (Edinger et al., 2007a, b), matching those of Strait coral hotspot is also supported by a current-swept boulder untrawled areas in the Gulf of Alaska (Krieger, 2001) or the environment similar to that of the Northeast Channel and Stone Tasmanian seamounts (Anderson and Clarke, 2003), and has Fence. This prediction would be consistent with the importance of been suggested to be the most important coral site in the the Hudson Strait as the principal ice stream through which S78 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84

Fig. 15. Meadow of Pennatula spp. (Sea pens) on fine-grained recent sediments. Desbarres Canyon, Southwest Grand Banks, 834 m. Fig. 13. Exposure of semi-consolidated slumped sediment colonized by large colony of S. arctica, and small colonies of Keratoisis ornata and Anthomastus grandiflorus. The S. arctica colony was aged radiometrically at 82731 years (Sherwood and Edinger, 2009). Exposed edges of cemented slumped material Aksu and Hiscott, 1992; Tripsanas and Piper, 2008) and Labrador visible in white. Additional sessile fauna on this substrate included several species Shelf margins (Josenhans et al., 1986)(Fig. 1). of sponges, and the solitary scleractinian coral Javania cailleti. Haddock Channel, The apparent difference in depth-limit between the acousti- Southwest Grand Banks 812 m. cally-recognizable till tongue facies (650 m) and their surface expression as the matrix-supported cobble-boulder facies near Haddock and Halibut Channels may be a function of the resolution of the acoustic profiler, but is more likely related to enhanced meltout of dropstones from attached ice along the ice margin. Where lithology could be assessed visually from video, and based on limited rock samples recovered, the cobbles and boulders appeared to be well-indurated sedimentary rocks, probably from the late PreCambrian sequences on the Avalon and Burin Peninsulas of Newfoundland, the areas that supplied glacial debris to the Haddock and Halibut Channels (Piper and deWolfe, 2003). These are lower-current environments, with general bottom current model predictions of 10–20 cm/s (as opposed to ca. 100 cm/s in the tidally influenced Northeast Channel off Nova Scotia), and directly measured bottom currents of 8–15 cm/s in the Haddock Channel (Zedel and Fowler, 2009). Seismic profiles from Desbarres Canyon show well-developed till tongues (Piper and Gould, 2004; their Fig. 3), supporting our observations of extensive areas of cobbles and boulders in mud matrix within the Desbarres Canyon area. Although we observed Fig. 14. Solitary scleractinian corals Desmophyllum dianthus and Javania cailleti very few of the large gorgonian K. ornata in Desbarres Canyon, this growing on underside of eroded authigenic carbonate crust of partially lithified surficial sediment adjacent to small gully eroded into horizontal glaciomarine species was recorded in fisheries bycatch from the Desbarres sediments, probably Pleistocene in age. The crusts, and possibly the small gully, Canyon area (Wareham and Edinger, 2007). Fishing effort, are likely related to cold seep activity. Haddock Channel, 797 m. especially trawling effort, is much higher around Desbarres Canyon than in the Haddock and Halibut Channel areas (Edinger Laurentide ice sheet glaciers reached the Labrador Sea (MacLean, et al., 2007b), suggesting that the dearth of K. ornata in the 2007 2001; Piper, 2005; Shaw et al., 2006). surveys of Desbarres Canyon may be a function of fisheries- induced damage. Although there are several records of fisheries bycatch of P. arborea in the Haddock Channel, very few of these 5.2. Deep-water till tongues larger corals were observed during our surveys, and none during the 2002 drop video surveys conducted in the area in waters Presence of till tongues in Halibut and Haddock Channels and shallower than 500 m (Mortensen et al., 2006b). The rarity or Desbarres Canyon is confirmed by seismic-reflection profiles absence of Primnoa and Paragorgia from the Southwest Grand (Halibut and Haddock Channels, Mosher et al., 2010, their figures Banks sites may also reflect the low current regime; Primnoa and 3.2.15 and 3.2.16; Desbarres Canyon, Piper and Gould, their Paragorgia tend to be found in areas of high current flow (Bryan Fig. 3). Trough-mouth tills are associated with the locations of ice and Metaxas, 2006). Alternatively, the rarity of these species, streams during deglaciation of Atlantic Canada (Shaw et al., 2006), which tend to be found shallower than Keratoisis and Acantho- and are expected to provide the basis for concentrations of gorgia (Gass and Willison, 2005; Mortensen et al., 2006b; Paramuricea and the antipatharian coral S. arctica in deep waters Wareham and Edinger, 2007), may also reflect the result of near trough mouths along the Northeast Newfoundland Shelf decades of trawling (Kulka and Pitcher, 2002) on the continental (upper slope off Trinity Trough, locally known as Tobin’s Point, shelf and upper slope. E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S79

5.3. Eroded friable bedrock and Quaternary glaciomarine sediments other mineral crust formation (e.g. Bohrmann et al., 1998). The thinness of the authigenic crusts, apparently limited spatial Deep-sea corals in The Gully were commonly observed on extent and existence along the margins of an erosional feature eroded friable Tertiary mudstone, in an environment resembling within horizontally bedded semi-consolidated sediment suggest underwater badlands. The exposed mudstone outcrops in The cementation related to cold seep activity. Cold seep activity has Gully are thought to be a product of subglacial meltwater erosion been reported at much greater depths in the Laurentian Fan (Fader and King, 2003; Piper, 2005). Coral growth on similar (Mayer et al., 1987). eroded bedrock was reported from The Gully by Mortensen and Buhl-Mortensen (2005b). Coral growth on eroded bedrock was 5.5. Coral assemblages on fine-grained post-glacial sediments also noted in the Northeast Channel (Scott, 2003; Watanabe et al., 2009). The abundance of post-glacial mud in many areas was not We hypothesize that low shear strength of the bedrock may surprising. A dramatic difference in the coral assemblages limit size, shape and species composition of deep-sea corals in between muddy environments and the various hard-substrate many parts of The Gully. Friable bedrock outcrops frequently had environments was also expected. Sea pens anchor in soft large colonies of the elongate gorgonian Keratoisis, but only small sediments, using hydrostatically inflatable pedicles, while Flabel- colonies of the bushier gorgonians Paragorgia and Primnoa. These lum lies semi-reclined in the mud. Because antipatharians, most bushy corals exert a much higher shear stress on the bedrock than gorgonians, and most scleractinians require hard substrates, they would Keratoisis, given the same current regime. Detached were not observed in muddy habitats, with the exceptions of the moderate size colonies of Paragorgia were observed lying at the smaller gorgonian species A. arbuscula and R. gracilis, both of base of outcrops, having detached from the friable bedrock with which have root-like holdfasts that anchor the corals within their holdfasts intact, but often with a thin layer of bedrock sandy sediment. These two gorgonian species occur at much remaining on the bottom part of the holdfast. This limitation also greater depth than the other gorgonians, which depend on hard likely applies to exposed bedrock in the Northeast Channel (Scott, substrates (Wareham and Edinger, 2007; Baker et al., 2008; 2003); although bedrock exposures in the Northeast Channel are Wareham, 2009; Cogswell et al., 2009). relatively uncommon in comparison with The Gully (Cogswell et al., 2009; Watanabe et al., 2009). Single colonies of the solitary scleractinian D. dianthus were also observed on eroded bedrock 5.6. Overview of interpreted relationship between geology and coral features in The Gully during a 2006 cruise using the Canadian distributions. Navy DSIS ROV (D.B. Scott, unpublished). The near-vertical dip of the exposed bedrock outcrops seaward As indicated in Fig. 1, there is a general correspondence of the Stone Fence suggests that they may represent near-surface between major glacial geological features that provide hard slumps of the type described by Hughes-Clarke et al. (1989). The substrates at shelf-break and slope depths and the abundance of antipatharian corals photographed on the deep eroded bedrock skeletal deep-water corals along the continental margin of facies in the Stone Fence (Fig. 11) may represent a new species of Atlantic Canada. Fig. 16 summarizes the relationships among Paranthipathes (Cogswell et al., 2009). the geological features discussed in this paper, and between the The horizontally bedded semi-consolidated sediment observed geological features and the corals growing on them, in the form of seaward of Haddock Channel is probably composed of Pleistocene a block diagram. The block diagram depicts the relative, rather glaciomarine sediments (Mosher et al., 2010). Off Halibut than absolute, depth distributions of the five types of geological Channel, both the small gully eroded into the semi-consolidated features discussed in this paper. For example, the current-swept sediment, and the weakly consolidated slumped material may be ice-contact sediments are found at considerably greater depth in related to the 1929 Grand Banks earthquake and turbidity current, the Hudson Strait, Northern Labrador than in the Northeast although regionally no failures have been previously confirmed Channel and Stone Fence, Nova Scotia (see Piper, 2005). east of Halibut Channel (Armitage et al., in press). Necessarily, the till tongues are always found at greater depths A colony of S. arctica growing on top of the weakly than the current-swept ice-contact sediments, and have been consolidated slumped material was aged at 82731 years using described from the mouths of many of the shelf-crossing troughs bomb radiocarbon (Sherwood and Edinger, 2009). The slumped of the Newfoundland and Labrador continental margin (Piper, material may have originated as a rotational slump (cf. Piper et al., 2005; Shaw et al., 2006, and references therein). The exposed 1999), but no slump headscarp was observed, and the slump was steep bedrock outcrops are found at a variety of depths in the not discernable in multibeam sonar, which had a pixel size of Northeast Channel, The Gully, and The Stone Fence (Watanabe approximately 40 m (Fig. 2E). et al., 2009; Mortensen and Buhl-Mortensen, 2005b; Cogswell et al., 2009, respectively), not necessarily at depths below 1000 m. Eroded consolidated Quaternary sediments and authigenic 5.4. Authigenic crusts carbonates are suggested to be related to fluid flow along lines, consistent with our understanding of the Laurentian Fan Growth of corals on authigenic crusts has been reported region (Mayer et al., 1987; Mosher et al., 2004) and elsewhere. In elsewhere in cold seeps and other deep-sea environments (e.g. general, eroded Quaternary sediments are thought to be more Hovland and Risk, 2003; Schroeder, 2007; Foubert et al., 2008a). common than eroded Tertiary bedrock along the shelf break and White filamentous slime related to hydrocarbon release has been upper continental slope of Newfoundland and Labrador (Piper, found on the Grand Banks (Fader, 1989). 2005). Authigenic carbonates may also occur on Orphan Knoll The origin of the crusts off Halibut Channel is unknown, but (Enachescu, 2004), although exposed pinnacles on Orphan Knoll may be related to seabed seepage of hydrocarbon and associated could also be eroded remnants of Paleozoic bedrock (Parson et al., formation waters (Mosher et al., 2004), perhaps accelerated by 1984; van Hinte et al., 1995). seabed failure in 1929 (Piper et al., 1999). The relationship The large skeletal coral fauna depicted on the different between the crusts and the excavation was unclear, as was the geological facies represents a summary of previously published potential relationship between the crusts and cold seep activity, research on coral distributions in relation to substrates (Mortensen which is widely recognized as a trigger for deep-sea carbonate or and Buhl-Mortensen, 2004, 2005a, b; Mortensen et al., 2006a, b; S80 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84

Coral species: Bank Pa: Paragorgia arborea Winnowed Till Pr: Primnoa resedaeformis Sand and Gravel Corals: Pr, Pa, Ac,Ke, Lo; Ac: Acanthogorgia armata Aa: Acanella arbuscula Figs 4, 5, 6, 7; Refs 1, 2, 4, 5, 6, 10. Mud Drape Lo: Lophelia pertusa Ke: Keratoisis ornata Till AN: Antipatharians Transverse Tongue De: Desmophyllum dianthus 200 Trough Corals: Ke, Ac, Aa, AN; Ja: Javania cailleti Fig. 9; Refs 5, 6, 7, 8, 9 300 boulders in proximal glaciomarine 400 sediment Quaternary Till Eroded Canyon 500 Quaternary Corals:Ke, Ac, De, Ja, AN Fig12, 13; Ref. 8, 9

m 600 Authigenic 700 Crust Corals: De, Ja, 800 Tertiary Figs. 13, 14; Refs 8, 9

900 Quaternary Eroded Bedrock 1000 Glaciomarine Shallow (The Gully) Corals: Pr, Pa, Ke, De cold seep? Fig 10; Refs 3, 4, 10 Deep (Stone Fence) Corals: De, AN Fig.11; Ref. 10.

Fig. 16. Interpreted summary relationship between major geological features, and between geological features and skeletal coral distributions in Atlantic Canada. Geological features include winnowed till, till tongues, eroded bedrock, eroded Quaternary sediments, and authigenic crusts. Depth ranges are relative, not absolute. The eroded bedrock facies also occurs in a wide depth range from shallow to deep in The Gully. Coral taxa indicated by initials. Antipatharians (AN) include Stauopathes arctica (Wareham and Edinger, 2007; Baker et al., 2008; Wareham, 2009) and a potentially new species of Parantipathes from the Stone Fence (Cogswell et al., 2009). Generalized coral distributions on substrates based on qualitative in-situ observations and published sources, and represent hypotheses to be tested in future detailed papers on specific areas, using quantitative data on coral species compositions on different geological feature types. Numbers for published data sources: 1: Mortensen and Buhl-Mortensen (2004),2:Mortensen and Buhl-Mortensen (2005a),3:Mortensen and Buhl-Mortensen (2005b),4:Mortensen et al. (2006a),5:Mortensen et al. (2006b),6:Gass and Willison (2005),7:Wareham and Edinger (2007),8:Baker et al. (2008),9:Wareham (2009), and 10: Cogswell et al. (2009).

Cogswell, et al., 2009; Watanabe et al., 2009)andourqualitative et al., 2006b; Wareham and Edinger, 2007; Baker et al., 2008; in-situ observations. The large gorgonians Primnoa and Paragorgia Wareham, 2009; Cogswell et al., 2009). These species are and the colonial scleractinian Lophelia appear to be most common generally found over a greater depth range than Primnoa and on the winnowed till facies (Mortensen et al., 2006a, b; Watanabe Paragoria (Wareham and Edinger, 2007; Baker et al., 2008; et al., 2009), and on the eroded bedrock facies in sites such as The Cogswell et al., 2009). Many of these species can tolerate the Gully (Fig. 16). These sites coincide with strong bottom currents, high current strengths at the winnowed till and eroded bedrock suggesting that current strength is a strong predictor of these facies, yet also grow in low current environments found on some species distributions (Bryan and Metaxas, 2006, 2007). Without the of the till tongues (e.g. Zedel and Fowler, 2009). Till tongues may moraines or bedrock to provide hard substrates, however, strong be the most common features that deliver hard substrates to currents may not be sufficient to sustain populations of these deeper, lower current, areas of the upper continental slope along corals (see Etnoyer and Morgan, 2007). Both current strength and paraglacial continental margins. Ice-rafted debris may be another geological facies probably influence the distribution of these important source of hard substrates upon which corals can grow species (Mortensen et al., 2006a, b). in paraglacial settings. The gorgonians K. ornata and A. armata, and the antipatharians, The eroded Quaternary sediments and authigenic crusts were are all dependent on hard substrates, and were observed on a each observed at only 1 site in our 2007 mission, although both wide range of geological features, with K. ornata and A. armata the types of features have been previously reported in Atlantic most common large skeletal corals on the till tongues seaward of Canada, especially in the Laurentian Fan region (Mayer et al., Haddock and Halibut Channels (in-situ observation Mortensen 1987; Piper et al., 1999; Mosher et al., 2004; Piper, 2005). et al. 2006 and this paper, and coral bycatch data, Mortensen Observations on the coral fauna of these features are necessarily E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 S81 limited, but included a variety of skeletal and non-skeletal species one species, the nephtheid soft coral Gersemia rubiformis, has also on the eroded Quaternary sediments, but only solitary scleracti- been recorded in shallow water or in fjords (Dale et al., 1989; nian corals on the exposed underside of the authigenic crusts (see MacIsaac et al., 2001; Copeland et al., 2008). On Banquereau, a Sections 4.3 and 4.4). The solitary scleractinian coral D. dianthus sandy bank offshore Nova Scotia, the soft coral G. rubiformis was often occurs on vertically exposed hard substrates that shelter it observed to attach to empty mollusk shells at frequencies Z84% from sedimentation (Cairns, 1981; D.B. Scott, unpublished (Gilkinson et al., 2005). In Newfoundland and Labrador waters, observations, 2006; Cogswell, et al., 2009). In our observations, most other coral species are probably restricted from fjords and these vertical hard substrates included eroded bedrock, eroded shallow shelf environments by seasonal sub-zero surface water and/or slumped Quaternary sediments, and authigenic crusts. As a temperatures associated with the Labrador Current. An exception summary of the published literature and our qualitative observa- to this pattern are a few of the deep ‘‘warm-water fjords’’ along tions, the illustrated distributions of corals among the geological the south coast of Newfoundland, which contain Labrador slope facies represent hypotheses to be tested in future publications water that remains 51 C or warmer year round, in which the soft using quantitative data on coral species composition among the coral A. grandiflorus was recorded (Haedrich and Gagnon, 1991). geological facies, from the various regions we have studied. Off Nova Scotia, warm surface waters in summer restrict many coral species to slope depths (Mortensen et al., 2006b). 5.7. Comparison with other regions 5.7.2. Non-paraglacial continental margins With the exception of the seapen meadows, hard substrates Where cold-water coral reefs and concentrations have been are fundamental to all the types of coral habitat described. The described from areas outside major glacial influence, the origins of general origins of coral habitats observed along the Atlantic hard substrates supporting coral growth are generally exposed Canadian continental margin are similar to origins observed along bedrock, eroded semi-consolidated sediment, shelf-break fluvio- other paraglacial continental margins. The origins of the hard deltaic gravels, and current-winnowed hardgrounds (Wheeler substrate features differ markedly among paraglacial continental et al., 2007). In Alaskan waters, coral density is highest on margins, continental margins not subject to glacial erosion and bouldery island-arc shelf and slope features of the Aleutian Islands sedimentation, and non-continental regions such as seamounts. (Stone, 2006), but these environments experienced little or no direct impact of glaciation, and are isolated from continental terrigenous sedimentation. Along the European margin south of 5.7.1. Paraglacial continental margins Scandinavia, Lophelia reefs initiated upon coarse gravels associated The patterns of erosion and sedimentation observed along the with lowstand paleo-deltas (e.g. Stewart et al.,this issue)and Atlantic Canadian margin are typical of paraglacial continental erosional features. Corals commonly occur along the flanks of shelves, with transverse shelf-crossing troughs, shelf-break till submarine canyons, on eroded bedrock scarps (e.g. Huvenne et al., deposits, deep-water till tongues, and yet deeper trough-mouth 2008), analogous to the erosional features supporting coral growth fans (O’Cofaigh et al., 2003). Cold-water corals are common in in The Gully as described here and by Mortensen and Buhl- paraglacial shelf and slope settings such as the Norwegian Mortensen (2005b). For many of the large carbonate mounds on continental margin and the Canadian Pacific and Atlantic banks at the edge of the European margin (e.g. Porcupine Bank, continental margins. Along the continental shelf and slope of Hatton Bank, Rockall Bank), cold-water coral reef growth initiated Norway, cold-water L. pertusa reefs have become established on a on bedrock, coarse siliciclastic deposits, or hardgrounds (Noe´ et al., variety of bottom features, including bedrock ridges (Mortensen 2006; Wheeler et al., 2007; Weinberg et al., 2008), but beneath et al., 2001; Freiwald et al., 2002), elevated hard substrates in larger mounds the original settlement surface has been obscured glacial till associated with Pleistocene iceberg ploughmark berms by successive generations of carbonate mound development, with (Freiwald et al., 1999), cold seeps (Hovland and Risk, 2003), or corals re-establishing reef growth upon the mound after a hiatus even isolated boulders in sandy channels subject to strong of thousands of years or more (e.g. Foubert et al., 2008b). unidirectional currents (Mortensen et al., 2008). On the Sula In the Gulf of Cadiz, cold seeps contribute to formation of hard ridge, offshore Norway, variation in bedrock resistance to erosion substrates that supported coral growth (e.g. Foubert et al., 2008a; contributes to the shape of the ridge on which the corals grow, Mienis et al., 2008). Similarly, cold seeps are the primary although iceberg ploughmarks appear to have had a greater mechanism generating hard substrates that support L. pertusa influence on reef distribution than the bedrock itself (Freiwald reef development in the Gulf of Mexico (Schroeder et al., 2005; et al., 2002). Although iceberg ploughmarks and associated berms Schroeder, 2007), and support a wide variety of hard-substrate have been recorded in great abundance from the Newfoundland dependent epifauna surrounding cold seeps (e.g. Callender et al., and Labrador shelves (Josenhans and Barrie, 1989; Cameron 1990). Although the authigenic carbonates described from and Sonnichsen, 1992) and on the upper Scotian Slope (Piper and Haddock Channel may have been related to a small cold seep, Campbell, 2002), very few of the coral occurrences observed to most of the coral habitat encountered along the Canadian date along the Atlantic Canadian margin has been recognized as continental margin was paraglacial in origin. Similarly, while associated with iceberg ploughmark berms. most of the coral habitat in the Hudson Strait and Baffin Bay is In some fjords and coastal inlets in Norway, British Columbia, probably derived from ice-contact sediments or till tongues New Zealand, and Chile, corals and sponges are concentrated in (see Section 4.1), a spatial correspondence between apparent locations where tidal currents are amplified by sills or other hydrocarbon seepage and concentrations of cold-water corals in restrictions (e.g. Nordgard,˚ 1921; Mortensen et al., 2001; the Hudson Strait area has been recently documented (C. Jauer, Tunnicliffe and Syvitski, 1983; Grange, 1985; Haussermann and Geological Survey of Canada, pers. comm., March 2009). Forsterra, 2007). Large gorgonian and scleractinian corals and reef-forming sponges on Canada’s Pacific continental margin occur on a variety of hard-substrate features, including boulder- 5.7.3. Non-continental-margin settings. sized fragments of glacial drift (Tunnicliffe and Syvitski, 1983; In non-continental-margin settings, seamounts often harbour Conway et al., 2005; Edinger et al., 2008) and bedrock ridges dense growth of cold-water octocoral and colonial and solitary (Conway et al., 2007; Edinger et al., 2008). Of the coral species scleractinian corals (e.g. Koslow et al., 2001; Stone, 2006; Rogers observed along the Atlantic Canadian continental margin, only et al., 2007; Cairns, 2007). Isolation from continental sources of S82 E.N. Edinger et al. / Continental Shelf Research 31 (2011) S69–S84 sediment appears to favour growth of corals and other long-lived A. Cogswell, K. MacIsaac, R. Benjamin, and other Bedford Institute sessile benthos on seamounts (Rogers et al., 2007). Although of Oceanography scientists and staff for their contributions at sea several sets of seamounts occur off the continental margin of and post-cruise. We thank A. Metaxas, P. Snelgrove, P. Lawton, and E. Atlantic Canada, most are quite deep and have not been Kenchington for allowing EE to participate in the 2006 Discovery investigated by drop-video, submersible, or ROV. The Newfound- Corridor cruise to the Northeast Channel. Vessel time on CCGS land Seamounts, Fogo Seamounts, and Orphan Knoll have some Hudson for 2006 and 2007 was provided by Fisheries and Oceans corals including recent and subfossil D. dianthus (e.g. Smith et al., Canada Maritimes Region through E. Kenchington. 2001 and 2006 1997), and have been studied geologically, but coral habitats in ROPOS cruises were jointly funded by NSERC ship-time grants and these areas have yet to be investigated using in-situ means. The Fisheries and Oceans Canada. 2007 ROPOS time was jointly funded New Seamounts, near the boundary between Canadian through a NSERC ship time grant to A. Mercier and others, and DFO and US waters, support dense communities and diverse assem- Science Branch International Governance of High Seas Fisheries blages of corals and other sessile epifauna (e.g. Moore et al., 2004; Program grant to KDG and others and DFO Maritimes Science and Cairns, 2007), except where they have been impacted by fishing Oceans branches funding to E. Kenchington. 2001 ROPOS cruise was (Waller et al., 2007). supported by Fisheries and Oceans Canada and by an NSERC ship time grant. Geological Survey of Canada vessel time supported by the Canada Program for Energy R&D through the Geological Survey 6. Conclusions of Canada. Research was supported by an NSERC post-doctoral fellowship to OAS, NSERC Discovery grants to EE and DBS, and DFO Quaternary and surficial geology exert a crucial influence on the grants to KDG. 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