Research

INTRODUCTION

Worldwide, Arctic ecosystems and communities experience more accelerated and pronounced impacts of climate change than those in other parts of the world. In Canada, the Arctic region has warmed and will continue to warm at more than double the global rate (Bush and Lemmen 2019). The consequences of increased Arctic warming and other climate-induced environmental changes include complex social and cultural impacts to Inuit and their livelihoods, and significant shifts in marine and terrestrial ecosystems result from changing distributions of marine species and loss of habitat (Cunsolo Willox et al. 2012, Ford et al. 2012). Because of the rate of climate change, these impacts are expected to intensify in the near future (Post et al. 2019). Unprecedented annual warming since 1993 in Nunatsiavut has caused a recent reduction of ice cover over both land and sea, as well as a significant change in the salinity of fjords (Allard and Lemay 2012). Ice cover is a critical platform used by Inuit, as it provides access to traditional hunting grounds and other important places.

Nunatsiavut is the Inuit settlement region in Labrador, which is established by the Labrador Inuit Land Claims Agreement (LILCA). The Nunatsiavut Government, the Inuit regional government of Nunatsiavut, was formalized in 2005 with the signing of LILCA. The LILCA established approximately 72,000 km² of the Labrador Inuit Settlement Area (LISA), including 48,690 km² of coastal and marine areas.

The coastal and marine environments in Nunatsiavut are influenced by climate, ocean currents, topography, and ice cover (Allard and Lemay 2012). The fjords, fjards, bays, and archipelagos that form the coastline of Nunatsiavut are dominated by the Labrador Current, the east Baffin Island current, and outflow from the Hudson Strait (Chapman and Beardsley 1989, Lazier and Wright 1993, Piper 2005, Coté et al. 2018). Fjords are characterized by narrow, muddy basins up to 300 m deep, separated by rocky sills (walls), and flanked by steep cliffs up to 1000 m high. Fjards are shallow, irregularly shaped inlets less than 150 m deep, with gently sloping sidewalls and large intertidal zones (Allard and Lemay 2012, Brown et al. 2012). Fjords and fjards in Nunatsiavut host boreal flora and fauna, and they are important feeding areas for marine megafauna, including marine mammals and seabirds, and important food species like Arctic char (Salvelinus alpinus; Dempson et al. 2002, Allard and Lemay 2012, Brown et al. 2012). This richness has provided food and livelihood for Labrador Inuit over hundreds of years. Hebron is an example of a fjord in this region of Nunatsiavut, whereas Okak Bay is considered a fjard (Allard and Lemay 2012, Brown et al. 2012, Carpenter et al. 2020). Commercial fishing by a range of bottom contact gear types are concentrated offshore on the shelf and slope waters. Arctic char and Atlantic salmon (Salmo salar) support both subsistence and commercial fisheries and there is a small commercial dredging operation for Icelandic scallop (Chlamys islandica) fishery around the Nain area (Coté et al. 2021, McCarney et al. in press).

Polynyas are areas of open, unfrozen ocean in an area of otherwise continuous seasonal ice. In coastal areas, like in the Nain archipelago, offshore wind and water currents help in the creation of an ice-free area that is dynamic in boundary but consistently open during the ice season when the surrounding marine area is covered by sea ice (Pikialasorsuaq Commission 2017). Polynyas allow harvesting and hunting opportunities to Inuit that would otherwise be inaccessible during winter months (QIA 2018). These areas have higher productivity than ice-covered areas because of penetration of sunlight into the water column, producing early plankton blooms that provide energy up through food webs to support benthic productivity and megafauna like seabirds, marine mammals, and humans (Grebmeier and Barry 2007, Pikialasorsuaq Commission 2017). Locally, polynyas are known as rattles, where they are defined by fast ocean currents. Labrador Inuit hunt in these dynamic areas along the Nunatsiavut coast for seabirds and seals (Brice-Bennett 1977).

The Nunatsiavut Government established the Imappivut (“Our Oceans”) initiative and designed it to represent the intricate relationship that Labrador Inuit have with the coastal and marine environment. Imappivut is guided by the values, knowledge, and interests of Labrador Inuit and the best available knowledge of the marine environment. Imappivut celebrates the connections Labrador Inuit have with the marine environment and works to contribute to the health and well-being of Labrador Inuit by recognizing their interdependence with their ecosystems. Labrador Inuit have expressed a range of priorities and concerns related to the marine environment (Durkalec et al. 2015, MacDonald et al. 2015). Because they consider themselves an interwoven expression of nature within a social-ecological system and not distinct from their environment, Nunatsiavut communities, including Inuit youth, are concerned about the impacts of climate change on their health, livelihoods, and future access to marine resources, including fisheries. These concerns are growing with increasing evidence suggesting impacts to traditional practices, including hunting, access, and species abundance, and the effects on both the individual and broader social and cultural systems (Power et al. 2012, Durkalec et al. 2015, MacDonald et al. 2015, DFO 2021, McCarney et al. in press).

Although the region is rich in Inuit knowledge, there remain significant research gaps in coastal ecology and oceanography because of the nature of the environment, the limited availability of research vessels, and prioritization of research resources toward projects that are driven by or connected to industry. The Nunatsiavut Government has stated that it is a priority to fill these important data gaps with both Inuit knowledge and Western scientific knowledge (for a definition of knowledge systems see Zurba et al. 2021) to help inform fisheries and marine planning and processes, and to increase public awareness about the unique, diverse, and sensitive marine biodiversity and habitats in Nunatsiavut’s Zone (DFO 2021, McCarney et al. in press). This includes the Imappivut Marine Planning Initiative that was developed through consultations with Labrador Inuit to incorporate their values and priorities. The initiative captured the stories and knowledge that substantiate the close relationship Labrador Inuit have with their environment.

The objective of this study was to help fill gaps in ecological knowledge in areas of high cultural significance to Inuit in the marine environment of Nunatsiavut. We aimed to understand patterns of distribution and abundance of key taxa including the identification of vulnerable marine ecosystems (VMEs) characterized by functionally significant and fragile indicator species, such as corals and sponges, that provide structural complex habitats (e.g., Long et al. 2020). The work is of relevance to, and informed by, Labrador Inuit and the Imappivut Marine Planning Initiative. Our contributions included surveys of a fjord, a fjard, and a coastal archipelago rich in polynyas. The 2019 Imappivut Expedition described patterns of epibenthic diversity and species assemblages in northern Nunatsiavut while sharing knowledge, resources, and expertise with local Inuit youth and community members (https://protectoceans.ca/expeditions/imappivut/).

METHODS

We identified the expedition priorities through collaborative planning among project partners, including Inuit (who have a unique perspective on the value of the region), informed by previous research (e.g. McCarney et al. in press) and community engagement efforts, carried out by the Nunatsiavut Government as part of the Imappivut initiative. We chose specific sites for their ecological, social, and cultural importance to the region and Labrador Inuit. We investigated the potential influence of depth, seafloor substrate type, and assemblages on species diversity in the fjords and channels around Hebron and Okak. These are former Inuit communities of deep historical significance and are still frequented as a source of food, and that hold great cultural and spiritual significance. The third area was in an island archipelago with numerous polynyas near the community of Nain.

The Imappivut expedition took place from 19 to 27 August 2019, during the ice-free period, aboard M/V Leeway Odyssey. Marine benthic surveys were conducted in three areas, Hebron Fjord, Okak Fjard, and the Nain archipelago (Fig. 1, Table 1), using a camera sled and a baited remote underwater video system (BRUVS). In addition to the traditional and social significance to Labrador Inuit, sites were selected based on depth, exposure, and coarse descriptions of bathymetry and habitat information where available. CTD data were not collected based on uniform salinity and temperature profiles available in the literature (reviewed in McCarney et al. in press). Permits for operations and sampling were provided by the Nunatsiavut Government.

Site selection

Hebron is well-known for its abundance of natural resources important to Labrador Inuit and continues to be a prominent hunting and fishing area that once sustained one of the largest communities of Nunatsiavummiut. It was also unique in that it was a common meeting site for peoples across the region and remains one of the most culturally important and significant sites in Nunatsiavut (Loring and Arendt 2009). Inuit lived a nomadic lifestyle and inhabited these areas long before they were made missionary sites. Moravian missionaries established missions to influence Christianity on Inuit in Labrador in the late 1700s, with posts in various areas in Labrador, including Hebron, Okak, and Nain. In 1959 Hebronimiut (Labrador Inuit living in Hebron) were abruptly relocated from their homelands when the Newfoundland and Labrador Government decided they would no longer provide services such as health care, education (church), and economic support in Hebron.

Similarly known for its ready access to important hunting and fishing sites in the past and today, Okak Bay and its surrounding areas was unique in that it was one of three sites engaged with whale hunting in the fall and offered unobstructed travel routes to offshore islands in the winter (Woollett 2007). Okak was the largest Inuit settlement in Labrador until the Spanish flu decimated the community in 1918, killing nearly all Inuit and forcing the survivors to abandon the town and relocate to other settlements in Nunatsiavut.

The island archipelago surrounding Nain has contributed to a long history of rich hunting and fishing grounds. When the northernmost communities were greatly affected by the closures of the Moravian churches they had become accustomed to, Inuit were forced out and relocated to other communities, including Nain. Today, Nain is the most northern and the largest community in Nunatsiavut, with approximately 1190 residents.

The deepest sampling site was referred to as Hebron 1 (outer fjord) and the site at the sill was Hebron 2 (inner fjord). Sampling summary details for all sites are in Table 1 (depth profiles are in Fig. A1.1). In Okak Fjard, sites 1 and 3 were on the outer exposure of the fjard, while site 2 was within the fjard. The two outside exposure sites at Okak represented benthic habitats of different depths. In the Nain archipelago, sampling was conducted at two sites. The first site was located near Sandy Island, in a deeper, outer portion of the archipelago. The second site was located between Hillsbury Island and Paul Island and spanned two different habitats, both inside and outside a well-known polynya that is of local importance for hunting and known to be highly productive (DFO 2021, McCarney et al. in press). Both sites surveyed in the Nain area were between 19 and 75 m in depth, shallower than the other areas surveyed (Table 1, Fig. 1, Fig. A1.1).

Collectively, samples at these sites captured the range of both soft and hard (cobble and pebble) seafloor substrates in this region (Fig. A2.2). However, large boulder habitat and sites dominated by kelp were underrepresented in our survey because of their unsuitability for sled deployment.

Video transects and drop surveys

A total of 17, one kilometer long video transect surveys combined with drop camera sampling at random stations along the transects were conducted within the three study locations of Hebron Fjord (sites = 2, transects = 3), Okak Fjard (sites = 3, transects = 7), and Nain archipelago (sites = 2, transects = 7), in depths ranging from 19 to 234 m (Table 1, Fig. 1). Seafloor video surveys were conducted using a towable sled (1.27 m long × 0.91 m wide × 0.79 m high) deployed via the vessel’s A-frame winch (Fig. 2). A Sony FDR X3000 action camera encased in an Abysso Group B housing was attached to the sled’s frontal area. The camera was positioned 41.3 cm above the sled runner at a 30° downward angle. The camera was set to record at 60 frames per second in 1080p quality (resolution: 1920 × 1080). Two wide-beam Nautilux lights (each with 3 Cree XML LEDS) in a GPH-1750m housing were placed on both sides of the camera and provided a constant source of illumination of the seafloor (2000 lumen setting, 4000 K neutral white color, Group B Distribution Inc.). Because a real-time view of the seafloor was not available with the system used in this study, the sled was operated in “drop camera” mode. See Appendix 1 (supplementary methods) for details on sled operation at each site. Drop camera images provided the means to quantify differences in epibenthic fauna community within and between sites, although the number of quadrat images from the two sites at Hebron was reduced because of equipment loss and damage.

Baited remote underwater video system (BRUVS) surveys

A total of 15 BRUVS deployments were conducted during the expedition within the three study locations of Hebron Fjord (n = 4), Okak Fjard (n = 6), and Nain (n = 5), at depths ranging from 23.6 m to 234 m (ship’s position). BRUVS were deployed in the vicinity of sled transect locations, with each deployment having an average soak time of four hours. BRUVs were deployed either at a different time than the video transects and/or at least two km from the transect locations to prevent any influence on mobile fauna observations. The baited camera frame (Fig. 2) consisted of a camera (SubC 1Cam Mk 6), battery, LED light (SubC Imaging Inc.), and bait. The camera was set to record in high-quality 4K format (resolution 3840 × 2160) at 30 frames per second and had parallel lasers (6.2 cm apart) as a measurement scale. The camera was positioned in a downward-looking angle toward the bait arm of the frame, which was located 50 cm off the seabed. Approximately 2–3 kg of squid was placed inside the bait bag and approximately 1 kg of squid was attached to the outside of the bait bag at each deployment.

Drop camera analysis

Image frame grabs of each drop were extracted from video for each station using VLC software (VideoLAN 2021). Drop images were considered suitable for analysis if the image was sharp and the field of view was not obscured by clouds of sediment or distorted because the sled was not in an upright position. If judged necessary, valid images were edited in ImageJ (Abramoff et al. 2004, Rasband 2018) to improve quality through sharpening and adjusting brightness, contrast, and color.

Perspective grid limits were used to define standardized dimensions of a useable field of view (Wakefield and Genin 1987). Only drop images in which all organisms were clearly visible in the field of view were selected for quadrat analysis. Based on the perspective grid template, the fixed field of view for quadrat analysis comprised 130 grid cells, each 5 × 6 cm (30 cm²), which produced a total quadrat area of 0.39 m². This area was held constant across all analyzed quadrat images to allow a standardized assessment of substrate and fauna across the surveyed sites. In some instances, some grid cells in a quadrat image were obstructed by turbidity and were excluded, and for these quadrats only the visible surface area was used for assessment, with taxa densities calculated accordingly. See Appendix 1 (supplementary methods) for details on the perspective grid set up.

The amount of each unique substrate type in each quadrat image was quantified by summing the number of 30 cm² grid cells where a given substrate type was present. Because multiple substrates may have been present in a single grid cell, for example, macrophytes attached to cobbles, the total surface area of substrate recorded in a quadrat could be greater than 0.39 m². Furthermore, the spatial area recorded for a given substrate in a quadrat is an approximation, as a substrate would be counted within a grid cell, even if it did not occupy 100% of the cell area.

Fauna were classified to the lowest taxonomic level possible using the video images. However, because no voucher specimens could be collected, in most cases identification was provided at the taxonomic level above genus (e.g., sponges were identified at the phylum level). Accordingly, because some of the taxa reported here likely represent multiple species, the actual number of species present at these sites is expected to be higher than the number of unique taxa reported. Still, general patterns of richness and diversity may hold true despite the lack of fine taxonomic resolution (Cusson et al. 2007).

All drop image annotations were conducted by the same researcher to reduce inter-annotator variation and uncertainty. Identifying and counting benthic megafauna was performed conservatively using the following criteria: if unsure of what taxon is present, count the observation as “unknown”; only count individuals with at least half of their main body within the field of view (e.g., half of the main disk of an ophiuroid); and exclude macroalgae from these observations. Evidence of human disturbance, such as debris or dredge marks, were also recorded.

Video transect analysis

In addition to the drop camera (quadrat) imagery, videos between drops were also annotated and analyzed. The analysis was qualitative, as sled speed and distance from the seafloor were not constant, which in many cases made annotation challenging (e.g., sled going too fast). Each video transect was watched twice by the same annotator to extract qualitative fauna and habitat data. The abundance of dominant benthic invertebrates was estimated in quantities of 10s or 100s. Aggregations of > 10 individuals from one taxon within a field of view was defined as a “field.” The previously analyzed quadrats provided the basis for identifying the dominant benthic invertebrates across the region. Less-abundant benthic fauna were identified to the lowest possible taxonomic level and counted, with their time of appearance and disappearance noted. Anthropogenic disturbance and debris were also noted, as was kelp debris. The time of appearance and disappearance on the video was noted for fields of benthic megafauna to attempt to quantify a vector distance of the field; however, the variable vessel speed and occasionally turbid water prevented accurate estimates at each site.

Data analysis

Both drop camera (quadrat) and video transect observations contributed to the epibenthic fauna community and habitat analyses. Taxa richness estimates were calculated both from the quadrats and the video transect footage, whereas taxa diversity was calculated from quadrat observations only. The Shannon-Weaver diversity index (H’) was used as the diversity metric as it prioritizes the species richness component of the diversity equation, an advantage in cases where there is a small sample size, to reduce the influence of rare taxa observations. The index is defined by H’ = -∑ p_ilog(b)p_i, where p_i is the proportional abundance of species i and b is the base of the logarithm (Hill 1973). Taxa density was calculated for each unique taxon within each quadrat at each site. Density is presented in individuals-m² and reflects the number of each fauna divided by the total visible surface area (0.39 m² ± obscured grid cells or additional grid cells in the perspective grid) of each quadrat. Although species density was not calculated for the video transects because of our inability to standardize the spatial scale, relative density of extensive fauna aggregations (e.g., cerianthid fields) was estimated.

Multivariate analyses were conducted using PRIMER 7 to investigate species assemblage patterns within and between sites and with substrate complexity (Clarke and Gorley 2015). Details of the multivariate analyses are shown in full in Appendix 1 but are summarized here. First, a square root transformation was applied to the quadrat abundance data to reduce the influence of zeros and dominant species (Clarke et al. 2014). Next, a resemblance analysis was conducted on every pair of samples (quadrat) in the dataset using Bray-Curtis dissimilarity. Non-metric multi-dimensional scaling (n-MDS) plots were generated based on the resemblance matrix and were represented by site and primary substrate. From these plots, the dominant taxa were identified by overlaying taxa vectors on the n-MDS using a Pearson correlation threshold of r > 0.4 (Clarke and Gorley 2015).

Dominant taxa were then used to inform criteria to create biotopes, a fauna assemblage classification defined by the most dominant taxa in a sample (in this case, a quadrat). Biotopes were assigned to each quadrat based on the following criteria: (1) if the only taxon found in a quadrat was one of the dominant taxa, the biotope assigned for that quadrat reflected that dominant taxon; (2) if two or three dominant taxa were found in the same quadrat, biotopes included all assigned taxa in alphabetical order (e.g., biotope = cerianthids, Gersemia sp., ophiuroids); (3) if more than three dominant taxa were found in the same quadrat, a “general epifauna” biotope category was assigned; (4) if none of the dominant species were present in a quadrat, the “rare species” biotope category was assigned; (5) if no visible epifauna were present, the “no epifauna” biotope category was assigned.

A one-way permutational MANOVA (PERMANOVA) with 9999 permutations (Factor: biotope, levels: 24 biotopes defined) was conducted to assess the statistical significance of the defined biotopes (Anderson et al. 2008). Given the low number of samples in some pair-comparisons, which results in a low number of unique permutations (e.g., < 100), we used Monte Carlo p-values (Clarke and Gorley 2006). Further, a one-way PERMANOVA (Factor: Site; Levels: Hebron, Okak, and Nain) and Pair-wise tests were conducted to identify differences in the resemblance matrix between sites. Finally, species accumulation plots were generated by area, also based on 9999 permutations using PRIMER’s S obs curve (Clarke and Gorley 2006).

Key taxa

Each key taxa were selected using at least one of the following criteria: (1) identified as a dominant in the community analysis noted above; (2) identified as important by Labrador Inuit in formal consultations; (3) previously identified in the literature as potential indicators of vulnerable marine ecosystems (VMEs) and other major ecological functions; or (4) identified as a species of current or potential commercial importance (e.g., fisheries management documents exist for the region; see references in Table 2). Although there is some overlap with dominant taxa identified from the n-MDS correlation threshold analysis described above, the criteria for identifying key taxa were qualitative.

RESULTS

Megabenthic diversity patterns (drop camera)

The drop camera quadrat analysis revealed different fauna assemblage patterns and substrate associations between sites (Table 3, Fig. 3, Fig. 4). The species accumulation curves indicated that further sampling at all sites will likely yield new species records, as asymptotes were not reached. However, at the inner Nain site, where the number of samples was higher, the curve is closer to plateauing (Fig. 5). It also confirms that the species richness is higher in all Nain sites and Hebron-inner than the rest of the sites.

Substrate at the Hebron sites was dominantly mud, though in the inner (sill) fjord site (H2) substrate structure was more complex (more variation in grain size and substrate hardness) and variable, coincident with decreasing depth (Fig. 6, Fig. A2.2). Whereas taxa richness was the lowest of all sites at outer Hebron Fjord (H1), which was dominated by polychaete tubes (present in 100% of quadrats, 15–69 individuals-m²), the inner fjord site had higher taxa richness, as well as higher diversity and taxa densities (Table 3, Fig. 3). High densities of ophiuroids (present in 72% of quadrats, 3–151 individuals-m²) and cerianthids (present in 62% of quadrats, 3–62 individuals-m²) were also observed at these sites (Table 3, Fig. A2.1).

Despite the different depth profiles of the Okak outer north site (O1, deeper) and outer south site (O3, shallower), both were characterized by predominantly muddy substrate (Fig. A2.2) and a high density of ophiuroids—the highest density of any taxon observed on this survey (present in 100% of quadrats, 64–418 individuals-m²; Table 3, Fig. 4). Coincident to the dominance of ophiuroids, the fauna diversity at these sites was lower than that at any other sites on this survey, though fauna such as sea urchins and cerianthids were also observed in smaller numbers (present in 9% and 35% of quadrats, 3–8 and 3–15 individuals-m², respectively). The inner Okak Fjard site (O2) was characterized by higher taxa diversity, though slightly lower overall taxa richness, than the outer sites (Fig. 3). This was the only site in the survey where crinoids (sea feathers) were observed (present in 20% of quadrats, 3–6 individuals-m²; Fig. 4, Table 3, Fig. A2.1).

The inner and outer sites in the Nain archipelago differed in their respective fauna assemblage patterns and heterogeneity of substrates, but both were characterized by high taxa richness and diversity in comparison to sites at Hebron and Okak (Table 3, Fig. 3, Fig. A2.1, Fig. A2.2). At the outer site (N1), the soft substrate was dominated by ophiuroids (8% of quadrats, 5–31 individuals-m²), similar to observations in Hebron and Okak. However, on the harder substrates a wider array of taxa was observed, including sea urchins and hermit crabs (present in 40% and 6% of quadrats, 3–13 and 3–5 individuals-m², respectively). Barnacles were observed in 31% of quadrats in densities of 5–103 individuals-m². At the inner site (N2), encompassing the polynya, the highest diversity and richness of taxa were observed. The complex and diverse substrate supported a broad range of taxa including corals, sponges, ophiuroids, and urchins (Table 3, Fig. 4, Fig. 6). Barnacles were only observed in 11% of quadrats at this site, primarily in the polynya, but again in high densities (5–153 individuals-m²). This was the only site in the survey where scallops (present in 16% of quadrats, 3–10 individuals-m²) were observed, where they co-occurred with what likely represented dredge marks on the soft-bottomed seafloor.

The key taxa (Table 2) varied in their distribution among sites (Table 3, Fig. A2.1). Scallops (likely C. islandica), sea urchins, tunicates (likely Boltenia ovifera), and sea cucumbers were most abundant in the inner Nain site (N2, both within and outside the polynya), where they typically occurred on mixed, hard substrate (e.g., Fig. 4). Polychaetes were observed where mud was dominant, in Hebron and Okak sites only. Sponges, likely comprising different species, were observed both in the outer Hebron site on mud substrate and on hard substrate in both Nain archipelago sites. Gersemia sp. coral observations coincided with mixed substrate in the inner Hebron site (H2), in the deep outer Okak site (O1), and in highest densities in the inner Nain archipelago site (N2, present in 55% of quadrats). Gersemia sp. densities were higher in quadrats outside the polynya than inside (maximum densities of 37 vs. 13 individuals-m²; Table 3).

Multivariate analysis

The dominant taxa identified in the n-MDS analysis were: cerianthids, ophiuroids, Gersemia sp., sea urchins, barnacles, and polychaete tubes (Fig. 7). The initial multivariate analysis led to the identification of 24 preliminary biotopes, most (11 of 24) of them ophiuroid-based. However, Pair-Wise PERMANOVA indicated no significant differences between a number of these (P(perm) > 0.05), which were subsequently grouped. The final number of biotopes is 16 (Table 4). The epibenthic community structure differed significantly between sites (PERMANOVA, Pseudo-F_{7, 367} = 30.5, P (perm) < 0.001).

Quadrats from the outer site in Hebron (H1) were mostly represented by the general epifauna and ophiuroid-based biotopes. Quadrats at the inner Hebron site (H2) were mostly cerianthid- and ophiuroid-based biotopes. At both sites the dominant substrate was mud (Fig. 7, Fig. 8).

Whereas the primary substrate in most quadrats from all Okak sites was mud (Fig. A2.2), the dominant biotopes were different between outer and inner sites. Both outer sites at Okak (O1 outer-north, O3 outer-south) were dominated by ophiuroid-based biotopes despite the difference in average depth between the two, while the inner site (O2) was dominated by a mix of ophiuroid- and cerianthid-based biotopes (Fig. 7, Fig. 8).

In the Nain archipelago, the outer site (N1) was dominated by the sea urchin biotope, while at the inner location (N2) quadrats were more commonly dominated by the general epifauna and ophiuroid-based biotopes (Fig. 7). The “rare” biotope dominated a subset of quadrats in both the outer and inner site in the Nain archipelago suggesting a large variety of species in the area. Although some taxa, like scallops and barnacles, were observed in higher densities within the polynya portion of the inner Nain site, overall taxa richness and dominant biotopes were not significantly different than what was observed at other transects at this site (Table 3). Substrate across both sites in Nain was highly variable and included mud, sand, pebbles, cobbles and boulder combinations (Figs. 6, 7, 8).

Across all sites, epibenthic taxa richness was associated with the complexity of the inorganic benthic substrate (Fig. 8). Organic (epiphytic) materials were not included in substrate analyses as the majority were unattached detritus. Species richness tended to be greater on samples with higher substrate complexity (i.e., pebbles and cobbles) at sites not dominated by mud or sand. Despite the lower taxa richness in the inner, less exposed, soft-substrate sites of the fjord and fjard, these sites had higher taxa evenness and therefore greater diversity compared to the outer sites (Fig. 3), which were dominated by ophiuroid biotopes (Fig. 8).

Video transects

Qualitative observations from the video data obtained between drops indicated similar taxa assemblages when compared to the drop camera quadrat observations (Table A2.1). However, the video footage provided a wider field of view, allowing the identification of fauna at a larger scale. For instance, dense and extensive fields of ophiuroids were observed at both the outer exposed sites in Okak (O1 outer-north, O3 outer-south), with > 100 individuals visible in the field of view at times. This density was consistent with what was captured in the drop camera quadrats but additionally revealed the spatial extent of these ophiuroid fields. Cerianthid fields were also observed at the inner fjord and fjard sites, with the densest fields (100 individuals/field of view) at the inner site of Hebron (H2), and up to 50 individuals per field of view in a field estimated to span hundreds of meters at the inner fjard site in Okak (O2). Cerianthid fields were also observed at the shallower outer fjard site in Okak (O3), with up to 50 individuals in the field of view. At this site there were also fields of sea urchins, with 5–13 urchins per field of view. Sea urchin fields were not observed at other sites. Despite the low density of crinoids observed in quadrats at the inner Okak fjard site (O2), the video transect footage captured fields of crinoids with as many as 50 individuals in the field of view, where the fields extended beyond the view of the camera. Similar to the results of the drop camera analysis, this was the only site where crinoid fields were observed. Rhodolith beds were also observed on video transects. Though the spatial extent or density of these were not quantified, they are three-dimensional habitat-forming structures and warrant further investigation.

More diverse and abundant fish fauna was observed from the video transect footage than the drop camera quadrats, highlighting the importance of capturing the larger spatial scale in this survey. In the Hebron sites, anguilliforms (eel-like) (2) and unidentified benthic fish (15) were observed, including some within cerianthid fields in the inner fjord (H2). Ten fish were observed on the video transects at Okak sites, primarily in the shallower outer fjard site (O3). Two of these were anguilliforms, and the remainder could not be identified further. The majority of fish observations on the transects were observed at the sites in the Nain archipelago: 25% of all fish observations from the survey were in the outer archipelago (N1) while 50% were from the inner site that included the polynya (N2; Table A2.1).

Baited remote underwater video system (BRUVS) surveys

Fish (capelin, Mallotus villosus, and gadids) and toad crabs (Hyas sp.) were the most common mobile fauna observed in the baited camera video footage (Table A2.2), though toad crabs and amphipods were the only fauna that were observed to feed on the bait. The deeper outer fjard site at Okak (O1) was the site where the greatest number and richness of fish were observed from the BRUVS. Capelin were common at Okak sites, primarily at the deeper outer fjard site (O1). The deployments in the Nain archipelago also led to the observation of at least five fish taxa, including nine skates (Rajidae) in the site with the polynya (N2) and five sculpins (Cottidae) in the outer site (N1).

DISCUSSION

The patterns of benthic biodiversity and habitat structure within major geomorphology features observed in this study, in areas of high cultural significance, help fill gaps in knowledge identified as important by Labrador Inuit and the Nunatsiavut Government. Understanding patterns in faunal densities and their relationship to habitat structure contributes to generating and interpreting habitat maps, managing resources and making decisions about protected areas.

Relationships between epibenthic megafauna, substrate, and sites

Benthic megafauna assemblages and biotopes differed significantly among sites. Deep benthic habitats in the fjord, fjard and archipelago were dominated by mud, with high megafauna densities but lower richness than the shallower sites with complex, harder substrate. The shallowest sites, located inside and outside of the polynya in the Nain archipelago, were the most diverse in rocky and biological substrate and hosted the largest taxa diversity. The fauna community biotopes at the Nain archipelago sites were primarily “rare” (no dominant taxa) and “general epifauna,” consisting of more dominant taxa. Throughout this region, higher biogenic habitat complexity and exposure supported more unique taxa, comparable to findings in other studies in the Arctic (e.g., Dale et al. 1989, Włodarska-Kowalczuk et al. 2012, Davies et al. 2015).

Substrate type and complexity can be considered a proxy for bottom hydrography and currents, with coarser and harder substrates indicative of stronger bottom current regimes (Snelgrove and Butman 1994). Though we cannot separate grain size from other ecosystem drivers in this survey, it is reasonable to expect that fauna assemblage patterns are related to substrate complexity and bottom currents (e.g., Fuller et al. 2008, Davies et al. 2015). This pattern was strong, despite a sampling bias that underrepresented boulder substrate. Shallower, hard substrate sites do exist in both Hebron and Okak (Carpenter et al. 2020) but we could not access them. Visiting these areas in future surveys would be useful to investigate whether the patterns observed in the Nain archipelago extend to other regions in Nunatsiavut and to confirm the existence of other “hotspots” having a high diversity of benthic species.

Taxa such as polychaetes associated with nutrient and carbon cycling (Shull 2008) were primarily abundant in deep sites with mud substrate and were the dominant taxa in the deepest fjord quadrats. Taxa associated with functions such as stabilizing sediment and providing structure (increasing heterogeneity) in the benthic environment included ophiuroids, crinoids, cerianthids, sponges, and Gersemia sp. (Auster et al. 2003, Geraldi et al. 2017, Fuller et al. 2008). These taxa exhibited varied distribution and density across the region. Ophiuroids and cerianthids were widely distributed and abundant, especially in deep, mud-dominated sites in fjords and fjards, with ophiuroids observed ubiquitously. This pattern corresponds to observations of ophiuroid dominance in shelf and fjord habitats across the Arctic (Dale et al. 1989, Roy et al. 2014). Sponges, soft corals (Gersemia sp.) and tunicates (Boltenia sp.) were most abundant in the polynya and on other hard substrate combinations, indicative of transport and availability of suspended food particles in these areas (LaBarbera 1984, Roy et al. 2014). Similarly, taxa that are locally important for food and commercial harvesting, including scallops, sea urchins, and holothurians (sea cucumber), were most abundant on heterogeneous rock-dominated substrates, especially in the polynya.

Scallops (C. islandica) were only observed in the inner Nain site. Interestingly, at this site there were no cerianthids observed although small ones may have gone undetected. However, large-sized cerianthids in high densities like those reported at the other sites were not seen. Cerianthids are important predators of scallop larvae, controlling spatial distribution and patch size of scallop beds in the western Gulf of Maine (Langton and Robinson 1990). Although other drivers cannot be excluded, the prevalence of scallops in this site could be related to the lack of cerianthid predation. The trophic and habitat roles of key taxa found in high abundances, such as cerianthids, ophiuroids, and soft corals, warrants further investigation on their role in structuring the benthic community.

Almost half of all fish observed in video transect footage were in the polynya. High productivity and habitat complexity in this site may attract fish. Capelin, sand lance, and hyperiid amphipods dominate the diets of Arctic char in the Nain region (Dempson et al. 2002). In the deeper, mud-dominated sites, fish were also observed in cerianthid fields, illustrating the potential benefit provided by three-dimensional structures in these areas with otherwise homogeneous substrate. The video transect observations of fish are useful to compare with results from the baited camera findings. Capelin and amphipods were observed in the baited camera images in the outer Okak site, but these mobile species were more difficult to spot in the video transects.

Our results support the characterization that productivity may be enhanced in polynyas because of the seasonal jumpstart in solar radiation and consequent vertical carbon flux resulting from the lack of, or dynamic, ice cover in the winter and spring (Grebmeier and Barry 2007). Although we did not quantify water column or benthic productivity during our survey, the higher benthic diversity and abundance of larger, mobile fauna (fish, crabs) at the Nain archipelago sites indicate a comparatively rich and productive community. For example, high densities of holothurians, only observed at the Nain sites and more dominantly in the vicinity of the polynya, have been associated with pulses of phytodetritus (Gooday 2002, Bluhm et al. 2009, Boetius et al. 2013). Our observations align with Inuit knowledge that this and other polynyas in the region support higher pelagic productivity that support preferential harvesting areas (Brice-Bennett 1977, Pikialasorsuaq Commission 2017, QIA 2018).

VME indicators

Vulnerable marine ecosystems (VMEs) are areas of high biodiversity: “hotspots” that are characterized by diverse benthic assemblages and contain fauna that are physically fragile, sensitive, and slow to recover from damage. VMEs can be distinguished from surrounding habitats by the presence of structure-forming taxa, which elevates the otherwise homogenous seafloor into more diverse habitat suitable for colonization by other benthic epifauna (Fuller et al. 2008, FAO 2009, Buhl-Mortensen et al. 2010, Auster et al. 2011, Beazley et al. 2013, Ashford et al. 2019, Blicher and Hammeken Arboe 2021).

Taxa observed during this survey that are considered VME indicators, included cerianthids, crinoids, tunicates, corals, and sponges. These taxa were seen in all sites, although patterns of assemblages differed among sites and might not necessarily characterize VMEs. For instance, tunicates and sponges were not observed forming fields, and therefore their presence alone may not indicate a VME. Nevertheless, dense cerianthid fields, such as those observed on video footage in the inner fjord and fjard sites, are recognized as being a key component and indicator of VMEs in the northwest Atlantic (Fuller et al. 2008). Cerianthid fields have been reported to be used by redfish (Sebastes sp.) in the Gulf of Maine (Auster et al. 2003). We identified a maximum of 20 cerianthids per quadrat. Based on our estimated quadrat area of 0.39 m², this could represent a maximum density of 53 individuals-m². Auster et al. (2003) reported cerianthid densities of up to > 50 individuals-m², which is comparable to our results, though caution should be exercised when extrapolating from patchily distributed species. Although density thresholds defining cerianthid fields have not been published, our findings highlight important benthic hotspots and potential VMEs in the study sites, which warrants further investigation. Like findings in the eastern Atlantic fjords, cerianthids in this site were associated with sea cucumber, pandalid shrimp species, and sponges (Buhl-Mortensen and Buhl-Mortensen 2014).

Soft corals reported in this study are known to provide habitat to juvenile basket stars (Gorgonocephalus sp.; Neves et al. 2020). In fact, juvenile basket stars were observed attached to soft coral colonies at several instances in the Nain archipelago, and the single observation of an errant basket star in this study was also reported there. Neves et al. (2020) reported that among soft corals in the family Nephtheidae, Gersemia sp. was the taxon with the lowest co-occurrence with juvenile basket stars. However, our in situ observations in Nain reinforce that co-occurrence rates might change spatially and that at this site Gersemia sp. might provide habitat to juvenile basket stars at potentially higher occurrence rates than those described by Neves et al. (2020) based on physical specimens. Nephtheidae soft coral gardens have also been suggested for consideration as VME indicators (Long et al. 2020). These authors suggested that a density of 1 soft coral-m² would characterize a soft coral garden. Where they occurred in our study, soft corals were common at densities of 5–14 colonies-m² and reached a maximum observed density of 33 colonies-m², greatly exceeding the minimum coral garden threshold proposed by Long et al. (2020).

High abundances of species such as ophiuroids and polychaete worms, such as those observed in the fjord and fjard sites, are important to benthic-pelagic energy cycling and soft substrate stabilization (Grebmeier and Cooper 1995, Cooper et al. 2002, Grebmeier and Barry 2007). Although in some areas these taxa co-occurred, transect footage revealed large stretches of substrate solely dominated by ophiuroids, particularly in the outer Okak fjard sites, corroborating the low diversity in ophiuroid-dominated quadrat samples there. Comparable ophiuroid-dominated fields in the soft bottoms of submarine canyons outside the Nain archipelago have been recently identified during a drop camera survey in the area (D. Coté, personal communication). The dominance of only a few structure-forming and energy-cycling low-trophic taxa in sites like the outer fjord and fjard indicate low functional diversity, not uncommon in Arctic food webs, and therefore greater vulnerability to food web disruption (Cadotte et al. 2011, Kędra et al. 2015). In laboratory studies, ophiuroids exhibited energy deficits with increased water temperature and decreased pH (Wood et al. 2011). Given the presumed low functional diversity observed in some sites where ophiuroids are dominant, it is not unreasonable to propose that changes in climate could have cascading implications for the sediment-stabilizing and energy-cycling roles ophiuroids fill in the benthic food webs here. More research of this kind in Nunatsiavut would provide further insight into broad-scale functional diversity patterns.

Changes in climate are already being observed in this region, and the impacts will continue at various scales (Fox 2002, Furgal et al. 2002, Allard and Lemay 2012, Cunsolo Wilcox et al. 2012, DFO 2021, McCarney et al. in press). The reductions in the temporal and spatial extent of annual sea ice cover in the Arctic are expected to contribute to warming water, lower pH, increased stratification, and altered primary production (Harada 2016). Overall, change in the timing, composition, and magnitude of spring blooms could have cascading impacts throughout the food web in this northern region (Mäkelä et al. 2017a,b). Indeed, environmental shifts have already affected the range, habitat use, diet, growth, and effective population size of valued coastal fish like Arctic char (Michaud et al. 2010, Coté et al. 2021, Layton et al. 2021). Given the important connections between Nunatsiavut residents and the ecosystem in which they reside, climate change may create uncertainty in accessing marine resources by making it difficult and sometimes impossible to trust traditional knowledge for sustenance, such as information about ice and travel routes (Allard and Lemay 2012, IPCC 2013, DFO 2021, McCarney et al. in press). Studies such as this one can help resource users mitigate the impacts of a changing environment.

CONCLUSION

The patterns of benthic biodiversity and habitat structure within major geomorphology features observed in this study, in areas of high cultural and social significance, contribute to filling information gaps identified by Labrador Inuit and the Nunatsiavut Government. The spatial extent of vulnerable marine ecosystem components and the high densities of dominant taxa, notably cerianthids, ophiuroids, Gersemia, and polychaetes, were important findings, even while the species accumulation curves indicated new species records are likely to be discovered. These dominant taxa are among those identified as important for seafloor structure and ecosystem functions such as energy cycling, especially in the deeper areas dominated by soft sediment. The high benthic diversity and presence of fish fauna in the shallow polynya-dominated archipelago was suggestive of a more direct linkage to higher trophic levels of greatest importance to Labrador Inuit. These findings attest to the importance and accuracy of Inuit knowledge that guided the research at these sites and the interpretation of the observed patterns of species and habitat distributions. Understanding these patterns from the combined perspectives of Inuit and Western science in Nunatsiavut marine waters will guide resource management and protected area decisions, including those in the Nunatsiavut Government’s Imappivut Marine Planning Initiative, at a time when there is growing concern about future access to resources because of climate change.

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