Shallow subtidal marine benthic communities of Nachvak Fjord, Nunatsiavut, Labrador: A glimpse into species composition and drivers of their distribution.

Marine fjords along the northern Labrador coast of Arctic Canada are influenced by freshwater, nutrients, and sediment inputs from ice fields and rivers. These ecosystems, further shaped by both Atlantic and Arctic water masses, are important habitats for fishes, marine mammals, seabirds, and marine invertebrates and are vital to the Labrador Inuit who have long depended on these areas for sustenance. Despite their ecological and socio-cultural importance, these marine ecosystems remain largely understudied. Here we conducted the first quantitative underwater scuba surveys, down to 12 m, of the nearshore marine ecology of Nachvak Fjord, which is surrounded by Torngat Mountains National Park located in Nunatsiavut, the Indigenous lands claim region of northeastern Canada. Our goal was to provide the Nunatsiavut Government with a baseline of the composition and environmental influences on the subtidal community in this isolated region as they work towards the creation of an Indigenous-led National Marine Conservation Area that includes Nachvak Fjord. We identified four major benthic habitat types: (1) boulders (2) rocks with sediment, (3) sediment with rocks, and (4) unconsolidated sediments, including sand, gravel, and cobble. Biogenic cover (e.g., kelp, coralline algae, and sediment) explained much of the variability in megabenthic invertebrate community structure. The kelp species Alaria esculenta, Saccharina latissima, and Laminaria solidungula dominated the boulder habitat outside of the fjord covering 35%, 13%, and 11% of the sea floor, respectively. In contrast, the middle and inner portions of the fjord were devoid of kelp and dominated by encrusting coralline algae. More diverse megabenthic invertebrate assemblages were detected within the fjord compared to the periphery. Fish assemblages were depauperate overall with the shorthorn sculpin, Myoxocephalus scorpius, and the Greenland cod, Gadus ogac, dominating total fish biomass contributing 64% and 30%, respectively. Understanding the composition and environmental influences within this fjord ecosystem not only contributes towards the protection of this ecological and culturally important region but serves as a baseline in a rapidly changing climatic region

Dominant algal taxa and benthic cover by major habitat type in Nachvak Fjord.

Avg. (± sd) is average percent cover and one standard deviation. Percent contributions to average similarities within groups based on Bray-Curtis similarity matrices. % contrib. = percent contribution, % cum. contrib. = percent cumulative contribution.</p

Table 12 -

(a) Results of redundancy analysis (RDA) on ln(x+1)‐transformed fish taxa abundance (num. m-2) by transect. (b) Conditional effects of Monte‐Carlo permutation results on the RDA.</p

Sampling locations in Nachvak Fjord, Nunatsiavut, Northern Labrador.

Basemap derived from GEBCO Compilation Group (2020) GEBCO 2020 Grid (doi:10.5285/a29c5465-b138-234de053-6c86abc040b9). Processing and assembly of the Global Self-consistent, Hierarchical, High-resolution Geography Database for shoreline data from [32].</p

Triplot of results of redundancy analysis on benthic taxa abundance by transect with biotic and abiotic variables (PC1, PC2, depth, salinity, water temperature, habitat type, distance to mouth of fjord).

Predictor variables were centered and standardized and megabenthic invertebrate taxa abundance was centered and log(x+1)-transformed for analysis.</p

Numerical abundance (number m-2) of megainvertebrates among habitats.

Values are means with one standard deviation in parentheses. BOU = boulders, RwS = rocks with sediment, SwR = sediment with rocks, and UNC = unconsolidated, which included sand, gravel, or cobble. (PDF)</p

Benthic cover correlations (Spearman’s rank-order correlations) from principal coordinates analysis.

Benthic cover correlations (Spearman’s rank-order correlations) from principal coordinates analysis.</p

Fish species observed in Nachvak Fjord.

num. m-2 = number of individuals per m-2, g m-2 = grams per m-2, Freq % = percent frequency of occurrence. Reported sizes (cm) are means, with minimum and maximum sizes in parentheses.</p

Metadata of survey sites sampled in Nachvak Fjord.

Habitats: BOU = boulders, RwS = rocks with sediment, SwR = sediment with rocks, and UNC = unconsolidated, which included sand, gravel, or cobble. Temp. = temperature (C°), Sal. = salinity (ppt). See Fig 1 for Station ID locations.</p