Kelp in the Eastern Canadian Arctic: Current and Future Predictions of Habitat Suitability and Cover

Abstract

Climate change is transforming marine ecosystems through the expansion and contraction of species’ ranges. Sea ice loss and warming temperatures are expected to expand habitat availability for macroalgae along long stretches of Arctic coastlines. To better understand the current distribution of kelp forests in the Eastern Canadian Arctic, kelps were sampled along the coasts for species identifications and percent cover. The sampling effort was supplemented with occurrence records from global biodiversity databases, searches in the literature, and museum records. Environmental information and occurrence records were used to develop ensemble models for predicting habitat suitability and a Random Forest model to predict kelp cover for the dominant kelp species in the region – Agarum clathratum, Alaria esculenta, and Laminariaceae species (Laminaria solidungula and Saccharina latissima). Ice thickness, sea temperature and salinity explained the highest percentage of kelp distribution. Both modeling approaches showed that the current extent of arctic kelps is potentially much greater than the available records suggest. These modeling approaches were projected into the future using predicted environmental data for 2050 and 2100 based on the most extreme emission scenario (RCP 8.5). The models agreed that predicted distribution of kelp in the Eastern Canadian Arctic is likely to expand to more northern locations under future emissions scenarios, with the exception of the endemic arctic kelp L. solidungula, which is more likely to lose a significant proportion of suitable habitat. However, there were differences among species regarding predicted cover for both current and future projections. Notwithstanding model-specific variation, it is evident that kelps are widespread throughout the area and likely contribute significantly to the functioning of current Arctic ecosystems. Our results emphasize the importance of kelp in Arctic ecosystems and the underestimation of their potential distribution there.

Arctic marine forest distribution models showcase potentially severe habitat losses for cryophilic species under climate change

“…solidungula (Table 1), the latter of which is known to complete much of its annual growth under sea‐ice (Chapman & Lindley, 1981; Dunton & Schell, 1986). The importance of sea‐ice in modelling Arctic kelp distributions is also reported by Goldsmit et al (2021). It can be expected, however, that contemporary marine forests at the highest latitudes are extremely patchy, persisting only where the ebb and flow of sea ice dynamics facilitate a brief growing season, and frequently occurring at low per area biomasses, depth ranges, and cover compared to marine forests at lower latitudes (Filbee‐Dexter et al, In press; Krause‐Jensen et al, 2012).…”

“…Indeed, of the environmental variables used to train our models, the presence of sea-ice best predicted the presence of cryophilic species D. socialis and L. solidungula (Table 1), the latter of which is known to complete much of its annual growth under sea-ice (Chapman & Lindley, 1981;Dunton & Schell, 1986). The importance of sea-ice in modelling Arctic kelp distributions is also reported by Goldsmit et al, 2021;Jueterbock et al, 2013Jueterbock et al, , 2016, and similar trends of northward shifts reported in temperate North Atlantic taxa (Westmeijer et al, 2019)…”

“…The importance of sea-ice in modelling Arctic kelp distributions is also reported by Goldsmit et al (2021). It can be expected, however, that contem- Goldsmit et al, 2021;Jueterbock et al, 2013Jueterbock et al, , 2016, and similar trends of northward shifts reported in temperate North Atlantic taxa (Westmeijer et al, 2019)…”

“…Medium confidence (IPCC+confidence scale of 5–8 in 10 chance of being correct) was placed on the projection that macrophytes are expanding in the Arctic, but this included within range increases in abundance as well as total gains in habitat area. Ecological niche modelling also supports this trend of expansion continuing into the future depending on the severity of climate change, with substantial gains in the Arctic projected for many canopy‐forming brown seaweeds (Assis et al, 2018; Goldsmit et al, 2021; Jueterbock et al, 2013, 2016), and similar trends of northward shifts reported in temperate North Atlantic taxa (Westmeijer et al, 2019). Modelling work, however, has focused largely on cold‐temperate taxa that extend into the Arctic basin (e.g.…”

“…Finally, mean salinity was selected, as this variable also occasionally explains a high percentage of seaweed distributions. Goldsmit et al (2021), for instance, showed that ice thickness, temperature and salinity were the most important variables explaining kelp distributions in the Eastern Canadian Arctic. We reduced this layer selection further to remove layers with multicollinearity issues (selecting between the mean, long‐term maximum and long‐term minimum measures) using variance inflation factor (VIF) tests.…”