Arctic crustose coralline alga resilient to recent environmental change

Abstract

Rising atmospheric carbon dioxide is warming Arctic seawater at a rate twice the global average due to multiple positive feedbacks. Thus, warming is disproportionately influencing data‐poor Arctic marine ecosystems. Subarctic flora are an important component of these ecosystems, along with the less biodiverse flora endemic to the Arctic. Warming will likely lead to an increasing dominance of subarctic flora that will be initially successful due to a shorter sea ice period. Benthic crustose coralline algae presently flourishes in subarctic regions where they are key substrate builders that influence community structure through provision of habitat for a variety of benthic organisms. Here we evaluate changes in the skeletal resilience of long‐lived subarctic crustose coralline alga Clathromorphum compactum to variability in seawater temperature and sea ice (the later which influences salinity and solar irradiance reaching the seafloor) across latitudes in the northwest Atlantic and Arctic Oceans. We demonstrate that average growth and calcification rate significantly decreases in C. compactum toward higher latitudes due to colder temperatures and more fresh waters. Skeletal density also declines toward higher latitudes but displays specimen‐specific variability. However, through a common growth period (1984–2001), density increased at all locations which we interpret to be a response to warmer and more well‐lit benthic environments. At the most northerly site, growth and calcification also increased with density, suggesting warming and declining Arctic sea ice in the spring may benefit this species at its upper latitudinal limits. As a result, continued warming may enhance the presence of C. compactum in Arctic regions.

Cessation of Hardground Accretion by the Cold‐Water Coralline Algae Clathromorphum Compactum and Clathromorphum Nereostratum Predicted Within Two Centuries

“…compactum increase with increasing T. Although the present laboratory‐based study was conducted over shorter timescales, the results are consistent with those of Williams, Chan, Halfar, et al. (2021) across the T range that the wild samples in Williams, Chan, Halfar, et al. (2021) were evaluated (−1 to −7°C).…”

“…Williams, Chan, Halfar, et al. (2021) found that, over multidecadal timescales, extension rates of C . compactum increase with increasing T. Although the present laboratory‐based study was conducted over shorter timescales, the results are consistent with those of Williams, Chan, Halfar, et al.…”

Ocean Acidification Reduces Skeletal Density of Hardground‐Forming High‐Latitude Crustose Coralline Algae

“…However, the general north‐south orientation of the continental shelf of the northeastern United States and southeastern Canada may permit northward retreat of C. compactum into colder waters along the Canadian continental shelf as temperatures warm. Analysis of historical skeletal growth, density, and calcification in wild collected C. compactum suggests that this species has been benefiting from a longer summer season and associated earlier spring sea ice breakup in the high Arctic (Williams et al., 2021). In contrast, the generally east‐west orientation of the Aleutian archipelago that supports large populations of C. nereostratum preclude such a northerly retreat into colder waters.…”

Element cycling and aquatic function in a changing Arctic

“…Clearly, the biological and biogeochemical function of shallow water settings in the future will depend on the extent to which environmental changes favor pelagic or benthic primary production. Ongoing hydrological, physical, and biogeochemical changes appear to stimulate the northward migration and areal expansion of seagrass and macroalgae (Kortsch et al 2012; Krause‐Jensen et al 2020) and the growth of resilient crustose corallines (fundamental ecosystem engineers in deeper waters) (Williams et al 2021). Thus, predictions for the future Arctic need to better address the importance of benthic primary producers and the energy they provide for coastal food webs and constrain the regional variability in their response to ongoing environmental changes.…”