Published Date2019-12-17
JournalGeology, 2019-12-17 Find other publications in this journal
Author Info
  • Department of Earth Science, University of Bergen, and Bjerknes Centre for Climate Research, Jahnebakken 5, Bergen 5007, Norway
  • Department of Chemical and Physical Sciences, University of Toronto, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada
  • Department of Botany, Smithsonian National Museum of Natural History, 1000 Constitution Avenue NW, Washington, D.C. 20560, USA
  • Lebcon Environmental Services, 3043 Naranja Drive, Walnut Creek, California 94598, USA
  • Darling Marine Center, University of Maine, 193 Clarks Cove Road, Walpole, Maine 04573, USA
  • Robarts Research Institute, Schulich School Of Medicine, Western University, 100 Perth Drive, London, Ontario N6A 5K8, Canada


Warming surface ocean temperatures combined with the continued diffusion of atmospheric CO2 into seawater have been shown to have detrimental impacts on calcareous marine organisms in tropical and temperate localities. However, greater oceanic CO2 uptake in higher latitudes may present a higher oceanic acidification risk to carbonate organisms residing in Arctic and subarctic habitats. This is especially true for crustose coralline algae that build their skeletons using high-Mg calcite, which is among the least stable and most soluble of the carbonate minerals. Here we present a century-long annually resolved growth, density, and calcification rate record from the crustose coralline alga Clathromorphum nereostratum, a dominant calcifier in Pacific Arctic and subarctic benthic communities. Specimens were collected from the Aleutian Islands, Alaska (USA), a region that has undergone a long-term decline of 0.08 ± 0.01 pH units since the late 19th century. Growth and calcification rates remain relatively stable throughout the record, but skeletal densities have declined substantially since A.D. 1983. Strong correlations to warming sea-surface temperatures indicate that temperature stress may play a significant role in influencing the ability of corallines to calcify. Decreasing algal skeletal density may offset the benefits of continued growth and calcification due to a weakening in structural integrity, which could have detrimental consequences for the diverse reef-like communities associated with algal structures in mid-to-high latitudes.