Long-term, high-resolution measurements of environmental variability are sparse in the High Arctic. In the absence of such data, we turn to proxies recorded in the layered skeletons of the long-lived crustose coralline algae Clathromorphum compactum. Annual growth banding in this alga is dependent on several factors that include temperature, light availability, nutrients, salinity, and calcium carbonate saturation state. It ha...

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 initia...

Reef corals calcify faster in the presence of non‐calcareous algae. Ratios of calcification to photosynthesis appear to be affected by the ratio of alkalinity to acidity, which controls how efficiently the protons from calcification convert bicarbonate to carbon dioxide. By forcing calcifiers to calcify faster, algal proliferation on nutrient‐enriched reefs may adversely affect the reef‐builders.