Coupled changes between the H‐Print biomarker and δ15N indicates a variable sea ice carbon contribution to the diet of Cumberland Sound beluga whales

Sub-Arctic habitats are being exposed to increasingly long periods of open water as sea ice continues to decline in thickness and extent. Some hypothesize that this will result in a reduction, and maybe total loss of sea ice derived (sympagic) carbon supply; however, the impact of such change on ecosystems requires further investigation. Here, we used the H-Print biomarker approach that utilizes well-defined indicators of both sympagic and phytoplanktic carbon, in combination with stable isotopes (delta N-15), to study the effect of reducing sympagic carbon availability on beluga whales (Delphinapterus leucas) in the sub-Arctic ecosystem of Cumberland Sound. Our data show that decreasing delta N-15 in belugas was negatively correlated with pelagic carbon (H-Print) within their diet. We also identified a statistically significant (R-2 = 0.82; p <= 0.01) change point in the proportion of sympagic/pelagic carbon within beluga around the year 2000, signified by consistently reducing delta N-15, coupled with increasing pelagic carbon composition. This observed shift from sympagic to pelagic contribution to diet is likely to remain a feature of the Cumberland Sound ecosystem during the projected reduction of sea ice.