A temporal shift in trophic diversity among a predator assemblage in a warming Arctic

Area of Science:

• Marine ecology
• Climate change biology
• Arctic ecosystem dynamics

Background:

• Climate change drives species range shifts, impacting species interactions at lower trophic levels.
• The effects of these shifts on high trophic-level predator assemblages are less understood.
• Arctic marine ecosystems are particularly vulnerable to warming, with observed changes in sea temperature and ice extent.

Purpose of the Study:

• To examine the trophic structure of a near-apex predator assemblage in Cumberland Sound, Nunavut, over a 22-year period.
• To assess how changes in prey availability, specifically capelin, influenced predator diets and trophic roles.
• To investigate long-term ecological changes in the Arctic food web due to climate change.

Main Methods:

• Utilized stable isotope analysis (δ13C and δ15N) within a Bayesian framework.
• Assessed shifts in diet, niche size, and community-wide metrics for key predators: beluga whales, ringed seals, Greenland halibut, and Arctic char.
• Compared trophic structure before (1990-2002) and after (2005-2012) an increase in capelin availability.

Main Results:

• All predator species increased their consumption of forage fish after 2005, indicating dietary flexibility.
• A temporal shift occurred from a trophically diverse to a trophically redundant predator assemblage.
• Predators increasingly utilized the pelagic energy pathway, playing more similar trophic roles.

Conclusions:

• High trophic-level predator assemblages in the Arctic food web are undergoing significant trophic shifts.
• Dietary flexibility allows predators to adapt to changing abiotic and biotic conditions driven by climate change.
• The observed changes signify a restructuring of the Arctic food web with potential cascading effects.