Critical indirect effects of climate change on sub-Antarctic ecosystem functioning

Area of Science:

• Marine ecology
• Climate change impacts
• Southern Ocean ecosystems

Background:

• Sub-Antarctic islands are vital breeding grounds for top predators in Southern Ocean food webs.
• Energetic demands of reproduction and molting are met by both inshore and offshore productivity.
• Oceanographic conditions influence these productivity pathways, affecting island ecosystems.

Purpose of the Study:

• To investigate the consequences of climate-driven environmental changes on the Prince Edward Islands' marine ecosystem.
• To understand how shifts in oceanography affect the balance of inshore and offshore productivity.
• To assess the cascading effects on top predator populations.

Main Methods:

• Analysis of long-term carbon isotope signatures in benthic organisms.
• Monitoring of population trends in inshore- and offshore-feeding top predators.
• Correlation of ecological changes with oceanographic shifts, specifically the Sub-Antarctic Front position.

Main Results:

• A measurable long-term shift in carbon isotope signatures indicates a decline in enhanced phytoplankton productivity.
• Regional climate change has altered the balance between allochthonous and autochthonous productivity.
• Inshore-feeding predators show population declines, while offshore-feeding predators remain stable or increase, suggesting altered prey availability.

Conclusions:

• Climate change indirectly affects marine ecosystems by altering trophic pathways.
• Shifts in the balance between offshore and inshore productivity have significant consequences for top predator populations.
• The Prince Edward Islands ecosystem demonstrates how climate change impacts can cascade through the food web.