Ecosystem response persists after a prolonged marine heatwave

Area of Science:

• Marine Ecology
• Climate Change Impacts
• Ecosystem Monitoring

Background:

• Long-term marine ecosystem monitoring programs in the Gulf of Alaska were established after the Exxon Valdez oil spill.
• These programs provide a unique, decades-long dataset to assess ecosystem health and recovery.
• The Gulf of Alaska experienced a significant marine heatwave (PMH) from 2014-2016, with lingering warm conditions.

Purpose of the Study:

• To assess the Gulf of Alaska ecosystem's response to the 2014-2016 northeast Pacific marine heatwave (PMH).
• To analyze changes across multiple trophic levels and ecosystem domains.
• To evaluate the persistence of heatwave impacts on marine communities.

Main Methods:

• Analysis of 187 time series data, spanning primary production to commercial fisheries.
• Inclusion of data from nearshore intertidal to offshore oceanic environments.
• Comparison of ecosystem metrics before, during, and after the marine heatwave event.

Main Results:

• Abrupt ecosystem-wide changes were observed across all trophic levels following the PMH onset.
• Many of these ecosystem responses persisted for at least five years post-heatwave.
• Novel community-level groupings emerged, distinct from the decade preceding the heatwave.

Conclusions:

• The Gulf of Alaska ecosystem exhibited significant and lasting alterations due to the marine heatwave.
• Increased frequency of marine heatwaves under climate change poses a threat to ecosystem resilience.
• The return of the Gulf of Alaska ecosystem to its pre-heatwave state is uncertain.