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July 3, 2024

Heatwaves are in the news a lot lately and their impacts have been felt by people across the world. Extreme heat is also impacting wildlife and marine ecosystems in recent years. These heatwaves are increasing in frequency and magnitude worldwide.

Marine Heatwaves: A Global Issue

Scientists familiar with marine ecosystems across the globe teamed up on a recent special summary of the impacts caused by extreme heatwaves.  The special volume, called “How do marine heatwaves impact seabirds?” includes papers that followed from a symposium led by USGS research scientists Drs. John Piatt and Mayumi Arimitsu, along with an international team of seabird and forage fish experts, at the 3rd World Seabird Conference in October 2021. 

This theme section includes 13 contributed articles detailing studies that involved one or more marine heatwave events that spanned spatial scales from individual seabird colonies to large marine ecosystems, in subtropical, temperate, and polar oceans, and over timescales of months to decades. Effects of marine heatwaves on seabirds included shifts in distribution at sea, reduced foraging success, reduced body condition, heat stress, reproductive failures at colonies, lower chick and adult survival, mass die-offs at sea, and declines in population abundance.

Common Murre feeds chick

 

Multiple Mechanisms Are at Play

Infographic describing the effects of North Pacific marine heatwave on seabirds

The introduction article, entitled “Mechanisms by which heatwaves impact seabirds”, provides a synthesis of marine heatwave research to date. This article, co-authored by Piatt, Arimitsu, and 5 other marine scientists, summarized 20 recent publications and identified specific mechanisms that cause impacts to seabirds, the types of mechanisms that are most common, and the associated effects or consequences (impacts) for each type of mechanism. These findings indicate that marine heatwaves can affect seabirds directly by creating physiological heat stress that affects behavior or survival, or indirectly by disrupting seabird food webs, largely by altering metabolic rates in ectothermic prey species, leading to effects on their associated predators and prey and their consequences for marine food webs. 

Mechanisms by which marine heatwaves affect seabirds are: 

  • Habitat modification
  • Physiological forcing
  • Behavioral responses
  • Ecological processes or species interactions

While many seabirds are vulnerable to these mechanisms of impact, most seabird species have experienced limited effects from marine heatwaves to date, owing to ecological and behavioral adaptations that buffer marine heatwave effects. However, the intensity and frequency of marine heatwaves is increasing due to climate change, and more seabird species may have difficulty coping with future heatwave events. Also, marine heatwave impacts can persist for years after a marine heatwave ends, so consequences of recent or future marine heatwaves could continue to unfold over time for many long-lived seabird species.

Overall, this body of work provides a synthesis of global heatwave science to promote awareness of current and potential future impacts and inform future management decisions arising from this significant population stressor. 

 

Thick-billed Murres on the Pribilof Islands
Thick-billed Murres on the Pribilof Islands
Common Murres holding Pacific herring in their bill at their breeding colony on Gull Island.
Common Murres with Pacific herring
Tufted Puffin flying with three capelin in orange bill. Black body, white head and orange feet with wings spread.
Tufted Puffin carrying capelin
A Northern Fulmar on the water in Lower Cook Inlet
A Northern Fulmar on the water in Lower Cook Inlet
Skinny Common Murre flying over water with keel protruding. lower Cook Inlet, Alaska
Skinny Common Murre with keel protruding
Sarah Schoen identifies and counts Common Murre carcasses
Sarah Schoen identifies and counts Common Murre carcasses
Short-tailed Shearwater carcass on beach in Bristol Bay, Alaska
Short-tailed Shearwater carcass on rocky beach in Bristol Bay, Alaska
Dead birds on the beach
Dead Common Murres found on the beach along the Alaska Peninsula

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