The Skimmer: How weather and climate extremes are impacting the ocean

MEAM

Editor’s note: The Skimmer is a MEAM feature where we briefly review the latest news and research on a topic. Last week, I had the opportunity to attend the 4th International Symposium on Effects of Climate Change on the World’s Oceans (ECCWO)[1], held in Washington, DC. This symposium gathered scientists and managers from more than 50 nations to discuss the latest science on climate change impacts on ocean ecosystems, identify climate risks and knowledge gaps, and determine best ways to respond to sustain ocean resources and communities. Here is a quick summary of some recent and brand new research findings presented at the symposium on how weather and climate extremes are impacting marine ecosystems, as well as insights shared by speakers. (Learn about climate change tools and resources presented at the symposium in this month’s EBM Toolbox). Part 2 of the Skimmer, coming out next month, will feature more research and insights from ECCWO on how we can manage and conserve ocean ecosystems in a rapidly changing climate.

We know that extreme weather events (such as marine heatwaves) and other climate change-associated effects (including ocean warming, ocean deoxygenation, and ocean acidification) are dramatically altering marine ecosystems. But we are still figuring out the how, how much, and why of these changes. Some perspectives on what we know and what we still need to know:

What we need to do to better understand changes in species distributions (aka “range shifts”)

  • As MEAM readers are all aware, the oceans are becoming warmer because of increased concentrations of greenhouse gases in the atmosphere. The average global sea surface temperature has increased by over 1°C over the past 100 years, and the mean global ocean temperature is expected to increase by another 1-4oC by 2100.  

  • As ocean temperatures rise due to climate change, many marine populations are shifting to new areas to keep pace with their preferred environmental conditions. Marine species are moving poleward at an average of 78 km per decade, and many are also moving deeper to cooler water. Between 25 and 85% of species are shifting, with the greatest shifts occurring in areas with the greatest warming.  

  • According to Gretta Pecl of the Center for Marine Socioecology and the Institute for Marine and Antarctic Studies in Tasmania, Australia, in her plenary presentation at the symposium (watch a recording of the plenary), we are currently looking at range shifts from a species perspective – we look at the local climate velocity (the speed and direction of isotherms – lines of equal temperature – across a seascape), life history traits, physiological responses, and other direct interactions. But range shifts depend on both the “shiftiness” of species AND the receptiveness of the receiving environment.  This is similar to invasion biology where invasions depend on both the invasiveness of the invading species and invasibility of the receiving environment. Characteristics of the receiving environment such as instability of the resident ecological network are critical and represent a new frontier for research to understand range shifts.  

  • In addition, climate-driven range shifters can have massive impacts on receiving environments, akin to invasive species. In Australia, changes in the East Australian Current are bringing warm currents from New South Wales to Tasmania. The currents have introduced the voracious long-spined sea urchin to Tasmanian waters, and the aggressive grazing of this urchin is reducing kelp beds to “urchin barrens”. Additionally, according to Pecl, our focus on individual species also means we’re not looking enough at the collective impact of multiple shifting species.

How are these range shifts changing global biodiversity?

  • In a stunning display of number crunching, researchers from the Changing Oceans Research Unit at the University of British Columbia assembled 4 billion records from numerous biodiversity databases and modeled distributions for every decade between 1950 and 2100 for over 40,000 species ranging from phytoplankton to marine mammals under two climate scenarios (pg. 124). The results show that biodiversity hotspots in the ocean will vary among taxa and predict the impact of anthropogenic climate change on global marine biodiversity. In general, there will be big local biodiversity losses, but some high seas and high latitude areas may provide refuges for tropical and temperate species if they provide suitable habitats and appropriate management measures can be taken. Want to see these results? Look for them next year on the Map of Life website.

Ocean warming will create more ecological “mismatches”

Marine heatwaves – learn to expect the unexpected

Deoxygenation – the next big problem coming into focus

And ocean acidification, “global warming’s equally evil twin”

Overheard at the symposium: “Ocean acidification is heavy on losers, light on winners, and some of the winners aren’t that tasty.” [Kaplan, pg. 151]

Insight: We can’t depend on the past as a guide to the future. Extreme events can help us figure out what impacts future climate change may have

Insight: We need to accept and embrace variability in species response

  • Another major point made by many speakers during the symposium, particularly by plenary speaker Stephen Widdicombe of the Plymouth Marine Laboratory in the United Kingdom, is that the response of individual organisms to changing ocean conditions is determined by the individual’s own physiological responses, its interactions with other organisms, and the interactions of these things. This means that not all individuals or even populations of the same species will respond in the same way to climate change impacts. For instance, males and females of the same species may respond differently from each other. And populations from different parts of a species’ range may respond differently from each other. Individual variability is to be expected (and, indeed, is what drives adaptation) and more consideration needs to be given to the range of responses to climate change rather than the mean response. Watch a recording of this plenary for more great insights about conducting climate change research.

Coming soon to MEAM: Part 2: Conservation and management of marine ecosystems with shifty species; hot, acidified water; and not enough oxygen

Illustration credit: Bas Kohler for the 4th International Symposium on the Effects of Climate Change on the World’s Oceans. See more Kohler illustrations from the conference (available for use in science communications).


[1] The symposium was organized and funded by numerous entities, including the four primary sponsors ICESPICESIOC, and FAO and the local sponsor NOAA Fisheries.

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