What happens when millions - or billions - of sea animals die on one day?

[riversedge]

What happens when millions – or billions – of sea animals die on one day?
Emily Carrington

The ‘heat dome’ over the Pacific north-west brought unprecedented death to sealife. And the effects will be felt for years to come



https://www.theguardian.com/environment/commentisfree/2021/aug/05/billions-sea-animals-die-heatwave?CMP=Share_iOSApp_Other











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‘In the days immediately after the historic heat wave, I visited shorelines that looked and smelled like death.’ Photograph: Action Press/REX/Shutterstock


Thu 5 Aug 2021 06.24 EDT

Last modified on Thu 5 Aug 2021 13.17 EDT

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As a marine biologist who has studied the effects of extreme weather events for decades, I expected it would be bad. The “heat dome” brought record high air temperatures to the Pacific north-west, and for the plants and animals living along our extensive coastlines the late June timing could not have been worse. The scorching heatwave coincided with some of the lowest daytime tides of the year, leaving tidal lands exposed to hot air and sun for hours during the hottest part of the day, several days in a row.

And bad it was. In the days immediately after the historic heatwave, I visited shorelines that looked and smelled like death. Mussel, oyster and clam shells open wide with rotting tissue exposed, snails and chitons no longer able to cling to the rock, kelp and surfgrass bleached white and sloughing off dead tissue. Similar scenes were reported throughout the Salish Sea of Washington and British Columbia by scientists, shellfish growers and the general public, with mortality estimates ranging from millions to billions of individuals. We’ve never seen anything quite like this before.
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What happens next? In a few weeks, the dead tissue will be scavenged and the empty shells will wash away, leaving bare spaces behind on the shore. Gone will be all of the ecosystem services those organisms provide, such as filtering water (a single mussel or oyster can clear up to 10 gallons of seawater a day), building a moist habitat for a diverse assemblage of other species and providing food for species at higher levels on the food chain, like crabs, birds and humans.

Over the following months, areas with extensive mortality may have poorer water quality, less biodiversity and predators searching for food in vain. Populations that were not directly affected by the heatwave can suffer ripple effects from the broad disruption of ecosystem function. Shellfish growers, already struggling from reduced demand during the Covid-19 pandemic, will struggle to maintain the supply chain. As a result, the central role of aquaculture in many rural coastal economies will diminish.......................................