Sushi Parasite Has Increased 283x in Nearly 40 Years
The population of a marine parasite that sometimes worms its way into sushi has increased by 283 times in the last nearly 40 years, a University of Washington (UW)-led study has found.
The study, published in Global Change Biology Thursday, reviewed the literature and found a significant rise in the abundance of the parasite Anisakis, or "herring worm." This isn't especially concerning for humans, who experience the worm as a nasty bout of food poisoning that then resolves, but it could have serious consequences for marine mammals, who play host to the parasites for years.
"One of the important implications of this study is that now we know there is this massive, rising health risk to marine mammals," study coauthor and UW School of Aquatic and Fishery Sciences assistant professor Chelsea Wood said in the UW press release. "It's not often considered that parasites might be the reason that some marine mammal populations are failing to bounce back. I hope this study encourages people to look at intestinal parasites as a potential cap on the population growth of endangered and threatened marine mammals."
The next time you eat sashimi, nigiri or other forms of raw fish, consider doing a quick check for worms. 🍣😳 https://t.co/juL5dW2NDu— UW SAFS (@UW SAFS)1584649387.0
The researchers looked at a total of 123 papers published between 1967 and 2017 to assess how the abundance of two marine parasites had changed over time: Anisakis and another parasite known as Pseudoterranova, or "cod worm." Anisakis abundance rose 283-fold from 1978 to 2015, while Pseudoterranova abundance did not change. This means that Anisakis has risen from less than one for every 100 hosts caught to more than one in every host caught, ScienceAlert explained.
Ironically, while Anisakis might threaten the health of marine mammals, its rise may have been triggered by their success.
"My gut is that this is about the improvements we've made in marine mammal conservation," Wood told ScienceAlert. "The time frame of our study directly overlaps with when a bunch of really important marine mammal legislation went into effect like the Marine Mammal Protection Act in 1972 and the international whaling commission moratorium on commercial whaling which came in the 1980s."
The one wrinkle in this theory is which mammals usually play host to the worm. Anisakis hatches in the ocean and first infects small animals like shrimp, the UW explained. They then make their way up the food web as the shrimp are eaten by fish, who are eaten by bigger fish, until they end up in the intestines of Cetaceans like whales or dolphins. Here they can live and reproduce for years, reentering the ocean in the animals' feces to start the cycle again.
While Anisakis abundance has risen, Pseudoterranova, which typically infects fish, sea lions and seals, has not. However, seals and sea lions have done much better than whales, Wood told ScienceAlert, which means one would expect Pseudoterranova abundance to have increased instead. However, she speculated it was possible the parasite was actually increasing because it had fewer hosts to pass through.
Other factors that could have caused the rise include the climate crisis and increased runoff from fertilizers, according to the press release.
So what happens if humans happen to ingest one of the worms? Nausea and vomiting that is unpleasant, but temporary.
"When they enter the intestine of a human, it's a great disappointment to the worm. They're not going to be able to complete their life cycle there," Wood told New Scientist.
Wood said that sushi lovers shouldn't worry, as chefs were expert de-wormers.
"I still eat sushi all the time," she told New Scientist.
However, if you are concerned, just cut your nigiri in half and look for worms yourself, she advised in the press release.
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By Harry Kretchmer
By 2030, almost a third of all the energy consumed in the European Union must come from renewable sources, according to binding targets agreed in 2018. Sweden is helping lead the way.
Sweden is a world leader in renewable energy consumption. Swedish Institute/World Bank
Naturally Warm<p>54% of Sweden's power comes from renewables, and is helped by its geography. With plenty of moving water and 63% forest cover, it's no surprise the <a href="https://sweden.se/nature/energy-use-in-sweden/#" target="_blank">two largest renewable power sources</a> are hydropower and biomass. And that biomass is helping support a local energy boom.</p><p>Heating is a key use of energy in a cold country like Sweden. In recent decades, as fuel oil taxes have increased, the country's power companies have turned to renewables, like biomass, to fuel local 'district heating' plants.</p><p>In Sweden these trace their <a href="https://www.sciencedirect.com/science/article/pii/S0360544217304140#fig3" target="_blank">origins back to 1948</a>, when a power station's excess heat was first used to heat nearby buildings: steam is <a href="https://www.sciencedirect.com/topics/engineering/district-heating-system" target="_blank">forced along a network of pipes</a> to wherever it's needed. Today, there are around 500 district heating systems across the country, from major cities to small villages, providing heat to homes and businesses.</p><p>District heating used to be fueled mainly from the <a href="https://www.sciencedirect.com/science/article/pii/S0360544217304140" target="_blank">by-products of power plants</a>, waste-to-energy plants and industrial processes. These days, however, Sweden is bringing more renewable sources into the mix. And as a result of competition, this localized form of power is now the country's<a href="https://www.sciencedirect.com/science/article/pii/S0360544217304140#fig3" target="_blank" rel="noopener noreferrer"> home-heating market leader.</a></p>
Sweden is using smart grids to turn buildings into energy producers. Huang et al/Elsevier
Energy ‘Prosumers’<p>But Sweden doesn't stop at village-level heating solutions. Its new breed of energy-generation takes hyper-local to the next level.</p><p>One example is in the city of Ludivika where 1970s flats <a href="https://www.buildup.eu/sites/default/files/content/transforming-a-residential-building-cluster-into-electricity-prosumers-in-sweden.pdf" target="_blank">have recently been retrofitted with the latest smart energy technology</a>.</p><p>48 family apartments spread across 3 buildings have been given photovoltaic solar panels, thermal energy storage and heat pump systems. A micro energy grid connects it all, and helps charge electric cars overnight.</p><p>The result is a cluster of 'prosumer' buildings, producing rather than consuming enough power for 77% of residents' needs. With <a href="http://www.diva-portal.org/smash/get/diva2:1232060/FULLTEXT01.pdf" target="_blank" rel="noopener noreferrer">high levels of smart meter usage</a>, it's a model that looks set to spread across Sweden.</p>
<div id="d7bf9" class="rm-shortcode" data-rm-shortcode-id="8757b138d5570bec9d6aad18074a429a"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1273556364263071744" data-partner="rebelmouse"><div style="margin:1em 0">Read more about Western Harbour and book a visit: https://t.co/ujSmVs9rNK 🏡🌳🌊 https://t.co/C5PuPziqIM</div> — Smart City Sweden (@Smart City Sweden)<a href="https://twitter.com/SmartCitySweden/statuses/1273556364263071744">1592474473.0</a></blockquote></div>
Scaling Up<p>A recent development by E.ON in Hyllie, a district on the outskirts of Malmö, southern Sweden, <a href="https://www.eonenergy.com/blog/2019/February/sweden-smart-city" target="_blank">has scaled up the smart grid principle</a>. Energy generation comes from local wind, solar, biomass and waste sources.</p><p>Smart grids then balance the power, react to the weather, deploying extra power when it's colder or putting excess into battery storage when it's warm. The system is not only more efficient, but bills have fallen.</p><p>Smart energy developments like those in Hyllie, Ludivika, and renewable-driven district heating, offer a radical alternative to the centralized energy systems many countries rely on today.</p><p>The EU's leaders have a challenge: how to generate 32% of energy from renewables by 2030. Sweden offers a vision of how technology and local solutions can turn a goal into a reality.</p>
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By Jessica Corbett
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