内容摘要：Since returning to power, US President Donald Trump has wielded tariffs – or the threat of them - as his economic weapon of choice.

Since returning to power, US President Donald Trump has wielded tariffs – or the threat of them - as his economic weapon of choice.

There was a time when China sent the highest number of foreign students to American campuses. But those numbers slipped as the relationship between the two countries soured.A more powerful and increasingly assertive Beijing is now clashing with Washington for supremacy in just about everything, from trade to tech.

Trump's first term had already spelled trouble for Chinese students. He signed an order in 2020 barring Chinese students and researchers with ties to Beijing's military from obtaining US visas.That order remained in place during President Joe Biden's term. Washington never clarified what constitutes "ties" to the military, so many students had theiror were turned away at US borders, sometimes without a proper explanation.

One of them, who did not wish to be named, said his visa was cancelled by Customs and Border Protection (CBP) when he landed in Boston in August 2023.He had been accepted into a post-doctoral program at Harvard University. He was going to study regenerative medicine with a focus on breast cancer, and had done his master's degree from a military-affiliated research institution in China.

He said he was not a member of the Communist Party and his research had nothing to do with the military.

"They asked me what the relationship was between my research and China's defence affairs," he told the BBC then. "I said, how could breast cancer have anything to do with national defence? If you know, please tell me."But it may be disrupting species' breeding patterns and could bring an influx of jellyfish that like warmer waters, including the huge barrel jellyfish, to seas and beaches.

It could also cause harmful algae to grow out of control, creating wide patches of green algae that can poison other life."We will be watching closely to monitor the impacts of the current UK heatwave on marine life and fisheries," John Pinnegar, Lead Advisor on Climate Change at the UK Centre for Environment, Fisheries and Aquaculture Science.

Previous heatwaves have caused harmful blooms of algae and in 2018 caused mass mortality among mussels.In 2023, jellyfish sightings increased by 32% following a marine heatwave with temperatures 3-4C above average.