There was plenty of tension at Sava Lake in the Serbian capital with rowers knowing that a top-five place would secure a ticket to Paris 2024.

Ayers and Altschwager triumphed in a time of 8min 7.07sec to take the title ahead of the American crew of Gemma Wollenschlaeger and Todd Vogt who finished in 8:15.22.

Defending champions Laurent Cadot and Elur Alberdi of France came third in 8:27.09.

Britain’s Annabel Caddick and Samuel Murray and Germany’s Valentin Luz and Hermine Krumbein also clinched Paralympic qualification spots.

"We’ve worked so hard over the last 18 months," said Altschwager.

"To get down to this morning waking up knowing today was the day we had to race the final was amazing.

"To get it done, it’s incredible."

Tokyo 2020 silver medallist Corné de Koning of The Netherlands captured the PR2 men’s single sculls crown in a time of 9:48.32.

Italy’s Gian Filippo Mirabile sealed silver in 10:08.88, with Germany’s Paul Umbach bagging bronze in 10:42.49.

There was also double delight for Ukraine, with Ivan Kupriichuk and Andrii Syvykh winning the PR3 men’s coxless pairs title in 8:30.78 and Anna Aisanova sealing PR2 women’s single sculls gold in 12:03.39.

Switzerland’s Andri Struzina became the first world rowing champion of 2023 after topping the standings in the men’s lightweight single sculls in 7:42.41.

Italy’s Niels Torre picked up silver in 7:44.90, with Poland’s Artur Mikołajczewski clinching bronze in 7:47.72.

"It’s indescribable, unbelievable," said Struzina.

"Calling myself a world champion is nothing I could have imagined at the beginning of the season.

"Now I have to realise it and it takes some days to really understand what I have achieved."

Siobhan McCrohan delivered gold for Ireland with victory in the women’s lightweight single sculls final.

The Irish rower took the title in 8:47.96, beating Mexico’s Kenia Lechuga and American Sophia Luwis who clocked 8:51.57 and 8:52.48 respectively to complete the podium.

Italy swept to success in the non-Olympic lightweight boat classes, triumphing in the lightweight men’s and lightweight women’s pairs and lightweight men’s quadruple sculls.

Olympic quota places were also awarded in a busy morning of races as double Olympic bronze medallist Damir Martin of Croatia booked his spot at a fourth Games in the men’s singles sculls.

He finished third behind defending world champion Oliver Zeidler of Germany and Olympic gold medallist Stefanos Ntouskos of Greece.

New Zealander Thomas Mackintosh, Denmark’s Sverri Nielsen and Netherlands’ Simon van Dorp also sealed places.

Martin and Valent Sinkovic of Croatia also qualified for a fourth Olympics after winning their men’s double sculls semi-final.

Crews from The Netherlands, Italy, China, Ireland and Spain also made it through to Paris 2024.

New Zealand’s Emma Twigg clinched her place at a fifth Olympic Games while there was also success for Kara Kohler of the US, Desislava Angelova of Bulgaria, Australia’s Tara Rigney, Viktorija Senkute of Lithuania and The Netherlands’ Karolien Florijn in the women’s single sculls semi-finals.

The US, Ireland, France, Romania, Lithuania and New Zealand qualified boats for the Olympics in the women’s double sculls.

Italy, Ukraine, Britain, Israel, Germany and Australia clinched Paralympic quota places in the PR1 men’s single sculls.

Competition is due to continue tomorrow.