Karsten made her debut as a 19-year-old at Barcelona 1992 as part of the Unified Team, where she won bronze in the quadruple sculls.

She has competed in the singles sculls ever since, taking gold at Atlanta 1996 and Sydney 2000, silver at Athens 2004 and bronze at Beijing 2008.

She finished in fifth place at London 2012.

The six-time world champion has been less dominant in recent year, but has still be competitive, showing this by finishing in third-place behind New Zealand's Emma Twigg in the final.

Twigg, returning to the sport following a break after winning gold during the 2014 World Championships, recovered from a sluggish start to power ahead after halfway.

Ireland's Sanita Puspure finished second as Denmark's Fie Udby Erichsen secured the final qualifying slot in fourth.

“It was a good race, said I thought I want to qualify, but in sports anything can happen," said Karsten, who is set to become the eighth woman to compete at seven Olympic Games.

Canoeist Josefa Idem Guerrini competed at her eighth Games at London 2012, the first two for West Germany and the remainder for Italy.

Twigg added that she "really felt the pressure to perform today after my year off", but that she now feels definitely on track for gold in Rio.

Belguim's Hannes Obreno produced as superb performance to win and qualify in the men's single sculls along with second-placed Australian Rhys Grant and Bendeguz Petervari-Molnar of Hungary.

There was Danish disappointment as Sverri Nielsen missed out, while there was further blow as Olympic champions Mads Rasmussen and Rasmus Quist missed out in the lightweight double sculls.

Belgium's Tim Brys and Niels van Zandweghe continued a good day for the country by winning the race ahead of Turkey's Huseyin Kandemir and Enis Kusku.

Spain's Anna Boada Peiro and Aina Cid led the women's pair qualifiers ahead of China's Min Zhang and Tian Miao, while Czech Republic's Jakub Podrazil and Lukas Helesic won the men's pair final.

Kristyna Fleissnerova and Lenka Antosova claimed a second Czech victory in the women's doubles scull.

Olaf Tufte remains in line for a fourth Olympic medal and third gold after winning the men's double sculls event with Norwegian team-mate Kjetil Borch.

South Africa and France qualified in the coxless four, while Russia and Germany secured lightweight four slots.

Romania and The Netherlands each qualified in the women's eight while United States and Poland secured the two men's positions.