Grethe Rytter Hasle

Grethe Berit Rytter Hasle (3 January 1920 – 9 November 2013) was a Norwegian planktologist.

Among the first female professors of natural science at the University of Oslo, she specialized in the study of phytoplankton.

Hasle was born in Borre as the daughter of shipmaster Johan Kristian Rytter (1890–1966) and his wife Nicoline Olava Nielsen (1885–1976).

She is also known for revising the morphological taxonomy of the genera Thalassiosira, Nitzschia and Fragilariopsis.

[1] She was honored with a Festschrift for her seventieth birthday, and she received the Award of Excellence from the Phycological Society of America in 2000 and the Yasumoto Lifetime Achievement Award from the International Society for the Study of Harmful Algae in 2003.