1968 Dr. philos University of Oslo, Norway; 1949; Cand. real. University of Oslo, Norway; 1942 graduated from the Teacher’s college in Elverum, Norway.

Professional Career

Grethe Rytte Hasle comes from a long tradition of leaders in Marine Botany at the University of Oslo, including famous names such as Gran, Braarud and Gaarder. She was born in the small town of Horten, at the mouth of the Oslofjord, where she grew up with a father who was a sea captain; her late husband was a navy officer. Her academic teacher, Prof. Trygve Braarud, further promoted her interest in marine and freshwater biology. Grethe Hasle started work at the University of Oslo as a Research Assistant and her first published work dates from 1950, with studies on the vertical migration of phototactic dinoflagellates and the reliability of single observations in phytoplankton surveys; her subsequent work was on the taxonomy of coccolithophorids and ciliates. In 1961, she was appointed as a Lecturer in Marine Botany, and in 1968 she was awarded her Dr. philos for a dissertation entitled "An analysis of phytoplankton of the Southern Pacific Ocean: abundance, composition and distribution during the ‘Brategg’ Expedition". Right after, in 1968-69, she was teaching and working with Antarctic phytoplankton in a position as associate professor at the Department of Oceanography at Texas A&M University. Stimulated by a study visit to "diatom guru" Dr. Friedrich Hustedt in Bremen, her true calling in life turned to diatom taxonomy, ranging from pennate (NitzschiaFragilariopsis) to centric (Thalassiosira, Cymatosira) genera, and eventually covering samples from every corner of the globe.

As a pioneer in the use of combined light, scanning and transmission electron microscopy, she became an internationally renown expert on diatom microarchitecture, describing what was finally named strutted and labiate processes in the diatom family Thalassiosiraceae. She has been supervising students from all over the world and her dedication to the study of diatoms has inspired diatomists around the world. Grethe Hasle was nominated as a Full Professor in Marine Botany at the University of Oslo in 1977.


2002 Yasumoto Lifetime Achievement Award by the International Society for the Study of Harmful Algae; 1999 Excellence Award by the Phycological Society of America; 1980 elected member of the Norwegian Academy of Science and Letters; Etymology of the diatom genus Haslea, Dinophysis hasleae, Nanoneis hasleae,Praethalassiosiropsis hasleae, Thalassiosira hasleae.

Key contributions

The lasting quality of Grethe Hasle’s work is well illustrated by her 1965 publication in "Skrifter utgitt av Det Norske Videnskaps-Akademi", on the group Pseudo-nitzschia within the diatom genus Nitzschia. She paid careful attention to details of the number of striae and fibulae, rows of poroids on the striae membrane, the presence/absence of a central interspace, as well as to diatom type material. This ground-breaking work, which was well ahead of its time, includes a description of Nitzschia pungensforma multiseries (now Pseudo-nitzschia multiseries; type locality Drøbak; as distinct from P. pungens), which in 1987-88 was found to be responsible for the production of domoic acid, causing Amnesic Shellfish Poisoning in Prince Edward Island, Canada. Grethe Hasle’s research is thus a prime example of the importance of basic science. Ever since, Grethe has been painstakingly assisting workers from all over the world, coming to grips with the bedazzlingly difficult taxonomy of this domoic-acid-producing genus, culminating in her 2002 review in "Harmful Algae" on the global distribution of toxigenic Pseudo-nitzschia species.

A dedicated website on Pseudo-nitzschia is being maintained by Steven Bates (an honour not bestowed on any other diatom!). Responding to a recommendation of the SCOR Working Group 33 on Phytoplankton Methods (which also led to the 1978 Sournia Phytoplankton Manual), starting in 1976, Prof. Hasle was instrumental in organising UNESCO phytoplankton training courses for experienced participants, where she taught the diatom portion. The 1976 course was offered at the field station of the University of Oslo and the next two at Drøbak; they later moved to the Stazione Zoologica Anton Dohrn Napoli, where she continued her teaching. Her UNESCO diatom lecture notes were published in 1996 as part of an authoritative 300-page chapter (co-authored with Erik Syvertsen) in "Identifying Marine Diatoms and Dinoflagellates"; and an updated chapter on the taxonomy of harmful diatoms (co-authored with Greta Fryxell) appeared in the 2003 UNESCO Manual on Harmful Marine Microalgae".

Grethe Hasle admirably is continuing her prolific publication output well after retirement and into her late eighties, publishing at least one paper per year and still keeping up her high standard. Notable publications after retirement includes a paper on Thalassionemataceae in Diatom Research, 2001 and the diatom part of the book “Phytoplankton of Norwegian coastal waters” by Throndsen, Hasle & Tangen in 2007. Being asked what she thought was the most important question in marine phytoplankton on which to work. she answered, "What is there, and how much of it is there?". "When things get too bad in your personal life, turn to the microscope!". Grethe Hasle continues her activities not only within science. She was going on skiing holidays with her grandchildren into her eighties and she is still going on vacations to her log cabin with her grandchildren and still travels around in Oslo in her little car, driving home at night even after terrible snow falls that keep other people at home.


Greta Fryxell, Rita Horner, Karina Lange, Nina Lundholm, Erik Syvertsen.

10 Key publications

Fryxell, G.A., Hasle, G.R. 2003. Taxonomy of harmful diatoms. In: G.M. Hallegraeff, D.M. Anderson, A.D. Cembella (eds.). Manual on Harmful Marine Microalgae. IOC Manuals and Guides, UNESCO, Paris.

Hasle, G.R., Syvertsen, E.E. 1996. Marine Diatoms. In: Tomas, C.R. (ed.) Identifying Marine Phytoplankton. Academic Press, Inc. pp. 5-385.

Hasle, G.R., Syvertsen, E.E., Lange, C.B. 1996. A review of Pseudo-nitzschia, with special reference to the Skagerrak, North Atlantic, and adjacent waters. Helgoländer Meeresuntersuchungen 50, 131-175.

Hasle, G.R. 1995. Pseudo-nitzschia pungens and P. multiseries (Bacillariophyceae): nomenclatural history, morphology, and distribution. J. Phycol. 31, 428-435.

Hasle, G.R. 1973. Some marine plankton genera of the diatom family Thalassiosiraceae. Nova Hedwigia, Beih. 45, 1-49.

Hasle, G.R. 1972. Two types of valve processes in centric diatoms. Nova Hedwigia, Beih., 39, 55-78.

Hasle, G.R. 1972. The distribution of Nitzschia seriata Cleve and allied species. Nova Hedwigia, Beih. 39, 171-190.

Hasle, G.R. 1965. Nitzschia and Fragilariopsis species studied in the light and electron microscopes. III. The genus Fragilariopsis. Skr. norske Vidensk Akad. I. Mat. Nat. Kl. N.S. 21, 1-49.

Hasle, G.R. 1965. Nitzschia and Fragilariopsis species studied in the light and electron microscopes. II. The group Pseudo-nitzschia. Skr. norske Vidensk Akad. I. Mat. Nat. Kl. N.S. 18, 1-45.

Hasle, G.R. 1964. Nitzschia and Fragilariopsis species studied in the light and electron microscopes. I. Some marine species of the group Nitzschiella and Lanceolatae. Skr. norske Vidensk Akad. I. Mat. Nat. Kl. N.S. 16, 1-48.

(Based partly on: Phycological Newsletter 36 (1), 10-11 (2000); portrait: University of Oslo).