Seasonal dynamics of Tripos-species in Oslofjorden

The genus Tripos contains large thecate dinoflagellates that are important primary producers in Oslofjorden, especially in late summer and during the fall. Sometimes they form blooms and color the water red. Because of their large size they may contribute significantly to the total phytoplankton biomass even when they do not bloom. The genus comprises more than 100 species worldwide and about 10 are recorded from Oslofjorden. Many of the Tripos-species occurring in Oslofjorden are readily identified while a few are difficult to discern. Thecate dinoflagellates are covered with cellulose plates that are used for their identification. They have a sexual life cycle and gametes of some species are very similar to the vegetative stage of other species. The project aims at elucidating the importance of Tripos-species within the phytoplankton

Field work/cruise:

Sampling onboard R/V Trygve Braarud once every month during one year.

Collect water samples and net hauls.

Measure salinity, temperature, fluorescence and water transparency.


Laboratory work:

Identify Tripos-species in net hauls using light, fluorescence and scanning electron microscopy

Cell counts of Tripos species and total phytoplankton

Calculate biomass of Tripos-species and total biomass of phytoplankton 


Research questions:

Which species of Tripos are present in Oslofjorden?

How much of total phytoplankton biomass does the Tripos-species account for?

How does the different Tripos-species vary with the seasons?




Publisert 13. aug. 2020 11:41 - Sist endret 13. aug. 2020 14:45

Omfang (studiepoeng)