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Krill on the MAR

Krill (Euphausiacea) are typical and abundant members of macrozooplankton, but their abundance and distribution remain poorly known even in the Atlantic Ocean. Bsc-student Tom Bech Letessier has analysed krill-samples from the 2004 "G.O Sars"-expedition!
Tom Letessier

Student of the month
Tom Bech Letessier

Topic
Describing the abundance and distribution of krill associated with the MAR

Background
Fourth year Bsc Hon Marine Biology University of Aberdeen

Completed
On 27 January 2006, Letessier successfully defended his thesis


Figur 1: An example of Thysanopoda cornuta, and giant deep sea species

Krill (Euphausiacea) are typical and abundant members of macrozooplankton but their abundance and distribution remain poorly known even in the Atlantic Ocean. Krill are similar in shape and size to shrimps, but are different in that they have exposed gills, below their carapace. In many marine ecosystems krill function as direct connections between the primary producers (phytoplankton) and the higher trophic groups, like fish, whales and birds. Krill is in many waters a major source of food for pelagic fishes, including some that are commercially exploited commercial. It is important to determine which species are present on the  MAR and how abundant they are.


Figur 2: An example of Meganyctiphanes norvegica, a typical euphausiid in the North Atlantic 
Krill-samples were collected on the 2004 "G.O Sars"-expedition using a macrozooplankton trawl equipped with five cod-ends. This gear enabled us to collect samples from different depths and to describe the vertical distribution of the individual species. 17 sites were sampled, each situated close to the MAR.

The samples were identified over the summer 2005 at the Institute of Marine Research, in Flødevigen, Norway, looking at the shape of their eyes and rostrum. Each individual was weighed and measured, in order to describe the overall characteristics of the population.

An interesting finding


Figur 3: Population size frequency distribution of Thysanopoda cornuta. X-axis represent carapace length in mm. Y-axis represent frequency.

Eleven species were identified, some typical, like Meganyctiphanes norvegica and Thysanopoda acutifrons, and some rare, like Thysanopoda egregia and T cornuta. Statistical analyses indicated that species clustered in to three types of habitats, all in relation to the temperature of the water. Analyses of diversity also showed that the diversity increased with decreasing latitude, or probably rather as water becomes warmer moving southwards. 

Some of the results suggest that the species composition is different on either side of the MAR, an interesting finding in relation to major questions addressed by MAR-ECO!

Meet the MAR-ECO post-graduate students and their projects in the student profiles:

Dangerously delicious?
Inger Marie Tyssebotn
Bachelor student projects
HiÅ B.Sci. students
Bone Atlas
Amy Heger
MAR-ECO jigsaw
Vanda Carmo
Systematics project
David Rees
What are dolphins doing along the mid-Atlantic ridge?
Lise Doksæter
DNA from shrimp diet
Helene Axelsen
Krill on the MAR
Tom Letessier
Biology and distribution patterns of some deep-sea fishes
Inge Fossen
The distribution of Lophogastrida
Pål Øyvind Aas
Analyses pictures of deep-sea life
Nicola J. King
Food for thought. What do deep-sea fish have for dinner?
Guro Gjelsvik
Jellies - challenging objects to study
Aino Hosia
~ see also students & scholarships
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