cod swimming in water

Doctoral project: Uncovering mechanisms inducing thiamin deficiency in top predators of the Baltic Sea

Several species in the Northern hemisphere are suffering from vitamin B1 (thiamine) deficiency affecting performance and survival. This project is aiming to determine causes for the lack of vitamin B1 in the Baltic food web.

Project information

Doctoral student
Marc Hauber
Samuel Hylander
Other project members
Vittoria Todisco, Emil Fridolfsson, Petter Tibblin, Oscar Nordahl, Linnaeus University
Participating organizations
Linnaeus University
15 Sep 2021–31 Dec 2025
Ecology (Department of Biology and Environmental Science, Faculty of Health and Life Sciences)

Foodweb cod
Illustration showing trophic levels which the Food Web Ecology Research Group currently investigates. Trophic levels studied in this particular project are highlighted. Picture: Marc Hauber

More about the project

Thiamin deficiency, i.e. the lack of vitamin B1, has been proposed as a threat to global biodiversity. It is affecting species of varying taxa such as fish, reptiles, molluscs, and birds across Europe and North America.

Thiamin is a co-factor for at least five enzymes in essential cellular pathways and a sufficient amount is necessary to sustain basic organismal functionality. Whereas some taxa of prokaryotes, algae, and plants can synthesize thiamin, organisms in higher trophic levels such as birds and fish are thiamin auxotrophs. Hence, these organisms presumably obtain most of their thiamin by grazing/preying on lower trophic levels.

Organisms affected by thiamin deficiency are also thought to suffer from sublethal health effects such as immunosuppression, neurological damages, behavioural changes, and an altered metabolism. While these sublethal effects may reduce an individual’s survival and fitness, severe thiamin deficiency can also directly cause mortality. Especially the offspring of egg-laying organisms such as fish and birds seem vulnerable to the deficiency.

Salmonids in the Baltic Sea are periodically suffering from low reproductive output due to the thiamin deficiency syndrome called M74. Recent studies also suggest that several other species in the Baltic Sea such as eider ducks, herring gulls and cod are thiamin deficient. Throughout the years, several hypotheses have been put forward trying to explain the causes for thiamin deficiency including toxins, lipid peroxidation, thiaminase and a depleted transfer from lower to higher trophic levels. However, researchers have not been able to present enough evidence to agree upon one root cause.

Therefore, we aim to:

  1. Study thiamin deficiency as a cause for the decline of coastal fish communities in the Baltic Sea.

  2. Quantify thiamin in cod in a wide range of systems.

  3. Investigate the importance of the gut microbiota in supplying/restricting the hosts thiamin dynamics.

  4. Study the phytoplankton and zooplankton composition and their lipid composition/content over the last decades in the Baltic Sea and hereby investigate its suggested connection to thiamin deficiency in higher trophic levels.

The project is part of the research in the Food Web Ecology research group, Linnaeus University Centre for Ecology and Evolution in Microbial model Systems (EEMiS) and the Linnaeus Knowledge Environment Water.