What will you do at Askö?

We propose to investigate the bloom during different stages and compare P uptake and storage from the beginning to the end of the bloom. During our experiments we will measure PO43- concentrations, collect N2-fixing cells and colonies and incubate them with 13C, 15N and 33P isotopes. By this approach we are able to show how these N2-fixers cope with P availability throughout their whole blooming season.

Project background

Marine Diazotrophs also known as ‘nitrogen fixers’ are a specific group of bacteria that are the only organisms capable to use nitrogen gas (N2) dissolved in seawater and transform it into ammonium (NH4+), a nitrogen (N) source that can be used by other organisms. Because of this unique capability diazotrophs act as natural fertilizers for the oceans and seas, where N is often the limited available nutrient for growth. Though diazotrophs do not experience N shortage, other nutrients like phosphorus (P) have a strong influence on their growth and fertilizing capabilities. The expedition to the Askö marine laboratory will be the first opportunity to test a novel technique in the field for investigating single bacterial cell Carbon, N and P requirements. By applying this very sensitive technique we can unravel the different P requirements and survival strategies of specific diazotrophic species in the Baltic. The results of this project will give us new insights on the effects of P availability on diazotrophs and their fertilizing role in today’s seas and oceans.

Niels Schoffelen, Max Planck Institute for Marine Microbiology, University Bremen