Responsible: Olav Myrann
E-mail: olavmy@student.ibv.uio.no
Supervisors: Bente Edvardsen, Simon Hasselø Kline and Tom Andersen
Aim
The primary aim of this master’s project is to gather further knowledge on the abiotic factors affecting the important spring bloom diatom genera Skeletonema and Chaetoceros, and how potential anthropogenic changes may affect their growth. The secondary aim is to research how variations in salinity might affect the interactions between Skeletonema, Thalassiosira and Chaetoceros during the spring bloom.
Background
The Oslofjord has experienced changes in abiotic factors and the species composition of phytoplankton throughout the last century. Anthropogenic impact is a leading cause of changes in the abiotic factors such as increased level of nutrients, temperature, change in salinity, ocean acidification and costal water browning. Climate change affects the fjord in multiple ways, the fjord becomes more brackish, the mean temperature and the amount of POM (Particulate organic matter) and DOM (Dissolved organic matter) released into the fjord from land has increased. Phytoplankton species have different optimums of temperature, salinity, light conditions, and access to nutrients. The spring bloom is usually started by diatoms in temperate waters. The amount of available nutrients determines the abundance of diatoms in time and space, but temperature and light availability are other important factors for the bloom of diatoms.
Diatoms are the dominating taxa during the spring bloom in the Oslofjord, with members of the genera Skeletonema, Thalassiosira and Chaetoceros playing substantial roles. In the last 15 years there has been a recorded reduction in Skeletonema abundance during the spring bloom, driving an overall reduction of diatom biomass in the Oslofjord. In comparison the biomass of other diatoms such as Chaetoceros has remained stable in the same period, while the relative abundance of heterotrophic and mixotrophic dinoflagellates have remained stable in comparison to the autotrophic diatoms since 2006. Research indicates that Skeletonema favors a colder environment with higher salinity in comparison to other common diatoms such as Chaetoceros and Thalassiosira.
Research Questions
1. How do different combinations of salinity and light intensity affect the growth rate of Skeletonema and Chaetoceros cultures?
2. What is the compensation light intensity of tested species of Skeletonema and Chaetoceros across the various tested salinities?
3. How does salinity affect the cultures of Skeletonema, Chaetoceros and Thalassiosira when they are grown in a common garden experiment?
4. Is the Planktoscope reliable enough to be used to quantify cell abundances in a phytoplankton common garden growth experiment?