Seasonal dynamics of the protist community in the Oslofjord and Skagerrak in a changing ocean

Responsible: Simon Hasselø Kline

Supervisors: Bente Edvardsen, Alexander Eiler, Tom Andersen, Josefin Titelman and Wenche Eikrem.

Collaborating researchers: Olli Hyvarinen and Eivind Stensrud. 

Aim

To better understand the diversity and dynamics of protists in the Oslofjord and Skagerrak, and the abiotic factors and biotic interactions that can explain the observed community changes.

Background

Single-celled protists constitute the majority of the diversity found within the Eukaryota domain of life and contain the oldest form of eukaryote life (Knoll, 1992). In our oceans, marine protists can be producers, consumers, or decomposers, serving as vital links between the various trophic levels and contributing to the biogeochemical cycles (Caron et al., 2012). As aquatic protists and microbes compose approximately 90% of the biomass in our oceans (Biddanda et al., 2021), any changes within the protist community are likely to have reverberating effects throughout the remaining ecosystem, which in turn may affect the overall resilience of marine ecosystems to changing conditions.

Climate and land use changes are already altering the hydrological cycle and the interactions between land and sea, with coastal waters experiencing increased browning as a result of increased extreme weather, precipitation, erosion and run-off. This browning reduces water clarity, which in turn can affect the timing of the spring bloom. A darkening of the water masses has already been observed in the North Sea, which has led to a 3-week delay in the spring bloom over the last century (Opdal et al., 2019). There are several indications that the Oslofjord and Skagerrak regions are experiencing a coastal darkening (Kile et al., 2018), that potentially may cause a delay in the spring bloom.

Research Questions

1. How has the protist community structure in the Oslofjord and Skagerrak changed over the last 14 years, as revealed by metabarcoding? Which physiochemical conditions can explain the variation in community composition? 
2. Through 20 years of Ferrybox chlorophyll fluorescence data, how has the timing and biomass of the phytoplankton spring bloom changed over time? Can coastal darkening and reduced transparency explain the observed delay in the spring bloom?
3. How does the phytoplankton species composition vary during the spring bloom period?
4. Can zooplankton grazing lead to a suppressed and/or delayed spring bloom? 
5. What role can citizen science play in plankton research and environmental awareness and how do the obtained results compare to those gathered by previous research? 

This PhD project will hopefully fill in some of the knowledge gaps that exist with regards to protist diversity and dynamics in the Oslofjord and Skagerrak, and provide insight into how global trends such as freshening and browning of oceans affect the pelagic community. This knowledge could then aid in future environmental policy and decision-making.