Exploration of community dynamics of protists during the autumn season through metabarcoding and intensive sampling.

Sammendrag

Increasing anthropogenic stressors and climate change are contributing to shifts in phytoplankton communities, which has significant consequences for marine ecosystems and biogeochemical cycles. Temperate regions, like Southern Norway, have distinct spring and autumn phytoplankton blooms which often differ in species composition due to variations in temperature, salinity, and light conditions, as well as nutrient availability. However, the autumn bloom is less explored than the spring bloom. Traditionally, phytoplankton monitoring programs collect samples once a month in the production period, this frequency may miss important aspects of population dynamics and species composition, especially during periods with rapid environmental and biological changes. This master’s project aims to get a better understanding of the phytoplankton autumn bloom in the Oslofjord. We intend to see if there is a difference in the composition and timing of the autumn bloom between the inner and outer Oslofjord, and whether frequent sampling reveals more of the changes over time and locality than traditional monthly sampling. This will be done through water sampling twice a week for about a month (mid-September to mid-October) in 2023 and 2024 from two marine sampling stations. The community diversity and composition will be examined by high throughput Illumina sequencing (using the V4 region of the 18S rRNA gene). Environmental factors, such as chlorophyll-a concentrations, along with nutrient and cDOM will be measured. Preliminary results from 2023 indicate differences in chlorophyll-levels between the stations, as well as temporal differences. Additionally, there appears to be weekly fluctuations in chlorophyll levels even with frequent sampling.