Sea-ice extent and northward expansion of calcifying microalgae (Coccolithophores) in the Arctic.
Calcifying microalgae (Coccolithophores) are an abundant and globally important group in marine phytoplankton. They account for up to 20% of marine primary production globally, and play a crucial role in the biogeochemical carbon cycle through photosynthesis and calcification . Due to their sensitivity to environmental changes, coccolithophores are a valuable model group for studying the effects of ocean warming on marine ecosystems. Notably, their calcite scales (coccoliths) are highly sensitive to changes in ocean chemistry (e.g. ocean acidification), and their poleward expansion is seen as an indicator of large-scale shifts in ocean circulation.
Figure 1. Coccolithophore bloom in the southern Barents Sea as seen from space. Summer 2011. Source: http://earthobservatory.nasa.gov
In the southern Barents Sea, coccolithophores form massive blooms during summer, dominated by the model species Emiliania huxleyi.
These blooms are of great relevance for the Barents Sea food web, but they also have a profound effect on the local ocean chemistry and carbon cycle dynamics. In recent decades, coccolithophore blooms in the area have been shifting northwards, indicating a stronger influence of warm Atlantic waters (the process known as Atlantification) .
While the expansion of coccolithophore blooms is well evidenced from the remote sensing data (e.g. satellite imaging), little is known about the species-level patterns in the northward expansion. Understanding the capability of individual coccolithophores species for northward expansion and their response to environmental conditions in the Barents Sea (especially the sea-ice extent) will help predict the future dynamics of phytoplankton communities in the warmer Arctic.
Aim of the project
This project aims to investigate the latitudinal distribution and diversity patterns of coccolithophores in the Barents Sea and the Arctic during summer of 2018 (low sea-ice extent) and summer of 2019 (high sea-ice extent) using Scanning Electron Microscopy and the bioinformatic analysis of molecular metabarcoding data.
- Which coccolithophore species are present in the summer phytoplankton community along the Barents Sea – Arctic Ocean transect?
- How does species diversity detected with scanning electron microscopy compare to the molecular diversity detected with metabarcoding?
- How is coccolithophore community shaped by the environmental gradients along the transect and what is the effect of sea-ice extent on northward expansion of coccolithophore species?
Figure 2. Scanning Electron Microscope images of common coccolithophore species in the Barents Sea.
Photo: Luka Supraha
Scanning Electron Microscopy (SEM) – the student will learn how to prepare samples for SEM, operate the microscope and conduct the full qualitative and quantitative analysis of coccolithophore communities. Filters for SEM from two cruises in August 2018 and 2019 (in the project Arven etter Nansen) already exists for this masters project.
Metabarcoding data analysis - coccolithophore diversity and distribution will also be explored using an existing molecular metabarcoding dataset (Saubrekka et al. in prep.) and different bioinformatic tools (DADA2 package in R, biostatistics, molecular phylogeny etc.).
Data analysis – The SEM and molecular data will be combined with the environmental data and visualized using different statistical tools in R.
This Master’s project is connected to the RCN project “Arven etter Nansen” and will offer a big network of collaborators.
1. de Vargas, C. et al., 2007: Origin and Evolution of Coccolithophores: From Coastal Hunters
to Oceanic Farmers. in Evolution of Primary Producers in the Sea (eds. Falkowski, P. &
Knoll, A. H.) 251–285.
2. Oziel, L. et al. Role for Atlantic inflows and sea ice loss on shifting phytoplankton blooms in the Barents Sea. Journal of Geophysical Research: Oceans 122, 5121–5139 (2017).