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Connectivity and transport patterns in the Baltic Skeletonema marinoi spring bloom: A joint Nordic Research Network (PRODIVERSA) study using ships of opportunity as a sampling platform

Anke Kremp, Karin Rengefors, Nina Lundholm, Sanna Suikkanen, Mireia Bertos, Carina Bunse, Susanna Gross, Sara Hardardottir, Ingrid Sassenhagen, Josefin Sefblom, Sirje Silvender, Conny Sjöqvist, Anna Godhe

 

 

 

 

In the Baltic Sea the spring phytoplankton bloom is the most important contributor to the annual new production. Typically it starts in the south in February, continues developing along the S/N gradient through March and peaking in late April in the North (Fig. 1). While the coastal blooms are genetically differentiated and likely to be seeded by local benthic resting stages, the origin and the extension of open sea blooms is not clear. This study investigates whether the successive spreading is a result of northward transport of one southern Baltic population by surface currents, or whether phased local initiation is due to gradual warming. We study connectivity and potential transport pattern within the Baltic spring bloom using temporal and spatial genetic structure information of the spring bloom diatom Skeletonema marinoi (Fig.2) .

Fig. 1: Weekly progression of the Skeletonema marinoi bloom in the Baltic Sea (black = low biomass, red = intermediate biomass, green = high biomass)

10 µm

Fig. 2: Light micrograph of Skeletonema marinoi

Fig. 3: Peaks of 3 microsatellite loci from the DNA of a Baltic S. marinoi isolate

Skeletonema marinoi is one of the most abundant members of the Baltic spring phytoplankton community and present throughout the entire Baltic. The species has been studied extensively in monitoring programs and population genetic tools (microsatellite markers, Fig. 3) are available.

We record and analyze the genetic structure of Skeletonema marinoi isolates grown from bloom samples (surface water) taken during 4 successive cruises in March and April 2013 along the S/N transect through the Baltic proper. Sampling is performed using the Algaline sampling platform onboard Finnmaid at 11 set stations across the passage through the Baltic Sea (Fig. 4). Live samples are processed and concentrated in the Algaline wet lab (Figs. 5 and 6) and 50 individual chains are isolated from each sampling point immediately, using the microscope (Fig. 7). Isolates are grown (Fig. 8) in the laboratory, harvested when dense cultures have established, and DNA extracts are genotyped. Transport processes will be inferred from gene flow data and physical-biological dispersal models.

Fig. 4: Samplingstations

PROJECTS

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