“Like an icebreaker through the algal bloom”

Large blooms of cyanobacteria (algal blooms) are common in the Baltic Sea during the summer, but in recent years blooms have also occurred along the west coast of Sweden.

“Cyanobacterial toxins have also been detected in mussels and oysters on the west coast. What we want to understand is what the future might look like, as algal blooms are expected to become more common as the climate changes,” says Malin Olofsson, researcher at SLU’s Department of Aquatic Sciences and Assessment and leader of the Algtox research group. 

One expedition, two parallel missions

SMHI’s recurring July expedition is part of Sweden’s national marine environmental monitoring programme. During the expedition, SMHI oceanographers collect data on temperature, salinity, oxygen, nutrients, and phytoplankton and zooplankton at a large number of monitoring stations.

The expedition sets out from Svea’s home port in Lysekil, travels through the waters off Sweden’s west coast and continues into the Baltic Sea – a route that was ideal for Malin Olofsson and her SLU colleagues. The waters off the west coast are saline, while in the Baltic Sea salinity decreases the further north you travel. Alongside SMHI’s environmental monitoring, the SLU researchers were able to collect and process water samples with varying salinity from more than 20 stations.

Here is Malin’s account of the expedition – in words and pictures:

“Loaded up with equipment, we leave Uppsala to learn more about how filamentous cyanobacteria adapt to different salinity levels. It is sunny and warm as we head towards Lysekil, taking the Gullbritt car ferry across Gullmarsfjorden. As we drive down towards the harbour, we start seeing seagulls, and when we step out of the car we are met by warmth, sunshine and the smell of the sea.

Almost 70 metres long, SVEA stretches out along the quay, and we carry all our equipment aboard. The laboratories are well equipped, and we have plenty of space in the fish lab for our filtration work.

We get off to a wonderful start, with a calm, still sea and brilliant sunshine.

Our aim on this trip is to find what is commonly called an algal bloom – or, more precisely, cyanobacteria occurring in high concentrations, particularly in the Baltic Sea. As we travel through the southern Baltic, we can see the algal bloom spreading across the surface of the water, and we plough through it like an icebreaker. We can also see the blooms in satellite images processed daily by SMHI.

Our sampling focuses on cyanobacterial blooms and their ability to adapt to different salinity levels. We take samples at more than 20 stations to study the presence and expression of different genes, as well as metabolites. In this way, we hope to see whether differences in composition and adaptation can be linked to different salinity levels.

Back in Uppsala, we will isolate and culture species from different locations so that we can study them more closely in the laboratory. There, we can investigate how different clones from different environments respond when we change the conditions. This may help us understand their ability to spread and thrive in new environments.

Life on board is comfortable, with spacious, well-designed cabins and very good food. The chef spoils us with freshly baked bread and fika every day, Friday popcorn, Saturday sweets and well-cooked traditional Swedish food. We each have our own cabin with a toilet and shower, and there is even a gym on board with a sign on the door saying ‘fiskis och skvättis’ – a fishy play on the name of a well-known Swedish fitness organisation. Even though sampling continues around the clock and we work in shifts, we are very comfortable and well looked after.

On the final evening, as we approach the bridge to Denmark, we spot both harbour porpoises and seals in the calm water. The evening light turns purple before the sun disappears below the horizon.” 

More reading

Algtox - Knowledge Center on Algal Toxins, led by Malin Olofsson