Alf Norkko is a Professor in Baltic Sea Research at the University of Helsinki. Years of diving and studying marine sediments have given him a unique, bottom-up perspective of the world’s most widespread habitat, the seafloor. In this edition, Professor Norkko explains how much there is to learn about the Baltic Sea by sifting through its very foundations.
“There is a whole different world when you put your head under the sea,” says Norkko who has been diving in the Baltic Sea for more than 30 years. He describes himself as an ecologist and systems scientist whose research aims to understand how the Baltic Sea works as an ecosystem. Although it is a shallow sea with a mean depth of only 60 metres, there is huge variability in types of sediment. In the southern Baltic alone, there are sandy coastlines, moraines and bedrocks which create an array of different environments and diverse habitats.
Norkko compares the sediment to compost due to its composition: organic matter, nutrients as well as decades worth of pollution. Eutrophication and low oxygen levels have led to large areas that are devoid of life. In recent years bottom trawling in certain areas, mineral extraction, dredging and building of coastal infrastructure have impacted the seafloor. For the Baltic Sea, this is problematic because there is such limited exchange.
Unless we have a profound understanding of the seafloor, we cannot solve the problem.
“Understanding the seafloor is a good place to start because it is connected to every part of the marine ecosystem. As an almost entirely enclosed sea, the Baltic is special in several ways. The exchange of nutrients between the seafloor and the water column above it becomes very intense because the Baltic is so shallow. Ecosystems are adapted to the low salinity, and the combination of these two factors alone results in a shallow basin where interactions are strong and there are rapid consequences of any changes in temperature, nutrient cycling and disturbances of the seafloor. Algal blooms are a good example of a visible indicator of disruption in the careful balance of nutrient cycling by benthic communities.”
What measures should be prioritized to allow efficient recovery of disturbed marine sediment?
A Decade for Ocean Science
“Sometimes we’re a bit slow to take the lead but there is such a strong and long history of collaboration in the Baltic. We can really take the lead as a region. Science and the communication of science can play an important role too. Every second breath comes from the oceans and expanding society’s knowledge about the sea and the seafloor is crucial in fostering care for an environment that is still so unknown. Now that we’ve entered the UN’s Decade for Ocean Science, the opportunity has come to share knowledge about the seafloor and help people to appreciate these vast sources of life.”
We know more about the moon than our seafloor
As in other parts of the global ocean, the Baltic seafloor is highly varied. Multiple gradients and sediment types influence the web of life in the different environments. ”Each of these environments requires a slightly different approach to management. One size does not fit all so a more localized, tailored management approach is necessary. For that, we need a local and in-depth understanding of each part of the seafloor.
We closed by asking Professor Norkko what first drew him to the depths of the ocean.
This article is part of the WWF Baltic Newsletter – May 2021
