Flounders breeding successfully in the Icelandic biosphere
Although a large number of marine species can swim or be carried great distances by the currents, the introduction of species to new areas is probably largely down to human activity. It is believed that most of these introduced species are transported far from their original homes in the bilge water of ships. Bilge water often contains the roe, larvae and juveniles of species which then manage to establish themselves in the new area. Thousands of non-native species are introduced in this way each year. However, this may not be the case for the European flounder (Platichthys flesus), since the roe and juvenile fish could both potentially be carried long distances by ocean currents.
Iceland's coastal waters are a delicate ecosystem
The marine biosphere around Iceland is incredibly vulnerable to changes and scientists do not fully understand how invasive species affect the natural balance of the ecosystem. The Atlantic rock crab, a North American species that until recently was not found in Iceland, is one example that has become well established here, with numbers increasing dramatically in just a few years. The European flounder is another species that has been extremely successful in the Icelandic biosphere in a very short time. Based on the distribution of the flounder, it is clear that the species has been spawning in Icelandic waters for many years.
Theresa Henke is one of the many scientists of foreign origin at UI. Their contributions have been invaluable in UI's mission to become a respected international research university. At the same time, influences from abroad have made the University into a more diverse community of students and staff, in the spirit of our comprehensive strategy, UI26.
Theresa is also one of a number of early-career researchers looking at non-native species in the Icelandic marine ecosystem. The focus of her PhD has been on the European flounder, following on from her Master's research into the same species. The European flounder is now defined as potentially invasive, since over the span of about two decades it has managed to spread around the entire country. Although flounders were first observed off the south west coast at around the turn of the century, they are now found in estuaries and rivers as remote as the highest parts of the Hornstrandir nature reserve.
Harnessing the knowledge of the public for research
The European flounder is a popular edible fish with a delicious flavour. In appearance it most closely resembles a dab or a plaice and is generally around 30-40 cm long.
"Since it was first observed off the south west coast in 1999, the flounder has become well established throughout Icelandic waters. It is most commonly found in estuaries but also enters rivers and lakes along with native salmonid species such as the Atlantic salmon, the brown trout and the Arctic char," says Theresa Henke, who is based at the UI Research Centre in Bolungarvík. The Research Centre has been home to a range of research on marine biodiversity under the leadership of the biologist Guðbjörg Ásta Ólafsdóttir, who is actually Theresa's main supervisor for this project. A particular focus for the Research Centre has been the Icelandic commercial stocks which have formed the backbone of the fishing industry and the processing and sale of seafood.
Theresa's main research interest is the impact of invasive species on established ecosystems. She is also interested in sharing information about biological invasions with the public and getting them involved with the enormous challenge of managing these ecological changes.
Theresa is taking a rather novel approach to this in her research, directly using knowledge of the subject among the public and stakeholders. For example, part of the study involves interviewing anglers who have spotted flounders in different circumstances.
"When I was doing my Master's project, which was also about the European flounder, I met a lot of people, anglers in particular, who were not only very interested in the subject but also knew a lot about it. My conversations with those people inspired me to continue this research for my PhD in order to improve our understanding of a species that is not native to Icelandic waters."
This aligns with the University's obligations as described in UI26, which specifically states that UI will lead informed debates and act as a force for positive societal development. Part of Theresa's project is about directly encouraging the public to influence processes related to invasive species in Icelandic waters.
"Recent international studies underline the threat of biological invasions and the importance of researching them and getting them under control. This research is also relevant to several UN Sustainable Development Goals, in particular 14 and 15, since biological invasions present a threat to biodiversity both in water and on land," says Theresa.
A little researched species in the Icelandic biosphere
Theresa says that when she first started looking at the European flounder, it immediately became apparent that very little research had been conducted on the species, even though it has evidently established itself very rapidly in Icelandic waters.
The flounder is a demersal fish and lives from the shoreline down to a depth of about 100 metres, although it also moves up into rivers and lakes as previously stated. The arrival of flounders in rivers and lakes is not particularly welcome, since research shows that in that environment they will eat juvenile salmon and trout, as well as sticklebacks. At sea, the flounder's diet is varied and includes shellfish, amphipods, lugworms, sandeels and dead fish. However, more research is needed in this area, since the species arrived so recently.
How do non-native species become established in a new ecosystem?
Theresa explains that her plan for her doctoral research is to uncover new knowledge about the European flounder, but also to find answers to general questions about how non-native species become established in Iceland's coastal waters. She says that the research has yielded some interesting results over the last four years. Part of the project is about developing, assessing and understanding communication about the species between stakeholders.
"We have collected information about the probable origin of the flounder and its habitats here in Iceland. With help from anglers, we also gained a better understanding of the societal impact of this species."
Important to share new knowledge with the public
Theresa explains that this study and others like it are important in order to gain a better understanding of the environment we live in and how we can handle any problems or challenges that arise.
"But I believe it is equally important to make this knowledge accessible to the public. Recent international studies underline the threat of biological invasions and the importance of researching them and getting them under control. This research is also relevant to several UN Sustainable Development Goals, in particular 14 and 15, since biological invasions present a threat to biodiversity both in water and on land."
Theresa hopes that her research will raise awareness of biological invasions in Iceland.
"But I also hope to do my bit to break down barriers between scientists and the public by actively sharing my research and getting the public involved."
