The "insect hotel" in the sea

Students at the interdisciplinary Master School of Marine Sciences aim to bring new life to built-up coastal waters through the Living Sea Walls project.

Underwater: a piece of concrete overgrown with plants
© Nikolas Linke

After just a short time underwater, the tiles were covered in algae, barnacles and mussels.

Algae, seaweed, mussels and various microorganisms: the 30 concrete tiles placed in the Kiel Fjord by the Kiel University students are bustling with life – to the delight of the interdisciplinary team of marine geoscientists and biologists involved in the Living Sea Walls project. In her Bachelor's thesis, biology student Lena Böttcher is now examining in greater detail what exactly has taken up residence and how great the biological diversity is on these tiles.

Developing solutions and initiatives for greater sustainability in the way we treat the ocean was the main topic of an interdisciplinary teaching module offered by the Master School of Marine Sciences (iMSMS) at Kiel University. This module was led by oceanographer Professor Martin Visbeck and marine ecologist Dr Franziska Werner. It gave rise to a project dealing with the question of how, given the major global loss of natural habitats in coastal waters resulting from over-development of port facilities, eco-engineering can be used to re-establish more animal and plant life and more biodiversity and, by doing so, improve water quality at the same time. In semester 2020/2021, marine geoscientists Luisa Franzen and Annabel Payne and Philosophy of Economics and Environmental Ethics students Rika Maletzky, Paulina Valente and Tamara Friebe examined this topic and began a pilot study on it. Biologist Lena Böttcher got involved later on.

This was their plan: like the World Harbour Project (WHP) by the Sydney Institute of Marine Science (SIMS), the student team, working in collaboration with the GEOMAR Helmholtz Centre for Ocean Research Kiel, installed a total of 30 concrete tiles with and without structured surfaces at two sites in the Kiel Fjord. "In the Pacific Ocean, the tiles work really well. They are like an underwater insect hotel," explained Australian Annabel Payne, who brought the idea for the project with her from Sydney to Kiel. But will the concrete tiles also be accepted in the brackish water of the Baltic Sea, where there are no tides and where the flora and fauna is completely different to those prevalent off the coasts of Australia? And what type of tile is better suited to form a new habitat for algae, mussels and such like?

Concrete tiles lined up on a footbridge
© Lena Böttcher

A total of 30 concrete tiles with and without structured surfaces were installed underwater for the study.

Lena Böttcher is working intensively on evaluating the study: the biology student is writing her Bachelor's thesis on the project and scrutinised the tiles in the Kiel Fjord after three and six months. "The first question of whether the tiles would also be colonised in the Baltic Sea can be answered with a resounding yes," said Böttcher. In fact, both variations of tile – the smooth and the structured ones – are covered in algae, with mussels and barnacles attached. She even found animals like starfish and crabs – they have accepted the new underwater habitat. Böttcher is attempting to find out which variation functioned better through meticulous and microscopic precision work. "I identify the different species of algae, barnacles and mussels as well as mobile grazers like microcrustaceans and isopods and determine the quantity and quality of the tile colony as a whole." The challenge here being that "The selected examination period was relatively short so the plants were still very small," said Böttcher. "From the first pioneer plants to an underwater rainforest full of different species takes at least a year or more," added Annabel Payne.

For this reason, the work is ongoing for marine geoscientist Payne, who after completing her Master’s at Kiel University is now writing her doctoral thesis in Zurich. Together with Kiel-based Master's students of geosciences Luisa Franzen and Lena Jebasinski as well as Christian Pape, expert in sustainability and carbon capture technology, Payne is in the process of founding a company – the start-up called Habitile. The first objective is to install a further 30 to 40 tiles in the Baltic Sea, in the North Sea and in the Mediterranean for at least a year in order to obtain more comparable results on colonisation. "In the long term we hope to be able to install permanent concrete tiles in ports," said Payne. To give a piece of habitat back to nature.

Author: Jennifer Ruske