Oldenburg scientists have created 120 square metres of artificial islands in the Spiekeroog mudflats. The globally unique large-scale project provides new insights for biodiversity research.
They can be seen from the ferry to Spiekeroog - in the middle of the mudflats: twelve large metal cages made of heavy ship steel. They look like large, silver fortresses that defy water, weather and wind. But they are artificial islands. Artificial islands with which researchers at the University of Oldenburg are breaking new scientific ground. The large-scale, globally unique research project is a co-operation with the Wadden Sea National Park and the University of Göttingen. Its aim is to find out how plants and animals colonise islands in the Wadden Sea. And how biodiversity changes with rising sea levels.
"We know that islands are formed by the accumulation of sediments," explains landscape ecologist Prof Dr Michael Kleyer from the Institute of Biology and Environmental Sciences (IBU). "But we hardly know anything about how colonisation by plants and animals takes place when new salt marshes are created far away from existing salt marshes." To find out more, Kleyer and a team led by scientist Dr Thorsten Balke installed the artificial islands in the Spiekeroog mudflats last summer. Back-breaking work.
Ten students and young scientists worked for eight weeks to anchor the heavy metal cages in the mudflats. They shovelled sediment, built a foundation from a geotextile, a kind of weather-resistant carpet, to prevent the heavy cages from sinking into the mudflats. They installed measuring devices to record the salt content and temperature. Step by step, an open-air laboratory was created that is unique in the world - an island system in fast motion: "We have shortened the entire process of creating an island in the mudflats in one go," laughs Balke. More than 120 square metres of artificial island now document how a terrestrial ecosystem develops from a marine one.
Eight doctoral candidates and several postdocs from Oldenburg and Göttingen are researching the large-scale experiment. They are organised in the "BEFmate" project (Biodiversity effects on ecosystem functioning across marine and terrestrial ecosystems), which is funded by the state government of Lower Saxony with three million euros. The spokesperson is the Oldenburg marine scientist and Director of the Institute of Chemistry and Biology of the Marine Environment (ICBM), Prof Dr Helmut Hillebrand.
Spiekeroog, the most natural of the East Frisian islands, offers ideal research conditions for this extraordinary project. The ICBM's "BioGeoChemistry of the Wadden Sea" research group has been present there for years and has been collecting precise measurement data on the physical, chemical and biological properties of the incoming and outgoing seawater using the "yellow measuring pole" since 2002. The scientists were therefore very familiar with the area. In addition, the university recently opened a number of laboratories and flats for scientists in the Wittbülten National Park House, where Kleyer and his team were able to stay during the construction work. "Spiekeroog is one of the tourist hotspots in Germany - accommodation for scientists has always been extremely expensive. Research projects often failed because of this," reports Kleyer. Wittbülten counteracts this shortcoming.
Several hundred metres separate the experimental islands from Spiekeroog. Plants and animals that settle there must first overcome this barrier. Which plant will find its home on the new island first, which animal? How do they interact with each other, do they influence each other? Will they be displaced by plants or animals that settle on the island later? What significance do they have for the new ecosystem? How much new biomass is created by the colonisation process and how does a new food web develop? To answer these questions, the scientists hike to the islands almost daily in summer at low tide, carry out measurement campaigns and record the plants and animals that settle there. A lengthy process. The research project is scheduled to run for three years - although the scientists are aiming to extend it to twelve years.
The experts have planted six of the artificial islands in advance. With plants that occur in the Spiekeroog salt marshes: Andel grass, salt marsh grass, sea lavender. Different height levels of the artificial islands simulate the flooding zones of the salt marshes, ensuring that the plants are exposed to the salt water of the North Sea at different frequencies. In this way, the scientists analyse the rise in sea level and its effects on the vegetation. "We put the plants in the salt marshes on our artificial islands under targeted pressure to see how they cope with this 'stress', how they cope with the changed environmental conditions," explains Kleyer. How long does it take before they die or are replaced by more resistant plants? How strong is their resistance? These are questions that urgently need to be answered given the current relative rise in sea level of up to four millimetres per year.
At the beginning of the research project, however, there was a bitter setback. A setback that impressively illustrates how unique this project is. The research group installed the first artificial islands in the mudflats back in summer 2013. Lighter metal baskets withstood the forces of nature until hurricane Xaver hit the artificial islands at the beginning of December - with wind force 13. Xaver easily destroyed the complex structures. "There is no comparable project in biodiversity and ecology research in which colonisable islands were built in a coastal system with sea, storm surges and waves," explains Balke. "We first had to gain experience," adds Kleyer. "We are the pioneers, we can't visit and study existing experimental set-ups or even improve on them."
The close co-operation with the Wadden Sea National Park also shows how outstanding this research is. Previously, the administration had a strict policy: no experiments in the Wadden Sea. The research carried out by the Oldenburg scientists is an exception in the highly protected UNESCO World Heritage Site - an absolute vote of confidence and an appreciation of Oldenburg's research.