Water Meets Land – Coastal Hydrography and Geology

The Wadden Sea forms a transitional habitat between land and sea. High tidal amplitudes, shallow water depths, strong winds, and rivers discharge create a unique and very complex hydrography of the area. The flowing water is in constant interaction with vast quantities of unconsolidated sediment and together they create complex patterns of geomorphological features and sedimentary structures. This Wadden Sea boasts some of the largest continuous intertidal (falls dry during low tide and is covered by water during high tide) sand and mud flats in the world and the dynamic interactions of sediment and water create and maintain the base for valuable ecosystems.

In the field of coastal geology, our research focuses on the mapping and surveying of geomorphology, sediment distribution and habitat properties in the Wadden Sea and in the coastal North Sea. To make area-based statements about the sediment properties of the seabed, we employ ship-based methodological approaches based on the acoustic backscatter properties of the seabed. With the help of these sonar-based measurements, bedforms can be assessed, and biogenic surface structures, such as mussel beds and subtidal rocky reefs, can be examined. Grab samples and video analyses are used to analyze and characterize habitats and the distribution of organisms on the seabed. We investigate both the natural processes that influence seafloor morphology and sediment dynamics and anthropogenic influences, such as the use of bottom-contact fishing gear.

Acoustic methods further allow us to look beneath the seabed and give us the opportunity to study the historical development of the very young North Sea on geological time scales. These methods help to visualize and analyze glacial surfaces and ancient river courses that are now covered by water and sand. In addition, we use sedimentary archives to gain a better understanding of the Holocene formation and long-term evolution of coastal areas.

How exactly habitats and sediment structures form is highly dependent on the ocean dynamics in the coastal area. Ocean modeling at the Wadden Sea Station involves creating computer-based representations of the ocean's physical processes. We use models to predict water currents, temperature, salinity, and turbidity distributions in time and space. The ocean models also allow us to investigate the dispersal patterns of oyster larvae in restoration areas and the impacts of sea-level rise on the coastal areas of the Wadden Sea and the associated changes in habitats. Coastal ocean modeling is also closely linked to global ocean modeling, which considers the coast as a transition zone between land and the deep ocean.

At the Wadden Sea Station, we pay particular attention to studying the complex interplay between hydrography, sediment dynamics, and the ecosystem, which represent coupled processes. Most of our investigations focus on the Sylt-Rømø Bight, where our station is located and where long-term measurements are available. The bight is a shallow, tidally-driven system with an average water depth of only 4 meters at high tide. In spring, for example, microscopic algae grow in the water column and cause widespread algal blooms. This phytoplankton is an important food source for mussel reefs and the entire aquatic food web. The spring bloom of phytoplankton often leads to a depletion of nutrients in the water column. When the phytoplankton die, they sink to the seabed, and the decomposition process returns the nutrients to the water column. In the Sylt-Rømø Bight, most of the primary production occurs on the seabed and in sediments of intertidal zone. At the Wadden Sea Station, we also investigate how climate-induced changes in the tidal cycle and light availability would affect the activity and composition of microorganisms in the sediment. The overarching goals include a better understanding of the ecosystem services currently provided by the Wadden Sea, as well as the ecosystem alterations that could result from sea-level rise and accompanying changes in water turbidity and current regimes.

Physical geographer Dr Lasse Sander, expert on the topic of landscape development in the Holocene

Marine geophysicist Dr Jasper Hoffmann, expert on the morphological structures of the seabed

Bioscientist Dr Vera Sidorenko, expert on the topic of numerical ocean modelling

Marine biologist Dr Nicola Camillini, expert on coastal ecology and benthic biogeochemistry

Our research focuses on the structure and function of coastal ecosystems in connection with changes in environmental conditions. Here, you can learn more about our core research topics and how climate change will impact our ecosystem.