KArstic submarine fReshwater Springs

Projektbeschreibung

Unterwasserquellen in Karstgebieten

Durch submarine Grundwasseraustritte werden Nährstoffe in Küstengebiete eingetragen, was für die Ökosysteme nicht ohne Folgen bleibt. In Karstsystemen stammen Grundwasseraustritte hauptsächlich aus submarinen Quellen, die schwer zu lokalisieren sind, aber in sehr flachen Gebieten an Veränderungen der Meeresoberfläche zu erkennen sind. Das EU-finanzierte Projekt KARST wird die Verbreitung submariner Quellen und ihren Einfluss auf lokale Ökosysteme in Karstgebieten ermitteln und charakterisieren. Gleichzeitig werden in flachen, weniger als 5 m tiefen Küstengebieten mit unbemannten Luftfahrzeugen biologische Lebensräume und Anomalien der Meeresoberfläche im Zusammenhang mit submarinen Quellen bildlich erfasst und in Beziehung zueinander gesetzt. Mit einem neu entwickelten geoelektrischen System in Kombination mit bildgebenden Mehrstrahl-Verfahren wird das physikalische Verhalten der Wassersäule und die Verbreitung von Seegras nahe tiefer gelegener Quellen erkundet.

Ziel

Submarine groundwater discharge (SGD) is the flow of fresh or recirculated groundwater into the ocean. This process introduces substantial amounts of nutrients to coastal areas, which significantly influences ecological systems. In karstic settings SGD dominantly occurs from submarine springs that manifest as point source discharge sites. Their identification generally relies on sea-surface changes (e.g. visual sea-surface anomalies or changes in sea-surface temperature) and is therefore confined to shallow areas with high discharge rates. As a result the distribution of offshore freshwater springs in karstic environments, which is crucial for determining the architecture and dissemination of offshore groundwater systems, is usually poorly constrained. Similarly, the negative effects of groundwater springs on seagrass diversity and biomass have been investigated at individual springs but have not been characterised over larger areas. This proposal focuses on the identification, characterisation and distribution of submarine springs and their influence on local ecosystems in karstic environments. KARST will make use of state of the art geophysical and remote sensing techniques for optimal imaging at various depths. In the shallow coastal areas (<~5 m), unmanned aerial vehicles equipped with multispectral and thermal infrared cameras will be used to simultaneously image and correlate biological habitats and sea-surface anomalies related to submarine springs. In deeper areas, a newly developed geoelectric system from the University of Kiel in combination with multibeam water column imaging techniques will provide insight into the physical behaviour of the water column as well as salinity and seagrass distribution around springs. All techniques will be guided by biological sampling and flow rate measurements, which will not only help to determine the ecological effects of SGD but will also provide valuable knowledge on the architecture of karstic groundwater systems.