Experimental settlement study in the Eastern Mediterranean deep sea (Ionian Sea)

In this study, we examined the potential growth of organisms on different artificial substrates on a bathymetrical transect in the deepest part of the Mediterranean Sea in the Ionian Sea (Nestor site) after long-term deployment. As this area is characterized by small temperature and salinity fluctuations between the deep-water layers, it is an ideal study site to determine variations in the community structure of settled organisms with depth and material type. Four new experimental platforms (GKSS prototype), each in one depth (4500, 3500, 2500 and 1500 m) and with five artificial substrates (titanium, aluminum, glass, limestone and shale) in two orientations (horizontal and vertical) were deployed for 155 days at the study site. After retrieval all substrates in every depth were visually inspected. The absence of macrofouling was evident and only a loosely adhered biofilm could be observed. Scanning Electron Microscopy revealed the presence of substrate attached bacteria although a direct counting could not be achieved. With the use of molecular-biological approaches substrate attached bacteria in biofilms could be detected at all depths, substrates and both orientations.