aus dem MARUM und dem Fachbereich Geowissenschaften der ...

MARIA S. MERIAN-Berichte, Cruise 20, Leg 4, Bridgetown – Freeport, 15.3.2012 – 7.4.2012
seafloor – as to expect under such vigorous current conditions – high quality video material
could be recorded, showing an amazing CWC ecosystem. The detailed MBES mapping reveal
that these CWC ecosystems are developed on V-shaped ridges - rather than on mounds - that
stretch over several hundreds of metres (Fig. 6.1). The ridges are embedded between a steep
slope towards the Campeche Bank in the west and a major drift sediment body in the east (as
already described by Hübscher et al., 2010). They follow the main current direction towards the
NW. In addition, a second orientation becomes evident with ridges stretching towards the NE.
Often both directions are merged thereby forming the V-shaped ridges pointing with the tip to
the NW. During the ROV dives, it has been observed that the morphology of these ridges is
mostly rather steep with differences between ridge crests and bases of up to 30 m. Living corals
occur at the highest parts, followed downslope by a zone of coral rubble and by plain soft
sediments in the lower parts of the ridges and in between them. An overview map of the
Campeche Bank working area with all the sampling stations is given in Fig. 6.1.
Fig. 6.1 Overview map of the Campeche Bank working area showing all sampling sites and ROV dive tracks
(GeoB station Numbers are indicated) conducted during cruise MSM20-4.
6.1.2. Campeche Bank: The Water Column Structure
(Christian Dullo, Thorsten Garlichs, Silke Glogowski)
In the Yucatan Strait (GeoB 16303), the uppermost 70 m of the water column is characterized by
the occurrence of relatively fresh water with salinities less than 35.89. This shallow water mass
is called Caribbean Water (CW) and believed to be a mixture of the Amazon and Orinoco River
outflow, as well as North Atlantic surface water. A salinity maximum (about 36.9) between 100
to 135 m has been measured and is characteristic for the Subtropical Under Water (SUW). This
water mass is formed in the central tropical Atlantic, where evaporation exceeds precipitation. It
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