Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Poseidon	POS466	02.03.2014 - 18.03.2014	MAPS	Madeira Abyssal Plain North Atlantic Ocean

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
George Kai Horst	Forschungsinstitut Senckenberg, Abt. Meeresgeologie/biologie, Wilhelmshaven	Las Palmas	Funchal

Ziel der Reise / Objectives of Cruise:

Background of the research project "Madeira Archipelago Pre-seamount Stages" (MAPS) and of POSEIDON cruise POS466 is the question, whether submarine island-seamount-chains like the Madeira Hot Spot Track (MHST) that show the same origin but different ages, do reflect that age gradient faunistically. Moreover it was planned to investigate if the meiofauna assemblages of seamount summits, respectively of the littoral of islands of the MHST form sub-populations of one overall meta-population, and if dispersal and/or isolation mechanisms may be recognizable along the MHST. That should help understanding if seamounts and islands function as staging posts, thus supporting the dispersal of marine meiobenthos, or if they in contrast act as isolated entities, rather benefitting the evolution of exclusive faunas with high percentage of endemism. In that context, a second gradient beside the age gradient and referring to the influence of terrigenous input into the littoral and sublittoral along the chain of MHST may be of essential relevance. Whereas such input of organic and anorganic terrigenous material is high at Madeira, it is supposed to decrease considerably at Porto Santo compared with marine influence. At both seamounts Ampere and Seine the terrigenous signal diminishes down to an eolian dust input. The change from a lithoclastic-terrigenous marked shelf sedimentation towards an autochthonous production of carbonates should be reflected in the composition of the phytoplankton community (particularly of the calcareous nanoplankton) as well as of the (meio)benthic associations of the corresponding islands and seamounts. The aimed census of the phytoplankton may enable detecting a possible influence of islands on the composition and structure of the respective species assemblages; moreover, it may allow comparing possible impacts on species composition caused by seamounts respectively islands. The Great Meteor Seamount that is located outside the MHST, and whose plateau meanwhile sunk below the photic zone, may be a good object for further comparison. MAPS is the first project considering the above mentioned aspects, and it may contribute remarkably for our comprehension of the role of seamounts for marine fauna, especially against the background of their pre-seamount stages, as exemplified by Madeira and Porto Santo. Cruise POS466 of RV POSEIDON aimed an extensive sampling of the sublittoral meiobenthos and sediment (both 50-300m depth), as well as of phytoplankton (0-150m) in the Madeira Archipelago. Moreover, several physical variables were measured throughout the water column down to 3000m depth. Altogether, 582 deployments were made at 108 stations that distributed over 22 transects around the islands of Madeira, Porto Santo, and Desertas. The following gears were deployed: van Veen grab (meiofauna), Shipek grab (sedimentology, meiofauna), plankton net (phytoplankton), underwater videocamera. Water samples were taken using Niskin bottles mounted on a rosette, which was additionally equipped with a CTD for measurement of temperature, conductivity, density (depth), oxygen, and fluorescence. Despite an initial lag of time due to a delayed delivery of the container with scientific equipment, the cruise was absolutely successful, providing all required samples (and even more)! Apart from the favourable weather conditions it was the amazing and phantastic collaboration of scientists and the ship's crew that lead to such successful results! On behalf of all scientists I express my deepest gratitude to captain Matthias Gunther and to all crew members of POSEIDON for the great cooperation and the huge support!

Messungen / Measurements