Southern Indian Ocean Seamounts, Cruise Report
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Final cruise report: Southern Indian Ocean Seamounts 2009 Cruise Report “Dr. Fridtjof Nansen” Southern Indian Ocean Seamounts (IUCN/ GEF/ UNDP/ ZSL/ ASCLME/ NERC/ EAF Nansen Project/ ECOMAR/ ACEP 2009 Cruise 410) 12th November – 19th December, 2009 By A.D. Rogers1, O. Alvheim2, E. Bemanaja3, D. Benivary4, P.H. Boersch-Supan1,5, T. Bornman6, R. Cedras7, N. Du Plessis8, S. Gotheil9, A. Hoines2, K. Kemp1, J. Kristiansen2, T. Letessier5, V. Mangar10, N. Mazungula6, T. Mørk2, P. Pinet11, J. Read12, T. Sonnekus6 1)Institute of Zoology, Zoological Society of London, Regent’s Park, London, NW1 4RY, United Kingdom. 2) Institute of Marine Research, P.O. Box 1870 Nordnes, 5817 Bergen, Norway. 3) IHSM Institut Halieutique et des Sciences Marines, Madagascar. 4) University of Tuléar, Madagascar. 5) Pelagic Ecology Research Group, Scottish Oceans Institute, University of St Andrews, Fife, KY16 8LB, United Kingdom. 6) South African Institute for Aquatic Biodiversity, Pbag 1015, Grahamstown 6140, South Africa. 7) University of the Western Cape, Dept. of Biodiversity & Conservation Biology, Private Bag X17, Bellville 7535, South Africa. 8) University of Cape Town, Department of Oceanography, Rondebosch 7701, Cape Town, South Africa. 9) International Union for Conservation of Nature (IUCN), Rue Mauvernay 28, 1196 Gland, Switzerland. 10) Albion Fisheries Research Centre, Mauritius. 11) ECOMAR Laboratory, Université de La Réunion, 15 avenue René Cassin, Saint Denis, 97715, France. 12) National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom. 1 Final cruise report: Southern Indian Ocean Seamounts 2009 Contents 1.0 The South West Indian Ocean ........................................................................................................... 6 1.1 Regional fisheries management arrangements....................................................................................... 6 1.2 Fisheries for deep-sea species in the South West Indian Ocean ............................................................. 8 1.3 Protection of benthic marine ecosystems ............................................................................................... 9 1.4 The Seamounts Project .......................................................................................................................... 10 1.5 The Environmental Setting of the Madagascar and South West Indian Ocean Ridges ......................... 12 1.5.1 Geology ........................................................................................................................................... 12 1.5.2 Oceanography ................................................................................................................................ 14 1.5.3 Prior knowledge on the biology of the Madagascar and South West Indian Ocean Ridges .......... 17 2.0 Cruise track and daily events........................................................................................................... 21 3.0 Multibeam bathymetry of the investigated seamounts .................................................................... 28 3.1 The seabed mapping system ................................................................................................................. 28 3.2 Bathymetry of the seamounts ............................................................................................................... 28 3.2.1 Atlantis Bank ................................................................................................................................... 28 3.2.2 Sapmer Bank ................................................................................................................................... 31 3.2.3 “Middle of What” Seamount .......................................................................................................... 33 3.2.4 Coral Seamount .............................................................................................................................. 35 3.2.5 Melville Bank .................................................................................................................................. 37 3.2.6 Unnamed Seamount, Madagascar Ridge ....................................................................................... 39 4.0 Physical Oceanography ................................................................................................................... 41 4.1 Objectives .............................................................................................................................................. 41 4.2 Plan ........................................................................................................................................................ 41 4.3 Equipment ............................................................................................................................................. 42 4.4 Data processing and calibration ............................................................................................................ 44 4.5 Results ................................................................................................................................................... 48 4.6 Conclusions ............................................................................................................................................ 52 5.0 Phytoplankton, nutrients and POM ................................................................................................. 53 5.1 Phytoplankton ....................................................................................................................................... 54 5.1.1 Materials and methods .................................................................................................................. 54 5.1.2 Preliminary results .......................................................................................................................... 55 5.2 Nutrients ................................................................................................................................................ 56 5.2.1 Materials and methods .................................................................................................................. 56 2 Final cruise report: Southern Indian Ocean Seamounts 2009 5.2.2 Preliminary results .......................................................................................................................... 56 5.3 Particulate Organic Matter (POM) ........................................................................................................ 56 5.3.1 Materials and methods .................................................................................................................. 56 5.3.2 Preliminary results .......................................................................................................................... 57 6.0 Mesozooplankton and micronekton sampling ................................................................................. 58 6.1 Summary ................................................................................................................................................ 58 6.2 Materials and methods ......................................................................................................................... 58 6.2.1 Pelagic Sampling ............................................................................................................................. 58 6.2.2 Multinet protocol (Stratified) ......................................................................................................... 60 6.2.3 Multinet protocol (Fmax) ............................................................................................................... 61 6.2.4 Oblique bongo protocol .................................................................................................................. 61 6.2.5 Aakratrawl Crustaceans .................................................................................................................. 61 6.3 Results ................................................................................................................................................... 62 6.3.1 Mesozooplankton ........................................................................................................................... 62 6.3.2 Aakra trawl Crustaceans ................................................................................................................. 64 6.4 Sampling limitations .............................................................................................................................. 66 6.5 Research intentions/discussion ............................................................................................................. 67 7.0 Micronekton and nekton sampling .................................................................................................. 69 7.1 Summary ................................................................................................................................................ 69 7.2 Methods ................................................................................................................................................ 70 7.2.1 Ǻkra trawl fishing ............................................................................................................................ 70 7.2.2 Ǻkra trawl catch-processing ..........................................................................................................