The importance of manganese nodules for the life cycle of deep sea incirrate octopi

felix.janssen [ at ]


Leg SO242/2 of an RV SONNE expedition to the DISturbance and reCOLonization (DISCOL) area in the manganese nodule ecosystem area of the Peruvian Basin in the framework of JPI Oceans program ‘Ecological aspects of deep-sea mining’ and MIDAS investigated the faunal and biogeochemical response and recovery to both recent (~5 weeks prior) and historical (~26 yrs prior) nodule removal and seafloor disturbances. Recently published by MIDAS partners, epifauna studies conducted within the Clarion Clipperton Fracture Zone (CCZ) as part of the same projects have shown the potential importance of manganese nodules as suitable hard substrate ‘islands’ onto which stalked fauna, such as deep sea sponges and crinoids, can settle and develop (Vanreusel et al., 2016). At the DISCOL site, 27 deep sea incirrate octopi were observed actively feeding around the edges of Manganese nodules at depths of approx. 4100 m, using crevices between nodules as sites of refuge, and in two instances brooding eggs directly onto the stalks of dead deep sea fauna. Interestingly, no incirrate octopi were observed during any of the recent MIDAS / JPI Oceans cruises to the CCZ, Observed individuals represent at least two species, with several being identified as Vulcanoctopus sp. The majority appear to belong to the recently observed ‘Casper’ species, recorded by Remote Operated Vehicles from several locations within the Hawaiian archipelago, and as yet, undescribed. Together with the recent Hawaiian observations, these new data increase the depth range of incirrate octopi by several hundreds of meters. Additionally they represent the first observations of incirrate octopi using other fauna as a brooding substrate. Though the knock-on impacts on stalk supported small megafauna communities has been a known consideration for several decades (though better understood following MIDAS and JPI Oceans investigations) the potential impacts on larger semi-pelagic mobile fauna such as octopi has not been considered to date. In this study we show that potentially the loss of nodules will have direct impacts on these larger megafauna. Tantalisingly, the observations of the incirrate octopi in the Hawaiian archipelago were made in areas also abundant in stalked fauna. Survey dives within these manganese crust rich regions of seafloor covered considerably less area than the DISCOL work carried out during SO242/2, and therefore there is the potentiality that stalks in these commercially interesting ecosystems represent habitat resources at risk from mining activities.

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Conference (Poster)
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EU FP7 MIDAS final meeting, 03 Oct 2016 - 07 Oct 2016, Gent, Belgium.
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Purser, A. , Marcon, Y. , Janssen, F. , Hoving, H. J. T. , Piatkowski, U. , Vecchione, M. , Eason, D. and Boetius, A. (2016): The importance of manganese nodules for the life cycle of deep sea incirrate octopi , EU FP7 MIDAS final meeting, Gent, Belgium, 3 October 2016 - 7 October 2016 .

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