FWO MINIMOUND Project: Using Cold-water coral mini-mounds as analogue for giant mound growth: assessment of environmental drivers and anthropogenic impact Cold-water corals (CWC) are found along the entire north-eastern Atlantic Margin from Norway to the Gulf of Cadiz. In the Porcupine Seabight, these coral reefs (mainly Lophelia pertusa and Madrepora oculata) accumulate into large mounds of up to 250m high (e.g. Challenger Mound), which have been well studied over the past two decades (Roberts et al., 2006). The detailed mechanism of the start-up phase of such large CWC mounds is however not yet fully understood. Therefore, it is essential to study analogues of these stages that are not well recorded in larger mounds. The FWO MINIMOUND project (2013-2016) aims to investigate the initiation, growth and demise of “small” CWC mounds and to determine the role of climatic and hydrocarbon-seepage related processes as well as anthropogenic impact. This high-resolution multidisciplinary study will focus on three “minimound” provinces along the Biscay continental margin: (1) the Explorer and Dangeard Canyons on the Celtic Margin (Fig. 1; Stewart et al., 2013), (2) the Guilvinec Canyon on the Armorican Margin (De Mol et al., 2011) and (3) the Upper Ferrol Canyon on the Cantabrian Margin (Fig. 1). These minimounds are fossil (9.7 ka BP) and occur at relative shallow depth on the interface between the Eastern North Atlantic Central Water (ENACW) and the Mediterranean Outflow Water (MOW). Contrastingly, most present-day living CWC reef habitats dwell in the deeper MOW depth range, relying on the density and dynamics of this water mass for their food supply.   The objectives of the project are threefold: (1) the establishment of a chronostratigraphic framework and the reconstruction of palaeoceanographic changes over the last 15.000 years in order to determine the impact of glacial to interglacial climate change on the ENACW-MOW interface and the CWC habitats (Frank et al., 2011); (2) the minimound province at the Upper Ferrol Canyon shows a close association with hydrocarbon-seepage (pockmarks) which allows to assess the role of hydrocarbon related processes in CWC mound formation; (3) the potential impact of anthropogenic fisheries activities will be investigated. These objectives will be tackled through a coupled geophysical, sedimentological and integrative approach, including the palaeoceanographic and biogeochemical study of sediment cores in cooperation with the BGS (UK), LSCE (Gif-sur-Yvette, France), IFREMER (France), IGME (Spain) and IEO (Spain). This Belgica2015/15 cruise is the second campaign of the project and it aims to sample both “on-mound” as “off-mound” sites by means of a 4.5 m vibrocorer (Supplied by the British Geological Survey, BGS). The target site are located on the upper slopes of the Ferrol Canyon (Cantabrian margin, Spanish EEZ) and the Guilvinec Canyon (Armorican margin, French EEZ) between 200 and 600 m water depth. In each sector, a minimum of 3 days of activities will be scheduled. In case of bad weather on 1 sector, the program will be revised towards the other sector. With respect to the size of these mounds, the coring location of the vibrocorer will be steered by means of am IXSEA USBL GAPS system. During night-time, the seafloor will be visually characterized using a small and light-weight camera dropframe (University of Plymouth).

The northern "Contourite Depositional System" located within the Gulf of Cadiz is well studied and was drilled last year during IODP expedition 339. We aim to acquire 3 additional seismic lines over these drill sites towards the shallow shelf for sequence stratigraphic studies and acquire a connection profile to the southern part of the Gulf, along the Moroccan margin. The research along the Moroccan margin builds upon previous investigations (R/V Belgica 2002, 2005, 2008) and will focus on smaller current-related deposits in order to fully understand the hydro- and sediment dynamic picture of this area during the past 2.4 Ma. This will allow to better assess the evolution of cold-water coral ecosystems. This will be achieved by gathering additional seismic lines and perform hydrographic measurements. In the second half of June, several cores will be gathered from the southern part of the Gulf of Cadiz with the R/V Marion Dufresne. In order to visualize the subsurface of these core sites, 6 seismic profiles will be gathered, connecting these core sites.

This cruise aims to investigate the seismic stratigraphy and palaeoceanographic evolution of the Le Danois contourite depositional system (Van Rooij et al., 2010), at several locations in the Le Danois "intraslope basin". Previous research (R/V Belgica in 2004, among others) has highlighted a significant correlation with the Cadiz CDS, suggesting a nearly simultaneous control by the Mediterranean Outflow Water since the Early Pliocene. As such, the Le Danois CDS is the only location in the Bay of Biscay where high-resolution climate change (e.g. bottom currents) may be recorded in a continuous way. It will assist in better constrain the role of the MOW in the thermohaline circulation system. Therefore, this large-scale sediment body is an ideal target for (a) investigating the MOW palaeoceanography within the NE Atlantic basin and (b) a palaeoclimatologic reconstruction of the Cantabrian margin. The main objective of this campaign is to acquire additional geophysical data which will give more insight in the construction and 3D evolution of this sedimentary deposit. This campaign will be executed in close cooperation with the Proyecto Coordinado CONTOURIBER (CTM 2008-06399-C04/MAR), with invited researchers from Spanish research institutes. More specifically, R/V Belgica ST1118a aims to perform: 1.High-resolution single channel sparker seismic profiling: investigation of the stratigraphic framework and the sedimentary environment in the western part of the intraslope basin between the Vizco High (west), the Lastras canyon system (east), Le Danois bank (north) and the Asturias slope (south). This will mainly focus on the lateral and temporal evolution of Le Danois drift and the Gijon drift and their interaction. The location of these profiles is determined based on industrial multichannel airgun profiles, in order to compare seismic methods with different penetration depths and seismic resolutions. We are very grateful to TGS-NOPEC for allowing us to use a large unpublished data set of seismic records from the Cantabrian Sea. 2.Hydrography: at specific sites in the intraslope basin, CTD casts will aim to better map the presence and behavior of the Mediterranean Outflow Water within the main elements of the Gijon and Le Danois drifts. The newly acquired Seapoint turbidity sensor will be able to indicate regions of active sediment transport within the Le Danois CDS. Multibeam bathymetry with the Belgica EM1002 will be only be used as a backup in case of spare time or failure of the other methods. The proponents are aware of the Marine Protected Area status of the Le Danois Bank, and will be vigilant to respect the guidelines of conducting scientific research. In order to ensure vigilance with respect to marine mammals, a team of whale watchers of MUMM, ULg (Belgium), CRMM (France) and OCEAMM (France) will be participating. This part of the campaign is a cooperation between the RCMG (UGent), the University of Vigo, the Geological Survey of Spain (IGME), the Spanish Oceanographic Institute (IEO), the Spanish Institute of Marine Sciences (CMIMA-CSIC) and the University of Cádiz.