Main objective: MapGES 2023 is the continuation of our long-term strategy to map deep-sea biodiversity and identify Vulnerable Marine Ecosystems (VMEs) in the Azores using the Azor drift-cam imagery system. As in other MapGES cruises, the objectives were to (i) map benthic communities inhabiting unexplored seamounts, ridges, and island slopes, (ii) identify new areas that fit the FAO Vulnerable Marine Ecosystem definition; and (iii) determine distribution patterns of deep-sea benthic biodiversity in the Azores. The results of this cruise added to the previous contributions to identify the environmental drivers that determine the spatial distribution of deep-sea benthic biodiversity in the Azores. It also provides valuable information in the context of Good Environmental Status (GES), Marine Spatial Planning (MSP) and new insights on how to sustainably manage deep-sea ecosystems.

Methodology: We performed several underwater video transects along the seafloor with the Azor drift-cam, a low-cost drifting camera system designed and developed at IMAR & Okeanos (University of the Azores), which allows the recording of high-quality underwater video images of the seabed down to 1000 m depth. The system was deployed from the research vessel RV Arquipélago, owned by the Government of the Azores.

Cruise summary: The MapGES 2023 RV Arquipélago cruise was composed of two Legs. In the first, we visited some unexplored areas such as the geomorphological structures around the Princesa Alice bank and the seamounts north of Graciosa (Sedlo, Borda, João Leonardes, and Gaillard) (central Azores). In the second, we also visited some unexplored areas such as the geomorphological structures of Hard Rock Café (northern of Corvo Island), Kurchatov SE (in the north mid Atlantic-ridge), Albatroz N, Ferraria N, Ferraria Mar, Sauerwein, Mar da Prata, Grande Norte (south of Faial Island), and the seamounts around Princesa Alice (Princesa Alice S, Princesa Alice SE, and De Guerne) and we revisited other geomorphological structures that needed complementary sampling efforts as, for example, Isolado, Kurchatov N, Kurchatov SW, and Mar da Prata South.

During the MapGES 2023 RV Arquipélago cruise, we performed 145 dives in 148 stations down to 1 125 m depth, and covered about 85 km of seafloor, resulting in more than 141 hours of video images. These dives were conducted in 28 different sampling areas, including 26 seamounts and 2 island slopes around the island of São Jorge. During this cruise, we explored, for the first time, some areas such as the famous Hard Rock-Café and Sedlo seamounts. Data on the benthic communities inhabiting these seamounts was lacking to complement existing information that supported the designation of these areas as Marine Protected Areas (MPA) of the Azores Marine Park (PMA).

Main achievements:

1.       Eighteen unexplored geomorphological structures in the Azores EEZ were visited, being listed in the evaluation of areas with substantial knowledge gaps.

a.       Leg1 – Sedlo W, Sedlo, Borda, São Jorge NE, Princesa Alice W (formerly part of Princesa Alice), Princesa Alice SW (formerly Alberto do Mónaco), Picos S do Princesa Alice-, plus two areas that were not listed - the Gaillard seamount and the an area West of Picos S do Princesa Alice. We also visited some areas that have already been explored but were in need of extra video data namely João Leonardes, Serreta Mar, Mar da Fortuna, and São Jorge NW.

b.       Leg 2 – Hard Rock Café, Kurchatov SE, Albatroz N, Ferraria N, Ferraria Mar, Sauerwein, Mar da Prata, Mar da Prata N, Grande Norte and one seamount around Princesa Alice (De Guerne). We also visited four areas that have already been explored but needed extra video data namely the Isolado, Kurchatov N, Kurchatov SW, and Mar da Prata S. We also visited the Perestrelo Bartolomeu area, for which some information already existed, and the Petrov area, which turned out to be deeper than what the maps indicated.

2.       During the MapGES 2023 cruise we accomplished 143 underwater video transects and the deepest dive to date performed with the Azor drift-cam, at 1 125 m depth. In total, we collected 141 hours of new underwater video footage of seabed habitats. As in previous years, the presence of some fishing lines made our deep-sea exploration challenging. After having the Azor drift-cam caught on several lines, mainly around São Miguel Island (Mar da Prata and Grande Norte seamount) and Kurchatov SE, we managed to get it free only with minor damages. This collateral fishing impact is hampering the acquisition of deep-sea biodiversity data to inform management deserve to be better quantified. Problems with the Outland lasers systems resulted in the lack of laser points the some of the images recorded.

3.       We finally explored the Sedlo seamount with the Azor drift-cam. From 2002–2005, Sedlo was the focus of a multidisciplinary EU project, OASIS (Oceanic Seamounts: An Integrated Study), which showed highly complex hydrographical patterns with anticyclonic circulation around its three summits, driven principally by Taylor column formation. This seamount was speculated to accommodate one the Azores’ most important spawning ground for orange roughies and alfonsinos.

4.       Deep-sea explorations with the Azor drift-cam contributed with supporting evidence to consider Sedlo seamount as an Essential Fish Habitat. We found areas that are home to the highly endangered deep-sea fish orange roughy Hoplostethus atlanticus and discovered that Sedlo and other neighbouring seamounts host a high number of deep-sea shark species, some of which rarely observed in the Azores. We also discovered large aggregations of the black coral Leiopathes expansa on the summit of the Sedlo W, with most specimens of relatively small sizes. This area seemed to be a good candidate for being considered a Vulnerable Marine Ecosystem and should be kept in the list of priority areas for conservation in the Azores.

5.       We also explored Borda, João Leonardes, Gaillard seamount, north of Graciosa Island. Along with Sedlo, these seamounts seem to host slightly unique deep-sea benthic communities when compared to other areas in the Azores EEZ explored so far with black corals Leiopathes expansa and Parantipathes hirondelle, the bamboo coral Acanella arbuscula, stylasterids of the genus Errina, the sea urchin Cidaris cidaris, and lamellate sponges of the genus Phakellia among others

6.       We started exploring the morphological features south of Princesa Alice peak. Most dives covered soft and mix sediments with relatively low biodiversity and abundance, although some areas hosted high densities of Narella bellissima and Narella versluysi, while others were dominated by patches of Pheronema carpenteri and other sponges (e.g., Asconema sp.). We also observed some sparse colonies of cold-water such as corals Narella versluysi, Hemicorallium niobe, H. tricolor, Acanella arbuscula, Chrysogorgya sp., cf. Leptopsammia, cf. Candidella imbricata, and Flabellum sp., and some deep-sea sponges such as cf. Regadrella, and specimens from the genus Geodia, along with some shrimps Aristaeopsis edwardsiana, sea-urchins Cidaris cidaris and deep-sea fishes such as Mora moro, Synaphobranchus kaupii, Helicolenus dactylopterus, Hoplostethus mediterraneus, Gephyroberix darwinii, Dalatias licha, and one Trachyscorpia cristulata.

7.       The Hard Rock Café seamount was finally explored with the Azor drift-cam. The hydrographic Institute had mapped this seamount in 2020 but given its location at 210 nautical miles from the natural starting point of the MapGES cruises (Horta) and its position to the north of the Azores archipelago (usually more affected by adverse weather conditions), the visit to this seamount had been postponed for a few years. After all conditions were met, the Hard Rock Café was visited. It is a geomorphological structure that, due to its characteristics, was from the first moment on the list of the first options for the expansion of the Azores Marine Park, hence the increased importance of this visit.

8.       We also visited a seamount named Petrov. This area does not yet have high-resolution bathymetry data, so we tried to prospect the area looking for a peak between 300 m and 1,000 m depth. However, after launching the Azor drift-cam in search of a shallower peak we were unable to reach the bottom. All sonars on board showed depths between 1,900 m and 2,500 m deep, indicating that this area is much deeper than current nautical charts demonstrate and highlighting, once again, the importance of carrying out multibeam bathymetry surveys in the Azores.

9.       Deep-sea explorations with the Azor drift-cam contributed with supporting evidence to consider Hard Rock Café and Isolado, Essential Fish Habitats. We found that these areas were both home to the highly endangered deep-sea fish orange roughy (Hoplostethus atlanticus) and large schools of the wreckfish (Polyprion americanus). These areas also showed a high number of deep-sea shark species, some of which rarely observed in the Azores. Although these areas showed low abundances in terms of benthic megafauna, we detected some frequent colonies of the slow-growing black corals Antipathes dichotoma and Leiopathes expansa.

10.   Most seamounts on the way to and around São Miguel Island, such as Albatroz N, Ferraria N, Ferraria Mar, Mar da Prata and Grande Norte host interesting deep-sea benthic communities with the deeper areas demonstrating abundant coral gardens of both Narella versluysi and Narella bellissima, sometimes, in aggregation with Callogorgia verticillata, Acanthogorgia sp. or Leiopathes expansa. Shallower areas were mainly characterized by large gardens of Viminella flagellum, sometimes associated with Callogorgia verticillata and other times with frequent and large colonies of Dentomuricea aff. meteor.

11.   The Sauerwein ridge, between the islands of São Miguel and Santa Maria, had a surprisingly low biodiversity, highlighting once again the need to better understand the reasons that explain the spatial distribution patterns of benthic communities to better inform management and conservation of these vulnerable ecosystems.

12.   Although the Grande Norte seamount was clearly the area with the highest intensity of bottom fishing, where we observed several lost bottom longlines, the benthic communities observed appeared to be in good environmental condition, displaying large aggregations of Callogorgia verticillata. These observations add to the evidence that hook-and-line fishing produces much smaller impacts when compared to other fishing gear.

13.   We continued exploring the morphological features around Princesa Alice, namely De Guerne. Most dives covered soft and mix sediments with relatively low biodiversity and abundance, with only some occasional corals of the species Acanella arbuscula, Parantipathes hirondelle and Elatopathes abietina, and dispersed Acanthogorgia sp.