Abstract
Main objectives: MapGES 2024 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. In this cruise, we operated, once again, from the RV Arquipélago and planned to visit some unexplored areas along the Alberto do Mónaco ridge, Princesa Alice, and some other areas along the Mid Atlantic Ridge. We aimed to expand previous explorations of these areas into deeper waters. During Leg 1, we visited Princesa Alice SW, Monte Alto, Espadarte, Farpas, Monte Alto SE, Monte Baixo, Voador, and Alberto Mónaco N. In Leg 2, we visited Princesa Alice, Princesa Alice S and Princesa Alice SE. Leg 3, aimed to visit Mar da Prata bank, D. João de Castro, and Heitor Álvares seamounts but was cancelled because of problems in the hydraulic which of the vessel. In leg 4, we visited Boureé NE, Boureé E, Princesa Alice, Princesa Alice S, Princesa Alice W, De Guerne, Açor S, Açor, Óscar, Bicuda, and Ferradura. 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 & IICM Okeanos at the University of the Azores. It allowed recording high-quality underwater video images of the seabed down to 1000 m depth. The system was deployed from the Research Vessel Arquipélago, owned by the Government of the Azores. In each of the areas or geomorphological structures to be explored, a representative number of dives (or transects) were carried out with a video camera system from a depth of about 1 000 m to the shallowest depth of each structure. The objective is to obtain underwater images to characterize the biodiversity along the entire bathymetric gradient and substrate types of each structure. The video transects were planned according to the best bathymetry available, so that the camera systems move from deeper to shallower areas. This methodology allows the collected images to always have the best possible quality, maximizing the area of incidence of light and avoiding its dissipation in the water column (in the case of descending transects). The transects carried out with the Azor-drift-cam were planned to last approximately 60 min in the seafloor, with the system drifting over the benthic habitats at an approximate speed of 0.5 to 1 knot. Under normal oceanographic conditions, each working day allowed for 5 to 6 dives, corresponding to around 5 km of bottom explored per day. Cruise summary: The MapGES 2024 cruise onboard RV Arquipélago was composed of 4 Legs, which were planned to visit some unexplored areas along the Alberto do Mónaco Ridge, the Princesa Alice bank and its surrounding areas and some seamounts along the Mid-Atlantic Ridge. Overall, 144 dives out of 145 stations were accomplished in 20 sampling areas, covering approximately 83km of the seafloor and generated 139 hours of videos images for analysis. During Leg 1, from 6th to 15th July 2024, we performed 47 successful dives with the Azor drift-cam. During this Leg, we managed to perform the 1000th dive with the Azor drift-cam, as well as the farthest ever from land. Unfortunately, we lost one complete Azor drift-cam system (the fourth since we started operating the system back in 2019) due to entanglement on lost longlines near a vertical wall. During Leg 1 we surveyed the deep-sea benthic communities dwelling on the geomorphological structures along the Alberto do Mónaco Ridge. During Leg 2, from 17th to 31st July 2024, we performed 31 successful dives with the Azor drift-cam aroud the Princesa Alice bank areas, but the weather conditions severely limited our operations in this important Azorean fishing ground. Leg 3 of the MapGES 2024 was canceled due to multiple technical issues related to the research vessel Arquipélago, which prevented us from carrying out our work. Leg 4 of the MapGES 2024 cruise was composed of two parts. During the first half of Leg 4, from 24th to 30th August 2024, we performed 43 successful dives with the Azor drift-cam, continuing the exploration of the Princesa Alice bank and expanding our work to its surrounding areas. During the second half of Leg 4, from 3rd to 6th September 2024, we performed 21 successful dives in some seamounts along the Mid-Atlantic Ridge, including Óscar, Bicuda and Ferradura. Main achievements: During the MapGES 2024 cruise on-board the RV Arquipélago, we were able to perform 144 dives with the Azor drift-cam down to 1100 m depth, where we explored about 83 km of the seafloor and produced 139 hours of video footage. This year, we performed the farthest dive ever from land on the southwest tip of the Alberto do Mónaco ridge, in Espadarte area. On July 12th 2024, we achieved an impressive and unbelievable milestone: the dive 1000 with the Azor drift-cam. Back in 2018 when we started to design a low-cost system to provide us with some images of the seafloor of the Azores, we never expected that only 6 years later we would have visited all geomorphological structures shallower than 1000 m and produced one of the world’s most comprehensive dataset of deep-sea benthic megafauna biodiversity distribution. In Espadarte seamount we lost one complete Azor drift-cam system; the fourth since we started operating the system back in 2019. In station 16, we got entangled on several lost fishing lines and a steep wall. We could see several lost multifilament lines hanging from the wall and spent about 2 hours trying to get it free but with no success, seince the umbilical broke on the hydraulic winch. This is yet another example of the volume of lost fishing lines in really steep slopes of the Azores seamounts and the impact they have in deep-sea exploration. After this unfortunate event, we cancelled the dives for the rest of the day, prepared a new set of the Azor drift-cam, and were ready to go. Although, the video annotations still have to be finished, it seems that we confirmed Farpas seamount as one of the areas in the Azores with higher densities of the primnoid corals Narella bellisima and Narella versluysi. In 2022, we were stunned by the impressive high abundances of the primnoid corals Narella spp. observed in this seamount with the NIOZ towed camera system, during the iMAR Eurofleets+ cruise. It was with no surprise but with great joy that the Azor drift-cam dives confirmed that similar ridges in the Farpas seamount host similar high abundances of these species. Remarkably, the density of these corals frequently exceeded 10 colonies per square meter, accompanied by a diverse array of other benthic species. This observation reinforces the ecological significance of this area and highlights the rich biodiversity found within the deep-sea environments of the Azores. We were caught by surprise with occasional rocky outcrops filmed at the deep and flat Alberto do Mónaco N area teeming with benthic fauna with patches of impressive biodiversity. The expectations for the biodiversity explorations in this area were low, given the flat and deep nature of the structures. However, on a couple of rocks we observed black corals Leiopathes expansa with Madrepora oculata, Paramuricea, and Candidella imbricata. The “bird’s nest” glass sponge Pheronema carpenteri was, likely, the most conspicuous species observed during this cruise. This sponge was frequently seen occupying the deeper strata samples, between 650 and 1000m depth, in small to large patches over soft bottoms. Not surprisingly, this species is one of the most common records in our deep-sea biodiversity occurrence database. We finally explore more thoroughly a large area that includes Princesa Alice and Açor banks, achieving a total of 74 successful dives in these and their vast surrounding areas. Despite being the most heavily fished grounds of the Azores archipelago, these areas showed a high diversity of megabenthic fauna and communities, across all depth strata explored. We also reached the goal of exploring the deeper sectors of some seamounts of the Mid-Atlantic Ridge. Back in 2019, the exploration of the seamounts that compose this large mountain chain was confined to 600m depth, which meant that the exploration of these areas still lacked in representativeness. During this cruise, we wanted to complement these past surveys with the exploration of deeper strata, thus making the survey of these areas more complete. Indeed, these sectors revealed diverse benthic communities of several coral species such as large Paragorgia johnsoni, Leiopathes expansa, Placogorgia sp., Lophelia pertusa, Madrepora oculata, Hemicorallium niobe, H. tricolor, Pleurocorallium johnsoni , and Pseudoanthomathus sp., revealing the presence of unique fragile and vulnerable deep-sea ecosystems along the MAR. Óscar, Bicuda and Ferradura seamounts contained other relevant benthic assemblages, including dense Narella spp. gardens and great abundances of Acanthogorgia spp., for instance. Unfortunately, the goal of visiting the Mar da Prata bank and the D. João de Castro and Heitor Álvares seamounts during Leg 3 could not be achieved due to technical reasons related with the RV Arquipélago hydraulic system, which stopped working during Leg 2 of this cruise. As the issue remained unsolved f
VALTER MEDEIROS