LEG 1 - Príncipe Alberto do Mónaco Ridge.

1. During the MapGES 2024 cruise on-board the RV Arquipélago, we were able to perform 48 dives with the Azor drift-cam down to 1100 m depth, mostly covering the deeper strata of our sampling efforts (600-1000 m depth). We explored about 28 km of the seafloor and produced 48 hours of video footage. This year, we performed the farthest dive ever in the Azor drift-cam short history, in the Espadarte seamount, about 220 nm SW of Faial Island and about 170 nm from the closest Flores Island.
2. 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 six 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.
3. In Espardarte seamount, we lost our fourth complete Azor drift-cam system. In station 16, we got entangled in several lost fishing lines and a steep wall. We could see several lost multifilament lines hanging from the wall. We spent about 2 hours trying to get free but with no success. The umbilical broke on the hydraulic winch, and we lost a complete set of the Azor drift-cam. This is yet another example of the volume of lost fishing lines in really steep slopes of the Azores seamounts and their impact on 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.
4. 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. We will need a dedicated PhD student to count all these observations. In 2022, we were stunned by the impressive high abundances of the primnoid corals Narella spp. observed in the Farpas 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..
5. Over the last few years, we have been able to sight several sailfin roughsharks with the Azor drift-cam, which may indicate that the species is more abundant than previously expected. During MapGES 2024 Arquipélago cruise, we observed several sailfin roughsharks of the species Oxynotus paradoxus. This shark was previously perceived as very rare since it has only been observed a couple of times and was never caught on the bottom longline fishing in the Azores.
6. The overall biodiversity observed in Monte Alto and Monte Baixo seamounts were, in general, low. Despite the fact that we conducted many dives in Monte Baixo seamount, we were not able to sample many steep slopes or the summits of the geomorphological structures. In most cases, the drift went around the structures or the Azor drift-cam got stopped just before the slopes. The lack of sampling on particular steep areas of Monte Baixo seamount may prevent a complete understanding of the biological diversity of this area. Therefore, the low biodiversity inference should be taken with caution.
7. The “bird’s nest” glass sponge Pheronema carpenteri was, likely, the most conspicuous species observed during this Leg. Pheronema 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.
8. We were caught by surprise with patches of impressive biodiversity in the deep and flat Alberto do Mónaco N area. 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. This latter species was also found over soft substrate, reaching, in some instances, patches of high densities. In this area, we spotted the first sighting with the Azor drift-cam of a Risso’s smooth-head cf. Alepochephalus rostratus