Azores Deep-sea Research — Cruise OceanX 2023

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ADSR-CRUISE-20

OceanX 2023

Exploration and mapping of deep-sea biodiversity in the Azores on board the RV OceanXplorer

On this cruise, we operated from the RV OceanExplorer and visited some unexplored areas in teh Azores, such as the geomorphological structures around the Princesa Alice bank and Dom João de Castro seamount, as well as other areas near the slopes of Pico and Faial islands. 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, (iii) determine distribution patterns of deep-sea benthic biodiversity in the Azores, and (iv) determine the condition of benthic communities by looking at evidence of fishing damage to fauna, presence of lost fishing gear and marine litter. Moreover, this cruise aimed to collect biological samples of poorly known or unidentified species observed on video footage. The results of these explorations will directly contribute to the Regional Government of the Azores' efforts to declare 30% of the Azores EEZ as marine protected areas of which 10% should be strictly protected. 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. During the OceanX 2023 survey, we visited several areas in the central group of the Azores, namely D. João de Castro seamount and Princesa Alice bank and the slopes of Faial Capelinhos, Pico S Lajes, and Pico Ponta da Ilha. Taking advantage of the technological assets onboard RV OceanXplorer, namely the ROV Chimaera and the Submersibles Neptune and Nadir, we were able to conduct 8 manned submarine dives and 12 remotely operated vehicle dives, one ROV D. João de Castro seamount, 3 SUB and 3 ROV dives in Capelinhos, 5 SUB and 6 ROV dives in Princesa Alice (Princesa Alice, Princesa Alice W, Bourée E), and one ROV dive in Pico S Lajes and another one in Ponta da Ilha N. From the 20 ROV and SUB dives, 19 were successful. In general, both the ROV and the submersible dives covered a much smaller linear distance (average 952 m) per hour of survey (206 m·h^-1^) when compared to the Azores drift-cam. One of the reasons for the shorter distances was the need to collect biological samples to clarify the taxonomic identification of several organisms. During these dives, we were able to collect 268 biological samples belonging to approximately 197 different morphotypes. It is likely that this sampling effort will help solve about 100 taxonomic questions. After each ROV or submersible dive, we performed a CTD cast to measure water mass properties and collect water samples for more detailed analyses. From the 27 CTD stations, 15 were specifically conducted to address deep-sea related questions, while the other stations were performed to address the Pelagic team objectives. From these 15 dedicated CTD casts, we obtained 157 water samples for different types of analyses.

The OceanXplorer 2023 (OceanX 2023) campaign is the continuation of our long-term strategy to map the deep-sea biodiversity of the Azores and identify areas that meet the criteria for Vulnerable Marine Ecosystems (VMEs) using various imagery systems. Taking advantage of our network of international contacts, we were able to establish a partnership with OceanX, a non-profit initiative by Dalio Philanthropies that “brings science to life through captivating stories”. OceanX owns the RV OceanXplorer, which is equipped with the best and most advanced ocean exploration technology, including submarines capable of diving down to 1000m deep and an ROV capable of working down to 6000m. On this cruise, we visited emblematic and little-explored areas and took advantage of the ship's capabilities to collect biological samples of deep-sea specimens for taxonomic identification. This cruise was also supported under the Contract 18/DRPM/2022, regarding the "Characterization of deep-sea habitats, for its mapping up to the outer limit of the Azores sub-area of the Portuguese exclusive economic zone" acquisition of services between the Government of the Autonomous Region of the Azores, through the Regional Directorate for Maritime Policies (DRPM) of the Regional Secretariat for Sea and Fisheries (SRMP) and the Gaspar Frutuoso Foundation (FGF). It benefits from funding from the European Union under the operation "ACORES-14-62G4-FEDER-000001 - Filling gaps in the characterization of maritime space", within the scope of the reprogramming of the Azores 2020 Operational Program (PO Açores 2020), by incorporating the Recovery assistance for cohesion and the territories of Europe programme (REACT-EU) and by the European Regional Development Fund (ERDF).

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Statistics

Transits

1080 km

Multibeam Bathymetry

3840 km²

Filmed Seabed

19 km

Visited Areas

Stations

Dives

Video Footage Recorded

85 hours

Used Storage

0 Tb

Samples

425

— We collected 268 biological samples and 157 water samples for analysis of environmental DNA and water masses parameters

Highlights

The deep-sea component of the OceanX 2023 expedition revealed that banks and seamounts heavily exploited by bottom longline fishing are still home deep-sea benthic communities with a high natural and ecological value.

During the OXR 2023 we visited 7 different areas, and mapped 3,840 km2 of seabed, of which 630 km2 is new information to be included in official Portuguese databases. We were able to participate in 8 manned submarine dives and 12 remotely operated vehicle dives, which produced 84:30 hours of deep sea video, over 19 km of bottom, and 268 biological samples. We also performed 27 stations for analysis of water masses, in which 157 samples were collected for analysis of environmental DNA and other parameters.
We observed big basalt outcrops at around 800 m depth that were densely colonized by many colonies of the black coral Leiopathes expansa. Most of the colonies observed were visually healthy, particularly large, probably older than 1.000 years, and with a lot of associated biodiversity. It is possible that before demersal fishing exploited this bank, these arborescent black corals, vulnerable to fishing, were even much more abundant, larger and older. These corals are very slow growing and can live for thousands of years.
We also discovered one of the few (and small) hard coral reefs known in the Azores composed by the lace corals Lophelia pertusa and Madrepora occulata. This small reef was observed at around 850 m depth in the Capelinhos area, west of Faial. Hard coral reefs play an important role in the biogeochemical cycles of the deep sea, but are very vulnerable to ocean acidification. Some portions of this reef were not alive, forming a compact coral framework to which many other associated species were attached. A better understanding of their distribution and their susceptibility to climate change are priority lines of research for the future.
We also discovered one of the largest and densest coral garden dominated by the primnoid Callogoria verticillata found in the Azores. This gorgonian forest, found on the Dom João de Castro seamount, is characterized by fan-shaped colonies whose feathery branches resemble palm leaves. Most of the colonies observed were smaller than usual, but this was possibly the densest aggregation of this species observed in the Azores so far.
We observed dense aggregations of the largest species of sponges that inhabit the deep sea of the Azores (e.g., Characella pachastrelloides, Haliclona magna), on the Princesa Alice bank. Sponges play a structuring role in the deep sea, increasing ecosystem productivity and creating habitat for other species.
In one of the areas explored with multibeam, an unknown canyon (or gorge) of about 15 km long, 340 m wide and with cliffs about 100 m high was found. The canyons and gorges of the Azores are fairly unknown habitats where unique ecosystems can be found.
The OceanX 2023 expedition made it possible to identify that a large part of the benthic communities, including corals and sponges, observed in one of the Azores' main demersal fishing grounds are still in good environmental condition and have a high natural and ecological value. However, some long-lived coral colonies with visible fishing impacts were observed. These in situ observations corroborate the conclusions of previous studies which suggest that well-regulated deep-sea fishing based on hook-and-line gear (preferably handlines) could contribute to a sustainable exploitation of the deep sea.
Using the sophisticated deep-sea exploration equipment available on the RV OceanXplorer, from manned submarines to an ROV, we were able to collect 268 biological samples belonging to approximately 197 different morphotypes. It is likely that this sampling effort will help solving about 100 taxonomic questions, and some samples could even reveal new species to science.