A summary from on board the RV Sarmiento de Gamboa in the tropical Atlantic
by Cova Orejas, Veerle Huvenne and Andrew Sweetman
Monday 16 August, 07:00 am: A CTD is in the water. There is always something in the water during iMirabilis2, as our tight programme does not afford us much spare time. However, the steaming back and forth between our two main research areas gives us some time to enjoy the view of the Atlantic in the tropics and a dramatic view on the volcanic islands of Brava and Fogo when we approach them. After two intense weeks of work, many of our planned activities are well underway. In the main lab, where most of our life on board takes place, we have our own “wall of success” where we keep a record of the stations we have already accomplished.
The abyssal plain study area has been well covered by the work conducted so far by the lander team – Andrew, Dani and Alycia. The camera lander, baited trap and respirometer have already supplied new information and a lot of data from these unknown regions, including novel results from in situ experiments contributing to better knowledge of the functioning of the abyssal plains around Cabo Verde. On-board experiments on board have also been successfully conducted by the lander team and are now finished. The results will show the potential consequences of future climate change scenarios on the functioning of the soft bottom deep-sea communities in these latitudes.
Above: Timelapse montage of imagery taken by the camera trap, 16 August 2021. Images © Prof. Andrew Sweetman / Lyell Centre – Heriot-Watt Unviersity / iMirabilis2
As well as the research on the functional ecology of the fauna and microbes inhabiting the Cabo Verde abyssal plains, several CTD-Rosette casts have been conducted thanks to the dedication of Iván and Ángela, to characterise the oceanography of the area. The water collected at different depths will be analysed for a range of purposes, including eDNA analyses which will be done by Susan, and particulate organic carbon and stable isotope analyses that Bea will conduct back in the lab on land. All these analyses will allow us to better characterise the area and support the interpretation of results from other studies conducted on board. Finally, Iván and Mario successfully collected a multicore from 4300 m depth, the analyses of which will shed light on the paleoceanography of the area. We hope in the coming days the technical challenges on Autosub6000 will be solved: Dan, Richard, Stewart and Eoin are working hard on this, and the AUV will conduct missions over the abyssal plain to obtain high-resolution multibeam data, seafloor imagery and eDNA samples that will allow Veerle, Erik and Susan to create a habitat map. A suitable target for this research has been selected through the multibeam ground-truthing surveys conducted by Veerle and Pablo. Autosub6000 has already supplied novel eDNA samples from two different areas around Cabo Verde, using the new RoCSI sampling equipment looked after by Susan.
Besides the work on the abyssal plains, the sampling on the Cadamosto seamount continues, thanks to the great ROV Luso team: Antonio, Andreia, Bruno, Renato and Miguel. Two impressive ROV dives have been conducted and have revealed the high diversity and beauty of the deep seas around Cabo Verde – some highlights are shown in the photos below. Murray, Bea, Andrea, Veerle, Kelsey and Cova – the “ROV scientist team”- have very much enjoyed the discovery of these new areas that have never before been explored.
We have nearly completed the water column characterisation of Cadamosto, and coring has been performed at different depths of the seamount to investigate the paleoecology of the area, which will be investigated at home by Irene and David.
Cadamosto is a seamount offshore Cabo Verde, exposed to the dynamic and often challenging oceanic weather conditions. High winds of more than 20 knots required us to change plans, and we moved closer to Fogo to benefit from the protection of the island. These meteorological conditions, together with the technical challenges of the expedition, require us to continuously plan and then replan. But the team is very resilient and adapts to these frequent changes brilliantly. Some ROV dives have been conducted on the slopes of the impressive volcanic island of Fogo, revealing a different benthic fauna compared to the deep-sea fauna of Cadamosto seamount.
These last two weeks at sea and the results collected to date allow us to start to get an impression of these deep-sea ecosystems and, as always, more questions than answers are emerging in our conversations on board… there’s still two weeks ahead of us and lots to explore!
We’ll keep you all updated through our outreach activities, expertly coordinated and supported by Kelsey, Roger and Vikki (onshore).
Many greetings from the deep seas around Cabo Verde!