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High-resolution imaging techniques to investigate faunal dynamics at deep-sea vents

Why use high-resolution imaging at deep-sea vents?

The team are working on the use of high-resolution imaging techniques to investigate the scale patterns of faunal dynamics at deep-sea vents and delineate the factors shaping those dynamics. They present case studies demonstrating how technological advances in underwater platforms and computer power have proved beneficial to using imaging techniques to expand knowledge on vent ecology. Indeed, our scientific perception of natural systems is highly constrained by technological limits. The methods we develop can be used to acquire insights on hydrothermal vent fauna ecology, hence expanding ecological characterisation across various spatial and temporal scales. Imaging techniques are non-destructive. This makes them ideal to characterise the deep-sea communities without disturbing them, since we do not know for sure the impact that repetitive long-term scientific sampling can have on them.

Can the team provide examples of successfully acquiring useful long-term high-resolution time series at deep-sea vents?    

Yes! For example, the analyses of images acquired daily over 7 years with the TEMPO underwater camera connected to the deep-sea European Multidisciplinary Seafloor and water-column Observatory (EMSO)-Azores observatory revealed the high stability of the vent habitat and associated Bathymodiolus azoricus vent mussel assemblage (see Figure below). We further developed a baseline workflow that enabled to detect a short migration of the vent mussels of 2 decimetres over 2 years.

Bathymodiolus azoricus mussel assemblage delimited for the whole time series in (A) 2012-2015 and (B) 2012-2019). The redder, the more stable the cover. The bluer, the more sporadic was the cover observed there. (C) The TEMPO underwater camera that spent 7 years at -1,700 m. (Van Audenhaege et al., 2022: https://doi.org/10.1016/j.pocean.2022.102791).

Moreover, the team shows the benefit of 3D reconstructions over several years to accurately unravel the dynamics of vent assemblages over a 450-m² hydrothermal edifice with a resolution of a few centimetres (Eiffel Tower edifice, -1,700 m, Lucky Strike, Mid-Atlantic Ridge) despite the complex topography of the sulphide edifice. This 5-year time series confirmed the high stability of the vent communities, despite local changes in the immediate vicinity of vent exits (see Figure below). Vent mussels appear to reposition over a few decimetres, but their overall population remained constant.

3D reconstruction over a 450-m² hydrothermal edifice in 2020 (Eiffel Tower edifice, -1,700 m, Lucky Strike, Mid-Atlantic Ridge) (Van Audenhaege et al.: A novel photogrammetry approach reveals scales of vent assemblage variability (in prep.)). The fine-scale details retrieved by 3 photogrammetric reconstructions from 2015, 2018 and 2020 were used to annotate changes of the vent fauna in 3D.

The team is also currently discussing the use of 3D high-resolution models retrieved from seafloor images to characterise the distribution of biological communities over the portion of hectares of seabed at the hydrothermal vent field of Lucky Strike, near the Azores Islands (see Figure below). The navigation, corrected by photogrammetric reconstruction, provides an accurate mapping of biological assemblages. Those spatial patterns provide detailed information on the drivers shaping their spatial distribution, for instance according to the seafloor terrain or the presence of other organisms.

(A) Bathymetric map of the Lucky Strike vent field with the imprint of seabed images in red (White Castle), blue (Montségur), green (Tour Eiffel) for each site where the seabed was imaged. (B) Forward-looking view of the 3D reconstruction of the Montségur site. The arrow shows the view of (C) the Montségur edifice, here shown in the 3D reconstruction.
Why are the high-resolution imaging techniques important for unravelling the deep-sea vent dynamics?

Ecological investigation aims to characterise patterns of variability in faunal communities in order to better delineate the biological and environmental drivers affecting their distribution and dynamics in space, from centimetres to kilometres, and in time, from infra-daily to a decade. Understanding these patterns requires high-resolution and long-term monitoring over large areas of biological communities and their environment. With the improvement of underwater platforms and resolution of optical imagery, imaging the deep sea has become a powerful and increasingly cost-efficient method for characterising deep-seafloor habitats and associated communities across scales.

For more information

If you want more information, please contact Loïc Van Audenhaege (loic.vanaudenahege[at]gmail.com/ loic.van.audenhaege[at]ifremer.fr), but please also check the following:

  • Part of this work has led to a green open-access peer-reviewed publication ‘Long-term monitoring reveals unprecedented stability of a vent mussel assemblage on the Mid-Atlantic Ridge’: https://doi.org/10.1016/j.pocean.2022.102791

Main contributors: Loïc Van Audenhaege, Jozée Sarrazin, Marjolaine Matabos, based at IFREMER (Brest, France)

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EU

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 818123 (iAtlantic). This output reflects only the author’s view and the European Union cannot be held responsible for any use that may be  made of the information contained therein.