Report on developments dedicated to monitor and study benthic comportment and processes

Type Contract report
Date 2017-09-18
Language English
Ref. JERICO-NEXT-WP3-D3.10-170917-V1.3
Other localization
Author(s) Carlier AntoineORCID1
Contributor(s) Vaz SandrineORCID, Facq Jean-Valery

The objective of this task is to develop a new towed underwater video system (TUVS), called ‘Pagure-2’ in order to map habitats, describe biodiversity, and monitor ecological changes in coastal benthic ecosystems. For this purpose, we modified an existing TUVS (‘Pagure’) to expand the range of accessible benthic habitats, to get more stable footage on irregular rocky bottoms, and to investigate fragile ecosystems (e.g., marine protected areas) where impact has to be limited. Thus, the Pagure-2 is a more versatile tool capable of being deployed on two different configurations: a classical ‘sledge’ mode with skates, and a ‘flying’ mode that reduces contact with the sea floor. It is easily deployable on small (~25 m) coastal vessels as well as large research vessels and was designed to cope with a 10-500 m operating depth range and with all kind of sea conditions and currents. It is also simple to use opportunistically on different kind of scientific cruises (benthic survey, fisheries stock assessment, hydrology, etc…) and without any dedicated specialist staff.

The two first years of the project were dedicated to the design, the production and the tests (in experimental tank and at sea) of the TUVS Pagure-2.

The optical sensors (front video camera and vertical still camera) provide data of very good quality during several tests at sea in 2016. Additional side cameras were used to assess the balance of the system and its footprint on the bottom.

A laser line coupled to a small video camera allows assessing surface microtopography (including features created by burrowing animals). The steel-frame of the Pagure-2 has been designed to integrate sensors of important environmental parameters (like temperature, salinity, oxygen, turbidity) to help to better characterize the ecological status of benthic habitats. However, these complementary equipments cannot be bought and installed in the context of the JERICO-Next project.

At this stage, the TUVS Pagure-2 proved to be a relevant imagery tool to get comprehensive insights into the integrity of benthic habitats of European coastal areas. The flying mode deployment still needs to be tested at sea in order to improve the stability of the system during towing and the measure of the vertical camera’s coverage. This less destructive configuration should be particularly relevant to study benthic biodiversity in protected areas where disturbance has to be limited (e.g., maerl and seagrass beds, rocky bottoms with large erected benthic species).

Numerous applications should come in the next years, such as investigations of areas adversely affected by invasive species (e.g., Crepidula fornicata), human activities (bottom-trawling, sand-mining, marine renewable energy development).

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