Based on recent technological developments, it is now possible to continuously monitor hydrothermal vents ecosystems using video cameras connected to seafloor installations, called observatories. The TEMPO ecological module, designed and developed by IFREMER teams, can monitor the daily activities of animal communities. It is fitted with a video camera, four spotlights on articulated arms, a temperature probe, an oxygen probe and a chemical analyser to determine the iron concentrations in the environment in real time.
Below, Julien Legrand, engineer in the Technological Development Research unit at Ifremer, presents the structure and functioning of deep sea observatories
While this type of arrays has existed for a long time in some scientific areas such as physics, the concept of multidisciplinary observatories is quite recent. These observatories gather on a single site instruments that measure physical parameters (such as temperature, currents, pressure), chemical parameters (for example, oxygen, pH, methane) as well as biological parameters extracted from images from videos cameras or sonars, which allows to obtain optical and acoustic images of the background. These images can be used to evaluate biological activity in terms of species abundance, animal movement, and behaviour.
Only three observatories harbour a multi-disciplinary array at hydrothermal vents: the Ocean Networks Canada observatories off the coast of Vancouver Island (British Columbia, Canada), and the Ocean Observatory Initiative off Oregon (USA), both located on the Juan de Fuca ridge. EMSO-Azores is located off the Azores in Portugal along the Mid-Atlantic ridge.
Two types of observatories exist: autonomous and cabled. Autonomous observatories, such as EMSO-Azores, rely on batteries deployed on the seabed and are therefore limited in energy. On the EMSO-Azores observatory, lithium batteries are installed on monitoring nodes (called Seamon) and provide energy to the various connected instruments deployed on the bottom. A central electronic unit, the COSTOF, insures instruments programming and data storage. Data are once per day acoustically transmitted to a surface buoy and the transferred to the data center at Ifremer Brest via a satellite link. Only the video data and seismic data, representing large volumes, are stored locally and are recovered during the annual maintenance cruise. We however receive a daily snaphshot from the camera.
Cabled observatories are directly connected to land, and for this reason have no energy limitation. The Ocean Networks Canada cabled observatory consists in an 800km loop of cable that distributes 20,000 volts to five benthic nodes deployed from the coast (20 m) to the abyss (2700 m). This same cable also contains an optical fiber that allows the transfer of data from the instruments to the shore station where data is then transferred via Internet to two data centers, one at the University of Victoria in British Columbia and the other in Saskatoon, Saskatchewan at 1,700 km away from there. This backup helps preserve the data in case a devastating earthquake or tsunami occur on the Pacific coast! One of the nodes of the observatory is located on the Endeavor segment of the Juan de Fuca Ridge, the main installation being deployed in the Main Endeavour Field. In this area the hydrothermal edifice Grotto appear as a Christmas tree with the wide range of instruments that it supports, from temperature probes to fluid samplers...
For more information on the Ocean Networks Canada initiative, visit the following page.
More recently, Ocean Observatory Initiative in the USA, installed a cabled array on the Juan de Fuca Ridge south of ONC on the Vance segment on the Axial Seamount volcano. More on OOI/Axial Seamount.
The ecological module TEMPO, designed by Ifremer, allows the daily monitoring of faunal communities. It is equipped with a camera, four light spots on mecanical arms, temperature probes, an oxygen sensor and a chemical analyser that allows in situ iron concentration measurements.
Two versions of the TEMPO module are currently deployed on deep-sea observatories: EMSO-Azores on the Mid-Atlantic Ridge and NEPTUNE Canada on the Juan de Fuca Ridge in the Pacific Ocean. Videos sequences from the Pacific can been screened using the ONC Seatube channel !