ROV research dives in the Mediterranean sea in search of Sponges!
Oded Ezra, Tal Idan
One of our exciting and interesting tasks with ROVs is the work we do in collaboration with the Sponges research lab of Prof. Micha Ilan from the university of Tel-Aviv (https://milan35.wixsite.com/tau-porifera), on-board the research vessel ‘Mediterranean Explorer’ that is owned and operated by Eco-Ocean, an NGO that supports research, education and environmental projects in Israel.
Every few months or so we set out to go for a few days of dives (returning port every night) at different sites offshore Israel. Most of our dives are performed at water depths of around 100 meters, at dive sites where high concentration of sponge species are found. We first choose a dive site by using maps of areas that were charted by high resolution multibeam. Normally we choose sites where significant rocky areas are apparent in the charts, some of the locations are places where we normally return to and survey and sample repeatedly. Using our USBL system we can accurately return to known sites of interests where we previously sampled or left a sensor on the seabed.
Our main tasks for these dives are normally video surveys of the sites, providing the scientists with visual data which they later use for ecological purposes and also sampling tasks of sponges by using the ROVs electric manipulator (arm) and a dedicated sample basket. From time to time we also place current and light sensors on the seabed, also using the ROV for that. In a typical ROV dive that lasts a few hours we can sample up to 10-20 different sponge samples and using the crane and sampling basket there is no need for the ROV to go back to surface between sampling and so continually stay near the seabed in search of new samples.
Samples of sponges such as Chondrosia, Axinella, Chalice and many more are being sampled by the ROV and hauled to deck by the sampling basket, preserved in different containers, depending on their research purpose so that later they can be studied at the university’s lab. Among the numerous research dives we performed together with the Sponge lab, new species of sponges and other invertebrates, as well as new chemical compounds, were discovered and several scientific articles were published during the years. Here’s for many more successful research dives!