On-board Diary: Urdaibai , July 19

Author: Ana de la Torriente
Date: July 19, 2008



Today, we will spend the day diving around Urdaibai while the ROV technicians install and test the equipment.

The natural areas from Mundaka to Gernika that comprise the Oka River, which extends to the Urdaibai marshes, were declared a Biosphere Reserve. Interestingly enough, we are finding an abundance of fish precisely in the areas where many species lay their eggs –such as shallow areas near the mouths of the estuaries and marshes. As such, protecting the Urdaibai area and other similar ecosystems contributes to the maintenance of biodiversity and we are proud to be a part of that.

The diving was carried out early in the morning, off the area NE of the Izaro Island, a rocky mound that falls from the surface of the ocean to 25 meters depth.

The most amazing part was the most superficial area, up to 10 meters depth, where once again, there was an abundance of fish: saddled seabreams (Oblada melanura), bogues (Boops boops), grey mullets (Mugil sp.), seabass (Dicentrarchus labrax), black seabreams (Spondyliosoma cantharus) and ocean sunfish (Mola mola). Under 15 meters depth, a strong thermocline marked a sudden change in temperature, from 10ºC in the shallower areas to 14 ºC in the deeper areas.

We found fields of various species of gorgonians in the deeper waters (Eunicella verrucosa, Leptogorgia tormentosa, Leptogorgia lusitanica). And we also detected many discarded fishing lines on the seabed.

After the divers came up and we finished installing and setting up the ROV, we tested it in that same area, at 40 meters depth, to confirm that it was operating correctly before submerging it to 200 meters depth at the canyons. At the same time, SE of the Izaro Island, two Portuguese man o’war were pulled by the currents towards the closest beaches.

At night, we carried out a night dive on the rocky seabed, SE of Izaro Island, were we anchored and spent the night. This area was similar to other Cantabrian areas in that the seabed was covered by sporophytes (Falkenbergia rufolanosa) and other algae from the Codium, Peyssonelia and Cystoseira families. Corallina elongata and Padina pavonica were also present, although in smaller amounts.

Amongst the invertebrates, we found the gaping file shell (Limaria hians) –which is rarely found and lives underneath the rocks- the ascidian (Botryllus schlosseri), the sea slug (Aplisia fasciata), the anemones Aiptasia mutabilis and Cerianthus membranaceus and the shrimp Periclimenes sagittifer amongst the tentacles of an Anemonia sulcata.

We also spot two species of clingfish (Lepadogaster candollei, Lepadogaster lepadogaster) –also known as shore clingfish- that posess a sucking disk to help them adhere to rocks.