On-board Diary: The Seamounts of Cantabria: La Maruca and El Castro

Author: Ana de la Torriente
Date: July 5, 2008



Although the morning was completely clouded over, with winds from the N-NW, we carried out two dives with the ROV at two seamounts off the Galizano coast: La Maruca and El Castro seamounts, areas where artisanal fisheries have traditionally operated.

The dive at La Maruca, at approximately 120 meters depth, was complicated due to the strong currents that dragged the boat. We found sea urchins (Echinus acutus), holothurians (Eostichopus regalis) and Thor’s scaldfish (Arnoglossus thori) on the sandy seabed (ripples). As we advanced over the seabed, we found a steep, rocky wall where we filmed corals (Dendrophyllia cornigera), gorgonians (Paramuricea cf. Placomus, Acanthogorgia hirsuta), sponges (Phakellia ventilabrum, Geodia sp., Rosella sp.), holothurians (Holothuria forskalii), sea stars (Marthasterias glacialis, Echinaster sepositus), brachipods and hydrozoans.

Special mention must be made of the enormous mixed field of gorgonians, Phakellia ventilabrum sponges, Dendrophyllia cornigera corals and hydrozoans, as well as the impressive field of Leptometra celtica crinoids over the rocky seabed. This species of crinoid is found on the sandy-muddy substrate in the Mediterranean.

The second dive with the ROV was at the El Castro seamount, approximately 6 miles from the coast, also in front of Galizano. We documented the seabed at approximately 115 meters depth, where we found a gorgonian and sponge field, including the presence of Phakellia ventilabrum sponges over a soft seabed (sand-mud).

We also found Desmacidon fruticosum and Cliona celata sponges, Dendrophyllia cornígera and Cariophyllia sp. corals, the sea star Chaetaster longipes and the ascidian Diazona violácea.

Two specimens of the 12-tentacle anemone, Peachia cylindrica, were documented on the sand. This species does not have an adhesive basal disc and is a true burrowing anemone.

We also found sand mason worms (Lanice conchilega) that make tubes out of sand grains and shell fragments that protrude above the sand.

While we were studying the seabed at La Maruca seamount, we sighted two common dolphins (Delphinus delphis) that quickly came over to the boat to play with the bow, and we passed a tuna troller.

While we sailed towards the El Castro seamount, we spotted two Portuguese man o’war (Physalia physalis) in waters at 17.8 ºC.