On-board Diary: Seco de los Olivos (day 4)

Author: Ricardo Aguilar
Date: August 1, 2007



More surprises in this area. We continue investigating the area around Seco de los Olivos. Near the main seamount, there is a group of smaller elevations that almost surround it as if they were a crown. All of them are proving to be quite interesting.

Today, we’ve decided to use the ROV to go down to 200-210 meters on the seamount closest to the coast. The summit is located at 120 meters depth and it plunges to more than 350 meters from there. It is very rocky and, like all the ones we’ve seen, is plagued by fishing tackle and abandoned ropes. There is not one single place we’ve sampled that is untouched by human hands.

The surprise came when we found some fabulous sponges. They are hexactinellids or large, upside-down, hat-shaped glass sponges. They are the same ones that have been found in El Cachuco bank in Asturias and are referred to as “hat sponges”. The ones we’ve found are 40-50 centimetres in height. There are other sponges that are difficult to identify; some also look like hexactinellids (similar in shape to the Rosella species but less wrinkled) and others are desmosongias, amongst them, if we’re not mistaken, possibly Phakellia ventilabrum.

Although there are also gorgonians in the area, such as the whip gorgonian (Viminella flagellum), sponges are the dominant species.

In the most abrupt area, we spot the popular swallowtail seaperch (Anthias anthias), a few scale-rayed wrasse (Acantolabrus palloni) and large grey groupers (Epinephelus caninus). It’s interesting that this species of grouper occurs frequently in seamounts and in large sizes, whereas it is not very common in coastal areas and almost all the specimens we find are quite small.

During the second dive with the ROV, we return to the main seamount to take a look at the area we haven’t seen. The landscape we find here is similar to the other areas we’ve sampled. Sandy bottoms with small and medium-sized rocks, many gorgonians and other anthozoans (Eunicella verrucosa, Swiftia pallida, Bebryce mollis, Viminella flagellum, Paramuricea clavata, Elisella paraplexauroides, Callogorgia verticillata, Dendrophyllia cornigera, Caryophyllia spp., etc.). As far as fish are concerned, we spot a large monkfish (Lophius sp.) and amongst the rocks, seabass (Serranus cabrilla), rainbow wrasse (Cois julis), scale-rayed wrasse (Acantholabrus palloni), greater forkbeards (Phycis phycis), etc.

The divers take their turn in the afternoon. We continue to collect data about the mixed seagrass prairies (Posidonia oceanica and Cymodocea nodosa) in front of Punta Sabinal. The Mesophyllum alternans reef occurring amongst the rhizomes where we’ve been today is more deteriorated. Even so, it is still rich in fauna and flora.