First faunistic results on Valencia (Cresques) Seamount, with some ecological considerations

J E Cartes,A Serrano,S Parra,V Papiol,D Lloris,D Díaz-Viñolas,A Carbonell,S Gofas,D Palomino,A Lombarte,C Salas

doi:10.1186/s41200-021-00210-y

Abstract

The living and dead fauna of Valencia Seamount, a deep promontory in the middle of the Balearic Basin which summit is at ca. 1100 m depth, is described by first time based in a rock dredge perfomed in a sedimentary area of the summit Mount. Surface-feeder polychaetes (the Paraonidae Levinsenia gracilis and Terebellidae as dominant), and taxodont bivalves (Ledella messanensis and Yoldiella ovulum) were the main species of benthos. We found alive remains of the bamboo coral Isidella elongata, a vulnerable, habitat-forming species in the deep Mediterranean. Benthos density was low (0.6 organisms/2 dm3 mud). Thanatocoenosis evidenced a rather moderate diversity of benthic bivalves (11 species) and gastropods (9 species) also dominated by surface deposit feeders. Fish (identified/quantified from sedimented otoliths) showed diversified and abundant mesopelagic fauna, mainly Myctophidae. More interestingly, we highlighted among benthopelagic fish the occurrence of recruits of Merluccius merluccius, Micromesistius poutassou, or Hymenocephalus italicus, all species that live in the neighboring slopes of the Iberian Peninsula and the Balearic Islands at quite shallower depths (at 100-700 m) than their distribution in the Valencia Seamount summit (1102–1130 m) based on the deposited otoliths found. Some ecological aspects were discussed and the necessity to consider the deep Valencia Seamount as a potential area that should be under protection.

Highlights

According to Barone and Ryan (1987), the Valencia Seamount is an elongated mount located in the Balearic Basin, oriented NW-SE, with numerous spurs whose shape resembles a short-legged insect or starfish
The objective of this study is to describe the fauna of the Valencia seamount for the first time, based on both its living animals and reconstructions of fauna from the thanatocoenosis, i.e., the remains filtered from the sediment
We found living remains of the bamboo coral Isidella elongata, consisting of 3 branch pieces with 5 polyps, plus fresh sclerites

Summary

Introduction

According to Barone and Ryan (1987), the Valencia Seamount is an elongated mount located in the Balearic Basin (western Mediterranean), oriented NW-SE, with numerous spurs whose shape resembles a short-legged insect or starfish. It is located close (7–8.5 km) to the Valencia Trough, where we found maximal depths of 2200–2300 m in the Balearic Basin. In 1986, these authors described the morphology of this mount using side-looking sonar (Sea MARC I) and swath-mapping sonar (Sea Beam), which yielded detailed bathymetric and sedimentary maps This submarine structure was named the Cresques Seamount (Rovere and Würtz 2015) in honour of a recognized Balearic. In its summit and the upper parts of the slopes (ca. 1020–1300 m), there are avalanche scars and debris flow deposits with sedimentary bottoms (Barone and Ryan 1987).

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Conclusion