The effect of mud volcano activity on biodiversity at shallow to deep water mud volcanoes at the Moroccan Atlantic slope and in the Gulf of Cadiz
Pannemans, B.; Van Rensbergen, P.; Cunha, M.; Bilova, E.; Henriet, J.-P.; Ivanov, M.; Pinheiro, L.; Van Gaever, S. (2004). The effect of mud volcano activity on biodiversity at shallow to deep water mud volcanoes at the Moroccan Atlantic slope and in the Gulf of Cadiz, in: 32nd International Geological Congress, Florence, Italy, August 20-28, 2004. Abstract Volume. pp. 1478 (Abstract 336-11)
In: (2004). 32nd International Geological Congress, Florence, Italy, August 20-28, 2004. Abstract Volume. IGC: Florence. 2 vols pp.
The newly discovered Larache mud volcano field at the Moroccan Atlantic slope (200 m - 700m water depth), and a deep water mud volcano field (1000 m - 1200 m water depth) in the Portuguese sector of the Gulf of Cadiz, have been investigated using side scan sonar, multibeam, video imagery, TV-guided grab, dredge and coring. At five mud volcanoes (Al Idrissi mv, Mercator mv, Gemini mv, Aveiro mv, and Captain Arutnyov mv) biodiversity was studied in relation to environmental factors.This study illustrated that the occurrence of mud volcanoes on the continental slope create new habitats and add to biodiversity. The study yielded the following results:
The thickness of hemipelagic drape overlying mud breccias showed that all mud volcanoes have been active in the last 1600 years.
Video imagery observations indicate an eastbound current over the Al Arraiche mud volcano field. At greater water depths this current becomes more variable.
Faunal assemblages change with the sedimentary facies of the sea floor at each mud volcano
Currents influence the distribution of trophic groups over the mud volcanoes. Populations of filter feeders are more dense on the upcurrent slope. On the downcurrent slope they are replaced by deposit feeders and scavengers.
Faunal diversity and bioturbation increases at seep sites
Abundances of megafauna decreases with increasing water depth.
The disturbance of the fauna by mud eruptions is small as periods inactivity are much larger than the time needed for recolonization. Seepage of fluids has a longer-lasting influence, resulting in a decrease of sessile filter feeders and burrows towards the summit of most mud volcanoes.The data were acquired during 2 consecutive surveys by the R/V Belgica (CADIPOR cruise) and the R/V Prof Logachev (TTR 12 cruise).
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