Spatial distribution of mud flows, chemoautotrophic communities, and biogeochemical habitats at Håkon Mosby Mud Volcano

Abstract

Marine mud volcanoes are significant source locations contributing to the marine methane cycle. Enhanced heat flow, unique chemoautotrophic communities, occurrence of massive gas hydrates and large gas plumes are direct evidences of elevated methane concentrations and the dynamic environment of mud volcanoes. Related to the high concentrations and large inventories of CH 4 in surface sediments only a fraction of the methane is exported to the bottom water. This is mainly due to chemoautotrophic communities oxidizing methane and proving a "microbial filter" reducing CH 4 fluxes. Although these processes were studied for several mud volcanoes still little is known about the spatial pattern and the areas covered by chemoautotrophic communities or by present mud flows.For this purposes the Håkon Mosby Mud Volcano (HMMV), which is located at the continental slope of the Barents Sea, was studied by several dives with the Remotely Operated Vehicle Victor6000. During these dives a high resolution microbathymetric map, with a footprint of 25 × 25 cm and a vertical resolution of better than 10 cm was derived. Furthermore, video streams of the bottom camera were converted into georeferenced mosaics, providing a detailed image about the spatial distribution of seafloor features as bacterial mats, pogonophorans, both indicating methane oxidation, or mud flows. Based on visual inspection of 2310 georeferenced mosaics covering an area of 46,160 m 2 , different biogeochemical habitats were identified and quantified on a m 2 -basis. By application of geostatistic techniques as indicator kriging the distribution of different biogeochemical habitats was quantified and mapped for the entire HMMV.Considering the flat and hummocky area of HMMV, approximately 16% (115,165 m 2 ) of the flat centre is nearly void of any benthic communities. This area is considered as a region of high methane discharge into bottom water. An area of 5% (38,244 m 2 ), located in the south-eastern part, is densely inhabited by Beggiatoa. The hummocky outer part is colonised dominantly by pogonophoran tube worms (37.3%; 276,121 m 2 ) and only occasional by Beggiatoa. Source locations and drainage directions for current mud flows were identified by computation of trend surfaces and consideration of temperature data. This suggests that present mud flow ascend close to the northern edge of the flat unit of HMMV, and that the drainage pattern of mud flows shifted from a westward to a south-south-eastern direction.

Transport and consumption of oxygen and methane in different habitats of the Håkon Mosby Mud Volcano (HMMV)

“…The spatial gradient in fluid flow rates across the HMMV has been found to create different niches for benthic assemblages, characterized by specific transport regimes and biogeochemical settings Jerosch et al 2007;Feseker et al 2008). Some temporal variability of mud volcanism was indicated by changes in absolute seafloor temperature between the different years (Feseker et al 2008), and variations in the microbathymetry of mud flows in the central and southern HMMV (Foucher et al 2009).…”

“…Videographic observations during ROV sampling indicated minor changes in overall habitat distribution within this time period. Hence, we have based the areal calculations on the detailed habitat map obtained in 2003 (Jerosch et al 2007). The gray mat habitat (III) was only recently described Lichtschlag et al 2010) and not considered as separate habitat in the previous habitat analyses (Jerosch et al 2007).…”

“…Hence, we have based the areal calculations on the detailed habitat map obtained in 2003 (Jerosch et al 2007). The gray mat habitat (III) was only recently described Lichtschlag et al 2010) and not considered as separate habitat in the previous habitat analyses (Jerosch et al 2007). Based on the published data and our video observations, we assumed that on average 75% of the hummocky area was inhabited by siboglinid tubeworms.…”

Changes in seabed morphology, mud temperature and free gas venting at the Håkon Mosby mud volcano, offshore northern Norway, over the time period 2003–2006

“…More recently, Perez-Garcia et al (2009) described the evolution of the HMMV over the last 330,000 years and, based on acoustic and seismic data, inferred the presence of a pseudo-mud chamber and a funnel-shaped geometry of the shallow part of the conduit. Field observations made during successive oceanographic expeditions have emphasized the concentric zones of litho-types, as well as of geochemical and biological processes at the surface of the mud volcano (Milkov et al 1999de Beer et al 2006;Jerosch et al 2007), and demonstrated an exceptionally high activity of fluid and gas ejections through the seabed Feseker et al 2008). Geothermal modelling indicates aqueous flow rates reaching 4-10 m year −1 at the centre of the mud volcano, rapidly decreasing to less than 1 m year −1 in its outer part (Feseker et al 2008).…”

Colonization of organic substrates deployed in deep-sea reducing habitats by symbiotic species and associated fauna

“…Colonization devices were deployed by ROV Victor 6000 (Ifremer,154 France) and recovered by the ROV Quest 4000 (MARUM, Germany) after 12 months (Table 1) 155 in the south Hummocky periphery of the mud volcano where there was generally a high density 156 of siboglinids (>50%) and lower density of Beggiatoa spp. (<20%) (Jerosh et al, 2007). 157 158…”