Seabed methane emissions and the habitat of frenulate tubeworms on the Captain Arutyunov mud volcano (Gulf of Cadiz)

Abstract

Submarine mud volcanism represents an important pathway for methane from deeper reservoirs to the surface, where it enters the benthic carbon cycle. To quantify overall methane release from the Captain Arutyunov mud volcano (CAMV) and to assess the contribution of macrobenthic seep organisms to the regulation of the benthic methane flux, we linked water column methane concentrations, seabed methane emission and pore water geochemistry to the spatial distribution of seep biota. Prominent organisms of the CAMV seep biota were 3 different species of frenulate tubeworms. Seabed methane emission ranged from 0.001 to 0.66 mmol m -2 d -1. Dense patches of tubeworms were associated with the lowest seabed methane emission. Elevated methane emission was associated with a sporadic distribution of tubeworms and the occurrence of numerous mud clasts. Despite the presence of a large subsurface methane reservoir, the estimated total methane release from CAMV was low (0.006 × 10 6 mol yr -1). In addition to direct methane consumption by Siboglinum poseidoni, the tubeworms likely contribute to the retention of methane carbon in the sediment by affecting bacterial communities in the proximity of the tubes. The siboglinids create new meso-scale habitats on the sediment surface, increasing habitat heterogeneity and introducing niches for bacterial communities.

Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone

“…In situ benthic flux measurements were conducted using the biogeochemical observatories BIGO and BIGO-T (Sommer et al 2009). BIGO contained two circular flux chambers (internal diameter 28.8 cm, area 651.4 cm 2 ).…”

The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone

“…In situ fluxes were measured using the biogeochemical observatories BIGO and BIGO-T as described in detail by Sommer et al (2009) Fig. 1).…”

Sucessão ecológica em parcelas orgânicas de madeira, macroalgas e em carcassas de baleia no mar profundo; e similaridade de espécies entre habitats redutores no talude continental da Califórnia (Pacífico Nordeste)

“…The siboglinid habitat exhibited macrofaunal densities (6821 ind.m -2 ) comparable to pogonophoran fields at deeper seeps in the Gulf of Alaska (~ 4000m; 6625 to 9739 ind. m -2 ), but lower densities than similar habitats at shelf to slope depths in the North Sea and Gulf of Cadiz (Dando et al 1994, Levin & Mendoza 2007, Sommer et al 2009). Depth-related effects of food limitation on macrofaunal abundance are masked at seep sites where the input of chemosynthetic carbon can provide the fauna with additional energy sources .…”

“…At seep areas where siboglinids fields are prominent, they reach high abundances in reducing sediments with dissolved methane or sulfide, allowing them to nurture their bacterial symbionts and yet provide access to oxygenated waters through their anterior end (Schulze & Halanych 2003, Southward et al 2005, Dando et al 2008, Sommer et al 2009). At the San Clemente seep, their higher abundance at sediments nearby tubeworm thickets suggests a heterogeneous spatial distribution on the flux of reduced chemicals, apparently centered at the tubeworm tickets.…”

“…Siboglinids are known to tolerate very low sulfide levels and are able to utilize enormous quantities of sulfide or methane before concentrations peak at surface sediments (Schulze & Halanych 2003, Dando et al 2008, Sommer et al 2009). The high densities attained by Siboglinum at 0 to 1 meter sediments could well result in efficient sulfide utilization in San Clemente sediments, and inhibit the growth of bacterial carpets and its associated fauna.…”