Evidence for extensive methane venting on the southeastern U.S. Atlantic margin

Abstract

We present the fi rst evidence for widespread seabed methane venting along the southeastern United States Atlantic margin beyond the well-known Blake Ridge diapir seep. Recent ship-and autonomous underwater vehicle (AUV)-collected data resolve multiple water-column anomalies (>1000 m height) and extensive new chemosynthetic seep communities at the Blake Ridge and Cape Fear diapirs. These results indicate that multiple, highly localized fl uid conduits punctuate the areally extensive Blake Ridge gas hydrate province, and enable the delivery of signifi cant amounts of methane to the water column. Thus, there appears to be an abundance of seabed fl uid fl ux not previously ascribed to the Atlantic margin of the United States.

Methane seep ecosystem functions and services from a recently discovered southern California seep

“…This study highlights an important gap in continental margin research: namely, the lack of adequate measures or even descriptions of the ecosystem services methane seeps and other deep-sea chemosynthetic ecosystems provide (Thurber et al 2014). Given the seeming ubiquity of cold seeps along global margins and the rapid discovery of new sites Brothers et al 2013), ecosystem services of methane seeps might be significant at a regional scale. Future research at methane seeps that quantifies trophic subsidies to other margin habitats, documents possible habitat relationships with fishery species, clearly defines links between diversity and ecosystem function, or explores the role of seeps as potential sources of larvae to surrounding habitats could serve as first steps in relating methane seep ecosystem functions to continental margin ecosystem services.…”

“…; Brothers et al . ), ecosystem services of methane seeps might be significant at a regional scale. Future research at methane seeps that quantifies trophic subsidies to other margin habitats, documents possible habitat relationships with fishery species, clearly defines links between diversity and ecosystem function, or explores the role of seeps as potential sources of larvae to surrounding habitats could serve as first steps in relating methane seep ecosystem functions to continental margin ecosystem services.…”

The interaction of climate change and methane hydrates

“…Deepwater gas hydrates occur in marine sediments at water depths so profound (i.e., nominally greater than 1000 m; Figures 3 and 9) that ocean temperatures do not typically undergo dramatic change on time scales of centuries or more [Brothers et al, 2013;Plaza-Faverola et al, 2015;Ruppel, 2011a;Skarke et al, 2014]. Even if deep ocean temperatures were to increase by several degrees, which is larger than anticipated in any global warming scenario over the multicentury scale and comparable to the difference between the LGM and the present [Adkins et al, 2002], the ambient hydrostatic pressure regime means that gas hydrates in the shallow part of the sedimentary section at these locations would generally remain stable [Reagan and Moridis, 2008;Ruppel, 2011a].…”

Using sediment geochemistry to infer temporal variation of methane flux at a cold seep in the South China Sea

“…Modern seep activity can be detected through seabed observations, pore water analysis, methane anomaly detection, and many other methods (Borowski et al, 1996(Borowski et al, , 1999Borowski, 2004;Newman et al, 2008;Bayon et al, 2009bBayon et al, , 2011Mazumdar et al, 2012aMazumdar et al, , 2014Brothers et al, 2013Brothers et al, , 2014Lemaitre et al, 2014;Skarke et al, 2014), but temporal variations in methane flux in the past are not well constrained because it is difficult to select the appropriate indicators in quantifying and age determining the occurrence of seep activity. Consequently, little is known about the impact of methane seepage on the surrounding sediment environment in seep settings.…”