Megafauna community structure at the Blake Ridge and Cape Fear Diapir seeps

The 2012 Okeanos Explorer seep-seeking expedition off the East Coast of the United States located 3 new methane seep communities using AUV Sentry. These 3 sites are all within 240 m of the known seep on the Blake Ridge Diapir. Additionally, a seep was discovered on the Cape Fear Diapir, ~55 km NNE of the Blake Ridge Diapir. Systematic photo surveys of seep organisms using Sentry reveals a consistent relationship among biomass dominant organisms, bathymetric features, authigenic carbonates, and areas of disrupted sediment. Overall, Bathymodiolin mussel beds at the Blake Ridge Diapir seeps are clustered around areas of irregular bathymetry – pockmarks and mounds – where we infer focused seepage. Vesicomyid clams are more scattered than the mussels, and are often located on stretches of flat seafloor around the mussel beds. Analyses were run in ArcGIS to examine the correlation between bathometric features and this concentric bivalve community structure. At the Cape Fear Diapir seep, mussels were absent and bacterial mats were more extensive. Further ArcGIS analyses were conducted on major taxa to calculate density and abundance among the five different seep communities. Nearby non-seep organism presence was used to determine if abundance changed with increasing proximity to a seep, indicating whether the seeps served as bio-hotspots for mobile non-seep endemic species. Cumulatively, these data will establish a baseline for the megafauna populations on the Blake Ridge and Cape Fear Diapirs. In 2014, a return cruise to these sites, utilizing AUV Sentry and ROV sampling, is planned. Changes in faunal diversity, abundance, density, and location during the two-year interim can be used to calculate the community dynamics at and around these seep sites. Further, the large size of the Bathymodiolin mussels allows photographic distinction among juveniles, live adults, and dead adults; comparing the 2012 and 2014 populations of mussels will provide insight into growth rates and population shifting.

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First Name: 
Jamie
Last Name: 
Wagner
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1-919-818-1316
Affiliation: 
Duke University Marine Lab, Beaufort, NC, USA
First Name: 
Alix
Last Name: 
Jacobson
Affiliation: 
Duke University Marine Lab, Beaufort, NC, USA
First Name: 
Elizabeth
Last Name: 
Hoerauf
Affiliation: 
Duke University Marine Lab, Beaufort, NC, USA
First Name: 
Cindy
Last Name: 
Van Dover
Affiliation: 
Duke University Marine Lab, Beaufort, NC, USA
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Biogeography
Distribution and abundance
Abstract ID: 
CBE5-173