METHANE SEEPS Sources of seepage Distribution Geochemistry Characteristic epifauna Environment animal interaction Faunal Nutrition WHAT ARE SEEPS Cold seeps are regions of the sea floor where reduced compounds mainly methane and sulfides are released into sediments Through chemosynthesis activities of chemoautotrophic bacteria these compounds support rich assemblages of organisms sometimes distinct from those in surrounding sediments 1 Types of seeps brine Gulf of Mexico Mediterranean petroleum asphalt Guaymas G of Mexico gas hydrate G of Mexico E Pacific subduction dewatering NE NW Pacific mud volcanos Gulf of Cadiz Haaken Moseby erosional turbidity currents Laurentian Fan biogenic thermogenic methane WHY ARE SEEPS IMPORTANT Discovery of methanotrophic symbioses Multiple sources widespread distribution Linkages to non seep faunas vent faunas Clues to past climate change through methane release On margins subject to human exploitation 2 20 years ago we believed hydrothermal vents were the only deep sea reducing environments First Seeps Florida Escarpment Paull et al 1984 3 Distribution of active blue and fossil yellow methane seeps Associated with brine hydrocarbon methane Some Locations of Deep Sea Seeps Florida Escarpment 3270 m Louisiana Slope Gulf of Mexico 180 900m Laurentian Fan Grand Banks W Atlantic 3800 3900 m Blake Ridge W Atlantic 2155 m Barbados mud volcanoes 1700 m and trench 5000m Cascadia subduction zone 2030 m 1000 m 600m OR Northern CA off Eel R 300 550 m Monterey Canyon 600 1000m Guaymas Basin 1550 m Costa Rica mud volcanos 3000 m Peruvian Subduction Zone 2630 5137 m Aleutian Subduction zone Gulf of Alaska 4000 5500m Japan Subduction zone Sagami Bay 900 1200m Nankai Trough 3800 4020 m Black Sea 35 785 m Hakon Mosby Mud Volcanoes Iceland Greenland Sea E Mediterranean Congo Fan Africa 4 Gulf of Mexico 600 800 m Bush Hill Brine Pool FL Escarpment 3290 m Aleutian Trench 4445 m Japan Trench 6370 m How are methane seeps similar to or different from hydrothermal vents Similarities High animal biomass large body size Trophic reliance on reduced compounds symbiosis Low species richness high dominance Similar megafaunal families genera Localized patchy distribution Dissimilarities Sediment ecosystem vs hard substrate Few species in common higher species richness at seeps Longer local persistence More widespread 5 Vents and seeps share only a few species but many genera Fluid flow rates vary between and within seep sites The CAT meter uses the dilution of a chemical tracer to measure flow through the outlet tubing at the top of the chamber A tracer solution of similar density but different composition than the seep fluid is injected at a constant rate by two osmotic pumps into the water stream as it moves through the outlet tubing Fig 2 These same pumps withdraw a sample of the seep fluid tracer mixture from downstream of the tracer injection port giving a serial record of the tracer dilution 6 Tryon et al 2001 2002 Flow rates vary across habitats OR Clambed OR Microbial mat Data from M Tryon SIO Microbial mat positive flow Clam bed variable flow Tidal influence on seepage at great depth Aleutian Trench 4445 m Key microbially mediated geochemical interactions Sulfide oxidation Free living bacteria Syntrophy Anaerobic Methane oxidation Methanogenesis 7 Archaea Methane oxidation CH4 2 H2 O to CO2 4H2 Sulfate Reduction H 4H2 SO4 2 to HS 4 H2O Total Process CH4 SO4 2 to HCO3 HS H2O Boetius et al 2000 Nature Archaea Probe BA2H11 932 Black Sea Reefs 5 m SRB Probe DSS658 ANME Hydrate Ridge Guaymas Basin AOM consortia all around the world Gulf of Mexico Haakon Mosby Black Sea Congo Projekt MUMM Boetius et al MPI 8 Carbonate precipitation mediated by AOM is a common feature at seeps Carbonate slabs N California 520 m Costa Rica Seeps Carbonates at Seeps Substrate for reproduction Neptunia amianta Active carbonate precipitation Substrate for refuge 9 Characteristic Epifauna Vestmentiferans Pogonophorans Gulf of Alaska 4440 m Gastropods Vesicomyid Bivalves Modiolid Mussels C soyae Japan 10 Other Bivalves Solemyidae 10 5380m Thyasiridae 100 7430 m Thyasira Acharax Solemya Conchocele Lucinidae Lucina Lucinoma Lesser sulfide requirements Deep burrowing Other Taxa Gastropods Astyris Cladorhizid Sponges Barbados methanotrophic Provanna Sponges Aplacophorans Ice worms Hesiocaeca 11 Common Macrofauna Ampharetidae 0 3 mm Hesionidae Dorvilleidae single species densities of 10 000 100 000 ind m2 Amphipoda Oligochaeta Capitellidae Polynoidae Common Meiofauna Nematoda 0 042mm Xyalidae Linhomoeidae Chromadoridae Cyatholaimidae Gnathostomulida Foraminifera Fursenkoina Bolivina Epistominella Cheilostomella Globobulimina ADAPTATION Body elongation Flower Garden Lg diameter Monterey Bay 906 m Symbiosis North Sea Pockmarks Astonema sp 12 Gas Hydrates Stable at 450 900 m Hydrate Ice worms Hessionidae Hesiocaeca methanicola 2500 ind m2 2 4 cm 13C 24 to 25 Mobile Scavengers Brachuran crabs Alvinocarid Shrimp isopods Asteroids hagfish 13 New Discoveries Yeti Crab Costa Rica Kiwanidae Bacterial Mat Sulfide oxidizers Heterotrophs Vertical Distribution of Bacterial Filaments Eel R sediments 500 m Depth cm 0 to 1 cm 1 to 2 cm Non Seep Clambed 2 to 5 cm Microbial Mat 5 to 10 cm 0 5 10 15 20 25 Number Per Core 14 Alaska Kodiak Seep Upper Aleutian Trench 4445 m Calyptogena phaseoliformis NEW DISCOVERIES IN THE E PACIFIC Aleutian Margin Unimak Island 2004 Expedition searching for manifestation of 1946 tsunami http www lib utexas edu maps historical aleutians 1942 43 jpg Vesicomya Beds 3267 m Carbonate Reefs Pogonophoran Fields 15 Hydrate Ridge Oregon Bacterial Mats Monterey Bay Seeps Bacterial Mat Clam bed 16 Asphalt Seeps Tar Campeche Basin Gulf of Mexico 2005 Fluid Studies Costa Rica a fore arc margin 1000 m Kevin Brown Mike Tryon SIO Constrain fluid sources measure fluid flux rate of elemental loss 17 Chile Margin Seeps 2004 7 18 Lamellibrachia sp Vestimentiferan tube worm Chile Margin Seeps 850 m 5 species symbiontbearing bivalves Gas hydrate Carbonate chimneys Abundant non chemosymbiotic fauna New Zealand Wairarapa Site III Bacterial Mat and Ampharetid Bed 19 Angola Basin W Africa 3150 m Haaken Mosby Mud Volcano 1250 m HM MV Courtesy A Vanreusal 20 Microhabitats at HMMV concentric structure with highly gas saturated sediments large gas plumes caused by methane emissions in the central zone not microbially oxidized strong flow BACTERIAL MATS surrounded by filamentous sulfide oxidizing bacterial white mats