Deep-Sea BenthosMARS 345026 September, 2013MBARI Benthic ROVwww.st.nmfs.noaa.govhttp://www.sams.ac.uk/henrik-stahlBenthic Deep Sea(Nybakken 2001)“Typical”•Soft-grained sediments (oozes)•Derived from forams, diatoms, etc.•Accumulate at 1 cm/1000 y•Cold•Dark•Oxygenated• Abundant Inorganic Nutrients•Little food(Nybakken 2001)•Life is sparse•1 of 50 random sediment pictures shows an organism•Respiration rates are 1/100thof shelf sedimentsThe abyssal plain is the largest (areal extent) ecosystem on the earthPhotosynthesis and thus food supply varies by oceanic province – central gyres are poorest•FoodPelagic organisms get the first opportunityBenthic organisms get longer timeWhale Fall•Santa Catalina basin, 1200 m•Discovered in 1987 during Alvin dive•Revisited through 1995•Blue or Fin whaleabundant microbial mats>40,000 invertebrates6 species of bivalves8 species of gastropods23 species of polychaetes3 crustaceans1 brittle starAll flesh was goneClam zoneLiving on Whale Bones:Characteristics of Deep Sea Organisms•Filter feeders are few in number (<7% of species)•Also, herbivores and strict carnivores are few in number•Deposit feeders are common•Omnivores and scavengers are commonSea cucumbersPolychaete wormsBivalvesBrittle starsStarfishCrabsFishCompare to pelagic(Castro and Huber 2003)Larger than deep pelagicElongatedStreamlined(Castro and Huber 2003)Adaptations to ooze“Typical Deep Sea”•Abyssal plain•Fish adaptations(Nybakken 2001)“Atypical”•1977 Alvin dive by marine geologists•Searching for predicted “hydrothermal vents”•Surprising discovery of rich biological communitiesTube worms (Riftia)Giant clams (Calyptogena)MusselsCrabsSnailspolychaetesHydrothermal Vent CommunitiesWhat is the source of food???East Pacific RiseMid-ocean ridge, spreading center, plate boundaryHydrothermal vent communities(Castro and Huber 2003)H2S + 2O2H2SO4+ ATPChemosynthesisCO2+ H2O + ATP CH2O + O2•No digestive tract•Bacteria inhabit trophosome•Sulfide, oxygen, CO2delivered by worm•Carbohydrates released by bacteria3 Types of extracellularhemoglobinBind both O2and H2SThe H2S Problem:Cytochrome c oxidase is poisoned by H2SH2S outcompetes O2 for hemoglobin bindingSpecial hemoglobin:Binds H2S tighter than cytochrome c oxidaseDoes not interfere with O2bindingPhotosynthesis ChemosynthesisChloroplastsEnergyPlantFixed Carbon Tube wormsSulfide-oxidizingbacteriaHydrogen sulfideEnergysamedifferentThe energy for this system is not tied to sunlightH2S and many other reduced chemicals and metals are released from vents into oxygenated waterSource of hydrogen sulfide: Water mixes with vent fluidsHydrothermal Vent Communities•Specialized animals, many new species! •Chemosynthetic bacteria(Nybakken 2001)Colonization of Hydrothermal VentsVents are short-lived (1-2 decades)Vents are separated by thousands of kilometersThe habitat between vents is inhospitable (cold, no H2S)Question: How do animals survive to colonize new vents?(Nybakken 2001)Answer: Whale bones?•Bones are rich in lipids•Anaerobic metabolism (bacteria) produces H2S•Chemosynthetic bacteria colonize the whale bones•The bacteria are food for other organisms•Whale bones are “stepping stones”ATPCO2+ H2O + ATP CH2O + O2But debated:species overlap minorSmaller colonizationdistance for vent organisms“Atypical” 2Cold Seep Communities•1984 dive by petrologists•Searching for oil seeps in the Gulf of Mexico•Another discovery of rich biological communitiesMethane seeping alsoBacteria live in gills of musselsChemosynthesis based on CH4BrineMussels with chemosynthetic bacteriaAnother tubeworm:Lamellibranchia• Stained with chitin dye in 1994• Measured new growth in 1995, 1997, 1998• Individuals were 175-250 years old• Growth rates vary tremendously“Base of Hydrate Stability Zone”Methane HydratesCold Seeps•Brine (high salt) “pools” •Methane-based chemosynthesis•Long-lived tube
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