•Hydrothermal Vent Communities • Thermarces cerberus Hydrothermal vent discovery-1977 Alvin vent_chemistry2 • Do Vents Affect the Entire Ocean? The world’s oceans contain many chemicals other than water and salt. Where do these chemicals come from? Rivers carry some of the chemicals into the ocean. Hydrothermal vents supply others. When seawater seeps down into the ocean crust and is heated by the magma, it undergoes lots of chemical reactions. When the fluid rises up through the seafloor, it carries many new chemicals with it, such as copper and zinc. These chemical reactions also remove chemicals from the seawater, such as oxygen and magnesium. Here is a look at some of the many chemical reactions that take place. 1.Cold seawater sinks down through cracks in the crust. 2. Oxygen and potassium are removed from the seawater. 3. Calcium, sulfate, and magnesium are removed from the fluid. 4. Sodium, calcium, and potassium from the surrounding crust enter the fluid. 5. The fluids have reached their highest temperatures. Copper, zinc, iron, and sulfur from the crust dissolve in the fluids. 6. Hot fluids carrying dissolved metals rise up through crust. 7. The hydrothermal fluids mix with cold, oxygen-rich seawater. Metals and sulfur combine to form black metal-sulfide minerals. Hydrothermal Vents 1.Cold seawater sinks down through the crust. 2.O2 and K are removed from the seawater. 3.Ca, SO4, and Mg are removed from the fluid. 4.Na, Ca, and K from the crust enter the fluid. 5.Highest temperatures (350-400 oC), Cu, Zn, Fe, and H2S from the crust dissolve in the fluids. 6.Hot & acidic fluids with dissolved metals rise up through crust. 7.The hydrothermal fluids mix with cold, O2-rich seawater. Metals and sulfur combine to form metal-sulfide minerals: MnO2, FeO(OH), … plumecartoon •www.pmel.noaa.gov/vents Black & White smokers hydro_diagmain4 •Metals & O2 • •Diffuse flow of water •Silica and Anhidrite 2. The seawater continues to seep far below this point in the ocean crust. Energy radiating up from molten rock deep beneath the ocean floor raises the water's temperature to around 350-400°C. As the water heats up, it reacts with the rocks in the ocean crust. These chemical reactions change the water in the following way: All oxygen is removed. It becomes acidic. It picks up dissolved metals, including iron, copper and zinc. It picks up hydrogen sulfide. 3. Hot liquids are less dense and therefore more buoyant than cold liquids. So the hot hydrothermal fluids rise up through the ocean crust just as a hot-air balloon rises into the air. The fluids carry the dissolved metals and hydrogen sulfide with them. 4. The hydrothermal fluids exit the chimney and mix with the cold seawater. The metals carried up in the fluids combine with sulfur to form black minerals called metal sulfides. These tiny mineral particles give the hydrothermal fluid the appearance of smoke. Many factors trigger this reaction. One factor is the cold temperature of the seawater. A second equally important factor is the presence of oxygen in the seawater. Without oxygen, the minerals would never form. In white smokers, the hydrothermal fluids mix with seawater under the seafloor. Therefore, the black minerals form beneath the seafloor before the fluid exits the chimney. Other types of compounds, including silica, remain in the fluid. When the fluid exits the chimney, the silica precipitates out. Another chemical reaction creates a white mineral called anhydrite. Both of these minerals turn the fluids that exit the chimney white. pic6 Lec1Slide40 • Smoker chimney section smoker Hydrothermal Vent Distribution se0720196001 •Pink, western Pacific; green, northeast Pacific; blue, East Pacific Rise; •yellow, Azores; red, Mid-Atlantic Ridge; orange, Indian Ocean Figure 1. Map of known hydrothermal vent biogeographic provinces and major mid-ocean ridges. Provinces: Pink, western Pacific; green, northeast Pacific; blue, East Pacific Rise; yellow, Azores; red, Mid-Atlantic Ridge; orange, Indian Ocean. Vent Sites Ocean Vents Around the World Hot or molten rock (magma) beneath the ocean floor is the engine that drives hydrothermal vents. It heats the hydrothermal fluids, causing them to move upwards through the crust. Therefore, hydrothermal vents are found only in areas where there is volcanic activity and the magma is close enough to the surface to heat the fluids. Most of the vents scientists have discovered are along the Mid-Ocean Ridge. There are vents on the Loihi Seamount, the newest underwater volcano in the Hawaii chain. Vents are also found along some subduction zones. Vents can occur at any depth. Some are as deep as 3,600 meters. Others off the coast of New Zealand are only 30 meters deep. Vents are also found on land. Two of the most famous examples are the hot springs and geysers in Yellowstone National Park in the United States and on the North Island of New Zealand. Hydrothermal vent age estimates •Age •20-100 years •Decades •<10 years •< 6 months •Technique •sulfide dating •mollusk shells •heat loss •submersible observations Hydrothermal energy source •H2S + O2 à SO4 ++ H+ + ATP • •Chemosynthetic (sulfur oxidizing) •Thermophilic Bacteria (up to 120oC) •Hot, anoxic, sulfide rich water mixes with Cold oxygenated water •Hydrothermal Vents as origin of Life? • • • • Bacterial mat clams •www.divediscover.whoi.edu/i Bacteria from 120oC Lec1Slide43 •http://mollie.berkeley.edu/~volkman/ Vent biological communities •BACTERIA (Bacteria and Archea) •400 morphological invertebrate species –New species every 2 weeks during 25 years! •Evolutionary Origin –Derived from surrounding Deep Sea –Derived from Shallow Water species –Many evolutionary radiations at species level –Many vent taxa originated at other organically enriched environments (cold seeps and whale bones) •Vents as stable refugia from Global extinctions Cold Seeps •CH4 + O2 à CO2 + H20 +ATP •CH4 à CH3- + H+ +ATP •H2S + O2 à SO4 ++ H+ + ATP •Hydrocarbon reservoirs •“methane bubbling” •Continental shelves and Trenches •200 invertebrate species cold_s1 dscn0356b Whale skeletons & sunken logs •H2S + O2 à SO4 ++ H+ + ATP •Osteophiles •Potential ‘stepping stones’ for certain invertebrate vent species • ~AUT0008 ~AUT0013 Invertebrate food sources •Food chain based on sulfur-oxidizing bacteria •Symbiosis with Bacteria –Vestimentiferan tube worms –Vent Mussels and vent clams •Ingestion of Bacteria –Grazers (gastropod limpets and snails) –Filter Feeders (vent shrimp, polychaete worms, amphipods, anemones) •Predators –Ventfish, octopus •Scavengers –Crabs – Oceanic vent Biogeography •Atlantic vents •Vent shrimp • •Indian vents •Vent shrimp •Anemones •Pacific vent species • •East Pacific vents •Vestimentiferan worms •Alvinellid polychaetes Hydrothermal Vent (46Kb) •Vestimentiferan worms 364-13 •http://web.uvic.ca/%7Everenat/364-13.jpg Riftia •http://www.ifremer.fr/droep/Driftia.html UNDER5 tubeworms Lec1Slide38 • manahan5 dandelion •www.divediscover.whoi.edu/i •Vent Mussels (Bathymodiolus ) clams •www.divediscover.whoi.edu/i clams_new_site2low •Vent Clams • (Calyptogena) • •Vent Shrimp (Bresiliidae) crevettes •www.ifremer.fr/ shrimp shrimp%20adult rep Alvinellid worms mound2 alvinelle limpets%20and%20sulfide%20worms Vent limpets •http://web.uvic.ca/~abates/ ventabb16 clams •www.divediscover.whoi.edu/i ds_08 •Vent Crabs ventabb19 •www.senckenberg.uni-frankfurt.de/ • Thermarces cerberus • Ventfish (Thermarces cerberus) fish •www.divediscover.whoi.edu/i Periferic filter feeders anemonelg Larval dispersal between vents Vent Plumes 1986Megaplume •www.pmel.noaa.gov/vents/PlumeStudies tubeworm_1 Tubeworm spawning crustageposter •Ocean Crust Age Mid Atlantic Ridge iceland •http://faculty.washington.edu/lyn4/images/iceland.jpg East Pacific Rise Fig12 Spreading rate and Plume incidence PlumeIncidenceGlobal •www.pmel.noaa.gov/vents/PlumeStudies Fast and Slow spreading ridges se0720196003 •VanDover et al. 2002 (Science) Figure 3. (A) Schematic representation of a slow- to medium-spreading ridge system (e.g., Mid-Atlantic Ridge), including fracture zone (FZ) offsets and nontransform discontinuities (NTD). Active high-temperature venting is indicated by red triangles. Hydrothermal plumes (orange) are retained within steep-walled rift valleys. Distributions of larvae of vent taxa are indicated by blue dots. The large arrow signifies prevailing bottom-water current direction. Examples of potential biogeographic filters or conduits for northerly dispersion of larvae are as follows: (i) NTD offset is short, allowing effective dispersal, (ii) constricted and/or irregular NTD path hinders dispersal, despite favorable bottom current regional flow, (iii) dispersal between adjacent segments is aided by prevailing flow direction along interconnecting NTD, (iv) FZ links active segments, and exchange of propagules is relatively unrestricted, (v) barren segments and adverse flow direction constrain dispersal, and (vi) isolated community is prevented from wider dispersal by FZ and inactive adjacent segments. (B) Schematic representation of a fast-spreading ridge axis (e.g., East Pacific Rise); symbols as for (A). Note that hydrothermal plumes are not contained within rift valleys, there is a higher spatial frequency of venting, and there are no apparent topographic barriers to dispersal along axis, other than a major fracture zone offset Figure 11 •White et al. 2002 Electromagnetic emissions by vents Light organs in vent organisms lights_alvin_full •www.deepsea.com/ shrimp shrimp%20adult rep •Jinks et al. 2003 (SCIENCE) Notice how the deeper you go, the higher the boiling point rises. The reason lies in the increase in pressure. At sea level, the pressure equals one atmosphere. But for every 10 meters you dive, the pressure increases by one atmosphere. So if you were to dive to ten meters, the pressure would equal two atmospheres. A hydrothermal vent 2,500 meters deep experiences 250 atmospheres. How does this affect the boiling point? As the pressure increases, so does the boiling point. The boiling point of water may be 100 degrees at sea level, but it is much greater deep in the ocean. Vent community regulation EPR Pacific Lec1Slide37 •http://mollie.berkeley.edu/~volkman/ Vent community regulation Snake-Pit Mid Atlantic Ridge • Snakepit se4119868002 •Vent community regulation Indian Ocean Invertebrates of Central Indian Ridge hydrothermal vents. (A) Discrete boundary between shrimp (Rimicaris aff. exoculata, top left) and anemones (Marianactis sp., lower right). (B) Mussels (Bathymodiolus aff. brevior), shrimp, and anemones. (C) Hairy gastropods (Alviniconcha n. sp.) and brachyuran crabs (Austinograea n. sp.). (D) Brachyuran crabs and anemones. (E) Red turbellarian flat worms and shrimp [Chorocaris n. sp. (narrow-bodied) and R. aff. exoculata (wide-bodied)]. (F) Bristleworm (Archinome sp.) on shrimp molts. (G) Stalked barnacles (Neolepas n. sp.) and shrimp. (H) Anemones and shrimp molts. Vent community regulation •Physical factors –Temperature •Ecological factors –Competition –Larval supply –Predation –Ecological cascading – Keystone predators – clam2.jpg •http://www.pmel.noaa.gov/vents/nemo/index.html Lost City fissuresample flange2 Below temperatures of about 425°C (about 800° F), olivine is unstable in the presence of seawater and reacts to form the hydrous Mg-rich silicate mineral serpentine and an iron-oxide called magnetite. We refer to this process of hydrating mantle rocks as “serpentinization”. Serpentinization causes important changes to the physical state of the rocks and the chemical composition of the system, and produces important nutrients for microbial activity. During the formation of magnetite, part of the ferrous (Fe2+) iron in olivine is oxidized to ferric iron (Fe3+) to form magnetite. This change in the valency of iron consumes oxygen from the fluid and leads to a state that chemists call reducing conditions. As a consequence of the formation of magnetite, hydrogen gas (H2) is produced from the reduction of seawater during serpentinization. Seawater also contains carbonate ions (HCO3- or CO22-) and sulfate ions (SO42-) which can become reduced to form methane (CH4) and hydrogen sulfide (H2S) during the serpentinization process. The presence of the reduced species H2, CH4 and H2S in the fluids that seep out of the rocks provide important energy sources for different microbial species that seem to thrive around the Lost City structures. •Chemical Reactions A beehive of activity. Microbial niches in serpentinization- influenced environments at the Lost City hydrothermal field. (A) Exothermic serpentinization reactions within the subsurface produce fluids of high pH enriched in methane and hydrogen, as well as some hydrocarbons. (B) Environments within the warm interior of carbonate chimneys in contact with end-member hydrothermal fluids host biofilms of Methanosarcina-like archaea (green circles). These organisms may play a dominant role in methane production and methane oxidation within the diverse environments present in the chimneys. Bacterial communities within these biotopes are related to the Firmicutes (purple rodlike cells). These organisms may be important for sulfate reduction at high temperature and high pH. (C) Moderate-temperature (40° to 70°C) endolithic environments with areas of sustained mixing of hydrothermal fluids and seawater support a diverse microbial community containing Methanosarcina-like archaea, ANME-1 (a methane-oxidizing phylotype; blue rectangular cells), and bacteria that include AtlantisMassif_viewN •Olivine Density = 3.3 g/cm3 •Serpentine Density = 3.3 g/cm3 •40% Increase Volume Thinsection topofmassif-corals2photo top-of-massif-corals Lost City •Serpentinization –Olivine à Serpentine (hydration) – –Exothermic reaction 260°C – –Basic fluids pH 9-10 (CaCo3 precipitate) – –Fluids contain high CH4 and H2 – –30.000 of Age se0720196004 Fig. 4. Plot of PV, large-scale potential vorticity (see text for explanation). Values near the equator, where f is zero, are set to a constant. Color scale ranges from red, where the Coriolis effect is strongest, to blue, where topography dominates, and ignores the change in sign of f across the equator. Longitude is wrapped to display ocean basins clearly. In general, ocean currents tend to follow contours of PV, leading to longitudinal motions in the tropics (25°N to 25°S; white flow line illustrated only for Pacific) and circumpolar connections in the Southern Ocean. The Circumpolar Current (yellow flow line) spans the globe. Deep water formed in the northern North Atlantic flows into neighboring ocean basins in a system of swift, narrow, western boundary currents and interior zonal flows (red lines). In these western boundary currents, frictional terms in the equation of motion become important, allowing them to break the constraint of following PV. Isolated regimes of nearly uniform PV (pink and white stars) occur in ocean basins of the northern hemispheres.