Hydrothermal Vents and their Communities
Questions about Hydrothermal Vents
Who are the dominant primary producers? How is their C, N, P transferred? Basically everything...
What happens at the oxic/anoxic interface?
A low-complexity community of chemosynthetic (straight, abundant) and heterotrophic (curved, red, sparse) bacteria attach to the basalt and establish a biofilm. When chemosynthetic bacteria oxidize sulfur species, they mobilize heavy metals, increasing their toxicity. Bacteria in biofilms produce ESPs (extracellular polymeric substances), which sequester heavy metals, reducing their toxicity. Heterotrophic bacteria actively detoxify heavy metals. Colonizing bacteria are metabolically versatile and can use multiple energy sources and terminal electron acceptors. Whatever that means.
Sea Floor Depth
Controlled by Thermal Subsidence
Metal-Rich Sediments
Created by hydrothermal vents systems; makes hydrothermal vents at least vaguely interesting to geologists
Convection
Created by water flow through the crust; wasn't until 1977 that this was confirmed by direct observation (Kathleen Crane!!!!)
Hydrothermal Vent Communities
First identified in 1977; organic source 'marine snow;' vary from location to location; popular organisms are tube worms, shrimp, mussels, amphipods, anemones, etc.
Mid Ocean Ridges
Highest internal heat flow on the globe
Chemosynthesis
Hot water gushing from hydrothermal vents is saturated with dissolved chemicals; bacteria absorbs hydrogen sulfide and carbon dioxide from vent water and oxygen from seawater; bacteria use energy released by oxidizing sulfur to make organic molecules; bacteria grow and reproduce, and are eaten or hosted as internal symbionts by other animals
Hydrothermal Vent Fluid
Hot, reducing conditions (H+), high metal
Iron-Sulphur World Theory
Life originated at deep sea vents; catalytic transition metal, iron, centers; heat and pressure facilitate catalytic centers catalyzing autotrophic carbon fixation pathways
Sources of Earth's Interior Heat
Radioactive decay and remnant primordial heat from the Earth's formation
Conduction
Theoretically accounts for exponential decay of heat flow away from mid-ocean ridges, but misses non-conductive heat loss relative to actual measurements of heat flow
Measurement of Heat Flow
Thermal conductivity is measured in a lab; heat flow is calculated using Fourier's equation; q = -ku where q = heat flow, k = thermal conductivity, and u = temperature gradient