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