Academic Reading: Hệ sinh thái hóa tổng hợp dưới đáy biển sâu (6 câu)

Prior to 1977, marine biologists widely assumed that life on the abyssal ocean floor, more than two kilometres below the sunlit photic zone, consisted solely of sparse scavengers subsisting on organic detritus drifting down from surface waters. That consensus collapsed when the research submersible Alvin surveyed the Galapagos Rift and encountered dense colonies of giant tube worms, blind vent shrimp, and ghostly eelpout fish clustered around black smokers discharging mineral-laden water at temperatures exceeding 350 degrees Celsius.

Unlike terrestrial forests or shallow coral reefs driven by solar radiation, hydrothermal vent food webs depend exclusively on chemosynthesis. Cold seawater percolates downward through fractures in the oceanic crust, where it is superheated by underlying magma chambers and leaches hydrogen sulfide, methane, and dissolved iron from surrounding basalt. When this superheated plume erupts back into near-freezing bottom water, chemoautotrophic bacteria oxidize the hydrogen sulfide to synthesize organic carbon compounds.

The adult giant tube worm Riftia pachyptila possesses neither a mouth nor a digestive tract; instead, its body cavity houses a specialized organ called the trophosome, packed with billions of symbiotic sulfur-oxidizing bacteria. The worm's bright red gill plumes absorb oxygen and hydrogen sulfide from the vent water and transport both gases via specialized hemoglobin molecules to the internal bacteria, which in turn supply the host worm with fixed carbon nutrients.

Because individual hydrothermal vents remain active for only a few decades before tectonic shifts seal their subterranean conduits, vent species must disperse larvae across hundreds of kilometres of barren basalt to colonize newly formed fissures. While researchers have tracked larval transport along fast-moving deep ocean currents, the precise chemical cues that trigger free-swimming larvae to settle at a new vent site remain unverified.