Passage:
While both hydrothermal vents and cold seeps support unique chemosynthetic ecosystems independent of sunlight, their physical environments and biological dynamics differ. Hydrothermal vents, typically found along mid-ocean ridges, are characterized by high-temperature (often exceeding ), mineral-rich fluids venting violently from the crust. In contrast, cold seeps occur along continental margins, where lower-temperature fluids containing hydrocarbons like methane and hydrogen sulfide diffuse slowly through seafloor sediments. A primary biological distinction lies in the role of symbiotic relationships: hydrothermal vent ecosystems are heavily dominated by giant tube worms (*Riftia pachyptila*) that lack a digestive tract and rely entirely on endosymbiotic bacteria to oxidize sulfide. Cold seep communities, conversely, are typically dominated by vesicomyid clams and bathymodiolin mussels. While these seep bivalves also harbor symbiotic bacteria, they retain a functional digestive tract, allowing them to supplement their chemosynthetic diet by filter-feeding on organic matter suspended in the water column—a capability entirely absent in the vent tube worms.
According to the passage, what is an explicitly stated difference between the biological capabilities of the dominant organisms found at cold seeps and those found at hydrothermal vents?
- AWhile hydrothermal vent tube worms depend on endosymbiotic bacteria to oxidize sulfide, cold seep bivalves survive without chemosynthetic endosymbionts by relying solely on filter-feeding of organic matter suspended in the water column.
- Unlike the tube worms dominant at hydrothermal vents, which rely exclusively on endosymbiotic bacteria due to their lack of a digestive tract, the dominant bivalves at cold seeps possess a functional digestive system that enables them to supplement their nutrition via filter-feeding.Answer
- CThe bivalves dominant in cold seeps reside in lower-temperature environments along mid-ocean ridges, whereas the tube worms dominant in hydrothermal vents are restricted to high-temperature fluids along continental margins.
- DAlthough both ecosystems rely on chemosynthesis, hydrothermal vent tube worms must actively filter-feed on organic matter to supplement their diet, whereas cold seep bivalves rely entirely on endosymbiotic bacteria to process diffused hydrocarbons.