Passage:
For decades, biological oceanographers assumed that deep-sea benthic communities relied exclusively on organic detritus drifting down from sunlit surface waters—a phenomenon known as "marine snow." However, the 1977 discovery of thriving ecosystems around hydrothermal vents challenged this paradigm by revealing chemosynthesis, wherein microbes convert chemical energy from vent fluids into organic matter independent of sunlight. While some marine paleontologists initially posited that these vent ecosystems functioned in complete isolation from surface dynamics, recent geochemical analyses of vent fauna shells have revealed trace isotopes of surface-derived carbon. This evidence indicates that while chemosynthesis underpins local primary production, deep-sea vent communities still interweave surface-derived nutrients into their trophic webs. Thus, recognizing hydrothermal vents as partially integrated into global carbon cycles rather than wholly isolated refuges provides a more accurate model of oceanic energy flow.
In the context of the passage as a whole, the statement that some marine paleontologists posited vent ecosystems functioned in complete isolation serves primarily to:
- introduce an opposing perspective that the author qualifies using recent geochemical evidence.Cevap
- Bstate the central thesis that the author proves throughout the remainder of the passage.
- Cdescribe a factual observation directly resulting from the 1977 discovery of chemosynthesis.
- Dsummarize the ultimate conclusion drawn from geochemical analyses of vent fauna shells.