Question

Deep-Sea Hydrothermal Vent Communities

Deep-sea hydrothermal vents support diverse communities of organisms in the absence of sunlight. Three researchers discuss the primary source of nutrients that forms the base of these food webs.

*Researcher 1*
The base of the food web relies entirely on local chemosynthesis by endosymbiotic bacteria. These bacteria live inside specialized tissues of host organisms, such as tube worms and clams, and oxidize hydrogen sulfide ($H_2S$) emitted from the vents. The host provides the bacteria with carbon dioxide and oxygen, while the bacteria synthesize organic compounds directly for the host.

*Researcher 2*
Local chemosynthesis occurs but is insufficient to sustain the high biomass of vent communities. Instead, these ecosystems rely on the downward drift of organic detritus (known as 'marine snow') from photosynthetic organisms living in the sunlit surface waters. The rich organic matter settles to the ocean floor, serving as the main source of nutrients.

*Researcher 3*
The primary nutrient source is chemosynthetic but does not rely on symbiosis. Free-living, chemolithoautotrophic bacteria in the water column and on seafloor rocks form dense bacterial mats. Mobile grazing invertebrates (such as crabs and snails) feed directly on these mats. These grazers are then consumed by larger predators, distributing nutrients throughout the ecosystem.

Based on the passage, match each statement describing a nutrient delivery mechanism to the researcher who proposes it.