30 There are, however, certain difficulties with this interpretation. For example, some of the large sedentary organisms associated with vents are also found at ordinary deep-sea temperatures many meters from the nearest hydrothermal sources. This suggests that bacterial 35 chemosynthesis is not a sufficient source of nutrition for these creatures. Another difficulty is that similarly dense populations of large deep-sea animals have been found in the proximity of smokers vents where water emerges at temperatures up to 350 C. No bacteria can survive such 40 heat, and no bacteria were found there. Unless smokers are consistently located near more hospitable warm-water vents, chemosynthesis can account for only a fraction of the vent faunas. It is conceivable, however, that these large, sedentary organisms do in fact feed on bacteria that 45 grow in warm-water vents, rise in the vent water, and then rain in peripheral areas to nourish animals living some distance from the warm-water vents.
Nonetheless, advection is a more likely alternative food source. Research has demonstrated that advective 50 flow, which originates near the surface of the ocean where suspended particulate matter accumulates,transports some of that matter and water to the vents.Estimates suggest that for every cubic meter of vent discharge, 350 milligrams of particulate organic 55 material would be advected into the vent area. Thus, for an average-sized vent, advection could provide more than 30 kilograms of potential food per day. In addition, it is likely that small live animals in the advected water might be killed or stunned by thermal and/or chemical 60 shock, thereby contributing to the food supply of vents.
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