How do biological communities at deep-ocean hydrothermal vents migrate between vents?
I did some research on the topic and came accross this paper by Johnson et al. I am not a zoologist, so everything I write here is taken from the references paper.

The authors used genetics to estimate gene flow between different populations of limpets Lepetodrilus fucensis which is considered to be an endemic hydrothermal vent animal. They used a mathematical demographic model "isolation with migration" to estimate the migration of the animals across different biotopes.

The vents are distributed along the ridge segments and can be seen as small islands isolated by tens of kms from each other along the same ridge segment and thousands of kilometers between distinct ridges.

The results suggest that there is certain migration between the adjacent vent locations, that means that the flora of one vent can indeed survive the distance towards the next most proximal vent. 



So, from now on is my pure speculation. Since the distance between single vents along the same ridge segment seems not be to so high we can suggest that these organisms are capable to resist the pressure and temperature on the ocean bottom while travelling from one vent to another...