This particular discovery doesn't back that assertion up very much, as it's an ocean floor biome that is dependent on nutrients from the surface, but there are deep ocean environments which are not. We know that it's possible for food chains supporting even complex multi-cellular life to be founded on chemosynthetic organisms subsisting on hydrothermal sulfide emissions or serpentinization reactions. Those sorts of conditions are likely to be fairly common throughout the Universe on a wide variety of bodies. Whether or not life can be bootstrapped and evolve into complex varieties within the constraints of such environments remains to be seen, but it's a tantalizing possibility.
