When studying shrimp feeding from hydro-thermal vents at the bottom of the ocean, biologists were surprised that the shrimps reproductive cycles followed seasonal patterns. far beyond the reach of?

I believe the correct answer to this question would be:

far beyond the reach of sunlight

Hydrothermal vents are usually located on the most bottom part of the ocean. A hydrothermal is created when there is a fissure in the planet’s surface underneath the ocean.