primary production in the depths
Though photosynthesis cannot occur in the deep, there is another form of nutrient production that takes its place at hydrothermal vents. Here, there are hot upwellings of dissolved chemicals and minerals that form towering chimney structures on the sea-floor, and release heated minerals from deep within Earth into the ocean. The chemicals expelled within the superheated vent fluid would be toxic to us humans. But to the life here, they are vital, containing nutrients that bacteria are able to convert to energy in a process that mirrors the conversion of sunlight during photosynthesis.
In place of Photoautotrophs, we find Chemoautotrophs. In place of plants and plankton, there is bacteria. In place of photosynthesis, chemosynthesis. The bacteria are the primary producers, a major source of nutrients for the deep sea ecosystem.
Like manatees grazing sea-grass in the shallows, there are grazers here too. Bottom-feeders, like limpets and shrimps, graze on the microbial mats. Yeti crabs farm colonies of the bacteria on their legs as a source of food. These creatures, that rely on the bacteria for food, are the deep ocean’s primary consumers.
Predators at the vents, such as crabs, eels and octopuses, are the secondary consumers. But here’s where things get interesting. Though organisms at these isolated vent ecosystems cannot stray from their respective habitats, nutrients are still cycled between communities. The creatures here are demersal, meaning they live on or near the sea floor. They may be confined here, relying on the bacteria and unable to survive away from the vent ecosystem, but a number of other processes contribute to the transfer of chemical energy from vents to the rest of the open ocean.
The first of these processes involves visitors to the vents. From hagfish to deep sea skates, these are creatures that can survive away from the vents, but must seek out these hotspots of life in order to feed, or lay their eggs.