Caves

Caves are under-surface biomes that usually have very little life within them, and a succession stage of 1. Caves can be water or land biomes. The list of cave biomes is almost complete.

River Caves

Occurs: on the sides of mountains
Resources: rainfall, snowmelt
Elevation: Approximately 5000 feet upwards - I will revise this sucker, but it's relative to latitude.
Climate: high temperatures are up to 10 C. great temperature variation between day and night
Topography: sloped ground, poor soil
Secession stage: 2
Autotroph niches: carnivores and herbivores up to midsize
Heterotroph niches: up to midsize. (small trees/shrubs are included.)
Other: All organisms must be adapted to a thinner atmosphere, meaning less oxygen or whatever your critter breathes. High winds probable.

Undersea Caves

Occurs: underwater, in the ocean near land
Resources: none
Elevation: 0 to -100 m below sea level
Climate: cool to warm, depending on climate above water
Topography: these caves are sometimes freshwater caves that ran into the ocean, but can also be lava tubes
Biodiversity: 1
Autotroph niches: none, except at entrance(s)
Heterotroph niches: tiny to midlarge carnivores/omnivores/detrivores
Other: more permanent residents than a river cave, again, more visitors than permanent residents

Blue Hole

Occurs: near sea level
Resources: possible fresh water
Elevation: opening @100m above to 50 m below sea level
Climate: cool, usually anoxic at a certain depth
Topography: basically a huge cylinder cut out of the earth by limestone dissolving- requires flat terrain
Biodiversity: 1
Autotroph niches: small/tiny floating plants
Heterotroph niches: tiny to small herbivores/carnivores/omnvores
Other: only bacterial life in the anoxic zone. May have visitors from surrounding environment.