Sanity check, please:
This page is a good example of the hierarchy, which interests me. I think the hierarchy begins with Characters (or Traits, or The Questions) and these go a few levels down and are then succeeded by Character States (or Trait Values, or The Answers). For instance:
Habitat, Substratum -> Characters
Soft, Coarse Sediments, Sandy Gravel -> Character States
For me as a data consumer, the distinction between these two types of terms is important. To describe a categorical data record, you need one of each. For building search interfaces, it is necessary to know which terms play which role. I think the terms should be labeled, possibly using the Concept Type field.
There is no mention of deep-sea habitat classifications here. We need to have these added. I will try to find a good reference that describes these but at the least we need to include:
Hydrothermal Vents Cold Seeps Mud volcanoes Cold-water coral reefs Sponge bed/aggregations Seamounts Manganese nodule beds Mid-Ocean Ridges Whale falls