Regarding the tree in this question, what kind of life forms would be possible if this tree were the only solid structure above water on this 50% of earths gravity, water planet? No land, just a continental sized tree, with vertical branches, reaching a height of five hundred feet. The 'ground' is floating on top of ocean, and is the trunk of the Bladetree, winding to and fro along its own body, Averages of width is five hundred yards, and the height of horizontal trunk, which is its thickness, is at minimum one hundred feet. The roots feed like coral, except for the mineralized ocean water.
Remember also that the rooted and rootlets, all are very large, so the surface area, of just the root system, is astronomical.
The root system, is much like that of the Seaweeds, of Earth.
At high noon, (same cycle of that of Earth, concerning the tilt, and rotation, and travel around the sun.) the huge areas between the spiraled rings are at minamum, about 300 yrds wide, so the surface areas exposed to sun are relatively balanced, compared with areas, not recieving sun at all, so it looks like the enviroment, will support, life forms of both kind. That is to say, that it will support sun energized life forms, and the chemical, and or minerals energized life forms.
Much like the Banyon, is the root system growth, to anchor the whole structure, but yet, the roots are very elastic, and will stretch, thus is the part of system, in which fish and other organics, are used in the Bladetrees, diet, that is to say through the roots.
This species, has many properties of Algae. Remember, low gravity, and same distance, and size of Earth's sun, is this planet's sun.
Let me give the planet a name of Nibaru, after the mysterious planet X, that science and goverments are trying to keep a secret. (my opinion)
Yes there is a special catch here.... God has created everything, so it is unique, and will have an important role, in this enviroment. The aquatic, and or Atlantean, like people, ( having webed feet, and hands, and gills, and lungs to breath air. Maintainers, managers of Bladetree, to keep it strong, and healthy.
this tree would be mostly above water, but at the horizontal spiral, is the main stemroot, traveling down, and anchoring at the Oceans bottom, also, the outer ending of the spiraled trunk, is also rooted, but this root, grows, and dies, as the outer end continues to grow. All along the trunk, which again is on average width, five hundred yards, are covered in decaying branches, leaves, and other types of vegetation, so in essence, this continentally sized tree, supports life, much the same way, the earths outer crust does. There not only is life going on above, but also the underneath. There are places completly darkened by the floating trunk above.