Piggybacking on the previous “Reef World” questions.
Let’s talk Flora and how it adds to life and the environment on Reef World.
The entire planet is mostly covered in shallow ocean, but not completely. There are some depths, but the tectonic activity is pretty much done. There is one last massive Olympus Mons type volcano spewing out the planets remaining inner heat, and the core has slowed down and become a large nickel iron ferro-magnet.
Free roaming islands of Pumice float around closer to the volcano, but they don’t last long. Even though unknown substances within the pumice islands (we’ve taken to calling it Wavnium) keep them afloat longer they still crumble apart after enduring months of rough seas. But during their time the Wavnium makes them quite large before they fall apart. This gives them the “ability to absorb [and distribute] many potentially advantageous elements/compounds. For at least these reasons, astrobiologists have hypothetically proposed pumice rafts as an ideal substrate for the origin of life” (https://en.wikipedia.org/wiki/Pumice_raft).
The reef throughout the planet benefit from this. These alien version of Coral create Reef that are more robust than Earth counterparts. “Sea grasses live in between the coral reefs, and they transfer nutrients to the coral. Their roots are adapted to keep the plant in place during strong ocean currents. When the sea grass dies it helps to create future plant growth. Mangroves grow [on and up from] the Coral Reefs. They grow above the sea water, and their roots protect from the sediment overpowering the coral (https://coralreefbrawner.weebly.com/plant--animal-adaptations.html).
There are areas of Sargasso, and Kelp forests as well, in competition with the Reef and Mangroves.
"A continual drizzle of dust falling from planetary rings seeds the oceans with ample nutrients." We theorize there may have been a small moon in a very low orbit that crumbled apart just below the Roche limit some time ago (potential source of Wavnium?).
The air on reef world is breathable because there are cyanobacteria and multicellular organisms like the Coral, and fish equivalents. These Mangrove forests are also part of producing air.
p.s. The gravity of the planet is lower than Earth but greater than Mars, and well within the escape velocity to retain an atmosphere and oceans.
Is this flora set up possible, and beneficial to habitability, both human and/or native?