In my book series, there is a planet called Ryu 108 that is almost entirely a water world. It is the furthest planet from its star (a supergiant), and has a relatively cold-but-still-habitable climate for the most part.

What I am asking about is the tiny amount of landmass on this planet (around 150 square miles (388.5 square kilometers) of islands: 2 main ones and a few hundred tiny islands and islets). I wanted these areas to be very ecologically diverse even though they are very small in size, hosting differing biomes including boreal forests, temperate rainforests, mammoth steppes, cold deserts, geyser fields, bogs, redwoods, tundra, and volcanoes. How would I be able to fit all of these different biomes into such a small area and have some small civilizations develop here? Could I even do this at all?