Minecraft wiki entry for JSON_format, associated text: Any biomes in the category ocean are considered part of the ocean temperature category; other temperature categories are controlled by the biome's temperature value. This means that biomes in the ocean category should typically be placed near each other.
Biomes in the categories ocean and river play the underwater music instead of their normal music when the player is underwater.
Zombie sieges and patrols do not spawn in biomes in the category mushroom.
Rabbits spawning in biomes in the category desert always have the desert skin, unless they are in a biome with precipitation set to snow.
Mobs in the water_ambient category spawn much less often in biomes in the category river.
Ocean monuments do not spawn in any biome which isn't in the category ocean or river.