The oceans were hit the hardest by the Holocene extinction event. Algae blooms and rapid acidification absolutely decimated the once thriving oceans. But as always, life goes on and the oceans recovered.
Some of the most productive ecosystems are the stormraft fleets. These are found in the North and South Atlantic ocean gyres, where calmer waters keep the whole ecosystem from literally falling apart. Stormrafts are large floating rafts made from clumps of sargassum, other types of seaweed and storm debris like driftwood which holds the entire structure together.
Northern stormraft fleets rely on the gulf stream to bring in driftwood while southern fleets rely on West African monsoons and South American storms as well as the Amazon to bring in debris. Debris gets lodged inside a sargassum clump and more and more debris and sargassum gets stuck together until it eventually makes a giant structure. The largest and oldest stormrafts can reach up to about half a mile in diameter. Some are thick and strong enough to support multiple decent sized animals at once, a characteristic that allowed stray stormrafts that drifted south to carry multiple species to Antarctica.
Stormraft fleets are ideal for many species. The biome contains an abundance of endemic fish, molluscs, arthropods, other invertebrates, mammals and birds, which feast on the abundant and near endless amounts of food provided by the rafts. Many other species choose to rear their young here as there is enough food to insure a high chance of survival.