Data from: Marine biodiversity at the end of the world: Cape Horn and Diego Ramírez islands

The vast and complex coast of the Magellan Region of extreme southern
Chile possesses a diversity of habitats including fjords, deep channels,
and extensive kelp forests, with a unique mix of temperate and
sub-Antarctic species. The Cape Horn and Diego Ramírez archipelagos are
the most southerly locations in the Americas, with the southernmost kelp
forests, and some of the least explored places on earth. The giant kelp
Macrocystis pyrifera plays a key role in structuring the ecological
communities of the entire region, with the large brown seaweed Lessonia
spp. forming dense understories. Kelp densities were highest around Cape
Horn, followed by Diego Ramírez, and lowest within the fjord region of
Francisco Coloane Marine Park (mean canopy densities of 2.51 kg m-2, 2.29
kg m-2, and 2.14 kg m-2, respectively). There were clear differences in
marine communities among these sub-regions, with the lowest diversity in
the fjords. We observed 18 species of nearshore fishes, with average
species richness nearly 50% higher at Diego Ramírez compared with Cape
Horn and Francisco Coloane. The number of individual fishes was nearly 10
times higher at Diego Ramírez and 4 times higher at Cape Horn compared
with the fjords. Dropcam surveys of mesophotic depths (53-105 m)
identified 30 taxa from 25 families, 15 classes, and 7 phyla. While much
of these deeper habitats consisted of soft sediment and cobble, in rocky
habitats, echinoderms, mollusks, bryozoans, and sponges were common. The
southern hagfish (Myxine australis) was the most frequently encountered of
the deep-sea fishes (50% of deployments), and while the Fueguian sprat
(Sprattus fuegensis) was the most abundant fish species, its distribution
was patchy. The Cape Horn and Diego Ramírez archipelagos represent some of
the last intact sub-Antarctic ecosystems remaining and a recently declared
large protected area will help ensure the health of this unique region.