The species composition, abundance and vertical distribution of micronektonic cnidarians has been investigated in the upper 2800 m at Discovery Station 9969, located in the cold regime in the eastern Weddell Sea, Antarctica. In total 22 siphonophore and 20 medusan species were identified. Overall siphonophores were more abundant than medusae, but the latter usually contributed much more to the biovolume. On average, cnidarians contributed more than 50% to the total biovolume of each catch; and they contributed >70% to the combined total of all the samples. Despite the high water content of these animals, these large biovolumes meant that the cnidarians formed ∼25% of the total carbon in each catch. The possible impact of these gelatinous cnidarian populations on the ecosystem is discussed.