Gelatinous zooplankton of the Marshall Islands, Central Tropical Pacific: an inventory

Vast regions of the Central Pacific, inhabited by low-lying Micronesian nations, have been poorly studied for zooplankton. Atolls of the Republic of the Marshall Islands (RMI) have been surveyed before, during, and after the US nuclear weapons tests between 1946 and 1958, and gelatinous taxa were sporadically mentioned. Gelatinous zooplankton (GZ) were photographed during several thousand SCUBA dives between 2001 and 2016 at Kwajalein Atoll. Together with new recordings, the GZ species richness was reviewed for the entire RMI, which has the potential to become a model system for marine biodiversity research in data-poor Micronesia. Our survey resulted in 74, mostly holoplanktonic (74%), species, including nine hydrozoan medusae, 31 siphonophores, 14 scyphozoans, three cubozoans, three lobate ctenophores, eight appendicularians, one doliolid, and five salps. The species richness was low compared to census efforts from neighbouring Southeast Asian countries, hence being the first GZ assemblage characterisation for the broader oceanic region.