Kinorhynch assemblages in the Gulf of Mexico continental shelf collected during a two-year survey

Abstract Kinorhynch assemblages along the northern continental shelf of the Gulf of Mexico were examined to better understand the distributional trends of this understudied group of meiofauna. Samples were collected with a multicorer from 37 stations at 36–187 m depths in the years 2013 and 2014. Sediment was collected and the animals were isolated from the mud using Ludox® centrifugation. Kinorhynchs were isolated with a stereomicroscope and the adult animals were identified to species level either by light microscopy or scanning electron microscopy. A total of 1328 animals were recovered, including juveniles and adults. After processing, 812 adults were identified and classified to 6 families, 12 genera and 32 species. The identifications were used to explore relationships among the species, and to determine if the animal assemblages at each site revealed relationships to each other. Sediment characteristics were determined at each site, to reveal if abiotic factors correlated with animal densities. Cluster analysis revealed distinct assemblages in Louisiana versus Florida sediment. The highest abundance of kinorhynchs was found in western sediments in Louisiana, which are characterized by higher levels of silt and clay, and aluminum-associated trace metals. These sediment characteristics indicated a strong influence from the outflow of the Mississippi River. The most abundant species were Echinoderes bookhouti , E . skipperae , E . augustae , and E . spinifurca , which comprised 79% of the identified animals. This was the first kinorhynch survey to cover a geographic area as large as the northern Gulf of Mexico, over multiple years, and to statistically analyze the animals in relation to their sediment type.