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

Abstract

Nematode assemblages along the northern continental shelf of the Gulf of Mexico (GOM) were examined to understand the structure of the meiobenthic community in the area. Meiofauna were collected at 36–187m depths on the northern GOM continental shelf in 2013–2014. Sediment was collected from 37 stations with a multicorer and analyzed for nematode diversity, trace metals, and granulometry. Over 3800 nematodes were identified from 151 genera and 32 families. Cluster analysis revealed distinct nematode assemblages in the eastern study areas (Florida/Alabama) versus western areas (Louisiana/Mississippi) that corresponded with two different sediment profiles in the eastern and western Gulf shelf. These areas demonstrated higher levels of silt and aluminosilicate compounds in the west due to the outflow of the Mississippi River, and higher levels of sand fractions in Florida, far from the River outflow. Further, significant (SIMPROF) temporal changes were revealed by the cluster analysis, as the 2014 eastern nematode assemblages grouped together but separately from the 2013 eastern nematode cluster, though the collection methods and identification processes were identical. Conversely, the 2013–2014 nematode assemblages from the Louisiana/Mississippi sites grouped as one significant cluster. As nematode communities are known to correlate to areas of organic enrichment, trace metals were used as indicators of Mississippi River-derived silty sediments that have elevated levels of organic matter. The data show that nematode abundances at each site correlated positively with high levels of Aluminum and Zinc, near the Mississippi River outflow, as well as with high levels of silt+clay. Conversely, nematode densities correlated negatively with Calcium and Strontium, which are elevated in Florida. Nematode density was not related to water depth. The most abundant genera identified in the study were Sabatieria, Dorylaimopsis, Pselionema, Tricoma, and Halalaimus. This study will be useful in understanding the abiotic factors that influence the meiobenthic community and will facilitate future assessments of natural and man-made disturbances.