Crustacean assemblage structure over the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge collected during the 2009 Henry B. Bigelow expedition

Abstract

The Charlie Gibbs Fracture Zone (CGFZ) consists of two nearly parallel fracture transform faults that intersect the Mid-Atlantic Ridge (MAR) axis. This area has high primary productivity and biomass levels due to the topography and water. A predominant hydrographic feature of the MAR is the Sub-Polar Front (SPF) which runs along the southern edge of the CGFZ and is known as a biogeographical boundary for multiple species. As part of The Census of Marine Life project Patterns and Processes of the Ecosystem of the northern Mid-Atlantic (MAR-ECO), the abundance and distribution patterns of the CGFZ crustacean community (primarily Decapoda) surveyed during the 2009 H B. Bigelow voyage were analyzed. Specimens were collected from five discrete depths, ranging between 0 and 3500 m deep, using a Norwegian microzooplankton trawl equipped with a multi-sampler. Analyses indicate that geographic location relative to the CGFZ is correlated to pelagic crustacean distribution, but the surrounding water masses are likely the primary drivers of abundance and diversity variations. The abundance of pelagic crustaceans was higher in the cold waters to the northwest of the CGFZ. A higher diversity was found in the warmer southeastern waters presumably due to stable influx of nutrients and food supply, and dominating mesoscale eddies located in the southeast of the study area. Benthic crustaceans in the northwest had an increased abundance and diversity compared the southeast region. This suggests that at depth, the MAR may act as a biogeographic barrier separating the two geographic regions and reducing connectivity.