Distribution, abundance, and diversity of euphausiids and their relationships with hydrodynamic processes in Campeche Canyon, Gulf of Mexico

Abstract

We analyzed the abundance, diversity, and distribution of euphausiids and their relationship with hydrodynamic processes from February 2011 to October 2012 in the Campeche Canyon in the southern Gulf of Mexico. Sampling was conducted at 55 oceanographic stations and zooplankton were captured using horizontal trawls. Environmentalvariables (temperature, salinity, and oxygen) and phytoplankton fluorescence were recorded at different depths. Twenty-four species of euphausiids representing the genera Euphausia, Nematobrachion, Nematoscelis, Stylocheiron, and Thysanopoda were identified. Stylocheiron carinatum was abundant in February and October, with the furcilia stage always the dominant one. Differences were observed among the 4 zones identified based on the bathymetric criteria; zone III (axis and head of the canyon) presented the highest diversity of euphausiids between 100 and 200 mwith 2.14 bits Ind-1 in February and 1.99 bits Ind-1 in October. The spatial-temporal distribution of euphausiids was heterogeneous in water bodies with temperatures between 15 and 22 °C and low dissolved oxygen concentrations, which were distributed outside the maximum concentrations of chlorophyll-a (2,127 mg m-3) and had an affinity for the frontal regions between cyclonic and anticyclonic eddies.