Metazoan meiofauna within the oxygen-minimum zone off Chile: Results of the 2001-PUCK expedition.

A quantitative study of metazoan meiofauna was carried out at continental shelf and slope stations affected by the oxygen-minimum zone in the eastern South Pacific off Chile. Densities of meiobenthos at the investigated stations off Antofagasta (22°S), Concepción (36°S), and Chiloé (42°S) ranged from 1282.1 to 8847.8 ind 10 cm⁻². Oxygen deficiency led only to average abundances, despite higher food availability and freshness at the corresponding sites. Sediment organic carbon, chlorophyll-a, and phaeopigment contents were used as measures of the input from water-column primary production, which accumulated at the oxygen-minimum zone stations. The highest abundances were found at a station with an oxygen content of 0.79 mL L⁻¹, which was slightly elevated from what is defined as oxygen minimum (0.5 mL L⁻¹). The most oxygenated site yielded the lowest densities. Meiofauna assemblages became more diverse with increasing bottom-water oxygenation, whereas nematodes were the most abundant taxon at every station, followed by annelids, copepods, and nauplii.