Zooplankton associated with the oxygen minimum zone system in the northern upwelling region of Chile during March 2000 |
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| Institution: | 1. Centro de Investigación Oceanográfica en el Pacífico Sur-Oriental (FONDAP-COPAS), Estación de Biología Marina, Departamento de Oceanografía, Universidad de Concepción, Casilla 44, Dichato, VIII Region, Chile;2. Programa de Postgrado en Oceanografía, Departamento de Oceanografía, Universidad de Concepción, Casilla 160-C, Concepción, Chile;1. Department of Oceanography & Center for Oceanographic Research in the eastern South Pacific University of Concepcion PO Box 160-C, Concepcion, Chile;2. Department of Oceanography & Center for Oceanographic Research in the eastern South Pacific University of Concepcion PO Box 160-C, Concepcion, Chile;1. Instituto de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain;2. Instituto Milenio de Oceanografía (IMO-Chile), Universidad de Concepción, Casilla 160-C, Concepción, Chile;3. Depto. de Oceanografía, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile;4. Instituto de Ciencias Marinas y Limnológicas, y Centro FONDAP de Investigación de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Valdivia, Chile;5. Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile;1. Louisiana Universities Marine Consortium, 8124 Highway 56, Chauvin, LA 70344, USA;2. Texas A&M University, College Station, TX 77843, USA;3. Scripps Institution of Oceanography, University of California, La Jolla, San Diego, CA 92093, USA;1. Florida International University, Department of Biological Sciences, Marine Science Program, North Miami, FL, 33181, USA;2. NORCE Norwegian Research Centre AS, Fantoftvegen 38, 5072, Bergen, Norway;3. Institute of Marine Research, P.O Box 1870, Nordnes, Bergen, Norway;4. National Centers for Coastal Ocean Science, NOAA Beaufort Laboratory, 101 Pivers Island Rd., Beaufort, NC, 21516, USA;5. Fisheries and Aquatic Sciences, University of Florida, 7922 NW 71st Street, Gainesville, FL, 32608, USA |
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| Abstract: | Zooplankton in the coastal upwelling region off northern Chile may play a significant biogeochemical role by promoting carbon flux into the subsurface OMZ (oxygen minimum zone). This work identifies the dominant zooplankton species inhabiting the area influenced by the OMZ in March 2000 off Iquique (20°S, northern Chile). Abundance and vertical distribution studies revealed 17 copepod and 9 euphausiid species distributed between the surface and 600 m at four stations sampled both by day and by night. Some abundant species remained in the well-oxygenated upper layer (30 m), with no evidence of diel vertical migration, apparently restricted by a shallow (40–60 m) oxycline. Other species, however, were found closely associated with the OMZ. The large-sized copepod Eucalanus inermis was found below the oxycline and performed diel vertical migrations into the OMZ, whereas the very abundant Euphausia mucronata performed extensive diel vertical migrations between the surface waters and the core of the OMZ (200 m), even crossing it. A complete assessment of copepods and euphausiids revealed that the whole sampled water column (0–600 m) is occupied by distinct species having well-defined habitats, some of them within the OMZ. Ontogenetic migrations were evident in Eucalanidae and E. mucronata. Estimates of species biomass showed a substantial (>75% of total zooplankton biomass) daily exchange of C between the photic layer and the OMZ. Both E. inermis and E. mucronata can actively exchange about 37.8 g C m−2 d−1 between the upper well-oxygenated (0–60 m) layer and the deeper (60–600 m) OMZ layer. This migrant biomass may contribute about 7.2 g C m−2 d−1 to the OMZ system through respiration, mortality, and production of fecal pellets within the OMZ. This movement of zooplankton in and out of the OMZ, mainly as a result of the migratory behavior of E. mucronata, suggests a very efficient mechanism for introducing large amounts of freshly produced carbon into the OMZ system and should, therefore, be considered when establishing C budgets for coastal upwelling systems. |
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