Análisis de las condiciones oceanográficas y biológicas del afloramiento costero frente a Callao en períodos contrastantes durante el 2018

Graco M, Anculle T, Aramayo V, Bernales A, Carhuapoma W, Correa D, Fernandez J, Garcia W, LedesmaJ, Marquina R, Quipuzcoa L, Romero D, Sarmiento M, Solis J. 2019. Analysis of the oceanographic and biologicalconditions of the coastal upwelling off Callao in contrasting periods during 2018. Bol. Inst Mar Peru. 34(2): 519-543.-The coastal upwelling ecosystem off Peru is characterized by intense oceanographic variability that impactsthe Oxygen Minimum Zone (OMZ), on nutrient availability and the plantonic and benthic ecology. This workpresents the results of two Intensive Oceanographic Cruises (CRIO in Spanish) associated with one of the mostimportant upwelling areas of Peru, Callao (12°S), carried out in autumn (April) under higher productivity and inwinter (August) when the physical upwelling process predominated. In April and August 2018, the conditions canbe defined in two contrasting periods under the influence of different intensities of the upwelling events with theassociated chemical and biological responses. Both periods were characterized by an intense and shallow OMZ. Inthe autumn, higher productivity and deficit of nitrates were observed, while in winter silicates and nitrates wereavailable throughout the study area. The phytoplankton community reflected the different conditions. Diatomswere dominant in April and on the coast, while winter and the ocean side were dominated by the nanoplankton.Changes in water masses gave the possibility of approaching ocean waters in winter increasing pH favorable forcoccolithophorid calcifying organisms. These organisms have been identified during El Nino Costero 2017. At thebenthos, the response indicates conditions that would still reflect aspects associated with El Nino and its impacton oxygenation and organic matter. The predominance of polychaetes such as Mageloma phyllisae and the decreaseof microbial mats (Candidatus Marithioploca) was detected. Less reduced sediment with relatively low H2S valueswas present. For the foraminifer assemblage, a mixture of species was observed, some that appeared since El Ninoand others that reflect some normalization towards oxygen deficiency and the availability of organic matter.