Potentially harmful phytoplankton in the natural bank of Peruvian scallop in Lobos de Tierra Island and the Lagunas-Chérrepe concession area (April, September 2017)

Abstract

We describe the phytoplankton communities on the natural bank of Peruvian scallop in Lobos de Tierra Island (April) and off Lagunas-Chérrepe (September) in 2017. The study was based on potentially toxic and/or harmful species and their relationship with environmental parameters. In both locations, the oceanographic conditions were variable due to the El Niño Costero in the first semester and to the cooling caused by the arrival of cold Kelvin waves in September. In April, in the sampling stations of Lobos de Tierra Island, phytoplankton predominated, characterized by an abundance of diatoms typical of coastal upwelling: Chaetoceros curvisetus, C. compressus, Thalassiosira subtilis, and T. angulata, which indicated a strong coastal upwelling. We recorded 41 diatoms, 19 dinoflagellates, and 2 silicoflagellates. The densities of the dinoflagellate Dinophysis acuminata ranged from 0 to 160 cel.L-1, which did not exceed the allowable limits of Sanitary Control for Mexico (> 200 cel.L-1) and Uruguay (> 500 cel.L-1). We also recorded Pseudo-nitzschia seriata and P. delicatissima, whose densities ranged from 0 to 320 cel.L-1, which did not exceed the allowable limits of those countries. The highest concentrations of D. acuminata and P. seriata were located in the euphotic zone (0 - 5 m depth), while P. delicatissima was found between 10 and 15 m depth related to silicate and nitrate levels. In September, phytoplankton in Lagunas-Chérrepe predominated in all stations, characterized by neritic diatoms: Coscinodiscus perforatus, Lithodesmium undulatum, Chaetoceros lorenzianus, Thalassiosira rotula, T. angulata, Stephanopyxis turris, and Thalassionema nitzschioides, the latter was abundant in most stations. We recorded 29 diatoms, 8 dinoflagellates, and 2 silicoflagellates. In some sampling stations, the P. delicatissima and P. seriata groups were recorded.