Potential effects of shoaling of oxygen minimum zone on the population of Acartia (Acanthacartia) tonsa in the Humboldt Current Upwelling System (23°S)

Diel vertical migration of Nannocalanus minor and Eucalanus inermis (Copepoda: Calanoidea) associated with the oxygen minimum zone in northern Chile

“…Their higher diversity and abundance substantiate this behavior (Escribano et al 2009, Paulmier & Ruiz-Pino 2009, Wishner et al 2013. Zooplankton abundance decreases significantly at depths with less than 44.6 µM O2, where the OMZ is located (Ruz-Moreno et al 2023). A succession of taxa adapted to hypoxic conditions can be found within this environment, resulting in lower species richness, abundance of zooplankton, and higher trophic levels (Wishner et al 2013, Donoso & Escribano 2014.…”

“…It has been shown that zooplankton communities respond to changes in temperature, seasonal upwelling intensity, and interannual fluctuations by shifting dominance, abundance, diversity, and species richness , Escribano et al 2009, Hugget et al 2009. Additionally, some studies have shown that environmental features directly affect the ontogeny development of certain calanoid species such as E. inermis (Hidalgo et al 2005a,b, Criales-Hernández et al 2007, Wishner et al 2020, C. chilensis, and A. tonsa and their growth rates (Torres & Escribano 2003, Ruz et al 2015, 2017, Ruz-Moreno et al 2023. The vertical zonation of zooplankton has allowed for the description and understanding of the response of the copepod community off the coastal zone of Chile.…”

Molecular evidence for a new endemic species of Acartia (Copepoda, Calanoida) from the Southeast Pacific coast

“…These traits include a broad tolerance to environmental fluctuations and the production of large cohorts 27,77,78 . Ecology and physiology studies have shown that populations previously identified as A. tonsa off the coast of Chile, including populations studied here, used mechanisms of tolerance and plasticity to face extreme environmental conditions 34,49 , and populations of different biogeographical areas showed signs of adaptation to local conditions of their habitat 34 . When we analyzed the genetic variation of both mitochondrial and nuclear markers between populations and biogeographic areas, we observed high genetic variability within populations, which was consistent with the levels of genetic diversity (Table 1).…”

“…Significant values are in bold. www.nature.com/scientificreports/ For decades, the presence of A. tonsa has been documented along the coast of Chile, with numerous ecological studies conducted on these populations 34,[46][47][48][49]76 . In these studies, it was expected that A. tonsa populations from the Chilean coast would exhibit a range of physiological and life history traits characteristic of cosmopolitan species, such as A. tonsa found in other oceans and seas worldwide.…”

“…To date, the presence of A. tonsa in SEPO coastal systems has been identified solely based on morphological characteristics, without molecular confirmation. In this context, it is crucial to emphasize that despite multiple studies on the distribution, physiology, and life history of populations along the coasts of Chile, there are no molecular sequences of A. tonsa available for the SEPO 34,[46][47][48][49] . The SEPO, specifically the coastal domain along the Chilean coast (18-56° S), provides a unique natural setting for studying the population dynamics of planktonic coastal species.…”