Hidalgo Díaz, P. (2005). Ciclos de vida y mecanismos de adaptación de copépodos pelágicos a la variabilidad oceanográfica en zonas de afloramiento del ecosistema de corrientes Humboldt. [Life cycles and adaptive mechanisms of pelagic copepods to the oceanographic variability in upwelling zones of the Humboldt Current ecosystem.]. Ph.D. Thesis, Universidad de Concepción, Concepción, Chile. 160 pp. [In Spanish.].

148497

Hidalgo Díaz, P.

2005

160 pp. [In Spanish.]

Publication

http://repositorio.udec.cl/jspui/handle/11594/4319

Available for editors   [request]

Copepods are key components of the zooplancton in the Humboldt Current System (HCS). However, the adaptation mechanisms that determine their success and high abundance in the coastal zone of the HCS are unkown. This zone exhibits a large environmental heterogeneity driven by coastal upwelling, a process that may occur throughout the year or seasonaily, depending on latitude along the HCS. In this environment, copepods must cope with distinct environmental regimes over a variety of spatial and temporal scales. Within this framework, the present thesis postulates that dominant copepods in the HCS have become adapted to oceanographic variability by adjusting their developmental rates, in according to the predominant thermic environment. This hypothesis was assessed by studying species responses to temperature under laboratory conditions andlor by means of fleid studies of their annual life cycles upon different thermic regimes. The studies were carried out in the upwelling zones off Iquique (21°S), Mejillones (23° S), and Concepción (36° S). Embryonic developmental rates were experimentally estimated for Calanus chilensis, Centropages brachiatus and Paracalanus parvus and adaptation to temperature was examined through the parameter a of Bélehrádek equation: D = a (T + a)b, where D = development time (d), T = temperature (°C), and a, b and a their parameters. Based on time series sampling (Mejillones and Concepción) and a cruise (Iquique), oceanographic information was obtained along with zooplancton samples for analysis of stages abundance of the species C. chilensis, C. brachiatus and Eucalanus inermis. Additionally, vertical distribution in relation to the oxygen minimum zone (OMZ) was studied for E. inermis off Iquique, as well as the role of its population in the active transport of carbon (C) into the OMZ Experimental results showed that the parameter a was significantly different among species, being io oc, 5.6 °c and -4.5 °C for C. chilensis, C. brachiatus and Paraclanus parvus, respectively, in absence of regional or seasonal effects. C chilensis developed faster (-.10%) than C. brachiatus, whereas P. parvus responded more rapidly to changes in temperature. Development rates (DR) were similar among species at temperatures between 10 to 12 T. P. parvus notably reduced its DR at low temperature (<10 °C) whereas DR became abruptly accelerated at temperatures >12 T. At warm temperatures (>15 oc) this species reduced its generation time (GT), incrementing the number of generations (>20) per year. The time series revealed a strong influence of local upwelling regimes on the annual life cycles of 3 species. In the northern zone, E. inermis had 3 annual cohorts, with GT >30 days, and its abundance positively associated with temperature (r2 = 0.6, P <0.05). The distribution of this species was also associated with the OMZ; through its vertical migration contributes to C fluxes into the OMZ, with about 3-14 mg C m 2 d'. In the same zone, C. chilensis and C. brachiatus reproduced continuously throughout the year, having at least 15 cohorts and GT of 19-20 days. In the southern zone, C. chilensis and C. brachiatus reproduced only at certain periods of the year, involving 4 cohorts per year and GT between 30 and 140 days. It was concluded that regional thermic regimes, as a product of upwefling variability, affect life cycles of copepods in the HES, in absence of local or seasonal adaptations. Temperature affects DR, GT, and the number of cohorts per year. Upwelling also exerts an additional effect that modifies food resources locally and seasonally, as well as vertical distribution of the OMZ. The strong coupling between upwelling variability and life cycles of the targeted species might substantially impact secondary production of zooplankton in the HCS.

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