Document of bibliographic reference 405173

BibliographicReference record

Type

Bibliographic resource

Type of document

Book/Monograph

Type of document

Dissertation

BibLvlCode

M

Title

Biogeographic and diversity patterns of pelagic copepods in the South Pacific Ocean

Abstract

Zooplankton are a key component of the marine ecosystem, mainly due to their role as part of the foundation of life in the ocean acting as the trophic link between primary producers and the other upper-trophic levels, as well as a component of the microbial loop and their function in biogeochemical cycles. Moreover, due to their relatively short life cycles, they are known to rapidly respond to oceanographic and environmental variations associated with climate-oceanographic change. Zooplankton representatives have been widely studied, especially copepods, which exhibit a strong dependence of their vital rates with temperature and other climate-related environmental factors. Regarding environmental impact on zooplankton, in the South Pacific Ocean there is a broad range of surface-ocean productivity and physical-oceanographic regimes that shape different environments and trophic conditions within the coastal and open ocean; therefore, to study the drivers of their species diversity in these areas would be useful to elucidate how zooplankton may respond to a changing ocean. The present thesis work focused on zooplankton diversity in relation to large-scale oceanographic variation in the South Pacific while considering the vertical axis as well. In the first chapter, a 27-years (1993–2019) database on species occurrence of planktonic copepods of the South Pacific Ocean was used, along with associated oceanographic variables, to examine their spatial patterns of biodiversity in the upper 200 m of the ocean. The aim of this study was to identify ecological regions and the environmental predictors explaining such patterns. It was found that hot and cold spots of diversity, and distinctive species assemblages were linked to major ocean currents and large regions over the basin, with increasing species richness over the subtropical areas on the East and West sides of the South Pacific. While applying the spatial models, it was shown that the best environmental predictors for diversity and species composition were temperature, salinity, chlorophyll-a concentration, oxygen concentration, and the residual autocorrelation. Nonetheless, the observed spatial patterns and derived environmental effects were found to be strongly influenced by sampling coverage over space and time, revealing a highly under-sampled basin. In the second chapter, we tested the hypothesis that environmental stability is the key modulating mechanism of copepod diversity patterns in the Humboldt Current System (HCS), by using a 17-years (1995-2011) database on species occurrence of copepods along with environmental data for the upper 500 m of the ocean (divided into five vertical strata) for the upwelling zone off Chile, distinguishing two regions (northern and southern) having different seasonal regimes of wind-driven upwelling. We estimated indices for copepod diversity and their distribution, segregated by regions and depth strata. The indices were then associated with oceanographic variables forced by upwelling intensity, along with an estimate of eddy kinetic energy (EKE), as a proxy of environmental stability. From the entire community, we found 18 dominant species widely distributed in the study area. Some were exclusive species for the upper depth stratum with differences in the number of exclusive species per region and depth. From Linear Mixed Models we found that the diversity indices significantly differed between regions and strata, and their variance was mainly explained by temperature, salinity, oxygen concentration, temperature stability, and eddy kinetic energy (EKE). Both temperature stability and EKE were the best predictors of copepods diversity, suggesting that climate-oceanographic stability, forced by upwelling intensity, is the key driver for promoting and maintaining copepod diversity in the HCS. The thesis provides findings that support the main hypothesis, concluding that the structuring of copepod communities on a large spatial scale in the South Pacific is strongly associated with a significant zonation on the horizontal and vertical axes in which the stability (variance) of environmental parameters, such as temperature and kinetic energy appear as key factors in the modulation of these biogeographic and diversity patterns.

Bibliographic citation

Pérez Aragón, M.I. (2024). Biogeographic and diversity patterns of pelagic copepods in the South Pacific Ocean. PhD Thesis. Universidad de Concepción: Concepción. 164 pp.

Topic

Marine

Access rights

open access

Is accessible for free

true