Short-term variability in the assemblage of medusae and ctenophores following upwelling events in the southern Benguela ecosystem

Abstract

Changes in the composition of the assemblage of medusae and ctenophores were examined daily over a period of 28 d, encompassing 3 upwelling events in a non-advective environment within the southern Benguela ecosystem. The relationships between assemblage composition and the environment were analysed using canonical correspondence analyses. Although distinct assemblages were associated with upwelling itself, as well as with the periods of water column stabilisation and stratification, indicator species for the assemblages could not be identified. This reflected the near ubiquitous nature of most assemblage members, and their probable response to historical (unmeasured) environmental variables. That notwithstanding, it is clear that short-term changes in characteristics of the surface and deeper water environment are reflected by short-term changes in the composition of the gelatinous zooplankton assemblage. This is more reminiscent of phytoplankton than holozooplankton and probably reflects the meroplanktic nature of most assemblage members.