Assessment of an environmental barrier to transport of ichthyoplankton from the southern to the northern Benguela ecosystems
Authored by Christophe Lett, Jennifer Veitch, der Lingen Carl D van, Larry Hutchings
Date Published: 2007
DOI: 10.3354/meps06982
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Abstract
The Luderitz upwelling cell and Orange River cone (LUCORC) area, a
transboundary region between South Africa and Namibia, is considered to
be an environmental barrier to transport of ichthyoplankton from the
southern to the northern Benguela upwelling ecosystems. We use
environmental data and modelling to assess the potential mechanisms
responsible for this barrier: environmental data were extracted from the
1 x 1 degrees World Ocean Atlas 2001 database and used to build maps of
annual mean salinity, temperature, chlorophyll, dissolved oxygen and
nutrient concentrations; outputs of a regional circulation model were
used in an individual-based model to assess the transport of passive
particles from the southern to the northern Benguela. The data show no
clear environmental barrier at sea surface, but the model results
suggest that particles released there would be largely transported
offshore. The model also shows that particles released below the surface
could be transported alongshore from the southern to the northern
Benguela, but low subsurface temperatures would increase ichthyoplankton
mortality and hence be a strong limiting factor to northward transport.
We conclude that the combination of a surface hydrodynamic and a
subsurface thermal barrier could limit the possibility for
ichthyoplankton of epipelagic species to be transported from the
southern to the northern Benguela, but that ichthyoplankton of
mesopelagic species, having a wider tolerance to low temperatures, would
be less affected.
Tags
Model
System
Variability
Larvae
Nursery areas
Upwelling ecosystem
Retention
Anchovy engraulis-capensis
Surface
Boundary