Kreiner, A.

Verheye, H.

Open Marine Archive

BENEFIT Research Projects
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Retrospective analysis of zooplankton community structure  
in the Benguela current large marine ecosystem
Hans Verheye1 and  Anja Kreiner2 
1Marine and Coastal Management, Cape Town, South Africa
2National Marine Information and Research Centre, Swakopmund, Namibia
Project description
The overall objective of the project was to quantify changes in zooplankton abundance and 
community structure in the northern Benguela over the past 50 years, for comparison and integration 
with information on long-term changes in zooplankton abundance and community structure in the 
southern Benguela.  The project was motivated by the need for baseline information on natural and 
anthropogenically forced changes in the Benguela ecosystem as a whole, which is a pre-requisite 
for ecosystem management.  
The project started as a BENEFIT project, with a retrospective analysis of a small subset of the 
SWAPELS (South West Africa Pelagic Egg and Larvae Survey) zooplankton sample archive from 
the 1970s and 1980s by two post-graduate students (T. Mainoane and S. Tsotsobe).  In 2004 the 
project was taken over by the BCLME Programme and expanded to include the full SWAPELS 
collection and more recent data collected on the NatMIRC monitoring line off Walvis Bay.  BENEFIT 
continued to support the project, specifically through partial funding of a regional training workshop 
on zooplankton taxonomy and identification, and of a PhD student involved in the study. 
The bulk of the work comprised the curation and cataloguing of some 15000 zooplankton samples 
from the SWAPELS surveys, and the retrospective analysis of a representative subset of about 800 
samples from this collection to quantify the abundance and describe the community structure of 
zooplankton in the northern Benguela during this period.  Zooplankton samples routinely collected on 
the NatMIRC monitoring line since 2000 were analysed in the same way to provide an inter-decadal 
comparison for the Walvis Bay region, on which the SWAPELS analysis was initially focused.  
A full-time sample curator and part-time sample analyst were engaged through the project, with 
initial financial assistance from the ENVIFISH and VIBES/IDYLE Programmes, in recognition of 
the collection’s scientific value.  The data management was contracted to the International Ocean 
Institute, University of the Western Cape, who were responsible for constructing a Benguela Plankton 
Portal to meet the BCLME’s requirements for a comprehensive inventory of plankton metadata in 
the ecosystem.  In addition, studentships were awarded to a PhD student (Fabienne Cazassus), and 
to a BSc Hons/ MSc student (Ignatius Kauvee) to work within the project.  The training workshop 
was co-funded by BENEFIT and the Alfred P. Sloan Foundation through the Census of Marine Life 
(Zooplankton) Programme. 
Achievements 
The achievements of the project have been reported in detail to the BCLME in the final report of 
BCLME Project EV/PROVARE/02/05, prepared by Hans Verheye and submitted in June 2007, from 
which the summary below has been compiled.  
A major achievement has been the capture of zooplankton data from the enormous number 
(approximately 20000) of samples collected during the SWAPELS surveys, from which hitherto only 
the ichthyoplankton had been extracted and analysed.  This has allowed inter-decadal changes in 
zooplankton abundance, distribution and community structure in the northern Benguela to be described 
for the first time, and to be compared with corresponding long-term changes in the zooplankton of 
the southern Benguela, thus providing an integrated overview of changes in zooplankton in the entire 
Benguela ecosystem over half a century.  Some of the major features are summarised below.  
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During the SWAPELS period copepod abundance was consistently higher during the upwelling 
(August-October) and intermediate (November-January) seasons than during the quiescent 
(February-April) season, with maxima and minima in 1983/84 and 1984/1985 respectively (Fig. 1). 
This signal was so strong that it often masked inter-annual patterns.  During the Benguela Niño in 
1984, copepod abundance during the upwelling and intermediate seasons dropped dramatically, and 
only recovered slowly, with a much reduced seasonality in subsequent years.  In contrast, copepod 
abundance was fairly consistent during the quiescent season over the entire time period.  There 
were considerable inter-seasonal and inter-annual changes in the copepod communities during 
the SWAPELS period, with distinctly different community structures before, during, and after the 
Benguela Niño in 1984 (Fig. 3). 
Copepod abundance was highly variable in the NatMIRC samples, again with clear seasonal cycles 
(Fig. 2), but changes in the community structure during the sampling period (2000-2006) were not 
significant.  It was found that a reduction in primary productivity in the summer of 2005/2006 due to 
reduced upwelling was reflected in a significant reduction in copepod abundance off Walvis Bay, and that 
the copepod species composition in this period was significantly different to that in all other years. 
1978/79
1979/80
1981/82
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1983/84
1984/85
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1988/89
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 m
-2  +
 1
)
 Upwelling
 Intermediate
 Quiescent
Current effect: F(9, 236)=2.3126, p<0.05
Vertical bars denote 0.95 confidence intervals
Figure 1. Year and season effect on copepod abundance during the SWAPELS period from a GLM. 
The year runs from 1 July of one year to 30 June the next.
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Figure 2. Copepod abundance (no m-2) between February 2000 and February 2007 along the Walvis 
Bay transect. The dots represent the station positions. 
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Overall, despite some gaps in the data set, it has been concluded that mesozooplankton biomass 
and total copepod abundance in the northern Benguela has been increasing over the past five 
decades.  In addition, there is evidence to suggest considerable inter-decadal variability associated 
with large-scale changes in coastal upwelling.  The “turning point” in upwelling and zooplankton 
appears to coincide with the Benguela Niño in 1984.  There is evidence to suggest than another 
reversal occurred in the early 2000s. 
Comparison with the southern Benguela (Fig. 4) shows that although there have been marked long-
term changes in the abundance, distribution and structure of the copepod community there as well, 
the changes in the two sub-systems do not seem to have been in synchrony.  
Another achievement of the project has been the construction of the plankton database, which 
currently contains 91964 records from 4465 samples at 648 stations, spanning the wider Benguela 
from its northern boundary to Durban in the Indian Ocean.  Data are held from 1958 to 2001, with 
greater emphasis on the older data.  The Benguela Plankton Portal, which consists of the metadata 
and metadata directory, the database itself and a comprehensive bibliography containing 233 
publications at present, will continue to be an invaluable tool for further retrospective analysis of 
plankton data in support of research and management in the Benguela region, if properly maintained 
and supported by users. 
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Oithona spp.
C. brachiatus
M. lucens
C. carinatus
Calanus spp.
R. nastus
Figure 3. Long-term, 
decade-scale changes 
in copepod community 
structure (expressed 
a s  p e r c e n t a g e 
composition of the 
six most dominant 
spec ies  –  adu l ts 
and copepodites C5 
combined,  shown 
on the right) on the 
Walvis Bay transect 
since the 1970s.
6
5
4
3
1950 1960 1970 1980 1990 2000 2010
Total copepods: northern Benguela
6
5
4
3
1950 1960 1970 1980 1990 2000 2010
Total copepods: southern Benguela
Northern - southern Benguela comparison:
total copepod abundance {Log10[(No.m-2)+1]}
Figure 4. Comparison of time-series 
of total copepod abundance in the 
northern and southern Benguela 
since the 1950s. Data points are 
annual mean abundances. 
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Outputs
Data
A major output of the project is the Plankton Database and Benguela (Zoo)plankton Portal described 
above.
Publications 
Hansen F.C., R.R. Cloete and H.M. Verheye. 2005. Seasonal and spatial variability of dominant copepods 
along a transect off Walvis Bay (23˚S), Namibia. African Journal of Marine Science 27(1): 55-63.
Hutchings L., H.M. Verheye, J.A. Huggett, H. Demarcq, R. Cloete, R.G. Barlow, D. Louw and A. da Silva. 
2006. Variability of plankton with reference to fish variability in the Benguela Current Large Marine 
Ecosystem - an overview. In: L.V. Shannon, G. Hempel, P. Malanotte-Rizzoli, C.L. Moloney and J.D. 
Woods (Eds.). Benguela: Predicting a large marine ecosystem. Elsevier Large Marine Ecosystems 
14: 91-124.
Verheye H.M. 2000.  Decadal-scale trends across several marine trophic levels in the southern Benguela 
upwelling system off South Africa. Ambio 29(1): 30-34.
Theses
Kauvee I.K.V. assisted by M.J. Gibbons and H.M. Verheye. 2005. Observations on the composition of 
the copepod community either side of the Lüderitz upwelling cell. I.K.V. Kauvee BSc Hons thesis, 
University of the Western Cape, South Africa. 41pp.
Tsotsobe S.V. 2005. Temporal and spatial variability in copepod abundance, distribution and community 
structure off Walvis Bay in the northern Benguela current, 1979-1981. MSc thesis, University of the 
Western Cape, South Africa. 111pp.


Retrospective analysis of zooplankton community structure in the Benguela current large marine ecosystem

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