Hanselmann, K.

Mohammed, S.

Muthumbi, A.W.

Waweru, B.W.

Open Marine Archive

-  99  -  
Oral presentation Science in a modern era 
Composition of macro-infauna and their distribution across Northern 
Benguela upwelling system - Namibia 
Waweru Beth Wangui
1,2
, Mohammed Said
3
, Hanselmann Kurt
4
 and Mathumbi Agnes Wangui
3
 
1 
Department of Biology, Campus Ledeganck, Ghent University, Ledeganckstraat 35, 9000 
Ghent, Belgium 
  E-mail: bethwwr54@gmail.com  
2 
Kenya Marine and Fishers Research Insitute, P.O. Box 81651-80100, Mombasa, Kenya  
3 
University of Nairobi, P.O. Box 30197, GPO, Nairobi, Kenya  
4 
Department of Earth Sciences, Swiss Federal Institute of Technology (ETH) Zurich, P.O. Box 71 
Rämistrasse, 8006 Zurich, Switzerland 
 
Macro-infauna are among the most abundant organisms in marine ecosystems where they play a critical 
role in nutrient cycling, organic matter turnover, provision of nourishment to the higher organisms in 
the food web and maintenance of soil physical and biogeochemical structure through bioturbation. 
Despite their significance in marine reamls, there is inadequate scientific understanding of macro-infauna 
diversity in Benguela Upwelling Systems (BUS) specifically across Oxygen Minimum Zones (OMZ). Three 
transects were chosen; Cape Frio (20⁰S), Walvis Bay (23⁰S) and Luderitz (26⁰S) for sampling. Sediments 
were systematically collected at 20⁰S (2nm, 20nm, 40nm), 23⁰S (2nm, 20nm, 70nm) and 26⁰S (90nm) 
using multi-corer where macrofauna were sub sampled using plastic corers (diameter=3.5cm; length= 
10cm). The samples were preserved using 5% buffered formaldehyde solution, stained with Rose Bengal 
(to aid in sorting) and observed under a dissecting microscope. Nematodes were the dominated 
organisms in macrofauna samples whose percentage ranged from 21-84.5% in all sampling stations. 20⁰S 
40nm had the highest taxa of nematodes (7510000ind-m2) an indicator of their ability to survive in 
hypoxic environments (0.41ml-l). 23⁰S 40nm sampling site was anoxic (0.148ml-l) with no recorded 
nematodes and annelids indicating failure of macrofauna to adapt in extremely low oxygen. Annelids 
(polychaetas and oligochaetas) had lower percentage than nematodes in all sampling sites showing 
limited ability to adapt in extreme environments. The results highlightened the adaptability of nematodes 
in hypoxic conditions which could have been enhanced by symbiotic relationship with sulphur reducing 
bacteria, Theomargarita. Further analysis is underway to identify nematodes to genus level (macrofauna 
and meiofauna samples) hence providing baseline data and adaptive mechanisms of nematodes in OMZ. 
 
Keywords: oxygen minimum zones; macrofauna; Benguela upwelling system; nematodes  
  


Composition of macro-infauna and their distribution across Northern Benguela upwelling system - Namibia

http://www.vliz.be/imisdocs/publications/318418.pdf

Composition of macro-infauna and their distribution across Northern Benguela upwelling system - Namibia

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