06 Oct 2023
 | 06 Oct 2023
Status: this preprint is currently under review for the journal BG.

Influence of Oxygen Minimum Zone on Macrobenthic Community Structure in the Northern Benguela Upwelling System: A Macro-Nematode Perspective

Hashim Said Mohamed, Beth Wangui Waweru, and Agnes Muthumbi

Abstract. Macrobenthic samples were collected offshore Namibia on board R/V Mirabilis during the 3rd RGNO training and the National Marine Information and Research Centre's (NatMIRC's) plankton survey from 13th May to 17th May 2016. Two transects, Cape Frio (20º S) and Walvis Bay (23º S), hosted three stations each, while the third transect, Luderitz (26º S), hosted only one station. From the results, three oxygen zones were identified, namely Microxic (< 0.1 ml l−1), Dysoxic (0.1–1.0 ml l−1), and Oxic (> 1.0 ml l−1). A total of 20 Macrobenthic taxa were identified; Nematoda, Polychaeta, Cumacea, and Oligochaeta were the most dominant taxa and recorded abundances in all oxygen zones. Eighteen genera of macro-Nematoda were identified; Desmolaimus and Paracomesoma dominated in all oxygen zones, Metoncholaimus recorded higher abundance in the Dysoxic stations, and no abundance in the Oxic stations, and the opposite was observed for Halanonchus and Dorylaimopsis. H′ Diversity values for both the general Macrofauna and Macro-Nematoda were higher in the Oxic stations and lower in both the Dysoxic and Microxic stations, while an opposite trend was observed for Dominance values. Density values were lower in Microxic stations and higher in Dysoxic stations, while at the Oxic stations, the density values fell in between the two hypoxic zones.

Hashim Said Mohamed, Beth Wangui Waweru, and Agnes Muthumbi

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on bg-2023-151', Leonardo Tamborrino, 11 Oct 2023
    • CC2: 'Reply on CC1', Said Hashim, 26 Oct 2023
  • RC1: 'Comment on bg-2023-151', Simon Forster, 15 Nov 2023
    • AC1: 'Reply on RC1', Said Hashim, 17 Nov 2023
    • AC2: 'Reply on RC1', Said Hashim, 21 Dec 2023
  • RC2: 'Comment on bg-2023-151', Anonymous Referee #2, 30 Nov 2023
    • AC3: 'Reply on RC2', Said Hashim, 21 Dec 2023
Hashim Said Mohamed, Beth Wangui Waweru, and Agnes Muthumbi
Hashim Said Mohamed, Beth Wangui Waweru, and Agnes Muthumbi


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Short summary
This study looked at the Benguela Upwelling System and its influence on organisms living in the sea bed. Our research found that low dissolved oxygen resulted in reduced species richness and diversity. The density of these organisms peaked at the edge of these hypoxic areas. Hypoxic areas had low diversity, low evenness, and high dominance. Due to this observation, the authors believe that increasing hypoxic areas in the ocean will have a similar influence on organisms as observed in this study.