Human impact on the biodiversity of macroinvertebrates in intertidal rocky shores along the Namibian coast
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Date
2023
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Publisher
University of Namibia
Abstract
The intertidal rocky shores along the central coast of Namibia provide multiple microhabitats supporting a high species biodiversity and a unique heterogeneous environment. Extreme anthropogenic disturbance such as harvesting and trampling due to human visitors may reduce biodiversity, modifying species genetic variability and overall ecosystem functioning. This research compares macroinvertebrate assemblage structures, size and diversity between disturbed and less disturbed sites. The study was conducted in March and June 2022 at six different sites along the coast – four disturbed sites and 2 control (less disturbed) sites. At each site, three line transects were used with a 0.5m x 0.5m quadrat placed at 5m intervals for 50m. In each quadrat, samples were counted and collected for identification and measurements. There was a significant difference in species assemblages in March (R = 0.557, P = 0.001) and June (R = 0. 618, P = 0.001) among all sites. There was a correlation between macroinvertebrate communities and sites due to environmental differences such as the type of habitat, water temperatures and human harvesting. Alien invasive mussels such as M. galloprovincialis and S. patagonicus had a significant reduced size (P < 0.05) in disturbed sites compared to control sites in both months. Majority of the limpet species such as S. argenvillei and C. granatina only had a significant smaller size (P < 0.05) in March and showed no significant difference in June. Oxystele variegata had larger sizes at control sites compared to disturbed sites in both months. There was a significant difference in species diversity between disturbed and less disturbed sites in both March (Z = -2.905, P = 0.002) and June (Z= -3.373, P < 0.001) indicating that both control sites had a greater species diversity than the disturbed sites. Human harvesting and trampling along with natural variation may play a crucial role in species assemblage structure, size and species diversity along the Namibian intertidal rocky shore. This study may be useful in filling the knowledge gap about the rocky intertidal structure along the Namibian coast and possibly identifying coastal management requirements.
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science (Biodiversity Management and Research)
Keywords
Human disturbance, Macroinvertebrates, Biodiversity, Biomonitors, Rocky shore