Porewater pathogenic bacteria variation across a recreational gradient in Zone A, Langebaan Lagoon

Ramashia, Tjale Winnie

Porewater pathogenic bacteria variation across a recreational gradient in Zone A, Langebaan Lagoon

Thesis / Dissertation

2026

Publisher

University of Cape Town

Department

Department of Biological Sciences

Faculty

Faculty of Science

Abstract

Anthropogenic pressures, such as recreational activities, are intensifying in coastal areas worldwide, posing great challenges to understanding and managing their impacts on coastal ecosystems and human health. Microbial pathogen communities are responsive to such stressors, yet their dynamics remain understudied in sediments. This study investigates spatial and seasonal variation in benthic (porewater) microbial pathogen communities along a recreational gradient in Zone A of Langebaan Lagoon, South Africa. Zone A experiences high human activity, especially near access points, with intensity decreasing along the ±800 m intertidal transect used in this study. Four equidistant sites were sampled during summer and winter spring tides in 2024. Data collected included physicochemical parameters (dissolved oxygen levels, salinity, and water temperature), sediment properties (particle size, penetrability, organic matter content and colouration), people counts, porewater nutrient concentrations, and samples for pathogenic bacteria bioindicators (i.e., enterococci, faecal coliforms, heterotrophic bacteria, Pseudomonas aeruginosa, and Escherichia coli) in both porewater and the water column. Sites with greater recreational activity had higher pathogenic bacteria counts in winter, but this trend reversed in summer. Porewater bacteria counts were ~300 times higher than in the water column, and overall pathogenic bacteria counts were observed to be generally higher in winter compared to summer. Sites with more human activity showed depleted sediment oxygen, increased sediment compaction, and elevated sediment ammonia levels. Overall, the results suggest that while human recreation influences benthic processes and sediment microbial communities, the interaction of seasonal environmental changes and recreational intensity drives porewater pathogen dynamics. These findings underline the importance of accounting for both anthropogenic and natural factors in managing intertidal ecosystems, with future research needed to explore the roles of rainfall, runoff, nutrient loading and other episodic events in shaping porewater pathogenic bacteria dynamics over time.

Keywords

ocean sciences

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Masters

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