Benthic macrofauna communities reflect eutrophic condition in a low-inflow estuary

• Published in: Regional studies in marine science 2024-02, Vol.70, p.103351, Article 103351
• Main Authors: Ndhlovu, Aldwin, Adams, Janine B., Lemley, Daniel A., Nhleko, Jabulile, Rishworth, Gavin M.
• Format: Article
• Language: English
• Subjects: Estuarine systems; Indicators; Macroinvertebrates; Pollution
• ISSN: 2352-4855; 2352-4855
• DOI: 10.1016/j.rsma.2023.103351

Nutrient enrichment drives potentially severe changes in low-inflow and temporarily closed estuaries where tidal mixing and freshwater flushing is limited, and bottom-water anoxia occurs frequently. Our research assesses the influence of nutrient enrichment by comparing macrobenthos community metrics in a persistently hypereutrophic South African estuary. This is then compared to published literature for an estuary with a similar catchment size and mean annual runoff, but which experiences limited anthropogenic nutrient input. Macroinvertebrate abundance and richness were higher in an estuary with limited anthropogenic nutrient loading, and this varied seasonally for both estuaries. Oxygen saturation had a significant influence on taxonomic level abundances, with lower oxygen levels in the polluted estuary reducing macroinvertebrate abundances. Macroinvertebrates tolerant of organic pollution (e.g., Oligochaeta) were also more abundant in the polluted estuary. This study highlights the effects of increased nutrient loading in low-inflow estuaries and confirms the supposition from several previous studies that macrozoobenthos could be used as a responsive tool from a bioindicator perspective to monitor eutrophication. •Nutrient enrichment drives changes that can be severe in low-inflow and temporarily closed estuaries.•Relatively pristine estuaries have higher macroinvertebrate species abundances and richness.•Macroinvertebrates tolerant of organic pollution were more abundant in estuaries exposed to wastewater effluent discharges.•Lower oxygen levels in a nutrient enriched estuary resulted in reduced macroinvertebrate abundances.•Nutrient enrichment negatively affects the abundance and community composition of estuarine benthic macroinvertebrates.