Heavy Metals Assimilation by Native and Non-Native Aquatic Macrophyte Species: A Case Study of a River in the Eastern Cape Province of South Africa

Abstract

There is continuous deterioration of freshwater systems globally due to excessive anthropogenic inputs, which severely affect important socio-economic and ecological services. We investigated the water and sediment quality at 10 sites along the severely modified Swartkops River system in the Eastern Cape Province of South Africa and then quantified the phytoremediation potential by native and non-native macrophyte species over a period of 6 months. We hypothesized that the presence of semi and permanent native and non-native macrophytes mats would reduce water and sediment contamination through assimilation downriver. Our results were variable and, thus, inconsistent with our hypotheses; there were no clear trends in water and sediment quality improvement along the Swartkops River. Although variable, the free-floating non-native macrophyte, Pontederia (=Eichhornia) crassipes recorded the highest assimilation potential of heavy metals in water (e.g., Fe and Cu) and sediments (e.g., Fe and Zn), followed by a submerged native macrophyte, Stuckenia pectinatus, and three native emergent species, Typha capensis, Cyperus sexangularis, and Phragmites australis. Pollution indices clearly showed the promising assimilation by native and non-native macrophytes species; however, the Swartkops River was heavily influenced by multiple non-point sources along the system, compromising the assimilation effect. Furthermore, we emphasise that excessive anthropogenic inputs compromise the system’s ability to assimilate heavy metals inputs leading to water quality deterioration.

Perceptions and knowledge of ecosystem services in urban river systems, Eastern Cape, South Africa

“…This is likely because of high levels of pollution of the river. The Swartkops River is regarded as one of the most polluted river systems in the Eastern Cape of South Africa (Tshithukhe et al 2021). High levels of E. coli, pharmaceutical compounds, metals and other chemical pollutants have previously been reported (Odume et al 2012; Farounbi and Ngqwala 2020; Vumazonke et al 2020;Ohoro et al 2021).…”

Bioremediation of Aquatic Environments Contaminated with Heavy Metals: A Review of Mechanisms, Solutions and Perspectives

“…Water pollution by organic and inorganic contaminants represents a current challenge, and the attempt to remove these elements is the object of study of different studies [4]. Several pollutants have recently been analyzed in the literature for their remediation by biological agents, such as pharmaceuticals and cosmetics [5]; polycyclic aromatic hydrocarbons [6]; artificial chemicals [7]; microplastics [8]; agrochemicals and pesticides [9]; primary nutrients [10]; HM [8,[11][12][13][14][15].…”

Heavy Metal Contamination of the River Nile Environment, Rosetta Branch, Egypt

“…Aquatic macrophytes are good biological monitors of heavy metals. They play significant roles in water quality control, oxygen production, nutrient cycling, and sediment stabilization, and they serve as aquatic life habitat and shelter (Tshithukhe et al, 2021). Metals can accumulate in high levels in aquatic macrophytes from the water or/and sediments, proving the utility of plants as aquatic biomonitors.…”

“…Furthermore, monitoring the buildup of persistent contaminants in aquatic macrophytes can offer time-integrated data on harmful chemicals in aquatic systems (Harguinteguy et al, 2014). The levels of heavy metals in aquatic macrophytes depend on the plant species, the plant sections, the metal levels in the growth environment, and the macrophytes' selective capacity to absorb different substances (Tshithukhe et al, 2021).…”