Physical Adsorption of Charged Plastic Nanoparticles Affects Algal Photosynthesis

Abstract

The physical adsorption of nanosized plastic beads onto a model cellulose film and two living algal species, Chlorella and Scenedesmus, has been studied. This adsorption has been found to ubiquitously favor positively charged over negatively charged plastic beads due to the electrostatic attraction between the beads and the cellulose constituent of the model and living systems. Such a charge preference is especially pronounced for Chlorella and Scenedesmus, whose binding with the plastic beads also depended upon algal morphology and motility, as characterized by the Freundlich coefficients. Using a CO 2 depletion assay, we show that the adsorption of plastic beads hindered algal photosynthesis, possibly through the physical blockage of light and air flow by the nanoparticles. Our ROS assay further indicated that plastic adsorption promoted algal ROS production. Such algal responses to plastic exposure may have implications on the sustainability of the aquatic food chain.

Nanoplastics in the Aquatic Environment. Critical Review

“…199.3 ± 176.3 nm (range 100-500 nm) after 28 days, using TEM. Bhattacharya et al (2010) measured substantial binding or heteroaggregation of 20 nm polystyrene particles with freshwater phytoplankton cells. Because of their low density, it is often assumed that substantial fractions of the total load of plastic particles from riverine sources reach the sea (Cózar et al 2014;Wagner et al 2014).…”

“…This study used an air-inhalation exposure scenario and the question remains to what extent this can be translated to aquatic systems, where aggregation would limit the concentrations of free NPs and direct inhalation of air-dispersed NPs does not occur. Bhattacharya et al (2010) showed that adsorption of 1.8-6.5 mg/L of 20 nm polystyrene particles (yet present as agglomerates) hindered algal photosynthesis, possibly through reduction of light intensity and of air flow by the nanoparticles, and stimulated Reactive Oxygen Species (ROS) production. Ward and Kach (2009) showed that mussels (Mytilus edulis) and oysters (Crassostrea virginica) take up 100 nm PS beads, especially when incorporated into aggregates.…”

“…Detection methods are in an early stage of development but to date no NPs have been detected in natural aquatic systems. Some first prognostic bioaccumulation and effect studies have been performed (Brown et al 2001;Ward and Kach 2009;Bhattacharya et al 2010;Wegner et al 2012;Lee et al 2013;Casado et al 2013;Besseling et al 2014b) but there is no systematic effect assessment for relevant aquatic species let alone for the community or ecosystem level. Apart from physiological consequences, NPs might also have chemical effects.…”

Microplastic Size-Dependent Toxicity, Oxidative Stress Induction, and p-JNK and p-p38 Activation in the Monogonont Rotifer (Brachionus koreanus)

“…20 Similarly, in the algae Chlorella and Scenedesmus, polystyrene microbeads have been shown to generate ROS and inhibit photosynthetic ability. 18 Despite growing concern regarding the deleterious effects of microplastics on marine organisms, particularly on filter feeding plankton at the bottom of the food chain, the defense mechanisms of marine organisms in response to microplastic ingestion have not yet been reported.…”

Marine Litter: Composition in Eastern Aegean Coasts

“…Furthermore, in open coasts, wave action may transfer a large portion of the marine debris from shallow areas to the shore [2]. Marine pollution leads to: • Nanopolystyrene beads can inhibit photosynthesis and cause oxidative stress in algae [26].…”