The first evidence of microplastics in plant-formed fresh-water micro-ecosystems: Dipsacus teasel phytotelmata in Slovakia contaminated with MPs

Microplastics were detected in six of 171 water-filled leaf cavities examined in teasel plants at two localities in eastern Slovakia, providing the first documented evidence of these particles in phytotelmata, according to the field study. The unexpected discovery was made while researchers were sampling the seasonal dynamics of organisms living in the temporary freshwater micro-ecosystems formed by the leaves of Dipsacus.

Phytotelmata are generally non-permanent aquatic micro-ecosystems in plants. In teasels, opposite leaves clasp the stem and form cup-like structures that collect rainwater and sediment. These cavities are small and persist for only about three to four months, making them overlooked and relatively short-lived sampling environments.

The investigators collected water and sediment from leaf axils on five plants at each of two sites, near the villages of Demjata and Kapušany. Sampling took place at the end of each of five 14-day collection periods in 2021, using sterile containers to prevent contamination from other sources. The 50 sampled teasels contained 171 functioning phytotelmata, from which 4,596 millilitres of water and sediment were collected in total.

After the initial observation, samples were examined in a sterile Petri dish under a stereomicroscope. Positive samples were photographed and measured, and 3 millilitres from each positive sample were analysed in 0.5-millilitre increments after thorough mixing. The reported concentrations were converted to values for one millilitre of sample. The Leica M205MC stereomicroscope, paired with a digital camera and used at magnifications from 7.8 to 160 times, could capture and measure particles with a minimum size of 1 micrometre.

Positive phytotelmata accounted for 3.5% of the 171 samples examined. They were recorded during two consecutive sampling periods, from 29 June to 12 July and from 13 to 26 July 2021, at different levels on the plants and at both localities. The six positive samples yielded estimated concentrations of 101.75 to 408.87 microplastic particles per millilitre, based on the analysed three-millilitre subsamples and their conversion to a one-millilitre basis.

The particles were predominantly fibres in blue, black, red and white, measuring 141 micrometres to 2.4 millimetres in length. Blue and orange fragments were also present, with diameters of 9 to 81 micrometres. The fibres and fragments were identified and measured microscopically; the study did not report chemical polymer identification, and the researchers did not experimentally trace the particles to a specific contamination source.

Suspended atmospheric microplastics were proposed as the most probable contamination pathway because fibres and fragments were also dominant in samples of atmospheric microplastics cited by the authors. The researchers also identified transport by snails as a second possible route, either through particles carried on or within their bodies or through ingestion and later dispersal. Living or drowned snails and their excrement were frequently observed in the teasel cavities, while the authors reported no contamination sources other than the atmosphere in the surrounding soil, vegetation and landscape at the two sites. These pathway explanations remained hypotheses rather than source-tracing results.

The low proportion of positive cavities may be related to the density of surrounding vegetation and to the position and orientation of the water-filled leaf axils, according to the study. The authors proposed testing whether the contamination pathway affects the usefulness of phytotelmata as indicators of microplastic pollution and whether their microplastic concentrations reflect environmental concentrations. They also suggested investigating whether the sequence of phytotelmata on individual teasels could reveal temporal differences in contamination during the growing season.

The study has a limited geographic scope and covers only two Slovak localities, 50 plants and one growing season. It was an observational field sampling study with incidental detection of microplastics rather than a controlled experiment, and it did not establish that the particles came from atmospheric deposition, snails or another specific source. The results therefore demonstrate the presence of microplastics in sampled teasel phytotelmata, while their origin, temporal dynamics and usefulness as environmental indicators require further testing.

Subject of Research: Field detection of microplastics in Slovak teasel phytotelmata and proposed contamination pathways

Article Title: The first evidence of microplastics in plant-formed fresh-water micro-ecosystems: Dipsacus teasel phytotelmata in Slovakia contaminated with MPs

Article References: Fogašová, K., Manko, P., & Oboňa, J. (2022). The first evidence of microplastics in plant-formed fresh-water micro-ecosystems: Dipsacus teasel phytotelmata in Slovakia contaminated with MPs. BioRisk, 18, 133-143. https://doi.org/10.3897/biorisk.18.87433

Image Credits: AI Generated

DOI: 10.3897/biorisk.18.87433

Keywords: microplastics, phytotelmata, teasel, Dipsacus, freshwater micro-ecosystems, Slovakia, atmospheric deposition, snail transport, environmental monitoring, first, evidence, plant-formed