Hannes K. Imhof

Contamination of beach sediments of a subalpine lake with microplastic particles

Summary Plastic waste is of increasing concern in marine ecosystems [1–3]. Buoyant plastic particles accumulate in pelagic habitats whereas non-floating debris accumulates on the seafloor and in beach sediments, posing risk to the respective communities [1–4]. Microplastic particles (

Beyond the ocean: contamination of freshwater ecosystems with (micro-)plastic particles

Massive accumulation of plastic particles has been reported for marine ecosystems around the world, posing a risk to the biota. Freshwater ecosystems have received less attention despite the majority of plastic litter being produced onshore and introduced into marine environments by rivers. Some studies report not only the presence of microplastics in freshwater ecosystems, but show that contamination is as severe as in the oceans. In continental waters microplastics have been observed in both sediments (predominantly lakeshores but also riverbanks) and water samples (predominantly surface water of lakes and rivers). This review highlights recent findings and discusses open questions, focusing on the methodology of assessing this contaminant in freshwater ecosystems. In this context, method harmonization is needed in order to obtain comparable data from different environmental compartments and sites. This includes sampling strategies (at spatial and temporal 18 scales), sample treatment (taking into consideration high levels of organic matter and suspended 19 solids) and reliable analytical methods to identify microplastics.

Spatial and temporal variation of macro-, meso- and microplastic abundance on a remote coral island of the Maldives, Indian Ocean

Plastic debris is ubiquitous in the marine environment and the worlds shores represent a major sink. However, knowledge about plastic abundance in remote areas is scarce. Therefore, plastic abundance was investigated on a small island of the Maldives. Plastic debris (>1mm) was sampled once in natural long-term accumulation zones at the north shore and at the high tide drift line of the south shore on seven consecutive days to quantify daily plastic accumulation. Reliable identification of plastic debris was ensured by FTIR spectroscopy. Despite the remoteness of the island a considerable amount of plastic debris was present. At both sites a high variability in plastic abundance on a spatial and temporal scale was observed, which may be best explained by environmental factors. In addition, our results show that snapshot sampling may deliver biased results and indicate that future monitoring programs should consider spatial and temporal variation of plastic deposition.

Applications of Computational 3D–Modeling in Organismal Biology

Christian Laforsch1,2, Hannes Imhof1,2, Robert Sigl1,2, Marcus Settles3, Martin Hes2,4 and Andreas Wanninger5 1Department of Biology II, Ludwig-Maximilians-University Munich, 2GeoBioCenter, Ludwig-Maximilians-University Munich, 3Institute of Radiology, Technical University of Munich, 4Department of Biology I, Ludwig-Maximilians-University Munich, 5Dept. of Integrative Zoology, Faculty of Life Sciences, University of Vienna, 1,2,3,4Germany 5Austria

Variation in plastic abundance at different lake beach zones - A case study

Plastic particles in marine and freshwater environments span from macroscopic to microscopic size classes. Each may have a different impact on individuals, populations and ecosystems, but still the wide variety of methods used in beach sediment sampling inhibit comparisons among studies and therefore hampers a risk assessment. A large portion of the uncertainties is due to differing sampling strategies. By quantifying the alongshore distribution of macro- and microplastic particles within five beaches of Lake Garda, we aim to shed light on the accumulation behavior of microplastic particles at an exemplary lake which might give indications for potential sampling zones. The identification of plastic at the single particle level with a spatial resolution down to 1μm was performed by Raman microspectroscopy. Given the time consuming approach we reduced the number of samples in the field but increased the spatial area where a single sample was taken, by utilizing a transect approach in combination with sediment cores (5cm depth). The study revealed that, in comparison to the water line and the high-water line, the drift line of all five beaches always contained plastic particles. Since the drift line accumulate particulate matter on a relatively distinct zone, it will enable a comparable sampling of microplastic particles. The applied sampling approach provided a representative method for quantifying microplastic down to 1μm on a shore consisting of pebbles and sand. Hence, as first step towards a harmonization of beach sediment sampling we suggest to perform sampling at the drift line, although further methodological improvements are still necessary.

Multi-temporal surveys for microplastic particles enabled by a novel and fast application of SWIR imaging spectroscopy – Study of an urban watercourse traversing the city of Berlin, Germany

Following the widespread assumption that a majority of ubiquitous marine microplastic particles originate from land-based sources, recent studies identify rivers as important pathways for microplastic particles (MPP) to the oceans. Yet a detailed understanding of the underlying processes and dominant sources is difficult to obtain with the existing accurate but extremely time-consuming methods available for the identification of MPP. Thus in the presented study, a novel approach applying short-wave infrared imaging spectroscopy for the quick and semi-automated identification of MPP is applied in combination with a multitemporal survey concept. Volume-reduced surface water samples were taken from transects at ten points along a major watercourse running through the South of Berlin, Germany, on six dates. After laboratory treatment, the samples were filtered onto glass fiber filters, scanned with an imaging spectrometer and analyzed by image processing. The presented method allows to count MPP, classify the plastic types and determine particle sizes. At the present stage of development particles larger than 450 μm in diameter can be identified and a visual validation showed that the results are reliable after a subsequent visual final check of certain typical error types. Therefore, the method has the potential to accelerate microplastic identification by complementing FTIR and Raman microspectroscopy. Technical advancements (e.g. new lens) will allow lower detection limits and a higher grade of automatization in the near future. The resulting microplastic concentrations in the water samples are discussed in a spatio-temporal context with respect to the influence (i) of urban areas, (ii) of effluents of three major Berlin wastewater treatment plants discharging into the canal and (iii) of precipitation events. Microplastic concentrations were higher downstream of the urban area and after precipitation. An increase in microplastic concentrations was discernible for the wastewater treatment plant located furthest upstream though not for the other two.

Do microplastic particles affect Daphnia magna at the morphological, life history and molecular level?

Microplastic particles are ubiquitous not only in marine but also in freshwater ecosystems. However, the impacts of microplastics, consisting of a large variety of synthetic polymers, on freshwater organisms remains poorly understood. We examined the effects of two polymer mixtures on the morphology, life history and on the molecular level of the waterflea Daphnia magna (three different clones). Microplastic particles of ~40 μm were supplied at a low concentration (1% of the food particles) leading to an average of ~30 particles in the digestive tract which reflects a high microplastic contamination but still resembles a natural situation. Neither increased mortality nor changes on the morphological (body length, width and tail spine length) or reproductive parameters were observed for adult Daphnia. The analyses of juvenile Daphnia revealed a variety of small and rather subtle responses of morphological traits (body length, width and tail spine length). For adult Daphnia, alterations in expression of genes related to stress responses (i.e. HSP60, HSP70 & GST) as well as of other genes involved in body function and body composition (i.e. SERCA) were observed already 48h after exposure. We anticipate that the adverse effects of microplastic might be influenced by many additional factors like size, shape, type and even age of the particles and that the rather weak effects, as detected in a laboratory, may lead to reduced fitness in a natural multi-stressor environment.

Microplastic Contamination in Freshwater Systems: Methodological Challenges, Occurrence and Sources

Abstract Microplastics have received significant attention by the scientific community during the past decade. Knowledge on this recently considered contamination has been constantly growing, although the studies are mainly oriented toward marine environments. The focus on plastic pollution in freshwater environments has been limited even with an increasing number of studies. The fate and the transfer routes of plastics in continental are not yet determined. In addition, these studies use various and constantly evolving methodologies, leading to a lack of homogeneous and standardized methods. This hinders comparability between studies and limits potential interpretations and conclusions on plastic repartition and distribution in the continental environment. In this chapter, the studies describing the plastic contamination in freshwater are reviewed. The different methodologies for microplastic sampling, sample preparation and analysis are discussed. The occurrences of these particles in limnetic systems are also presented along with an overview on their different potential sources and input pathways into freshwater.