Finding the Balance between Research and Monitoring: When Are Methods Good Enough to Understand Plastic Pollution?

Plastic pollution is an international environmental problem. Desire to act is shared from the public to policymakers, yet motivation and approaches are diverging. Public attention is directed to reducing plastic consumption, cleaning local environments, and engaging in citizen science initiatives. Policymakers and regulators are working on prevention and mitigation measures, while international, regional, and national bodies are defining monitoring recommendations. Research activities are focused on validating approaches to address goals and comparing methods. Policy and regulation are eager to act on plastic pollution, often asking questions researchers cannot answer with available methods. The purpose of monitoring will define which method is implemented. A clear and open dialogue between all actors is essential to facilitate communication on what is feasible with current methods, further research, and development needs. For example, some methods can already be used for international monitoring, yet limitations including target plastic types and sizes, sampling strategy, available infrastructure and analytical capacity, and harmonization of generated data remain. Time and resources to advance scientific understanding must be balanced against the need to answer pressing policy issues.publishedVersio

Role of cAMP-Dependent Protein Kinase during Growth and Early Development of Dictyostelium discoideum

AbstractcAMP-dependent protein kinase (PKA) is an essential regulator of gene expression and cell differentiation during multicellular development of Dictyostelium discoideum. Here we show that PKA activity also regulates gene expression during the growth phase and at the transition from growth to development. Overexpression of PKA leads to overexpression of the discoidinIγ promoter, while expression of the discoidinIγ promoter is reduced when PKA activity is reduced, either by expression of a dominant negative mutant of the regulatory subunit or by disruption of the gene for the catalytic subunit (PKA-C). The discoidin phenotype of PKA-C null cells is cell autonomous. In particular, normal secretion of discoidin-inducing factors was demonstrated. In addition, PKA-C null cells are able to respond to media conditioned by PSF and CMF. We conclude that PKA is a major activator of discoidin expression. However, it is not required for production or transduction of the inducing extracellular signals. Therefore, PKA-dependent and PKA-independent pathways regulate the expression of the discoidin genes

At second glance: The importance of strict quality control – A case study on microplastic in the Southern Ocean key species Antarctic krill, Euphausia superba

The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of micro-plastic (MP), by testing different sample volumes, extraction approaches, and applying hyperspectral imaging Fourier-transform infrared spectroscopy (μFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide

Characterizing the multidimensionality of microplastics across environmental compartments

Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of >60 000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR- imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks

Toward the systematic identification of microplastics in the environment: evaluation of a new independent software tool (siMPle) for spectroscopic analysis

Microplastics (MP) are ubiquitous within the environment, but the analysis of this contaminant is currently quite diverse, and a number of analytical methods are available. The comparability of results is hindered as even for a single analytical method such as Fourier transform infrared spectroscopy (FT-IR) the different instruments currently available do not allow a harmonized analysis. To overcome this limitation, a new free of charge software tool, allowing the systematic identification of MP in the environment (siMPle) was developed. This software tool allows a rapid and harmonized analysis of MP across FT-IR systems from different manufacturers (Bruker Hyperion 3000, Agilent Cary 620/670, PerkinElmer Spotlight 400, Thermo Fischer Scientific Nicolet iN10). Using the same database and the automated analysis pipeline (AAP) in siMPle, MP were identified in samples that were analyzed with instruments with different detector systems and optical resolutions, the results of which are discussed

Comparison of two rapid automated analysis tools for large FTIR microplastic datasets

AbstractOne of the biggest issues in microplastic (MP, plastic items  &lt;5 mm) research is the lack of standardisation and harmonisation in all fields, reaching from sampling methodology to sample purification, analytical methods and data analysis. This hampers comparability as well as reproducibility among studies. Concerning chemical analysis of MPs, Fourier-transform infrared (FTIR) spectroscocopy is one of the most powerful tools. Here, focal plane array (FPA) based micro-FTIR (µFTIR) imaging allows for rapid measurement and identification without manual preselection of putative MP and therefore enables large sample throughputs with high spatial resolution. The resulting huge datasets necessitate automated algorithms for data analysis in a reasonable time frame. Although solutions are available, little is known about the comparability or the level of reliability of their output. For the first time, within our study, we compare two well-established and frequently applied data analysis algorithms in regard to results in abundance, polymer composition and size distributions of MP (11–500 µm) derived from selected environmental water samples: (a) the siMPle analysis tool (systematic identification of MicroPlastics in the environment) in combination with MPAPP (MicroPlastic Automated Particle/fibre analysis Pipeline) and (b) the BPF (Bayreuth Particle Finder). The results of our comparison show an overall good accordance but also indicate discrepancies concerning certain polymer types/clusters as well as the smallest MP size classes. Our study further demonstrates that a detailed comparison of MP algorithms is an essential prerequisite for a better comparability of MP data.</jats:p

Generation of macro- and microplastic databases by high-throughput FTIR analysis with microplate readers

FTIR spectral identification is today’s gold standard analytical procedure for plastic pollution material characterization. High-throughput FTIR techniques have been advanced for small microplastics (10–500 µm) but less so for large microplastics (500–5 mm) and macroplastics (> 5 mm). These larger plastics are typically analyzed using ATR, which is highly manual and can sometimes destroy particles of interest. Furthermore, spectral libraries are often inadequate due to the limited variety of reference materials and spectral collection modes, resulting from expensive spectral data collection. We advance a new high-throughput technique to remedy these problems using FTIR microplate readers for measuring large particles (> 500 µm). We created a new reference database of over 6000 spectra for transmission, ATR, and reflection spectral collection modes with over 600 plastic, organic, and mineral reference materials relevant to plastic pollution research. We also streamline future analysis in microplate readers by creating a new particle holder for transmission measurements using off-the-shelf parts and fabricating a nonplastic 96-well microplate for storing particles. We determined that particles should be presented to microplate readers as thin as possible due to thick particles causing poor-quality spectra and identifications. We validated the new database using Open Specy and demonstrated that additional transmission and reflection spectra reference data were needed in spectral libraries