Downward migrating microplastics in lake sediments are a tricky indicator for the onset of the Anthropocene.

Plastics are a recent particulate material in Earth's history. Because of plastics persistence and wide-range presence, it has a great potential of being a global age marker and correlation tool between sedimentary profiles. In this research, we query whether microplastics can be considered among the array of proxies to delimit the Anthropocene Epoch (starting from the year 1950 and above). We present a study of microplastics deposition history inferred from sediment profiles of lakes in northeastern Europe. The sediments were dated with independent proxies from the present back to the first half of the 18th century. Regardless of the sediment layer age, microplastic particles were found throughout the cores in all sites. Depending on particles' aspect ratio, less elongated particles were found deeper, while more elongated particles and fibers have reduced mobility. We conclude that interpretation of microplastics distribution in the studied sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.

Dataset on microplastic concentrations, characteristics, and chemical composition in the marine surface waters of Latvia - the Eastern Gotland basin and the Gulf of Riga.

The dataset provides information on spectroscopically verified microplastics, both particles and fibers, from 44 marine surface water samples of two Baltic Sea sub-basins - the semi-enclosed Gulf of Riga and the Eastern Gotland Basin. Sampling was performed by using Manta trawl with a mesh size of 300 µm. Thereafter, the organic material was digested with sodium hydroxide, hydrogen peroxide and enzymes. Samples were filtered on glass fiber filters and analyzed visually, registering the shape, size, and color of each item. Where feasible, the polymer type was determined using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy method. The number of plastic particles per m3 of filtered water was determined. The data presented in this article may be useful for further research on microplastic pollution, meta-analysis and calculation of microplastic flow. Interpretation and analysis of total acquired data on micro debris and microplastics are reported in the article "Occurrence and spatial distribution of microplastics in the surface waters of the Baltic Sea and the Gulf of Riga".

Hide-and-seek: Threshold values and contribution towards better understanding of recovery rate in microplastic research.

Microplastic pollution has become one of the most pressing environmental issues. A fundamental criterion for risk assessment is the concentration of found microplastic that can be altered during microplastic isolating from the sample. Recovery rate (i.e. positive control) is an important feedback component that identifies accuracy, quality and efficiency of sample processing, same as physical and chemical impact. Here, using 100 µm red polystyrene (PS) beads we have tested some methodological steps that can be responsible for the possible microplastic losses during sample treatment and based on that, we provided a recovery rate threshold values. Our results support that the choice of the extraction method (vacuum filtration versus wet sieving) results in lower recoverability when vacuum filtration is used and that used separatory funnels size versus material amount impacts the efficiency or recoverability in density separation. We have also analysed microplastic recovery rate when different samples treatment steps from widely used isolation protocols (sediment and water) were applied and our results suggest that there are a number of factors affecting recovery rates, of which physical effects (loss by consecutive treatment steps due to material transfer) are more important than possible chemical degradation.•Sample filtration method determines recovery rate from < 40 to > 80%.•The number of sample processing steps involving transfer has a direct impact on recovery rate.•As a measure of quality assurance, recovery rate thresholds are introduced.

Occurrence and spatial distribution of microplastics in the surface waters of the Baltic Sea and the Gulf of Riga.

The study is comparing microplastic debris distribution and composition in the Gulf of Riga and the Eastern Gotland Basin, Baltic Sea. Samples from 44 stations were collected from coastal and open water sites using Manta trawl (mesh size 300 µm). The natural organic material was digested sequentially with sodium hydroxide, hydrogen peroxide and enzymes. Thereafter, micro-debris (16,315 particles) was identified by visual analysis and 5285 particles were analyzed with Attenuated Total Reflection Fourier Transform Infrared spectroscopy method. The abundance of particles varied from 0.09 to 4.43 particles per m-3. The fibers accounted for 66.1% of all encountered particles while the fragments for 30.2%. The predominant polymer types were polyethylene (77.9%) and polypropylene (11.1%). The relative proportion among polymer types varied considerably from station to station. The encountered concentrations of micro-debris were well in range of values reported from other regions of the Baltic Sea.

Correction to: Zooplankton indicator-based assessment in relation to site location and abiotic factors: a case study from the Gulf of Riga.

This paper, published in Environ Monit Assess 192, 147 (2020), contains errors in Table 5.

Zooplankton indicator-based assessment in relation to site location and abiotic factors: a case study from the Gulf of Riga.

There are a number of zooplankton parameters proposed as indicators to evaluate environmental status of marine ecosystems. Mean size and total stock (MSTS) is the only zooplankton-based and HELCOM (Baltic Marine Environment Protection Commission - Helsinki Commission)-approved core indicator. MSTS was developed to evaluate the environmental status of the Baltic Sea based on total biomass (or abundance) and mean body weight of mesozooplankton. This indicator reflects status of the food web and zooplankton biodiversity. Both are qualitative descriptors for determining good environmental status (GES) as defined by the EU Marine Strategy Framework Directive 2008/56/EC. However, the existing indicator concept is applicable to the extent that it characterizes off-shore pelagic habitats, while use of MSTS for coastal habitats remains challenging. In this case study, we aimed to assess and discuss performance of MSTS applied to mesozooplankton data from the shallow Gulf of Riga. Both off-shore and coastal communities were included in the study. MSTS responses to variable environmental factors (temperature, salinity and riverine runoff) were analysed. Temporal variations in temperature revealed response in mean size, whereas salinity covaried with total stock (both - biomass and abundance). However, spatial variations of MSTS parameters stayed unexplained. The results demonstrate difficulties with and provide possible solutions for MSTS-based assessment, with a particular emphasis on coastal waters. The use of mesozooplankton abundance as a determinant parameter for assessment of coastal waters and substitution of the corresponding 99% confidence interval of the mean as an assessment value instead of the mean have been considered.

Fauna of Cladocera and Copepoda from Xinjiang Uyghur Autonomous Region (China).

This study evaluates the species composition of Cladocera and Copepoda in the five lakes of the Bogda-Shan Mountain range and in the floodplain of the Tarim and Konchedarya rivers located in the Xinjiang Uygur Autonomous Region of China (Xinjiang). We collected seven species of Cladocera and six species of Copepoda. Seven species were identified as new for Xinjiang fauna, and two species (Cyclops cf. herberti Einsle, 1996, and Eucyclops roseus Ishida, 1997) were first records for China. Herein, we characterize the distribution ranges for the detected species and provide taxonomic remarks. The total species list for water bodies in Xinjiang compiled from original data and available literature includes 56 species of Cladocera and 33 species of Copepoda. We also discuss the biogeographical structure of Cladocera and Copepoda faunas in Xinjiang.