Marine litter in mangroves comes mainly from poor waste management practices and its abundance is increased by natural catastrophes occurrence that affects coastal settlements, as occurred in November-2020, when two hurricanes (ETA and IOTA) destroyed homes and deposited litters in mangroves of the Providencia and Santa Catalina islands, in the Colombian Caribbean. This study aims to assess the litter pollution in mangrove forests of these islands after Hurricane IOTA. Litter pollution was high in mangroves near urban areas and low in mangroves with little urban influence. In three mangrove sectors with high pollution, litter densities of 0.4–1.4 items m⁻² and masses of 0.1–1.2 kg m⁻² were determined; the majority were megalitter (sizes >1 m). Plastics were the most abundant (>60%). Local community is aware of the litter pollution problem and their participation in scientific research and mangroves recovery is key to understanding the impacts of natural and anthropogenic events and for ecosystem conservation.

Marine pollution is increasing, and pinnipeds are commonly affected by entanglement in waste. We investigated entanglement rates, common materials, and the demographic profile of Cape fur seals (Arctocephalus pusillus pusillus) affected at two Namibian colonies. Overall, we identified 366 cases of entanglement, and present a global rate of entanglement of 0.17%. Entanglement rates were 0.17% and 0.15% for the Pelican Point and Cape Cross colonies, respectively. We identified 17% more entanglements through photographs than binocular scans. Of the 347 entanglements analysed in detail, juveniles were most commonly affected and fishing materials were the primary cause of entanglements (53%), with 8% of entangled seals exhibiting ‘very severe’ injuries. Overall, 191 individuals were successfully disentangled, and citizen scientists contributed 51% of total entanglement data. We highlight the negative impact of plastic marine waste among seals and the importance of disentanglement for individual animal welfare.

Beaches are good indicators for local microplastic distribution and pollution. Multiple methods have been developed for extracting microplastics from sediment through density separation. However, the chemicals applied are often expensive and harmful to the user or the environment. We briefly review the problems associated with the use of these chemicals and present a new floatation medium, potassium carbonate (K₂CO₃), that has many advantages over other available media. It is non-toxic and cheap, and with a density of 1.54 g/cm³ the K₂CO₃ solution yielded a mean recovery rate of around 90% for PVC, one of the densest polymers, that cannot be easily extracted with alternative floatation media. We propose that the use of K₂CO₃ is particularly promising for long term and large-scale monitoring studies, because it allows involving citizen scientists in such studies, leading to an increased public awareness of the plastic problem in the seas.

The study presents the results of the field expedition in the Russian Arctic held by a group of NGO members, scientists and volunteers in summer-autumn 2020 in the Arkhangelsk Region (Russia). The survey showed microplastics presence in 7 out of 13 remote and sparsely inhabited locations in lakes, rivers and coastal areas of the White Sea basin, with microplastic particle average concentration 1.14 part/m³, that is in agreement with other recent regional studies. Mostly PE, PET and PVC were found. A simple, cheap and easy-to-use microplastics monitoring protocol was developed and tested to be used by volunteers in remote Arctic communities. Video-lectures and tutorials are available online in an open-aсcess mode. 200 volunteers from polar communities are trained in microplastic sampling and litter separation, learning about microplastic pollution, including local residents, schoolchildren and students.

Marine litter on Spanish beaches is assessed through two monitoring programmes: the Official Monitoring Programme of Marine Litter on Beaches (BM-1) developed by the Spanish Ministry for the Ecological Transition and the Demographic Challenge and the Citizen Science Monitoring Programme (BM-7) that provides beach litter data from voluntary clean-up initiatives. So far, the data provided by both programmes have been analysed separately although their integration could improve the assessment of the situation of Spanish beaches regarding marine litter. To this end, this paper studies the possible integration of both datasets through the calculation of a baseline value for marine litter on Spanish beaches. Statistical analysis of data shows that both datasets produce similar values and also integrate in a consistent way to achieve a value of 128 items/100 m as a baseline value for beach litter in Spain.

Seasonal distribution of Marine Litter (ML) on Santos beaches was assessed using a citizen science strategy. Plastics and cigarette butts (CB) were the dominant items in all sampling campaigns. Seasonal distribution did not result in significant differences for most items. Plastic and CB amounts were high in summer compared to autumn. For all sampled sites the presence of beach users influenced ML densities. However, results showed that some sites presented an additional influence of local hydrodynamic. Moderate amounts of hazardous items including metal, glass, CB, sanitary waste and plastic tubes used to pack and market illicit drugs represented between 20.8 and 31% of all ML over the seasons. The beaches of Santos were classified as dirty in autumn and spring and as extremely dirty in winter and summer. These findings can serve as a baseline to support mitigating actions by public authorities and start monitoring programs of ML not only in Santos but also in other urbanized beaches.

The toxic benthic dinoflagellate Ostreopsis ovata causes harmful algal blooms. During five years, citizens have monitored blooms of O. cf. ovata along the coast of Molfetta city facing the Adriatic Sea. Coscinodiscus spp., Licmophora spp., Gyrosigma spp. and Achnantes spp. diatoms were also quantified. O. cf. ovata was detected from spring up to winter, however, blooms always occurred in summer. Correlation with nine weather parameters was relatively strong with seawater temperature, dew point and air temperature. Dew point has never been reported before as key parameter. Blooms of O. cf. ovata were preceded by lag period during which conditions permitted proliferation but no proliferation observed. Furthermore, dew point, seawater and air temperature only moderately correlated with proliferation of Coscinodiscus spp. However, correlation between blooms of O. cf. ovata and Coscinodiscus spp. was relatively strong. Correlation between proliferation of O. cf. ovata and Gyrosigma spp. was very weak, while moderate and negative with Licmophora spp. or Achnantes spp.

In the “contributory” citizen science project INSIGNIA, beekeepers carried out non-invasive sampling of their own honey bee colonies for an environmental investigation of pesticide residues and pollen plant origin. We surveyed several traits and attitudes of 69 of the volunteering beekeepers from ten countries. We found that their motivation was similar to that found in previous studies of environmental volunteer motivation, with helping the environment and contributing to scientific knowledge being strong motivators. Our results suggest that receiving laboratory analysis results of the samples from their colonies is the most meaningful way of appreciation for beekeepers, but is not their primary reason for participation. A citizen scientist beekeeper in this study spent on average 10.4 working hours on the project during a sampling season. Our study indicates that most of our volunteers would participate in similar future investigations, or would recommend participation to other beekeepers, underlining the potential of beekeepers as citizen scientists in honey bee research.