Searching for hotspots of neustonic microplastics in the Canary Islands

Do weathered microplastics impact the planktonic community? A mesocosm approach in the Baltic Sea

Microplastics (MPs) are ubiquitous pollutants of increasing concern in aquatic systems. However, little is still known about the impacts of weathered MPs on plankton at the community level after long-term exposure. In this study, we investigated the effects of weathered MPs on the structure and dynamics of a Baltic Sea planktonic community during ca. 5 weeks of exposure using a mesocosm approach (2 m3) mimicking natural conditions. MPs were obtained from micronized commercial materials of polyvinyl chloride, polypropylene, polystyrene, and polyamide (nylon) previously weathered by thermal ageing and sunlight exposure. The planktonic community was exposed to 2 μg L-1 and 2 mg L-1 of MPs corresponding to measured particle concentrations (10-120 μm) of 680 MPs L-1 and 680 MPs mL-1, respectively. The abundance and composition of all size classes and groups of plankton and chlorophyll concentrations were periodically analyzed throughout the experiment. The population dynamics of the studied groups showed some variations between treatments, with negative and positive effects of MPs exhibited depending on the group and exposure time. The abundance of heterotrophic bacteria, pico- and nanophytoplankton, cryptophytes, and ciliates was lower in the treatment with the higher MP concentration than in the control at the last weeks of the exposure. The chlorophyll concentration and the abundances of heterotrophic nanoflagellates, Astromoeba, dinoflagellate, diatom, and metazooplankton were not negatively affected by the exposure to MPs and, in some cases, some groups showed even higher abundances in the MP treatments. Despite these tendencies, statistical analyses indicate that in most cases there were no statistically significant differences between treatments over the exposure period, even at very high exposure concentrations. Our results show that weathered MPs of the studied conventional plastic materials have minimal or negligible impact on planktonic communities after long-term exposure to environmentally relevant concentrations.

Microplastic and mesoplastic pollution in surface waters and beaches of the Canary Islands: A review

The Canary Archipelago is a group of volcanic islands located in the North Atlantic Ocean with high marine biodiversity. This archipelago intercepts the Canary Current, the easternmost branch of the Azores Current in the North Atlantic Subtropical Gyre, which brings large amounts of litter from remote sources via oceanic transportation. It is, therefore, particularly vulnerable to marine plastic pollution. Here, we present a review of the available studies on mesoplastics and microplastics in the Canary Islands over the last decade to evaluate the level and distribution of plastic pollution in this archipelago. Specifically, we focused on data from beaches and surface waters to assess the pollution level among the different islands as well as between windward and leeward zones, and the main characteristics (size, type, colour, and polymer) of the plastics found in the Canary Islands. The concentrations of meso- and MPs on beaches ranged from 1.5 to 2972 items/m2 with a mean of 381 ± 721 items/m2. The concentration of MPs (>200 μm) in surface waters was highly variable with mean values of 998 × 103 ± 3364 × 103 items/km2 and 10 ± 31 items/m3. Plastic pollution in windward beaches was one order of magnitude significantly higher than in leeward beaches. The accumulation of MPs in surface waters was higher in the leeward zones of the high-elevation islands, corresponding to the Special Areas of Conservation (ZECs) and where the presence of marine litter windrows (MLW) has been reported. Microplastic fragments of polyethylene of the colour category "white/clear/uncoloured" were the most common type of plastic reported in both beaches and surface waters. More studies on the occurrence of MLW in ZECS and plastic pollution in the water column and sediments, including small-size fractions (<200 μm), are needed to better assess the level of plastic pollution and its fate in the Canary Islands. Overall, this review confirms that the Canary Archipelago is a hotspot of oceanic plastic pollution, with concentrations of MPs in surface waters in the highest range reported for oceanic islands and one of the highest recorded mean concentrations of beached meso- and microplastics in the world.

Does water column stratification influence the vertical distribution of microplastics?

Microplastic pollution has been confirmed in all marine compartments. However, information on the sub-surface microplastics (MPs) abundance is still limited. The vertical distribution of MPs can be influenced by water column stratification due to water masses of contrasting density. In this study, we investigated the vertical distribution of MPs in relation to the water column structure at nine sites in the Kattegat/Skagerrak (Denmark) in October 2020.A CTD was used to determine the stratification and pycnocline depth before sampling. Plastic-free pump-filter sampling devices were used to collect MPs from water samples (1-3 m3) at different depths. MPs concentration (MPs m-3) ranged from 18 to 87 MP m-3 (Median: 40 MP m-3; n = 9) in surface waters. In the mid waters, concentrations ranged from 16 to 157 MP m-3 (Median: 31 MP m-3; n = 6), while at deeper depths, concentrations ranged from 13 to 95 MP m-3 (Median: 34 MP m-3; n = 9). There was no significant difference in the concentration of MPs between depths. Regardless of the depth, polyester (47%), polypropylene (24%), polyethylene (10%), and polystyrene (9%) were the dominating polymers. Approximately 94% of the MPs fell within the size range of 11-300 μm across all depths. High-density polymers accounted for 68% of the MPs, while low-density polymers accounted for 32% at all depths. Overall, our results show that MPs are ubiquitous in the water column from surface to deep waters; we did not find any impact of water density on the depth distribution of MPs despite the strong water stratification in the Kattegat/Skagerrak.

Lagrangian tracking of long-lasting plastic tags: From lobster fisheries in the USA and Canada to Macaronesia

Plastic waste from the fishing industry, particularly lobster trap identification tags from the USA and Canada, poses a significant threat to marine ecosystems due to its resilience. This study unveils a novel link between North American fisheries and the appearance of these plastic tags in Macaronesia. Collected in the Azores and Canary Islands, these tags offer a unique insight into the sources and spatio-temporal scales of marine plastic pollution. Ocean model data indicates the Labrador Current and Gulf Stream as key forces transporting these tags. Virtual particle simulations show a small fraction reaching Macaronesia (4.12 % in the Azores, 0.76 % in the Canary Islands), suggesting real ocean drift. The Azores, with more collected tags, are more susceptible, and tags can reach Macaronesia in under a year. These findings underscore the urgency of better waste management and emphasize the role of citizen science in monitoring and combating marine pollution.