The human connection: First evidence of microplastics in remote high mountain lakes of Sierra Nevada, Spain

Data availability Data will be made available on request.

Acknowledgements We would like to thank the support of all the citizen volunteers without which this work would not have been possible. We are extremely grateful to the colleagues of the Ecology Department Carmen Pérez, Eloisa Ramos, Jesús Manuel López-Rodríguez and José Antonio Delgado for leading the multidisciplinary research groups. We are indebted to the contribution of Joana Llodrá for lake basins estimations. Dr. Bopaiah Biddanda is acknowledge for his thorough suggestions. We are also grateful to the staff of Sierra Nevada National Park and the Global Change Observatory of Sierra Nevada who have always supported the “74 High Mountain Glacial-Lake Oases” Citizen Science initiative. This research has been funded by a FECYT grant to MVA (FCT- 18-13095), the LifeWatch-ERIC project “Smart EcoMountains” (LifeWatch- 2019-10-832 UGR-01), a FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades project (P20_00105), and by the Ministerio de Ciencia e Innovación project “REMOLADOX” (PID 2020-118872RB-I00). Funding for open access charge: Universidad de Granada / CBUA.

Microplastics have become one of the most serious global threats to animal and human health. While their presence has been documented in all Earth water ecosystems, including remote mountain lakes, the observation that the abundance of microplastics is largely different across nearby lakes has rarely been examined. As part of a citizen science initiative, this study analyzed for the first time the abundance of microplastics in the surface of 35 glacial lakes of Sierra Nevada National Park in Southern Spain with the objective of determining the local factors that control their abundance. First, we described the shape, size, color and nature of microplastics. Second, we tested whether the number of microplastics differed between basins and analyzed environmental and morphometrical features of lakes affecting their abundance. We found that microplastics were common in most lakes, with a maximum abundance of 21.3 particles per liter that akin to some of the most microplastic polluted lakes worldwide. Fragments were the predominant shape (59.7%) followed by fibers (38.8%) and very scarce spheres (1.5%). Microplastics were observed for all size-fractions, but the abundance of particles <45 μm was higher, what advocates for the use of low pore-size filters to prevent underestimation of microplastics. While the mean abundance of microplastics did not differ among basins, their quantity was related to the presence of meadows surrounding the lakes. This result indicates that while atmospheric transport of microsplastics may equally reach all basins, differences in microplastics among nearby-lakes has an anthropic origin caused by mountaineers who find lakes with ample meadows much more attractive to visit relative to barren lakes. The staggering number in these remote lakes, headwaters of rivers that feed drinking reservoirs, is a major concern that warrants further investigation and the strict compliance with waste management laws to reduce the harmful impacts of microplastic contamination.

FECYT grant to MVA (FCT- 18-13095)

LifeWatch-ERIC project “Smart EcoMountains” (LifeWatch- 2019-10-832 UGR-01)

FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades project (P20_00105)

Ministerio de Ciencia e Innovación project “REMOLADOX” (PID 2020-118872RB-I00)

Funding for open access charge: Universidad de Granada / CBUA