Amenábar María, Aguilera Moisés A, Gallardo Camila, Moore Charles, De Vine Raquelle, Lattin Gwen, Gamba Angela, Luna-Acosta Andrea, Thiel Martin
Facultad Ciencias del Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, 1781421, Chile.
Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ibáñez, Diagonal Las Torres, 2640, Peñalolén, Santiago, Chile.
Environ Pollut. 2024 Feb 15;343:123157. doi: 10.1016/j.envpol.2023.123157. Epub 2023 Dec 22.
In coastal waters, higher concentrations of microplastics (MPs) are generally related to densely populated and industrialized areas, but intense upwelling and offshore transport in the Eastern Boundary Upwelling Systems (EBUS) may influence this pattern. The Humboldt Current System (HCS) along the coast of northern-central Chile represents a perfect model to test whether the abundance of MP at the sea surface decreases with distance from land-based sources, e.g., river mouths, harbors, and submarine wastewater outfalls. The sea surface was sampled with a manta trawl to examine the abundance, composition, and distribution of floating MPs, and Generalized Additive Mixed Models (GAMMs) were performed to examine the relationship between MP abundance (particles km) and the distance to putative sources. MPs were found in all 57 net tows, with an average of ⁓120,000 MP km and maximum values of ⁓1,500,000 MP km. The composition of MPs was dominated by fragments (>50% of the total count) and over 80% of all MPs were ≥1 mm. The combined effect of the various sources, spatially concentrated in urban areas, makes it difficult to distinguish their relative contributions, but the MP composition suggested that rivers are more important sources, followed by submarine wastewater outfalls and then harbors. A significant and steep negative relationship with the "distance to source" explained 15.2% of the variance of "MP abundance", suggesting rapid offshore displacement within the HCS. This is the first study to report this pattern along the edges of the South Pacific Subtropical Gyre (SPSG), revealing that continuous offshore transport of microplastic from land-based sources is occurring over large scales and contributing to the accumulation of microplastics in the center of the SPSG. However, the findings additionally suggested that processes at meso- and submeso-spatial scales (driven by geographic and seasonal variables) are disrupting the general pattern.
在沿海水域，微塑料（MPs）的较高浓度通常与人口密集和工业化地区有关，但东部边界上升流系统（EBUS）中的强烈上升流和离岸运输可能会影响这种模式。智利中北部沿海的洪堡海流系统（HCS）是一个完美的模型，可用于测试海面微塑料的丰度是否会随着与陆源（如河口、港口和海底废水排放口）距离的增加而降低。使用蝠鲼拖网对海面进行采样，以检查漂浮微塑料的丰度、组成和分布，并采用广义相加混合模型（GAMMs）来研究微塑料丰度（颗粒/千米）与到假定源的距离之间的关系。在所有57次拖网中均发现了微塑料，平均约为120,000个微塑料/千米，最大值约为1,500,000个微塑料/千米。微塑料的组成以碎片为主（占总数的50%以上），所有微塑料中超过80%的尺寸≥1毫米。各种来源在空间上集中在城市地区，其综合影响使得难以区分它们的相对贡献，但微塑料的组成表明河流是更重要的来源，其次是海底废水排放口，然后是港口。与“到源的距离”呈显著且陡峭的负相关关系，解释了“微塑料丰度”方差的15.2%，表明在HCS内微塑料迅速离岸迁移。这是第一项报道南太平洋亚热带环流（SPSG）边缘这种模式的研究，揭示了陆源微塑料在大尺度上持续的离岸运输，并导致微塑料在SPSG中心的积累。然而，研究结果还表明，中尺度和亚中尺度空间尺度上的过程（由地理和季节变量驱动）正在扰乱这种总体模式。
