Ana Montoya-Melgoza

This study examined the ingestion of microplastics (MPs) by copepods in the Bay of La Paz, the largest and deepest coastal environment in the Gulf of California (GC), Mexico. The research was based on zooplankton samples collected during oceanographic cruises from 2003 to 2016 at a location near the urban area of La Paz city. In the laboratory, adult copepods were selected from the samples, and a dilution process was used to extract the MPs from their bodies. Were extracted 428 MPs, consisting of fibers, films, fragments, and pellets (microspheres). No evidence was found to suggest that the ingestion of MPs has increased over time. The year 2009 recorded the highest number of MPs, with 120 items, which may be attributed to the circulation pattern during that period, which was influenced by an old, decaying cyclonic eddy. In contrast, 2014 had the fewest MPs, with only 44 items. Throughout the study, transparent fibers were the most conspicuous material. Research on the ingestion of MPs by copepods in Mexico is still in its early stages. According to the available literature, this study represents the first documented report on this subject in coastal waterbodies within the GC.

This study evaluated the ingestion of microplastics (MP) by copepods in Terminos Lagoon (TL), a RAMSAR-listed site in the southern Gulf of Mexico. The evaluation was carried out in two contrasting seasons of 2022, as follows: the dry (April) and the rainy (October). Copepods were collected using a conical plankton net (mesh size of 200 μm). In the laboratory, a pool of all pelagic adult copepod taxa was picked, and the MP inside the organisms were extracted, classified, and photographed using traditional optical and scanning electron microscopy. A total of 268 MP particles were extracted from the interior of copepods; among them, 149 and 119 corresponded to the dry and rainy seasons, respectively. The ingestion rate in the dry season was 0.14, while in the rainy season, it was 0.11. In addition, fibers, plastic fragments, and microspheres with different colors (blue, red, black, green, transparent, and multicolored), sizes, forms (angular, round, triangular, and twisted), and textures were also detected. Fibers were the most abundant MP found in a proportion of more than 85%. In addition, in some sampling sites, microspheres were observed with high relative abundance values (80%). In some sites, fragments reach 20% of the total abundance. Significant differences were observed between the two seasons. The sites closest to the urban area adjacent to TL observed high diversity and abundance of MP. The higher abundance of MP in the dry season is due to lower river discharge, on the other hand. Thus, MP particles accumulate and become available for consumption by copepods. This is the first study that has revealed that the MP was ingested by the copepods in TL. Furthermore, this study provides a baseline information for future research on the abundance of MP in the Gulf of Mexico region.