The research, pioneering in its field, reveals that more than half of the specimens of this species, known as the red swimming crab, analyzed on four beaches on the island, contain microplastic particles in their stomachs, mostly textile fibers from domestic wastewater discharges caused by laundry. This raises concerns about the ecological impact and the transfer of polluting particles into marine ecosystems
A study by the Ecophysiology of Marine Organisms (EOMAR) group at the ECOAQUA University Institute, part of the University of Las Palmas de Gran Canaria (ULPGC), has documented for the first time the presence of microplastics in the Cronius ruber crab, better known as the red swimming crab, an invasive species found in the Canary Islands, off the coast of Gran Canaria. This study establishes a clear relationship with proximity to wastewater discharges, especially domestic wastewater. The research reveals that more than half of the crabs studied, collected from four beaches on the island, contained these polluting particles in their stomachs, and that most of them were textile-derived, derived from laundry waste.
The study, titled "Microplastics in Cronius ruber: Links to Wastewater Discharges" and recently published in the scientific journal "Animals," analyzed 63 specimens of these crabs collected from four beaches on the island (Playa de Las Nieves (Agaete), La Laja (Las Palmas de Gran Canaria), El Puertillo (Arucas), and Anfi del Mar (Mogán). The results show that 52% of the specimens had microplastics in their stomachs, with an average length of between 0.5 and 0.7 mm, with an average of between 1.02 and 1.73 particles per individual.
The research, co-authored by Sofía Huelbes, as lead author; May Gómez, director of EOMAR; Ico Martínez and Alicia Herrera, researchers from this group; and Raül Triay-Portella, from the group Biodiversity and Conservation (BIOCON), also from ECOAQUA, and Miguel González-Pleiter, a researcher in the Department of Biology at the Faculty of Science at the Autonomous University of Madrid, point out that the vast majority of this waste, 89%, was fibers, mainly blue and black. Rayon, commonly used in textiles, was the most frequently identified polymer, at 52%, revealing the role of wastewater from laundry processes as a significant source of contamination.
EOMAR researcher Sofía Huelbes Muñoz.
Beaches near unauthorized wastewater discharges, such as Anfi del Mar and El Puertillo, showed the highest levels of contamination, with microplastic particle occurrence frequencies (FOs) of 67% and 58%, respectively. Las Nieves Beach had the lowest level of contamination, with a microplastic particle occurrence frequency of 41%. Meanwhile, at La Laja Beach, a frequency of 50% was detected in the six samples collected.
Figure 2. Images of the sampling locations represented by the purple area (200 m scale) with the nearby wastewater discharge points. The sampling area at each beach is outlined in pink. (A) El Puertillo Beach; (B) Playa de Las Nieves; (C) La Laja Beach; (D) Anfi del Mar Beach.
This is the first study to document microplastic ingestion by Cronius ruber, which "raises concern about its ecological presence and the potential bioaccumulation of contaminants in marine ecosystems," the study states.
The study warns that "further research is essential to understand the long-term consequences of microplastic exposure on invasive species and their potential role in the transfer of contaminants through food webs."
“Microplastic pollution in the ocean is a growing problem that affects the entire ecosystem and, therefore, the species that inhabit it. These polluting particles can be filtered or ingested by organisms, penetrating and negatively affecting individuals. Crustaceans are among the affected populations. This work demonstrates that wastewater discharges, particularly those from laundry, are a significant source of plastic fibers in the marine environment,” highlights Sofía Huelbes, lead author of the study.
Polluting Discharges: A Direct Link
The analysis, performed using alkaline digestion, filtration, and Fourier Transform Infrared Spectroscopy (micro-FTIR), confirmed the plastic composition of most of the particles. In addition to rayon, polymers such as polypropylene, acrylic, nylon, and polyester, all commonly found in clothing, were identified. The study highlights that a single load of clothes can release more than 700,000 synthetic fibers, which end up in the ocean through wastewater treatment systems.
Figure 3. Photos of types and colors of microplastic particles which were found in stomachs of Cronius ruber specimens from Gran Canaria: (a) films (3.5%); (b) fragments (7%); (c) fibers (89.5%); (d) blue fiber; (e) black fiber; (f) red fiber.
Cronius ruber, introduced to the Canary Islands in 2016 and experiencing rapid population expansion, is a generalist predator that feeds on filter-feeding mollusks, fish, and other invertebrates. The researchers warn that microplastic ingestion can occur both directly and through the food chain, which could amplify the transfer of contaminants to other marine organisms.
“The presence of microplastics in an invasive species raises questions about its role in the dispersion of contaminants and the possible cumulative effect on the marine food web,” notes Huelbes.
This pioneering work highlights the need to monitor wastewater discharges and to further study the long-term effects of microplastics on invasive species and on the health of coastal ecosystems. The authors of the study believe that Cronius ruber could become a key bioindicator for monitoring microplastic pollution in the eastern Atlantic Ocean.
ASTRESS Project
The study, which can be consulted in full at the following link: https://www.mdpi.com/2076-2615/15/10/1420, is part of the ASTRESS project (Assessment of anthropogenic multistressors in zooplankton and suprabenthos), whose principal investigator is Alicia Herrera, a member of the EOMAR group and co-author of this research. The project aims to holistically study the effect of various anthropogenic stressors on zooplankton and suprabenthos.
This ECOAQUA project, which began in October 2024 and will run until the end of 2027, is based on the premise that the oceans are currently being affected, particularly by marine litter, chemical spills, and noise pollution.
Some of the effects of these pollutants are well known, such as the effect of noise on the behavior of cetaceans, endocrine disruption resulting from chemical pollution in fish, or the damage caused by the ingestion of microplastics in turtles, fish, and seabirds.
However, the cumulative effects of these pollutants have not yet been studied in zooplankton and suprabenthos, two fundamental groups within marine ecosystems.
These groups are at the base of the food chain, hence their importance in both pelagic and coastal regions. Understanding the impact of global change on these groups is essential to understanding the long-term effects on the oceans.