Photo Credits: Odei Garcia-Garin and Núria Viladrich
Scientific Frontline: Extended "At a Glance" Summary: Microplastic Impact on Mediterranean Octocoral Metabolism
The Core Concept: Prolonged exposure to microplastics alters vital physiological processes—most notably respiration and cellular metabolism—in Mediterranean gorgonians (octocorals) without causing immediate visible damage to their tissues.
Key Distinction/Mechanism: Unlike pollutants that cause direct structural deterioration, microplastics induce a sublethal effect in gorgonians. While these organisms can ingest and effectively eliminate plastic particles (such as PET, polystyrene, and polypropylene) while maintaining standard feeding behaviors, their respiration rates drop significantly. This reduction in metabolic activity serves as a physiological response to stress or a strategy for energy conservation.
Major Frameworks/Components:
- Species Analysis: Focused on two representative Mediterranean gorgonian species: the white gorgonian (Eunicella singularis) and the violescent sea-whip (Paramuricea clavata).
- Simulated Exposure: Replicated actual Mediterranean concentrations of prevalent marine microplastics (PET, PS, and PP) over a three-month period.
- Physiological Indicators: Assessed metrics including oxygen uptake (respiration), prey-capture ability, organic matter content, microplastic ingestion rates, and histological tissue conditions.
Branch of Science: Marine Biology, Ecotoxicology, Benthic Ecology.
Future Application: The methodologies and findings from this research will be utilized to model the long-term resilience of marine benthic ecosystems. They provide a critical baseline for developing targeted ecological impact assessments, marine conservation policies, and predictive models regarding the health of coralligenous animal forests under combined environmental stressors (e.g., plastic pollution and ocean warming).
Why It Matters: Gorgonians act as "ecosystem engineers" in the Mediterranean, forming complex three-dimensional structures on rocky seabeds that provide essential habitat and shelter for countless fish and invertebrate species. If microplastic exposure compromises the energetic yield and resilience of these foundational organisms, it could trigger cascading structural failures across the broader marine biodiversity network.
These are some of the findings, set out in an article published in Marine Pollution Bulletin, from a study led by experts Odei Garcia-Garin from the Faculty of Biodiversity Research Institute (IRBio) at the University of Barcelona, and the Institute of Aquatic Ecology at the University of Girona (IEA-UdG), and Núria Viladrich, also a member of the Faculty of Biology and IRBio. The study, funded by IRBio grant PR-2023, also involved collaboration with the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBIBE) at Universitat de València.
The study analyses, for the first time, the effects of prolonged exposure to microplastics on two representative Mediterranean gorgonian species: the white gorgonian (Eunicella singularis) and the violescent sea-whip (Paramuricea clavata).
Gorgonians are colonial organisms that play a vital role in Mediterranean benthic ecosystems and in the conservation of marine biodiversity. They form three-dimensional structures on rocky seabeds — known as coralligenous animal forests — providing shelter and habitat for many species of fish and invertebrates.
“Any disruption to its physiology could have consequences for many other associated species,” explains expert Odei Garcia-Garin, lead author of the study and a member of the Department of Evolutionary Biology, Ecology and Environmental Sciences at the UB and the IEA-UdG.
“Understanding how habitat-forming species respond to plastic pollution will be essential for assessing the ecological impact of microplastics on a global scale.”, Odei Garcia-Garin says.
Microplastics disrupt gorgonian respiration
Microplastic pollution — particles smaller than five millimeters — is a global problem affecting virtually all marine ecosystems. These particles originate from the breakdown of plastic waste or from microbeads used in industrial and consumer products, and can remain in the marine environment for decades, during which they are ingested by numerous organisms. The long-term effects of this pollution are that living organisms that form seabed habitats remain uncertain.
To assess the effects of microplastics, colonies of E. singularis and P. clavata were exposed for three months to a mixture of the most common plastic particles found in the ocean, such as polyethylene terephthalate (PET), polystyrene (PS) and polypropylene (PP). The experiments carried out using equipment at the UB’s Faculty of Biology simulated the actual concentrations of microplastics in the Mediterranean.
The team analyzed various physiological indicators in the gorgonians, such as respiration, prey-capture ability, organic matter content, microplastic ingestion, and the condition of biological tissues. The results reveal that prolonged exposure to these pollutants does not cause visible damage to tissues, “but it does alter some key physiological processes such as respiration, that is, the uptake of oxygen from the external environment for cellular metabolism,” says researcher Núria Viladrich (UB-IRBio).
“Respiration rates fell significantly in both species of gorgonian, which suggests a reduction in metabolic activity. This physiological response could indicate an adaptation to stress or energy-saving strategies,” notes Viladrich.
Effects of microplastic ingestion on gorgonians
Gorgonian colonies also ingested microplastics, with PET particles being the most prevalent. “Their ability to capture food and their organic matter content remained stable, suggesting that the colonies were able to balance the energy cost by maintaining their feeding behavior. Differences were also observed between species in the number of particles ingested and the size of those retained,” reveals Garcia-Garin and Viladrich.
Microscopic analysis of the tissues “revealed no structural damage or histological changes in the colonies studied due to microplastic ingestion,” they continue. “This suggests that gorgonians can eliminate ingested particles relatively effectively, preventing the long-term accumulation of pollutants in their tissues.”
However, the changes observed in metabolism indicate that prolonged exposure to microplastics may lead to sublethal effects, potentially reducing the energy yield of gorgonians over time.
“Further studies will be needed to assess whether these energy costs could compromise the resilience and ecological role of Mediterranean gorgonians in future climate scenarios,” the authors conclude.
Reference material: What Is: Microplastics
Funding: IRBio grant PR-2023, also involved collaboration with the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBIBE) at Universitat de València.
Published in journal: Marine Pollution Bulletin
Authors: Odei Garcia-Garin, Mercè Villar, Iris Cherta, Alessandra Cani, Jazel Ouled-Cheikh, Marc Ruiz-Sagalés, and Núria Viladrich
Source/Credit: University of Barcelona
Reference Number: mb032326_01
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