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Spatial patterns of microplastic contamination, Batophora occidentalis invasion, and physiological responses of Holothuria tubulosa from a Mediterranean coastal lagoon.
Summary
Researchers found microplastics, tiny plastic fragments, mostly from common plastics like polyethylene, throughout a protected Mediterranean lagoon, including inside sea cucumbers living there. The animals showed signs of stress but were able to activate their own antioxidant defenses to cope, at least for now, suggesting these creatures could serve as an early-warning system for pollution. While this study focused on marine life rather than people, it's a reminder that the same persistent plastics accumulating in seafood-producing waters are part of the same pollution making its way into the food we eat.
Microplastic (MP) pollution and biological invasions are major stressors in coastal marine ecosystems, yet the ecological and physiological responses associated with their co-occurrence remain poorly understood. This study assessed the potential relationship between MP contamination, the presence of the invasive macroalga Batophora occidentalis, and the physiological state of the sea cucumber Holothuria tubulosa in S'Estany des Peix lagoon (Formentera, western Mediterranean). MPs were measured in sediment, water, and tissues (intestines and gills), while oxidative stress and detoxification biomarkers (CAT, SOD, GSH, GSSG, GST), along with MDA (lipid peroxidation indicator) and PCC (protein oxidation indicator), were analysed across three zones (internal, middle, and external) with different invasion levels. MPs were detected in all compartments, predominantly as blue fibres, with the highest abundances recorded in the middle zone with 36 items·L in water and 0.89 items·g in sediment. In H. tubulosa, 124 MPs were recovered (64% in intestines; 36% in gills). Polymer composition was analysed by μ-ATR-FTIR on a representative subset, revealing dominance of high-density polyethylene (HDPE), followed by polypropylene (PP) and low-density polyethylene (LDPE) across all matrices, indicating common anthropogenic sources and high persistence. Organisms from the internal and middle zones, where higher MP abundances and B. occidentalis cover were recorded, exhibited elevated antioxidant and detoxification enzyme activities, whereas lipid peroxidation and protein oxidation remained stable, suggesting compensatory biochemical responses. These findings demonstrate widespread microplastic contamination in S'Estany des Peix and reveal spatial variation in physiological responses in H. tubulosa in a context of multiple co-occurring environmental stressors. The study supports the use of this species as a sentinel organism for assessing ecological disturbance in vulnerable Mediterranean coastal lagoons and provides baseline information on MP contamination and biomarker responses in a protected Mediterranean lagoon ecosystem.