Early-life exposure to plastics is associated with health parameters and biomarkers in southern giant petrels

Abstract

The sub-lethal effects of plastics and their associated chemicals on wildlife are poorly understood, primarily due to the lack of reliable indicators. We used southern giant petrels ( Macronectes giganteus, SGP), key scavengers and predators in southern seas, to assess whether early-life exposure to plastics was associated with health parameters. We examined relationships between plastic ingestion (≥ 1 mm) and biomarkers of enzymatic activities (AChE acetylcholinesterase, BChE butyrylcholinesterase and GST glutathione S-transferase) and conventional health parameters (haematological, biochemical and morphometric data) in SGP chicks from colonies in Chubut, Argentina. During 2022 and 2023, plastics were detected in 71.4% of chicks (1–14 items, mean mass = 0.2510 g, representing < 0.1% of chick body mass). In 30-day-old chicks, plastic ingestion was associated with nutritional parameters (cholesterol, total solids, packed cell volume, calcium, body mass and body condition index), metabolism (enzymes aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, creatinine phosphokinase) and immune response (eosinophil percentage). Associations with biomarkers (AChE, BChE, and GST) were observed but lost significance when accounting for inter-annual variation. By fledging (∼90 days), most relationships weakened or disappeared, while GST activity and calcium levels emerged as the only variables associated with plastic ingestion. It is unclear whether these associations reflect compensatory physiological responses to oxidative challenge, contaminant exposure, or developmental/ontogenetic adjustments. Our results highlight the value of multi-indicator approaches for detecting subtle physiological variation associated with plastic ingestion. Importantly, the pervasive threat of plastic pollution warrants investigating whether early-life exposure influences post-fledging survival and fitness.