Sex, age class, and foraging strategy of the Southern Giant Petrel might influence the hazard of plastic ingestion on the Patagonian shelf

Abstract

**Abstract:** Plastic circulates at sea threatening marine megafauna. Southern Giant Petrels (SGP, Macronectes giganteus) are known to consume plastic, but the source and accumulation areas of marine litter remain unknown. The goal of this study is to understand how foraging behavior of SGP will impact their risk of plastic ingestion by mimicking the circulation of floating debris. We tracked 34 adult and juvenile birds using either PTTs or GPS, from Arce (45°00'S; 65°29'W) and Gran Robredo Islands (45°80'S; 66°03'W). To mimic plastic circulation at sea we employed the output of 15 years of daily-forcing simulations using ROMS-Agrif. We designed lagrangian simulations of particles (individual based model) using off-line particle-tracking model. Simulations incorporate physical characteristics of plastic that reaches the area from coastal cities and ships. Dual foraging strategy was recorded for all breeding birds. During short trips (N=108, recorded with GPS), both sexes foraged at 38.5 ± 12.9 km from the colony. During long trips (N= 60), males mainly foraged along the coast at 382 ± 65 km from the colony, while females moved to the shelf break and the middle shelf (459 ± 58 km). Throughout austral fall and winter, adults remained on the Patagonian shelf, but juveniles moved north using the shelf break as a corridor. The drift model showed how simulated particles generated a plastic corridor along the Patagonian shelf until reaching the Malvinas-Brazil confluence, concurring with juveniles' migration path. Accumulation hot spots occurred in the mid shelf and along the shelf break with a strong seasonal variation, overlapping with breeding females. Litter coming from cities and fisheries accumulated near the colony, corresponding with adult foraging areas during short trips, which may explain the 50 to 73% of plastic items found in chicks' diet. Our results showed that marine litter dispersed by ocean circulation, will threat SGP, depending on sex, age class, and breeding stage. Understanding where marine organisms come into contact with plastic, could help elucidate negative effects at population-levels to design management strategies that mitigate this environmental issue. **Authors:** Gabriela Blanco¹, Mariano Tonini², Gallo Luciana¹, Flavio Quintana¹ ¹Instituto de Biologia de Organismos Marinos - CONICET, ²Instituto Andino Patagonico de Tecnologias Biologicas y Geoambientales - CONICET