Towards understanding the effects of oceanic plastic pollution on population growth for a South American fur seal (Arctocephalus australis australis) colony in Chile

Entanglement of pinnipeds with plastic debris is an emerging conservation and animal welfare issue worldwide. However, the origins and long-term population level consequences of these entanglements are usually unknown. Plastic entanglement could produce a combination of wounds, asphyxiation, or inability to feed that results in the death of a certain percentage of individuals from the total population. In this research, we report on the consequent effect of plastic entanglement on population growth demographics in a South American fur seal (Arctocephalus australis australis) colony on Guafo Island, southern Chile. Using a stochastic matrix population model structured according to age and sex, and assuming an otherwise stable population, we explored population growth rates under five scenarios with differing rates of entanglement: A) a zero rate of plastic entanglement, B) entanglement rates (number of entangled individuals as a proportion of the total number of individuals) as observed in our study population (overall entanglement ratio of 1.2 × 10^-3); and for the other scenarios, entanglement ratios as reported in the literature for other pinniped colonies around the world: C) 3.04 × 10^-3, D) 4.42 × 10^-2, and E) 8.39 × 10^-2. Over the 30 years forecasting period and starting with a population size of ∼2950 individuals, the population growth rate was lower under all scenarios with rates of entanglement greater than zero (scenarios B-E). In comparison with scenario A, at the end of the 30-year period forecasted, we calculated a projected decrease in population size of between 20.34% (scenario B) and 91.38% (scenario E). These results suggest that even the lowest levels of entanglement in pinnipeds as reported in the literature might have significant effects over time on population-level dynamics. Our research offers potential insight when devising policy for the management and limitation of plastic pollution in the oceans, and indeed for the conservation and management policy of affected marine species. Furthermore, whilst there are some limitations to our methodology, it offers a straightforward and potentially useful approach for the standardized prediction of impacts at a population level of different rates of plastic pollution and entanglement and could be applied in distinct populations of the same species around the world.

Variación estacional de aves en el humedal de Trumao, centro-sur de Chile

RESUMEN En este estudio se describe el ensamble de aves del humedal de Trumao y su variación estacional según régimen hidrológico durante primavera 2017 y verano 2018 (no inundado) e inviernos 2017 y 2018 (inundado) y se evalúa el tipo de hábitat. Se registraron 29 especies de aves con una abundancia total de 2,341 individuos. El número total de especies acumuladas observadas para el período inundado y no inundado correspondió a 16 y 22 especies, respectivamente, siendo Chroicocephalus maculipennis (Lichtenstein, 1823) (Gaviota cáhuil) la especie dominante durante el período de estudio. El índice de similitud de Sorensen entre los períodos de inundación y no inundación del humedal fue de 73.2%, mientras que la similitud de Bray-Curtis resultó en un 32.65%. Al compararse el periodo invernal inundado (4 m profundidad) y el periodo estival no inundado (1 m profundidad), el índice de diversidad registró diferencias estadísticamente significativas, en cambio, la abundancia no presentó diferencias significativas. El análisis SIMPER arrojó que entre el periodo invernal inundado y el periodo estival no inundado las especies que mostraron un mayor porcentaje de disimilitud en su abundancia entre estas temporadas fueron la Gaviota cáhuil y Loro choroy [Enicognathus leptorhynchus (King, 1831)]. El uso de hábitat en el humedal de Trumao, por parte de las aves, fue altamente variable, tanto estacional como espacialmente, resultado esperable para este tipo de ecosistemas. Finalmente, nuestros resultados nos indican que las aves ocupan los humedales según fluctuaciones estacionales y según el hábitat que se encuentre disponible, sin embargo, la abundancia no se ve afectada por los cambios hidrológicos. Con estos resultados es fundamental seguir realizando más investigaciones en el humedal para determinar el uso (nidificación, alimentación, reproducción) que realizan las aves en los distintos hábitats para de esta manera generar medidas de protección y conservación para la gestión del humedal de Trumao.

First detection of plastic microfibers in a wild population of South American fur seals (Arctocephalus australis) in the Chilean Northern Patagonia

The dramatic increase of microplastics (plastic fragments <5 mm) in marine environments is a problem that has attracted public attention globally. Within the different types of microplastics, microfibres are the least studied (size <1 mm). We examined 51 female scats from a population in Northern Patagonia. Our results showed no presence of microplastic particles, however 67% of them showed a remarkable abundance of microfibers, which until now had only been reported in animals fed in captivity. As a result of this work we propose that the examination of scats from South American Fur Seal and also other pinnipeds could be an efficient tool to monitor environmental levels of microfibres and maybe microplastics in the environment due to the easy recognition of the animals and their scats.

Coastal debris survey in a Remote Island of the Chilean Northern Patagonia

Global marine litter pollution is increasing dramatically, and oceanic islands are one of the most vulnerable ecosystems due to their high debris accumulation rate compared to continental sites. Remote areas, such as inhabited islands, represent a perfect study case to track marine debris sources, due to the assumed low rates of local production of debris. Guafo Island is one of the largest islands of the Chilean Northern Patagonia and is considered a remote zone. The accessible coast of Guafo Island was monitored during four austral summers revealing higher levels of marine debris accumulation than continental Chile. Plastic was the most abundant type of debris constituting 50% of the total litter monitored. Our results suggest that most of the plastic identified is likely to be related to local fisheries activities. Mitigation measures including collaboration among fishing communities and scientists could contribute to reduce the coastal debris pollution in remote areas.

Kelp and dolphin gulls cause perineal wounds in South American fur seal pups (Arctocephalus australis) at Guafo Island, Chilean Patagonia

During five reproductive seasons, we documented the presence, extent and origin of perineal wounds in South American fur seal pups (Arctocephalus australis) on Guafo Island, Northern Chilean Patagonia. The seasonal prevalence of perineal wounds ranged from 5 to 9%, and new cases were more common at the end of the breeding season (February), when pups were on average two months old and were actively expelling hookworms (Uncinaria sp). Histologically, wounds corresponded to marked ulcerative lymphoplasmacytic and histiocytic dermatitis with granulation tissue and mixed bacterial colonies. In 2015 and 2017, kelp gulls (Larus dominicanus) and dolphin gulls (Leucophaeus scoresbii) were observed picking and wounding the perineal area of marked pups. This behaviour occurred more frequently after the pups' defecation, when sea gulls engaged in consumption of pups' faeces. The affected pups usually had moderate to marked hookworm infections along with bloody diarrhoea and anaemia. Pups with severe wounds (23% of affected animals) had swollen perineal areas and signs of secondary systemic bacterial infection. We propose that seagulls on Guafo Island have learned to consume remains of blood and parasites in the faeces of pups affected by hookworm infection, causing perineal wounds during this process. We conclude that this perineal wounding is an unintentional, occasional negative effect of an otherwise commensal gull-fur seal relationship.