Penguins as bioindicators of mercury contamination in the southern Indian Ocean: geographical and temporal trends

Abstract

Penguins have been recently identified as useful bioindicators of mercury (Hg) transfer to food webs in the Southern Ocean over different spatial and temporal scales. Here, feather Hg concentrations were measured in adults and chicks of all the seven penguin species breeding in the southern Indian Ocean, over a large latitudinal gradient spanning Antarctic, subantarctic and subtropical sites. Hg was also measured in feathers of museum specimens of penguins collected at the same sites in the 1950s and 1970s. Our aim was to evaluate geographical and historical variations in Hg transfer to penguins, while accounting for feeding habits by using the stable isotope technique (δ(13)C, habitat; δ(15)N, diet/trophic level). Adult feather Hg concentrations in contemporary individuals ranged from 0.7 ± 0.2 to 5.9 ± 1.9 μg g(-1) dw in Adélie and gentoo penguins, respectively. Inter-specific differences in Hg accumulation were strong among both adults and chicks, and mainly linked to feeding habits. Overall, penguin species that feed in Antarctic waters had lower feather Hg concentrations than those that feed in subantarctic and subtropical waters, irrespective of age class and dietary group, suggesting different Hg incorporation into food webs depending on the water mass. While accounting for feeding habits, we detected different temporal variations in feather Hg concentrations depending on species. Notably, the subantarctic gentoo and macaroni penguins had higher Hg burdens in the contemporary rather than in the historical sample, despite similar or lower trophic levels, respectively. Whereas increases in Hg deposition have been recently documented in the Southern Hemisphere, future monitoring is highly needed to confirm or not this temporal trend in penguins, especially in the context of actual changing Hg emission patterns and global warming.

Mercury exposure and short-term consequences on physiology and reproduction in Antarctic petrels

“…In addition, longitudinal investigations on temporal changes in Hg concentrations in wild seabirds' tissues are still dramatically lacking. On the other hand, blood Hg concentrations were not significantly related to the year of sampling, highlighting low inter-annual variability in exposure over the short-term, as usually observed at oceanic sites far from Hg point sources (Brasso et al, 2014;Carravieri et al, 2016).…”

“…Upper predators such as seabirds can thus be exposed to large quantities of Hg via food intake (Bargagli et al, 1998). Consequently, seabirds are increasingly used as bioindicators of Hg distribution in the marine environment, including the polar regions (Carravieri et al, 2016;Fort et al, 2014;Polito et al, 2016), and are susceptible to Hg toxicity both at the individual and population levels (Goutte et al, 2014a,b;Tartu et al, 2013Tartu et al, , 2016. In contrast to the Arctic, where spatio-temporal trends and negative effects of seabird exposure to Hg are relatively wellknown (e.g., Bond et al, 2015;Braune et al, 2014a;Dietz et al, 2013;Fort et al, 2016Fort et al, , 2014Goutte et al, 2015;Scheuhammer et al, 2015;Tartu et al, 2013), Hg occurrence and toxicity in Antarctic species are poorly studied.…”

“…In contrast to the Arctic, where spatio-temporal trends and negative effects of seabird exposure to Hg are relatively wellknown (e.g., Bond et al, 2015;Braune et al, 2014a;Dietz et al, 2013;Fort et al, 2016Fort et al, , 2014Goutte et al, 2015;Scheuhammer et al, 2015;Tartu et al, 2013), Hg occurrence and toxicity in Antarctic species are poorly studied. Hg exposure has mainly been assessed in penguins in a variety of tissues (Brasso et al, 2015;Carravieri et al, 2016) especially in West Antarctica (e.g., Ancora et al, 2002;Brasso et al, 2012;dos Santos et al, 2006;Jerez et al, 2011). By contrast, Antarctic flying seabirds have received much less attention (Tartu et al, 2014(Tartu et al, , 2015; most studies have reported Hg concentrations in eggs or tissues within a limited number of individuals, revealing similar levels to Arctic species, despite lower Hg concentrations in abiotic matrices (Bargagli et al, 1998;Calle et al, 2015;Cipro et al, 2017a;Nygård et al, 2001).…”

Long‐term dietary shift and population decline of a pelagic seabird—A health check on the tropical Atlantic?

“…In addition, the increase in atmospheric CO 2 , and thus aqueous CO 2 , has increased phytoplankton fractionation, reducing its δ 13 C values (Rau, Takahashi, Des Marais, Repeta, & Martin, ). Thus, raw δ 13 C values of sooty tern feathers were adjusted following Hilton et al (), Jaeger and Cherel (), and Carravieri, Cherel, Jaeger, Churlaud, and Bustamante ().…”

Seasonal variation and annual trends of metals and metalloids in the blood of the Little Penguin (Eudyptula minor)

“…Yet another possibility is the global trend of increasing oceanic Hg, but this applies to a lesser degree to the Southern hemisphere (Lamborg et al, 2014). Only two of seven penguin species in the southern Indian Ocean exhibited an increasing Hg pattern in their feathers (Carravieri et al, 2016) and it is certainly questionable why St Kilda penguins would reflect this global trend when penguins from Phillip Island did not.…”