The influence of breeding colony and sex on mercury, selenium and lead levels and carbon and nitrogen stable isotope signatures in summer and winter feathers of Calonectris shearwaters

Abstract

Contamination in marine foodwebs is nowadays of great environmental concern owing to the increasing levels of pollution in marine ecosystems from different anthropogenic sources. Seabirds can be used as indicators of regional contaminant patterns across large temporal and spatial scales. We analysed Hg, Se and Pb levels as well as stable isotope ratios of C ( grown during breeding also showed sexual differences in Hg concentrations and d 13 C. Differences in Hg concentration between sexes are mainly due to egg-laying decontamination in females. In contrast, differences in Hg among colonies are probably related to differences in trophic ecology, as indicated by d 13 C and d 15N measurements. Contaminant concentrations in winter-grown feathers did not show any relationship with stable isotope values but were affected by contaminant loads associated with the breeding season. These findings suggest that the interpretation of contaminant levels of migratory species from feathers moulted out of the breeding season should be made with caution because those values could reflect exposures to contaminants acquired during the breeding season. We conclude that factors other than feeding ecology may play an important role in the interpretation of contaminant levels and their annual dynamics at several spatial scales. Consideration of the relevant temporal context provided by isotopic signatures and contaminant concentrations is important in deciphering contaminant information based on various tissues.

Trophodynamics of inorganic pollutants in a wide-range feeder: The relevance of dietary inputs and biomagnification in the Yellow-legged gull (Larus michahellis)

“…Within this framework, monitoring animal exposure to pollutants derived from local foodwebs is crucial to evaluate the actual impact of such pollution on wildlife communities and on the ecosystem as a whole. In this regard and as many previous studies had found, THg, Se and Pb levels in fledgling feathers varied geographically confirming that baseline levels of these elements at different colony sites easily influence tissue burdens, especially at high trophic levels (Bearhop et al, 2000;Gochfeld, 1997;Ramos et al, 2009a;Ricca et al, 2008;Thompson et al, 1992). However, more importantly, this study concluded that exploited feeding habitats may affect pollutant burden of a given individual, in a greater manner than its own trophic position does.…”

“…In addition, many other studies have already reported on biomagnification of these elements throughout foodwebs, considering d 15 N as a measure of trophic positions (Atwell et al, 1998;Becker et al, 2002;Cabana and Rasmussen, 1994;Jarman et al, 1996;McIntyre and Beauchamp, 2007;Morel et al, 1998). Some of these studies even found this positive pollutante d 15 N relationship at intra-specific level (Ramos et al, 2009a).…”

“…In this regard and in addition to intrinsic factors, such as detoxification capability, age, sex, body size, genetics, reproductive status and nutritional condition, those factors related with diet and trophic aspects are proved to be the most relevant in affecting pollutant burdens of the individuals (Becker et al, 2002;McIntyre and Beauchamp, 2007;Verreault et al, 2009). In particular, several studies have previously reported on the influence of particular dietary contributions on THg and Se concentrations (Bergeron et al, 2007;Loseto et al, 2008;Ramos et al, 2009a). In addition, many other studies have already reported on biomagnification of these elements throughout foodwebs, considering d 15 N as a measure of trophic positions (Atwell et al, 1998;Becker et al, 2002;Cabana and Rasmussen, 1994;Jarman et al, 1996;McIntyre and Beauchamp, 2007;Morel et al, 1998).…”

“…However, direct trophic transfer of pollutants derived from local feeding opportunities and individual feeding behaviours is also considered an important pathway for contaminant acquisition (Bearhop et al, 2000;Bergeron et al, 2007;Loseto et al, 2008;Ramos et al, 2009a), adding complexity to the study of pollutant trophodynamics. Thus, although it is generally accepted that both individual trophic level and differential exploitation of particular trophic chains condition the pollutant exposure of species, most of previous contaminant studies partially neglected some of these effects due to the difficulty in distinguishing and accurately quantifying them (e.g.…”

Trace me if you can: the use of intrinsic biogeochemical markers in marine top predators

“…Each tracer integrates into tissues in a different manner and over different time periods (Figure 3). For instance, while stable-isotope signatures and fatty acids are promptly transferred from the diet to the tissues, trace elements and some pollutants are intentionally mobilized to various tissues and organs with accumulation or excretion purposes, showing a slower and more complex response to changes in diet or habitat (Ramos et al 2009b;Bond 2010). Therefore, when designing any ecological study based on biogeochemical tracers, the selection of the target tracers and tissues becomes a key issue.…”