Feather mercury levels in seabirds at South Georgia: influence of trophic position, sex and age

Abstract

We studied the mercury contamination of 13 species of seabirds breeding on Bird Island, South Georgia, in 1998. Total mercury concentrations in body feather samples of birds caught at their breeding colonies were determined. Among the species, grey-headed albatross (8933 ng g ) the lowest body feather mercury concentrations. Mercury levels were negatively correlated with the proportion of crustaceans (mainly krill) in the species' diets, suggesting that the trophic level is the most important factor in explaining the variation of mercury concentrations in Antarctic seabirds. In 4 species studied for age effects among adult birds (grey-headed and black-browed albatross, northern and southern giant petrel), no age-dependent variation in mercury levels was found. Sex differences were also assessed: female gentoo penguins had lower mercury levels than males, which may be related to the elimination of part of the mercury body burden by females into eggs. In contrast, northern giant petrel males had lower levels than females, which may be related to a higher consumption by males of carrion from Antarctic fur seals. In grey-headed albatrosses, mercury levels were 113% higher than in 1989, when this species was investigated at the same site, indicating a possible increase in mercury pollution of the Southern Ocean during the last decade.

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

“…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). Some of these studies even found this positive pollutante d 15 N relationship at intra-specific level (Ramos et al, 2009a).…”

“…In previous papers, several authors have speculated on the causes underlying the high intra-specific variation in contaminant concentrations in many marine top predators (McIntyre and Beauchamp, 2007;Muir et al, 2003;Takahashi et al, 2000;Verreault et al, 2009;Wan et al, 2007). 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).…”

“…However, there is a marked variability in these factors affecting the dynamics of contaminants throughout foodweb (i.e. pollutant trophodynamics), which may potentially lead these apical species to a different pollutant exposure; and this knowledge becomes critical for effective environmental health monitoring and pollutant body burden assessments (Becker et al, 2002;McIntyre and Beauchamp, 2007;Verreault et al, 2009).…”

“…Since Cabana and Rasmussen (1994) questions related to biomagnification of contaminants to deleterious levels in biota, have largely been addressed by considering species' trophic positions (Becker et al, 2002;McIntyre and Beauchamp, 2007;Morel et al, 1998;Stewart et al, 2004). 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.…”

Influence of trophic position and foraging range on mercury levels within a seabird community

“…mesopelagic fish) accessed through fisheries discards may be more important than trophic level per se (Thompson et al 1998a, Monteiro et al 1999, Arcos et al 2002. To date, most studies have either focused on a single or a small number of species (but see Atwell et al 1998, Becker et al 2002, or have examined mercury burdens in a wide variety of species, but were unable to compare diet and Hg burden directly, since diets were assessed during the breeding season and the tissues collected (feathers) reflect the nonbreeding season (e.g. Stewart et al 1999, Becker et al 2002.…”