Seabird colonies as relevant sources of pollutants in Antarctic ecosystems: Part 1 - Trace elements

Abstract

Global distillation is classically pointed as the biggest responsible for contaminant inputs in Polar ecosystems. Mercury (Hg) and other trace elements (TEs) also present natural sources, whereas the biologically mediated input is typically ignored. However, bioaccumulation and biomagnification combined with the fact that seabirds gather in large numbers into large colonies and excrete on land might represent an important local TEs input. A previous work suggested these colonies as sources of not only nutrients, but also organic contaminants. To evaluate a similar hypothesis for TEs, samples of lichen (n = 55), mosses (n = 58) and soil (n = 37) were collected in 13 locations within the South Shetlands Archipelago during the austral summers of 2013-14 and 2014-15. They were divided in: "colony" (within the colony itself for soil and bordering it for vegetation) and "control" (at least 50 m away from colony interference), analysed for TEs (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) and stable isotopes (C and N). In most cases, soil seems the best matrix to assess colonies as TEs sources, as it presented more differences between control/colony sites than vegetation. Colonies are clearly local sources of organic matter, Cd, Hg and likely of As, Se and Zn. Conversely, Co, Cr, Ni and Pb come presumably from other sources, natural or anthropogenic. In general, isotopes were more useful for interpreting vegetation data due to fractionation of absorbed animal-derived organic matter. Other local Hg sources could be inferred from high levels in control sites, location and wind patterns.

Do population parameters influence the role of seabird colonies as secondary pollutants source? A case study for Antarctic ecosystems

“…Some studies (e.g. Roosens et al 2007;Choy et al 2010), including recent ones by the authors of the present work (Cipro et al 2018a(Cipro et al , 2019, confirmed the role of seabird colonies in Antarctic ecosystems as relevant secondary sources of POPs and TEs as well.…”

“…A subset of the samples is taken from previous works of the authors (Cipro et al 2018a(Cipro et al , 2019, i.e., the samples from the austral summers of 2013-14 and 2014-15. To those, a new subset has been added, with samples collected in 2017-18 (n=3 for algae, 22 for lichen, 21 for moss, 10 for soil), always in locations comprised within the previous dataset.…”

“…Samples for TEs and SIA of C and N were collected according to Cipro et al (2018a). Briefly, samples were collected with plastic gear (spoons and tweezers) firstly rinsed in an acid bath (35mL L -1 nitric acid, 50 mL L -1 hydrochloric acid), then further rinsed with Milli-Q water.…”

“…These inputs are classically attributed to a phenomenon labelled "Global distillation", briefly: volatile contaminants evaporate in warmer regions, undergo long-range transport and condensate in colder regions. In a lesser scale, TEs have natural sources as well (Mão de Ferro et al 2013;Cipro et al 2018a). Conversely, the input due to the movement of organisms, i.e., biologically mediated, is typically insufficiently considered or even ignored (Blais et al 2007).…”

“…Moreover, some material within the colony other than the excretion itself, such as eggs (Brasso et al 2012), carcasses and prey (Emslie et al 2014) also contribute to this input. The use of stable isotope analyses (SIA), in turn, was proven able to provide a deeper insight on the origin of both organic matter and pollutants in previous studies of the authors (Cipro et al 2011(Cipro et al , 2018a(Cipro et al , 2019, particularly due to fractionation steps during the decay of animal derived organic matter (Heaton 1986) and the relative volatility of the decay products and the pollutants themselves (Cipro et al 2011).…”