Eurasian Dipper Eggs Indicate Elevated Organohalogenated Contaminants in Urban Rivers

Many urban European streams are recovering from industrial, mining, and sewage pollution during the 20th century. However, associated recolonization by clean water organisms can potentially result in exposure to legacy or novel toxic pollutants that persist in the environment. Between 2008 and 2010, we sampled eggs of a river passerine, the Eurasian dipper (<i>Cinclus cinclus</i>), from 33 rivers in South Wales and the English borders (UK) which varied in catchment land use from rural to highly urbanized. Dipper egg δ¹⁵N and δ¹³C stable isotopes were enriched from urban rivers while δ³⁴S was strongly depleted, effectively discriminating their urban or rural origins at thresholds of 10% urban land cover or 1000 people/km². Concentrations of total polychlorinated biphenyls (PCBs) and polybrominated biphenyl ethers (PBDEs) were positively related to urban land cover and human population density while legacy organochlorine pesticides such as <i>p,p</i>′-DDE, lindane, and hexachlorobenzene were found in higher concentrations at rural sites. Levels of PBDEs in urban dipper eggs (range of 136–9299 ng/g lw) were among the highest ever reported in passerines, and some egg contaminants were at or approaching levels sufficient for adverse effects on avian development. With the exception of dieldrin, our data shows PCBs and other organochlorine pesticides have remained stable or increased in the past 20 years in dipper eggs, despite discontinued use

ANOVA summary table of main and interactive effects of CO₂ treatment (CO₂) and conditioning type (CT) on litter chemistry.

<p><i>P</i> values <0.05 are emboldened.</p

Effects of CO₂ treatment on feeding responses of each invertebrate species.

<p>The mean litter consumption (±1 SE) of each invertebrate species is shown for (A) alder and (B) birch in the choice test, and (C) alder and (D) birch in the no-choice test. Asterisks indicate significant differences between CO₂ treatments within each invertebrate species (***<i>P</i><0.001). Species are arranged by habitat of origin: aquatic species are <i>Asellus aquaticus</i> (Aa), <i>Gammarus pulex</i> (Gp), <i>Odontocerum albicorne</i> (Oa) and <i>Sericostoma personatum</i> (Sp); terrestrial species are <i>Blaniulus guttulatus</i> (Bg), <i>Oniscus asellus</i> (On), <i>Porcellio scaber</i> (Ps) and <i>Tachypodoiulus niger</i> (Tn).</p

Overview of the experimental approach.

<p>Litter was produced under ambient- and elevated-CO₂ atmospheres at BangorFACE, UK. Half of the litter from each CO₂ treatment was conditioned aquatically and half terrestrially. Chemical analyses of the conditioned litter were undertaken, and litter discs were presented to aquatic and terrestrial invertebrates in choice and no-choice tests. Only one tree and one invertebrate species have been shown for clarity. Not to scale.</p

Chemical composition of leaf litter (mean ±1 SEM).

<p>Abbreviations: percent dry mass (% DM), percent acetyl-bromide-soluble lignin (% ABSL), conditioning type (CT).</p><p>Different lowercase letters indicate significant differences (<i>P</i><0.05) between CO₂ treatments for each tree species × CT combination.</p

Detritivorous macroinvertebrate species used in the study.

<p>Detritivorous macroinvertebrate species used in the study.</p