Food web transfer of plastics to an apex riverine predator.

As a rapidly accelerating expression of global change, plastics now occur extensively in freshwater ecosystems, yet there is barely any evidence of their transfer through food webs. Following previous observations that plastics occur widely in their prey, we used a field study of free-living Eurasian dippers (Cinclus cinclus), to test the hypotheses that (1) plastics are transferred from prey to predators in rivers, (2) plastics contained in prey are transferred by adults to altricial offspring during provisioning and (3) plastic concentrations in faecal and regurgitated pellets from dippers increase with urbanization. Plastic occurred in 50% of regurgitates (n = 74) and 45% of faecal samples (n = 92) collected non-invasively from adult and nestling dippers at 15 sites across South Wales (UK).

Polystyrene microplastics decrease accumulation of essential fatty acids in common freshwater algae.

Despite growing concern about the occurrence of microplastics in aquatic ecosystems there is only rudimentary understanding of the pathways through which any adverse effects might occur. Here, we assess the effects of polystyrene microplastics (PS-MPs; <70 μm) on a common and widespread algal species, Chlorella sorokiniana. We used laboratory exposure to test the hypothesis that the lipids and fatty acids (FAs) are important molecules in the response reactions of algae to this pollutant.

Biological Traits and the Transfer of Persistent Organic Pollutants through River Food Webs.

Freshwater organisms remain at risk from bioaccumulation and biomagnification of persistent organic pollutants (POPs), but factors affecting their transfer through food webs are poorly understood. Here, we investigate transfer pathways of polychlorinated biphenyls, polybrominated diphenyl ethers, and organochlorine through a river food web, assessing the distribution and flux between basal resources ( = 3), macroinvertebrates ( = 22), and fish ( = 1). We investigate the effects of biological traits on the observed patterns and use trait-based models to predict POP bioaccumulation.

Toxicity of proton-metal mixtures in the field: linking stream macroinvertebrate species diversity to chemical speciation and bioavailability.

Understanding metal and proton toxicity under field conditions requires consideration of the complex nature of chemicals in mixtures. Here, we demonstrate a novel method that relates streamwater concentrations of cationic metallic species and protons to a field ecological index of biodiversity. The model WHAM-F(TOX) postulates that cation binding sites of aquatic macroinvertebrates can be represented by the functional groups of natural organic matter (humic acid), as described by the Windermere Humic Aqueous Model (WHAM6), and supporting field evidence is presented.

Local to continental influences on nutrient and contaminant sources to river birds.

Stable isotope and contaminant analyses revealed differences in nutrient sources and contaminant pathways in two species of dipper, Cinclus mexicanus and Cinclus cinclus in western Canada and western Britain. We collected dipper prey and eggs from relatively pristine British Columbian rivers contrasting in the presence of salmon-derived nutrients, and rural Welsh rivers with varying food-web complexity associated with stream acidity. Enriched delta(13)C and to a lesser extent delta(15)N in American dipper eggs and prey confirmed that streams with migrating Pacific salmon were enriched with marine-derived nutrients, but overall contaminant concentrations did not differ strongly in dipper eggs between rivers with and without salmon.

Diet shifts during egg laying: Implications for measuring contaminants in bird eggs.

We combined stable isotope tracers of blood plasma, blood cells and egg contents with faecal analysis during pre-breeding and egg laying phases in two dipper species Cinclus cinclus and Cinclus mexicanus to determine the occurrence of dietary shifts during egg production and to assess consequences for egg contaminant loads. In both species, changes in delta(13)C (C. cinclus) or delta(15)N (C.