Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor (Vultur gryphus) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown fromca1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest siteca650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet.

This study compared the ability of the lichen Evernia prunastri, chitin and chitosan to take up Cu²⁺ and Zn²⁺. It was hypothesized that chitin and chitosan have an accumulation capacity comparable to the lichen, so that these biopolymers could replace the use of E. prunastri for effective biomonitoring of Cu and Zn air pollution. Samples of the lichen E. prunastri, as well as chitin (from shrimps) and chitosan (from crabs), were incubated with Cu and Zn solutions at concentrations of 0 (control), 10, 25, 50, 75, and 100 µM and analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Metal concentrations accumulated by lichen, chitin and chitosan samples were strongly and linearly correlated with the concentrations in the treatment solutions. The lichen always showed significantly higher accumulation values compared to chitin and chitosan, which showed similar accumulation features. The outcomes of this study confirmed the great effectiveness of the lichen Evernia prunastri for environmental biomonitoring and showed that chitin and chitosan have a lower accumulation capacity, thus suggesting that although these biopolymers have the potential for replacing E. prunastri in polluted areas, their suitability may be limited in areas with intermediate or low pollution levels.

We analyzed biomarkers, including sterols, stanols, and δ ¹⁵ N, in sediment cores from lakes with well‐documented sockeye salmon return histories. Our goal was to improve estimates of past changes in salmon escapement, that is, the population that return to their freshwater nursery lakes, inferred using sediment biogeochemical markers. Cholesterol, the predominant sterol in adult sockeye salmon muscle tissue, displayed a strong positive relationship with escapement ( R ² = 0.8, p = 0.001, and F _1,8 = 28.3). Sediment concentrations of the plant‐derived sitosterol and algal‐derived fucosterol, absent in salmon muscle tissue also related positively with salmon escapement, suggesting that salmon‐derived nutrients from decomposing fish promote the production of these lipids by primary producers in the lakes. We developed a novel salmon sterol index (SSI _a ) from values in surface sediments of the nine Alaskan lakes [(cholesterol + coprostanone + epicoprostanol + desmosterol)/(cholesterol + coprostanone + epicoprostanol + desmosterol + fucosterol + sitosterol + stigmastanol)] that was strongly related with salmon return density (pseudo R ² = 0.86 and RMSE = 0.071). This index also tracked historical sockeye escapement patterns and δ ¹⁵ N values in ²¹⁰ Pb‐dated lake sediment cores from Frazer, Karluk, Red, and Kinaskan lakes that span more than a century of salmon population history, suggesting that the index has potential as a proxy for tracking historical salmon populations, particularly when used in combination with independent biomarkers of salmon‐derived nutrient inputs. SSI _a and the other salmon sterol indices we developed show promise for improving and extending long‐term sockeye salmon population estimates using lake sediment records, which will help inform salmon conservation and management efforts.

We examined a combination of sediment biomarkers, including sterols, stanols, and δ ¹⁵ N, in lakes with well documented Sockeye salmon return histories to optimize methods to infer past changes in salmon escapement (i.e. the population that returns to their freshwater nursery lakes) based on dated sediment core records. Several sterols in surface sediment correlated strongly with salmon escapement across nine Alaskan lakes, particularly cholesterol, the predominant sterol in adult Sockeye salmon muscle tissue (R ² = 0.8, p = 0.001, F _1,8 = 28.3). Sediment concentrations of the plant-derived sitosterol and algal-derived fucosterol, absent in salmon muscle tissue, also correlated positively with salmon escapement, suggesting that salmon-derived nutrients from decomposing salmon indirectly promote the production of these lipids by primary producers within the aquatic ecosystem. We developed a novel salmon sterol index (SSIa) [(cholesterol + coprostanone + epicoprostanol + desmosterol) / (cholesterol + coprostanone + epicoprostanol + desmosterol + fucosterol + sitosterol + stigmastanol)] that correlated most strongly with salmon return density in surface sediments across nine Alaskan lakes (Pseudo R ² = 0.86, RMSE =0.071). This index also tracked Sockeye escapement patterns and δ ¹⁵ N values in dated sediments spanning over a century of salmon population history, suggesting its potential as a proxy for tracking historical salmon populations, particularly when used alongside independent proxies of salmon-derived nutrient inputs. In summary, the SSIa and the other SSIs we developed show promise to enhance and extend long-term Sockeye salmon population studies from lake sediment records that will help inform salmon conservation and management efforts.