RESUMO
Persistent organic pollutants (POPs) bioaccumulate in the food chain and can cause ecotoxicity. In wild bird populations, various tissues are used to determine POP levels, including invasive (e.g., brain, fat, kidney, liver, muscle) and minimally-invasive tissues (e.g., blood, feather, preen oil). Minimally-invasive sampling, which does not require the death of the animal, opens new prospects for sampling birds as sentinels of environmental pollution and its consequences on fitness. However, POP variability between tissues is understudied, which is an essential prerequisite for making a reasoned choice about which tissues to sample. Here, we performed a meta-analysis of eight tissues across 115 studies comparing tissues across POP groups. We demonstrate increased use of minimally-invasive measures between 1974 and 2020. When grouping tissue correlations into three groups, "invasive:invasive", "invasive:minimally-invasive" and "minimally-invasive:minimally-invasive", we found that all three groups produced moderate to strong positive correlations with no difference seen between comparison groups. We demonstrate (1) lower POP concentrations in preen oil than fat, but no difference in detection frequencies, supporting preen oil use; (2) blood showed high concentration variability dependent on POP group but detection frequencies were comparable to liver and kidney; and (3) feathers demonstrated a significantly lower detection frequency than other matrices measured. By further researching minimally-invasive tissues, we increase our understanding of whether minimally-invasive tissues are ecologically representative of body-level toxicity. Our study supports blood and preen oil as substitutes for invasive measures when sampling living bird populations as they represent internal POP concentrations and provide significant benefits both practically and ethically.
RESUMO
Chemical pollution is a major man-made environmental threat to ecosystems and natural animal populations. Of concern are persistent organic pollutants (POPs), which can persist in the environment for many years. While bioaccumulating throughout the lives of wild animals, POPs can affect their health, reproduction, and survival. However, measuring long-term effects of POPs in wild populations is challenging, and therefore appropriate biomarkers are required in wildlife ecotoxicology. One potential target is telomere length, since telomere preservation has been associated to survival and longevity, and stressors as chemical pollution can disrupt its maintenance. Here, we investigated the effects of different classes of POPs on relative telomere length (RTL) and its rate of change (TROC) in wild long-lived Alpine swifts (Tachymarptis melba). As both RTL and TROC are often reported to differ between sexes and with chronological age, we tested for sex- and age-specific (pre-senescent vs. senescent, ≥ 9 age of years, individuals) effects of POPs. Our results showed that senescent females presented longer RTL and elongated telomeres over time compared to pre-senescent females and males. These sex- and age-related differences in RTL and TROC were influenced by POPs, but differently depending on whether they were organochlorine pesticides (OCPs) or industrial polychlorinated biphenyls (PCBs). OCPs (particularly drins) were negatively associated with RTL, with the strongest negative effects being found in senescent females. Conversely, PCBs led to slower rates of telomere shortening, especially in females. Our study indicates diametrically opposed effects of OCPs on RTL and PCBs on TROC, and these effects were more pronounced in females and senescent individuals. The mechanisms behind these effects (e.g., increased oxidative stress by OCPs; upregulation of telomerase activity by PCBs) remain unknown. Our results highlight the importance in wildlife ecotoxicology to account for sex- and age-related effects when investigating the health effects of pollutants on biomarkers such as telomeres.