Target and untargeted screening of perfluoroalkyl substances in biota using liquid chromatography coupled to quadrupole time of flight mass spectrometry

Perfluoroalkyl substances (PFAS) are known to bioaccumulate and trigger adverse effects in marine birds. This study develops an extraction and analytical methodology for the target/untargeted analysis of PFAS in eggs of Yellow-legged gull (Larus michahellis) and Audouin's gull (Larus audouinii) and blood of Greater flamingo (Phoenicopterus roseus), which are used as bioindicators of organic chemical pollution. Samples were extracted by ultrasonication with acetonitrile and cleaned-up with activated carbon, and analysis was performed by ultra-high-performance liquid chromatography coupled to a quadrupole-time of flight mass spectrometer (UHPLC-Q-TOF) with negative electrospray ionization. Data-independent acquisition (DIA) was performed through full-scan acquisition to obtain MS1 at 6 eV and MS2 at 30 eV. In a first step, quantitative analysis of 25 PFAS was performed using 9 mass-labelled internal standard PFAS and quality parameters of the method developed are provided. Then, an untargeted screening workflow is proposed using the high-resolution PFAS library database from NORMAN to identify new chemicals through accurate mass measurement of MS1 and MS2 signals. The method permitted to detect several PFAS at concentrations ranging from 0.45 to 55.2 ng/g wet weight in gull eggs and from 0.75 to 125 ng/mL wet weight in flamingos' blood, with PFOS, PFOA, PFNA, PFUdA, PFTrDA, PFDoA, PFHxS and PFHpA the main compounds detected. In addition, perfluoro-p-ethylcyclohexylsulfonic acid (PFECHS, CAS number 646-83-3) and 2-(perfluorohexyl)ethanol (6:2 FTOH, CAS number 647-42-7) were tentatively identified. The developed UHPLC-Q-TOF target/untargeted analytical approach increases the scope of PFAS analysis, enabling a better assessment on contaminant exposure and promoting the use of bird species as bioindicators of chemical pollution.

Agricultural policies against invasive species generate contrasting outcomes for climate change mitigation and biodiversity conservation

Direct consequences of biological invasions on biodiversity and the environment have been largely documented. Yet collateral indirect effects mediated by changes in agri-environmental policies aimed at combating invasions remain little explored. Here we assessed the effects of recent changes in water management in rice farming, which are aimed at buffering the impact of the invasive apple snail (Pomacea maculata, Lamarck) on greenhouse gas emissions and diversity of waterbird communities. We used observational data from a 2-year field monitoring (2015-2016) performed at the Ebro Delta regional scale. We found that drying rice fields reduced methane emission rates by 82% (2015) and 51% (2016), thereby reflecting the contribution of rice farming to climate change. However, there was a marked reduction (75% in 2015 and 57% in 2016) in waterbird diversity in dry fields compared with flooded fields, thus suggesting that post-invasion policies might hinder biodiversity conservation. Our results highlight the need for accounting for potential collateral effects during the policy decision-making process to design efficient agricultural management plans that lessen undesirable agri-environmental outcomes.

Decrease in social cohesion in a colonial seabird under a perturbation regime

Social interactions, through influence on behavioural processes, can play an important role in populations’ resilience (i.e. ability to cope with perturbations). However little is known about the effects of perturbations on the strength of social cohesion in wild populations. Long-term associations between individuals may reflect the existence of social cohesion for seizing the evolutionary advantages of social living. We explore the existence of social cohesion and its dynamics under perturbations by analysing long-term social associations, in a colonial seabird, the Audouin’s gull Larus audouinii, living in a site experiencing a shift to a perturbed regime. Our goals were namely (1) to uncover the occurrence of long-term social ties (i.e. associations) between individuals and (2) to examine whether the perturbation regime affected this form of social cohesion. We analysed a dataset of more than 3500 individuals from 25 years of monitoring by means of contingency tables and within the Social Network Analysis framework. We showed that associations between individuals are not only due to philopatry or random gregariousness but that there are social ties between individuals over the years. Furthermore, social cohesion decreased under the perturbation regime. We sustain that perturbations may lead not only to changes in individuals’ behaviour and fitness but also to a change in populations’ social cohesion. The consequences of decreasing social cohesion are still not well understood, but they can be critical for the population dynamics of social species.

Predator arrival elicits differential dispersal, change in age structure and reproductive performance in a prey population

Predators are an important ecological and evolutionary force shaping prey population dynamics. Ecologists have extensively assessed the lethal effects of invasive predators on prey populations. However, the role of non-lethal effects, such as physiological stress or behavioural responses like dispersal, has been comparatively overlooked and their potential population effects remain obscure. Over the last 23 years, we developed a mark-recapture program for the Audouin's gull and an intensive carnivore monitoring program to assess how the appearance and invasion of the study site by carnivores affects population dynamics. We evaluate changes in turnover of discrete breeding patches within the colony, age structure and breeding performance. Once carnivores entered the colony, the number of occupied patches increased, indicating a higher patch turnover. Breeders responded by moving to areas less accessible to carnivores. More importantly, the presence of carnivores caused differential (and density-independent) breeding dispersal: experienced, better-performing breeders were more likely to leave the colony than younger breeders. This differential dispersal modified the age structure and reduced the reproductive performance of the population. Our results confirm the importance experience in the study of populations. The role of differential dispersal for animal population dynamics might be more important than previously thought, especially under scenarios of global change.

Colonisation in social species: the importance of breeding experience for dispersal in overcoming information barriers

Studying colonisation is crucial to understand metapopulations, evolutionary ecology and species resilience to global change. Unfortunately, few empirical data are available because field monitoring that includes empty patches at large spatiotemporal scales is required. We examine the colonisation dynamics of a long-lived seabird over 34 years in the western Mediterranean by comparing population and individual data from both source colony and the newly-formed colonies. Since social information is not available, we hypothesize that colonisation should follow particular dispersal dynamics and personal information must be crucial in decision making. We test if adverse breeding conditions trigger colonisation events, if personal information plays a role in colonisation and if colonisers experience greater fitness. Our results show a temporal mismatch between colonisation events and both density-dependence and perturbations at the source colony, probably because colonisers needed a longer prospecting period to compensate for the lack of public information. Colonisers were mostly experienced individuals gaining higher breeding success in the new colony. Our results highlight the demographic value that experienced individuals can have on metapopulation dynamics of social long-lived organisms.

Consecutive cohort effects driven by density-dependence and climate influence early-life survival in a long-lived bird

Conditions during early life, including maternal cohort effects, can influence the future fitness of individuals. This may be particularly true for long-distance migrating birds, because, apart from conditions experienced by cohorts during rearing, conditions during early life in regions far from breeding grounds may also influence their population dynamics. Very little is known about the fitness consequences of those conditions experienced by juveniles after independence, especially in wild populations and for long-lived birds. We used multi-event capture-recapture-recovery models and a unique 26-year dataset for the Audouin's gull (Larus audouinii) to assess for the first time whether survival was influenced by early conditions, both during the rearing period (i.e. a maternal cohort effect potentially affected by density dependence) and the first winter (i.e. a cohort effect driven by climate when birds disperse to wintering grounds). Our results show that juvenile survival was highly sensitive to early-life conditions and that survival decreased with stronger density dependence and harsh climate. The two consecutive cohort effects were of similar magnitude and they may represent a selection filter. Thus, early-life conditions had a strong impact on survival, and neglecting this complexity may hinder our understanding on how populations of long-lived animals fluctuate and respond to perturbations.