Yellow-legged gull eggs (Larus michahellis) as persistent organic pollutants and trace metal bioindicator for two nearby areas with different human impact

The concentration of different persistent organic pollutants (POPs including chlorinated and brominated compounds) and trace metals and metalloids (As, Cd, Cu, Cr, Pb, Hg, Ni, and Zn) was examined in eggs from two colonies of yellow-legged gulls. The two colonies are established in Ría de Vigo, Northwest Spain, with a distance between them of only 10 km, one in Vigo town (industrial and harbour activities) and the other in the Cíes Islands in a Natural Park and Marine Protected Area –MPA- (with no known anthropogenic inputs). Statistically significant differences for the two colonies were observed for Hg, the sum of 7 CBs, the sum of DDTs y and the sum of 9 PBDEs, with values that could be causing some toxic effects in the area of the most anthropogenically influenced colony. The estimated isotopic niche was also calculated, based on δ15N and δ13C, for the two colonies, pointing to a wider diet in the Cíes colony when compared to the diet in the Vigo colony. The study supports the use of the yellow-legged seagull eggs as a bioindicator of pollution capable of differentiating pollution level even in geographically close areas.

Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development

Noguera, J.C., da Silva, A. and Velando, A., Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development. Molecular Ecology.

It is often assumed that the transfer of maternal glucocorticoids (GCs; e.g. corticosterone or cortisol) to offspring is an inevitable cost associated with adverse or stressful conditions experienced by mothers. However, recent evidence indicates that maternal GCs may adaptively program particular physiological and molecular pathways during development to enhance offspring fitness. In this context, an important mechanism through which maternal GCs may lastingly affect offspring phenotypic quality and survival is via effects on embryo telomerase activity and so on offspring postnatal telomere length. Here, using a field experimental design for which we manipulated the corticosterone content in yellow‐legged gull (Larus michahellis) eggs, we show that embryos from corticosterone‐injected eggs not only had a higher telomerase activity but also longer telomeres just after hatching. A complementary analysis further revealed that gull hatchlings with longer telomeres had a higher survival probability during the period when most of the chick mortality occurs. Given the important role that telomere length and its restoring mechanisms have on ageing trajectories and disease risk, our findings provide a new mechanistic link by which mothers may presumably shape offspring life‐history trajectories and phenotype.

Essential ocean variables and high value biodiversity areas: Targets for the conservation of marine megafauna

García-Barón, I., Santos, M.B., Saavedra, C., Astarloa, A., Valeiras, J., Barcelona, S.G. and Louzao, M., 2020. Essential ocean variables and high value biodiversity areas: Targets for the conservation of marine megafauna. Ecological Indicators, 117, p.106504.

Effective conservation and management measures are needed to face the unprecedented changes that marine ecosystems, and particularly marine megafauna, are suffering. These measures require the identification of high-value biodiversity areas (HVBAs) which in turn require the identification of the essential ocean variables (EOVs) that shape the environmental envelope of communities (i.e. space defined by a set of environmental variables). The aim of this study was to delineate and characterise the HVBAs for the north and northwestern Spanish seabird and cetacean community taking advantage of the sightings collected during the annual PELACUS oceanographic survey (2007–2016). We used distance sampling methodology to analyse the species detectability based on environmental conditions. Then, we delimitated the HVBAs and identified the EOVs defining the environmental envelope of the community based on a spatio-temporal modelling approach using Generalized Additive Models. Overall, the main environmental variables driving species abundance were the sea surface temperature (SST), the distance to the shelf-break and the chlorophyll-a concentration (Chl-a). The SST and Chl-a were identified as dynamic EOVs due to their highest relative predictor importance, driving the environmental envelope and shaping areas of higher density. HVBAs were located mainly over the northwestern Spanish waters and decreased towards the inner Bay of Biscay remaining spatially stable over the study period. By identifying community-level HVBAs, we can understand the underlying ecological and oceanographic processes driving the spatio-temporal patterns of biological communities, such as those composed by seabirds and cetaceans. This information would identify conservation targets to assist the allocation of management resources. In addition, the location of HVBAs can help to fulfil the emergent need for sound spatial information to support the implementation of marine spatial planning.

Gull chicks grow faster but lose telomeres when prenatal cues mismatch the real presence of sibling competitors

Noguera, J.C. and Velando, A., 2020. Gull chicks grow faster but lose telomeres when prenatal cues mismatch the real presence of sibling competitors. Proceedings of the Royal Society B, 287(1927), p.20200242.

During embryonic life, individuals should adjust their phenotype to the conditions that they will encounter after birth, including the social environment, if they have access to (social) cues that allow them to forecast future conditions. In birds, evidence indicates that embryos are sensitive to cues from clutch mates, but whether embryos adjust their development to cope with the expected level of sibling competition has not hitherto been investigated. To tackle this question, we performed a ‘match versus mismatch’ experimental design where we manipulated the presence of clutch mates (i.e. clutch size manipulation) and the real (postnatal) level of sibling competition (i.e. brood size manipulation) in the yellow-legged gull (Larus michahellis). We provide evidence that the prenatal cues of sibling presence induced developmental changes (such as epigenetic profiles) that had programming effects on chick begging behaviour and growth trajectories after hatching. While receiving mismatching information favoured chick begging and growth, this came at the cost of reduced antioxidant defences and a premature loss of telomeres. Our findings highlight the role of the prenatal social environment in developmental plasticity and suggest that telomere attrition may be an important physiological cost of phenotype–environment mismatch.

Soil under dead or live organic matter systems: Effect of European shag (Phalacrocorax aristotelis L.) nesting on soil nematodes and nutrient mineralization.

Aira, M. and Domínguez, J., 2020. Soil under dead or live organic matter systems: Effect of European shag (Phalacrocorax aristotelis L.) nesting on soil nematodes and nutrient mineralization. Soil Ecology Letters, pp.1-7.

Here we studied whether soil systems differ if they are under the influence of live (plants) or dead organic matter systems (nest) in terms of C and N mineralization, microbiological characteristics and nematode trophic group structure. We analyzed physicochemical and microbiological properties of soils inside and outside nests of the European shag (Phalacrocorax aristotelis L.) on the Cíes Islands (NW Spain). We sampled fresh soil below dead (nests) and live organic matter (plants) (paired samples, n = 7). Soil of nests had lower organic matter and higher electric conductivity and dissolved organic C and extractable N contents than the soil of plants. Microbial biomass and activity were greater in soil of nests than in soil of plants. The abundance of nematode trophic groups (bacterivores, fungivores, omnivores and herbivores) differred between soils of nests and plants, and the soil of plants supported a more abundant and diverse nematode community. The present results points to that source of organic matter promote differences in the decomposer community, being more efficient in soil of nests because C mineralization is greater. Further, this occurred independently of the complexity of the systems, higher in the soil of plants with more groups of nematodes.

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Soil nutrient dynamics in colonies of the yellow-legged seagull (Larus michahellis) in different biogeographical zones

De la Peña-Lastra, S., Affre, L. and Otero, X.L., 2020. Soil nutrient dynamics in colonies of the yellow-legged seagull (Larus michahellis) in different biogeographical zones. Geoderma, 361, p.114109.

Seabirds drastically alter the ecosystems where they establish their colonies. However, previous studies have not considered how colonies of the same species affect their surroundings in different environmental contexts. The main objective of this study was to determine the degree to which environmental factors (particularly climate and lithology) modulate the impact of seabird colonies on soil nutrients. For this purpose, two breeding colonies of the yellow-legged gull were selected: one located in the Atlantic Islands National Park (AINP, Atlantic region) and the other in Calanques National Park (CNP, Mediterranean region). In both parks, samples of soil and excrement were obtained from colonies with different densities of birds and in control zones, without birds, in two different seasons (winter and summer). The samples were analysed to determine the concentrations of N-NO3, N-NH4+, total P and different geochemical P forms, including bioavailable P. The colony soils were enriched in N and P relative to soils from the control zones. However, the annual nutrient dynamics were modulated by the environmental conditions in each park. In winter in CNP, NH4+ concentrations were low and similar to those in the control zones, while the concentrations of NO3 were highest at this time of year. By contrast, in AINP, the annual N cycling appeared to be less variable, although the NH4+ concentrations were lower than in the control zone in winter, while those of NO3 remained high, despite the high rainfall in this season. The concentrations of P (total and bioavailable) remained high in soils in both parks throughout the year. However, fractionation of the P forms revealed different geochemical behaviour at the two sites. In CNP, calcium phosphate and residual P were the dominant fractions. In AINP, the P was distributed more homogeneously between the different fractions, with a slight predominance of the P associated with Al hydroxides and clays. The findings clearly show alteration of the cycling of both nutrients in both parks, although the impact is modulated by the environmental conditions at each location.

Food-web interactions in a coastal ecosystem influenced by upwelling and terrestrial runoff off North-West Spain

Paradell, O.G., López, B.D., Methion, S. and Rogan, E., 2020. Food-web interactions in a coastal ecosystem influenced by upwelling and terrestrial runoff off North-West Spain. Marine Environmental Research, p.104933.

Ecopath with Ecosim has been used to create mass-balance models of different type of ecosystems around the world to explore and analyse their functioning and structure. This modelling framework has become a key tool in the ecosystem approach to fisheries management, by providing a more comprehensive and holistic understanding of the interactions between the different species. Additionally, Ecopath with Ecosim has provided a useful framework to study ecosystem maturity, changes in the ecosystem functioning over time and the impact of fisheries and aquaculture on the ecosystem, among other aspects. The present work explores the ecosystem functioning and structure in an anthropogenically impacted coastal area, influenced by seasonal coastal upwelling and high input of nutrients from rias (ancient drowned tectonic valleys) off North-West Spain. A mass-balance model with 23 functional groups was created using Ecopath to study the trophic interactions in the ecosystem during the post-upwelling period (August to October) in 2017. The model described an immature, wasp-waist ecosystem, that shared characteristics of ecosystems found in upwelling areas and ecosystems found in fjords or coastal embayments. Deeper analyses highlighted the importance of small planktivorous pelagic fish as a keystone functional group, and of zooplankton, blue whiting (Micromesistius poutassou) and phytoplankton as structuring groups in the ecosystem. Additionally, the study revealed that the existing fishing pressure on species of intermediate-high trophic levels could alter ecosystem functioning and structure, and ultimately affect top predators in the area. Findings of this study provide baseline information in ecosystem functioning and structure in the area and highlight the need to deeper study the effects of fisheries and their potential impacts on top predators.

Anthropogenic food resources, sardine decline and environmental conditions have triggered a dietary shift of an opportunistic seabird over the last 30 years on the northwest coast of Spain

Calado, J.G., Paiva, V.H., Ramos, J.A., Velando, A. & Munilla, I., 2020. Anthropogenic food resources, sardine decline and environmental conditions have triggered a dietary shift of an opportunistic seabird over the last 30 years on the northwest coast of Spain. Regional Environmental Change, 20(1), p.10.

Human activities and environmental conditions are the main drivers of ecosystem change. One major alteration near the western Iberian coast has been the collapse of the Atlanto-Iberian sardine Sardina pilchardus stock, with important cascading effects on marine top predators. We investigated the effect of long-term changes in fishery landings, sardine availability and environmental conditions on the diet of the yellow-legged gull Larus michahellis in the northwest coast of Spain, over the last 30 years (1987–2017). Dietary trends of gulls were investigated through the analysis of 5010 pellets that revealed a sharp decline of fish and refuse and a shift to a crustacean-based diet. General additive mixed models showed that both total fish and sardine occurrences in gull pellets were negatively associated with total fishery landings and positively associated with sardine landings, suggesting fish depletion and higher fishing efficiency (i.e. reduced discards) during the study period. The winter North Atlantic Oscillation (NAO) index was also positively related with sardine occurrence in gull pellets, possibly due to low sardine abundance and rough conditions in years with very low NAO values. The refuse decline was most probably caused by the closure of open-air landfills, implemented under the European Union Landfill Directive. Our results suggest that changes in fishing practices and waste disposal were the main factors responsible for the sharp decline of fish and refuse in yellow-legged gull diet.

Bird embryos perceive vibratory cues of predation risk from clutch mates

Noguera, J.C. and Velando, A., 2019. Bird embryos perceive vibratory cues of predation risk from clutch mates. Nature ecology & evolution, 3(8), pp.1225-1232.

During development in fluctuating environments, phenotypes can be adjusted to the conditions that individuals will probably encounter later in life. As developing embryos have a limited capacity to fully capture environmental information, theory predicts that they should integrate relevant information from all reliable sources, including the social environment. In many oviparous species, embryos are able to perceive cues of predator presence in some circumstances, but whether this information is socially transmitted among clutch mates—promoting phenotypic adjustments in the whole clutch—is unknown. Here, using an experimental design for which we modified the exposure to some, but not all, embryos of the same clutch to cues of predator presence (that is, alarm calls), we show that exposed embryos of the yellow-legged gull (Larus michahellis) and their unexposed clutch mates showed similar developmental changes that were absent in embryos from control clutches. Compared with the control broods, both embryos that were exposed to alarm calls and their unexposed clutch mates showed altered prenatal and postnatal behaviours, higher levels of DNA methylation and stress hormones, and reduced growth and numbers of mitochondria (which may be indicative of the capacity for energy production of cells). These results strongly suggest that gull embryos are able to acquire relevant environmental information from their siblings. Together, our results highlight the importance of socially acquired information during the prenatal stage as a non-genetic mechanism promoting developmental plasticity.

Marine megafauna niche coexistence and hotspot areas in a temperate ecosystem

Louzao, M., Valeiras, J., García-Barcelona, S., González-Quirós, R., Nogueira, E., Iglesias, M., Bode, A., Vázquez, J.A., Murcia, J.L., Saavedra, C. and Pierce, G.J., 2019. Marine megafauna niche coexistence and hotspot areas in a temperate ecosystem. Continental Shelf Research, 186, pp.77-87. 

In the last few decades, there has been a remarkable development of niche models to help understand the ecological response of species to current rapid environmental changes. In the present study, we applied niche modelling to the megafauna community of shelf waters of the northwestern (NW) and northern Iberian Peninsula in order to analyse the coexistence of different species taking into consideration their niche preferences. The Spanish Institute of Oceanography conducts the PELACUS multidisciplinary survey annually to assess pelagic fish stocks and collect information on the status of other ecosystem components, such as oceanographic conditions, phytoplankton, zooplankton and marine megafauna. Using data collected from these surveys, we developed niche models for 14 marine megafauna taxa (3 cetaceans, 10 seabirds and 1 fish) incorporating multi-trophic ecological descriptors collected simultaneously during the surveys alongside the more commonly used oceanographic variables (e.g. chlorophyll a and sea surface temperature). Megafauna niche models were developed by pooling observations from 2007 to 2013 and were found to be driven by mean fish biomass and its variability, in addition to sea surface temperature. Hierarchical clustering identified four distinct megafauna assemblages, the first comprising wide-ranging species and the other three associated with shelf-slope waters in Galicia, coastal/shelf waters in Galicia, and the eastern Cantabrian Sea, respectively. Community-level hotspot areas were found in shelf and shelf-break sectors of Galicia, along with small diversity spots scattered throughout the Cantabrian coastal area. Our results showed that synoptically collected survey-based ecological descriptors, especially acoustic-based preyscapes, were among the most important variables explaining megafauna niche preference. These findings highlight the advantage of using integrated ecosystem surveys to collect simultaneous information on a suite of ecosystem components for spatial assessments.