soils

Soil eutrophication in seabird colonies affects cell wall composition: Implications for the conservation of rare plant species

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Otero, X.L., Fernández-Balado, C., Ferreira, T.O., Pérez-Alberti, A. and Revilla, G., 2021. Soil eutrophication in seabird colonies affects cell wall composition: Implications for the conservation of rare plant species. Marine Pollution Bulletin, 168, p.112469.

Seabird colonies exert a strong influence on coastal ecosystems, increasing soil nitrogen bioavailability and modifying plant communities. Previous studies have evidenced that increased N in soils leads to changes in plant cell wall composition; however, this effect has not been assessed in seabird colonies. The main objective of this study was to determine the influence of seabird colonies on nitrogen, cellulose and lignin content in cell walls. For this purpose, analyses were performed on droppings, soils and three native plant species (Armeria pubigera, Armeria pungens and Corema album) growing in yellow-legged gull colonies. The results showed that N excreted by yellow-legged gull is assimilated by plants, increases N content in plant tissues and reduces cellulose and lignin synthesis, therefore potentially altering plant resistance against phytoparasites.

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Seabird colonies as the main source of nutrients for the coastal ecosystems in the Atlantic Islands of Galicia National Park (NW Spain)

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De La Peña-Lastra, S., Pérez-Alberti, A. and Otero, X.L., 2021. Seabird colonies as the main source of nutrients for the coastal ecosystems in the Atlantic Islands of Galicia National Park (NW Spain). Chemosphere, 275, p.130077.

Seabirds form large colonies during the reproductive period, producing substantial changes in coastal ecosystems. The present study quantifies the amount of N and P deposited in colonies of yellow-legged gull (Larus michahellis) in the Atlantic Islands of Galicia National Park (AINP). Based on the composition of droppings, the amount of total N (TN), total P (TP) and bioavailable P (Pbio) deposited directly on the area occupied by the colony was determined. In addition, the amount of NH3 released into the atmosphere was also estimated by applying a bioenergetic model. The results indicated that 5.35 t total N, 3.35 t total P and 1.24 t bioavailable P are deposited in the colony annually. The archipelagos that received the greatest amount of nutrients were the Cíes Islands (2.37 t TN y−1, 1.48 t TP y−1, 0.55 t Pbio y−1), Sálvora (1.94 t TN y−1, 1.22 t TP y−1, 0.55 t Pbio y−1) and Ons (1.04 t TN y−1, 0.65 TP y−1, 0.24 t Pbio y−1). Rainwater from the colonies showed higher values of nutrients than in the control plot, possibly also due to gull influence. Therefore, the yellow-legged gull colony seems to be the most important source of nutrients at a local level, exerting a clear influence on the N and P cycles in this National Park. Another aspect worth taking into consideration is that increased N and P bioavailability may have a negative effect on the conservation of rare or threatened habitats and species by promoting the expansion of non-native ruderal species.

Effects of a yellow legged gull (Larus michahellis) colony on soils and cliff vegetation in the Atlantic Islands of Galicia National Park (NW Spain)

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De La Peña-Lastra, S., Gómez-Rodríguez, C., Pérez-Alberti, A., Torre, F. and Otero, X.L., 2021. Effects of a yellow legged gull (Larus michahellis) colony on soils and cliff vegetation in the Atlantic Islands of Galicia National Park (NW Spain). Catena, 199, p.105-115.

Seabirds are powerful environmental modulators, generating major changes in soil properties and vegetation in areas where their breeding colonies are established. One of the largest yellow-legged gull colonies in the world is found in the Atlantic Islands of Galicia National Park. In this study, we performed seasonal monitoring, over a period of 5 years, of the flora and soil in eight subcolonies characterized by different densities of gulls. Soil nutrient concentrations differed significantly between the control site and the subcolonies, as well as between seasons; the concentrations of N-NO3– and bioavailable P were highest in samples obtained at the end of the breeding season. Principal Component Analysis (PCA) transformed the environmental variables into three main components following varimax rotation. The PCA components were used as potential predictors in distance-based Redundancy Analyses (db- RDA) to explain turnover and also nestedness patterns in plant assemblages. Species turnover was explained by both natural (salinity) and nutrient gradients, while none of the relationships were significant in the nestedness analysis. Floristics inventories clearly revealed ruderalization of vegetation in the densest subcolonies, which led to total replacement of the most representative vascular plant species by eutrophic and ruderal species. PERMANOVA analysis showed that seagull density in 1991, when the seagull population was at its highest, could be used to group similar plant assemblages; however, this relationship was not observed for seagull density in 2011, which was 70–90% lower than in 1991. The study findings indicate that the environmental effects of seabird colonies are long lasting and that disappearance of the birds does not lead to restoration of the previous vegetation. The gull colony has irreversibly transformed the soil and vegetation of cliffs, generating a new environmental system.

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

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Aira, M. e 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, https://doi.org/10.1007/s42832-020-0023-9

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.

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

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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

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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.

Enrichment of trace elements in colonies of the yellow-legged gull (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain)

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De La Peña-Lastra, S., Pérez-Alberti, A. e Otero, X.L., 2019. Enrichment of trace elements in colonies of the yellow-legged gull (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain). Science of The Total Environment, 648, pp.1536-1548.

Marine-derived nutrients are known accumulate in seabird breeding colonies due to the deposition of nutrient-rich biological materials, thus greatly altering the functioning and dynamics of these terrestrial ecosystems. Here we present the results of a sampling survey carried out during three years in yellow-legged gull colonies in the Atlantic Islands of Galicia National Park (NW Spain) with the aim of evaluating the influence of the colonies on the accumulation of trace elements, including micronutrients (Cu, Zn, Se, Co, Mo, Ni) and toxic elements (Cr, Cd, Hg, Pb, As, Ag), in the surrounding environments. For this purpose, we analysed samples of biological materials produced by the seabirds (pellets, excrement, feathers, eggs) and of soil, plants and inland water from several different subcolonies and control zones without seabirds.

The concentrations of most of the elements were higher in excrement and pellets (mean values: Zn: 152, As: 50 mg kg−1, Cd: 6, Co: 5 mg kg−1) than in feathers and eggs. The flow of trace elements into the breeding colonies, considering only the excrement, revealed a very high level of trace element deposition for a supposedly pristine environment (Zn: 2667, Cd: 70, Cu: 315, As: 64 g ha−1). The total concentrations of trace elements in soil were consistent with the long-term impact of the seabirds. Thus, the values in areas which this impact was greatest were significantly higher than in the control zones, particularly considering the most labile geochemical fractions of the soil. The concentrations of some elements (i.e. Co, As, Cd) were also higher in the inland waters in the colonies than in control zones. Finally, the concentration of trace elements in plants varied depending on the species and element considered.

Trace elements in biomaterials and soils from a Yellow-legged gull (Larus michahellis) colony in the Atlantic Islands of Galicia National Park (NW Spain).

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Otero, X.L., de la Peña-Lastra, S., Romero, D., Nobrega, G.N., Ferreira, T.O., Pérez-Alberti, A., 2018. Trace elements in biomaterials and soils from a Yellow-legged gull (Larus michahellis) colony in the Atlantic Islands of Galicia National Park (NW Spain). Marine Pollution Bulletin, 133, pp.144-149.

Seabird colonies drastically transform the sites that they inhabit. Although the influence of seabirds on nutrient cycling has been investigated in numerous studies, the effects on trace elements has scarcely been considered. In this study, we determined the total contents of 9 trace elements in biomaterials (excrement, pellets, feathers and eggs) and soils in relation to the presence the Yellow-legged gull Larus michahellis. The concentrations of Zn, Cu and As were particularly high in the pellets and excrement. The total contents of the trace elements were significantly higher in the soils in the sub-colonies in which Yellow-legged gulls predominate than in soil from the control zone (with no gulls). The difference was even higher for the most reactive geochemical fractions. We observed that the oxidizable fraction was the most relevant fraction for almost all trace elements, indicating the importance of organic matter in trace element retention in sandy soils.

Effects of nesting yellow-legged gulls (Larus cachinnans Pallas) on the heavy metal content of soils in the Cies Islands (Galicia, North-west Spain)

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Otero Pérez, X. L. Effects of nesting yellow-legged gulls (Larus cachinnans Pallas) on the heavy metal content of soils in the Cies Islands (Galicia, North-west Spain). Marine Pollution Bulletin 36, 267–272 (1998).

Cd, Cr, Cu, Pb and Zn levels were determined in faeces of the yellow-legged gull Larus cachinnans in Galicia (NW Spain), and in soils from three breeding and one reference site. The levels of Cd, Cu, Zn and Pb in the soil were significantly higher at the site with highest gull density and with the longest history of use as a breeding site (Percha) than at the reference site. Zn levels were higher than levels of the other metals in all soil and faeces samples. Mean levels of metals in faeces were 305 mg kg-1 (Zn), 60 mg kg-1 (Cu), 40 mg kg-1 (Pb), 9.8 mg kg-1 (Cr) and 5.8 mg kg-1 (Cd).

Phosphorus in seagull colonies and the effect on the habitats. The case of yellow-legged gulls (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain)

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Otero, X. L. et al. Phosphorus in seagull colonies and the effect on the habitats. The case of yellow-legged gulls (Larus michahellis) in the Atlantic Islands National Park (Galicia-NW Spain). Science of The Total Environment 532, 383–397 (2015).

During the period 1980–2000, the yellow-legged gull population underwent exponential growth due to an increase in the availability of anthropogenic food resources. The aim of this study was to highlight the effect of the gull colonies on the P soil cycle and the associated effects on coastal ecosystems. Samples of soil, water and faecal material were collected in a colony of yellow-legged gulls (Cíes Islands) and in a control area. Four sampling plots were installed in the study areas, and samples were collected in summer and winter in 1997 and 2011. Sample analysis included soil characterization and determination of the total P content (TP), bioavailable-P and fractionated-P forms in the soils and faecal material. The 31P NMR technique was also used to determine organic P forms. Clear differences between the gull colony soils and the control soil were observed. The TP was 3 times higher in the gull colony soil, and the bioavailable P was 30 times higher than in the control soil. The P forms present at highest concentrations in the faecal material (P-apatite, P-residual and P-humic acid) were also present at high concentrations in the colony soil. The absence of any seasonal or annual differences in P concentration indicates that the P has remained stable in the soil over time, regardless of the changes in the gull population density. The degree of P saturation indicated that soils are saturated with P due to the low concentration of Fe/Al-hydroxides, which is consistent with a high P concentration in the run-off from the colonies. The P output from the colony soils to coastal waters may cause eutrophication of a nearby lagoon and the disappearance of a Zostera marina seagrass meadow. Similarly, the enrichment of P concentration in dune system of Muxieiro may induce irreversible changes in the plant communities.