Differing ecological responses of seabirds to invasive species eradication

The impact of invasive species at seabird breeding islands causes a breakdown of important ecological functions such as prey consumption and nutrient transfer, and elevates extinction risk in impacted taxa. Eradicating invasive species from islands can result in substantial short-term recovery of seabird populations and consequently the prevalence of eradication programs as conservation tools is increasing. However, as the scale and complexity of eradications has increased, quantitative data on rates of recovery, especially from larger islands, remain limited. Furthermore, the mechanisms that govern recovery are poorly understood, limiting our ability to forecast outcomes and therefore prioritise effectively. Here, using the world's largest multi-species vertebrate eradication from Macquarie Island as a case study, we show how responses to invasive species and their eradication differ. Species with broad realised niches whose breeding phenology minimizes time on land and corresponds with summer resource abundance remained extant alongside invasive species while more habitat-specific species present in winter were extirpated. Following eradication, immigration and flexibility to colonise under-utilised optimal habitat appears to be boosting population growth in recolonising species, whereas established populations appear to be tethered to refugial habitats by the influence of philopatry, and their recovery is slower as a result. Unpicking these differential responses and the mechanisms behind them provides valuable information to help predict responses in other systems as future eradications are planned.

Intrauterine Transfer of Polyunsaturated Fatty Acids in Mother–Infant Dyads as Analyzed at Time of Delivery

Polyunsaturated fatty acids (PUFAs) are essential for fetal development, and intrauterine transfer is the only supply of PUFAs to the fetus. The prevailing theory of gestational nutrient transfer is that certain nutrients (including PUFAs) may have prioritized transport across the placenta. Numerous studies have identified correlations between maternal and infant fatty acid concentrations; however, little is known about what role maternal PUFA status may play in differential intrauterine nutrient transfer. Twenty mother–infant dyads were enrolled at delivery for collection of maternal and umbilical cord blood, and placental tissue samples. Plasma concentrations of PUFAs were assessed using gas chromatography (GC-FID). Intrauterine transfer percentages for each fatty acid were calculated as follows: ((cord blood fatty acid level/maternal blood fatty acid level) x 100). Kruskal–Wallis tests were used to compare transfer percentages between maternal fatty acid tertile groups. A p-value < 0.05 was considered significant. There were statistically significant differences in intrauterine transfer percentages of arachidonic acid (AA) (64% vs. 65% vs. 45%, p = 0.02), eicosapentaenoic acid (EPA) (41% vs. 19% vs. 17%, p = 0.03), and total fatty acids (TFA) (27% vs. 26% vs. 20%, p = 0.05) between maternal plasma fatty acid tertiles. Intrauterine transfer percentages of AA, EPA, and TFA were highest in the lowest tertile of respective maternal fatty acid concentration. These findings may indicate that fatty acid transfer to the fetus is prioritized during gestation even during periods of maternal nutritional inadequacy.

Field Cage Assessment of Feeding Damage by Riptortus pedestris on Soybeans in China

The bean bug, Riptortus pedestris, is a major pest of soybeans. In order to assess the critical stages of soybean damage by R. pedestris, we tested the damage to soybeans at different growth stages (R2, R4, and R6) caused by five densities of R. pedestris (1, 2, 3, 4, and 5) through a field cage experiment. The results show that the R4 stage was the most sensitive stage in terms of suffering R. pedestris injury damage, followed by the R6 stage and then the R2 stage. The number of stay green leaves was 7.04 per plant, the abortive pod rate of the soybeans was 56.36%, and the abortive seed rate of the soybeans was 46.69%. The dry weight of the soybeans was 14.20 g at the R4 stage; these values of R4 were significantly higher than at the R2 and R6 stages. However, the dry weight of soybean seed was 4.27 g and the nutrient transfer rate was 27.01% in the R4 stage; these values were significantly lower than in the R2 and R6 stages. The number of stay green leaves, abortive pod rates, and abortive seed rates were all increased significantly with increasing pest density at each stage of soybean growth. However, the nutrient transfer rate was significantly decreased with the increase in the pest density. Soybean nutrition factors changed after they suffered R. pedestris injury; the lipid content of the soybean seed decreased and the lipid content of the soybean plant increased compared to controls, when tested with a density of five R. pedestris in the R4 stage. These results will be beneficial to the future management of R. pedestris in soybean fields.

LPJmL-Med – Modelling the dynamics of the land-sea nutrient transfer over the Mediterranean region–version 1: Model description and evaluation

Land forcing (water discharge and nutrient loads) is reported as one of the major sources of uncertainty limiting the capacity of marine biogeochemical models. Runoff from rivers and coastal plains delivers significant amounts of nutrients to the Mediterranean Sea from agricultural activities and urban wastewater. Several recent studies show that variations in river inputs may play a significant role in marine biogeochemical cycles and the planktonic food web throughout the entire basin. The aim of this study is to estimate the water dischargeas as well as nitrate (NO3) and phosphate (PO4) release into the Mediterranean Sea from basin-wide agriculture and inhabited areas through the implementation of the biogeochemical land-sea nutrient transfer processes within the agro-ecosystem model Lund Potsdam Jena managed Land for the Mediterranean (LPJmL-Med). The representation of the nutrient transfer from land to sea has been introduced into LPJmL-Med by considering the following processes: mineralization, denitrification, adsorption, remineralization, nitrification, and phytoplankton dynamics. A compilation of a new input data set of fertilizer, manure and wastewater nutrient content [1961–2005] has been added to the LPJmL-Med forcing data set. The first basin-wide LPJmL simulation at 1/12° indicates that the model succeeds in simulating the interannual variability of water discharge for the main rivers in the Mediterranean Sea, especially the Po, Rhone and Ebro Rivers. A very high correlation (R-square values higher than 0.94) is found for these three rivers. Results also show a good consistency between the simulated nutrients concentration (NO3 and PO4) and available in-situ data. River outflows of NO3 and PO4 exhibit opposite trends in the Mediterranean Sea. NO3 showed a more or less continuous increase from the beginning of the 1960s until the present in all three rivers. PO4 trends are more heterogeneous. There is a strong increase in PO4 between 1960 and 1980, followed by a decrease in mean annual fluxes from the second half of the 1980s as a consequence of the banning of phosphates in detergents, and the construction of wastewater treatment plants in the different countries. Results show that wastewater strongly contributes to the river phosphate fluxes, while both agriculture and wastewater control the nitrogen (mainly as NO3) fluxes from rivers to the Mediterranean Sea.

Mycorrhizal fungi transfer nitrogen from tree to maize in subsistence farmers' fields

Trees within farmers' fields can enhance systems' longer-term productivity e.g., via nutrient amelioration, which is indispensable to attain sustainable agroecosystems. While arbuscular mycorrhizal fungi (AMF) are known to improve plant access to soil nutrients, the potential of AMF to facilitate nutrient transfer from trees to crops is unclear. We used the 15N (nitrogen) natural abundance technique together with root and AMF exclusion plots to assess if Faidherbia albida (faidherbia) trees deliver N to maize via associated AMF in smallholder fields. We show, here, that within one cropping season, maize obtained approximately 35 kg biologically fixed N ha-1 from faidherbia and AMF significantly contribute to this transfer of N. One third of tree-derived N in maize leaves was attributed to transfer via AMF and two thirds were explained by tree leaf litter input. Thus, the faidherbia-AMF association can enhance agroecosystem functioning and as such, attain greater sustainability of low-input cropping systems.