Browsing by Subject "SUBSIDIES"

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  • Lienart, Camilla; Cirtwill, Alyssa R.; Hedgespeth, Melanie L.; Bradshaw, Clare (2022)
    Allochthonous subsidies to marine ecosystems have mainly focused on biogeochemical cycles, but there has also been recent interest in how terrestrial carbon (C) influences marine food webs. In the Baltic Sea, pine (Pinus sylvestris) pollen is found in large amounts in shallow bays in early summer. Pollen is a significant C-source in freshwater ecosystems and may also be important in coastal food webs. We examined the consumption of pollen and autochthonous resources by benthic invertebrates in shallow bays of the Baltic Sea. We used stable isotopes to estimate diets and reconstructed consumer-resource networks (food webs) for grazers and particulate organic matter (POM)-feeders to compare how these different guilds used pollen. We found that P. sylvestris pollen was consumed in small amounts by a variety of animals and in some cases made up a sizeable proportion of invertebrates' diets. However, invertebrates generally depended less on pollen than other resources. The degree of pollen consumption was related to feeding traits, with generalist invertebrate grazers consuming more pollen (> 10% of diet) than the more specialist POM-feeders (< 5% of diet contributed by pollen). POM-feeders may consume additional microbially-degraded pollen which was not identifiable in our model. We suggest that pollen is a small but substantial allochthonous C-source in shallow bay food webs of the Baltic Sea, with the potential to affect the dynamics of these ecosystems.
  • Favereau, Judith; Nagatsu, Michiru (2020)
    In this paper, we critically and constructively examine the methodology of evidence-based development economics, which deploys randomized field experiments (RFEs) as its main tool. We describe the context in which this movement started, and illustrate in detail how RFEs are designed and implemented in practice, drawing on a series of experiments by Pascaline Dupas and her colleagues on the use of bednets, saving and governance in Kenya. We show that this line of experiments have evolved to address the limitation of obtaining policy-relevant insights from RFEs alone, characterized as their lack of external validity in the literature. After examining the two prominent responses by leading figures of evidence-based development economics, namely machine learning and structured speculation, we propose an alternative methodological strategy that incorporates two sub-fields, namely experimental economics and behavioral economics, to complement RFEs in investigating the data-generating process underlying the treatment effects of RFEs. This strategy highlights promising methodological developments in RFEs neither captured by the two proposals nor recognized by methodologists, and also guides how to combine different sub-fields of economics.
  • Rodil, Ivan F.; Lastra, Mariano; López, Jesús; Mucha, Ana P.; Fernandes, Joana P.; Fernandes, Sara V.; Olabarria, Celia (2019)
    Sandy beaches, which represent the most common type of land-sea interface, harbor distinctive biotic communities and regulate the flow of energy between marine and terrestrial ecosystems. Accumulations of sea wrack on sandy beaches are of crucial importance for recycling beach nutrients and for regulating trophic connectivity and coastal functioning. We investigated the role of beaches as biogeochemical hotspots by examining the metabolic activity in accumulations of different species of wrack on two exposed beaches affected by different levels of human pressure. Experimental wrack patches provided large amounts of different sedimentary nutrients over time due to remineralization of the algae. Unsurprisingly, the variation in the nutrients present in the beach sediments was related to the species of wrack considered. Macroalgal wrack was metabolically very active and supported high respiration rates represented by intense CO2 fluxes. Importantly, we demonstrated that the wrack metabolic rate differed significantly depending on the algal species considered. Different macrofauna and bacterial assemblages were identified in the different wrack patches and on the different beaches. We suggest that human activities such as beach grooming can modify the wrack-associated communities, thus contributing to the variability in the biogeochemical processes and metabolic rates. Significant changes in the type and amount of wrack deposited on beaches can change fundamental processes related to the marine-terrestrial transfer of nutrients and energy and to the marine-atmospheric transfer of CO2 emissions, with ecological consequences for nearshore environments.