Structuring pelagic trophic networks from the biomass size spectra

The selection and establishment of the structure (number and compartments, aggregation criteria, and trophic links) of the food webs is a critical task in trophic modelling. The present work proposes a systematic method to structure trophic networks in pelagic food webs. The biomass-size spectrum (BSS) is a well-established approach to analyze the structure of pelagic communities, and the body size is especially related to the ecological role of the organisms in the pelagic environment. To structure food webs, this work uses detailed arrangements of the community in size classes with increasing widths (like Sheldon-type BSS) as first aggregation criteria, and BSS theory as a framework to integrate the available knowledge about feeding selectivity in order to obtain a method to identify the trophic links between compartments. Diet composition matrices were estimated through the combination of a probability of encounter for each food type and a specific probability of ingestion related to the food size selectivity and other food quality characteristics (e.g., morphology and nutritional quality). The feasibility of this approach has been illustrated through data of size-structured communities extracted from the literature including different planktonic predator guilds (nanoflagellates, cladoceran-dominated zooplankton and copepod-dominated zooplankton) in a high mountain lake (La Caldera, Spain), two subtropical wetland lakes (meso-oligotrophic Laguna Galarza and eutrophic Laguna Iberá, Argentina) and a marine microcosm (Alborán Sea, Mediterranean). The identification of “who eats whom” and “by how much” also allows for more accurate analyses of the trophic control in the BSS. Extensive analyses of the balance between top-down and bottom-up controls were developed for the feeding interactions of the study cases.     

Controlling risks of P water pollution by sorption on soils,pyritic material,granitic material,and different by-products: effects of pH and incubation time

Environmental Science and Pollution Research - Batch experiments were used to test P sorbent potential of soil samples, pyritic and granitic materials, mussel shell, mussel shell ash, sawdust, and...     

Arsenic release from pyrite ash waste over an active hydrogeological system and its effects on water quality

Environmental Science and Pollution Research - Arsenic is a potentially toxic element of concern for environmental compartments, and it is a frequent pollutant in many abandoned industrial sites....     

A critical geography approach to land and water use in the tourism economy in Los Cabos,Baja California Sur,Mexico

ABSTRACT

This paper offers a critical assessment of how tourism development in the municipality of Los Cabos, Baja California Sur affects land and water use. Los Cabos is a seaside tourism Mecca located at the southern tip of the Baja California peninsula, in Mexico’s northwest. There, subsidised profits and a process of dispossession in the tourism sector have to do mainly with land and water appropriation in the form of restrictions to beach access by the local population, urban segregation and, in an arid region, privileging water provision for the tourism industry over the needs of the population. In order to sustain these claims, we map water and land use for tourism in Cabo San Lucas. We also analyse the expansion of the Los Cabos type of tourism to the small town of La Ribera, in the East Cape-Cabo Pulmo area, where marinas and high scale housing for residential tourism sprout along the coast. We argue that the seemingly ever-growing presence of tourism in the region carries with it an urgent call for the reappraisal of current approaches to land and water use, if local resources are to deliver quality of life for the population, and not only economic profitability for (mostly) foreign capital. Analytically, we address these issues by unpacking David Harvey’s concept of accumulation by dispossession, which – we argue – is for our purposes a broader tent than the (mostly Latin American) theorisations on extractivism, as we explain later in the relevant section of the paper.     

Toxicity evaluation of cypermethrin,glyphosate, and malathion,on two indigenous zooplanktonic species

In Aguascalientes, Mexico, there is a special concern about pesticides because of their intensive use on guava production areas, which are located in the vicinity of water reservoirs; thus, non-target organisms could be exposed. Thereafter, the aim of this work was to assess the effect of cypermethrin, Faena® (glyphosate), and malathion, which are the most used pesticides in Aguascalientes’ guava production, on the indigenous freshwater species Alona guttata (cladoceran) and Lecane papuana (rotifer). Acute 48-h toxicity tests were carried out, and LC₅₀ values were calculated. Then, five sublethal concentrations (1/80, 1/40, 1/20, 1/10, and 1/5 of the respective LC₅₀) were selected for the chronic assays: (a) intrinsic growth rate analysis in the rotifer and (b) partial life table analysis in the cladoceran. The results of the acute toxicity tests showed that A. guttata was more sensitive to malathion (LC₅₀ = 5.26 × 10^?3 mg/L) at concentrations found in natural environments with continuous application on guava fields, whereas L. papuana was more sensitive to Faena® (LC₅₀ = 19.89 mg/L). The somatic growth of A. guttata was inhibited for the chronic exposure to cypermethrin. In addition, cypermethrin and Faena® seemed to exert endocrine disruptive effects on A. guttata. Moreover, malathion chronic exposure significantly decreased the survival of A. guttata. Moreover, L. papuana was affected chronically for the three pesticides.     

Performance of an integrated system combining microalgae and vertical flow constructed wetlands for urban wastewater treatment

Environmental Science and Pollution Research - The present study investigated the performance of an integrated system, combining the sequential use of microalgae (MA) and vertical flow constructed...     

Modeling road building,deforestation and carbon emissions due deforestation in the Ecuadorian Amazon: the potential impact of oil frontier growth

In the Ecuadorian Amazon roads play the major role in transforming land cover. Since the beginning of the oil development in this region, oil exploration and road building have been linked. The objectives of this paper are twofold: First, to present a scenario of future deforestation as result of expanding the oil frontier in the Ecuadorian Amazon until the year 2030. Second, to produce an analysis of possible carbon emission scenarios as results of the deforestation produced. This paper tries to shed light into how the development of new oil concessions impact land associated environmental services. The paper uses spatial explicit simulations, that are based on parameters built using past land transitions from areas that experimented oil development, and that explain possible outcomes in the year 2030 using current and predicted road network. Simulations indicate that under current transition probabilities and a conservative scenario road construction, more than 2 million hectares will be affected, which is 35% of the area covered by concessions, which would release 51 to 148 MT of carbon to the atmosphere. This paper illustrates the strong links between road building and deforestation, where even small amount of road construction can have large effects on land cover.     

Markets and climate are driving rapid change in farming practices in Savannah West Africa

Agricultural practices have constantly changed in West Africa, and understanding the factors that have driven the changes may help guide strategies to promote sustainable agriculture in the region. To contribute to such efforts, this paper analyzes drivers of change in farming practices in the region using data obtained from surveys of 700 farming households in five countries (Burkina Faso, Ghana, Mali, Niger and Senegal). The results showed that farmers have adopted various practices in response to the challenges they have faced during the last decade. A series of logit models showed that most changes farmers made to their practices are undertaken for multiple reasons. Land use and management changes including expanding farmed areas and using mineral fertilization and manure are positively related to perceived changes in the climate, such as more erratic rainfall. Planting new varieties, introducing new crops, crop rotation, expanding farmed area and using pesticides are positively associated with new market opportunities. Farm practices that require relatively high financial investment such as use of pesticides, drought-tolerant varieties and improved seeds were positively associated with the provision of technical and financial support for farmers through development projects and policies. Changes in markets and climate are both helping to promote needed changes in farming practices in West Africa. Therefore, policies that foster the development of markets for agricultural products, and improved weather- and climate-related information linked to knowledge of appropriate agricultural innovations in different environments are needed.     

Socioeconomic Drivers of Deforestation in the Northern Ecuadorian Amazon

Investigations of land use/land cover (LULC) change and forest management are limited by a lack of understanding of how socioeconomic factors affect land use. This lack also constrains the predictions of future deforestation, which is especially important in the Amazon basin, where large tracts of natural forest are being converted to managed uses. Research presented in this article was conducted to address this lack of understanding. Its objectives are (a) to quantify deforestation in the Northern Ecuadorian Amazon (NEA) during the periods 1986–1996 and 1996–2002; and (b) to determine the significance and magnitude of the effects of socioeconomic factors on deforestation rates at both the parroquia (parish) and finca (farm) levels. Annual deforestation rates were quantified via satellite image processing and geographic information systems. Linear spatial lag regression analyses were then used to explore relationships between socioeconomic factors and deforestation. Socioeconomic factors were obtained, at the finca level, from a detailed household survey carried out in 1990 and 1999, and at the parroquia level from data in the 1990 and 2001 Ecuadorian censuses of population. We found that the average annual deforestation rate was 2.5% and 1.8%/year for 1986–1996 and 1996–2002, respectively. At the parroquia level, variables representing demographic factors (i.e., population density) and accessibility factors (i.e., road density), among others, were found to be significantly related to deforestation. At the farm level, the factors related to deforestation were household size, distance by road to main cities, education, and hired labor. The findings of this research demonstrate both the severity of deforestation in the Northern Ecuadorian Amazon and the array of factors affecting deforestation in the tropics.     

Assessment of trace metal concentration in feathers of seabird (Larus dominicanus) sampled in the Florianópolis, SC, Brazilian coast

Cd, Co, Cr, Cu, Mn, Ni, Zn, and Pb were measured in feather samples of adult, subadult, and juvenile of Larus dominicanus, sampled in the Florianólis, SC, in the south of Brazil in December 2005, by flame atomic absorption spectrophotometry. The average of the distribution of Cd concentration in adult feathers (0.072 μg g^???1) was significantly different than that found in juvenile feathers (0.021 μg g^???1). Cu concentration averages were not significantly different between adults (13.30 μg g^???1), subadults (9.67 μg g^???1), and juveniles (13.76 μg g^???1). For adults and juveniles there was significant difference in feather concentrations for Cd, Co, Cr, Ni, and Pb. The distribution of Mn concentration averages in feathers differs between adults (11.36 μg g^???1) and juveniles (1.184 μg g^???1). Ni concentration averages of adults (5.92 μg g^???1) were significantly higher than those of juveniles (2.23 μg g^???1). For Pb, concentration averages were significantly higher in adults (7.53 μg g^???1) than in juveniles (1.47 μg g^???1). The concentration of Co and Cr in juvenile and subadults are statistically different when compared with the adults. In the present study, levels of Cd, Co, Cr, Mn, Ni, Zn, and Pb increased with age. The concentrations of essential trace elements in L. dominicanus were generally comparable to values reported in other studies. With non-essential metals (Cd, Pb, and Ni), in our study, L. dominicanus had lower values than those reported for their northern Atlantic counterparts.