From small-scale habitat loopholes to decadal cycles: a habitat-based hypothesis explaining fluctuation in pelagic fish populations off Peru

The Peru‐Humboldt Current system (HCS) supports the world's largest pelagic fisheries. Among the world's eastern boundary current systems, it is the most exposed to high climatic stress and is directly affected by El Niño and La Niña events. In this volatile ecosystem, fish have been led to develop adaptive strategies in space and time. In this paper, we attempt to understand the mechanisms underlying such strategies, focusing on the El Niño 1997–98 in Peru from which an extensive set of hydrographic, capture and acoustic survey data are available. An integrated analysis of the data is crucial, as each has substantial shortcomings individually; for example, both catch data and acoustic surveys may easily lead to wrong conclusions. Existing hypotheses on anchovy and sardine alternations lead us to a ‘habitat‐based’ synthetic hypothesis. Using our data, an integrated approach evaluated how fish responded to habitat variation, and determined the consequences in terms of fish‐population variability. Various factors occurring at a range of different spatio‐temporal scales were considered: interdecadal regime (warm ‘El Viejo’/cool ‘La Vieja’ decadal scale); strength and the duration of the El Niño Southern Oscillation event (interannual scale); population condition before the event (interannual scale); fishing pressure and other predation (annual scale); changes in reproductive behaviour (intra‐annual scale); presence of local upwelling (local scale). During El Niño 1997–98, anchovy was able to exploit a small‐scale temporal and spatial ‘loophole’ inside the general unfavourable conditions. Moreover, sardine did not do better than anchovy during this El Niño and was not able to take advantage of the ‘loophole’ opened by this short‐term event. Our results question the traditional view that El Niño is bad for anchovy and good for sardine.     

Extensive cage culture of pejerrey (Odontesthes bonariensis) in a shallow pampean lake in Argentina

Pejerrey is an important zooplanktivorous native fish of the Argentinean inland waters. It has been traditionally propagated for stocking purposes by relatively costly semi‐intensive and intensive methods. In this study, we evaluated the implementation of an extensive culture method by using floating cages in a shallow pampean lake. Four cages were installed in the Lacombe Lake and stocked with juveniles (16.24 ± 1.69 mm length) at 50 fish m^?3 density for growing until the size of 150 mm, which is considered as a suitable size for stocking. Throughout the experiment, the temperature ranged between 10 and 26 °C and the zooplankton biomass ranged between 12 and 3269 μg dw L^?1. The growth patterns in the length were similar in the four cages and directly related to the lake thermal conditions and zooplankton availability. The average final length after 315 days was 154.4 ± 8.8 mm. The survival rates ranged between 53.5% and 64.7% during the first 110 days and 11.1–25.7% at termination. Growth rate for the first 2 months was the highest documented for pejerrey culture. This simple technique offers the possibility to produce juvenile pejerrey at a low cost and provides the alternative of reinforcing the natural populations with fish already adapted to the natural environmental conditions.     

A rare Cryptosporidium parvum genotype associated with infection of lambs and zoonotic transmission in Italy

An outbreak of cryptosporidiosis occurred in a mixed sheep/cattle farm of Central Italy in October 2011. A total of 450 ovines (250 sheep and 200 lambs) and 140 bovines (130 cows and 10 calves) were housed in two separated units, at the time of the outbreak. About half of the lambs had diarrhea due to Cryptosporidium sp. with a mortality rate of 80%; calves were not infected. Genomic DNA was extracted from an archived slide and from fecal specimens, and the parasite was identified as Cryptosporidium parvum by PCR and sequence analysis at the CpA135 gene. Genotyping at the GP60 gene showed the presence of a very rare genotype, IIaA20G2R1. Shortly after the outbreak was identified, the son of the farm's owner, aged 18 months, experienced an acute gastroenteritis and was hospitalized due to recurrent episodes of diarrhea, fever, vomiting and lack of appetite. The feces tested negative for bacteria and viruses, whereas cryptosporidiosis was diagnosed by microscopy and an immunochromatographic test. Molecular typing identified the C. parvum genotype IIaA20G2R1 in the feces of the child. This is the first case of transmission of cryptosporidiosis in Italy involving lambs as source of oocysts infectious to humans.     

Morphologic and physiologic changes induced by Clostridium perfringens type A alpha toxin in the intestine of sheep

OBJECTIVE: To evaluate the morphologic and physiologic changes induced by Clostridium perfringens type A (alpha toxin in the ileum and colon of sheep. SAMPLE POPULATION: 16 ligated intestinal loops in 4 Merino lambs and 18 explants of ileum and colon from slaughtered lambs. PROCEDURE: alpha Toxin-induced fluid accumulation was evaluated in ligated ileal and colonic loops of sheep. Tissues were evaluated morphologically by use of gross and histologic examination. Effects of toxin on in vitro intestinal net water transport were tested in modified Ussing chambers. RESULTS: Ovine ileal and colonic loops incubated with C perfringens type A alpha toxin retained more fluid than control loops. Histologically, in the ileum of lambs inoculated with 300 LD50 of alpha toxin/mL, there was a mild to moderate multifocal infiltration of neutrophils in the lamina propria and submucosa. The colonic loops of lambs inoculated with 30 or 300 LD50 of alpha toxin/mL had excessive mucus in the lumen, a moderate amount of neutrophils mixed with mucus in the intestinal lumen, and moderate multifocal infiltration of the lamina propria and submucosa with neutrophils; the blood vessels of these layers were engorged with neutrophils. In vitro measurements of water transport also revealed inhibition of net epithelial water absorption in ileum and colon incubated with alpha toxin on the mucosal side. CONCLUSIONS AND CLINICAL RELEVANCE: These results indicate that alpha toxin induces alterations in sheep intestine. Clostridium perfringens type A organisms that produce alpha toxin could be responsible for diseases of intestinal origin in some ruminants.     

Carbon dynamics in small tropical catchments under preserved forest and cacao agroforestry systems

Agroforestry Systems - Inland waters such as streams that receive carbon from terrestrial landscapes usually have a net heterotrophic metabolism and emit significant amounts of CO2 to the...     

Woody leguminous trees: New uses for sustainable development of drylands

Woody leguminous species are valuable crops because of their nutritional, economic, and ecological characteristics. Such crops have aided in the recovery of marginal lands for agricultural development due to their ability to fix nitrogen, control erosion, and act as a refuge for other species, in addition to their capacity to improve soil mineral composition and microbial biodiversity. Nevertheless, some leguminous trees are recognized to be one of the worst invasive species that affect negatively biodiversity and the entire ecosystem balance. In this study, we review new global uses for some woody leguminous crops, highlighting new nutraceutical and pharmacological properties, their uses as bioenergy sources, and their ecological uses for bioremediation opening new possibilities of management. We aim to bring knowledge on the multiple benefits that these woody plants continue to provide to humans from economic, social, and environmental standpoints.     

Effects of Titanium Dioxide Nanoparticles in Different Metabolic Pathways in the Freshwater Microalga <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis> (Trebouxiophyceae)

The products that employ nanoparticles (NPs) in their composition have increased since the beginning of NP production; hence, their availability in the environment, especially in aquatic ecosystems, tends to increase. In these ecosystems, the phytoplankton is immersed in a complex matrix of nutrients, excreted materials, and other chemical compounds, which can influence the metabolic strategy of microalgae. One of the metabolic ways is mixotrophy, a situation whereby microalgae perform photosynthesis and use dissolved organic carbon at the same time. Most toxicity evaluations do not consider such a metabolic route, but this can represent a preferential metabolism in natural environments. The present study aimed at evaluating the effects of NP-TiO₂ at a log concentration range of ??3.10 to 0.89, on photosynthesis, growth, viability, and biochemical composition of the microalgae Chlorella sorokiniana during photoautotrophic and mixotrophic growth (glucose as the organic carbon source). The results showed lower chlorophyll a and photosynthetic activity in mixotrophy than in photoautotrophy, which can be due to a decreased need for photosynthesis in mixotrophy. Photoautotrophy cultures were sensitive to NPs, reaching 39% of viability at log 0.89, while in mixotrophy, cell viability was not affected by NPs. The biochemical composition and cell density changed as a function of NP concentrations, with increase in the protein/carbohydrate ratio in both treatments. The results showed that C. sorokiniana is more resistant to NPs during mixotrophic growth, but with changes in biochemical composition, whereas the photoautotrophic cultures were more sensitive to the increase in NP concentrations.     

Adaptation and Validation of Colorimetric Methods in Determining Ammonium and Nitrate on Tropical Soils

Inorganic nitrogen (N) determination in soil extracts is a useful tool in studying soil–N interactions. The main method used worldwide is the steam distillation, but colorimetric methodologies show advantages of being quick, simple, sensitive, and higher yield. However, they are subject to disruption when the extract has interfering organic N, limiting its application in tropical soil. The aim of this study is to evaluate colorimetric methods for the determination of NH₄⁺ (through Berthelot reaction) and NO₃^? + NO₂^? (through Griess-Ilosvay reaction) in saline extracts of tropical soils by addition of activated charcoal during the extraction process. It is recommended to use extraction solution of 2 mol L^?1 potassium chloride (KCl) and reaction time of 30 min. Validation parameters confirmed the best performance of the colorimetric methods, revealing results favorable to the addition of the activated charcoal in the extraction process to increase the accuracy and precision of the colorimetric methods.     

Application of bioassays with <Emphasis Type="Italic">Enchytraeus crypticus</Emphasis> and <Emphasis Type="Italic">Folsomia candida</Emphasis> to evaluate the toxicity of a metal-contaminated soil,before and after remediation

Purpose  

A contaminated soil was amended to reduce bioavailability of metals (As, Cd, Cu, Pb, and Zn) and to modify its potential environmental impacts. Reproduction toxicity tests using two different soil invertebrates, Enchytraeus crypticus and Folsomia candida, were used to evaluate efficiency of soil amendments to reduce metal availability.