Spatial and seasonal variations in the stable carbon isotopic composition of methane in stream sediments of eastern Amazonia

The stable carbon isotopic composition of methane (δ13 C-CH4) gas bubbles formed in the sediments of three Amazonian streams was determined over a 5-yr period. The study sites were two ' 'várzea' floodplain (Açu and Maicá) and one 'terra-firme' (Jamaraquá) streams. The δ 13C of sedimentary organic matter (SOM) from the surrounding vegetation and bottom sediments were also determined. The mean δ13C value of SOM was lower in the terra-firme (-29.6‰) than in the várzea stream (-23.8‰) as a result of less C4 plant deposition in the former. The δ 13C-CH4 values varied systematically both seasonally and spatially among the sites during all 5 yr of the study, in association with changes during hydrologic cycle. Overall, the variation in values of δ 13C-CH4 during the high water phase covered a narrower range of values, -63 to -56‰. Contrastively, during the low water phase the δ 13C-CH4 values for várzea and terra-firme streams are different and are in direct opposition. At this phase, the δ13C-CH4 at terra-firme stream is at least 20‰ depleted of 13C compared to várzea streams. Changes in organic matter sources, water levels and associated microbial degradation processes control the observed seasonal and spatial variations in net stable carbon isotopic composition of methane

Evaluation of different attraction sources and their possible interaction in trapping Rhynchophorus palmarum Avaliacao de diferentes fontes atrativas e suas prov?veis interacoes na captura de Rhynchophorus palmarum

3 ilus. 7 tab. 15 ref.Este experimento fue conducido por EMBRAPA CPATC, Aracaju/SE, Brasil, con el objetivo de evaluar la eficiencia de diferentes fuentes de atracci?n y sus probables interacciones en la captura de adultos de Rhynchophorus palmarum. Las fuentes de atracci?n ca?a de az?car (C), feromona de agregaci?n (F), con y sin cambio de la c?psula cada 3 meses, acetato de etila (A) y melaza (M) fueron evaluadas separadamente, y combinadas de dos en dos y de tres en tres, sumando 12 tratamientos en total. Las tiras atractivas fueron colocadas en trampas confeccionadas con baldes pl?sticos de 50 litros. Las trampas fueron evaluadas y cambiadas de lugar en cada colecta para reducir la influencia del lugar sobre el est?mulo del insecto. Un total de 6365 adultos fueron recolectados durante el per?odo experimental. Los tratamientos T10 y T8 fueron los m?s eficientes en la captura de los insectos con 30,54 por ciento y 19,28 por ciento, respectivamente, del total de adultos recolectados. Utilizados aisladamente, los atractivos no fueron eficientes, sumando apenas 4,76 por ciento de los insectos recolectados, mostrando que la interacci?n de las fuentes atractivas es necesaria para un mayor efecto sin?rgico en la atracci?n de R. palmarum. El n?mero de las capturas en cada tratamiento no fue significativamente diferente en relaci?n con el lugar de captura. Research was carried out by Embrapa Coastal Tableland Research Center, Sergipe, Brazil, to determine the efficiency of different lures and to study their probable interaction in the capture of Rhynchophorus palmarum. The experimental design was completely randomized. The lures were sugar cane (C) aggregation pheromone (F) ethyl acetate (A) and molasses (M), tested alone, and combined in twos and threes, adding up to 12 treatments. Plastic bucket traps (50 liters capacity) were used to catch the adults. Every fifteen days, the traps were changed from site to site to avoid the spot effect on the weevil capture. A total of 6365 adults of R. palmarum were captured during the experimental period. The treatment T10 and T8 were the most efficient ones. They were able to attract 30.54 percent and 19.28 percent, adults, respectively, from total adults captured. When tested alone, the lures showed an efficiency level of 4.76 percent from total captures. This result shows the importance of interaction between lures to promote a synergistic effect on the attraction of R. palmarum adults in the field. The number of adults attracted by each lures was not significantly different among the sites, showing no spot effect on the weevil capture

Population structure and dynamics of the Atlantic mackerel (Scomber scombrus) in the North Atlantic inferred from otolith chemical and shape signatures

The Atlantic mackerel, Scomber scombrus, is an economically important and widely distributed fish species in the North Atlantic, currently considered to comprise two stocks: the North-West Atlantic (NWA) and the North-East Atlantic (NEA). Each stock is composed of different spawning components which involve temporal and spatial movements driven by the environment. Thus, resolving the species population structure and dynamics presents a challenge to scientists. In this study, the stock structure of S. scombrus was evaluated using otolith shape and chemical signatures. One hundred and eighty individuals of the same cohort (age 3), caught between January and February of 2018 from six key locations in the North Atlantic, were used. Individuals were collected from the two spawning components in the NWA stock, the Canadian Northern component (NWA-N) and the US Southern component (NWA-S); and from the three spawning components in the NEA stock, the North Sea (NEA-NS), the Western (NEA-W) and the Southern components (NEA-S), plus, an overlapping area of these last two components, the Bay of Biscay (NEA-BB). Combined otolith signatures fully discriminated the NEA and NWA stocks (100% of reclassification success, indicates distinct population-units) and discriminated the components within each stock with high reclassification percentages (100% and 68% for the overall reclassification of the NWA and NEA components, respectively). These data suggest that NWA stock should be regard as two distinct populationunits for fisheries management purposes, confirms the complex metapopulational structure of the NEA stock, and calls for the need of continuous evaluation of these complex stocks in order to achieve a sustainable exploitation.MARINFO [NORTE-01-0145-FEDER-000035]FCT Foundation for Science and TechnologyPortuguese Foundation for Science and Technology [UIDB/04423/2020, UIDP/04423/2020]info:eu-repo/semantics/publishedVersio