Pelagic larvae are highly important for maintaining the gene flow among populations of sessile marine invertebrates. Colonial
ascidians consist, exclusively, of brooding species, with lecithotrophic larvae that have a limited dispersal. As a result,
there is a marked differentiation among populations. In this work, we used allozyme electrophoresis to access the genetic
variation in four populations of Symplegma rubra, a colonial ascidian frequently found in the intertidal zone of Southeastern Brazilian coast. High variability was found
at three of the four sites sampled, the exception being Praia Grande in the State of Rio de Janeiro. At this site, there was
a great preponderance of clones, which possibly reflected the enclosed nature of the location and its low water circulation
that reduce the dispersal capabilities of these animals. S. rubra did not conform to expectations for random mating (Hardy–Weinberg equilibrium): there was a deficit of heterozygotes that
was more related to the small population size than to inbreeding processes, since Fis analysis per locus revealed a deficiency of heterozygotes at only one locus—MDH*. The greatest variation in allele frequency was found for GPI-2*. Analyses of genetic variability revealed moderate differentiation among the populations (FST=0.051), which was unexpected for a species with a low dispersal capability. Rafting, a frequently underestimated means of
dispersal, may be the main mode of gene flow in this species over large areas, since colonies of S. rubra are frequently seen growing on drift material and there is no evidence that the larva survive for a long time in the plankton. 相似文献
In addition to direct photolysis studies, in this work the second-order reaction rate constants of pesticides imidacloprid (IMD) and ametryn (AMT) with hydroxyl radicals (HO●), singlet oxygen (1O2), and triplet excited states of chromophoric dissolved organic matter (3CDOM*) were determined by kinetic competition under sunlight. IMD and AMT exhibited low photolysis quantum yields: (1.23?±?0.07)?×?10–2 and (7.99?±?1.61)?×?10–3 mol Einstein?1, respectively. In contrast, reactions with HO● radicals and 3CDOM* dominate their degradation, with 1O2 exhibiting rates three to five orders of magnitude lower. The values of kIMD,HO● and kAMT,HO● were (3.51?±?0.06)?×?109 and (4.97?±?0.37)?×?109 L mol?1 s?1, respectively, while different rate constants were obtained using anthraquinone-2-sulfonate (AQ2S) or 4-carboxybenzophenone (CBBP) as CDOM proxies. For IMD this difference was significant, with kIMD,3AQ2S*?=?(1.02?±?0.08)?×?109 L mol?1 s?1 and kIMD,3CBBP*?=?(3.17?±?0.14)?×?108 L mol?1 s?1; on the contrary, the values found for AMT are close, kAMT,3AQ2S*?=?(8.13?±?0.35)?×?108 L mol?1 s?1 and kAMT,3CBBP*?=?(7.75?±?0.80)?×?108 L mol?1 s?1. Based on these results, mathematical simulations performed with the APEX model for typical levels of water constituents (NO3?, NO2?, CO32?, TOC, pH) indicate that the half-lives of these pesticides should vary between 24.1 and 18.8 days in the waters of the Paranapanema River (São Paulo, Brazil), which can therefore be impacted by intensive agricultural activity in the region.
Environmental Science and Pollution Research - One of the most widely used antibiotics is amoxicillin (AMX), which is the most widely used in humans and animals, but it is discharged metabolically... 相似文献
Environmental Science and Pollution Research - Pesticides have been used to kill pests such as insects, fungi, rodents, and unwanted plants. Since these compounds are potentially toxic to the... 相似文献
Environmental Science and Pollution Research - Microplastics (MPs) correspond to plastics between 0.1 μm and 5 mm in diameter, and these can be intentionally manufactured to be microscopic or... 相似文献
Journal of Polymers and the Environment - The objective of this study was to obtain and characterize Nerol essential oil encapsulated in PCL. The miniemulsion and solvent evaporation method was... 相似文献
Invasion by alien species is one of the most critical factors affecting global biodiversity, leading to homogenization and species loss worldwide. Jackfruit (Artocarpus heterophyllus Lam., Moraceae) is one of the most conspicuous invasive plants in Brazil. We studied jackfruit invasion in the Atlantic Forest in Ilha Grande State Park, located on an island (Ilha Grande), by assessing jackfruit distribution and density along 23 trails (90 km). Presence or absence was verified in a total of 857 plots. Data showed that jackfruit is spread all over Ilha Grande, and that plant density varied significantly along and between trails. Jackfruit was registered as the dominant tree species on some of the trails. Control by park managers is an urgent need in order to ensure the conservation of local biodiversity. A decision key for jackfruit management according to jackfruit density, age class and slope is provided. 相似文献
Previous studies in the Douro River estuary, based on occasional sampling, showed the presence of several estrogenic disrupting chemicals (EDCs). In sequence, we hypothesized that such type of pollution was more likely an enduring issue than an occasional phenomenon, and that it may even affect recreational beaches in each side of the estuarine mouth. Thus to conclude about the continuous influx of EDCs, water samples were taken twice a day, once per a week, from March to May of 2009, at four sites within the estuary and at two sites in the coastline. After solid-phase extraction, the extracts were prepared for GC-MS analysis of 11 reference EDCs. These embraced natural and pharmaceutical estrogens (17β-estradiol, estrone and 17α-ethynylestradiol) and xenoestrogenic industrial pollutants (4-octylphenol, 4-nonylphenol, and their mono and diethoxylates and bisphenol A). Data showed the ubiquitous presence of potentially hazardous amounts of natural estrogens (particularly of estradiol, ca 5.5?ng?L?1) and persistent organic pollutants such as nonylphenol mono (up to 550?ng?L?1) and diethoxylate (up to 2000?ng?L?1). It was concluded that the targeted area is continuously polluted by the assayed EDCs, and as a consequence, conditions exist for endocrine disturbance in the biota by chronic exposure to EDCs. 相似文献
A photocatalyst based on CuO/SiO2 was prepared, and evaluated for the degradation of methylene blue in aqueous medium. The photocatalyst was obtained by calcination
method of copper salt, in the presence of silica. The characterization by XRD, FTIR, and TPR techniques confirmed the formation
of CuO as active phase. SEM studies showed CuO deposited on the surface of SiO2. By ESI-MS, it was demonstrated that the degradation of methylene blue occurs through successive hydroxylations. Photodegradation
assays showed that CuO/SiO2 was efficient for degradation, and that the material worked better in the presence of UV light. 相似文献
This paper details a case study of economic and natural system responses to alternative water management policies in the Cache La Poudre River basin, Colorado, 1980–1994. The case study is presented to highlight the value and application of a conceptual integration of economic, salmonid population, physical habitat, and water allocation models. Five alternative regimes, all intended to increase low winter flows, were investigated. Habitat enhancements created by alternative regimes were translated to population responses and economic benefits. Analysis concluded that instream flows cannot compete on the northern Colorado water rental market; cooperative agreements offer an economically feasible way to enhance instream flows; and establishing an instream flow program on the Cache La Poudre River mainstem is a potentially profitable opportunity. The alliance of models is a dynamic multidisciplinary tool for use in professional settings and offers valuable insight for decision-making processes involved in water management. 相似文献