Wolves-coyotes-foxes: a cascade among carnivores

Due to the widespread eradication of large canids and felids, top predators in many terrestrial ecosystems are now medium-sized carnivores such as coyotes. Coyotes have been shown to increase songbird and rodent abundance and diversity by suppressing populations of small carnivores such as domestic cats and foxes. The restoration of gray wolves to many parts of North America, however, could alter this interaction chain. Here we use a 30-year time series of wolf, coyote, and fox relative abundance from the state of Minnesota, USA, to show that wolves suppress coyote populations, which in turn releases foxes from top-down control by coyotes. In contrast to mesopredator release theory, which has often considered the consequence of top predator removal in a three-species interaction chain (e.g., coyote-fox-prey), the presence of the top predator releases the smaller predator in a four-species interaction chain. Thus, heavy predation by abundant small predators might be more similar to the historical ecosystem before top-predator extirpation. The restructuring of predator communities due to the loss or restoration of top predators is likely to alter the size spectrum of heavily consumed prey with important implications for biodiversity and human health.     

A universal approach to estimate biomass and carbon stock in tropical forests using generic allometric models

Allometric equations allow aboveground tree biomass and carbon stock to be estimated from tree size. The allometric scaling theory suggests the existence of a universal power-law relationship between tree biomass and tree diameter with a fixed scaling exponent close to 8/3. In addition, generic empirical models, like Chave's or Brown's models, have been proposed for tropical forests in America and Asia. These generic models have been used to estimate forest biomass and carbon worldwide. However, tree allometry depends on environmental and genetic factors that vary from region to region. Consequently, theoretical models that include too few ecological explicative variables or empirical generic models that have been calibrated at particular sites are unlikely to yield accurate tree biomass estimates at other sites. In this study, we based our analysis on a destructive sample of 481 trees in Madagascar spiny dry and moist forests characterized by a high rate of endemism (> 95%). We show that, among the available generic allometric models, Chave's model including diameter, height, and wood specific gravity as explicative variables for a particular forest type (dry, moist, or wet tropical forest) was the only one that gave accurate tree biomass estimates for Madagascar (R2 > 83%, bias < 6%), with estimates comparable to those obtained with regional allometric models. When biomass allometric models are not available for a given forest site, this result shows that a simple height-diameter allometry is needed to accurately estimate biomass and carbon stock from plot inventories.     

Oxidative and genotoxic effects of bisphenol A on primary gill cell culture of Lake Van Fish (Alburnus tarichi Güldenstädt, 1814)

Lake Van is the largest lake in Turkey. The lake limits lifespan due to its high pH and brackish water. For this reason, only a single species of fish (Van Fish) is living in the lake that has been adapted to these conditions. In the present study, we investigated the total oxidant status (TOS), total antioxidant status (TAS), malondialdehyde (MDA) level and DNA damage effect of bisphenol A (BPA) (10^?7, 10^?6 and 10^?5?M) on primary gill cell culture of Van Fish for 24 and 48?h of incubation periods. TAS levels were not changed when compared to those of the control group, but TOS levels were decreased in both 24 and 48?h. The MDA level increased only at the highest concentration (10^?5) at the end of 12 and 24?h (p?.05). DNA damage increased only at the 10^?5?M concentration after 48?h. At the end of the experiment, BPA exposure caused lipid peroxidation and genotoxic effect. These results indicate that high levels of BPA exposure induced oxidative stress and DNA damage by time- and concentration-dependent fashion in the gill cell culture of Van Fish. Gill cell culture is a useful model for the rapid identification of the harmful effects of chemicals in the aquatic environment.     

Bayesian estimation of species relative abundances and habitat preferences using opportunistic data

We develop a new statistical procedure to monitor relative species abundances and their respective preferences for different habitat types, using opportunistic data. Following Giraud et al. (Biometrics 72(2):649–658, 2015), we combine the opportunistic data with some standardized data in order to correct the bias inherent to the opportunistic data collection. Species observations are modeled by Poisson distributions whose parameters quantify species abundances and habitat preferences, and are estimated using Bayesian computations. Our main contributions are (i) to tackle the bias induced by habitat selection behaviors, (ii) to handle data where the habitat type associated to each observation is unknown, (iii) to estimate probabilities of selection of habitat for the species. As an illustration, we estimate common bird species habitat preferences and abundances in the region of Aquitaine (France).     

肠道微生物群和水生毒理学: 环境健康的新概念

高通量测序技术极大地方便了深度考察不同种群中宿主相关微生物群的组成和功能。研究表明微生物在动物包括人类的健康和疾病发病中扮演着必要的角色。微生物已成为环境毒理学中新兴的重要研究主题。这是因为微生物在免疫系统中起着重要的交互的作用,同时在化学解毒中也有作用。污染物扰动肠道微生物,引起胃肠组织的病理生理变化,导致一系列系统效应,致使营养摄入变差和肠道发炎。本文检索了关于环境污染物对水生物种微生物影响的文献,重点关注了肠道微生物。我们强调了脊柱动物宿主中的一些已知的肠道上皮细胞的主要蛋白,这些均是化合物破坏的靶标,这些蛋白可以与微生物直接对话。我们提出了一个有害结局路径(adverse outcome pathway)的总体框架,将肠道生态失调作为有害效应终点事件的主要贡献因子。我们展示了两个案例研究,分别是(1)纳米材料;(2)碳氢化合物,我们参考了Deepwater Horizon港口的石油泄漏事件, 生态失调在案例中展示了微生物的考察如何改善有害结局的研究。最后,我们提出了一些策略以建立化合物诱导的肠道生态失调与有害结局的关联。我们通过实验建立了特定微生物与肠道生态失调的关联。对毒物与微生物关系的深入研究将成为改善动物及人类健康的重大突破。 精选自Ondrej Adamovsky, Amanda N. Buerger, Alexis M. Wormington, Naomi Ector, Robert J. Griffitt, Joseph H. Bisesi Jr., Christopher J. Martyniuk. The gut microbiome and aquatic toxicology: An emerging concept for environmental health. Environmental Toxicology and Chemistry,2018,37:2758-2775.
详情请见 https://doi.org/10.1002/etc.4249
     

High connectivity among locally adapted populations of a marine fish (Menidia menidia)

Patterns of connectivity are important in understanding the geographic scale of local adaptation in marine populations. While natural selection can lead to local adaptation, high connectivity can diminish the potential for such adaptation to occur. Connectivity, defined as the exchange of individuals among subpopulations, is presumed to be significant in most marine species due to life histories that include widely dispersive stages. However, evidence of local adaptation in marine species, such the Atlantic silverside, Menidia menidia, raises questions concerning the degree of connectivity. We examined geochemical signatures in the otoliths, or ear bones, of adult Atlantic silversides collected in 11 locations along the northeastern coast of the United States from New Jersey to Maine in 2004 and eight locations in 2005 using laser ablation inductively coupled plasma mass spectrometry (ICP-MS) and isotope ratio monitoring mass spectrometry (irm-MS). These signatures were then compared to baseline signatures of juvenile fish of known origin to determine natal origin of these adult fish. We then estimated migration distances and the degree of mixing from these data. In both years, fish generally had the highest probability of originating from the same location in which they were captured (0.01-0.80), but evidence of mixing throughout the sample area was present. Furthermore, adult M. menidia exhibit highly dispersive behavior with some fish migrating over 700 km. The probability of adult fish returning to natal areas differed between years, with the probability being, on average, 0.2 higher in the second year. These findings demonstrate that marine species with largely open populations are capable of local adaptation despite apparently high gene flow.     

Bioengineers and their associated fauna respond differently to the effects of biogeography and upwelling

Temperature and primary production (often linked to nutrient supply) are two of the few factors influencing species diversity and abundances across mesoscale gradients, while at smaller scales the habitat complexity offered by bioengineers is important. Previous studies have illustrated effects of upwelling and biogeography on intertidal bioengineers, but it is not known if these processes influence assemblages associated with those bioengineers in a similar way. We examined the habitat structure offered by two species of mussels and their associated fauna in five regions across 3000 km and three biogeographic provinces of the South African coast, replicating upwelling and non-upwelling areas within each region. Upwelling and region influenced the structure of mussel beds (the density and size of mussels). In contrast, upwelling did not influence mesoscale differences in composition, abundance, and numbers of species of crustaceans, mollusks, or polychaetes in mussel beds. Regardless of trophic level or mode of reproduction, mussel bed fauna were influenced only by region. Regional differences were strongly influenced by biogeography. The associated fauna was, however, also strongly correlated with the structure of the habitats created by mussels. Our results support the importance of upwelling to a critical ecosystem engineer, but show that these effects do not extend directly to the assemblages of associated fauna, which are more influenced by regional-scale effects and biogeography. We suggest that mesoscale patterns in the associated fauna of this bioengineered habitat are driven by the direct effects of biogeography, combined with the influence of biogeography and upwelling on mussel bed structure.     

Heavy metals in fish species from lotic freshwater ecosystem at Afikpo, Nigeria

A study was conducted between March 2006 and February 2007 to assess the concentration of Fe, Zn, Cu, Mn, Pb, and Cr in the gills and muscles of six fish species (Chrysichthys nigrodigitatus, Clarias anguillaris, Tillapia zillii, Mormyrus rume rume, Mormyrus macrophthalmus and Mormyrus tapirus) from lotic freshwater ecosystem at Afikpo South- East Nigeria using Atomic Absorption Spectrophotometer. In all the fish species studied the concentration of metals in the gills was significantly higher than that of the muscles (p<0.05). While the highest concentration (mg l(-1)) of Fe (702.20 +/- 0.04), Zn (34.40 +/- 0.02), Cu (2.10 +/- 0.01), Mn (4.91 +/- 0.08) Pb (0.50 +/- 0.02) and Cr (1.12 +/- 0.07) were recorded in the gills of C. nigrodigitatus, that in the muscles were recorded in T. zillii (443.20 +/- 0.08, 23.30 +/- 0.06, 1.33 +/- 0.06, 3.09 +/- 0.02, 0.31 +/- 0.01 and 0.66 +/- 0.04 for Fe, Zn, Cu, Mn, Pb and Cr respectively). The lowest concentration of all the heavy metals in the gills was recorded in M. tapirus (309.00 +/- 0.07, 16.45 +/- 0.03, 0.92 +/- 0.04, 2.15 +/- 0.04, 0.21 +/- 0.01 and 0.50 +/- 0.06 mg l(-1)for Fe, Zn, Cu Mn, Pb and Cr respectively) while the lowest in the muscles was recorded in C. anguillaris [Fe (186.00 +/- 0.07), Zn (14.20 +/- 0.08), Cu (0.56 +/- 0.03), Mn (1.30 +/- 0.02), Pb (0.10 +/- 0.01) and Cr (0.28 +/- 0.04)]. The order of heavy metals concentrations in both the gills and muscles was Fe>Zn>Mn>Cu>Cr>Pb. While the concentration of Zn, Cu and Pb both in the muscles and gills of all the six fish species studied were within the WHO and FEPA prescribed limits, that of Fe(except in the muscles), Mn and Cr were above the prescribed limits thus indicating contamination of the fish species by these metals. Fe has the highest bio-concentration factor (BCF) in both tissues while the least was Cu. Periodic monitoring of these metals in both fishes and river to ensure safety is advocated.     

In situ removal of arsenic from groundwater by using permeable reactive barriers of organic matter/limestone/zero-valent iron mixtures

In this study, two mixtures of municipal compost, limestone and, optionally, zero-valent iron were assessed in two column experiments on acid mine treatment. The effluent solution was systematically analysed throughout the experiment and precipitates from both columns were withdrawn for scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry analysis and, from the column containing zero-valent iron, solid digestion and sequential extraction analysis. The results showed that waters were cleaned of arsenic, metals and acidity, but chemical and morphological analysis suggested that metal removal was not due predominantly to biogenic sulphide generation but to pH increase, i.e. metal (oxy)hydroxide and carbonate precipitation. Retained arsenic and metal removal were clearly associated to co-precipitation with and/or sorption on iron and aluminum (oxy)hydroxides. An improvement on the arsenic removal efficiency was achieved when the filling mixture contained zero-valent iron. Values of arsenic concentrations were then always below 10 μg/L.     

Trophic ecology of Grey-headed albatrosses from Marion Island, Southern Ocean: insights from stomach contents and diet tracers

During chick-rearing, albatrosses can alternate between long foraging trips that provide the main source of food for the adults and short foraging trips that they use to feed their young. This flexibility in foraging behaviour can lead to differences in diet composition between adults and chicks and implies that they may be vulnerable in different ways to food shortages. The trophic ecology of the Grey-headed albatross Thalassarche chrysostoma was investigated at the sub-Antarctic Prince Edward Islands during the chick-rearing period in April 2006 using a combination of approaches. Diets of adults and chicks were assessed using stable isotope ratios and fatty acid (FA) profiles of blood and/or stomach oils, in addition to stomach contents analysis. Fish from the family Macrouridae and cephalopods (particularly the onychoteuthid Kondakovia longimana) were the primary prey, whereas crustaceans (krill Euphausia superba) represented a smaller proportion of the stomach contents. Stomach oil FA profiles contained more monounsaturated FA than the profiles of plasma, which were richer in saturated FA and arachidonic acid (20:4n-6). There was also a distinct separation of adults from chicks, with higher levels of monounsaturates in chick plasma, and higher saturated FA levels (particularly 16:0) in the adult plasma. Stable carbon isotope ratios of whole blood were similar in adults and chicks, whereas stable nitrogen isotope ratios showed significant enrichment by >1‰ in chicks. The combined FA, stable isotopes and stomach contents analyses suggest clear differences in diet quality between adults and chicks, with chicks feeding at a higher trophic position through feeding more on highly nutritious fish and adults keeping much of the less nutritious zooplankton for themselves.