Natural‐Channel‐Design Restorations That Changed Geomorphology Have Little Effect on Macroinvertebrate Communities in Headwater Streams

Stream restorations that increase geomorphic stability can improve habitat quality, which should benefit selected species and local aquatic ecosystems. This assumption is often used to define primary restoration goals; yet, biological responses to restoration are rarely monitored or evaluated methodically. Macroinvertebrate communities were inventoried at 6 study reaches within 5 Catskill Mountain streams between 2002 and 2006 to characterize their responses to natural‐channel‐design (NCD) restoration. Although bank stability increased significantly at most restored reaches, analyses of variation showed that NCD restorations had no significant effect on 15 of 16 macroinvertebrate community metrics. Multidimensional scaling ordination indicated that communities from all reach types within a stream were much more similar to each other within any given year than they were in the same reaches across years or within any type of reach across streams. These findings indicate that source populations and watershed‐scale factors were more important to macroinvertebrate community characteristics than were changes in channel geomorphology associated with NCD restoration. Furthermore, the response of macroinvertebrates to restoration cannot always be used to infer the response of other stream biota to restoration. Thus, a broad perspective is needed to characterize and evaluate the full range of effects that restoration can have on stream ecosystems.     

Spatial changes in carbon and nitrogen stable isotopes of the plankton food web in a saline lake ecosystem

We investigated spatial changes in the isotope ratios of the plankton food web in Lake Chany, Siberia, Russia, especially at an estuarine transition zone of the lake. The δ¹³C values of particulate organic matter (POM) varied among the sampling sites, and increased with increasing pH of the lake water. This may reflect a shift by phytoplankton from using CO₂ to using bicarbonate for photosynthesis with increasing pH. The δ¹³C values of zooplankton community also changed at each site along with those of the POM. This was indicative of carbon isotope changes of plankton food webs between the stations along an environmental gradient.     

Reconstruction of historical productivity using visible-near-infrared (VNIR) reflectance properties from boreal and saline lake sediments

Chlorophylls preserved in lake sediments have been used as a proxy to infer past trophic status. Recently, it has been demonstrated that visible-near-infrared (VNIR) reflectance spectroscopy can provide a rapid and non-destructive estimation of fossil chlorophylls from alpine lake sediments. The present study explores, (a) the applicability of VNIR reflectance spectroscopy to reconstructing historical productivity from boreal and saline lakes, and (b) the ability of an inference model combining all lake types to reconstruct historical chlorophyll concentrations from lake sediments. Results revealed that regardless of the lake type, a common sediment spectral feature of a reflectance trough centered near 675 nm, was observed. Additionally, the amplitude of reflectance in the VNIR region differs within and among lakes depending on their trophic states. The inferred concentration of total chlorophylls and derivatives from sediment spectral properties reflected a recent nutrient enrichment in most of the study lakes. Predicted chlorophyll concentration, when plotted against high-pressure liquid chromatography (HPLC) measured concentration combining all lake types, was found to be statically significant (r ² = 0.80, P < 0.01). Collectively, results from this study indicate that regardless of the lake type, a common chlorophyll absorption feature near 675 nm can be detected, which is associated with contrasting limnological settings and, therefore, can be used as a viable tool to reconstruct paleoproductivity. A similar approach can be implemented for rapid and non-destructive detection of historical lake water quality in a wide range of lake sediments.     

High-temperature tolerance of Artemisia tridentata and Potentilla gracilis under a climate change manipulation

Leaf tolerance to high temperatures, as determined by electrolyte leakage and chlorophyll a fluorescence, was compared for Artemisia tridentata (Asteraceae), a widespread shrub of the Great Basin, Colorado Plateau, and western slope of the Rocky Mountains, and Potentilla gracilis (Rosaceae), a herbaceous forb common to high-elevation meadows of the western United States. Species-specific and treatment-specific differences in leaf temperature, high-temperature tolerance and chlorophyll a fluorescence from photosystem II were compared, to test the hypothesis that plants at ecosystem borders will exhibit species-specific responses to climate change. Measurements were made for plants exposed to a climate change warming manipulation on a major ecosystem border at the Rocky Mountain Biological Laboratory, Colorado, United States, in July and August 1995. In July, daily maximal leaf temperatures were significantly higher for P. gracilis than for A. tridentata. Leaf temperatures were slightly lower in August than July for leaves of both species, on control and heated plots, despite the fact that daily maximum air temperatures were not significantly different for the two months. High-temperature tolerance was determined for leaves treated for 1 h at temperatures ranging from 15°C to 65°C. LT₅₀ was approximately 46°C for both species on control plots, but was 43°C for leaves of both species from heated plots, contrary to the predictions of the hypothesis. No shift in LT₅₀ (acclimation) was apparent between July and August. Changes in chlorophyll a fluorescence from photosystem II (F _V /F _M ) were used to characterize the photosynthetic response to high temperatures. For both A. tridentata and P. gracilis in July, F _V /F _M was about 0.7, but decreased for temperatures above 40°C. The results suggest that plant responses to global warming at ecosystem borders may be influenced by factors other than leaf-level physiological tolerance to elevated temperatures.     

基于物元模型的鄱阳湖生态经济区土地生态安全评价

基于2001-2007年的相关数据,借助物元模型对鄱阳湖生态经济区的土地生态安全状况进行研究.结果表明:2001年鄱阳湖生态经济区土地生态安全状况为较安全状态,2002—2004年处于临界安全状态,2005年下降为不安全状态,2006年后土地生态安全状况有所好转,处于临界安全状态.表明利用物元模型进行区域土地生态安全评价是可行的,具有计算简便、意义明确、评价精度高等优点,为土地生态安全评价提供了另一种途径.     

Regulation of phytoplankton dynamics in a Laurentian Great Lakes estuary

The composition and dynamics of phytoplankton populations were examined in Old Woman Creek estuary, Lake Erie (USA). The centric bacillariophytes,Cyclotella atomus Hust.,Cyclotella meneghiniana Kütz., andAulacoseira alpigena (Grun.) Krammer, and the cryptophytes,Cryptomonas erosa Ehren. andRhodomonas minuta var. nannoplanctonica Skuja, dominated the phytoplankton most of the year. Chlorophytes, euglenophytes, and cyanophytes were observed less frequently. Estuarine and Lake Erie phytoplankton were considered distinct populations; lake taxa were largely confined to the estuary mouth and present only in low biomass. Maxima and minima of estuarine phytoplankton coincided with meteorological and hydrological forcing in the form of rainfall and subsequent storm-water inflows, respectively. Distinct population dynamics between the upper and lower estuary following storm events were attributed to the presence/absence of refugia serving as a source for repopulation by opportunistic taxa, fluctuating light conditions in the water column resulting from influx of particulate matter and resuspension of bottom sediments, and nutrient inputs associated with surface runoff and sub-surface interflow. Additionally, agricultural herbicides introduced by storm-water inflows potentially may affect and/or control the growth and physiological responses of individual taxa.     

Vegetation types and patterns in Senegal based on multivariate analysis of field and NOAA-AVHRR satellite data

Abstract. Woody vegetation was studied in 44 sites in Senegal. Species composition and density were analysed with TWINSPAN and Canonical Correspondence Analysis; 16 vegetation types were defined. A supervised, multispectral and multitemporal classification of day and night, dry season NOAA-AVHRR imagery was used to identify their distribution with a classification accuracy ranging from 60–100%.     

Battling for Ribosomes: Translational Control at the Forefront of the Antiviral Response

In the early stages of infection, gaining control of the cellular protein synthesis machinery including its ribosomes is the ultimate combat objective for a virus. To successfully replicate, viruses unequivocally need to usurp and redeploy this machinery for translation of their own mRNA. In response, the host triggers global shutdown of translation while paradoxically allowing swift synthesis of antiviral proteins as a strategy to limit collateral damage. This fundamental conflict at the level of translational control defines the outcome of infection. As part of this special issue on molecular mechanisms of early virus–host cell interactions, we review the current state of knowledge regarding translational control during viral infection with specific emphasis on protein kinase RNA-activated and mammalian target of rapamycin-mediated mechanisms. We also describe recent technological advances that will allow unprecedented insight into how viruses and host cells battle for ribosomes.     

Taxonomic studies in the Miconieae (Melastomataceae). VII. Miconia howardiana,a new speices from Hispaniola

Miconia howardiana, which is known only from a diverse moist montane forest in the vicinity of Loma Trocha de Pey (or “Monteada Nueva”), the easternmost peak of the Sierra de Baoruco, is described and illustrated. It is compared to phenetically similar (and probably phylogenetically related) species of theMiconia favosa complex, i.e.,M. favosa, M. xenotricha, M. campanensis M. Sintenisii, M. foveolata, andM. pycnoneura. The species of this complex are characterized by bullate leaves with frequently cordate bases and often six secondary veins. Most species also have large berries and flowers, 5-locular ovaries, large inflorescence bracts and bracteoles, and more or less dendritic multicellular hairs.     

Satellite data identify decadal trends in the quality of Pygoscelis penguin chick‐rearing habitat

Pygoscelis penguins are experiencing general population declines in their northernmost range whereas there are reported increases in their southernmost range. These changes are coincident with decadal‐scale trends in remote sensed observations of sea ice concentrations (SIC) and sea surface temperatures (SST) during the chick‐rearing season (austral summer). Using SIC, SST, and bathymetry, we identified separate chick‐rearing niche spaces for the three Pygoscelis penguin species and used a maximum entropy approach (MaxEnt) to spatially and temporally model suitable chick‐rearing habitats in the Southern Ocean. For all Pygoscelis penguin species, the MaxEnt models predict significant changes in the locations of suitable chick‐rearing habitats over the period of 1982–2010. In general, chick‐rearing habitat suitability at specific colony locations agreed with the corresponding increases or decreases in documented population trends over the same time period. These changes were the most pronounced along the West Antarctic Peninsula where there has been a rapid warming event during at least the last 50 years.