Ecology of bacterial endophytes associated with wetland plants growing in textile effluent for pollutant-degradation and plant growth-promotion potentials

In this study, 41 culturable endophytic bacteria were isolated from the roots and shoots of three wetland plants, Typha domingensis, Pistia stratiotes and Eichhornia crassipes, and identified by 16S rRNA gene sequencing. Textile effluent-degrading and plant growth-promoting activities of these endophytes were determined. The analysis of endophytic bacterial communities indicated that plant species had a pronounced effect on endophytic bacterial association and maximum endophytes (56.5%) were associated with T. domingensis. These endophytic bacteria mainly belonged to different species of the genera Bacillus (39%), Microbacterium (12%) and Halomonas (12%). Eight of the 41 strains showing maximum efficiency of textile effluent degradation also exhibited plant growth-promoting activities such as production of indole-3-acetic acid and siderophore, presence of 1-amino-cyclopropane-1-carboxylic acid deaminase, and solubilization of inorganic phosphorous. This is the first study describing the diversity and plant-beneficial characteristics of the textile effluent-degrading endophytic bacteria associated with wetland plants. T. domingensis showed better growth in textile effluent and also hosted maximum number of endophytic bacteria in roots and shoots. The interactions between T. domingensis and its associated endophytic bacteria could be exploited to enhance the efficiency of constructed wetlands during the remediation of industrial effluent.     

Enhanced degradation of phenol in floating treatment wetlands by plant-bacterial synergism

Phenol is a commonly found organic pollutant in industrial wastewaters. Its ecotoxicological significance is well known and, therefore, the compound is often required to be removed prior to discharge. In this study, plant-bacterial synergism was established in floating treatment wetlands (FTWs) in an attempt to maximize the removal of phenol from contaminated water. A common wetland plant, Typha domingensis, was vegetated on a floating mat and augmented with three phenol-degrading bacterial strains, Acinetobacter lwofii ACRH76, Bacillus cereus LORH97, and Pseudomonas sp. LCRH90, to develop FTWs for the remediation of water contaminated with phenol. All of the strains are known to have phenol-reducing properties, and grow well in FTWs. Results showed that T. domingensis was able to remove a small amount of phenol from the contaminated water; however, bacterial augmentation enhanced the removal potential significantly, i.e., 0.146 g/m²/day vs. 0.166 g/m²/day, respectively. Plant biomass also increased in the presence of bacterial consortia; and inoculated bacteria displayed successful colonization/survival in the rhizosphere, root interior and shoot interior of the plant. Similarly, highest reduction in chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and total organic carbon (TOC) was achieved by the combined application of plants and bacteria. The study demonstrates that the plant-bacterial synergism in a FTW may be a more effective approach for the remediation of phenol-contaminated water.     

Effects of wetland connectivity on overwintering and movement behaviours of Australian freshwater turtles

Freshwater turtles are important consumers in Australian freshwater ecosystems. They serve as scavengers, nutrient regulators, and as food sources and Totems for Traditional Owners throughout Australia. Despite their importance, most Australian freshwater turtle species are declining. The impact of winter wetland drying on turtle populations remains unknown, and winter exposure of hibernating turtles may be an important additional source of mortality. We aimed to examine turtle responses to seasonal and episodic wetland drying in wetlands using acoustic telemetry and active trapping. Wetlands were chosen that spanned a range of hydrological connectivity to the adjacent Edward/Kolety-Wakool River. We found that tagged Emydura macquarii typically exit wetlands disconnected from the adjacent permanent river prior to winter, and overwinter in the river. Female E. macquarii rapidly re-entered ‘home’ wetlands (wetlands in which they were initially tagged) the following spring, whereas males tended to leave the study area, returning occasionally. Although we were not able to evaluate a winter drying event, one of the wetlands experienced partial summer drying. All three local turtle species (E. macquarii, Chelodina expansa, C. longicollis) exited the wetland long before winter drying would have become a potential threat. Our results suggest that turtles in this system may be protected from winter wetland drying because they move to the adjacent permanent river prior to winter. Spending the winter in the river channel reduces the risks of being trapped in a drying wetland as temperatures drop in winter.     

考洲洋人工种植红树林湿地大型底栖动物群落环境响应

2017年以来,广东省惠州市在考洲洋潮间带开展了大规模人工种植红树林生态修复工程,但考洲洋人工种植红树林湿地大型底栖动物群落的环境响应未见报道。根据2018-2019年四个季节在考洲洋盐洲大桥附近红树种植1-2年（X断面）和5-6年（Y断面）的两处湿地的大型底栖动物定量取样数据,分析了人工红树林湿地大型底栖动物的时空格局及其环境响应。方差分析表明,Y断面冬季的大型底栖动物群落的物种数、栖息密度、生物量、多样性指数（H''）和丰富度指数（d）,以及夏季的栖息密度均随潮高（海平面高程）降低而增加;而Y断面冬季的均匀度指数（J）、夏季的H''和J则是随潮高降低而减少。聚类（Cluster）和非度量多维尺度（nMDS）分析表明冬季和夏季X断面和Y断面大型底栖动物群落相似性较低,而春季和秋季X断面和Y断面大型底栖动物群落相似性较高。冬季和夏季最大潮高、潮差、大型底栖动物物种数、栖息密度、H''和d较春季和秋季的高。红树种植1-2年的X断面大型底栖动物物种数、H''和J低于种植5-6年的Y断面。上述结果证实潮汐和红树种植年限影响考洲洋红树林湿地大型底栖动物的群落结构,研究结果可为大型底栖动物多样性保护和生态修复提供基础资料。     

Hydrologic,vegetation, and substrate characteristics of floating marshes in sediment-rich wetlands of the Mississippi river delta plain,Louisiana, USA

Floating marshes occur over 70% of the western Terrebonne Basin, Louisiana, USA, freshwater coastal wetlands. They are of several types: A free-floating thick-mat (45–60 cm) marsh dominated by Panicum hemitomon and Sagittaria lancifolia; a thick mat marsh dominated by Panicum hemitomon and Sagittaria lancifolia that floats part of the year, but whose vertical floating range is damped compared to adjacent water; and an irregularly-floating thin mat (< 30 cm) dominated by Eleocharis spp. in the spring and Ludwigia leptocarpa and Bidens laevis in the summer and fall. Floating mats must be almost entirely organic in order to be buoyant enough to float. The western Terrebonne wetlands receive large winter/spring supplies of suspended sediments from the Atchafalaya River. Even though sediment concentrations in the adjacent bayou are as high as 100 mg l^–1, the Panicum hemitomon/Sagittaria lancifolia free-floating marsh probably receives no over-surface sediments since it floats continuously. The bulk density data of the damped-floating marsh, however, suggest some mineral sediment input, probably during winter when this marsh is submerged. These two types of floating marsh could not have developed in the present sediment regime of the Atchafalaya River, but as long as they remain floating can continue to exist. Thin floating mats are found in areas receiving the least sediment (<20 mg 1^–1 suspended sediment concentration in adjacent bayous). This low sediment environment probably made possible their formation within the past 20 years. They may represent a transitional stage in mat succession from (1) existing thick-mat floating marsh to a degrading floating marsh, or (2) a floating marsh developing in shallow open water.Corresponding editor: D. Whigham     

Dynamics of <Emphasis Type="Italic">Typha domingensis</Emphasis> spread in <Emphasis Type="Italic">Eleocharis</Emphasis> dominated oligotrophic tropical wetlands following nutrient enrichment

Recent agricultural intensification in tropical countries has led to increased nutrient input and eutrophication of wetland ecosystems. Higher nutrient levels often lead to changes of vegetation structure and, eventually, shift in species dominance and loss of ecosystem services. We studied the dynamics of species shift in a manipulative nutrient enrichment experiment (+N, +P, +N&P) in oligotrophic wetlands of northern Belize distributed along a salinity gradient. We monitored spread and biomass accumulation of an introduced single individual of Typha domingensis within a 4 years period. The focus was on speed of the spreading and the relative importance of neighbouring ramets in this process. Large differences were found between control and N addition plots versus P and N&P addition plots. The ramets planted in control and N plots died or barely survived, while ramets in P and N&P plots grew vigorously and almost completely outcompeted original vegetation represented by Eleocharis spp. Final numbers of ramets were 2 and 576 per 100 m² for control and N versus P and N&P plots. The filling dynamics of P-enriched plots of differing salinity changed in time. The spreading was delayed in low salinity plots compared to high and medium salinity plots, although it finally reached comparable rates and values. We attribute this delay to originally denser vegetation and less suitable soil conditions in low salinity plots than to a direct salinity effect. Eventually, the number of ramets stabilized and often even decreased, probably due to self-thinning. Spatiotemporal model extrapolating observed vegetative spread suggested that in P-enriched conditions, a clone originating from a single individual is able to cover 1 ha plot completely within 9 years. We conclude that P-enrichment strongly increases the possibility of fast takeover of Belizean wetlands by Typha domingensis. Eventually, such species change can highly increase potential larval habitat for malaria transmitting mosquitoes.     

Transpiration and stomatal conductance of two wetland macrophytes (Cladium jamaicense and Typha domingensis) in the subtropical Everglades

In the subtropical Everglades, greater than 85% of water input through atmospheric precipitation, the primary source of water to the ecosystem, is lost through evapotranspiration (ET). Two dominant macrophytes that could influence ET rates through transpiration and stomatal control were investigated in a field study: Cladium jamaicense, presently the species with the greatest distribution (65%–70%); and Typha domingensis, a species increasing in distribution due to eutrophication and hydrological modifications to the ecosystem. Transpiration rates and stomatal conductance of the two species were compared at eutrophic, mesotrophic, and oligotrophic sites throughout an annual wet and dry season of subtropical Florida. Typha domingensis possessed higher transpiration and conductance rates (>; 11 mmol m^-2 sec^-1) than C. jamaicense (<;7 mmol m^-2 sec^-1; P <; 0.01), during the winter and spring months when ambient temperatures and vapor pressure were at a minimum. However, rates for the two species converged and were not significantly different during the summer and fall months. Stomatal conductance of C. jamaicense remained constant over the range of ambient vapor pressures, but significantly increased in T. domingensis with decreasing vapor pressure. Vapor pressure and light were the best predictors of seasonal and diurnal transpiration rates of T. domingensis, whereas temperature explained the most variability in C. jamaicense. Annual transpiration rates for both species were 1 to 2 mmol m^-2 sec^-1 greater at the eutrophic site than at the transitional and oligotrophic sites. Leaf area increased six times in C. jamaicense and twofold in T. domingensis from the control to nutrient-enriched sites. Results at the leaf scale suggest vegetation shifts and nutrient enrichment have the potential to alter water balances in the Everglades. However, canopy level studies may be necessary to support these conclusions when applied to the larger ecosystem or regional scale.     

Effects of an African grass invasion on vegetation,soil and interstitial water characteristics in a tropical freshwater marsh in La Mancha,Veracruz (Mexico)

Abstract

The transformation of freshwater wetlands to pastures is a common practice in Mexico. This rapid loss of wetlands contrasts with the scarce information that exists about these ecosystems. To identify the environmental factors that control vegetation structure of a freshwater wetland invaded by the African grass Echinochloa pyramidalis, we characterized the vegetation (species composition, cover and aerial biomass), soil (moisture, redox potential, bulk density and topography) and water (water depth level, electric conductivity and pH) in two seasons of the year (dry and rainy). In addition, we analyzed the soil and water of three vegetation areas in the wetland, one dominated by E. pyramidalis, another by Sagittaria lancifolia and a third by Typha domingensis. The parameters associated with the hydrology of the wetland (water level, soil moisture, redox potential and bulk density) explained the plant species distribution. The invasive grass dominated in the relatively drier areas in the wetland while native species such as S. lancifolia, T. domingensis and Pontederia sagitatta dominated wetter sites. Introduction of E. pyramidalis has caused negative changes in the wetland, in particular a decrease of the diversity of plant species. In addition, we believe that the invader grass, as a C4 species, has more efficient use of water than the native plants, as well as a larger biomass, characteristics that can change the hydrological pattern of this wetland.     

Nutrient-limited productivity of calcareous versus fleshy macroalgae in a eutrophic,carbonate-rich tropical marine environment

The results of a study of nutrient enrichment with nitrogen (N) and phosphorus (P) on productivity and calcification of fleshy and calcareous algae are reported in this study. Plants were collected from a nearshore eutrophic site in the Florida Keys (USA) and experimentally pulsed during the night with combinations of N and P. After several days of pulsing (7–10 days), net productivity, calcification, and alkaline phosphatase activity (APA), were measured. Productivity of fleshy algae were frequently enhanced by N, P, and N+P, during both summer and winter. Phosphorus limited the productivity of Hydroclathrus clathratus during winter and Ulva spp. during summer, whereas nitrogen limited the productivity of Laurencia intricata during both seasons. During summer, Dictyota cervicornis productivity was not enhanced by any nutrient enrichment. Nitrogen limited the productivity of the three calcareous species Penicillus capitatus, Penicillus dumetosus and Halimeda opuntia during winter and that of H. opuntia during summer. Neither N nor P enrichment increased calcification of calcareous species, and P enrichment greatly inhibited calcification of P. dumetosus during winter. Nutrient enrichment enhanced the productivity of the fleshy species to a greater extent than that of calcareous algae. The seawater DIN:SRP molar ratio was low at our eutrophic study site (molar ratio average of 3:1 during winter and 9:1 during summer) compared to more oligotrophic sites in the Florida Keys, suggesting that in carbonate-rich environments, eutrophication shifts nutrient regulation of productivity from P to N. APA activities of fleshy macroalage were higher than calcareous algae, and rates of all macro algae were 2- to 7-fold higher in summer compared to winter. Productivity was also about 3-fold higher in fleshy compared to calcareous species and about 2-fold higher in summer compared to winter. These results suggest that nutrient enrichment enhances productivity of fleshy algae to a greater extent than that of calcareous algae. Thus, overgrowth of calcareous algae by more opportunistic fleshy forms could reduce carbonate accretion in tropical coastlines experiencing increased eutrophication.     

Phragmites australis makes valuable floating mat biotopes under oligotrophic conditions

To understand the mechanism of how Phragmites australis makes valuable floating mat biotopes under oligotrophic conditions, we investigated the environmental (water chemistry) and vegetational characteristics (growth, plant species richness, and floristic composition) of a floating mat consisting of three main mat-forming species with a zonal distribution (P. australis on the land side of the floating mat, Zizania latifolia on the middle area, and Typha angustifolia on the water side). Although they showed relatively low growth in the floating mat, compared to those in land-based wetlands, P. australis grew better than other mat-forming species in terms of shoot height and biomass production. Specifically, P. australis made more below-ground parts (593?±?38 g/m²) than other mat-forming species (Z. latifolia, 100?±?10 g/m²; T. angustifolia, 167?±?8 g/m²) and more companion species were found in P. australis-dominated plots (8.5?±?1.0 species/m²) than other plots (Z. latifolia-dominated plots, 2.7?±?0.6 species/m²; T. angustifolia-dominated plots, 1.0?±?0.0 species/m²). The larger amount of below-ground P. australis parts could contribute to thicker and denser mat structures, possibly providing more favorable habitats for neighboring plant species, thus facilitating more companion species within the P. australis-dominated area of the mat.

     

Temperature influences on root growth for Encelia farinosa (Asteraceae), Pleuraphis rigida (Poaceae), and Agave deserti (Agavaceae) under current and doubled CO2 concentrations

To help evaluate root distribution patterns, elongation rates of individual roots were measured as a function of soil temperature for Encelia farinosa (a C₃ species), Pleuraphis rigida (C₄), and Agave deserti (CAM), sympatric codominants in the northwestern Sonoran Desert. Measurements were made at current and doubled CO₂ concentrations under winter and summer conditions of air temperature (day/night temperatures of 17 C/10 C and 33 C/22 C, respectively). The three species had different optimal temperatures for root elongation (T_opt) under winter conditions (25 C for E. farinosa, 35 C for P. rigida, and 30 C for A. deserti); T_opt increased by 2-3 C under summer conditions for all three species. The limiting temperatures for elongation also acclimated from winter to summer conditions. The rate of root elongation at T_opt was higher under summer than winter conditions for E. farinosa (9 vs. 6 mm d⁻¹) and P. rigida (20 vs. 14 mm d⁻¹), reflecting conditions for maximum photosynthesis; no difference occurred for A. deserti (9 vs. 10 mm d⁻¹). Decreased elongation rates at extreme temperatures were associated with less cell division and reduced cell extension. The doubled CO₂ concentration increased average daily root elongation rates for A. deserti under both winter (7%) and summer (12%) conditions, reflecting increased cell extension, but had no effect for the other two species. Simulations of root elongation as a function of soil temperatures showed that maximum elongation would occur at different depths (16-20 cm for E. farinosa, 4-8 cm for P. rigida, and 0-4 cm for A. deserti) and during different seasons (winter to spring for E. farinosa, spring to summer for P. rigida, and all year for A. deserti), contributing to their niche separation. Shading of the soil surface moderated daily variations in soil temperature, reducing seasonal root elongation for winter and spring and increasing elongation for summer. Shading also altered root distribution patterns, e.g., optimal rooting depth for A. deserti and especially P. rigida increased for a hot summer day.     

Riparian leaf litter decomposition on pond bottom after a retention on floating vegetation

Allochthonous (e.g., riparian) plant litter is among the organic matter resources that are important for wetland ecosystems. A compact canopy of free‐floating vegetation on the water surface may allow for riparian litter to remain on it for a period of time before sinking to the bottom. Thus, we hypothesized that canopy of free‐floating vegetation may slow decomposition processes in wetlands. To test the hypothesis that the retention of riparian leaf litter on the free‐floating vegetation in wetlands affects their subsequent decomposition on the bottom of wetlands, a 50‐day in situ decomposition experiment was performed in a wetland pond in subtropical China, in which litter bags of single species with fine (0.5 mm) or coarse (2.0 mm) mesh sizes were placed on free‐floating vegetation (dominated by Eichhornia crassipes, Lemna minor, and Salvinia molesta) for 25 days and then moved to the pond bottom for another 25 days or remained on the pond bottom for 50 days. The leaf litter was collected from three riparian species, that is, Cinnamomum camphora, Diospyros kaki, and Phyllostachys propinqua. The retention of riparian leaf litter on free‐floating vegetation had significant negative effect on the carbon loss, marginal negative effects on the mass loss, and no effect on the nitrogen loss from leaf litter, partially supporting the hypothesis. Similarly, the mass and carbon losses from leaf litter decomposing on the pond bottom for the first 25 days of the experiment were greater than those from the litter decomposing on free‐floating vegetation. Our results highlight that in wetlands, free‐floating vegetation could play a vital role in litter decomposition, which is linked to the regulation of nutrient cycling in ecosystems.     

Breeding biology of Tenagomysis tasmaniae Fenton,Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea: Mysidacea)

The number, size and developmental stage of young in the brood pouch of female Tenagomysis tasmaniae, Anisomysis mixta australis and Paramesopodopsis rufa was recorded throughout the year. Breeding was intensive from spring till the end of autumn for the three species. Calculation of the egg ratio for each species showed that their major reproductive peaks occurred during spring and summer. A winter depression in the breeding cycle was observed for T. tasmaniae and P. rufa, but A. mixta australis ceased breeding during winter. Seasonal variation in the length of gravid females and number of young carried was evident for these three species. Females were longer in spring and summer and carried more young than in autumn and winter. A linear relationship between female length and brood size was demonstrated for each species; annual and seasonal equations were calculated for females carrying each developmental stage. The seasonal equations showed that for a female of given length fecundity was greater during spring than any other season. Natality was estimated to be highest during late spring, summer and early autumn for the three species. No seasonal variation in the size of eggs was evident for the three species. The reproduction pattern of T. tasmaniae, A. mixta australis and P. rufa appears to be very similar to that reported for the majority of iteroparous coastal temperate mysids throughout the world.     

Plants used in constructed wetlands with horizontal subsurface flow: a review

The presence of macrophytes is one of the most conspicuous features of wetlands and their presence distinguishes constructed wetlands from unplanted soil filters or lagoons. The macrophytes growing in constructed wetlands have several properties in relation to the treatment process that make them an essential component of the design. However, only several roles of macrophytes apply to constructed wetlands with horizontal subsurface flow (HF CWs). The plants used in HF CWs designed for wastewater treatment should therefore: (1) be tolerant of high organic and nutrient loadings, (2) have rich belowground organs (i.e. roots and rhizomes) in order to provide substrate for attached bacteria and oxygenation (even very limited) of areas adjacent to roots and rhizomes and (3) have high aboveground biomass for winter insulation in cold and temperate regions and for nutrient removal via harvesting. The comparison of treatment efficiency of vegetated HF CWs and unplanted filters is not unanimous but most studies have shown that systems with plants achieve higher treatment efficiency. The vegetation has mostly a positive effect, i.e. supports higher treatment efficiency, for organics and nutrients like nitrogen and phosphorus. By far the most frequently used plant around the globe is Phragmites australis (Common reed). Species of the genera Typha (latifolia, angustifolia, domingensis, orientalis and glauca) and Scirpus (e.g. lacustris, validus, californicus and acutus) spp. are other commonly used species. In many countries, and especially in the tropics and subtropics, local plants including ornamental species are used for HF CWs.     

Microhabitat Association of Blanding's Turtles in Natural and Constructed Wetlands in Southeastern New York

ABSTRACT We studied Blanding's turtle (Emydoidea blandingii) microhabitat in natural wetlands and wetlands constructed for the turtles in Dutchess County, New York, USA. Investigation of these topics can provide information on ways to increase the extent of Blanding's turtle habitat, improve its quality, and assure that conservation or restoration managers do not overlook key habitat characteristics. Microhabitat was determined by radiotracking individuals to their exact locations and recording habitat variables. Blanding's turtles were associated with shallow water depths (x̄ = 30 cm), muck substrates, and areas of abundant vegetation (total cover xM = 87%). Buttonbush (Cephalanthus occidentalis)had the greatest mean total cover (29%). In the constructed wetlands, Blanding's turtles were associated with significantly less cover and warmer water than in the natural wetlands. Blanding's turtles appeared to be using the constructed wetlands to bask and forage in the spring and early summer but moved to deeper wetlands in late summer when the constructed wetlands dried up or became too warm. For Blanding's turtles, new habitat should contain abundant emergent vegetation (including buttonbush in Dutchess County and other areas where the turtles are known to use buttonbush swamps), basking areas, muck, floating plant material, and submerged aquatic vegetation. Blanding's turtle's use of constructed wetlands highlights the value of a complex of connected wetland habitats in providing for the varied needs of the turtle.     

Constraints of Seed Bank Species Composition and Water Depth for Restoring Vegetation in the Florida Everglades, U.S.A.

The Rotenberger Wildlife Management Area (RWMA) is a northern Everglades marsh, in Florida, U.S.A., that will undergo hydrologic restoration to remedy an artificially shortened hydroperiod. In an effort to predict vegetation responses to the impending changes in hydrology, plant community development from the resident seed bank was observed in response to three different moisture regimes in March and September 1998. Percent cover, species densities, total seedling densities, and percentages of facultative, facultative‐upland, and upland indicator species were significantly higher in moist than in saturated soils. Flooding inhibited the germination of all species except Typha domingensis (cattail), which emerged in the highest numbers from saturated soils in both assays. Lythrum alatum (purple loosestrife) was abundant in both saturated and moist conditions. The season of assay affected species densities and the communities. Percent facultative‐wetland species increased in saturated soils in the March assay but not in September. In contrast, percent obligate hydrophytes were higher in saturated conditions only in the September assay. In general the assay communities bore little resemblance to vegetation in currently undisturbed or historic wetlands of the northern Everglades. Consequently the RWMA seed bank will contribute little to the development of a restored community. Moreover, rehydration may encourage the spread of undesirable hydrophytes such as T. domingensis. This study supports the contention that hydrologic restoration must be accompanied by some level of active vegetation management and that the reference condition cannot be attained passively.     

Population dynamics of the cattle tick Rhipicephalus (Boophilus) microplus in a subtropical subhumid region of Argentina for use in the design of control strategies

The population dynamics of Rhipicephalus microplus (Ixodida: Ixodidae) in northwest Argentina was analysed to support the design of strategic methods for its control. Both parasitic and non‐parasitic phases were studied. The seasonal activity of R. microplus in its parasitic phase was characterized by three peaks in abundance: the first in mid–late spring; the second in summer, and the third in autumn. The non‐parasitic phase of R. microplus was characterized by a long total non‐parasitic period observed after exposures of females from mid‐summer to early autumn, a short total non‐parasitic period observed after exposures of females from late winter to late spring, a short period of larval longevity in early and mid‐summer, and no hatch of the eggs produced by females exposed in mid‐ and late autumn and winter. Treatments of cattle administered during the period from late winter to late spring will act on small cohorts of R. microplus, preventing the emergence of larger generations in summer and autumn. A 17‐week spelling period starting in late spring and early summer will be necessary to achieve optimal control of R. microplus free‐living larvae. If spelling begins in mid‐ or late summer or in autumn, the required period will be 26–27 weeks.     

Seasonal variation in the activity of selected antioxidant enzymes and malondialdehyde level in worker honey bees

The recent decline in managed honey bee populations, Apis mellifera L. (Hymenoptera: Apidae), has caused scientific, ecological, and economic concern. Research into the formation of reactive oxygen species (ROS), antioxidative defense mechanisms, and oxidative stress can contribute to our understanding of bee survival and conservation of this species. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione S‐transferase (GST) enzymes together with levels of malondialdehyde (MDA) were measured in summer and winter honey bees sampled from three colonies. One colony was stationary (C1), entering the winter period having accumulated Robinia pseudoacacia L. (Fabaceae) honey, and two were migratory (C2 and C3), entering the winter period with mainly Tilia (Malvaceae) and Brassica (Brassicaceae) honey, respectively. Compared to summer workers, winter worker bees had decreased SOD and GST activity, and MDA level, whereas CAT activity increased in all three colonies. We also demonstrated that seasonality is the main factor responsible for changes in antioxidant enzymes and MDA levels in worker honey bees. Overall, our results indicate a difference between summer and winter worker bees, pointing at a reduced level of antioxidant enzyme defenses during overwintering which may be due to a decrease in production of ROS. The decreased levels of MDA measured in winter honey bees confirm this. As ROS are actively used by insects as a defense mechanism to fight pathogens, we suggest that reduced production of ROS contributes to higher susceptibility of winter honey bees to infections and reduced overwinter survival.     

Population dynamics of Mus minutoides and Steatomys pratensis (Muridae: Rodentia) in a subtropical grasslandin Swaziland

The population dynamics of Mus minutoides and Steatomys pratensis are virtually unknown. These two species were live-trapped over a 12-month period in a subtropical grassland in Swaziland. Numbers of M. minutoides were relatively high in winter, declined in spring and the population disappeared in summer and autumn. By contrast, numbers of S. pratensis increased gradually from winter to summer and reached a peak in autumn. There were no differences between the mean weights of male and female M. minutoides and S. pratensis. There were, however, seasonal differences in the mean weight of male S. pratensis, with highest weights recorded in summer. Individuals of both species came into breeding condition in spring (October–November). Reproduction had ceased by the end of autumn (April–May). Monthly survival rates of M. minutoides were highest in winter, but did not vary seasonally in S. pratensis. Burning had a pronounced effect on the distribution of S. pratensis. Steatomys pratensis individuals selected recently burnt but revegetated areas over unburnt areas. The effect of burning on the M. minutoides population is difficult to assess, as this species disappeared shortly after the fire.     

长苞香蒲对人工盐碱湿地Na+和K+的吸收与转运特征

为揭示长苞香蒲(Typha domingensis)对盐生湿地生态系统中Na⁺和K⁺的吸收与转运特征,探讨长苞香蒲对盐生湿地的生态修复效果,该研究采用人工模拟盐生湿地的方法,设置CK(对照)、T1(浇灌100 mmol·L^-1盐水)、T2(浇灌200 mmol·L^-1盐水)及T3(浇灌300 mmol·L^-1盐水)4种不同盐浓度的人工湿地生态系统,并分别于5月5日(开始盐胁迫处理,S0)、5月30日(S1)、6月30日(S2)和7月30日(S3)测量其株高和干重、植株地上与地下部分Na⁺和K⁺的含量以及底泥和水体中Na⁺和K⁺的含量以分析长苞香蒲对盐碱湿地的脱盐作用。结果表明：(1)各处理的长苞香蒲的株高和干重随着处理时间的延长呈增加趋势,但与CK相比,各处理生长量随盐浓度升高出现下降趋势。(2)高浓度盐处理(T3)使长苞香蒲的地上部分和地下部分的Na⁺分别增加了2.5...