Nutrient Utilization Strategies of Algae and Bacteria after the Termination of Nutrient Amendment with Different Phosphorus Dosage: A Mesocosm Case

The impacts of nutrient amendment termination on the growth strategies of algae and bacteria were conducted in experimentally designed mesocosm in which two different phosphorus (P) dosages were treated. The algal community composition did not change greatly in Group A (low phosphorus) and Group B (high phosphorus). In Group A, the secretion of bacterial alkaline phosphatase (AP) after nutrient termination stimulated bacterial phosphorus acquisition, which caused the decrease in algal phosphorus levels, in terms of the increase of bacterial abundance and bacterial production, as well as the decrease in chlorophyll a and particulate organic carbon. The algal collapse resulted in dissolved organic carbon secretion, further fuelling bacterial growth. In Group B, excess phosphorus input urged algae to store phosphorus as poly-phosphate. When phosphorus input ceased, in order to maintain their used high phosphorus demand, algae strengthened to gain phosphorus through the hydrolysis of dissolved organic phosphorus in water column and ploy-phosphate inside the cells by AP, evidenced by high algal alkaline phosphatase activity, algal growth continuation, and bacterial growth decline. These facts indicated that phosphorus content should reduce to a lower level than expected, so that algal bloom can be effectively controlled in eutrophic water bodies.     

Sediment and Water Nutrient Characteristics in Patches of Submerged Macrophytes in Running Waters

(1) The relative importance of sediments and water as nutrient sources for submerged macrophytes in running waters is poorly understood. Here we present water and sediment nutrient characteristics within macrophyte patches in Bavarian rivers. (2) No significant differences between early (June/July) and late summer (August/September) sediment nutrient characteristics could be detected within macrophyte patches. Therefore, a single sediment sample per macrophyte patch was considered to be sufficient for characterising nutrient concentrations during the main growing season in running waters. (3) Sediment TP (total phosphorus) is not a useful parameter for predicting trophic status in running waters. Sediment porewater SRP (soluble reactive phosphorus) concentration is not correlated to water body SRP or TP concentration; nor is it correlated with sediment TP content. Potamogeton coloratus, a oligotrophic species, is associated with low overlying and porewater SRP concentrations but high sediment TP content. Eutrophic species, such as Potamogeton pectinatus, are associated with low sediment TP. (4) It is hypothesized that Chara hispida primarily takes up sediment ammonia for nitrogen nutrition. (5) Nutrient characteristics of the water body and the sediment of eight macrophyte species in Bavarian rivers are described.     

Virus-Bacterium Interactions in Water and Sediment of West African Inland Aquatic Systems

The ecology of virioplankton in tropical aquatic ecosystems is poorly documented, and in particular, there are no references concerning African continental waters in the literature. In this study, we examined virus-bacterium interactions in the pelagic and benthic zones of seven contrasting shallow inland waters in Senegal, including one hypersaline lake. SYBR Gold-stained samples revealed that in the surface layers of the sites, the numbers of viruses were in the same range as the numbers of viruses reported previously for productive temperate systems. Despite high bacterial production rates, the percentages of visibly infected cells (as determined by transmission electron microscopy) were similar to the lowest percentages (range, 0.3 to 1.1%; mean, 0.5%) found previously at pelagic freshwater or marine sites, presumably because of the local environmental and climatic conditions. Since the percentages of lysogenic bacteria were consistently less than 8% for pelagic and benthic samples, lysogeny did not appear to be a dominant strategy for virus propagation at these sites. In the benthic samples, viruses were highly concentrated, but paradoxically, no bacteria were visibly infected. This suggests that sediment provides good conditions for virus preservation but ironically is an unfavorable environment for proliferation. In addition, given the comparable size distributions of viruses in the water and sediment samples, our results support the paradigm that aquatic viruses are ubiquitous and may have moved between the two compartments of the shallow systems examined. Overall, this study provides additional information about the relevance of viruses in tropical areas and indicates that the intensity of virus-bacterium interactions in benthic habitats may lower than the intensity in the adjacent bodies of water.     

Interactions Between Rhinanthus minor and Its Hosts: A Review of Water, Mineral Nutrient and Hormone Flows and Exchanges in the Hemiparasitic Association

At the ecological level, the effects of the facultative root hemiparasite Rhinanthus minor on the structure and functioning of its host communities are relative well described; yet until recently, the mechanistic basis for parasitic plant-driven community change and the physiological basis for the host-parasite interaction were poorly understood. Empirical incremental flow models, based on the increase in water, mineral nutrients, carbon assimilates or phytohormones between two defined time points, have been successfully employed to investigate the physiology of resource acquisition by- and distribution within host-parasitic plant associations. In this study we review the application of these empirical flow models to Rhinanthus-host associations showing the extent of and physiological basis of resource abstraction from the host and how this is profoundly influenced by soil nutrient status. We show that Rhinanthus primarily abstracts water and mineral nutrients via the apoplastic pathway through direct lumen-lumen connections with little resource acquisition via symplastic pathways. Nutrient status of the soil is shown to significantly influence the resource acquisition. We also investigate the hormonal regulation of resource acquisition by Rhinanthus showing pivotal roles for the key for the phytohormones abscisic acid (ABA) and cytokinins.     

A Multi-Year Longitudinal Study of Water Quality Parameters in Four Salmon-Bearing and Recreational Streams on Mount Hood,Oregon

Four streams–Clear Fork, Lost Creek, Camp Creek and Still Creek–in northwestern Oregon’s Sandy River Basin were monitored for temperature, dissolved oxygen levels, and fecal bacterial concentrations in a multi-year analysis examining stream health for recreational users and anchor habitat for Pacific Salmon. Temperatures were recorded using micro –T temperature loggers at 15 locations, during 22 July - 5 September 2006, 2 July - 4 September 2007, 20 June - 7 September 2008, 23 June - 9 September 2009, and 2 July –9 September 2010. The Seven-Day Average Maximum water temperature (7-DAM) of 13°C was used as a reference value for the biological limit governing suitable salmonid spawning and egg incubation conditions. The maximum 7-DAM temperatures occurred on different dates and all streams neared or exceeded the 13°C standard at least once each summer. Dissolved oxygen levels were measured at weekly or longer intervals in 2006, 2007, 2008, and 2009. Dissolved oxygen levels fell below the 9.0 ppm standard for Clear Fork on almost half the sampling dates in 2006, 2007, and 2009. Concentrations of the bacterial genus Enterococcus were measured as an indicator of fecal contamination. Samples were collected at 15 sites along the four streams. Weekly samples were collected during a 9 week period from July - September 2007, an 11 week period from June - September 2008, and an 11 week period from June - September 2009. Enterococcus counts exceeded the federal recommended national criterion value of 61 colony forming units (CFU) per 100 mL every year in Camp Creek and occasionally elsewhere, with exceedances trending towards late summer.     

Knowledge,Attitudes and Practice of Desalinated Water among Professionals in Health and Water Departments in Shengsi,China: A Qualitative Study

Desalination has been considered as an essential way to solve water stress all over the world. Most of previous studies focused on its environmental impacts, energy consumption and desalination technologies rather than human health. However, the safety of desalinated water remains unclear. This study was undertaken to investigate the knowledge, attitude and practice (KAP) of the residents in an island county in eastern China to desalinated water. Seventeen people working in medical and water industries were recruited, and focus group discussion and in-depth interview were conducted among them. Our results showed that the majority of people interviewed knew the definition and local supply pattern of desalinated water, while some of them showed some concern about the safety and nutrition of desalinated water. Current drinking water standard has no specific item for desalination, so we strongly suggest issuing a standard for desalinated water.     

The Mechanisms of Water Exchange: The Regulatory Roles of Multiple Interactions in Social Wasps

Evolutionary benefits of task fidelity and improving information acquisition via multiple transfers of materials between individuals in a task partitioned system have been shown before, but in this paper we provide a mechanistic explanation of these phenomena. Using a simple mathematical model describing the individual interactions of the wasps, we explain the functioning of the common stomach, an information center, which governs construction behavior and task change. Our central hypothesis is a symmetry between foragers who deposit water and foragers who withdraw water into and out of the common stomach. We combine this with a trade-off between acceptance and resistance to water transfer. We ultimately derive a mathematical function that relates the number of interactions that foragers complete with common stomach wasps during a foraging cycle. We use field data and additional model assumptions to calculate values of our model parameters, and we use these to explain why the fullness of the common stomach stabilizes just below 50 percent, why the average number of successful interactions between foragers and the wasps forming the common stomach is between 5 and 7, and why there is a variation in this number of interactions over time. Our explanation is that our proposed water exchange mechanism places natural bounds on the number of successful interactions possible, water exchange is set to optimize mediation of water through the common stomach, and the chance that foragers abort their task prematurely is very low.     

Physiological and Morphological Responses of the Temperate Seagrass Zostera muelleri to Multiple Stressors: Investigating the Interactive Effects of Light and Temperature

Understanding how multiple environmental stressors interact to affect seagrass health (measured as morphological and physiological responses) is important for responding to global declines in seagrass populations. We investigated the interactive effects of temperature stress (24, 27, 30 and 32°C) and shading stress (75, 50, 25 and 0% shade treatments) on the seagrass Zostera muelleri over a 3-month period in laboratory mesocosms. Z. muelleri is widely distributed throughout the temperate and tropical waters of south and east coasts of Australia, and is regarded as a regionally significant species. Optimal growth was observed at 27°C, whereas rapid loss of living shoots and leaf mass occurred at 32°C. We found no difference in the concentration of photosynthetic pigments among temperature treatments by the end of the experiment; however, up-regulation of photoprotective pigments was observed at 30°C. Greater levels of shade resulting in high photochemical efficiencies, while elevated irradiance suppressed effective quantum yield (ΔF/F_M’). Chlorophyll fluorescence fast induction curves (FIC) revealed that the J step amplitude was significantly higher in the 0% shade treatment after 8 weeks, indicating a closure of PSII reaction centres, which likely contributed to the decline in ΔF/F_M’ and photoinhibition under higher irradiance. Effective quantum yield of PSII (ΔF/F_M’) declined steadily in 32°C treatments, indicating thermal damage. Higher temperatures (30°C) resulted in reduced above-ground biomass ratio and smaller leaves, while reduced light led to a reduction in leaf and shoot density, above-ground biomass ratio, shoot biomass and an increase in leaf senescence. Surprisingly, light and temperature had few interactive effects on seagrass health, even though these two stressors had strong effects on seagrass health when tested in isolation. In summary, these results demonstrate that populations of Z. muelleri in south-eastern Australia are sensitive to small chronic temperature increases and light decreases that are predicted under future climate change scenarios.     

Stressors, Stress Reactions, and Survival of Bacteria: A Review

Recent data on the molecular mechanisms of the stress responses of bacteria are reviewed, with emphasis on their reactions to a variety of stressors (heat, oxidation, cold, osmotic shock, etc.). The mechanisms underlying the phenomenon of sensoring are discussed. It is shown that cross-resistance to stressors and cell-to-cell communication, mediated by chemical metabolites, affect bacterial survival in food products. The stress-antagonizing activity of bacteria is discussed in relation to food product biotechnology.     

Testing the Sensitivity of Phytoplankton Communities to Changes in Water Temperature and Nutrient Load, in a Temperate Lake

Freshwater lakes are biologically sensitive to changes in the surrounding environment and the impacts that such changes have on their water quality are of considerable ecological, recreational and economic importance. In this study the phytoplankton community model, PROTECH, was used to experiment with the effects of elevated temperatures and increased nutrient load on phytoplankton succession and productivity. The response of a phytoplankton community to combined incremental changes in these drivers was analysed, in order to elucidate the resulting ecological changes. Annual mean phytoplankton biomass increased with increases in temperature and nutrient loading, although the latter had the larger effect. The phenology of the dominant phytoplankton taxa changed with increasing water temperature; the three spring blooming species all peaked earlier in the year. The simulated summer bloom of Anabaena became earlier in the year and the Chlorella bloom later. The increased phytoplankton biomass was largely dominated by the cyanobacterium Anabaena, which was especially prevalent during the summer bloom. This resulted in a progressive loss of phytoplankton biodiversity with increasing water temperature and nutrient supply. Model experimentation showed that whilst both factors greatly affected the community, the changes to nutrient loading generally had the greater effect and that at low nutrient levels the effect of water temperature change was reduced considerably. Finally, the model predicted that cyanobacteria have the potential to dominate the phytoplankton community, with clear consequences for water quality, and that this dominance was at its greatest when high water temperatures were combined with high nutrient loads.     

Investigating the Relationships among Stressors,Stress Level,and Mental Symptoms for Infertile Patients: A Structural Equation Modeling Approach

Objective

Patients with infertility are a high risk group in depression and anxiety. However, an existing theoretically and empirically validated model of stressors, stress, and mental symptoms specific for infertile patients is still a void. This study aimed to determine the related factors and their relational structures that affect the level of depressive and anxiety symptoms among infertile patients.

Methods

A cross-sectional sample of 400 infertility outpatients seeking reproduction treatments in three teaching hospitals across Taiwan participated in the structured questionnaire survey in 2011. The hypothesized model comprising 10 latent variables was tested by Structural Equation Modeling using AMOS 17.

Results

Goodness-of-fit indexes, including χ²/DF = 1.871, PGFI = 0.746, PNFI = 0.764, and others, confirmed the modified model fit the data well. Marital stressor, importance of children, guilt-and-blame, and social stressor showed a direct effect on perceived stress. Instead of being a factor of stress, social support was directly and positively related to self-esteem. Perceived stress and self-esteem were the two major mediators for the relationships between stressors and mental symptoms. Increase in social support and self-esteem led to decrease in mental symptoms among the infertile patients.

Conclusions

The relational structures were identified and named as the Stressors Stress Symptoms Model, clinically applied to predict anxiety and depression from various stressors. Assessing sources and level of infertility-related stress and implementing culturally-sensitive counseling with an emphasis on positive personal value may assist in preventing the severity of depression and anxiety.     

Bacterial Diversity in Shallow Oligotrophic Marine Benthos and Overlying Waters: Effects of Virus Infection,Containment, and Nutrient Enrichment

Little is known of the factors shaping sediment bacterial communities, despite their high abundance and reports of high diversity. Two factors hypothesized to shape bacterial communities in the water column are nutrient (resource) availability and virus infection. The role these factors play in benthic bacterial diversity was assessed in oligotrophic carbonate–based sediments of Florida Bay (USA). Sediment–water mesocosm enclosures were made from 1-m diameter clear polycarbonate cylinders which were pushed into sediments to 201 cm sediment depth enclosing 80 L of water. Mesocosms were amended each day for 14 d with 10 µM NH ₄ ⁺ and 1 µM PO ₄ ^3– . In a second experiment, viruses from a benthic flocculent layer were concentrated and added back to flocculent layer samples which were collected near the mesocosm enclosures. Photosynthesis by microalgae in virus-amended incubations was monitored by pulse-amplitude modulated (PAM) fluorescence. In both experiments, bacterial diversity was estimated using automated rRNA intergenic spacer analysis (ARISA), a high-resolution fingerprinting approach. Initial sediment bacterial operational taxonomic unit (OTU) richness (236 ± 3) was higher than in the water column (148 ± 9), where an OTU was detectable when its amplified DNA represented >0.09% of the total amplified DNA. Effects on bacterial diversity and operational taxonomic unit (OTU) richness in nutrient-amended mesocosms may have been masked by the effects of containment, which stimulated OTU richness in the water column, but depressed OTU richness and diversity in sediments. Nutrient addition significantly elevated virus abundance and the ratio of viruses to bacteria (p < 0.05 for both) in the sediments, concomitant with elevated bacterial diversity. However, water column bacterial diversity (in unamended controls) was not affected by nutrient amendments, which may be due to rapid nutrient uptake by sediment organisms or adsorption of P to carbonate sediments. Addition of live viruses to benthic flocculent layer samples increased bacterial OTU diversity and richness compared with heat-killed controls; however, cluster analyses showed that the community structure in the virus-amended mesocosms varied greatly between replicates. Despite the strong effects upon eubacterial communities, photosynthesis of co-occurring protists and cyanobacteria was not significantly altered by the presence of virus concentrates. This study supports the hypothesis that nutrient availability plays a key role in shaping sediment bacterial communities, and also that viruses may regulate the abundance of the dominant competitors and allow less dominant organisms to maintain or increase their abundance in a community due to decreased competition for resources.     

Estimation of Agricultural Water Consumption from Meteorological and Yield Data: A Case Study of Hebei,North China

Over-exploitation of groundwater resources for irrigated grain production in Hebei province threatens national grain food security. The objective of this study was to quantify agricultural water consumption (AWC) and irrigation water consumption in this region. A methodology to estimate AWC was developed based on Penman-Monteith method using meteorological station data (1984–2008) and existing actual ET (2002–2008) data which estimated from MODIS satellite data through a remote sensing ET model. The validation of the model using the experimental plots (50 m²) data observed from the Luancheng Agro-ecosystem Experimental Station, Chinese Academy of Sciences, showed the average deviation of the model was −3.7% for non-rainfed plots. The total AWC and irrigation water (mainly groundwater) consumption for Hebei province from 1984–2008 were then estimated as 864 km³ and 139 km³, respectively. In addition, we found the AWC has significantly increased during the past 25 years except for a few counties located in mountainous regions. Estimations of net groundwater consumption for grain food production within the plain area of Hebei province in the past 25 years accounted for 113 km³ which could cause average groundwater decrease of 7.4 m over the plain. The integration of meteorological and satellite data allows us to extend estimation of actual ET beyond the record available from satellite data, and the approach could be applicable in other regions globally where similar data are available.     

Mapping the Spatial Extent of Depositional Areas in Agricultural,Urban, and Residential California Streams: Implications for Pyrethroid Toxicity

Wetted stream-bed mapping at randomly selected sites in an agricultural stream (Del Puerto Creek), urban stream (Arcade Creek), and residential stream (Pleasant Grove Creek) in California was conducted to determine the spatial extent of depositional and non-depositional areas. This study evaluated the “representativeness” of standard sediment sampling approaches used in California by using hydrophobic pyrethroids as an example. Measured background concentrations of eight pyrethroids in sediment and potential sediment toxicity for each stream were discussed within the context of depositional areas. Four percent, 15%, and 12% of the randomly selected transects in Del Puerto Creek, Arcade Creek, and Pleasant Grove Creek, respectively, were depositional areas. For all three streams, depositional areas were more dominant in downstream segments. Pyrethroid concentrations in sediment were higher in depositional areas versus non-depositional areas in Del Puerto Creek and were also higher downstream. Pyrethroid concentrations in sediment were also higher in downstream areas of Arcade Creek but generally higher in upstream areas of Pleasant Grove Creek. The results from this study demonstrate the importance of determining “representativeness” of depositional areas for an entire stream if hydrophobic chemicals (pyrethroids) measured in sediment from depositional areas are suspected to be toxic.     

Drivers of Sediment Accumulation and Nutrient Burial in Coastal Stormwater Detention Ponds,South Carolina,USA

Stormwater detention ponds are widely utilized as control structures to manage runoff during storm events. These ponds also represent biogeochemical hotspots, where carbon (C) and nutrients can be processed and buried in sediments. This study quantified C and nutrient [nitrogen (N) and phosphorus (P)] sources and burial rates in 14 stormwater detention ponds representative of typical residential development in coastal South Carolina. Bulk sediment accumulation was directly correlated with catchment impervious surface coverage (R² = 0.90) with sediment accumulation rates ranging from 0.06 to 0.50 cm y^?1. These rates of sediment accumulation and consequent pond volume loss were lower than anticipated based on maintenance guidelines provided by the State. N-alkanes were used as biomarkers of sediment source; the derived terrestrial aquatic ratio (TAR_HC) index was strongly correlated with sediment accumulation rate (R² = 0.71) which, in conjunction with high C/N ratios (16–33), suggests that terrestrial biomass drives this sediment accumulation, with relatively minimal contributions from algal derived material. This is counter to expectations that were based on the high algal productivity generally observed in stormwater ponds and previous studies of natural lakes. Sediment C and nutrient concentrations were consistent among ponds, such that differences in burial rates were a simple function of bulk sediment accumulation rate. These burial rates (C: 8.7–161 g m^?2 y^?1, N: 0.65–6.4 g m^?2 y^?1, P: 0.238–4.13 g m^?2 y^?1) were similar to those observed in natural lake systems, but lower than those observed in reservoirs or impoundments. Though individual ponds were small in area (930–41,000 m²), they are regionally abundant and, when mean burial rates are extrapolated to the regional scale (≈ 21,000 ponds), ultimately sequester 2.0 × 10⁹ g C y^?1, 9.5 × 10⁷ g N y^?1, and 3.7 × 10⁷ g P y^?1 in the coastal region of South Carolina alone. Stormwater ponds represent a relatively new but increasingly significant feature of the coastal landscape and, thus, are a key component in understanding how urbanization alters the transport and transformations of C and nutrients between terrestrial uplands and downstream receiving waters.     

Edges in Agricultural Landscapes: Species Interactions and Movement of Natural Enemies

Agricultural landscapes can be characterized as a mosaic of habitat patches interspersed with hostile matrix, or as a gradient of patches ranging from suitable to unsuitable for different species. Arthropods moving through these landscapes encounter a range of edges, with different permeability. Patches of native vegetation in these landscapes may support natural enemies of crop pests by providing alternate hosts for parasitic wasps and/or acting as a source for predatory insects. We test this by quantifying species interactions and measuring movement across different edge-types. A high diversity of parasitoid species used hosts in the native vegetation patches, however we recorded few instances of the same parasitoid species using hosts in both the native vegetation and the crop (canola). However, we did find overall greater densities of parasitoids moving from native vegetation into the crop. Of the parasitoid groups examined, parasitoids of aphids (Braconidae: Aphidiinae) frequently moved from native vegetation into canola. In contrast, parasitoids of caterpillars (Braconidae: Microgastrinae) moved commonly from cereal fields into canola. Late season samples showed both aphids and parasitoids moving frequently out of native vegetation, in contrast predators moved less commonly from native vegetation (across the whole season). The season-long net advantage or disadvantage of native vegetation for pest control services is therefore difficult to evaluate. It appears that the different edge-types alter movement patterns of natural enemies more so than herbivorous pest species, and this may impact pest control services.     

Dynamics of Nutrient Contents (Phosphorus,Nitrogen) in Water,Sediment and Plants After Restoration of Connectivity in Side‐Channels of the River Rhine

During the last century, canalization of the Rhine river led to disconnection of side‐arms, over‐sedimentation of these channels, loss of the fluvial dynamics, and aquatic vegetation change or disappearance. Recent restoration projects aim to reconnect disconnected arms to the main channel. The objective of this study was to assess the nutrient dynamics in restored channels during the vegetation colonization process. In spring, summer, and autumn 2009, the phosphorus and nitrogen contents were measured in water, sediment, and plants, sampled in six channels, two reference sites and four restored ones at different dates. Aquatic vegetation was monitored during the same period. Sites were mesotrophic related to the water nutrient concentrations. However, vegetation communities indicated a eutrophic level, as they were dominated by species like Elodea nuttallii, Myriophyllum spicatum, and Potamogeton perfoliatus. Sites were discriminated by P content and mineral nitrogen in the sediment. We showed an effect of species and season on the plant nutrient content, but there was no relationship between plant nutrient content and nutrients in water and sediment. A negative correlation between mean N plant content and the cover of each species was found. Vegetation characteristics (species richness and cover) and bioavailable phosphorus in the sediment were also correlated. In the restored side‐arms of the river Rhine, phosphorus‐rich sediment seems to be important in the recolonization dynamics, as it was linked to higher species richness, whereas nitrogen played a role in the colonization patterns as a growth limiting factor.