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In order to test the response of phytoplankton to anthropogenic pressure, data of chlorophyll a concentration, phytoplankton abundance, and composition are analyzed in relation to anthropogenic pressure gradient and environmental variables such as temperature, salinity and nutrients. Investigated sites encompassed wide tropic range according to a preliminary determination of anthropogenic pressure, quantified through the LUSI index. Statistical analyses indicated nitrates and silicates as proxies of freshwater influence, and phytoplankton single metrics such as concentrations of chlorophyll a and abundances as indicators of anthropogenic pressure. Boundary values for different water quality classes for coastal waters under indirect freshwater influence (Type II) are obtained according to gradient between concentration of chlorophyll a and pressure index (LUSI), which empirically fit to exponential equation. The response of phytoplankton diversity was not linear, as the highest diversity was observed in the area with intermediate disturbance level. CCA analysis identified Skeletonema marinoii, Scrippsiella trochoidea, Guinardia flaccida, Leptocylindrus spp., Prorocentrum spp., Proboscia alata, Eutreptiella spp., and Pseudonitzschia spp. as local eutrophication indicators, whose abundances increased with nutrients loads. 相似文献
3.
The water relations of shoots of young jack pine (Pinus banksiana Lamb.) seedlings were examined 6 and 15 weeks after the initiation of four different dynamic nitrogen (N) treatments using a pressure-volume analysis. The N treatments produced a wide range of needle N concentrations from 12 to 32 mg g?1 dry mass and a 10-fold difference in total dry mass at 15 weeks. Osmotic potential at full turgor did not change over the range of needle N concentrations observed. Osmotic potential at turgor-loss point, however, declined as N concentrations decreased, indicating an increased ability of N-deficient jack pine plants to maintain turgor. The increase could be attributed largely to an increase in cell wall elasticity, suggesting that elasticity changes may be a common, significant adaptation of plants to environmental stresses. Dry mass per unit saturated water almost doubled as needle N level dropped from 32 to 12 mg g?1 and was inversely correlated to the bulk modulus of elasticity. This suggests that cell wall elasticity is determined more by the nature of its cross-linking matrix than by the total amount of cell wall material present. Developmental change was evident in the response of some water relation variables to N limitation. 相似文献
4.
Microscopic structural alterations of liver tissue induced by freeze-thaw cycles give rise to palpable property changes. However, the underlying damage to tissue architecture is difficult to quantify histologically, and published data on macroscopic changes in biophysical properties are sparse.To better understand the influence of hepatic cells and stroma on global biophysical parameters, we studied rat liver specimens freshly taken (within 30 min after death) and treated by freeze-thaw cycles overnight at either −20 °C or –80 °C using diffusion-weighted imaging (DWI) and multifrequency magnetic resonance elastography (MRE) performed at 0.5 T in a tabletop MRE scanner. Tissue structure was analyzed histologically and rheologic data were analyzed using fractional order derivatives conceptualized by a called spring-pot component that interpolates between pure elastic and viscous responses.Overnight freezing and thawing induced membrane disruptions and cell detachment in the space of Disse, resulting in a markedly lower shear modulus μ and apparent diffusion coefficient (ADC) (μ[−20 °C] = 1.23 ± 0.73 kPa, μ[−80 °C] = 0.66 ± 0.75 kPa; ADC[–20 °C] = 0.649 ± 0.028 μm2/s, ADC[−80 °C] = 0.626 ± 0.025 μm2/s) compared to normal tissue (μ = 9.92 ± 3.30 kPa, ADC = 0.770 ± 0.023 μm2/s, all p < 0.001). Furthermore, we analyzed the springpot-powerlaw coefficient and observed a reduction in −20 °C specimens (0.22 ± 0.14) compared to native tissue (0.40 ± 0.10, p = 0.033) and −80 °C specimens (0.54 ± 0.22, p = 0.002), that correlated with histological observations of sinusoidal dilation and collagen distortion within the space of Disse. Overall, the results suggest that shear modulus and water diffusion in liver tissue markedly decrease due to cell membrane degradation and cell detachment while viscosity-related properties appear to be more sensitive to distorted stromal and microvascular architecture. 相似文献
5.
Report cards are an increasingly popular method for summarising and communicating relative environmental performance and ecosystem health, including in aquatic environments. They are usually underpinned by an Ecosystem Health Index (EHI) that combines various individual indicators to produce an overall ecosystem health “score”. As a result of public water quality concerns, an integrated means of monitoring and reporting on aquatic ecosystem health was needed for the Fitzroy Basin in central Queensland, Australia. The Fitzroy Partnership for River Health was formed to address this need, and developed an EHI and report card for the Basin using existing monitoring data collected from various third parties including regulated companies operations and government. At 142,000 square kilometres, the Fitzroy Basin is the largest catchment draining to the World Heritage Listed Great Barrier Reef. The Fitzroy Basin provides an example of how to deliver an effective aquatic ecosystem health reporting system in a large and complex river basin. We describe the methodology used to develop an adaptive EHI for the Fitzroy Basin that addresses variability, complexity and scale issues associated with reporting across large areas. As well, we report how to manage the design and reporting stages given limitations in data collection and scientific understanding. 相似文献
6.
A three-step screening method was developed to identify the mode of phloem loading in intact leaves. Phloem loading of 14CO2-derived photosynthate was challenged by p-chloromercuribenzenesulfonic acid (PCMBS) in leaves of dicotyledons with either a symplasmic (type 1, with intermediary cells as companion cells) or apoplasmic (type 2b, with transfer cells as companion cells) minor-vein configuration. Firstly, photosynthate export as the result of phloem loading was measured by collection of phloem exudate from the petiole. The PCMBS had virtually no effect on photosynthate export in representatives of type-1 families (Lamiaceae, Lythraceae, Onagraceae, Saxifragaceae). In contrast, photosynthate export was strongly reduced by PCMBS in representatives of type-2b families (Asteraceae, Balsaminaceae, Dipsacaceae, Linaceae, Tropaeolaceae, Valerianaceae) and type-2b members of polytypical families (Fabaceae, Scrophulariaceae). Secondly, densitometric measurements of leaf autoradiographs demonstrated that the contrast between the mesophyll and the lower-order veins was hardly affected by PCMBS treatment in type-1 species, whereas PCMBS strongly reduced the contrast in type-2b species. Thirdly, separate 14C-radioassays of vein and mesophyll tissues confirmed this observation. The three-step procedure thus revealed a strong and consistent reduction of phloem loading by PCMBS in type-2b species which was absent in type-1 species. In conclusion, phloem loading in type-2b species occurs via the apoplast and type-1 species execute an alternative — most likely symplasmic — mode of phloem loading.Abbreviations PCMBS
p-chloromercuribenzenesulfonic acid
- SE/CC-complex
sieve element/companion cell complex
We gratefully acknowledge the expert help of Dr. Maarten Terlou, Department of Image Processing and Design, University of Utrecht, in carrying out the densitometric measurements. 相似文献
7.
Eutrophication resulting from nutrient enrichment decreases water quality and harms ecosystem structure and function, and its degree is significantly affected by land use in the catchment. Quantifying the relationship between eutrophication and land use can help effectively manage land use to improve water quality. Previous studies principally utilized land use quantity as an indicator to link water quality parameters, but these studies lacked insight into the impact of land use intensity. Taking the upper catchment of Miyun Reservoir as a case study, we developed a method of aggregating land use quantity and intensity to build a new land use indicator and tested its explanatory power on water quality. Six nutrient concentrations from 52 sub-watersheds covering the whole catchment were used to characterize the spatial distribution of eutrophication. Based on spatial techniques, empirical conversion coefficients, remote sensing data, and socio-economic statistical data, land use intensity was measured and mapped visually. The new land use indicator was calculated and linked to nutrient concentrations by Pearson correlation coefficients. Results demonstrated that our new indicator incorporating intensity information can quantify the different nutrient-exporting abilities of different land use areas. Compared to traditional indicators that only incorporate land use quantity, most Pearson correlation coefficients between the new indicator and water nutrient concentrations increased. This new information enhanced the explanatory power of land use on water nutrient concentrations, and so will be able to help us understand the impact of land use on water quality and guide decision making for better land use management. 相似文献
8.
Akihisa Hattori 《Journal of Ethology》2006,24(1):51-57
The distribution patterns of the leathery sea anemone, Heteractis crispa, which contains an algal endosymbiont (zooxanthellae) and anemonefish, were investigated in relation to size distribution on a shallow fringing reef (3.2 ha, 0–4 m depth) in Okinawa, Japan. Individual growth and movements were also examined. Large individuals (>1,000 cm2) inhabited reef edges up to a depth of 4 m, while small anemone (<500 cm2) inhabited shallow reefs including inner reef flats. Individuals rarely moved, and their sizes were significantly correlated with their water depths. Growth of small anemones was negatively correlated with their distance from the reef edge, suggesting that reef edges provide more prey and lower levels of physiological stress. This study suggested that deep reef edges are suitable habitats for H. crispa. Large anemones were inhabited by large Amphiprion perideraion or large Amphiprion clarkii, both of which are effective defenders against anemone predators. Anemones that settle in deep reef edges may enjoy a higher survival rate and attain a large size because of their symbiotic relationship with anemonefish. However, early settlers do not harbor anemonefish. Their mortality rate would be higher in the deep edges than in shallow edges, the complicated topography of which provides refuge. 相似文献
9.
With many advantages, many ecological parameters of protozoan communities have been successfully used as a useful bioindicator for bioassessment of water quality in Chinese marine waters. However, as regard the response of the annual cyclicity of protozoan communities to seasonal environmental stress, a further investigation was needed. In this study, the cyclicity of annual variations in community patterns of biofilm-dwelling protozoa was studied based on an annual dataset. Samples were monthly collected, using glass slide method, at four stations, within a pollution gradient, in coastal waters of the Yellow Sea, northern China during a 1-year period. The cyclicity patterns of the microbiota represented a significant spatial variation among four stations. The low value of cyclicity coefficients occurred in heavily polluted area, while the high values were in less stressed areas. Correlation analysis showed that the cyclicity measure was significantly related to environmental variables ammonia, transparency and dissolved oxygen. Thus, it is suggested that the annual cyclicity of protozoan communities may be used as a potential bioindicator of bioassessment in marine ecosystems. 相似文献
10.
Water scarcity is a widespread problem in many parts of the world. Most previous methods of water scarcity assessment only considered water quantity, and ignored water quality. In addition, the environmental flow requirement (EFR) was commonly not explicitly considered in the assessment. In this study, we developed an approach to assess water scarcity by considering both water quantity and quality, while at the same time explicitly considering EFR. We applied this quantity–quality-EFR (QQE) approach for the Huangqihai River Basin in Inner Mongolia, China. We found that to keep the river ecosystem health at a “good” level (i.e., suitable for swimming, fishing, and aquaculture), 26% of the total blue water resources should be allocated to meet the EFR. When such a “good” level is maintained, the quantity- and quality-based water scarcity indicators were 1.3 and 14.2, respectively; both were above the threshold of 1.0. The QQE water scarcity indicator thus can be expressed as 1.3(26%)|14.2, indicating that the basin was suffering from scarcity problems related to both water quantity and water quality for a given rate of EFR. The current water consumption has resulted in degradation of the basin's river ecosystems, and the EFR cannot be met in 3 months of a year. To reverse this situation, future policies should aim to reduce water use and pollution discharge, meet the EFR for maintaining healthy river ecosystems, and substantially improve pollution treatment. 相似文献