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1.
We examined changes in biomass and species dominance of periphyton in response to nitrogen (N) and phosphorus (P) enrichment in 12 mesocosms representing eutrophic aquatic ecosystems. The 100-L mesocosms consisted of lake water and pond sediment, and N and P were applied weekly. Periphyton samples were taken to assess the biomass (as estimated by the concentration of chlorophyll a (chl a)) and to determine which species were dominant. The mean periphyton biomass (chl a) in the P-enriched treatment did not differ from that in the control group, but increased with N enrichment. Compared with that in the control group, the chl a concentration increased with N+P enrichment in the early stages of the experiment, but decreased in the later stages. The decline in periphyton biomass at the later stages of the experiment was due to limited light availability, which resulted from the increased phytoplankton density in the experiment. The nutrient enrichment treatments resulted in changes in the dominant algal species in the periphyton, suggesting that various algal species showed different responses to different nutrients. The results of this study have implications for nutrient management in aquatic ecosystems. 相似文献
2.
The increasing riverine pollutants have resulted in nutrient enrichment and deterioration of water quality in the coastal water of Guangxi Province, China. However, the quantitative relationship between nutrient loads and water quality responses, which is crucial for developing eutrophication control strategies, is not well studied. In this study, the riverine fluxes of nutrients were quantified and integrated with nutrient cycling and phytoplankton dynamics by using box models for Guangxi coastal bays. The model concepts and biogeochemical equations were the same; while most model parameters were specific for each bay. The parameters were calibrated with seasonal observations during 2006–2007, and validated with yearly averaged measurements in 2009. The general features of nutrient and phytoplankton dynamics were reproduced, and the models were proved feasible under a wide range of bay conditions. Dissolved inorganic nitrogen was depleted during the spring algal bloom in Zhenzhu Bay and Fangcheng Bay with relatively less nutrient inputs. Phosphorus concentration was high in spring, which decreased then due to continuous phytoplankton consumption. Chlorophyll-a concentration reached its annual maximum in summer, but was the minimum in winter. Eutrophication was characterized by both an increase in nutrient concentrations and phytoplankton biomass in Lianzhou Bay. Either about 80% reduction of nitrogen or 70% reduction of phosphorus was required to control the algal bloom in Lianzhou Bay. Defects of the models were discussed and suggestions to the environmental protection of Guangxi coastal bays were proposed. 相似文献
3.
Sediment-water fluxes of N and P species in the Bohai Sea were investigated in September-October 1998 and April-May 1999. The benthic fluxes of nutrient species were determined by incubating sediment core samples with bottom seawater bubbled with air or nitrogen. NO^-2,NH4, dissolved organic nitrogen (DON) and phosphorus (DOP), total dissolved nitrogen (TDN) and phosphorus (TDP), and PO4^3- showed a net exchange flux from seawater to sediment, while NO^-3, dissolved inorganic nitrogen (DIN) and SiO3^2- were released from sediment to seawater in the Bohai Sea. Sediment-water nutrient exchange increases DIN and reduces the phosphorus load in the Bohai Sea. The release of silicate from sediment to overlying seawater reduces potential silicate limitation of primary production resulted from decrease of riverine discharge.The exchange flux of nutrients showed no obvious seasonal variation. The present study showed that the concentrations and composition of nutrients in the water column were affected by suspended sediment, and that not all the exchangeable phosphate in sediment could be released via sediment resuspension. 相似文献
4.
1 INTRODUCTION Surface blooms of nuisance cyanobacteria are often a signal of eutrophication (Jacoby et al., 2000). They are generally favored by conditions of low nitrogen to phosphorus ratios, high total phosphorus content, high water temperature, high … 相似文献
5.
A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded. 相似文献
6.
The freshwater cyanobacterium, Cylindrospermopsis raciborskii (Wo?oszyńska) Seenayya and Subba Raju is a common species in lakes and reservoirs globally. In some areas of the world it can produce cyto- and hepatotoxins (cylindrospermopsins, saxitoxins), making blooms of this species a serious health concern for humans. In the last 10-15 years, there has been a considerable body of research conducted on the ecology, physiology and toxin production of this species and this paper reviews these studies with a focus on the cylindrospermopsin (CYN)-producing strains. C. raciborskii has low light requirements, close to neutral buoyancy, and a wide temperature tolerance, giving it the capacity to grow in many lentic waterbodies. It also has a flexible strategy with respect to nitrogen (N) utilisation; being able to switch between utilising fixed and atmospheric N as sources of N fluctuate. Additionally this species has a high phosphate (DIP) affinity and storage capacity. Like many cyanobacteria, it also has the capacity to use dissolved organic phosphorus (DOP). Changes in nutrient concentrations, light levels and temperature have also been found to affect production of the toxin CYN by this species. However, optimal toxin production does not necessarily occur when growth rates are optimal. Additionally, different strains of C. raciborskii vary in their cell quota of CYN, making it difficult to predict toxin concentrations, based on C. raciborskii cell densities. In summary, the ecological flexibility of this organism means that controlling blooms of C. raciborskii is a difficult undertaking. However, improved understanding of factors promoting the species and toxin production by genetically capable strains will lead to improved predictive models of blooms. 相似文献
7.
The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes
much to it. A Sino-German cooperation program has been carried out to improve the understanding of the ecosystem by observations
and modelling. A three-dimensional ecosystem model, coupled with a physical transport model, is adopted in this study. The
simulation for the year 1982 is validated by the data collected in 1982/1983. The simulated annual mean nutrient concentrations
are in good agreement with observations. The nutrient concentrations in the bohai Sea, which are crucial to the algal growth,
are high in winter and low in summer. There are depletion from spring to summer and elevation from autumn to winter for nutrients.
The nutrients’ depletion is a response to the consumption of the phytoplankton bloom in spring. Internal recycle and external
compensation affect the nutrient cycle. Their contributions to the nutrient budgets are discussed based on the simulated results.
Production and respiration are the most important sink and source of nutrients. The process of photosynthesis consumes 152
kilotons-P and 831.1 kilotons-N while respiration releases 94.5 kilotons-P and 516.6 kilotons-N in the same period. The remineralization
of the detritus pool is an important source of nutrient regeneration, It can compensate 23 percent of the nutrient consumed
by the production process. The inputs of phosphates and nitrogen from rivers are 0.55 and 52.7 kilotons respectively. The
net nutrient budget is −3.05 kilotons-P and 31.6 kilotons-N. 相似文献
8.
根据2004年6月中旬在鳌山湾海区所取得的底层海水营养盐资料,分析了青岛鳌山湾海区营养盐的平面分布特征;运用绝对限制法则和相对限制法则确定了鳌山湾海区的营养盐限制因子;采用营养状态综合指数法和分类分级富营养化评价模式对鳌山湾海域的营养状况进行了评价。结果表明:鳌山湾营养盐限制因子为磷(P),该海区由缺氮转变为缺磷,营养盐结构发生了根本性变化,且该海域无富营养化现象,水质较好。 相似文献
9.
Livestock behaviour in the Pyrenees includes free grazing and a long resting period that provokes the accumulation of dung and urine in some places,so-called camping areas. The aims of this study were （i） to analyze any change in floral composition,and in nutritional and chemical contents of plants in a livestock camping area; and （ii） to relate the floral composition with soil chemical properties. In a linear transect,five sampling zones were established,from the centre of the camping area to the surrounding Nardus stricta-dominant pasture. The above ground plant biomass and the topsoil were sampled in each zone with 6 replicates per zone. Plant species were classified and weighed to calculate above ground biomass,nutritional and chemical contents,and Shannon diversity and evenness indices. Additionally,soils were sampled in two periods,at the beginning and at the end of grazing period. Soil available nutrients （nitrate,ammonium,phosphorus,potassium,calcium and magnesium）,total nitrogen,organic carbon and pH were measured.
Plant chemical contents （protein,lignin and others） were significantly related to the proportions of grasses,legumes and other plants; so,the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However,the relationship among plant species richness,diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area,plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers.
Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale,the strong soil nutrien 相似文献
Plant chemical contents （protein,lignin and others） were significantly related to the proportions of grasses,legumes and other plants; so,the protein content is positively correlated with legumes plant biomass while lignin content is negatively correlated with grasses. Both plant and soil nutrients increased linearly towards the centre of the camping area. However,the relationship among plant species richness,diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area,plants with low nutrient demand were progressively replaced by those with medium and high nutrients demand and by pioneers.
Nardus stricta-dominant pasture has low plant diversity and plant nutrient content as well as a poor soil nutrient availability. The presence of the camping area introduced patches with more soil nutrients and new species in the large spatial scale. However at a small spatial scale,the strong soil nutrien 相似文献
10.
Although biomass variations in Microcystis and microcystin have been widely reported,few studies have addressed whether different trophic states of natural lake water affect the spatial-temporal variations in abundances of microcystin-producing Microcystis in a given bloom.In this study,we used a harmful algal bloom in Chaohu Lake,eastern China,as an example to investigate the mutual relationship between different nutrient states and environmental factors,and the impact on Microcystis.Overall,cyanobacteria and Microcystis were more abundant in the middle and western parts of the lake under high nutrients levels,while in the eastern part,nutrient concentrations were low enough to limit biomass,and their fluctuations affected the contents of toxic Microcystis.Moreover,microcystin concentration was correlated positively to nutrient levels and Microcystis biomass during bloom developing in 2013 from June to August.Temporally,the cellular content of total microcystin was lowest when the bloom peaked in intensity.Our results suggest that lake eutrophication not only results in cyanobacterial blooms,but may also increase the proportion of toxic Microcystis species and their cell-bound MCs contents(i.e.microcystin cell quotas) under mild eutrophication.The present investigation provided molecular evidence for the selection of MC-producing and non-MC-producing genotypes.The current study provides new evidence advocating the monitoring of partitions of large lakes when studying cyanobacteria and toxin-contaminated freshwaters,which will be beneficial for both water agencies and water researchers. 相似文献
11.
《山地科学学报》2017,(1)
Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum,an evergreen alpine shrub species,occupies a wide range of habitats above timberline in the Miyaluo Natural Reserve,southwestern China. Along an altitudinal gradient ranging from 3700 to 4150 m,we measured leaf morphological characters including leaf dry matter content(LDMC),leaf dry mass per unit area(LMA),and one leaf area(OLA),as well as carbon(C) and nutrient(N,P) contents in leaves of three different age groups(juvenile leaves,mature leaves and senescent leaves). We also calculated the stoichiometric relationships among carbon and nutrients(C/N,C/P and N/P). Results showed thatboth age and altitude affected the leaf morphological and stoichiometric properties of R. agglutinatum. Mature leaves possessed the highest LDMC,LMA and C contents both on a dry mass basis and on a unit area basis. Younger leaves possessed higher contents of nutrients. OLA as well as ratios between carbon and nutrients(C/N,C/P) increased with ages. Juvenile leaves possessed lowest ratio between nitrogen and phosphorus. In juvenile leaves,nutrients increased with altitudinal elevation,whereas other traits decreased. In mature leaves,nutrients and their ratios with carbon showed consistent trends with juvenile leaves along increasing altitude,whereas LMA and carbon on a unit area basis showed opposite trends with juvenile leaves along increasing altitude. In senescent leaves,only content of phosphorus on a unit area basis and N/P were found linearly correlated with altitude. Our results demonstrated a clear pattern of nutrient distribution with aging process inleaves and indicated that a high possibility of N limitation in this region. We also concluded that younger leaves could be more sensitive to climate changes due to a greater altitudinal influence on the leaf traits in younger leaves than those in elder leaves. 相似文献
12.
Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum, an evergreen alpine shrub species, occupies a wide range of habitats above timberline in the Miyaluo Natural Reserve, southwestern China. Along an altitudinal gradient ranging from 3700 to 4150 m, we measured leaf morphological characters including leaf dry matter content (LDMC), leaf dry mass per unit area (LMA), and one leaf area (OLA), as well as carbon (C) and nutrient (N, P) contents in leaves of three different age groups (juvenile leaves, mature leaves and senescent leaves). We also calculated the stoichiometric relationships among carbon and nutrients (C/N, C/P and N/P). Results showed that both age and altitude affected the leaf morphological and stoichiometric properties of R. agglutinatum. Mature leaves possessed the highest LDMC, LMA and C contents both on a dry mass basis and on a unit area basis. Younger leaves possessed higher contents of nutrients. OLA as well as ratios between carbon and nutrients (C/N, C/P) increased with ages. Juvenile leaves possessed lowest ratio between nitrogen and phosphorus. In juvenile leaves, nutrients increased with altitudinal elevation, whereas other traits decreased. In mature leaves, nutrients and their ratios with carbon showed consistent trends with juvenile leaves along increasing altitude, whereas LMA and carbon on a unit area basis showed opposite trends with juvenile leaves along increasing altitude. In senescent leaves, only content of phosphorus on a unit area basis and N/P were found linearly correlated with altitude. Our results demonstrated a clear pattern of nutrient distribution with aging process in leaves and indicated that a high possibility of N limitation in this region. We also concluded that younger leaves could be more sensitive to climate changes due to a greater altitudinal influence on the leaf traits in younger leaves than those in elder leaves. 相似文献
13.
Systematic studies of the changes in dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) and their
effects on phytoplankton over the last 30 years in the Bohai Sea are presented. The amount of sewage disposal, use of fertilizer
and the Huanghe River runoff were found to have a significant influence on the DIN or DIP concentrations in the Bohai Sea
over the last 30 years. Moreover, the changes in DIN and DIP resulted in changes in the limiting nutrients of phytoplankton
in the Bohai Sea from nitrogen in the early 1980s to nitrogen-phosphorus in the late 1980s, and then to phosphorus after the
1990s. In addition, changes in nitrogen and phosphorus had a significant effect on the phytoplankton community structure.
The half saturation constant (K
s) was used to evaluate the effect of nutrients on the phytoplankton community structure in the Bohai Sea over the last 30
years. Cell abundance percentages of dominant phytoplankton species with high K
s values for phosphorus and low K
s values for nitrogen have decreased since the 1980s, while those of dominant phytoplankton species with low K
s values for phosphorus and high K
s values for nitrogen increased during this period. 相似文献
14.
Recent observations support an emerging paradigm that climate variability dominates nutrient enrichment in costal eco-systems, which can explain seasonal and inter-annual variability of phytoplankton community composition, biomass (Chl-a), and primary production (PP). In this paper, we combined observation and modeling to investigate the regulation of phytoplankton dynamics in Chesapeake Bay. The year we chose is 1996 that has high river runoff and is usually called a ’wet year’. A 3-D physical-biogeochemical model based on ROMS was developed to simulate the seasonal cycle and the regional distributions of phytoplankton biomass and primary production in Chesapeake Bay. Based on the model results, NO3 presents a strong contrast to the river nitrate load during spring and the highest concentration in the bay reaches around 80 mmol Nm-3 . Compared with the normal year, phytoplankton bloom in spring of 1996 appears in lower latitudes with a higher concentration. Quantitative comparison between the modeled and observed seasonal averaged dissolved inorganic nitrogen concentrations shows that the model produces reliable results. The correlation coefficient r2 for all quantities exceeds 0.95, and the skill parameter for the four seasons is all above 0.95. 相似文献
15.
Water quality model establishment for middle and lower reaches of Hanshui River,China 总被引：2，自引：1，他引：1
With the development of industry and agriculture,nitrogen,phosphorus and other nutrients in the Hanshui River greatly increase and eutrophication has become an important threat to the water quality of the Hanshui River,especially in the middle and lower reaches.The primary objective of this study was to establish the water quality model for the middle and lower reaches of the Hanshui River based on the model of MIKE 11.The main pollutants migration and transformation process could be simulated using the water quality model.The rainfall-runoff model,hy-drodynamic model and water quality model were established using MIKE 11.The pollutants,such as chemical oxygen demand(COD),biochemical oxygen demand(BOD),ammonia nitrogen,nitrate nitrogen,phosphorus,dissolved oxy-gen(DO),were simulated and predicted using the above three models.A set of methods computing non-point source pollution load of the Hanshui River Basin was proposed in this study.The simulated and observed values of COD,BOD5,ammonia,nitrate,DO,and total phosphorus were compared after the parameter calibration of the water quality model.The simulated and observed results match better,thus the model can be used to predict water quality in the fu-ture for the Hanshui River.The pollution trend could be predicted using the water quality model according pollution load generation.It is helpful for government to take effective measures to prevent the water bloom and protect water quality in the river. 相似文献
16.
In the mid-eastern China,there are few or no lakes which are in the absence of anthropogenic disturbances,or their sediments remain undisturbed.As a result,the reference lakes distribution and paleolimnological reconstruction approaches usually are inappropriate to estimate lake reference conditions for nutrients.This yields the necessity of using the extrapolation methods to estimate the lake reference conditions for nutrients within those regions.The lake reference conditions for nutrients could be inferred inversely from the law of mass conservation,current lake nutrient concentration,and the loadings from watershed.Considering the scarcity of hydrological and water quality data associated with lakes and watersheds in China,as well as the low requirement of the watershed nutrient loadings models for these data,the soil conservation service(SCS) distributed hydrological model and the universal soil loss equation(USLE) were applied.The SCS model simulates the runoff process of the watershed,thereby calculating dissolved nutrients annually.The USLE estimates the soil erosion and particulate nutrients annually in a watershed.Then,with the loadings from atmospheric deposition and point source,the previous annual average nutrient concentrations could be acquired given the current nutrient concentrations in a lake.Therefore,the nutrient reference conditions minimally impacted by human activities could be estimated.Based on the proposed model,the reference conditions for total nitrogen and total phosphorus of Chaohu Lake,Anhui Province,China are 0.031 mg/L and 0.640 mg/L,respectively.The proposed reference conditions estimation model is of clear physical concept,and less data required.Thus,the proposed approach can be used in other lakes with similar circumstances. 相似文献
17.
Seasonal variation in abundance and species composition of a planktonic diatom assemblage distributed in the water column and also settled on the bottom was investigated for the shallow coastal water in Matsushima Bay on the Pacific coast of northeastern Japan during the period from October 1999 to September 2000. A spring bloom of diatoms began in April when nutrient concentrations started to increase, indicating the importance of nutrients. Viable cells of Skeletonema costatum and Thalassiosira spp., which were the dominant species in the water column throughout the year, were also always abundant in the bottom sediment. Both populations in the water column and on the bottom fluctuated essentially in parallel. For the planktonic diatoms in shallow coastal waters to maintain their vegetative populations in the water column, it would be advantageous for them to have a seeding population of viable cells on the bottom that are easily resuspended into the upper photic layer. 相似文献
18.
Are there some relationships among species diversity and soil chemical properties of high altitude natural grasslands？ Plant community composition and chemical properties of soil samples were compared to investigate the relationship between soil and species diversity, and the richness in Tibetan alpine grasslands. Results showed that species diversity was significantly positively related to soil organic matter （SOM）, total nitrogen （TN）, available nitrogen （AN）, total phosphorus （TP）, available phosphorus （AP）, and available potassium （AK） in the high alpine grasslands. Margalefs species richness index was also significantly positively related to SOM, TN, AN, and TP. Most soil chemical properties showed significantly positive correlation with species diversity and Margalef＇s richness index. Our results suggested that higher plant species richness index and diversity occurred in more fertile soil habitats in high altitude natural grassland community. In practice, fertilization management for the restoration of degraded grassland should be conducted with reference to the nutrient levels ofnatural grassland without the additional artificial fertilizer and with higher species-diversity and richness index. 相似文献
19.
湖泊富营养化是当前全球范围内最为典型且严重的水环境问题之一，但过去偏重营养盐向湖泊的点源和面源输入评价，常常忽视地表水-地下水相互作用在湖泊水质形成与演化中的作用。总结了地下水-湖水相互作用模式，重点评述了地下水排泄过程对湖泊水文与水质影响的研究进展，对比了渗流仪测量、水量平衡、氡质量平衡、温度示踪、数值模拟等量化方法的优劣性与适用性，探讨了地下水向湖泊排泄的时空变异性、地下水-湖水界面氮磷的迁移转化等难点问题的研究现状，提出该领域未来研究方向主要包括:综合运用多种技术方法，表征湖底地下水排泄的时空变异性；揭示界面水文生物地球化学过程，量化地下水向湖泊排泄氮磷负荷；评估强烈人类活动改造对地下水-湖水相互作用的影响。 相似文献
20.
Gracilaria asiatica,being highly efficient in nutrient absorption,is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate.It was cultured in a laboratory simulating field conditions,and its nutrient absorption was measured to evaluate effects of environmental conditions.Ammonia nitrogen(AN),nitrate nitrogen(NN),total inorganic nitrogen(TIN),and soluble reactive phosphorus(SRP) uptake rate and removal efficiency were determined in a 4×2 factorial design experiment in water temperatures(T) at 15℃ and 25℃,algae biomass(AB) at 0.5 g/L and 1.0 g/L,total inorganic nitrogen(TIN) at 30 μmol/L and 60 μmol/L,and soluble reactive phosphorus(SRP) at 3 and 6 μmol/L.AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN,NN,TIN,and SRP(P<0.001).G.asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L.Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations;nutrient removal efficiency decreased at higher environmental nutrient concentrations.The algae preferred to absorb AN to NN.Uptake rates of AN,NN,and SRP were significantly affected by temperature(P<0.001);uptake rate was higher for the 25℃ group than for the 15℃ group at the initial experiment stage.Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups(P<0.01).The four factors had significant interactive effects on absorption of N and P,implying that G.asiatica has great bioremedial potential in sea cucumber culture ponds. 相似文献