Seasonal Variations Of Nutrients Research Articles

Comparison of nutrients status in Liaodong Bay and Northern Yellow Sea, China: Controlling factors and nutrient budgets

Under the dual stress of global warming and human interaction, Liaodong Bay (LDB) and northern Yellow Sea (NYS) are undergoing significant ecological changes. Little is known about the driving nutrients characteristics supporting fishery resource output in these areas. We carried out three field observations in 2019 to investigate nutrient status. Results showed that dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silica (DSi) concentrations changed seasonally, with lowest values in spring, and highest values in autumn. High DIN, DIP, and DSi concentrations were detected in LDB and NYS's estuary areas. The Yellow Sea Cold Water Mass plays a role in the distribution and seasonal variation of nutrients. Exchanges across the sediment-water interface, SFGD, atmospheric deposition, and the adjacent sea input dominated DIN dynamics of these areas. DIP primarily came from the adjacent sea input and DSi mainly originated from sediment release and the adjacent sea input. NYS seawater invasion accounted for 13.8% of DIN, 63.4% of DIP, and 35.1% of DSi in LDB. These results provide new insights to better facilitate the formulation of nitrogen and phosphorus reduction and control policies in these marginal seas.

Efficient removal of nitrogen and organic matter strategy from landfill leachate under high seasonal substrate variations

Landfill leachate is commonly used as a co-substrate in aerobic granular sludge (AGS) systems due to its high nitrogen concentration and variable organic matter content, which have a substantial impact on the removal efficiency. Typically, the nutrient content and biodegradability of leachate are categorized based on landfill age, often overlooking important factors such as seasonal variations. To address this limitation, a two-step process consisting of an anaerobic digestion (AD) reactor followed by an AGS reactor was evaluated over 431 days. Landfill leachate from the winter and spring seasons was chosen for its favorable biodegradability characteristics.Raw landfill leachate assays revealed a biodegradability range of 25%–92% within a single year, with higher values observed during winter compared to summer. To effectively handle the nutritional variations of landfill leachate, the hydraulic retention time (HRT) emerged as a crucial parameter influencing the performance of the reactors. When the AD reactor was operated in a hydrolytic configuration with an OLR of 68.4 g COD L−1 d−1, the proposed system showed 76.9% and 78.3% of organic matter and nitrogen removals, respectively. Best performance was obtained with COD/N 6.30 in the influent, ensuring required conditions for anoxic reactions (denitrification) at the center of the AGS.The proposed system offers valuable design tools for effectively removing nitrogen and organic matter from landfill leachates, despite significant seasonal nutrient variations. This approach can also be applied to wastewater with organic and nitrogen variations to face organic matter fluctuations in the AD and nitrogen fluctuations in the AGS.

Seasonal Variation of Nutrients that Influence the Growth of Cyanobacteria in Surface Water Reservoirs of River Tapi

Seasonal Variation of Nutrients that Influence the Growth of Cyanobacteria in Surface Water Reservoirs of River Tapi

Spatial-temporal distribution of carbon, nitrogen and phosphorus concentrations and eutrophication evaluation of mountainous small river in a cascaded damming

梯级筑坝对河流水环境演化的影响是国内外关注的热点.小型山区河流高密度梯级开发对水体生源要素的空间格局以及水环境演化的累积影响特征尚不清楚.以重庆市五布河为研究对象，对流域内8个“河流-水库-下泄水”交替系统中表层水体理化因子及碳（C）、氮（N）、磷（P）形态组成进行季节性监测，探讨了梯级筑坝对小型河流生源要素空间格局及水体富营养化风险影响的累积特征及驱动机制.结果表明：梯级水电开发对五布河流域水生生境和生源要素空间分配的影响具有潜在的累积效应，各库区水体碳氮磷浓度均呈逐级增加的空间规律；水库段的有机碳及不同形态的氮、磷浓度均高于入库河流，因此水体养分浓度呈现出河段尺度（即单个河流-水库-下泄水系统）和流域尺度（即上游至下游）耦合的空间变异模式.上游水库中溶解性氮、磷的再释放及下泄输移能够补给下游库区，加之下游水库泥沙对氮、磷的吸附-沉积作用的减弱，导致水体氮、磷总量及溶解性氮、磷的占比沿程增加，呈现梯级筑坝对水环境演化的累积影响.梯级筑坝影响下河流碳氮磷总量的相关性减弱，而溶解性养分间的相关性增强，形成了特殊的养分协同演化；水库群之间水力滞留时间的差异与水体碳氮磷浓度具有较好的线性关系，是影响流域养分分配的关键因素.五布河流域水体均为高富营养化风险，由于梯级筑坝下水体溶解性养分的逐级增加，下游水库水华风险更大；水力滞留时间与水体富营养化指数及叶绿素a浓度呈显著正向关，结合氮磷比特征的分析，本研究认为外源磷输入控制及水力滞留时间的调节是五布河梯级水库富营养化防控的有效途径.;Rivers, as the channel connecting terrestrial and marine ecosystems and transporting a large amount of nutrients to ocean, are important for maintaining the global material cycle. The construction of cascade dams leads to river fragmentation and changes the distribution of carbon, nitrogen and phosphorus in the water. At present, a lot of studies have been conducted on the ecological effects of cascade development in large rivers, but few studies focus on small mountainous rivers. The spatial-temporal patterns and controls of the distribution of carbon, nitrogen and phosphorus from cascade river-reservoir systems in the small mountainous rivers remain unclear. In this study, we investigated the spatial-temporal variations of carbon(C), nitrogen(N) and phosphorus(P) concentrations along a cascade damming river (Wubu River) in Southwest China. The results showed that carbon, nitrogen and phosphorus showed an obvious cumulative effect, that was, the contents of C, N and P gradually increased from the first reservoir upstream to the last reservoir downstream underlying cascade dams. And, the organic carbon, as well as nitrogen and phosphorus in the reservoir section, were higher than in those inflow rivers. Thus, different forms of carbon, nitrogen, and phosphorus concentration in the reach (river-reservoir-release water system) scale and river basin scale (the upstream to downstream) displayed the double coupling variation pattern. Primary production and plankton proliferation were the main mechanisms of organic carbon accumulation in the river. At the same time, cascade reservoirs may form a series of nitrogen and phosphorus storage tanks and reactors to promote the release and transport of dissolved nitrogen and phosphorus. The re-release and transport of dissolved N and P in the upstream reservoir can replenish the downstream reservoir, increasing the content of N and P in the downstream reservoir and the proportion of dissolved N and P, thus leading to the cumulative effect of water deterioration. The decrease in the adsorption-deposition effect of sediment on nitrogen and phosphorus nutrients in downstream reservoirs also leads to the accumulation of soluble nitrogen and phosphorus concentrations. The correlation of C, N and P in the river was weakened, but there was a significant relationship between dissolved nutrients, forming a special nutrient co-evolution. Furthermore, the hydraulic retention time of the reservoir groups had a good linear relationship with water C, N and P contents, which was the key factor affecting nutrient allocation in the watershed. Seasonal variations of total organic carbon and dissolved organic carbon were highest in spring and lowest in winter in Wubu River Basin. Total nitrogen and nitrate nitrogen in the dry season (winter and spring) were significantly higher than those in the wet season (summer and autumn), and other nutrient forms had no obvious seasonal pattern. Rainfall dilution, algal reproduction, microbial decomposition and re-release were the main processes leading to the seasonal variation of nutrients. The eutrophication risk also presented an increasing trend from upstream to downstream because of the dam. There was also a good linear relationship between hydraulic retention time and eutrophication risk. Combining the analysis of N:P ratio characteristics, it was suggested that exogenous P control and optimal allocation of hydraulic retention time are effective approaches for eutrophication control in the Wubu River Basin.

Can Early-Period Fruit Analysis be Performed for Timely Interventions Against Physiological Disorders In Apple Trees?

Apple is grown in various parts of the world and consumed year-long in four seasons. The nutrient contents of fruit constitute the bases for several disorders experienced in storages. Although leaf analyses are used worldwide to assess the nutritional status of fruit trees, they may not yield accurate outcomes for assessment of fruit nutrient contents. Even if leaf nutrient contents are enough or quite high, various physiological disorders on fruits may be resulted from nutrient deficiencies. Fruit analyses should be performed to determine fruit nutrient contents and accordingly to improve flesh quality and to take relevant measures in early periods.In this study, fruit samples were collected for 2 years from 260 apple orchards in Isparta province of Turkey in 6 different periods covering the timeframe from June drops to harvest and fruit nutrient contents were determined from these samples. Firstly, seasonal variations of nutrients were examined. It was observed that fruit nutrient contents decreased periodically and this decreasing was quite faster through the early periods of the vegetation. Secondly, correlations between nutrient contents of the fruits sampled at the last period and the nutrient contents of the fruits sampled at earlier periods were also investigated in this study. Significant correlations revealed that fruit nutrient contents could be traced between the relevant periods and reference values could be established for these periods. Positive outcomes were observed for investigated nutrients except for N, Fe and Zn.

Climatology of nutrient distributions in the South China Sea based on a large data set derived from a new algorithm

Nutrients are typically the most important determinant of the productivity of marine ecosystems. Hence, nutrients have been an essential variable of ocean observations in the modern oceanography era. Understanding of marine ecosystems and biogeochemistry, however, is largely limited by the spatiotemporal coverage of nutrient data. Herein, we developed a novel algorithm based on a large observational dataset of nutrients and their relationship with water masses indexed by temperature and salinity in the South China Sea (SCS). The algorithm yielded errors of ≤ 1.3, ≤ 0.10 and ≤ 3.5 μmol L−1 for NO3– + NO2– (N + N), phosphate and silicate, respectively. It is then applied to reconstruct nutrient concentrations primarily using temperature and salinity data archived in the World Ocean Database and Argo database during 1940–2018. It increases the nutrient data to ~ 5 million, by ca. three orders of magnitude compared to direct measurements in the SCS. This allows for a full examination of the seasonal climatology of nutrients in the SCS. In summer, in the upper 200 m, nutrient concentrations in the northwest and southernmost SCS are higher than in the rest of the SCS. An overall reversed pattern is revealed in winter, when higher nutrient concentrations are found in the central basin rather than basin margins. The Kuroshio intrusion and the vertical displacement of the nutricline, driven by upwelling/downwelling induced by horizontal convergences/divergences at both meso- and basin scales, determine the spatial and seasonal variation of nutrients. Seasonally, the Kuroshio intrusion and vertical displacements of the nutricline tend to offset the spatial variation of nutrient concentrations in spring, while they show an additive effect in the fall.

Spatiotemporal variation of the nutrients and heavy metals in mangroves using multivariate statistical analysis, Gulf of Kachchh (India)

The present study is an attempt to assess the spatial and seasonal variation of nutrients and heavy metals in mangroves water in the Gulf of Kachchh, India. The surface water samples were collected during pre- and post-monsoon to evaluate the hydrochemical processes occurring in the region. Seasonal changes and anthropogenic inputs have influenced the nutrients and metal concentrations. The results suggest high salinity (Pre-monsoon ±45.59 PSU; post-monsoon ±45.36 PSU) and chloride (Pre-monsoon ±30251 mg/L; post-monsoon ±29536 mg/L) concentration in both the seasons. Average values of Sulfate (SO4−), Nitrate (NO3−), Dissolved silica (DSi), and Phosphate (PO43−) was 2503.69 mg/L, 10.47 mg/L, 35.41 mg/L and 0.85 mg/L in pre-monsoon, and 3474.50 mg/L, 13.66 mg/L, 31.54 mg/L and 0.64 mg/L in post-monsoon, respectively. Nutrient ratios indicate phosphorus limitation in both the seasons. Cluster and Principal Component analysis signifies that sampling locations in cluster 3 and factor 1 majorly impacted due to seawater mixing, high evaporation and discharge of brine from saltpans, while cluster 2, 3 and factor 2 indicates the anthropogenic source. Metal concentration was higher during pre-monsoon and among the metals, Fe, Sr, Zn and Mn were observed in high concentration. The hydrochemical characteristics of water found to be dependent on the peculiarity of sampling locations such as high tidal amplitude, less freshwater input, arid climate, extensive saltpans, tidal flushing, instinctive reducing environment and anthropogenic discharge. Gulf of Kachchh is an industrial hub of the country, where anthropogenic activities (such as fertilizer, cement, and chemicals industries, oil and petroleum refineries, metal processing units, thermal power plants and ports activities) are the prime sources of contamination, which are affecting water quality. The relatively high concentration of nutrients and metals suggests that water is in very dreadful condition, which will ultimately affect flora and fauna of this ecosystem. This study provides baseline information on mangrove water quality and impacts of ongoing anthropogenic activities on the Gulf of Kachchh.

Lake warming intensifies the seasonal pattern of internal nutrient cycling in the eutrophic lake and potential impacts on algal blooms

Lake warming induced by climate change has constituted a particular challenge for the restoration of eutrophic lakes. However, a quantitative analysis about impacts of lake warming on the internal nutrient cycling in eutrophic lakes is limited. In this study, monthly nutrient monitoring data set in 2015-2016 in eutrophic Lake Chaohu, China, revealed a regular seasonal pattern of nutrient concentration. A process-based water quality model was established to quantify contributions from internal loadings on seasonal nutrient variations and predict responses under climate change scenarios. Results indicated that internal nutrient loading was responsible for the intra-annual variations of nutrient concentrations in the lake, and the internal loadings fluctuated much more between different seasons than the external nutrient inputs. We predicted that lake warming might probably result in stronger seasonal fluctuations of internal loading and create conditions beneficial for longer duration of cyanobacteria blooms in the year. Evidence derived from this study could help water managers to rethink the existing mitigation strategies in the restoration of eutrophic lakes and emphasize the potential interactions among lake warming, eutrophication and internal nutrient cycling in the future.

Seasonal Water Level Fluctuation and Concomitant Change of Nutrients Shift Microeukaryotic Communities in a Shallow Lake

Seasonal water level fluctuations (WLFs) impose dramatic influences on lake ecosystems. The influences of WLFs have been well studied for many lake biotas but the microeukaryotic community remains one of the least-explored features. This study employed high-throughput 18S rRNA gene sequencing to investigate the spatiotemporal patterns of microeukaryotic communities in the dry and wet seasons with concomitant change of nutrients in Poyang Lake, which experiences huge seasonal WLFs. The results showed that the dry season and wet season had distinct microeukaryotic community compositions and structures. In the dry season, Ciliophora (13.86–40.98%) and Cryptomonas (3.69–18.64%) were the dominant taxa, and the relative abundance of these taxa were significant higher in the dry season than wet season. Ochrophyta (6.88–45.67%) and Chlorophyta (6.31–22.10%) was the dominant taxa of microeukaryotic communities in the wet season. The seasonal variation of microeukaryotic communities was strongly correlated to seasonal nutrient variations. Microeukaryotic communities responded significantly to dissolved organic carbon, total nitrogen, nitrate, and soluble reactive phosphorus in the dry season, and correlated to nitrate and total phosphorus in the wet season. The microeukaryotic community showed different modular structures in two seasons, and nutrient variations were the key factors influencing seasonal variations of the modular structures. Moreover, microeukaryotic community networks based on different seasons indicated that the microeukaryotic community co-occurrence patterns were not constant but varied largely associating with the nitrogen and phosphorus variations under the effects of WLFs. Our results are important for understanding how microeukaryotic communities respond to nutrient variation under seasonal water level fluctuation.

Seasonal Variation of Physico-Chemical Parameters and Their Influence on Phytoplankton Community of Muthupet Estuary, Southeast Coast, Tamil Nadu, India

Physico-chemical parameters of freshwater are most important factor for diversity and density of phytoplankton community. Hence, the present study was intended to evaluate the seasonal variation on physico-chemical parameters such as rainfall, temperature, pH, salinity, dissolved oxygen and their relationship with phytoplankton community of Muthupet estuary. The seasonal variation of nutrients like nitrate, phosphate and silicate was recorded to determine the utilization of nutrients by phytoplanktons in aquatic environment. The results exposed that physico-chemical parameters showed significant difference among the seasons. The nutrient dynamic of Muthupet estuary exhibits considerable seasonal variation due to the rainfall and nutrient utilization of autotrophs. There are totally 14 species of phytoplankton under three different groups namely Bacillariophyceae, Dinophyceae and Cyanophyceae was recorded. The highest phytoplankton density was recorded during summer season (18541.67b ± 3934.52/m3), while lower in monsoon seasons. The statistical analysis of physico-chemical parameters showed significant variation among seasons and the diversity indices of phytoplankton were high during post monsoon for both Simpson and Shannon indices and also on Evenness. The correlation analysis exposed that physico-chemical parameters and nutrients are effective dynamics to control the seasonal variations on phytoplankton diversity. Therefore, the present study reveals that Muthupet estuary has rich in phytoplankton community due to presence of high nutrient content and consisting of appropriate environmental factors.

Microbial community evolution during the aerobic biodegradation of petroleum hydrocarbons in marine sediment microcosms: Effect of biostimulation and seasonal variations

Evolution of the microbial community structure in crude oil contaminated marine sediments was assessed under aerobic biodegradation during wet (18 °C) and dry (28 °C) seasons experiments, to account for seasonal variations in nutrients and temperature, under biostimulation and natural attenuation conditions. NMDS showed significant variation in the microbial communities between the wet and the dry season experiments, and between the biostimulation and the natural attenuation treatments in the dry season microcosms. No significant variation in the microbial community and oil biodegradation was observed during the wet season experiments due to high background nitrogen levels eliminating the effect of biostimulation. Larger variations were observed in the dry season experiments and were correlated to enhanced alkanes removal in the biostimulated microcosms, where Alphaproteobacteria dominated the total microbial community by the end of biodegradation (54%). Many hydrocarbonoclastic bacterial genera showed successive dominance during the operation affecting the ultimate performance of the microcosms.

Seasonal Variations Of Nutrients In Perur Chettipalayam Lake, Coimbatore District, Tamilnadu, India

The water quality was performed in Perur Chettipalayam Lake, Coimbatore District from July 2015 to June 2016, with specific regard to nutrient content. The nutrients investigated were phosphate, calcium,magnesium, chlorides, nitrates and sulphates. The obtained results showed marked seasonal changes incontamination of the sewage pond. The analyzed nutrient content shows that the lake is extremely contaminated with sewage.

Particle-Associated Microbial Community in a Subtropical Lake During Thermal Mixing and Phytoplankton Succession.

Ecosystem dynamics in monomictic lakes are characterized by seasonal thermal mixing and stratification. These physical processes bring about seasonal variations in nutrients and organic matter fluxes, affecting the biogeochemical processes that occur in the water column. Physical and chemical dynamics are generally reflected in seasonal structural changes in the phytoplankton and bacterio-plankton community. In this study, we analyzed, using 16S rRNA amplicon sequencing, the structure of the bacterial community associated with large particles (>20 μm) in Lake Kinneret (Sea of Galilee, Israel), and its associations to phytoplankton populations. The study was carried out during late winter and early spring, a highly dynamic period in terms of thermal mixing, nutrient availability, and shifts in phytoplankton composition. Structural changes in the bacterioplankton population corresponded with limnological variations in the lake. In terms of the entire heterotrophic community, the structural patterns of particle-associated bacteria were mainly correlated with abiotic factors such as pH, ammonia, water temperature and nitrate. However, analysis of microbial taxon-specific correlations with phytoplankton species revealed a strong potential link between specific bacterial populations and the presence of different phytoplankton species, such as the cyanobacterium Microcystis, as well as the dinoflagellates Peridinium and Peridiniopsis. We found that Brevundimonas, a common freshwater genus, and Bdellovibrio, a well-known Gram-negative bacteria predator, were positively associated to Microcystis, suggesting a potentially important role of these three taxa in the microbial ecology of the lake. Our results show that the dynamics of environmental abiotic conditions, rather than specific phytoplankton assemblages, are the main factors positively correlated with changes in the community structure as a whole. Nevertheless, some specific bacteria may interact and be linked with specific phytoplankton, which may potentially control the dynamic patterns of the microbial community.

Seasonal variations in nutrients and biogenic particles in the upper and lower layers of East China Sea Shelf and their export to adjacent seas

Based on a three dimensional low-trophic ecosystem model, we revaluated budgets of nutrients and biogenic particles (phytoplankton and detritus) in the East China Sea (ECS), a continental shelf sea with high productivity that is affected by a large river (Changjiang River) and a western boundary current (Kuroshio). Following careful comparison of model results with available observation data, we calculated the monthly inventories of the nutrients and biogenic particles in the ECS and the fluxes of the nutrients and biogenic particles through the lateral and vertical interfaces of the ECS. As an improvement over previous nutrient budget calculations that treated the ECS as one box, we divided the water column into two layers: upper and lower layers corresponding to different light condition. Seasonal variations in inventories of nutrients and biogenic particles in both upper and lower layers are apparent but present different features, which are related to opposite contributions of biological processes and physical processes in the two layers. Our calculation shows the necessity of evaluating not only the horizontal fluxes of nutrients and biogenic particles into and out of the ECS through lateral boundaries with adjacent seas but also the exchange fluxes of nutrients and biogenic particles between the upper and lower layers because the latter is larger than the former. Our calculation also reveals two major export pathways of biogenic particles generated locally in the ECS: from the ECS to the Japan/East Sea through the Tsushima Strait and from the ECS to the Kuroshio region through the shelf break (200 m isobath). The export amount of biogenic particles is larger through the Tsushima Strait than through the shelf break in the water column. The depth for the biogenic particles exporting through the shelf break of the ECS is the middle layer (from ~60 m to ~160 m).

Spatial and temporal variations of water quality in Pallikaranai wetland, Chennai, India

This paper analysed the spatial-temporal variations of surface water quality of the Pallikaranai wetland, located in the region known as Chennai City. An extensive study pertaining to seasonal variations in nutrients, dissolved carbon, dissolved gases and heavy metals in surface water was studied at 16 locations of Pallikaranai wetland during three seasonal cruises from March 2010 to December 2010. GIS and statistical techniques such as interpolation method (IDW), Pearson correlation and principal component analysis (PCA) were applied to evaluate the spatial pattern and variation in water quality of Pallikaranai wetland and to identify pollution sources. The results revealed that there is a remarkable seasonal variation in the analysed parameters which are attributed to the natural sources (monsoon) and anthropogenic activities. PCA resulted in three factors explaining 73.8% of the total variance. Factor 1 exhibited a high correlation with environmental parameters, nutrients and organic carbon representing the influence of seasonal runoff. Factor 2 envisaged heavy metal pollution results from anthropogenic activities. Factor 3 explored moderate correlation with SPM and nutrients.

Spatial and temporal variations of water quality in Pallikaranai wetland, Chennai, India

This paper analysed the spatial-temporal variations of surface water quality of the Pallikaranai wetland, located in the region known as Chennai City. An extensive study pertaining to seasonal variations in nutrients, dissolved carbon, dissolved gases and heavy metals in surface water was studied at 16 locations of Pallikaranai wetland during three seasonal cruises from March 2010 to December 2010. GIS and statistical techniques such as interpolation method (IDW), Pearson correlation and principal component analysis (PCA) were applied to evaluate the spatial pattern and variation in water quality of Pallikaranai wetland and to identify pollution sources. The results revealed that there is a remarkable seasonal variation in the analysed parameters which are attributed to the natural sources (monsoon) and anthropogenic activities. PCA resulted in three factors explaining 73.8% of the total variance. Factor 1 exhibited a high correlation with environmental parameters, nutrients and organic carbon representing the influence of seasonal runoff. Factor 2 envisaged heavy metal pollution results from anthropogenic activities. Factor 3 explored moderate correlation with SPM and nutrients.

Linkages between hydrology and seasonal variations of nutrients and periphyton in a large oligotrophic subalpine lake

Periphyton is important to lake ecosystems, contributing to primary production, nutrient cycling, and benthic metabolism. Increases in periphyton growth in lakes can be indicative of changes in water quality, shifts in ecosystem structure, and increases in nutrient fluxes. In oligotrophic lakes, conservationists are interested in characterizing the influence of hydrological drivers on excessive periphyton growth along nearshore areas. We collected nutrient samples bi-weekly from groundwater and surface water during a 9-month monitoring period to evaluate the timing and availability of nutrients to eulittoral periphyton in Lake Tahoe. Groundwater discharge rates were measured synoptically using seepage meters and estimated indirectly using continuous head gradient measurements and aquifer properties estimated by slug tests. The discharge measurements made from the seepage meter measurements provide information about the spatial variability perpendicular from shore along and the change in groundwater discharge due to wave action. Algal biomass sampled from substrates and observed using underwater photographs were used to correlate seasonal growth and nutrient concentrations in groundwater and lake water. Results indicate that groundwater and nutrient discharge are temporally variable due to seasonal changes in recharge within the watershed, wave action, and lake stage. Groundwater discharge was enhanced by the seasonally-low lake stage and episodic recharge caused by precipitation falling as rain in the watershed. Increases in dissolved phosphorus and nitrate in the lake during winter are attributed to groundwater discharge and correlates to increases in algal biomass in the nearshore area. Results indicate that nutrient-rich groundwater discharge appears to stimulate seasonal periphyton blooms along the eulittoral zone of Lake Tahoe.

Dynamic Replenishment Process of Nutrients in Tributary of Channel Reservoir

The process of phytoplankton succession and change in primary productivity are directly determined by the seasonal variations in nutrients in tributary bays of channel reservoirs. This study aimed at analyzing the effects of the main nutrient sources on seasonal distribution of nutrients in Xiangxi Bay based on the field data collected in 2010 and 2011. The tracing inorganic ions were Cl- and Na+ that showed significant differences (P<0.01) between the mainstream and the tributary. The nutrient contribution rates of different sources were calculated by the binary linear model. The results showed that the nutrient contribution rate of the mainstream was more than 75% during the dry season and the impoundment period. The intrusion of the mainstream was the main source of nutrients in Xiangxi Bay. The difference in the contribution rates between the mainstream and the upstream decreased during the pre-flood drawdown period and the flood season. The concentration of total phosphorus was higher in the upstream, while the concentration of total nitrogen was higher in the mainstream. The patterns of density currents were different and the nutrient contribution rates of different sources changed accordingly. Therefore, the nutrients of Xiangxi Bay changed regularly in different operation periods of the Three Gorges Reservoir.

Seasonal variation of nutrients and hydrological conditions in the State Marine Park of Laje de Santos (SMPLS) and adjacent continental shelf areas (South Atlantic Ocean - Brazil)

Abstract Marine parks constitute important areas for the conservation of marine life and the genetic heritage around the world. The creation of such marine parks must be accompanied by careful measures to guarantee the coexistence of natural biota and human activities in these systems. The State Marine Park of Laje de Santos (SMPLS) is so close to an industrial pole and urban area that its creation and maintenance is an example for humanity. However, no program has yet been installed for the monitoring of its biotic and abiotic water parameters. Thus, the objective of this study is to provide hydrological and hydrochemical parameters with emphasis on dissolved nutrients to establish a starting point for the monitoring of these waters. The presence of the South Atlantic Central Water (SACW) in the marine park during the spring and summer sampling periods was evidenced by the observation of low temperatures (&lt; 17ºC) associated with salinity around 35 at the bottom of the water column, indicating a thermohaline feature. The dissolved oxygen presented high values, with few data below 4 mL L-1 occurring at the bottom of the water column. The pH was always in accordance with marine values (~8). Dissolved silicate and phosphate presented high values associated with inputs from the SACW intrusion, continental runoff and bottom resuspension processes, reaching maximum values of 15.86 and 1.23 µmol L-1, respectively. Nitrogen compounds were also associated with a natural fertilization process by the presence of the SACW at the bottom of the water column, as evidenced by the high nitrate concentrations (&gt; 7.00 µmol L-1), while the concentration of N-ammonium (maximum 9.86 µmol L-1) demonstrated a rapid regeneration of the organic matter, mainly in the euphotic zone. Analysis of the data from summer periods revealed an annual difference, showing January 2014 to be drier than January 2015, which influenced the availability of some nutrients and the standard distribution of hydrochemical parameters in this region. The results of the distribution of hydrochemical parameters in the marine park confirms the preserved conditions of the seawater around the Laje de Santos, demonstrated by the excellent water quality, concluding the need to implant monitoring actions based on these reference data to preserve this important reserve of marine life.

Seasonal dynamics of nutrients concentration and dissolved oxygen content in the rivers of southern Primorye

Rivers are the main source of terrigenous nutrients to the coastal sea which could be responsible for such adverse impacts as red tides or hypoxia in the estuarine areas. To evaluate the rivers influence on chemical environments in the coastal zone, monitoring of water properties in the rivers of southern Primorye was conducted in 2016 (and continues till nowadays). Retrospective data of chemical measurements on the Razdolnaya, Artemovka, Knevichanka and Ryazanovka rivers in different seasons of 1985 were used for comparison with modern data. Prominent seasonal dynamics of chemical parameters is revealed that generally corresponds to seasonal changes of freshwater discharge caused by monsoon cycle of precipitations. The seasonal dynamics of water temperature is conditioned by climate features of the region and geographic location of the rivers: the temperature at the surface is about 0 о C in February, then rises in spring-summer and decreases in autumn, with the maximum values in August as 26-27 о С for the flat rivers and 18-20 о С for the mountain rivers. The pH variations are conditioned by the carbon dioxide saturation in water, so its level is 6.1-7.2 in winter and 7.4-8.2 in summer. Nutrients, except iron, have the maximum concentration in winter (DIN ~2.5 µM/L, DIP ~0.5 µM/L, silicates ~115.0 µM/L) but the iron concentration is the highest in spring (~0.1 mg/L). However, natural seasonal variation of nutrients is distorted by anthropogenic load for some rivers with industrial and agricultural activity in the basins, including the territories of P.R. China (Suifen/Razdolnaya River): their waters are the richest by nitrogen and phosphorus in summer (DIN ~45.0 µM/L, DIP ~0.5 µM/L) and by dissolved iron in autumn-winter (~0.9-1.3 mg/L). Spatial variability is very similar between all nutrients in any season (correlation coefficients between DIN and Fe concentrations are 0.75-0.99, between DIP and Fe - 0.83-0.99) that means that their growth in the polluted rivers has common nature, presumably a decomposition of organic wastes Being transferred. Transferred to the sea, the nutrient elements of terrestrial origin are converted back to organic matter enhancing the coastal waters productivity, but consequences of this impact are principally different for the natural regime with the winter-spring maximum and for the distorted regime with the summer-fall maximum. Huge oxygen demand determines the lowered DO in the Suyfen/Razdolnaya and Knevichanka in winter. Other rivers of southern Primorye (Ryazanovka, Barabashevka, Kievka, Partizanskaya, Sokolovka, Artemovka) could be considered as «clean» ones, following to Russian standards of water quality. Seasonal variability of oxygen content in their waters is driven by changes of water temperature and photosynthesis. Comparison of the long-term changes in water quality for the rivers Razdolnaya, Artemovka, Knevichanka and Ryazanovka over the last 30 years (relative to 1985) has revealed unfavorable changes of dissolved oxygen content for the Razdolnaya and Knevichanka, whereas the changes are not significant for the Artemovka and the oxygen content has increased for the Ryazanovka. The latter indicates the Ryazanovka water quality improvement that is important since a fish farm is located on the river.