Soluble Reactive Phosphate Research Articles

Assessing land use and land cover influence on surface water quality using a parametric weighted distance function

Stream water quality is directly influenced by land use and human practices in the surrounding environment. Understanding such effects and the spatial extent of impacts is essential to generate reliable information for ecosystem-based management of water resources. We identified sources of impact on water quality and characterized indicator-specific landscape influence on samples collected during base flow along the Chubut River (43 °S, 69 °W). We modeled Total Nitrogen (TN), Total Phosphorous (TP), Soluble Reactive Phosphorous (SRP) concentrations and δ15N of particulate organic matter along the river, as a function of effective contribution areas (AEC) of Land Use/Land Cover (LULC). AECs were calculated by assuming that landscape influence decays exponentially with the Euclidean distance between a given LULC parcel and the sampling point. We calibrated the model to the observations by estimating an indicator-specific decay rate. Agriculture and barren lands were the main sources of phosphate nutrients whereas urban areas were the main source of TN. Radius of landscape influence for SRP (100–180 km) was larger than for TP (10–25 km), reflecting different patterns of mobilization and delivery in the catchment. δ15N variation was explained by vegetation cover but the influence rapidly decreased (1–4 km) reflecting a mostly autochthonous source of organic matter.

Nutrient release from sediments and biological nitrogen fixation: Advancing our understanding of eutrophication sources in Lake Victoria, Tanzania

AbstractIntensification of anthropogenic activities in the three riparian countries bordering the shoreline of Lake Victoria is exacerbating eutrophication in the main body of the lake. The present study evaluated the importance of sediments and biological nitrogen fixation as sources of nutrient enrichment into Lake Victoria in Magu, Mwanza and Kayenze bays influenced by different anthropogenic activities, over a period of 7 months. Kayenze Bay is a relatively pristine site, while higher anthropogenic activities occur in the Magu Bay and Mwanza North Bay areas. Sediment cores were retrieved from each sampling site and transported to the laboratory for nutrient concentrations and flux analyses. In situ nitrogen fixation rates also were measured in the water column. The results indicated the sediment–water interface in Magu Bay exhibited significantly higher concentrations of nitrate‐N and a net release of nitrate‐N, compared to Mwanza North Bay and Kayenze Bay (p < 0.001). The sediment–water interface in Magu Bay also exhibited a significant net release of total phosphate towards the water column, compared to Mwanza Bay (p < 0.001). The sediment–water interface in Mwanza North Bay exhibited higher ammonium‐N concentrations, and net release of ammonium‐N and total nitrogen than did Magu and Kayenze Bays (p < 0.001). The sediment–water interface in Mwanza and Magu Bays exhibited higher total nitrogen and soluble reactive phosphate concentrations than Kayenze Bay (p < 0.001). Their sediments also released net fluxes of soluble reactive phosphate to the water column than did Kayenze Bay (p < 0.001). In contrast, the Kayenze Bay sediments acted as a sink of ammonium‐N from the water column, compared to Mwanza North and Magu Bays (p < 0.001). Biological nitrogen fixation rates were significantly higher during the rainy season than the dry season (p < 0.05), although no spatial variations in biological nitrogen fixation existed among the three sites (p > 0.05). The present study indicated the water column and sediments in Magu Bay and Mwanza North Bay, characterized by high anthropogenic activities are rich in nitrate‐N, ammonium‐N, total nitrogen and soluble reactive phosphate, compared to the relative pristine Kayenze Bay. Anthropogenic activities and sediments may well be important sources of nutrients enrichment to the overlaying waters, thereby enhancing eutrophication of Lake Victoria. Management strategies are required to reduce external releases and internal nutrient fluxes to enhance the lake ecosystem health.

Metagenomic Evidence of Microbial Community Responsiveness to Phosphorus and Salinity Gradients in Seagrass Sediments.

Sediment microorganisms can have profound influence on productivity and functioning of marine ecosystems through their critical roles in regulating biogeochemical processes. However, the identity of sediment microorganisms that mediate organic matter turnover and nutrient cycling in seagrass sediments is only poorly understood. Here, we used metagenomic sequencing to investigate shifts in the structure and functioning of the microbial community of seagrass sediments across a salinity and phosphorus (P) availability gradient in Shark Bay, WA, Australia. This iconic ecosystem is oligotrophic and hypersaline with abundant seagrass meadows that directly contribute Shark Bay’s status as a World Heritage Site. We show that sediment phosphonate metabolism genes as well as enzyme activities increase in hypersaline conditions with lower soluble reactive phosphate in the water column. Given that sediment organic P content is also highest where P concentrations in the water column are low, we suggest that microbial processing of organic P can contribute to the P requirements of seagrasses at particularly oligotrophic sites. Seagrass meadows are often highly productive in oligotrophic waters, and our findings suggest that an increase in the functional capacity of microbial communities in seagrass sediments to break down organic P may contribute to the high productivity of seagrass meadows under oligotrophic conditions. When compared to soil and sediment metagenomes from other aquatic and terrestrial ecosystems, we also show microbial communities in seagrass sediments have a disproportionately high abundance of putative phosphorus and sulfur metabolism genes, which may have played an important evolutionary role in allowing these angiosperms to recolonize the marine environment and prosper under oligotrophic conditions.

Flow cytometry-based evaluation of the bacterial removal efficiency of a blackwater reuse treatment plant and the microbiological changes in the associated non-potable distribution network

The study evaluated the changes in bacterial numbers across a full-scale membrane bioreactor (MBR) blackwater reuse system. Flow cytometry was used to quantify total and intact bacterial concentrations across the treatment train and during distribution of the recycled water. Membrane passage reduced bacterial numbers by up to 5-log units resulting in coliform-free permeate. A 2-log increase in bacterial cell concentration was subsequently observed after the granular activated carbon unit followed by a reduction in intact cells after chlorination, which corresponds to an overall intact bacteria removal of 3.4-log units. In the distribution network, the proportion of intact cells greatly depended on the free chlorine residual, with decreasing residual enabling regrowth. An initial target of 0.5 mg L−1 free chlorine ensured sufficient suppression of intact cells for up to 14 days (setting the time intervals for system flushes at times of low water usage). Bacterial regrowth was only observed when the free chlorine concentration was below 0.34 mg L−1. Such loss of residual chlorine mainly applied to distant points in the distribution network from the blackwater reuse treatment plant (BRTP). Flushing these network points for 5 min did not substantially reduce cell numbers. At points closer to the BRTP, on the other hand, flushing reduced cell numbers by up to 1.5-log units concomitant with a decreasing proportion of intact cells. Intact cell concentrations did not correlate with DOC, total nitrogen, or soluble reactive phosphate, but it was shown that dead biomass could be efficiently converted into new biomass within seven days.

Tile Drainage and Anthropogenic Land Use Contribute to Harmful Algal Blooms and Microbiota Shifts in Inland Water Bodies.

Freshwater harmful algal blooms (HABs), driven by nutrient inputs from anthropogenic sources, pose unique risks to human and ecological health worldwide. A major nutrient contributor is agricultural land use, specifically tile drainage discharge. Small lakes and ponds are at elevated risk for HAB appearance, as they are uniquely sensitive to nutrient input. HABs introduce exposure risk to microcystin (MC), hepatotoxic and potentially carcinogenic cyanotoxins. To investigate the impact of anthropogenic land use on small lakes and ponds, 24 sites in central Ohio were sampled over a 3-month period in late summer of 2015. MC concentration, microbial community structure, and water chemistry were analyzed. Land use intensity, including tile drainage systems, was the driver of clustering in principle component analysis, ultimately contributing to nutrient deposition, a driver of HABs. Relative abundance of HAB-forming genera was correlated with elevated concentrations of nitrate and soluble reactive phosphate. One location (FC) showed MC concentrations exceeding 875 μg/L and large community shifts in ciliates (Oligohymenophorea) associated with hypoxic conditions. The prokaryotic community at FC was dominated by Planktothrix sp. These results demonstrate the impact of HABs in small lakes and ponds, and that prevailing issues extend beyond cyanotoxins, such as cascading impacts on other trophic levels.

Ecosystemic Assessment of Surface Water Quality in the Virilla River: Towards Sanitation Processes in Costa Rica

Water quality information is essential supporting decision making in water management processes. The lack of information restricts, at some point, the implementation of adequate sanitation, which is still scarce in developing countries. In this study, an ecosystemic water quality assessment was conducted in the Virilla river in Costa Rica, in a section of particular interest for future sanitation development. It included the monitoring of physical, chemical, microbiological and benthic macroinvertebrate parameters from 2014 to 2016. Mutivariate statistics and water quality indexes were used for data interpretation. Results indicated that water quality decreased downstream towards more urbanised areas. Particularly, extreme values of phosphorous, nitrogen and E. coli were found. Sample sites were grouped in two clusters, which were consistent with land use. Benthic macroinverterbrates diversity was predominantly represented by Baetidae, Chironomidae, Leptohyphidae, Hydropsychidae, Simuliidae and Physidae. They were mostly influenced by water temperature, nitrite, ammonium, soluble reactive phosphorous, total solids, alkalinity, nitrate and total suspended solids. Three water quality indexes consistently showed the poor condition of the water body. The overall results indicate that the main sources of pollution in the river are likely to be wastewater discharges. Thus, special efforts should be undertaken regarding its regulation in the country.

Cyanotoxins in small artificial dams in Kenya utilised for cage fish farming – a threat to local people?

Nine small artificial dams located in different climatic regions of Kenya were studied. The local communities use the stored water for various purposes, such as irrigation, domestic use, watering of livestock and cage fish farming. Such intense use is commonly accompanied by eutrophication, including fast growth of cyanobacteria, which at times produce cyanotoxins threatening human and animal life. We studied the pelagic community, analysed abiotic variables and identified microcystins by means of high performance liquid chromatography and ELISA kits at monthly intervals over a period of one year. Mass spectrometry (MALDI-TOF MS) was used to identify structural variants of microcystins by their protonated masses (M + H). Three dams contained microcystins, with the highly toxic Microcystin-LR being identified as the most prominent substance. Cell content of the toxin varied from 7.2 to 686.7 fg cell−1. Basic limnological variables that indicate the probability of toxin presence were also recorded. Non-parametric Mann–Whitney U-test revealed significant differences in soluble reactive phosphorous, nitrate-N, water depth, total hardness and post-Nauplii stages sampled between toxin-producing and non-toxin-producing dams. Although most of the samples did not contain high amounts of cyanobacteria, the cyanotoxin-problem was evident, suggesting the need for regular cyanotoxin monitoring programs.

Water quality of inlets’ water bodies in a growing touristic barrier reef Island “Isla Holbox” at the Yucatan Peninsula

Holbox Island faces issues related to the availability of freshwater and living space given the increasing coastal migration and tourism development in the region. We report the water quality of 12 tidal inlets (which are geomorphological features of barrier islands), which neighbor hotels. Because no previous studies of tidal inlets exist on Holbox, we used reference published values of water quality and unpublished water values collected at 43 sampling sites throughout the Yalahau Lagoon. Analyses of water quality variables and the trophic index (TRIX) were measured. Inlets sites salinity values ranged from 11 to 36 psu. Average values for nitrates (0.83 μmol l−1), and nitrites (0.14 μmol l−1), at inlets, had lower values in the fronts season. Soluble reactive phosphate (48.8μmol l−1), and silicate (78.6 μmol l−1) were higher at inlets during rains and chlorophyll-α (29.7 mg/m3) was more top at inlets during fronts. TRIX values for inlets ranged between 2 and 6, indicating low water quality in most inlets associated with hotel sites. Seasonal changes in soluble reactive phosphate and chlorophyll-α at inlets suggests these could be receiving sewage water discharges from human activities. Besides inlet’s higher water residence time and slower water interchange rate can favor the accumulation of pollutants. Results demonstrate that water quality issues exist on Holbox and need management actions to prevent the decay of coastal ecosystem services. These are necessary for positive feedback between local communities’ wellbeing and successful tourism development in the region.

Effect of no carbohydrate addition on water quality, growth performance and microbial community in water-reusing biofloc systems for tilapia production under high-density cultivation

A 56-day experiment was conducted to investigate the effect of no carbohydrate addition applied to control water quality in water-reusing biofloc systems for tilapia (GIFT Oreochromis niloticus) cultivation. Reusing water-contained flocs was initially inoculated into six 300 L indoor tanks. Thirty fish (average individual weight 99.62 ± 7.34 g) were stocked in each tank. Glucose was extra added into three tanks (GLU-tanks) according to biofloc technology, while other tanks were no carbohydrate added (NCA-tanks). Concentrations of total ammonia nitrogen in GLU-tanks and NCA-tanks were fairly consistent and below 4.74 ± 0.35 mg/L. Nitrite concentrations in NCA-tanks were significantly lower than GLU-tanks, which were below 0.59 ± 0.10 mg/L during the later culture period. NCA-tanks achieved a low relative abundance of denitrifiers and high concentrations of nitrate. Soluble reactive phosphorous in NCA-tanks was consistently increased, which was decreased to a low level in GLU-tanks. However, growth parameters in NCA-tanks were similar to GLU-tanks (p > .05) and reach a high finial density of 24.32 ± 1.04 kg/m3. Cetobacterium sp. was the first-dominant bacterial genus in all tanks, which was a commonly indigenous bacterium in the intestinal tract of freshwater fish. The results demonstrate the feasibility of no carbohydrate addition in water-reusing biofloc systems for tilapia.

Phosphate Adsorption by Montmorillonites Modified with Lanthanum/Iron and a Laboratory Test using Water from the Jacarepaguá Lagoon (RJ, Brazil)

Montmorillonites modified with lanthanum(III) and iron(III) were prepared from two commercial clays. These materials were characterized by powder X-ray diffraction analysis, X-ray fluorescence, infrared spectroscopy, N2 adsorption, and scanning electron microscopy. The incorporation of lanthanum(III) and iron(III) varied from 0 to 4.00%. The amount of these cations governed the adsorption capacity of the material since an increase in the percentage of La by 1.7 times improved the adsorption capacity by 3.3 times. The structural properties of the precursor clay minerals, such as pore size, may have influenced the extension of the modification process. Kinetics and equilibrium studies indicated that adsorption occurs mainly within 24 h, and the pseudo-second order and Lagmuir models described the process. The phosphate adsorption capacity ranged from 2.86 to 17.86 mg g-1 for the modified materials and was mainly dependent on the La content. A laboratory test with a natural water sample from the Jacarepagua Lagoon showed reduction of the soluble reactive phosphorus concentration from 0.41 to 0.04 mg L-1, for the material with 4.00% La2O3. The materials described in this work were effective for the reduction of the soluble reactive phosphate, contributing to the research of a national product destined to the restoration of eutrophic aquatic environments.

Natural nutrient enrichment and algal responses in near pristine micro-estuaries and micro-outlets

Naturally-occurring pristine estuarine ecosystems are rare in modern environments due to anthropogenic encroachment. There are more than 100 outlets around the South African coast arising from streams flowing from small catchments close to the sea. Eight near natural systems were sampled seasonally over the period of a year to acquire baseline information on water quality and chlorophyll a status across a variety of algal guilds (benthic microalgae, phytoplankton and macroalgal cover). Albeit on a much smaller-scale, these systems represent natural surrogates of larger temporarily open/closed estuaries (TOCEs). Inorganic nutrients (ammonium, total oxidized nitrogen and soluble reactive phosphate), phytoplankton and microphytobenthos chlorophyll a, as well as macroagal percentage cover, were measured using standard methods. Algae showed a seasonal trend, with blooms of both micro- and macro-algae occurring during summer, with a dieback recorded in autumn. During summer, only one system had a phytoplankton peak in chlorophyll a above 20μgL−1, while the microphytobenthos concentrations in three of the systems were above 100mgm−2. Summer blooms of green filamentous macroalgae occurred in all four micro-outlets and in one micro-estuary. Using a linear mixed-effects modelling approach, significant drivers for algal growth related to temperature, nutrient conditions, light availability and water residence time, all of which are known to stimulate primary production. The results show that enrichment from natural sources display similar responses from primary producers to mesotrophic and/or eutrophic water bodies, with the exception that they revert to a natural state rather than continue into a degraded state as is the case in artificially enriched systems. This importantly demonstrates how larger temporarily/open closed estuaries, most of which are anthropogenically degraded, might have functioned under a former more balanced state. Some of these larger systems now respond to nutrient enrichment by exhibiting permanent cultural eutrophication.

Harmful Algae Bloom Occurrence in Urban Ponds: Relationship of Toxin Levels with Cell Density and Species Composition.

Retention ponds constructed within urban watershed areas of high density populations are common as a result of green infrastructure applications. Several urban ponds in the Northern Kentucky, USA area were monitored for algal community (algae and cyanobacteria) from October 2012 to September 2013. Many of the harmful algal blooms observed during this study were composed primarily of the cyanobacteria genus, Microcystis. No correlations were observed between basic water quality parameters (dissolved oxygen, pH, conductivity, temperature, nitrate and soluble reactive phosphate) and the presence of cyanobacteria and/or microcystin cyanobacterial toxin levels. Furthermore, levels of microcystin toxins did not always coincide with high Microcystis cell counts. Harmful algal blooms in small urban ponds are common which pose risk to human and ecological health due to proximity of dense human population including pets and wild animals. Because harmful algal blooms were detected throughout the year in this study, adaptation of universal guidelines for the design, construction and maintenance of urban ponds may be necessary to protect watershed aquatic ecosystems, and lower health risks from exposure to such harmful blooms.

In Situ Benthic Nutrient Flux and Sediment Oxygen Demand in Barnegat Bay, New Jersey

Wilson, T. and DePaul, V., 2017. In situ benthic nutrient flux and sediment oxygen demand in Barnegat Bay, New Jersey. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey.The U.S. Geological Survey, in cooperation with the New Jersey Department of Environmental Protection, measured sediment oxygen demand (SOD) and benthic nutrient fluxes throughout Barnegat Bay, New Jersey. SOD was determined in situ using chambers equipped with optical dissolved oxygen sensors. The benthic nutrient fluxes of ammonia (NH3), nitrite nitrate ( plus ions; here, referred to as NO32), soluble reactive phosphorous (SRP), and dissolved silica (SiO2) were measured with in situ equilibrium dialysis samplers. Measurements were made at nine stations around the periphery and at three mid-Bay locations from August 2012 to October 2013. The SOD ranged from −1.5 to −8.4 g of oxygen (O2) m−2 d−1. The SOD rates varied as a function of water temperature and followed the van't Hoff rate equation for change in reaction rate with temperature, with a temperature coefficient (Θ) that varied among sites and averaged 1.083. The highest SOD rates in the bay were measured near the mouth of the Toms River embayment. Concentrations in the upper 1 m of sediment pore water were found up to 23 mg N L−1 for NH4 and 6.7 mg P L−1 for SRP. Maximum measured fluxes into the overlying water were 3.0 × 10−2 g NH3–N m−2 d−1, 7.0 × 10−4 g NO32–N m−2 d−1, 1.9 × 10−3 g P m−2 d−1, and 3.6 × 10−3g SiO2 m−2 d−1. Using the measured benthic N and P fluxes, daily nutrient inputs derived from sediment recycling are shown to be comparable in scale to freshwater tributary inputs to the bay.

Coastal Acidification as Nutrients Over Enrichment Impact: A Case Study in Ambon Bay, Indonesia

Ambon Bay is a silled bay on Ambon Island consisting of two regions, Inner Ambon Bay (IAB) and Outer Ambon Bay (OAB) that are separated by shallow sill. Ambon bay and its surrounding have economically important ecosystem since the utilization for many activities. The bay is affected by anthropogenic impacts associated with urbanization, climate change, and nutrients over enrichment. The “deep water-rich nutrients” from Banda Sea that enter the bay during Southeast monsoon also contribute to this enrichment as well as the nutrients transport from the land. The high concentration of nutrients increases carbon dioxide level and promotes acidifications. There are literatures about nutrients over enrichment in Ambon Bay, however, little is known about coastal acidification as nutrients over enrichment impact. In order to study the effect of nutrients distribution on the acidity of Ambon Bay, the researchers measured pH and concentrations of nutrients {nitrate + nitrite (N+N) and Soluble Reactive Phosphate (SRP)} from water samples collected in 7 stations on both IAB and OAB during Southeast monsoon. The results showed that in surface water, nutrients concentrations is increased from May to June due to the “deep water flushing” occurrence on May and increased precipitations from May to June. From July to August, the nutrients concentrations on surface layer decreased, due to the decreased precipitations. In column and bottom water, the nutrients concentrations were increased from May to August. While the acidity have reverse pattern from the nutrients, when nutrient concentrations increased the acidity was decreased. From correlation test, pH was not significantly correlated with the concentrations of nutrients on surface water, but showed significantly correlated on column and bottom water. The results indicated that the distribution of nutrients on column and bottom water might be an important environmental factor affecting the acidification of the Ambon Bay in Southeast monsoon.

Impact of raking and bioturbation-mediated ecological manipulation on sediment-water phosphorus diagenesis: a mesocosm study supported with radioactive signature.

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive 32P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6-28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5-12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Sewage pollution: genotoxicity assessment and phytoremediation of nutrients excess with Hydrocotyle ranunculoides.

The discharge of sewage effluents into low-order streams has negative effects on water quality. Macrophytes can be efficient in the treatment of this wastewater due to the removal of the main pollutants. The genotoxicity of sewage-polluted water discharging into La Choza stream was evaluated by testing with Allium cepa. Also, a phytoremediation assay with continuous recirculation of the residual water was conducted for 12days. Three treatments were carried out. One treatment (Hr) was performed with a macrophyte (Hydrocotyle ranunculoides), and two treatments were conducted without macrophytes: with lighting (Ai) and without lighting (Ao). The wastewater was toxic according to all the evaluated indexes (mitotic index, frequency of chromosomal aberrations and micronucleus). High concentrations of ammonium, dissolved inorganic nitrogen (DIN), total (TP) and soluble reactive phosphorous (SRP) and indicators of faecal contamination were determined in the wastewater. The ammonium, DIN, SRP and TP loads at the end of the assay were significantly lower in the treatments with light (Hr and Ai). So, the nutrient removal was due to their absorption and adsorption by the periphyton and H. ranunculoides. Our results lead us to recommend the maintenance and planting of macrophytes in lowland streams subject to sewage pollution.

Simulation on phosphorus release characteristics of Poyang Lake sediments under variable water levels and velocities

Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the disturbance intensity to sediments, which caused the increase of suspended solids (SS) concentration, total phosphorus (TP) concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well: when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4.86 mg/(md) at 0.4 m/s. The concentration of total dissolved phosphorous (TDP) and soluble reactive phosphate (SRP) both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.

Preservation of seawater samples for soluble reactive phosphate, nitrite, and nitrate plus nitrite analyses by the addition of sodium hydroxide

AbstractSeawater storage at ambient temperature is necessary when freezing facilities are unavailable for the preservation of samples collected for the determination of soluble reactive phosphate (SRP), nitrite ( ), and nitrate plus nitrite (N + N)—notably, during small boat operations. Here, we report that samples may be preserved at ambient temperature by the addition of NaOH at sampling to induce the precipitation of Mg(OH)2, and then returned to a shore base laboratory for further processing. In the laboratory, SRP, which has been sequestered in the precipitate, is analyzed by the MAGnesium‐induced co‐precipitation method. and N + N are quantitatively retained in the supernatant liquid and they are analyzed by the standard methods after a pH adjustment. The samples may be stored for up to at least 2 months and they yield concentrations that are indistinguishable from those in frozen samples. Internally added SRP, , and N + N to seawater samples can be recovered quantitatively after storage. This storage method also offers clear advantages over the preservation of samples at ambient temperature by the addition of HgCl2 as NaOH is a less toxic and less environmentally hazardous chemical and it does not interfere in the determination of N + N. It also allows low level SRP to be determined as part of the analytical routine as a pre‐concentration of SRP has been built into the storage scheme.

Indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental change in marine ecosystems

The indication of spatial variations in annual cycles of functional groups of planktonic ciliates to environmental changes was studied in a bay, northern Yellow Sea. Samples were biweekly collected at five stations with different hydrographic conditions during a 1-year cycle. The second-stage-matrix-based multivariate approach was used to summarize the internal interactions of the ciliate functional groups among five stations during a 1-year period. The functional groups of the ciliates represented a clear spatial variation in annual cycle among five stations. Mantel analysis demonstrated that the spatial variation in annual cycles of the ciliate functional groups were significantly correlated with the changes nutrients (mainly soluble reactive phosphates and nitrates), alone or in combination with salinity among five stations. Based the results, it is suggested that the spatial variation in annual cycles of functional groups of planktonic ciliates may indicated the changes of hydrographic conditions.

Speciation and Mobility of Phosphate in the Eutrophic Ponds at Prospect Park, Brooklyn, New York, USA

The water system at the Prospect Park ponds of Brooklyn, NY has been receiving chronic loads of orthophosphate from the municipal water since the mid ’90s. The ponds are currently eutrophic with degraded water quality and high levels of P in the sediment. In this study, the distribution and speciation of P within the water column was examined. The dominant form of P in the water was found as soluble reactive phosphate (SRP) and the temporal change of SRP indicated significant internal loading from the sediment during late summer in the ponds downstream. Lake sediment was investigated for P fractionation and phosphate bound to Fe-hydroxides was the dominant form of P in the sediment. Both external and internal P pools are important and should be taken into consideration when planning for restoration.