Terms Of Nutrient Concentrations Research Articles

Effect of Water Level Reduction on the Littoral Zone in Terms of Its Efficiency in Lake Protection

Decreased water levels due to climate change cause many negative effects on lake ecosystems. The aim of this study was to (a) assess the effect of the reduction of water levels on nutrient availability in the sediment in the littoral zone; (b) evaluate the effect of changes in water level on biomass productivity and nutrient concentrations in the aboveground biomass of four emergent species: Phragmites australis (Cav.) Trin. ex Steud., Typha angustifolia L., Carex acutiformis L., Glyceria maxima (C. Hartm.) Holmb; and (c) assess the efficiency of the littoral zone in the reduction of nutrient pollution. The study hypothesis was that water level reduction has a positive effect on the plant biomass of high productive species. The study was carried out in the littoral zone of Tomickie Lake, situated in the western part of Poland. This lake is located in the protected area—the buffer zone of Wielkopolska National Park, and at the international level—Natura 2000. Six transects, perpendicular to the shoreline, were selected at two subzones—permanently and seasonally flooded. Analyses of nutrient concentrations in sediments and plant species were performed. The results show the higher productivity of reeds in the zone where water occurs seasonally at the site through the year, which reached 1193 g dry weight/m2. The decline of the water level may lead to the increased growth of highly productive species as emergent vegetation with a broad ecological scale in terms of nutrient concentrations and changes of water depth, i.e., Phragmites australis (Cav.) Trin. ex Steud. Species that prefer growth in the deeper part of the lake will be characterized by lower productivity, despite the high availability of nutrients. Changes in the availability of nutrients may cause the intensification of lake overgrowth by very productive species, which may affect biodiversity, which is particularly high in protected areas.

Evaluation of Organic Wastes as Substrates for Rearing Zophobas Morio, Tenebrio Molitor, and Acheta Domesticus Larvae as Alternative Feed Supplements

Studies have focused on identifying combinations of insects and organic waste to optimise bio-conversion. Here, the effects of different diets (10% chicken feed complemented with 90% vegetable waste, garden waste, cattle manure, or horse manure) on growth and survival rates and nutritional value of Zophobas morio and Tenebrio molitor larvae, and Acheta domesticus were investigated. Compared with chicken feed, organic waste decreased the individual larval weight, although green waste showed fewer negative effects than the manure. The macronutrient concentrations in garden waste were moderate compared with chicken feed, and vegetable waste was the poorest diet in terms of nutrient concentration. There was no difference in weight between larvae reared on garden waste and those reared on vegetable waste. Tenebrio molitor and A. domesticus showed the maximum growth rates at 71–101 and 36–66 days of age at 22.5 ± 2.5 °C, respectively. Acheta domesticus was rich in proteins, whereas Z. morio and T. molitor were rich in fat. Feeding nutrient-poor diets resulted in a lower protein and a higher fat concentration in the larvae.

All-In-One: Microbial Response to Natural and Anthropogenic Forcings in a Coastal Mediterranean Ecosystem, the Syracuse Bay (Ionian Sea, Italy)

Bacterial and phytoplankton communities are known to be in close relationships, but how natural and anthropogenic stressors can affect their dynamics is not fully understood. To study the response of microbial communities to environmental and human-induced perturbations, phytoplankton and bacterial communities were seasonally monitored in a Mediterranean coastal ecosystem, Syracuse Bay, where multiple conflicts co-exist. Quali-quantitative, seasonal surveys of the phytoplankton communities (diatoms, dinoflagellates and other taxa), the potential microbial enzymatic activity rates (leucine aminopeptidase, beta-glucosidase and alkaline phosphatase) and heterotrophic culturable bacterial abundance, together with the thermohaline structure and trophic status in terms of nutrient concentrations, phytoplankton biomass (as Chlorophyll-a), and total suspended and particulate organic matter, were carried out. The aim was to integrate microbial community dynamics in the context of the environmental characterization and disentangle microbial patterns related to natural changes from those driven by the anthropic impact on this ecosystem. In spite of the complex relationships between the habitat characteristics, microbial community abundance and metabolic potential, in Syracuse Bay, the availability of organic substrates differently originated by the local conditions appeared to drive the distribution and activity of microbial assemblage. A seasonal pattern of microbial abundances was observed, with the highest concentrations of phytoplankton in spring and low values in winter, whereas heterotrophic bacteria were more abundant during the autumn period. The autumn peaks of the rates of enzymatic activities suggested that not only phytoplankton-derived but also allochthonous organic polymers strongly stimulated microbial metabolism. Increased microbial response in terms of abundance and metabolic activities was detected especially at the sites directly affected by organic matter inputs related to agriculture or aquaculture activities. Nitrogen salts such as nitrate, rather than orthophosphate, were primary drivers of phytoplankton growth. This study also provides insights on the different seasonal scenarios of water quality in Syracuse Bay, which could be helpful for management plans of this Mediterranean coastal environment.

Influence of reclaimed water on water quality of urban rivers receiving WWTP effluent in Beijing

As a new type of water source, reclaimed water is used to replenish the landscape water bodies of urban river courses, which can alleviate the problem of insufficient water in river courses. However, due to the large amount of reclaimed water input, the water quality of the downstream river is obviously different from that of the upstream river. In this study, with the recharge of reclaimed water, the water conductivity increased gradually from upstream to downstream of the Wenyu River river, while the pH decreased gradually. In terms of nutrient concentration, TN, NO3-N and NO2-N of river water showed an obvious upward trend from upstream to downstream.

Wastewater effluents cause microbial community shifts and change trophic status

Widespread wastewater pollution is one of the greatest challenges threatening the sustainable management of rivers globally. Understanding microbial responses to gradients in environmental stressors, such as wastewater pollution, is crucial to identify thresholds of community change and to develop management strategies that protect ecosystem integrity. This study used multiple lines of empirical evidence, including a novel combination of microbial ecotoxicology methods in the laboratory and field to link pressure-stressor-response relationships. Specifically, community-based whole effluent toxicity (WET) testing and environmental genomics were integrated to determine real-world community interactions, shifts and functional change in response to wastewater pollution. Here we show that wastewater effluents above moderate (>10%) concentrations caused consistent significant shifts in bacterial community structure and function. These thresholds of community shifts were also linked to changes in the trophic state of receiving waters in terms of nutrient concentrations. Differences in the community responses along the effluent concentration gradient were primarily driven by two globally relevant bacterial indicator taxa, namely Malikia spp. (Burkholderiales) and hgcI_clade (Frankiales). Species replacement occurred above moderate effluent concentrations with abundances of Malikia spp. increasing, while abundances of hgcI_clade decreased. The responses of Malikia spp. and hgcI_clade matched gene patterns associated with globally important nitrogen cycling pathways, such as denitrification and nitrogen fixation, which linked the core individual taxa to putative function and ecosystem processes, rarely achieved in previous studies. This study has identified potential indicators of change in trophic status and the functional consequences of wastewater pollution. These findings have immediate implications for both the management of environmental stressors and protection of aquatic ecosystems.

Evaluation of Organic Wastes as Substrates for Rearing Zophobas morio, Tenebrio molitor, and Acheta domesticus Larvae as Alternative Feed Supplements

Simple SummaryThe yellow mealworm, super worm, and house cricket are among the most widely produced insects, with high feed conversion efficiency. However, their nutritional composition and development rate generally vary with environmental conditions. From an economic point of view, rearing conditions such as diet, temperature, and time, and insect performance such as mortality and nutritional value are the most important factors. During their intensive growth period at room temperature, when fed a diet of vegetable waste, garden waste, cattle manure, or horse manure with 10% chicken feed, the worms performed better in terms of survival, but presented lower weight. Moreover, they showed differences in growth intensity with time. The yellow mealworm and super worm presented a relatively high fat concentration. House cricket is specifically high in protein; however, its nutritional composition is affected by the rearing substrate, and it was more sensitive to the low-value substrates. Feeding nutrient-poor diets resulted in a low protein concentration and high fat concentration in the larvae of all three species.Studies have focused on identifying combinations of insects and organic waste to optimise bio-conversion. Here, the effects of different diets (10% chicken feed complemented with 90% vegetable waste, garden waste, cattle manure, or horse manure) on growth and survival rates, and nutritional value of Zophobas morio and Tenebrio molitor larvae, and Acheta domesticus were investigated. Compared with chicken feed, organic waste decreased the individual larval weight, although green waste showed fewer negative effects than the manure. The macronutrient concentrations in garden waste were moderate compared with chicken feed, and vegetable waste was the poorest diet in terms of nutrient concentration, as revealed by the principal component analysis (PCA). There was no difference in weight between larvae reared on garden waste and those reared on vegetable waste. Tenebrio molitor and A. domesticus showed the maximum growth rates at 71–101 and 36–66 days of age at 22.5 ± 2.5 °C, respectively. The PCA showed that the protein and fibre concentrations were inversely proportional to fat concentration in the larvae. Acheta domesticus was rich in proteins, whereas Z. morio and T. molitor were rich in fat. Feeding nutrient-poor diets resulted in a lower protein and a higher fat concentration in the larvae.

Experimental harvesting of wetland plants to evaluate trade-offs between reducing methane emissions and removing nutrients accumulated to the biomass in constructed wetlands.

Constructed wetlands built for water treatment often need biomass harvesting to remove nutrients from the system. Usually harvesting is done during the peak growing season to maximize the amount of nutrients removed from the system. This, however, can create huge methane fluxes that escape from plant tissues to the atmosphere. We used manual chambers and eddy covariance measurements to analyze the increase in methane emissions due to the harvesting of two common wetland species, Typha spp. and Schoenoplectus spp., in two climatically different constructed wetlands in Estonia and California. In addition, we determined the biomass nutrient and carbon concentrations from harvested biomass. We found that harvesting during the summer season, e.g. June and August, resulted in a significant release of methane at both sites. At the California site, baseline median methane emissions were 217.6nmolm-2s-1, and harvesting resulted in increases to 395.4nmolm-2s-1 that decreased to baseline emission within three days. Footprint modeling demonstrated that the emission increases measured by eddy covariance were dominated by contributions from the cut area to the total footprint signal. At the Estonian site, harvesting resulted in methane increases of 15.9nmolm-2s-1 to 110.4nmolm-2s-1 in August. However, in September and October the emission was significantly lower. Plant biomass analyses showed clear temporal dynamics in terms of nutrient concentration, being highest in summer and lowest in winter. Our experiments indicate that the optimal time for aboveground biomass harvesting is at the end of the growing season before nutrient translocation to belowground plant structures begins coinciding with lowest methane emissions. Therefore, strategic planning of the harvest timing may help reduce greenhouse gas emissions from managed wetlands and thus improve their multi-faceted ecological benefit.

Residual effects of biochar and phosphorus on growth and nutrient accumulation by maize (Zea mays L.) amended with microbes in texturally different soils

The purpose of study was to examine the residual effects of two types of biochar amendments, two phosphorus (P) fertilizer levels, phosphorus solubilizing bacteria (PSB) and arbuscular mycorrhizal fungs (AMF) on plant growth, nutrients absorption and root architecture of Zea mays L. in texturally different soils. Biochar signficantly increased nutrients absorption and plant biomass production with P-fertilization and microbial inoculantion. Texturally different soils enhanced the plant biomass and nutrients absorption in their independent capacity on addition of biochar, microbial inoculants and P-fertilization. It was shown that mycorrhizal inoculation had positive influence on plant root and shoot biomass in both soils irrespective to the biochar type used. Root colonization was notably increased in biochar + mycorrhizae (B + M) inocultaed plants. It was shown that mycorrhizal inoculation had positive influence on nutrients absorption by plant roots and it had high content of P, potassium, calcium and magnesium in plants at all biochar and P levels. Without P fertilization, biochar amendments significantly promoted shoot P content and root colonization. The P application significantly influenced soil microbial activity in terms of nutrient concentration and plant growth. Root attributes were significantly inclined by microbial inoculation. Residual effects of biochar and P significantly enhanced the nutreints absorption and maize plant growth. Thus, we concluded that residual biochar and P fertilizer showed positive effects on nutrients absorption and maize plant growth promotion in differently textured soils. Microbial inoculants further stimulated the plant biomass production and nutrients absorption due to effective root colonization.

Estudio preliminar de ecotoxicidad y contaminación no puntual por nitrógeno y fósforo en cursos de agua superfcial cercanos a feedlots

Feedlots are plots located in establishments on which bovine cattle is fattened for market by means of the use of concentrated foods. The objective of this work was to characterize watercourses located in decline with respect to the areas where fattening pens are located in terms of nutrient concentrations and of the inputs of solids, through physicochemical analyses, and with regard to ecotoxicity through models of bioassays. To do so, samples were taken from two establishments at three different points of each watercourse: upstream, in front of, and downstream the feedlots. This study did not detect appreciable levels of acute toxicity to Daphnia magna but mild levels of toxicity in both watercourses to Vibrio fischeri and Lactuca sativa consisting on biostimulatory effects. Through physicochemical studies, it was found that in both watercourses the total phosphorus levels exceeded the established values in Decree 253/79, which were present even upstream, but further increasing downstream to the corrals.

Effects of flooding regime and meteorological variability on the removal efficiency of treatment wetlands under a Mediterranean climate

The modeling of free-water surface constructed wetlands (FWS-CWs) provides an improved understanding of their processes and constitutes a useful tool for the design and management of these systems. In this work, a dynamic simulation model for FWS-CWs was developed and used to simulate the operation of a FWS-CW proposed for improving the treatment of sewage effluents entering the Tablas de Daimiel National Park in central Spain. The process-based model simulates carbon, nitrogen and phosphorus dynamics, including key hydrological processes for wetlands under a fluctuating Mediterranean semiarid climate. The model allows for the simulation of the operation of FWS-CWs with variable flooding regimes, relating the surface water level to the flooded area and the water outflow. Simulations of the proposed FWS-CW under different water management schemes and scenarios were run, and the consequences of those management strategies on the treatment efficiency were analyzed. Under the Mediterranean climate and geology of the study area, namely, high water losses through evapotranspiration and infiltration, the decrease in nutrient concentrations was higher when the flooded area was reduced in summer than when a constant flooded area was maintained. Moreover, the meteorological variability introduced in different scenarios produced different results in terms of water outflow, but differences in terms of nutrient concentrations were not significant. The ability of the model to simulate different hydrological scenarios and their consequences on water quality makes it a useful decision-support tool.

Ecosystem of the Polish part of the Vistula Lagoon from the perspective of alternative stable states concept, with implications for management issues

Summary The alternative stable states concept finds broad application in reference to both terrestrial and aquatic ecosystems. For some reason, attempts to implement the concept to explain processes observed in estuaries and Baltic lagoons are very rare. Based on information included in publications issued over the last 60 years, three co-existing states were designated within the strongly elongated basin the Vistula Lagoon, namely: phytoplankton-dominated (Middle Basin), macrophyte-dominated (Elbląg Bay), and transition state balancing between the two former ones (West Basin). Regions of the lagoon representing such states are similar in terms of nutrient concentrations, but they considerably differ in terms of: exposure to wind and wave action, salinity, anthropogenic impact, and multi-level top-down regulations. The paper discusses the role of such drivers, responsible for both the maintenance of a given state, and the past transition into the present alternative state. Moreover, it presents chances for the improvement of the situation, as well as threats which can undermine them.

A new closed loop heating system for composting of green and food wastes

Excessive amount of foodwaste in global food supply chain is a serious issue, and additional controlling measures are needed to prevent wastages of food. In our approach to tackle this global problem, we developed an improved composting system, which can be used as a small decentralized unit for treating food and green wastes in urban environment. A new closed loop heating system was developed to enhance the temperature of compost piles, and accelerate the inactivation of pathogens during the process. The system involved a heated bath circulator, an air injector, and a system of copper piping used as heat exchangers in bins. The system was tested under aerated, static, and plowed composting conditions. To test the pathogen inactivation in the composting, the concentrations of Salmonella and Escherichia coli in compost were measured. In addition, the changes in C:N ratio, pH, and moisture content were observed to understand the quality of the compost in terms of nutrient concentrations. Results showed that the Salmonella levels reached to non-detectable limit in 34, 5, and 34 days of composting in aerated, static, and plowed composting system, respectively. The E. coli levels were detectable till day 70 indicating longer survival of E. coli cells compared to Salmonella under composting environment. In the current system, feedstock C:N ratio was reduced by 71, 70, and 62% in static, plowed, and aerated composting, respectively. We anticipate that the proposed system will yield a new composting design with less dependency on environmental conditions. The proposed design can be used for developing an in-door composting system to convert food and green wastes into pathogen free soil amendment.

Acidification of pig slurry before separation to improve slurry management on farms

ABSTRACTPig slurry, rich in plant nutrients such as nitrogen (N) and phosphorus (P), is generally applied to soil as organic fertilizer. However, costs related to slurry transport may limit its utilization to fields close to the farm, leading to significant N losses, namely ammonia (NH3) emissions. Slurry acidification, to minimize NH3 emissions, is a potential solution to this problem, while solid–liquid separation leads to a solid fraction (SF) – rich in organic matter (OM) and phosphorus – and a liquid fraction (LF) rich in soluble nutrients. We hypothesized that a combination of acidification and separation could affect the quality of the resulting fractions depending on the separation technique used. After acidification, the two most common techniques for separation, centrifugation (CF) and screw-press (SP), were applied. The main characteristics of the slurry fractions in terms of nutrient concentrations and speciation as well as the potential N mineralization (PNM) were analysed. Our results show SFs with improved properties, mostly N and PNM when acidification is performed before separation with both techniques. The PNM was significantly increased in LFs from both techniques after acidification. The concentration increased in LFs from SP with acidification; therefore, slurry acidification is recommended to avoid any N losses during the separation process with SP, while CF may not require such pretreatment. Acidification could allow the use of a cheaper technique such as SP relative to CF since it prevents NH3 emissions during the separation process and leads to more equilibrated fractions in terms of nutrient composition.

Swine manure and quicklime have different impacts on chemical properties and composition of bacterial communities of an acidic soil

Red soil is a kind of Ferralic Cambisol. Good hydrothermal resources but usually acidic and low base saturation make it very easy to be acidified under unreasonable fertilizer managements in agricultural area. In 1990, a series of fertilizer applications were established on a homogeneous field to investigate the soil fertility changes under different fertilizations in Hunan province, among them, long-term chemical nitrogen fertilization (NPK) induced severe soil acidification, whereas long-term chemical plus swine manure fertilization (NPKM) exhibited an overwhelming advantage in terms of nutrient concentration and bacterial diversity. In 2010, to investigate the effect of short-term quicklime and swine manure applications on the acid red soil, a remediation experiment was established on the NPK treatment. Quicklime (CaO) and swine manure (the same as the swine manure in NPKM) applications on NPK soil had different effects on remediating the soil acidification: short-term quicklime application (NPK+Ca) increased soil pH and bacterial diversity more rapidly, whereas short-term swine manure application (NPK+M) improved soil nutrient concentration more effectively. Alteration of environmental conditions caused significant changes of bacterial community: oligotrophic groups were in greater relative abundances with quicklime treatment, whereas copiotrophic groups were in greater relative abundances with swine manure treatment. This study provides insights into the two major remediation approaches for an acidic red soil; these insights are important for soil remediating and improving fertility. Taken together, we recommended short-term quicklime application to increase the soil pH quickly and long-term swine manure fertilization to improve soil fertility.

The nutrient accumulation pattern and cycling in natural secondary forests in North China. A case study from the Caijiachuan watershed, Shanxi Province

In order to examine the nutrient content, and the distribution and accumulation patterns of individual nutrients in the natural secondary forests (NSFs), sample NSF plots were selected in the Caijiachuan watershed on the Loess Plateau. On the basis of a comprehensive field inventory to the NSFs in Caijiachuan watershed, a 40 m × 40 m sample plot was selected as the representative plot. Each tree plant was then measured to select the standard tree in accordance with a diameter-scale. For measurement of the biomass in the above-ground part of the tree, it was divided into parts and measured. The study measured the concentration of the 5 major macronutrients (namely N, P, K, Ca and Mg) and the 8 major micronutrients (namely Cd, Fe, Mn, Cu, Zn, Pb, Ni and B) in plant organs. An appropriate amount of the samples were weighed and exposed to H2SO4-H2O2 using the Kjeldahl heating digestion method. While N content was measured with the semi-micro determination method, P content was measured using vanadium molybdate yellow colorimetric method HNO3-HClO4 ICP heating digestion method was applied to determine the contents of Ca, Mg, K, Na, Fe, Cu, Zn, Mn, B, Cd, Pb, Ni. As for soil samples, corresponding approaches were employed to work out the contents of each of the above-mentioned nutrient elements. Among the tree, shrub and herbaceous layers, the content of macro-nutrients follows the sequence of Ca > N > K > Mg > P, compared with their counterpart of K > N > Ca > P > Mg in the litter layer. For the micronutrient contents, similar sequences (i.e., Fe > Mn > Zn > B > Cu > Pb > Ni > Cd) were observed in the tree, shrub and litter layers; whereas the herbaceous layer demonstrated a different sequence of Fe > Mn > B > Zn > Cu > Pb > Ni > Cd. Within the NSF ecosystem, total accumulation of the 5 major macronutrients (excluding that in the soil) reached 1089.82 kg/ha, of which the tree layer took up the largest share, 40.82%, followed in turn by the shrub layer (31.28%), the herbaceous layer (12.55%) and the litter layer (15.36%). In terms of nutrient-concentration in the plant organs within the tree layer, the overall sequence can be expressed as branches > roots > wood > bark > leaves. The total accumulation of the 5 major macro-nutrient in the soil reached 634.97 t/ha. In terms of the accumulation coefficients in each of the layers, the general pattern can be summed up as: shrub layer > tree layer > herbaceous layer, and N > P > Ca > K > Mg. In terms of the plant organ accumulation coefficients at the tree layer, the sequence was leaves > branches > roots > bark > wood. As for the accumulation coefficients of the micronutrients, the overall sequences for the tree layer, the shrub layer and the herbaceous layer can be listed as Cd > B > Zn > Cu > Mn > Ni > Pb > Fe; Cd > B > Zn > Mn > Cu > Ni >Pb > Fe and Cd > B > Mn > Zn > Cu > Ni > Pb > Fe, respectively. The study also revealed that the macronutrients that are absorbed, assimilated and returned by the NSF stand annually reached 99.054kg/(ha·year), 49.155 kg/(ha·year) and 49.899 kg/(ha·year), respectively, demonstrating a well-balanced state of nutrient cycling. With an average of 0.0013, the absorbance index of the macro-nutrients was ranked in the following sequence, N > P > K > Ca > Mg; whereas their utilization and cycling indexes were respectively sequenced as K > P > N > Mg > Ca and K > P > N > Mg > Ca. For the micronutrients the corresponding annual figures were 117.35 g/(ha·year), 50.96 g/(ha·year) and 66.39 g/(ha·year), respectively. The micronutrients, as a whole, showed a relatively small absorbance index (e.g.,Cd was the largest =0.0036). The average utilization index of all the microelements was 0.12.

Evaluation of two milk replacers fed to hand‐reared cheetah cubs (Acinonyx jubatus): nutrient composition, apparent total tract digestibility, and comparison to maternal cheetah milk

Commercially prepared milk replacers are frequently used to provide the sole source of nutrition for hand-reared cheetah cubs (Acinonyx jubatus). The nutrient composition of two commonly used milk replacers was determined. Using titanium dioxide as an indigestible marker, nutrient digestibility was calculated from the analyses of fecal samples collected from each cub (n = 4 on formula 1, and n = 2 on formula 2). Mean apparent total tract digestibility for both formulas was >90% for all nutrients analyzed (crude protein, amino acids, crude fat (CF), and dry matter). However, the total CF content and the concentration of the essential fatty acids, such as α-linolenic, linolenic, and arachidonic acid, of both formulas was lower than reported for maternal cheetah milk. Additionally, one formula contained a comparatively high amount of carbohydrate, at the expense of protein. Although data were lacking for cheetah maternal milk, comparison with domestic cat milk revealed high concentrations of a number of minerals (K, Fe, Zn, and Cu), while vitamin D(3) was not detected in one formula. Both formulas were low in the majority of essential amino acids compared with domestic cat maternal milk. Despite their apparently high digestibility, neither formula was complete or balanced in terms of nutrient concentrations and ratios when maternal cheetah milk and/or the requirements established for growth in domestic cats were used as estimates of ideal. On this basis, although all cubs in this study were healthy and maintained good body conditions for the duration of the trial, the results of dietary analyses indicate that these milk replacers may not provide optimal nutrition for growth in cheetah cubs when used for extended periods.

A sequential extraction to determine the distribution of phosphorus in the seawater and marine surface sediment

The distribution of phosphorus species among environmental compartments (e.g., between water and sediment), significantly affects the bioavailability of these species to organisms. The eastern Mediterranean Sea is one of the most extreme oligotrophic oceanic regions on earth in terms of nutrient concentrations and primary productivity. The paper presents the results of inorganic and organic forms in surface sediment and seawater from NE Mediterranean Sea (Burclar Bay, Erdemli, South Anatolia of Turkey) in May 2007. Speciation of phosphorus in seawater and surface sediment using inductively coupled plasma-atomic emission spectrometer (ICP-AES) has been reported here. The method is based on sequential extractions of the seawater and sediment each releasing four forms of inorganic phosphorus: loosely sorbed phosphorus, phosphorus bound to aluminium (P–Al), phosphorus bound to iron (P–Fe) and phosphorus bound to calcium (P–Ca). The most abundant form of inorganic phosphorus in the seawater and surface sediment is calcium-bound phosphorus. Relative abundances of the remaining phosphorus forms in sediment follow the order: P–Al > P–Fe > loosely bound-P and in seawater follow the order P–Fe > P–Al > loosely bound-P.

Wastewater treatment with anaerobic membrane bioreactor and reverse osmosis

Domestic wastewater from a new city district in Stockholm has been treated by an anaerobic membrane bioreactor (AMBR) followed by reverse osmosis (RO). The main objectives were to study the gas production, the reduction of organic matter and nutrient recovery. The AMBR was operated at 22 degrees C (equal to the average temperature in the influent) and a hydraulic retention time of 0.6 d. The results show that the reduction of organic matter, nitrogen and phosphorus over the AMBR was approximately 92, 9 and 9%, respectively. A stable gas production was registered throughout the evaluation period. The overall removal efficiency, i.e. including the RO, was >99% for TOC, >91% for Kj-N and about 99% for P. Adding a reverse osmosis (RO) unit to the AMBR makes it possible to produce a concentrated, nutrient rich product well suited for agricultural use. The quality of the concentrate is, in terms of nutrient concentration and heavy metal content, similar to source separated human urine, i.e. nitrogen content about 3 g N/L and <2 mg Cd/kg P. However, addition of acid is required to prevent precipitation/fouling of the RO. The total electricity use for operation for the system, including the RO-unit, is estimated to be 3-6 kWh/m3.

Molecular ecology of nifH genes and transcripts in the eastern Mediterranean Sea

The eastern Mediterranean Sea is one of the most extreme oligotrophic oceanic regions on earth in terms of nutrient concentrations and primary productivity. Nitrogen fixation has been suggested to contribute to the high N : P molar ratios of approximately 28:1 found in this region. Surprisingly, no molecular biological work has been performed in situ to assess whether N(2) fixation genes actually occur in the eastern Mediterranean Sea, or to determine which organisms are responsible for this process. In this study, we examined the presence and expression of nitrogenase genes (nifH) in the upper water layer of the eastern Mediterranean. Clone libraries constructed from both DNA and reverse-transcribed PCR-amplified mRNA were examined and compared. We observed different nifH genes from diverse microbial groups, such as Cyanobacteria, Proteobacteria and methanogenic Archaea. Interestingly, numerous phylotypes were observed in coastal stations at the DNA level but none were active. However, in far offshore stations, the phylotypes observed at the DNA level were the ones that were actually active. Our preliminary study revealed diverse diazotrophs that possess and express nifH genes, which may support N(2) fixation in the eastern Mediterranean Sea.

On the issue of limiting nutrient and predictions of cyanobacteria in aquatic systems

This study aims at bridging the gap between freshwater and marine eutrophication studies by presenting (1) a cross-system analysis of the relationship between chlorophyll and the total nitrogen (TN) to total phosphorus (TP) ratio (2) a general model to predict concentrations of cyanobacteria from data on TP, the TN/TP ratio, salinity and temperature, and (3) a general trophic level classification for aquatic systems based on chlorophyll classes (for oligo-, meso-, eu- and hypertrophic systems). The data compiled in this study concerns more than 500 lakes and coastal areas covering a very wide domain in terms of nutrient concentrations and salinity. There was no simple relationship between the TN/TP ratio and empirical chlorophyll concentrations or concentrations of cyanobacteria. Variations in TP rather than TN generally seem to be more important to predict variations among systems in chlorophyll-a and cyanobacteria. Different "bioavailable" forms of the nutrients (DIN, DIP, phosphate, nitrate, etc.) have been shown to have very high coefficients of variation (CV), which means that many samples are needed to obtain reliable empirical data which are necessary in models aiming for high predictive power and practical usefulness.