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Many marine planktonic ciliates retain functional chloroplasts from their photosynthetic prey and use them to incorporate inorganic carbon via photosynthesis. While this strategy provides the ciliates with carbon, little is known about their ability to incorporate major dissolved inorganic nutrients, such as nitrogen and phosphorus. Here, we studied how ciliates respond to different concentrations of dissolved inorganic nitrogen and phosphorus. Specifically, we tested the direct and indirect effects of nutrient availability on the ciliate Strombidium cf. basimorphum fed the cryptophyte prey Teleaulax amphioxeia. We assessed responses in the rates of growth, ingestion, photosynthesis, inorganic nutrient uptake, and excretion. Our results show that the prey changed its carbon content depending on the nutrient concentrations. Low inorganic nutrient concentrations increased S. cf. basimorphum growth and prey ingestion. The higher carbon content of the prey under these low nutrient conditions likely supported the growth of the ciliate, while the higher carbon:nutrient stoichiometry of the prey led to the higher ingestion rates. The low carbon content of the prey at high nutrient concentrations resulted in reduced growth of S. cf. basimorphum, which indicates that carbon acquired via photosynthesis in the ciliate cannot compensate for the ingestion of prey with low carbon content. In conclusion, our findings show S. cf. basimorphum is not able to utilize dissolved inorganic nitrogen and phosphorus for growth, and this species seems to be well adapted to exploit its prey when grown at low nutrient conditions. [ABSTRACT FROM AUTHOR]

Pampean streams constitute a drainage network which discharges continental freshwater into the associated marine coastal zone. The present study concerned a set of streams within General Pueyrredón district, Southeastern province of Buenos Aires, Pampa's region, Argentina, which deserves particular attention, since they flow in the area of influence of Mar del Plata, one of the most important tourist destination in the country. Different physical–chemical (i.e., temperature, conductivity, pH, dissolved oxygen), hydrographical and eco-physiological parameters were studied within five streams along an annual cycle, searching for seasonal variations and possible relations with land use. The behavior of physical–chemical parameters was consistent with previous reports on similar environments; inorganic nutrients presented high levels along the whole period, and have never been completely depleted. Within N nutrients, nitrate demonstrated to be the dominant along the whole period, with global mean values of ~ 18 µM and reaching values up to ~ 50 µM (total discharge of N ~ 1.23 Ton DIN y−1). A very high load of organic matter (from ~ 2000 mg Cm−3 in the fall up to ~ 4000 mg Cm−3 during summer) is discharged from these streams into the marine coastal zone (which represents ~ 214 Ton POC y−1) and, even until now, response effects have not been recorded there. The obtained results allowed us to sustain that anthropic activities (i.e., agriculture, cattle raising), continental runoff and climate conditions seem to be the main drivers of the hydrographical/biogeochemical behavior of the studied streams. Therefore, changes concerning them should also be included in future monitoring programs. [ABSTRACT FROM AUTHOR]

The free-flowing Usumacinta River maintains an average annual water-level fluctuation of 6.7 m. This study evaluated relationships between 14 physicochemical and biological variables and key factors in four water-level conditions in a river–floodplain system. The analysis incorporated intra-annual variation in all variables, with each selected in accordance with multiple statistical and physicochemical criteria. Possible correlations were examined as a function of various physicochemical and biological factors at each water level. Within the study area, defined by a temporal gradient in principal component 1, the yearly river overflow above the bankfull stage is characterized by water with a low level of total suspended solids. Data on riverine wetlands suggest that seasonal changes are key to determining intra- and inter-annual chlorophyll-a levels and water clarity. However, opposite trends are observed for high and low water-level conditions. Nutrient enrichment cannot be taken as the key physicochemical factor of water level, under either water-level conditions, due to the lack of a temporal gradient in principal component 2 and the high biochemical variability of nitrate and orthophosphate levels. In conclusion, the hypothesis was accepted for the production of phytoplankton biomass and light attenuation at low and high water levels, as both were dependent on intra-annual changes. The increases in chlorophyll-a related to the minimal variability at the lowest water level open the opportunity to gauge this relationship as a possible environmental predictor for river–floodplain systems. [ABSTRACT FROM AUTHOR]

Using stable isotope analysis of nitrogen, for the first time the hypothesis on different sources of inorganic nutrients for two groups of littoral algae in Lake Baikal was confirmed. Strongly attached filamentous algae of genus Ulothrix, which developed in the wave-braking zone at depth 0.5 m, and loosely attached filamentous algae of genus Spirogyra, which developed in deeper layers 3.0–5.0 m in a low-turbulence zone, get inorganic nutrients presumably from surface discharge and groundwater inputs, respectively. Besides, stoichiometric ratios C:N and N:P in biomass of the algae indicated that growth of Spirogyra in Lake Baikal was likely limited by nitrogen, while growth of Ulothrix was limited by phosphorus. [ABSTRACT FROM AUTHOR]

While nitrogen (N) and potassium (K) fertilizers are commonly used in tomato fields for increasing plant growth and productivity, concepts regarding the interactive effects of these elements on tomato fruit quality during storage are ambiguous. The interactive effects of potassium (0, 250 and 500 mg kg soil− 1) and nitrogen (0, 150 and 300 mg kg soil− 1) fertilizers were tested on tomato fruit size at harvest, and their quality was evaluated after 30 days of storage at 4 °C. Fruit mass, firmness, taste-related parameters, inorganic nutrients, bioactive compounds, and antioxidative capacity of the fruits were investigated after the storage period. Application of 250-500 mg K in combination with 150 mg N per kg soil improved fruit mass at harvest and reduced loss of mass during storage. By increasing the soil’s K supply, the fruits exhibited significant increases in their amount of potassium, TSS and TA contents, antioxidative capacity, concentrations of lycopene, phenolics and ascorbic acid. Nonetheless, increasing the soil’s K concentration reduced Ca concentration and firmness of the fruits. By increasing the N concentration in the soil, a trend of decline was observed in the fruits’ TSS, soluble phenolics, lycopene and ascorbic acid contents. However, higher amounts of N and TA contents were detected in fruits treated with 300 mg N kg soil− 1. N treatments did not affect the antioxidative capacity of the fruits. Accordingly, application of 250 mg K + 150 mg N kg soil− 1 was suggested as the optimum treatment that could yield tomato fruits with high quality and that would also have improved storage capability. [ABSTRACT FROM AUTHOR]

The present study was conducted to test the effects of KNO3, KH2PO4, and CaCl2 on shoot multiplication, root proliferation, and accumulation of phytochemicals in in vitro cultures of Oroxylum indicum. The results indicate that modifying the MS salt formulation in relation to particular inorganic nutrients highly affected shoot multiplication, root proliferation, and accumulation of flavonoids in in vitro cultures. A concentration of 0.60 g L−1 CaCl2 resulted in the highest frequency of shoot regeneration (5.6 shoots per explant). A concentration of 0.40 g L−1 CaCl2 resulted in the highest frequency of root regeneration (7.8 roots per shoot). Modifications of the concentrations of inorganic salts were also found to be advantageous for production media for both multiple shoots and shoot-derived root in vitro cultures. Multiple shoots generated on shoot induction medium with a concentration of 0.60 g L−1 CaCl2 and roots generated on root induction medium with a concentration of 1.5 g L−1 KNO3 yielded about a five times higher flavonoid level than cultures generated on control medium respectively. [ABSTRACT FROM AUTHOR]

Dredging has been practiced to remove sediment impacted by persistent contaminants, such as heavy metals. Of these metals, lead (Pb) is of particular concern due to its toxicity. Therefore, dredged sediment containing Pb requires further mitigation. One method for Pb mitigation is phytoremediation of dredged sediment. In this study, the partitioning of Pb in sediment during phytoremediation by willow ( Salix integra) was assessed. The results showed that, in general, the bioavailable forms of Pb declined with increased application of the standard Hoagland nutrient solution, which appeared to enhance the Fe-Mn oxide fraction and residual inert fraction. In contrast, the addition of excess phosphorus decreased the bioavailable fractions of Pb. However, the bioavailable fractions of Pb increased with additional potassium addition. Planting Salix integra was shown to promote the stabilization of Pb in sediment and led to a transformation from bioavailable forms to non-bioavailable forms. The results suggest that planting Salix integra can remediate Pb-contaminated dredged sediment via Pb immobilization by the roots. During this process, the application of Hoagland nutrient solution and the application of nutrient solutions with excess phosphorus not only promote root growth of Salix integra which would reduce Pb bioavailability, but also further enhance the immobilization of Pb in contaminated sediment, likely through the formation of Pb-containing compounds with low bioavailability. [ABSTRACT FROM AUTHOR]

Water pollution caused by 2,4-dichlorophenoxyacetic acid (2,4-D) has become a serious health and environmental concern all over the world. The aim of this study was to assess the potential of Nostoc hatei strain TISTR 8405 to remove 2,4-D under different conditions. The strain TISTR 8405 was found to grow well with 2,4-D at a concentration range of 2-50 mg/L with satisfactory bioremovability. Despite its growth ability at broad-range pH intervals (4-9), the strain TISTR 8405 performed its bioremovability at decreased rates in the extreme acidic environment. Addition of heavy metals caused a strong suppressing effect on the bioremoval of 2,4-D, while amendment of nutrients enhanced bioremoval efficiency of the herbicide. GC-MS analysis indicated that the strain TISTR 8405 could degrade 2,4-D, transforming it into 2,4-DCP. The findings obtained in this study suggest that the strain TISTR 8405 could be used as a promising bioremedial agent for bioremoval of 2,4-D. However, the presence of heavy metals in aquatic environments can possibly impede its bioremoval activities. [ABSTRACT FROM AUTHOR]

Dose-response experiments were conducted to investigate the effects of ammonia nitrogen (NH/NH) and orthophosphate (PO) on four stages of larval development in Platygyra acuta, including fertilization, embryonic development and the survival, motility, and settlement of planula larvae. Fertilization success was reduced significantly under 200 μM NH/NH or PO. These high doses of NH/NH and PO affected egg viability (or sperm viability and polyspermic block simultaneously) and polyspermic block, respectively. These results provide the first evidence to indicate the mechanisms of how inorganic nutrients might affect coral fertilization processes. For embryonic development, NH/NH at 25-200 μM caused delay in cell division after 2-h exposure and NH/NH at 100-200 μM resulted in larval death after 72 h. However, no significant differences were observed in the mobility and survivorship of either planula or competent larvae under different levels of NH/NH or PO. There was a significant (~30 %) drop in the settlement of competent larvae under the combined effect of 100 μM NH/NH and PO. The effects of elevated nutrients appeared to become more significant only on gametes or larvae undergoing active cellular activities at fertilization, early development, and settlement. [ABSTRACT FROM AUTHOR]

Large freshwater contributions to the Arctic Ocean from a variety of sources combine in what is, by global standards, a remarkably small ocean basin. Indeed, the Arctic Ocean receives ∼11% of global river discharge while accounting for only ∼1% of global ocean volume. As a consequence, estuarine gradients are a defining feature not only near-shore, but throughout the Arctic Ocean. Sea-ice dynamics also play a pivotal role in the salinity regime, adding salt to the underlying water during ice formation and releasing fresh water during ice thaw. Our understanding of physical-chemical-biological interactions within this complex system is rapidly advancing. However, much of the estuarine research to date has focused on summer, open water conditions. Furthermore, our current conceptual model for Arctic estuaries is primarily based on studies of a few major river inflows. Future advancement of estuarine research in the Arctic requires concerted seasonal coverage as well as a commitment to working within a broader range of systems. With clear signals of climate change occurring in the Arctic and greater changes anticipated in the future, there is good reason to accelerate estuarine research efforts in the region. In particular, elucidating estuarine dynamics across the near-shore to ocean-wide domains is vital for understanding potential climate impacts on local ecosystems as well as broader climate feedbacks associated with storage and release of fresh water and carbon. [ABSTRACT FROM AUTHOR]

Salt-induced changes in growth, photosynthetic pigments, various gas exchange characteristics, relative membrane permeability (RMP), relative water content (RWC) and ion accumulation were examined in a greenhouse experiment on eight sunflower ( Helianthus annuus L.) cultivars. Sunflower cultivars, namely Hysun-33, Hysun-38, M-3260, S-278, Alstar-Rm, Nstt-160, Mehran-II and Brocar were subjected to non-stress (0 mM NaCl) or salt stress (150 mM NaCl) in sand culture. On the basis of percent reduction in shoot biomass, cvs. Hysun-38 and Nstt-160 were found to be salt tolerant, cvs. Hysun-33, M-3260, S-278 and Mehran-II moderately tolerant and Alstar-Rm and Brocar salt sensitive. Salt stress markedly reduced growth, different gas exchange characteristics such as photosynthetic rate ( A), water-use efficiency (WUE) calculated as A/E, transpiration rate ( E), internal CO concentration ( C) and stomatal conductance ( g) in all cultivars. The effect of 150 mM NaCl stress was non-significant on chlorophyll a and b contents, chlorophyll a/b ratio, RWC, RMP and leaf and root Cl, K and P contents; however, salt stress markedly enhanced C /C ratio, free proline content and leaf and root Na concentrations in all sunflower cultivars. Of all cultivars, cv. Hysun-38 was higher in gas exchange characteristics, RWC and proline contents as compared with the other cultivars. Overall, none of the earlier-mentioned physiological attributes except leaf K/Na ratio was found to be effective in discriminating the eight sunflower cultivars as the response of each cultivar to salt stress appraised using various physiological attributes was cultivar-specific. [ABSTRACT FROM AUTHOR]

Two surveys were performed for determining bacteria biomass (BB), temperature, salinity, chlorophyll a (chl- a) and nutrient concentrations at 11 stations with three sampling depths in the high-incidence regions of red tide in the East China Sea (ECS) in the spring of 2006. Temperature and salinity increased from nearshore to offshore region and from high latitude to low latitude in the two cruises of 2006. BB were between 0.3-5.2 mgC m (about 2.1 mgC m on average) and 0.2-6.0 mgC m (about 2.7 mgC m on average) respectively in the two cruises. BB in the surface layer decreased from the Changjiang River estuary to high sea and from low latitude to high latitude. The results showed that bacterial growth was regulated by temperature, primary production and inorganic nutrient concentrations depending on different hydrographic conditions. In the surface and middle layers where the primary production can supply enough organic substrate, temperature was the main factor to control bacteria biomass. BB showed a good correlation between the surface and middle layers in both cruises. The distribution of nutrients during both cruises showed a similar decreasing trend from nearshore region and high latitude to offshore region and low latitude. High BB values were mainly recorded from samples in the middle layer where chl- a concentrations were also high, indicating primary production being strongly correlated with temperature over the ECS shelf. In the offshore area, phosphate and silicate became limiting factors for phytoplankton growth with indirect influence on BB. Bacteria played an important role in nitrogen regeneration process turning organic nitrogen to inorganic forms such as NH. The increasing ratio of NH/DIN could be a proof of that. [ABSTRACT FROM AUTHOR]

Ice-core observations were conducted at three arctic sites in early April 2003: one clean sediment-free site (Chukchi), one sediment-rich site (Beaufort) on landfast sea ice offshore Barrow, and one oceanic Ice Exercise (ICEX) site. Concentrations of inorganic nutrients at coastal sites were similar to but higher than those at the oceanic site. Chlorophyll- a (Chl- a) concentration was much higher in the Chukchi bottom ice than at the other two sites. However, large size Chl- a (>20 μm) dominated (>70%) the bottom-ice algal Chl- a at both the Chukchi and Beaufort sites, whereas the oceanic ICEX site was evenly occupied by large (>20 μm), medium (5–20 μm), and small Chl- a (0.7–5 μm). These in situ data were incorporated into an ocean-ecosystem model. The model results revealed that: (1) strong light attenuation by trapped sediments controlled ice-algal production at the Beaufort site; (2) the peak in ice algae occurred later at the oceanic site than at the Chukchi site because of thicker ice and the consequently reduced amount of light reaching the ice algae at the ice bottom; and (3) maximum production at the oceanic site reached only 10% the level at the Chukchi site because of nutrient limitation. [ABSTRACT FROM AUTHOR]

Short and long-lived radium isotopes (223Ra, 224Ra, 226Ra, 228Ra) were used to quantify submarine groundwater discharge (SGD) and its associated input of inorganic nitrogen (NO3 −), phosphorus (PO4 3−) and silica (SiO4 4−) into the karstic Alcalfar Cove, a coastal region of Minorca Island (Western Mediterranean Sea). Cove water, seawater and groundwater (wells and karstic springs) samples were collected in May 2005 and February 2006 for radium isotopes and in November 2007 for dissolved inorganic nutrients. Salinity profiles in cove waters suggested that SGD is derived from shallow brackish springs that formed a buoyant surface fresh layer of only 0.3 m depth. A binary mixing model that considers the distribution of radium activities was used to determine the cove water composition. Results showed that cove waters contained 20% brackish groundwater; of which 6% was recirculated seawater and 14% corresponded to freshwater discharge. Using a radium-derived residence time of 2.4 days, a total SGD flux of 150,000 m3 year−1 was calculated, consisting of 45,000 m3 year−1 recirculated seawater and 105,000 m3 year−1 fresh groundwater. Fresh SGD fluxes of NO3 −, SiO4 4− and PO4 3− were estimated to be on the order of 18,000, 1,140 and 4 μmol m−2 day−1, respectively, and presumably sustain the high phytoplankton biomass observed in the cove during summer. The total amount of NO3 − and SiO4 4− supplied by SGD was higher than the measured inventories in the cove, while the reverse was true for PO4 3−. These discrepancies are likely due to non-conservative biogeochemical processes that occur within the subterranean estuary and Alcalfar Cove waters. [ABSTRACT FROM AUTHOR]

This article reports on the study of the regulatory effect of dissolved inorganic nitrogen and phosphorus on the rates of bacterial heterotrophic activity in a mesotrophic estuarine system (Ria de Aveiro, NW Portugal) along a seasonal timeframe. Ectoenzymatic activity, analysed as the rate of hydrolysis of fluorescent substrate analogues, and monomer uptake, estimated from the incorporation of radioactive glucose and leucine, were studied as descriptors of bacterial heterotrophic activity. The availability of dissolved inorganic nitrogen (DIN) was estimated as the sum of the concentrations of nitrate, nitrite and ammonium, and soluble reactive phosphorus (SRP) was determined as an estimate of inorganic phosphorus. The average ratio between DIN and SRP indicates that, generally, N was not a limiting nutrient. Maximum rates of potential aminopeptidase and β-glucosidase activities showed a global positive correlation with DIN. Under low concentrations of DIN, a tighter coupling between aminopeptidase potential activity and leucine incorporation was also observed. In conditions of N-limitation of phytoplankton growth, there was a negative relation between DIN concentration and maximum rates of leucine and glucose incorporation. The results were interpreted as an indication that aminopeptidase potential activity can partially supply organic N sources and that under distinct stoichiometric scenarios, different steps of the pathways of bacterial dissolved organic matter utilisation are affected. Under non-N-limiting situations, DIN stimulates extracellular hydrolysis, whereas under N-limiting conditions, DIN inhibits amino acid uptake. [ABSTRACT FROM AUTHOR]

We report partial pressure of CO2 (pCO2) and ancillary data in three rivers (Bia, Tanoé, and Comoé) and five lagoons (Tendo, Aby, Ebrié, Potou, and Grand-Lahou) in Ivory Coast (West Africa), during four cruises covering the main climatic seasons. The three rivers were oversaturated in CO2 with respect to atmospheric equilibrium, and the seasonal variability of pCO2 was due to dilution during the flooding period. Surface waters of the Potou, Ebrié, and Grand-Lahou lagoons were oversaturated in CO2 during all seasons. These lagoons behaved similarly to the oligohaline regions of macrotidal estuaries that are CO2 sources to the atmosphere due to net ecosystem heterotrophy and inputs of riverine CO2 rich waters. The Aby and Tendo lagoons were undersaturated in CO2 with respect to the atmosphere because of their permanent haline stratification (unlike the other lagoons) that seemed to lead to higher phytoplankton production and export of organic carbon below the pycnocline. [ABSTRACT FROM AUTHOR]

Environmental factors, including the supply of organic matter and inorganic nutrient concentrations, are thought to influence rates of two opposing processes in the nitrogen (N) cycle, denitrification and N fixation. Using sediment cores from a temperate estuary we examined the effects of nitrate, phosphate, and ammonium enrichment of the overlying water on the net N2 flux across the sediment–water interface. In addition, we used sediment cores and large marine mesocosms to determine the effect of organic matter amendment. The addition of nitrate (50 μM), ammonium (50 μM), and phosphate (10 μM) to the overlying water had no effect on the net N2 flux. However, high ammonium fluxes (145 μmol m−2 h−1) were observed in the nitrate-amended cores, which is suggestive of dissimilatory nitrate reduction to ammonium. Organic matter enrichment first increased rates of N fixation, but ultimately switched the sediments from being a net source (N fixation dominated) to a net sink (denitrification dominated) of N. We observed a threshold where N fixation took place when organic matter deposition fell below about 0.3 g C m−2 day−1. On the basis of these results and the findings of others, we developed a conceptual model that links net sediment N2 flux with the organic matter production of a system. [ABSTRACT FROM AUTHOR]

Present water quality of the perennial rivers; Göksu, Lamas, Efrenk, Tarsus and Seyhan discharging into the Cilician Basin have been investigated. Monthly surface samples collected from three stations downstream of the rivers during the period of October 2004–May 2005 were analyzed to determine ionic composition (Cl−, $${\text{SO}}_4^{2 - } $$ , $${\rm{NO}}_3^ - $$ , $${\text{PO}}^{{3 - }}_{4} $$ , $${\rm{NH}}_4^ + $$ , Ca2+, Mg2+, Na+ and K+), in addition to measurements of pH, electrical conductivity, alkalinity and total hardness. The results have been compared with recommended water quality standards. Excluding Göksu, Seyhan and Efrenk river mouths, values for almost all measured parameters, except $${\rm{NH}}_4^ + $$ , were found to be lower than the desirable limits. In particular, inorganic ammonium, phosphate and nitrate concentrations for Göksu and Seyhan Deltas were 101 or 102 orders of magnitude higher than the concentrations of the rest of the samples. Temporal variation in levels, primarily observed in $${\rm{PO}}_4^{3 - } $$ , suggest the impact of agricultural fertilizers intensively used around Göksu and Seyhan Rivers. According to Turkish National Water Pollution Control Regulations, all rivers were found to be unpolluted with respect to their nitrate, chloride, sulfate and sodium ion contents, while they all could be considered as slightly polluted with respect to their phosphate contents. In contrast to nitrate and phosphate, ammonium exceeded the maximum permissible limits of water quality criteria in almost all samples. Among the sampled rivers, Tarsus River was better in water quality, with the lowest electrical conductivity, alkalinity, total hardness and nutrient concentration values. Calculated values of elemental inorganic N and P fluxes suggest a substantial increase in nitrogen loads within the last decade, compared to a significant decrease in phosphorus loads of the rivers during the same period. [ABSTRACT FROM AUTHOR]

In plants, long-distance transport of inorganic nutrients is important for mineral nutrition, ion homeostasis, nutrient recycling, and the detoxification of toxic or excess inorganic ions. Here, we review information on the transporters involved in the loading/unloading of inorganic nutrients to and from the vascular bundle. We also describe the methods used to obtain such information. [ABSTRACT FROM AUTHOR]

Since February 1999, the Municipal Wastewater Treatment Plant (MWTP) of Balneário Camboriú, Brazil, started a complementary treatment with ClO2 application on its effluent. It was realized to minimize its impacts caused by increase of the population during summer. This study was realized in order to verify the influence of this compound in the water quality and the environmental evaluations. Samples of surface water were collected in this environment between January 1997 and June 2001 for chemical and microbiological surveys. The results had shown that after application of ClO2, fecal coliforms were decreased about six times in the beach (2.3 × 103 to 3.5 × 102 MPN/100 ml) and three times in the river (3.3 × 104 to 1.0 × 104 MPN/100 ml), during summer time. NH4 + showed an increase of about four times and 1.5 times, respectively, to beach and river. These results are showing the influence of ClO2 on chemical and microbiological parameters. [ABSTRACT FROM AUTHOR]

Daily changes in phytoplankton abundance and species composition were monitored from July to September 2003 (n=47) to understand which factors control the abundance at a station in Jangmok Bay. During the study, the phytoplankton community was mainly composed of small cell diatoms and dinoflagellates, and the dominant genera were Chaetoceros, Nitzschia, Skeletonema and Thalassionema. Phytoplankton abundance varied significantly from 6.40x104 to 1.22x107 cells/l. The initially high level of phytoplankton abundance was dominated by diatoms, but replacement by dinoflagellates started when the N/P ratio decreased to < 5.0. On the basis of the N/P and Si/N ratios, the sampling period could be divided into two: an inorganic silicate limitation period (ISLP, 14th July-12th of August) and an inorganic nitrogen limitation period (INLP, 13th of August - the end of the study). Phosphate might not limit the growth of phytoplankton assemblages in the bay during the study period. This study suggests that phytoplankton abundance and species composition might be affected by the concentrations of inorganic nutrients (N and Si), and provides baseline information for further studies on plankton dynamics in Jangmok Bay. [ABSTRACT FROM AUTHOR]

Chlorophyll a and inorganic plant nutrient levels were measured in the euphotic zone at a pelagic station in Lake Tanganyika for 12 months. In October, chlorophyll a had a mean concentration of 5.0 μg/l, the highest value obtained during the study period. A secondary peak (mean 2.5 μg/l) was obtained in May. Upwelling in July/August may have been responsible for the high biomass in October, while secondary upwelling in April/May may have caused the secondary peak in May. Secchi disc transparency ranged between 7.71 and 16.25 m. The low transparency coincided with maximum chlorophyll a in October. An inverse relationship was found between chlorophyll and transparency. High nitrate-nitrogen was observed in July and December, when the values were 67 and 76 μg N/l, respectively. Nitrogen fixation by the heterocystous Anabaena flos-aquae may have been responsible for the high nitrate values in October/December. The mean nitrate-nitrogen concentration was 45.64 μg N/l and an inverse relationship was found between chlorophyll a and nitrate-nitrogen. Very low soluble reactive phosphorus levels (range 0.4 and 4.0 μg P/l) were found throughout the 12 month period. A mean SRP concentration of 1.86 μg P/l was found. A positive correlation was found between chlorophyll a and SRP. N:P molar ratio gave a value of 54.33, showing that in the euphotic zone of the lake, P is limiting primary production. Silica concentrations were high throughout the study period with a mean value of 1.56 mg SiO2/l. [ABSTRACT FROM AUTHOR]

Bioavailability of dissolved organic carbon (DOC) can significantly influence nutrient cycling in small streams yet the factors influencing the bioavailability of DOC remains poorly understood. The isotopic composition of DOC and factors controlling its utilization were studied in two contrasting headwater streams to elucidate the relationship between DOC source and its bioavailability. Water samples were collected monthly from Moore Creek (MC), located in a watershed dominated by fertilized pasture, and from Huey Hollow (HH), located in a deciduous forest watershed. Dissolved organic carbon concentrations ranged from 222 to 1130 μm C and 35 to 289 μm C in MC and HH, respectively. The isotopic composition of DOC (δ13CDOC) was more seasonally variable in HH and ranged from -33.6 to -28.0\fontencodingTS1\selectfontĞ, as compared with MC where it ranged from -27.2 to -24.5\fontencodingTS1\selectfontĞ. The δ13CDOC in Huey Hollow suggests leaf debris was an important source of DOC throughout most of the year while algae was important in winter and early spring. In MC, the δ13CDOC indicated DOC was largely derived from soil organic matter while algal inputs were small relative to the large pool of refractory DOC. Stream water community respiration (SWCR) rates suggest the existence of a larger pool of refractory DOC in MC relative to HH. The ratio of SWCR (μM C h-1) to DOC concentration (mM C) was generally higher in HH (1.2–13.2) as compared with MC (0.2–4.2), suggesting that relative bioavailability of DOC was often greater in HH. Nutrient addition experiments indicate that bioavailable C limited SWCR in spring and fall in MC, while bioavailable C was never limiting in HH. The results suggest that elevated nutrient and DOC concentrations supported higher levels of microbial activity that resulted in a large pool of refractory DOC in MC. The lower inorganic nutrient and DOC concentrations reduced microbial activity in HH and likely limited the production of refractory DOC. Results of this study suggest that both organic matter source and nutrient concentration are important determinants of DOC bioavailability in small streams. % [ABSTRACT FROM AUTHOR]

The present investigation provides data of some ions, namely Na+, Ca2+, NH4+, Cl-, NO3-, CN- and PO43- on water samples of river Osun, selected rivers in the region and groundwaters. The pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and total carbon (IV) oxide (TCO2) have also been determined to asses the chemical status and pollution levels of these water sources. The higher values of certain parameters with respect to the acceptable standard limits for drinking water indicate the pollution in both groundwater and river water samples of the study area, and make the waters unsuitable for various applications. The high pollution river water source showed higher levels of phosphate, nitrate and ammonium ions (P < 0.05). There is no significant difference (P < 0.05) between the mean concentrations of other inorganic nutrients in the high and low pollution water source types. The correlation coefficient between quality parameter pairs of river water and groundwater samples are determined and the significance of these parameters in both types of water sources are discussed. [ABSTRACT FROM AUTHOR]

A probe that allows to take water samples in intertidal areas at high spatial resolution in the first metre above the bottom without disturbing the current profile has been developed. Data on dissolved inorganic nutrients were obtained at a temporal resolution of 30 minutes and spatial distances of 2, 4, 8, 16, 32. 64 and 100 cm above the bottom from up to three hours before to up to four hours after high tide. The layer in direct contact with the sediment showed marked concentration changes with tidal state. All compounds analysed exhibited a pronounced minimum at or immediately after current direction change. Depth profiles, on the other hand, did not give such a consistent picture. Individual compounds showed fluxes into and out of the sediment independently of each other and of tidal state. The data obtained suggest that sediment-water interactions play a major role in controlling nutrient concentrations in intertidal waters on short time scales. [ABSTRACT FROM AUTHOR]

The effects of P, N and Ca+Mg fertilization on biomass production, leaf area, root length, vesiculararbuscular mycorrhizal (VAM) colonization, and shoot and root nutrient concentrations of pretransplant rice ( Oryza sativa L.) plants were investigated. Mycorrhizal plants generally had a higher biomass and P, N, K, Ca, Mn, Fe, Cu, Na, B, Zn, Al, Mg, and S shoot-tissue nutrient concentrations than non-mycorrhizal plants. Although mycorrhizal plants always had higher root-tissue nutrient concentrations than non-mycorrhizal plants, they were not significantly different, except for Mn. N fertilization stimulated colonization of the root system (colonized root length), and increased biomass production and nutrient concentrations of mycorrhizal plants. Biomass increases due to N were larger when the plants were not fertilized with additional P. P fertilization reduced the colonized root length and biomass production of mycorrhizal plants. The base treatment (Ca+Mg) did not significantly affect biomass production but increased the colonized root length. These results stress the importance of evaluating the VAM rice symbiosis under various fertilization regimes. The results of this study suggest that pretransplant mycorrhizal rice plants may have a potential for better field establishment than non-mycorrhizal plants. [ABSTRACT FROM AUTHOR]

A difference in biomass production between plants grown in autoclaved soil and non-autoclaved soil under N and base (Ca + Mg) treatments was probably caused by soil microbes other than vesicular-arbuscular mycorrhizal fungi. The plants were grown for 70 days in autoclaved soil, autoclaved soil with a vesicular-arbuscular mycorrhizal-free filtrate of non-autoclaved soil added, and non-autoclaved soil. The plants in each substrate received additional N, P, or Ca + Mg (base treatment) weekly. Control plants received no additional nutrients. The plant response to various substrates was a function of nutrient treatment. Colonization of roots by vesicular-arbuscular mycorrhizal fungi in non-autoclaved soil was lowest with the N and P treatments. There were significant negative correlations between vesicular-arbuscular mycorrhizal colonization and all plant growth variates. For all nutrient treatments, there were no differences in total biomass between plants grown in non-autoclaved soil and in the autoclaved-plus-filtrate substrate. [ABSTRACT FROM AUTHOR]

The leaves of terrestrial plants are capable of absorbing nutrients supplied in an aqueous medium. This capacity is exploited in many agronomic practices like application of herbicides, growth regulators and inorganic nutrients, for the purpose of enhancing crop production. The mechanisms of foliar absorption and subsequent transport of inorganic nutrients are discussed here. The penetration of the nutrient elements supplied to the leaf, through the outermost barrier-the cuticle-absorption by the leaf cells within, and transport from cell-to-cell finally to the conducting system of the leaf, are as complex as those following the root absorption. Yet, foliar supply of nutrients have many advantages over the root-feeding. There have been considerable interest in the practical use of this technique, as also several accomplishments not only in the understanding of the mechanisms involved in foliar uptake, but also in the development of chemicals and surfactants for the greater effectiveness. [ABSTRACT FROM AUTHOR]

Geochemistry involves the study of the distribution, proportion, and association of chemical elements of the earth’s crust that are present in different matrices such as water (sweet, saline, residual, rain, underground), soils, minerals, sediments, rocks, and air. Initially, this discipline was only used to study the composition and formation of rocks, but nowadays simultaneously relates geology to chemistry. [ABSTRACT FROM AUTHOR]