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Reactive Phosphorus (reactive + phosphorus)
Kinds of Reactive Phosphorus Selected AbstractsExoenzyme activities as indicators of dissolved organic matter composition in the hyporheic zone of a floodplain riverFRESHWATER BIOLOGY, Issue 8 2010SANDRA M. CLINTON Summary 1. We measured the hyporheic microbial exoenzyme activities in a floodplain river to determine whether dissolved organic matter (DOM) bioavailability varied with overlying riparian vegetation patch structure or position along flowpaths. 2. Particulate organic matter (POM), dissolved organic carbon (DOC), dissolved oxygen (DO), electrical conductivity and temperature were sampled from wells in a riparian terrace on the Queets River, Washington, U.S.A. on 25 March, 15 May, 20 July and 09 October 1999. Dissolved nitrate, ammonium and soluble reactive phosphorus were also collected on 20 July and 09 October 1999. Wells were characterised by their associated overlying vegetation: bare cobble/young alder, mid-aged alder (8,20 years) and old alder/old-growth conifer (25 to >100 years). POM was analysed for the ash-free dry mass and the activities of eight exoenzymes (,-glucosidase, ,-glucosidase, , -N-acetylglucosaminidase, xylosidase, phosphatase, leucine aminopeptidase, esterase and endopeptidase) using fluorogenic substrates. 3. Exoenzyme activities in the Queets River hyporheic zone indicated the presence of an active microbial community metabolising a diverse array of organic molecules. Individual exoenzyme activity (mean ± standard error) ranged from 0.507 ± 0.1547 to 22.8 ± 5.69 ,mol MUF (g AFDM),1 h,1, was highly variable among wells and varied seasonally, with the lowest rates occurring in March. Exoenzyme activities were weakly correlated with DO, DOC and inorganic nutrient concentrations. 4. Ratios of leucine aminopeptidase : ,-glucosidase were low in March, May and October and high in July, potentially indicating a switch from polysaccharides to proteins as the dominant component of microbial metabolism. 5. Principal components analysis indicated that there were patch effects and that these effects were strongest in the summer. 6. DOM degradation patterns did not change systematically along hyporheic flowpaths but varied with overlying forest patch type in the Queets River hyporheic zone, suggesting that additional carbon inputs exist. We hypothesise that the most likely input is the downward movement of DOM from overlying riparian soils. Understanding this movement of DOM from soils to subsurface water is essential for understanding both the hyporheic metabolism and the carbon budget of streams and rivers. [source] Undesirable side-effects of water hyacinth control in a shallow tropical reservoirFRESHWATER BIOLOGY, Issue 6 2007DENISE DE C. BICUDO Summary 1. Based on a comprehensive data set collected monthly during 8 years (1997,2004), we evaluated the effects of mechanical removal of Eichhornia crassipes on the limnological characteristics and algal biomass of a polymictic shallow tropical reservoir. 2. Interrupted time series analyses indicated that the limnological responses to macrophyte removal can be classified as an ,abrupt permanent impact' implying that the overall mean of the time-series shifted promptly after intervention. These analyses indicated a significant increase for pH, total phosphorus, total phytoplankton and cyanobacterial biomass, and a decrease in water transparency and CO2 concentrations in the surface water; also, the increase in water stability, increase of bottom soluble reactive phosphorus (SRP) and decrease in bottom oxygen levels. 3. Cyclic anoxic periods previously observed during springs and summers were replaced by a persistent period of anoxic conditions in the sediment overlying water. Anoxic conditions were suitable for SRP release from sediments. Heavy cyanobacterial blooms became more persistent, maximum biomass (4229 mm3 L,1) was 30 times larger, the blooms frequently reached 2 m and sometimes the bottom of the reservoir, contrasting to the preremoval period in which it reached at most 1 m deep. 4. The long-term P dynamics in the system, initially driven by allochthonous nutrient loadings were replaced by internal ecological processes. Water hyacinth removal markedly accelerated the process of eutrophication due to internal feedback mechanisms, leading to a switch to a more turbid state. Biological feedback mechanisms were driven by cyanobacterial blooms by enhancing water stability, oxygen anoxia at the bottom and by increasing suitable conditions for P internal loading. These data support the hypothesis of the role of cyanobacterial blooms as an important factor impairing water quality and driving the ecosystem towards a stable degraded state. 5. These findings have important implications for the restoration of shallow stratifying eutrophic lakes, as the alternative degraded state is most likely to occur when compared with their non-stratifying counterparts. Moreover, feedback mechanisms in tropical and subtropical shallow lakes seem to be stronger than in temperate ones, as stratification events are more likely to occur over the year, intensifying system resilience to restorative strategies. [source] Does leaf quality mediate the stimulation of leaf breakdown by phosphorus in Neotropical streams?FRESHWATER BIOLOGY, Issue 4 2006MARCELO ARDÓN Summary 1. Lowland tropical streams have a chemically diverse detrital resource base, where leaf quality could potentially alter the effect of high nutrient concentrations on leaf breakdown. This has important implications given the extent and magnitude of anthropogenic nutrient loading to the environment. 2. Here, we examine if leaf quality (as determined by concentrations of cellulose, lignin and tannins) mediates the effects of high ambient phosphorus (P) concentration on leaf breakdown in streams of lowland Costa Rica. We hypothesised that P would have a stronger effect on microbial and insect processing of high- than of low-quality leaves. 3. We selected three species that represented extremes of quality as measured in leaves of eight common riparian species. Species selected were, from high- to low-quality: Trema integerrima > Castilla elastica > Zygia longifolia. We incubated single-species leaf packs in five streams that had natural differences in ambient P concentration (10,140 ,g soluble reactive phosphorus (SRP) L,1), because of variable inputs of solute-rich groundwater and also in a stream that was experimentally enriched with P (approximately 200 ,g SRP L,1). 4. The breakdown rate of all three species varied among the six streams: T. integerrima (k -values range: 0.0451,0.129 day,1); C. elastica (k -values range: 0.0064,0.021 day,1); and Z. longifolia (k -values range: 0.002,0.008 day,1). Both ambient P concentration and flow velocity had significant effects on the breakdown rate of the three species. 5. Results supported our initial hypothesis that litter quality mediates the effect of high ambient P concentration on leaf processing by microbes and insects. The response of microbial respiration, fungal biomass and invertebrate density to high ambient P concentration was greater in Trema (high quality) than in Castilla or Zygia (low quality). Variation in flow velocity, however, confounded our ability to determine the magnitude of stimulation of breakdown rate by P. 6. Cellulose and lignin appeared to be the most important factors in determining the magnitude of P-stimulation. Surprisingly, leaf secondary compounds did not have an effect. This contradicts predictions made by other researchers, regarding the key role of plant secondary compounds in affecting leaf breakdown in tropical streams. [source] Lake responses to reduced nutrient loading , an analysis of contemporary long-term data from 35 case studiesFRESHWATER BIOLOGY, Issue 10 2005ERIK JEPPESEN Summary 1. This synthesis examines 35 long-term (5,35 years, mean: 16 years) lake re-oligotrophication studies. It covers lakes ranging from shallow (mean depth <5 m and/or polymictic) to deep (mean depth up to 177 m), oligotrophic to hypertrophic (summer mean total phosphorus concentration from 7.5 to 3500 ,g L,1 before loading reduction), subtropical to temperate (latitude: 28,65°), and lowland to upland (altitude: 0,481 m). Shallow north-temperate lakes were most abundant. 2. Reduction of external total phosphorus (TP) loading resulted in lower in-lake TP concentration, lower chlorophyll a (chl a) concentration and higher Secchi depth in most lakes. Internal loading delayed the recovery, but in most lakes a new equilibrium for TP was reached after 10,15 years, which was only marginally influenced by the hydraulic retention time of the lakes. With decreasing TP concentration, the concentration of soluble reactive phosphorus (SRP) also declined substantially. 3. Decreases (if any) in total nitrogen (TN) loading were lower than for TP in most lakes. As a result, the TN : TP ratio in lake water increased in 80% of the lakes. In lakes where the TN loading was reduced, the annual mean in-lake TN concentration responded rapidly. Concentrations largely followed predictions derived from an empirical model developed earlier for Danish lakes, which includes external TN loading, hydraulic retention time and mean depth as explanatory variables. 4. Phytoplankton clearly responded to reduced nutrient loading, mainly reflecting declining TP concentrations. Declines in phytoplankton biomass were accompanied by shifts in community structure. In deep lakes, chrysophytes and dinophytes assumed greater importance at the expense of cyanobacteria. Diatoms, cryptophytes and chrysophytes became more dominant in shallow lakes, while no significant change was seen for cyanobacteria. 5. The observed declines in phytoplankton biomass and chl a may have been further augmented by enhanced zooplankton grazing, as indicated by increases in the zooplankton : phytoplankton biomass ratio and declines in the chl a : TP ratio at a summer mean TP concentration of <100,150 ,g L,1. This effect was strongest in shallow lakes. This implies potentially higher rates of zooplankton grazing and may be ascribed to the observed large changes in fish community structure and biomass with decreasing TP contribution. In 82% of the lakes for which data on fish are available, fish biomass declined with TP. The percentage of piscivores increased in 80% of those lakes and often a shift occurred towards dominance by fish species characteristic of less eutrophic waters. 6. Data on macrophytes were available only for a small subsample of lakes. In several of those lakes, abundance, coverage, plant volume inhabited or depth distribution of submerged macrophytes increased during oligotrophication, but in others no changes were observed despite greater water clarity. 7. Recovery of lakes after nutrient loading reduction may be confounded by concomitant environmental changes such as global warming. However, effects of global change are likely to run counter to reductions in nutrient loading rather than reinforcing re-oligotrophication. [source] Seasonal and interannual variation of bacterial production in lowland rivers of the Orinoco basinFRESHWATER BIOLOGY, Issue 11 2004María M. Castillo Summary 1. We examined the influence of hydrologic seasonality on temporal variation of planktonic bacterial production (BP) in relatively undisturbed lowland rivers of the middle Orinoco basin, Venezuela. We sampled two clearwater and two blackwater rivers over 2 years for dissolved organic carbon (DOC), chlorophyll, phosphorus and bacterial abundance to determine their relationship to temporal variation in BP. 2. Dissolved organic carbon concentration was greater in blackwater (543,664 ,m) than in clearwater rivers (184,240 ,m), and was generally higher during periods of rising and high water compared with low water. Chlorophyll concentration peaked (3 ,g L,1) during the first year of study when discharge was lowest, particularly in blackwater rivers. Soluble reactive phosphorus (SRP) was very low in the study rivers (<3.8 ,g L,1) and concentration increased during low water. 3. Average BP was higher in clearwater (0.20,0.26 ,g C L,1 h,1) than in blackwater rivers (0.14,0.17 ,g C L,1 h,1), although mean bacterial abundance was similar among rivers (0.6,0.8 × 106 cells mL,1). 4. Periods of higher chlorophyll a concentration (low water) or flushing of terrestrial organic material (rising water) were accompanied by higher BP, while low BP was observed during the period of high water. 5. Interannual variation in BP was influenced by variations in discharge related to El Niño Southern Oscillation events. 6. Seasonal variation in BP in the study rivers and other tropical systems was relatively small compared with seasonal variation in temperate rivers and lakes. In addition to the low seasonal variation of temperature in the tropics, low overall human disturbance could result in less variation in the inputs of nutrients and carbon to the study rivers compared with more disturbed temperate systems. [source] Oligotrophication outweighs effects of global warming in a large, deep, stratified lake ecosystemGLOBAL CHANGE BIOLOGY, Issue 2 2010H. B. STICH Abstract Between 1951 and 1979, total phosphorous concentrations in Lake Constance increased from 7 to 87 ,g L,1. Following wastewater treatment, phosphorus levels were brought under control, returning to 7.6 ,g L,1 by spring 2007. The biological and chemical data from 1980 to 2004 were first modelled by seasonal time series analyses and then used to create a general model. Excluding collinear variables allowed the data set to be condensed to six variables that could be fitted into a general linear model that explained ,75% of the observed annual variation in chlorophyll a. A clear seasonal influence was apparent, with chlorophyll a tracking trends in temperature and the progress of spring. A nonseasonal influence was also observed in the interaction of two biological components, the proportion of phytoplankton biomass available to Daphnia (i.e. the percentage of ingestible size <30 ,m) and the grazing intensity. In combination, these biotic variables had a negative impact on chlorophyll a levels. In contrast, the concentration of soluble reactive phosphorus (SRP) correlated positively with chlorophyll a. The effect of SRP showed a significant seasonal component, as it was more abundant in spring than at other times of year. In general, the model predicts a negative exponential response of chlorophyll a to further depletion of SRP in Lake Constance, while the temperature trends predicted by current global warming scenarios will result in a moderate increase in productivity. Data from 2005 to 2007 were used to verify the model. The modelled chlorophyll a values were nonbiased and showed a close match to the measured values (r2: 75%). Thus the applicability, reliability, and informative value of the model for pelagic Lake Constance was confirmed. The approach might easily be applied to other waters. [source] Large-scale climatic signatures in lakes across Europe: a meta-analysisGLOBAL CHANGE BIOLOGY, Issue 7 2007THORSTEN BLENCKNER Abstract Recent studies have highlighted the impact of the winter North Atlantic Oscillation (NAO) on water temperature, ice conditions, and spring plankton phenology in specific lakes and regions in Europe. Here, we use meta-analysis techniques to test whether 18 lakes in northern, western, and central Europe respond coherently to winter climate forcing, and to assess the persistence of the winter climate signal in physical, chemical, and biological variables during the year. A meta-analysis approach was chosen because we wished to emphasize the overall coherence pattern rather than individual lake responses. A particular strength of our approach is that time-series from each of the 18 lakes were subjected to the same robust statistical analysis covering the same 23-year period. Although the strongest overall coherence in response to the winter NAO was exhibited by lake water temperatures, a strong, coherent response was also exhibited by concentrations of soluble reactive phosphorus and soluble reactive silicate, most likely as a result of the coherent response exhibited by the spring phytoplankton bloom. Lake nitrate concentrations showed significant coherence in winter. With the exception of the cyanobacterial biomass in summer, phytoplankton biomass in all seasons was unrelated to the winter NAO. A strong coherence in the abundance of daphnids during spring can most likely be attributed to coherence in daphnid phenology. A strong coherence in the summer abundance of the cyclopoid copepods may have been related to a coherent change in their emergence from resting stages. We discuss the complex nature of the potential mechanisms that drive the observed changes. [source] The Trophic Index of Macrophytes (TIM) , a New Tool for Indicating the Trophic State of Running WatersINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2003Susanne Schneider Abstract In running waters, apart from structural degradation, nutrient input becomes increasingly important. To investigate the indicator values of as many species of submerged macrophytes as possible numerous samples of the sediment within macrophyte stands and the overlying water were taken in running waters throughout Bavaria, Germany. To develop the Trophic Index of Macrophytes (TIM), the concentrations of soluble reactive phosphorus of both the water body and the sediment pore water were used. Based on a weighted sum of the SRP-concentrations of the water body and the sediment pore water, indicator values were determined for a total of 49 species of submerged macrophytes. A detailed method is described on how and depending on which preconditions the trophic state of running waters can be determined by the TIM. An example of the TIM in the stream Rotbach is given. It shows that the TIM is a useful means to detect differences in the phosphorus loading of running waters. [source] Stream Condition in Piedmont Streams with Restored Riparian Buffers in the Chesapeake Bay Watershed,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2010Leslie L. Orzetti Orzetti, Leslie L., R. Christian Jones, and Robert F. Murphy, 2010. Stream Condition in Piedmont Streams with Restored Riparian Buffers in the Chesapeake Bay Watershed. Journal of the American Water Resources Association (JAWRA) 46(3):473-485. DOI: 10.1111/j.1752-1688.2009.00414.x Abstract:, This study tested the efficacy of restored forest riparian buffers along streams in the Chesapeake Bay watershed by examining habitat, selected water quality variables, and benthic macroinvertebrate community metrics in 30 streams with buffers ranging from zero to greater than 50 years of age. To assess water quality we measured in situ parameters (temperature, dissolved oxygen, and conductivity) and laboratory-analyzed grab samples (soluble reactive phosphorus, total phosphorus, nitrate, ammonium, and total suspended solids). Habitat conditions were scored using the Environmental Protection Agency Rapid Bioassessment Protocols for high gradient streams. Benthic macroinvertebrates were quantified using pooled riffle/run kick samples. Results showed that habitat, water quality, and benthic macroinvertebrate metrics generally improved with age of restored buffer. Habitat scores appeared to stabilize between 10 and 15 years of age and were driven mostly by epifaunal substrate availability, sinuosity, embeddedness, and velocity depth regime. Benthic invertebrate taxa richness, percent Ephemeroptera, Plecoptera, Trichoptera minus hydropsychids (%EPT minus H), % Ephemeroptera, and the Family Biotic Index were among the metrics which improved with age of buffer zone. Results are consistent with the hypothesis that forest riparian buffers enhance instream habitat, water quality, and resulting benthic macroinvertebrate communities with noticeable improvements occurring within 5-10 years postrestoration, leading to conditions approaching those of long established buffers within 10-15 years of restoration. [source] Nutrient Uptake in a Large Urban River,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2007Catherine A. Gibson Abstract:, Small streams have been shown to be efficient in retaining nutrients and regulating downstream nutrient fluxes, but less is known about nutrient retention in larger rivers. We quantified nutrient uptake length and uptake velocity in a regulated urban river to determine the river's ability to retain nutrients associated with wastewater treatment plant (WWTP) effluent. We measured net uptake of soluble reactive phosphorus (SRP), dissolved organic phosphorus, ammonium (NH4), nitrate, and dissolved organic nitrogen in the Chattahoochee River, Atlanta, GA by following the downstream decline of nutrients and fluoride from WWTP effluent on 10 dates under low flow conditions. Uptake of all nutrients was sporadic. On many dates, there was no evidence of measurable nutrient uptake lengths within the reach; indeed, on several dates release of inorganic N and P within the sample reach led to increased nutrient export downstream. When uptake occurred, SRP uptake length was negatively correlated with total suspended solids and temperature. Uptake velocities of SRP and NH4 in the Chattahoochee River were lower than velocities in less-modified systems, but they were similar to those measured in other WWTP impacted systems. Lower uptake velocities indicate a diminished capacity for nutrient uptake. [source] STORM DISCHARGE, LOADS, AND AVERAGE CONCENTRATIONS IN NORTHWEST OHIO RIVERS, 1975,1995,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2001R. Peter Richards ABSTRACT: A computerized technique was developed to identify storm runoff episodes and calculate storm discharges, storm loads, and storm average concentrations for each event in datasets with up to 10,000 records. This technique was applied to four watersheds within the Lake Erie drainage basin and identified between 160 and 250 runoff events in each. Storm event loads and storm event mean concentrations were calculated for each runoff event for suspended solids, total phosphorus, soluble reactive phosphorus, nitrate, and total Kjeldahl nitrogen. The basic characteristics of the resulting data are described, as are systematic differences as a function of watershed size, seasonal differences, and trends over time. Many of the results of this study reflect the importance of nonpoint processes and improvements in agricultural best management practices in these watersheds. [source] Effect of temperature and soluble reactive phosphorus on abundance of Aphanizomenon flos-aquae (Cyanophyceae)PHYCOLOGICAL RESEARCH, Issue 1 2000Keishi Takano SUMMARY Filament density of Aphanizomenon flos-aquae (Lemmerm.) Ralfs, water temperature and soluble reactive phosphorus (SRP) were measured from April to August in 1993,1996 in Lake Barato, Hokkaido, Japan. In addition, growth characteristics and internal phosphorus (P) utilization of Aph. flos-aquae were evaluated under P limitation at three temperatures (15, 20 and 25,C) to clarify the role of internal accumulated P for its growth in the incubation experiment. The filament density was highest in early July 1994, when SRP concentration had not yet decreased and the water temperature was high. These are important factors favoring an increase in abundance of this species in L. Barato. During batch culture, the time course of the stationary phase was shortest at 25,C and longest at 15,C; the cellular C:P molar ratio was 111 under P sufficiency and increased eight- to 12-fold under P limitation. As the C:P ratio was significantly higher in the decreasing phase at 15,C, Aph. flos-aquae may be more adaptable to Plimitation at 15,C than at 20,C and 25,C. However, the low temperatures did not favor the abundance of Aph. flos-aquae in 1996. This indicates that the filament density of Aph. flos-aquae decreases before it reaches the maximum value for some reason under P limitation in L. Barato. [source] Rehabilitation of Stream Ecosystem Functions through the Reintroduction of Coarse Particulate Organic MatterRESTORATION ECOLOGY, Issue 1 2009Kane T. Aldridge Abstract In streams, coarse particulate organic matter (CPOM) acts as a substrate for microbial activity, which promotes nutrient retention. However, in urban areas, increased peak flows within streams lead to decreased retention of CPOM. The aim of this study was to investigate whether the reintroduction of CPOM, in the form of leaf litter, into a degraded urban stream would increase biofilm activity and phosphorus retention, two ecosystem functions that reflect the integrity of the ecosystem. Stream metabolism and nutrient retention were assessed in treated (T) and control (C) channels of the Torrens River Catchment, South Australia, before and after CPOM addition. Gross primary production and community respiration (CR) were measured as oxygen production and consumption within benthic chambers. Phosphorus retention was measured through a series of short-term filterable reactive phosphorus (FRP) addition experiments. Before CPOM addition, there were no differences in CR, but C retained 6.8% more FRP than T. After CPOM addition, CR was greater in T than in C (572 and 276 mg O2·m,2·day,1, respectively), and T retained 7.7% more FRP than C. The increase in FRP retention in T compared to C was attributed to phosphorus limitation of the CPOM and increased demand for phosphorus of the attached microbial heterotrophic community. The reintroduction of CPOM into degraded streams will be an important step in the restoration of stream metabolism and nutrient retention. Maintenance of CPOM may be achieved through restoration of riparian vegetation, a reduction in the increased peak flows, and rehabilitation of stream morphology. [source] Effects of stocking density on the nutrient budget and growth of the western king prawn (Penaeus latisulcatus Kishinouye) in a recirculating aquaculture systemAQUACULTURE RESEARCH, Issue 10 2010Le Van Khoi Abstract Intensification in the commercial culture of prawns can have a significant impact on the water quality and hence on the survival, growth and the surrounding environment. The present study aims to evaluate the effects of stocking density on the water quality and performance of the western king prawns (Penaeus latisulcatus) and the nutrient budget of the culture environment. Four stocking densities of 4, 8, 16 and 32 prawns m,2 were tested in 12 recirculating systems. Prawn weight and specific growth rate increased with decreasing stocking density, while the survival rate showed the reverse trend. The mean total ammonia nitrogen, nitrate nitrogen, total phosphorus and soluble reactive phosphorus were significantly higher (P<0.05) at the higher stocking density. The nutrient budget revealed that the prawns could assimilate only 9.34,20.13% nitrogen and 4.97,11.25% phosphorus of the total nutrient inputs. The drained water at harvest was the major sink of phosphorus and nitrogen at stocking densities of 4, 8 and 16, which accounted for 45.59,64.82% and 44.28,65.62% of the total inputs, respectively, while a significant proportion of nitrogen sunk into the sediment at 32 prawns m,2. The study suggested that the stocking densities of western king prawns can be up to 16 prawns m,2 in the recirculating water environment. [source] A seasonal survey of surface water habitats within the River Spey basin, Scotland: major nutrient propertiesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2007B.O.L. Demars Abstract 1.Current monitoring strategies of governmental organizations tend to be focused on relatively large flowing and standing waters, and until recently those polluted by point sources. Consequently areas of high conservation interest tend to be understudied, and defining reference conditions, as required by current legislation, is difficult to achieve. 2.In order to address this imbalance, water samples have been collected and analysed once in each of four seasons during 2003 from 72 locations within a 100 km2 area of the oligotrophic River Spey catchment in NE Scotland. The sampling design included examples of running water (headwater streams and the main rivers) and standing water (lochs, lochans, pools, ditches, backwaters, bogs). Altitude ranged from 220 to 980 m and incorporated a climatic regime from cool temperate to sub-alpine. Each sampling campaign targeted low-flow conditions to evaluate steady-state nutrient concentrations. 3.Concentrations of the major soluble nutrients nitrogen and phosphorus demonstrated high spatial and temporal variability, with soluble organic and molybdate unreactive forms generally being dominant. Concentrations of ammonium-N, nitrate-N and soluble reactive phosphorus were extremely small, with 50% of samples falling below 8, 5 and 1 µg L,1, respectively, during spring and summer. 4.Sampling sites were grouped either by water-body type or by the properties of their immediate biophysical zone. Together these two groupings explained 33,38% of the variance in water chemistry. Certain changes were detectable across most habitats and biophysical zones. 5.A decline in the concentration of nitrate that occurred in reaches downstream from certain headwater streams draining the mountain areas indicated the potential for its within-stream utilization. Inorganic N dynamics differed between small streams and large rivers. 6.Landscape-scale patterns were recorded in spring and summer nutrient availability with inorganic N and P thresholds (arbitrarily defined) of 10 and 1 µg L,1, respectively. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||