High Levels Of Total Phosphorus Research Articles

Impact of fertilization and grazing on soil N and enzyme activities in a karst pasture ecosystem

The biggest obstacle to economic development in karst areas comes from the ecological crisis, so healthy soil and adequate food are important. Soil nitrogen (N) is an important factor in maintaining soil quality. Understanding the changes in soil N fractions and enzyme activities under different management practices is important to maintain sustainable pastureland in karst areas. In this study, we investigated how grazing and fertilization affect different soil nitrogen fractions and enzyme activities of karst pastureland. The four treatments were unused land (UL, undisturbed utilization), abandoned-grazing pastureland (APL, grazing for three years followed by abandonment for six years), grazing pastureland (GPL, controlled grazing without fertilizer) and fertilized-grazing pastureland (FGPL, controlled grazing + fertilizer), with the aim of determining the management practices that is most beneficial to soil N in the area. Our results indicated that FGPL is the most beneficial in enhancing soil N fractions. This is reflected in greater total nitrogen (TN), alkaline driven nitrogen (NOH), inorganic nitrogen (TON), anaerobic mineralized nitrogen (The average increase in each soil layer over UL was 1.43 times; TMN), microbial biomass nitrogen (The average increase in each soil layer over UL was 3.51 times; MBN), amino acid nitrogen (AAN), amino sugar nitrogen (ASN), acidolyzed unknown nitrogen (TUN) and unacidified nitrogen (AIN) in FGPL soils. Likewise, greater enzyme activities were also found in nitrogen conversion-related enzymes (soil urease (S-UE), soil N-acetyl-β-D-aminoglucosidase (S-NAG), nitrate reductase (S-NR), and soil acid protease (S-ACPT)). In addition, the combination of grazing and balanced nutrient inputs slowed soil acidification and maintained high levels of total phosphorus (TP) and total potassium (TK). In contrast, the soil N fractions responded significantly to APL (low TN and plant effective nitrogen), while insufficient conversion capacity (enzyme activity, MBN) was the main reason for the compromised soil N availability at GPL. Government policy makers and livestock producers should encourage controlled grazing with proper fertilizer supplementation, and avoid prolonged abandonment of grazing lands.

Distribution, driving forces, and risk assessment of 2-MIB and its producer in a drinking water source-oriented shallow lake.

Freshwater blooms of harmful cyanobacteria in drinking water source-oriented shallow lakes affect public health and ecosystem services worldwide. Therefore, identifying 2-methylisoborneol (2-MIB)-producing cyanobacteria and predicting the risks of 2-MIB are critical for managing 2-MIB-infected water sources. Previous studies on the potential producers and risks of 2-MIB have focused on reservoirs or have been limited by the ecosystems of phytoplankton-dominated areas. We investigated the producers, distribution, and occurrence of 2-MIB in East Taihu Lake-a drinking water source-oriented shallow lake with macrophyte- and phytoplankton-dominated areas-from August 2020 to November 2021. We observed that Pseudanabaena sp. produces 2-MIB in this lake, as determined by the maximum correlation coefficient (R = 0.71, p < 0.001), maximum detection rate, and minimum false positive/negative ratio exhibited by this genus. Extreme odor events occurred in this lake during late summer and early autumn in 2021, with the mean 2-MIB concentration increasing to 727 ± 426ng/L and 369 ± 176ng/L in August and September, respectively. Moreover, the macrophyte-dominated area, particularly the wetland area, exhibited a significant decrease (p < 0.01) in bloom intensity and 2-MIB production during these extreme odor events. Pseudanabaena sp. outbreak was likely owing to eutrophication, seasonal gradients, and macrophyte reduction, considering that temporal trends were consistent with high water temperature, high total phosphorus levels, and low-light conditions. Moreover, 2-MIB production was sensitive to short-term hydrometeorological processes, with high water levels and radiant intensity enhancing 2-MIB production. The risk assessment results showed that the probability of 2-MIB concentration exceeding the odor threshold (10ng/L) is up to 90% when the cell density of Pseudanabaena sp. reaches 1.8 × 107 cell/L; this risk is reduced to 50 and 25% at densities of < 3.8 × 105 cell/L and 5.6 × 104 cell/L, respectively. Our findings support calls for shallow lake management efforts to maintain a macrophyte-dominated state and control odorous cyanobacteria growth.

Drone-based water sampling and characterization of three freshwater harmful algal blooms in the United States

Freshwater harmful algal blooms (HABs), caused mostly by toxic cyanobacteria, produce a range of cyanotoxins that threaten the health of humans and domestic animals. Climate conditions and anthropogenic influences such as agricultural run-off can alter the onset and intensity of HABs. Little is known about the distribution and spread of freshwater HABs. Current sampling protocols in some lakes involve teams of researchers that collect samples by hand from a boat and/or from the shoreline. Water samples can be collected from the surface, from discrete-depth collections, and/or from depth-integrated intervals. These collections are often restricted to certain months of the year, and generally are only performed at a limited number of collection sites. In lakes with active HABs, surface samples are generally sufficient for HAB water quality assessments. We used a unique DrOne Water Sampling SystEm (DOWSE) to collect water samples from the surface of three different HABs in Ohio (Grand Lake St Marys, GLSM and Lake Erie) and Virginia (Lake Anna), United States in 2019. The DOWSE consisted of a 3D-printed sampling device tethered to a drone (uncrewed aerial system, or UAS), and was used to collect surface water samples at different distances (10–100 m) from the shore or from an anchored boat. One hundred and eighty water samples (40 at GLSM, 20 at Lake Erie, and 120 at Lake Anna) were collected and analyzed from 18 drone flights. Our methods included testing for cyanotoxins, phycocyanin, and nutrients from surface water samples. Mean concentrations of microcystins (MCs) in drone water samples were 15.00, 1.92, and 0.02 ppb for GLSM, Lake Erie, and Lake Anna, respectively. Lake Anna had low levels of anatoxin in nearly all (111/120) of the drone water samples. Mean concentrations of phycocyanin in drone water samples were 687, 38, and 62 ppb for GLSM, Lake Erie, and Lake Anna, respectively. High levels of total phosphorus were observed in the drone water samples from GLSM (mean of 0.34 mg/L) and Lake Erie (mean of 0.12 mg/L). Lake Anna had the highest variability of total phosphorus with concentrations that ranged from 0.01 mg/L to 0.21 mg/L, with a mean of 0.06 mg/L. Nitrate levels varied greatly across sites, inverse with bloom biomass, ranging from below detection to 3.64 mg/L, with highest mean values in Lake Erie followed by GLSM and Lake Anna, respectively. Drones offer a rapid, targeted collection of water samples from virtually anywhere on a lake with an active HAB without the need for a boat which can disturb the surrounding water. Drones are, however, limited in their ability to operate during inclement weather such as rain and heavy winds. Collectively, our results highlight numerous opportunities for drone-based water sampling technologies to track, predict, and respond to HABs in the future.

Beneficial Bacterium Azospirillum brasilense Induces Morphological, Physiological and Molecular Adaptation to Phosphorus Deficiency in Arabidopsis.

Although most cultivated soils have high levels of total phosphorus (P), the levels of bioavailable inorganic P (Pi) are insufficient. The application of plant-growth-promoting rhizobacteria (PGPR) is an eco-friendly strategy for P utilization; however, PGPR-mediated plant responses that enhance Pi acquisition remain unexplored. Here, we investigated the effect of Azospirillum brasilense on Arabidopsis adaptation to Pi deficiency. Results showed that A. brasilense inoculation alleviated Pi-deficiency-induced growth inhibition and anthocyanin accumulation and increased the total P content in Arabidopsis plants. A comprehensive analysis of root morphology revealed that A. brasilense increased root hair density and length under Pi-limited conditions. We further demonstrated that A. brasilense enhanced the acid phosphatase activity and upregulated the expression of several Pi transporter genes, such as PHOSPHATE1 (PHO1), PHOSPHATE TRANSPORTER 1:(PHT1:1) and PHT1;4. However, A. brasilense did not enhance the growth o total P content in pht1;1, pht1;4 and pht1;1pht1;4 mutants. Moreover, A. brasilense could not increase the P content and PHT1;1 expression in the root hairless mutant rsl4rsl2, because of the occurrence of low-Pi-induced PHT1;1 and PHT1;4 in root hairs. These results indicate that A. brasilense can promote root hair development and enhance acid phosphatase activity and Pi transporter expression levels, consequently improving the Pi absorption capacity and conferring plant tolerance to Pi deficiency.

Can shrimp farming wastewater negatively affect water quality and zooplankton community structure of a Neotropical estuary? A case study during a productive cycle of Litopenaeus vannamei

Aquaculture wastewater can influence various communities’ structures in both marine and freshwater environments. This study describes the zooplankton community structure and environmental variables in both Passos River estuary (Northeast Atlantic, Brazil) and commercial shrimp farming ponds associated with this estuary. Samples for water quality analysis and quantification and identification of zooplankton were taken during a shrimp culture cycle (July to September 2014) from eight sites (two across the main channel, downstream and upstream, and six shrimp farming ponds). The main water quality parameters showed difference between the shrimp farming ponds and the Passos River estuary – higher levels of total phosphorus and chlorophyll-a were observed in the shrimp ponds. The zooplankton structure at different environments was dominated by the copepods (53.3 to 83.7%) and rotifers (9.2 to 35.5%) but no significant difference was observed among the individual densities. Meanwhile, nutrients availability was a key for high plankton densities in shrimp ponds. These findings have suggested that wastewater from shrimp farming did not influence the zooplankton community on a Neotropical estuary on a short-time scale.

In Situ Monitoring of a Eutrophicated Pond Revealed Complex Dynamics of Nitrogen and Phosphorus Triggered by Decomposition of Floating-Leaved Macrophytes

To explore the influence of the decomposition of aquatic macrophytes on water quality in eutrophicated aquatic ecosystems and the interacting environmental factors that trigger nitrogen (N) and phosphorus (P) dynamics, a suburban pond with floating-leaved macrophytes (Pond A) as well as another nearby newly dug pond without any obvious aquatic macrophytes (Pond B) were studied. N and P levels together with a series of parameters relating to biomass, water and sediments were monitored during a period of 84 d that covered the entire decomposition process of plants. The results show that the decomposition of aquatic macrophytes can be divided into two phases, with the first phase having a faster decomposition rate and the second phase, a slower one. With the decomposition of biomass, the dissolved oxygen (DO), oxidation-reduction potential (ORP), and pondus hydrogenii (pH) of the water body increased, whereas the permanganate index (CODMn) decreased. Significantly higher levels of total phosphorus in both water and sediment (TPW and TPS) were detected in Pond A with macrophytes; TPW increased quickly during the first phase of biomass decomposition but decreased in the second phase, and TPS remained relatively stable during the first phase but increased slowly in the second phase. Total nitrogen in both water and sediment (TNW and TNS) was also significantly higher in Pond A but remained relatively stable. A structural equation model revealed that the decomposition of aquatic macrophytes, could, directly and indirectly, influence N and P cycles in an aquatic ecosystem through the regulation of pH and DO. Our study indicate that the decomposition of biomass exerted a greater influence on P than on N. Besides the direct release of P from decaying biomass, which caused a significant increase of P in water body, changes of DO and ORP and the subsequent redox state of the whole system during the process also indirectly affected the deposition and dissolution of P between sediment and water. P was the decisive factor that caused endogenous eutrophication in ponds containing aquatic macrophytes.

Environmental analysis of soil characteristics in El-Fayoum Governorate using geomatics approach.

The present study aims at identifying the impact of wastewater irrigation on soil characteristics of El-Fayoum Governorate using Landsat images and geo-statistical techniques integrated with field investigation and soil analyses. Soil samples were collected from 40 representative sites during November/December 2016 and analyzed for pH, electric conductivity (EC), organic carbon (OC), total nitrogen (TN), total phosphorus (TP), Ca, K, Na, and Mg. Landsat images were processed to produce spectral indices of water (MNDWI), vegetation (NDVI), salinity (NDSI), and urban areas (NDBI). Inverse distance weighting in ArcGIS 10.1 was used for mapping soil characteristics. Results refereed to a fluctuation in soil characteristics among different districts, as a result of variation and severity of activities. High levels of OC (3.5-5.21%) were recorded in several scattered parts while northern parts showed high levels of TP and TN recording 0.8-1.7mg/g and 1.7-2.4mg/g respectively. A great fluctuation in salinity, Ca, K, and Na levels were detected among the collected soil samples. Southern and eastern borders of the governorate showed high levels of Ca (> 17.7mg/g). The most alkaline soil samples (> 8) were mostly recorded in El-Fayoum and Tamia districts. Variation of soil characteristics is greatly impacted by irrigation using wastewater particularly from El-Bats and El-Wadi drains. A strong positive correlation (0.94) was observed between urbanization (NDBI) and land salinization (NDSI) which ensures the negative impact of residential areas on agricultural lands. It can be concluded that the agricultural land problems have greatly been impacted by the lack of sufficient water supply. Geospatial techniques along with soil analyses facilitate studying such problems.

Spatial and temporal variation of phytoplankton functional groups in extremely alkaline Dali Nur Lake, North China

In this study, the concept of phytoplankton functional groups was used to assess phytoplankton community structure in an attempt to better understand their spatial and seasonal variation in extremely alkaline Dali Nur Lake. Samples were collected for analysis during spring, summer and autumn for a period of two years. We identified 13 phytoplankton functional groups (Lo, S1, H1, P, C, MP, X3, Y, X2, W1, J, F, and T) among 37 species out of which 7 groups Lo, H1, P, C, MP, X2, and F were dominant. The biomass of phytoplankton functional groups in the Lake exhibited a strong seasonal variation with the highest biomass value observed in autumn and lowest in spring. Functional groups MP, P, and C were dominant in spring when the temperatures were very low. Groups H1 and X2 were the dominant in summer corresponding to higher temperatures. In autumn groups Lo and X2 were the dominant corresponding to high levels of total phosphorus (TP). Our study revealed that alkalinity, pH, arsenic, chemical oxygen demand, and TP are the most important physical–chemical variables structuring the phytoplankton functional groups in Dali Nur Lake. Functional groups Lo and X2 were mainly influenced by TP while groups MP and P flourished better under high conditions of arsenic. This study reveals the importance of physical–chemical variables in the spatial and seasonal gradient, in structuring phytoplankton functional groups, and consequently in the assessment of environmental status of the lake.

Water quality of a coastal lagoon (ES, Brazil): abiotic aspects, cytogenetic damage, and phytoplankton dynamics.

Assessment of water resources requires interdisciplinary studies that include multiple ecosystem aspects. This study evaluated the water quality of Juara Lagoon (ES, Brazil) based on physical and chemical variables, cytogenetic responses in Allium cepa and phytoplankton dynamics. Three sampling sites were defined and water samples were collected during two sampling periods. Analyses such as determination of photic zone, conductivity, and concentrations of nutrients and metals were conducted as well as cytotoxic, mutagenic, and genotoxic potentials using A. cepa test. The main attributes of phytoplankton community, such as total richness, total density, density by class, dominance, and diversity, were also evaluated. Results have revealed that Juara Lagoon has signs of artificial eutrophication at two sampling sites due to high levels of total phosphorus and ammonia nitrogen. Cytotoxic, genotoxic, and mutagenic potentials were detected as well as high concentrations of Fe and Mn. Furthermore, 165 phytoplankton taxa were recorded, with highest richness in Chlorophyceae and Cyanophyceae classes. In addition, Cyanophyceae presented as the highest density class. A. cepa test and phytoplankton community evaluation indicated that the ecological quality of Juara Lagoon is compromised.

Assessment of water pollution induced by human activities in Burullus Lake using Landsat 8 operational land imager and GIS

Burullus Lake is the second largest lake along the Mediterranean Sea and represents one of the most subjected lakes to pollution at the delta’s coastline. The present study explores the use of Landsat data and GIS for assessing water pollution at Burullus Lake, Egypt. Multi-spectral Landsat-8 OLI image dated 2015 provided the necessary information to this study. Radiometric and atmospheric corrections were applied to the image. Land use/cover map was obtained to identify natural resources and types of human activities in the area surrounding the Lake. Three previously developed water quality empirical models for BOD, total nitrogen (TN) and total phosphorus (TP) were applied on the calibrated image. Then, a GIS model was generated to identify areas recording high levels of BOD, TN and TP. Results confirmed that the Lake water is subjected to pollution from multiple sources; particularly domestic and agricultural drains. Shallow water (i.e. Lake Shores), where human activities are influencing, reported high levels of water studied pollutants. The model indicated that south western and north eastern parts of the Lake are the most polluted parts, recording relatively high levels of BOD, TN and TP; >4.46mgL−1, >18.33mgL−1 and >15.59mgL−1, respectively. Results were ascertained based on water quality investigations in relevant research studies on the Lake. It was concluded that Burullus Lake is extensively subjected to interrupting human activities which have a great negative impact on water quality. Also data-observation techniques and water quality empirical models were successful in assessing and mapping water pollution.

Diatom Assemblages in Surface Sediments Along Nutrient and Salinity Gradients of Thi Vai Estuary and Can Gio Mangrove Forest, Southern Vietnam

In order to assess the current ecological status of the tidal Thi Vai Estuary and the Can Gio Mangrove Forest in Southern Vietnam, we evaluated the spatial diatom composition and abundance in surface sediments and their relation to physical and chemical parameters of the water. Major changes in the distribution of diatom assemblages were determined by multivariate statistical analyses. Principal component analysis (PCA) was used to ordinate environmental variables of the water, showing a clear gradient along the estuary, with higher nutrient levels (total phosphorus and total nitrogen) and lower dissolved oxygen (DO) concentrations at upstream sites. Canonical correspondence analysis (CCA) was used to determine the species-environmental relationship. Total phosphorus (TP) and DO (p < 0.001) as well as salinity and pH (p < 0.002) were the most significant variables related to diatom composition. The neritic planktonic species Thalassionema nitzschioides (Grunow) Mereschkowsky was the most widespread and abundant species in the data set, presumably also reflecting significant influence of oceanic water. Thalassiosira cedarkeyensis Prasad, a marine benthic species, was the second most abundant species and seems to be related to higher nutrient levels, particularly at upstream sites. High abundances of Cyclotella meneghiniana Kutzing and Cyclotella atomus Hustedt were also recorded upstream sites. Their association to high TP levels and lower DO concentrations suggests deterioration of water quality. This study shows the potential of diatoms as indicators of environmental change even in dynamic systems such as estuaries.

Trace metal bioavailability in sediments from a reference site, Ribeira Bay, Brazil

Surface sediments were collected near potential contamination sources impacting Ribeira Bay (Brazil), a system considered as a ‘reference site’ for trace metals. Physicochemical properties (pH and Eh), grain size and concentrations of total organic carbon (TOC), total phosphorus (TP), acid-volatile sulfides (AVS) and simultaneously-extracted metals (Fe, Mn, Cd, Cu, Ni, Pb and Zn) were analyzed. Although relatively low metal concentrations were found, correlations of Zn and Ni with high TP levels suggested an association with sewage inputs, while other metals presented associations with specific geochemical carriers (TOC, Fe and Mn compounds). AVS levels exceeding those of the sums of Cd, Cu, Ni, Pb and Zn (ΣSEM) by at least one order of magnitude and TOC-normalized differences between ΣSEM and AVS ((ΣSEM–AVS)/fOC) near to or below than −200μmolgOC−1 indicated that there were sufficient AVS and TOC levels to control trace metal bioavailability in sediment pore water.

Assessment of Nutrient and Sediment Loads in Buhisan, Bulacao and Lahug Rivers, Cebu, Philippines

The study aimed to provide baseline data by assessing the nutrient levels and sediment load in Buhisan, Bulacao and Lahug Rivers. Specifically, the study assessed the nitrates, Total Phosphorus (TP), Total Suspended Solids (TSS) and Total Dissolved Solids (TDS) concentrations of the rivers. Water samples were taken by grab sampling from three designated sites (upstream, midstream and downstream) along each river. Laboratory analyses were performed according to standard protocols. Results of the study were compared with the standard set by the Department of Environmental and Natural Resources (DENR). The nitrate, TSS and TDS levels did not exceed the allowable concentration set by the government but the TP did. The mean TP values observed at Buhisan, Bulacao and Lahug Rivers ranged from 0.10-1.82 mg∙L-, 0.05-0.48 mg∙L-, and 0.17-2.75 mg∙L-, respectively. The TP levels in the midstream and downstream areas of Buhisan and Lahug Rivers exceeded the 0.4 mg∙L- limit. High TP levels could be attributed to anthropogenic sources like untreated domestic waste discharges, unsanitary sewer systems in the surrounding communities, and runoffs from fertilized backyard gardening, and piggery.

The effects of Asian summer monsoons on algal blooms in reservoirs

An important characteristic of lakes and reservoirs in the East Asian summer monsoon region is the dramatic seasonal difference in hydrologic inputs, with annual rainfall commonly concentrated in a few heavy rain events. In this study, we surveyed the monthly variations of phytoplankton density in 3 large deep reservoirs and 7 small shallow reservoirs and analyzed the effect of large precipitation events on phytoplankton. During heavy rains, stream phosphorus concentrations increased sharply, and phosphorus loadings into reservoirs were not continuous but episodic shock loadings. In deep stratified reservoirs, however, the concentrations of phosphorus and chlorophyll a were much lower than expected from the high total phosphorus levels in the storm runoff. Inflowing storm waters laden with phosphorus flowed into metalimnetic layers because deep reservoirs had strong thermal stratification and the storm water was cooler than the epilimnion. The result was the formation of an ecosystem resilient to phosphorus shock loadings during monsoon. Nutrients in the metalimnion seemed to be dispersed gradually toward the epilimnion, and phytoplankton reached maximum densities, called “monsoon blooms,” after the monsoon. By contrast, shallow reservoirs with short hydraulic residence times had lower chlorophyll a concentrations during the monsoon season because the high flushing rate was the major limiting factor of phytoplankton growth. In conclusion, summer monsoon is the major determinant of phytoplankton density in reservoirs of the East Asian region, but their responses can vary widely depending on hydrologic characteristics.

Sediment phosphorus forms and levels in two tropical floodplain wetlands

Inorganic phosphorus is one of the critical nutrients determining trophic state and freshwater productivity. Sediment may act as a sink or source of phosphorus to the overlying water depending on its pH, redox state, various forms of phosphorus present, etc. To examine potential sorption or mobilization of sediment phosphorus in floodplain wetlands, the amount and distribution of phosphorus fractions were evaluated using a sequential chemical extraction procedure. Exceedingly high levels of total phosphorus (mean: 6040 ± 344, 5470 ± 363 mg kg−1), consisting largely of organic and refractory fraction (70 – 98%), followed by calcium-phosphorus (mean: 584 ± 31.3, 143 ± 8.42 mg kg−1) and iron-phosphorus (mean: 108 ± 10.1, 91.0 ± 7.68 mg kg−1) were recorded respectively in Bhomra and Akaipur wetlands of West Bengal, India. The inorganic phosphorus, comprising the loosely sorbed phosphorus and all the mineral bound forms contributed only about 6–14% to the total phosphorus indicating their less significance in phosphorus sorption or desorption in these tropical wetlands. Although the loosely sorbed phosphorus was in moderate level (2.69 ± 0.69, 1.54 ± 0.53 mg kg−1), water dissolved phosphorus was recorded at higher concentrations (mean: 0.16 ± 0.02 mg l−1 in Akaipur and 1.08 ± 0.12 mg l−1 in Bhomra). However, the higher level of water available phosphorus was not reflected in plankton production since the dominance of weeds suppresses their growth. This study recorded large accumulation of organic matter and nutrients in the form of detritus in these wetlands which may be channelized for fish production through stocking of suitable detritivorous fishes and/or reducing macrophyte coverage that would give space and nutrients for phytoplankton growth.

Divergent functioning of Proteaceae species: the South AmericanEmbothrium coccineumdisplays a combination of adaptive traits to survive in high‐phosphorus soils

SummaryProteaceae species in south‐western Australia thrive on phosphorus‐impoverished soils, employing a phosphorus‐mining strategy involving carboxylate‐releasing cluster roots. Some develop symptoms of phosphorus toxicity at slightly elevated soil phosphorus concentrations, due to their low capacity to down‐regulate phosphorus uptake. In contrast, Proteaceae species in Chile, e.g.Embothrium coccineumJ.R. Forst. &amp; G. Forst., occur on volcanic soils, which contain high levels of total phosphorus, but phosphorus availability is low.We hypothesised that the functioning of cluster roots ofE. coccineumdiffers from that of south‐western Australian Proteaceae species, in accordance with the difference in soil phosphorus status. With more phosphorus to be gained from the soil with high levels of total phosphorus, we expect less investment in biomass and more release of carboxylates. Furthermore, we hypothesised thatE. coccineumregulates its phosphorus‐uptake capacity, avoiding phosphorus toxicity when grown at elevated phosphorus levels. To test these hypotheses,E. coccineumseedlings were grown at a range of phosphorus supplies in nutrient solution.We show thatE. coccineumallocated at least five times less biomass to cluster roots that released at least nine times more carboxylates per unit cluster root weight compared with south‐western Australian species (e.g.Banksia,Hakea). The highest phosphorus supply caused a growth inhibition and high leaf phosphorus concentration, without symptoms of phosphorus toxicity. We accept our hypotheses on the functioning of cluster roots and the high capacity to reduce the net phosphorus uptake in plants grown at a high‐phosphorus supply.This novel combination of traits indicates divergent functioning of Proteaceae species from southern South America, exposed to frequent phosphorus input due to volcanic activity, in contrast with the functioning of south‐western Australian Proteaceae species that thrive on severely phosphorus‐impoverished soils. These traits could explain the functioning ofE. coccineumon soils that are rich in total phosphorus, but with a low concentration of available phosphorus.

Effects of agricultural land use on stream assemblages: Taxon-specific responses of alpha and beta diversity

Although biodiversity loss and homogenization of communities with increasing stress is an established axiom of pollution ecology, few studies have compared the concurrent response of multiple taxonomic groups to determine if environmental perturbation results in coherent patterns in assemblage composition. Here, data from 35 lowland European streams was used to explore the responses of multiple taxonomic groups to disturbance from agricultural land use, mainly gradients in total phosphorus (TP). We studied responses of fish, invertebrate, macrophyte and benthic diatom assemblages to TP, based on univariate metrics that characterize α-diversity (taxon richness, Simpson diversity, evenness, taxonomic distinctness) and abundance, and multivariate community structure. Multivariate dispersion was used to infer β-diversity characteristics in two groups of streams with low and high levels of TP. Three of the five metrics of α-diversity and abundance of primary producers were significantly related to resources, however, the direction of change was not always consistent with our predictions; macrophyte diversity decreased, whereas benthic diatom diversity increased with elevated nutrients. For consumers, taxon richness increased (fish) or decreased (invertebrates), while fish assemblages had lower phylogenetic diversity (taxonomic distinctness) associated with disturbance, implying a loss of functional diversity. In line with our predictions, fish and invertebrate assemblages showed homogenization of β-diversity with disturbance. Our finding that β-diversity of the two primary producers remained relatively high, while α-diversity either decreased (macrophytes) or increased (benthic diatoms), suggests that local disturbance is to some extent compensated for by among-site diversity. Our finding that secondary producers showed homogenization of β-diversity with disturbance has strong management perspectives, suggesting that these groups will need to be more carefully managed to maintain diversity at the landscape level, potentially sustaining resilient communities.

Influence of anthropogenic activities on microbial and nutrient levels along the Mara River tributaries, Kenya

Background: A number of factors impact negatively on natural surface water resources across the world. Although sources of surface water pollution are numerous, anthropogenic activities have been singled out as among the most important and of great concern. The aim of this study was to assess the influence of anthropogenic activities on nutrients and microbial levels along the Amala and Nyangores tributaries of the Mara River in Kenya. Materials and Methods: Four sampling sites along each tributary were specifically selected from which water samples were collected and analyzed for nutrients by use of spectrophotometric techniques, and coliform bacterial presence by a multiple tube fermentation technique. Results: Higher levels of total phosphorus were recorded along the Nyangores than the Amala tributary (P= 0.02). Significant differences in phosphorus levels were recorded between different sites along the Nyangores tributary (P= However, total nitrogen levels varied only within sites along the Nyangores tributary (P Conclusions: The findings imply that the health of local communities who depend on this water for domestic use might be compromised. As such, regular monitoring, strict enforcement of environmental protection laws, public education and proper sewage disposal is recommended.

The distribution of phytoplankton along trophic gradients and its mediation by available light in the pelagic zone of large eutrophic lakes

We describe the pattern and the principal factors affecting the phytoplankton biomass–nutrient relationship in the pelagic zone of large lakes. The results showed that the phytoplankton abundance and biomass of Cyanophyta, Cryptophyta, and Pyrrophyta were significantly correlated with trophic states. The total phosphorus (TP)–biomass relationship curves showed that the increment of biomass with TP is weak at high TP levels. The decrease in biomass at the high end of the curves might be a synthesis of the pattern of responses of the major taxonomic groups (except cyanobacteria) to environmental variables. Light limitation might be one of the important factors causing the decrease in the TP–biomass curve at high TP concentrations. If the mean underwater available light is lower than ∼250 µmol photons·m–2·s–1, clear-water species decline and cyanobacteria become dominant. The responses to available light of these key species play a central role in modulating the biomass–nutrient relationship. Our results contribute to the understanding of this relationship in the pelagic zone of large eutrophic lakes and have important practical implications for lake management.

Estimating reference nutrient criteria for Maryland ecoregions

Management of stream nutrients is becoming increasingly important in order to protect both water quality and aquatic resources throughout the USA. Using an extensive water quality database from the long-term Maryland Biological Stream Survey (MBSS), we describe nutrient relationships to landscape characteristics as total nitrogen (TN) and total phosphorus (TP) of small-order, non-tidal streams in USEPA L2 and L3 ecoregions in Maryland and by MBSS stream order at the L2 and L3 ecoregion levels. To protect stream ecosystem integrity, preliminary reference nutrient estimates (TN and TP) as percentiles (25th of all stream reaches and 75th of stream reference reaches) for the six Maryland L3 ecoregions are: Blue Ridge TN 0.29 and 0.64mg/L, TP 0.0065 and 0.0090mg/L; Central Appalachians TN 0.40 and 1.0mg/L, TP 0.0060 and 0.015mg/L; Middle Atlantic Coastal Plains TN 0.93 and 2.5mg/L, TP 0.094 and 0.065mg/L; Northern Piedmont TN 1.6 and 1.8mg/L, TP 0.010 and 0.015mg/L; Ridge and Valley TN 0.40 and 0.98mg/L, TP 0.0063 and 0.012mg/L; and Southeastern Plains TN 0.33 and 0.82mg/L, TP 0.016 and 0.042mg/L. High levels of both TN and TP are present in many streams found in non-tidal watersheds associated with all Maryland ecoregions, but are especially elevated in the Northern Piedmont and Middle Atlantic Coastal Plain ecoregions, with the latter second-order streams (average TN > 2.9mg/L) significantly higher than all other ecoregion-order combinations. Across all six ecoregions, mean nutrient loading for both TN and TP was generally equivalent in first-order streams to nutrient concentrations seen in both second- and third-order streams, indicating a definite need to increase efforts in preventing nutrients from entering first-order streams. Small-order stream nutrient levels are the drivers for subsequent TN and TP inputs into the upper freshwater tidal reaches of the Chesapeake Bay, resulting in a potential risk for altered estuarine ecosystems.