Excessive Levels Of Nutrients Research Articles

Phytoplankton communities and environmental variables as indicators of ecosystem productivity in a shallow tropical lake

The water quality and ecosystem productivity of a tropical lake in Ethiopia (Lake Arkiet) was evaluated using phytoplankton and environmental factors. This was to ascertaining the lake’s potential for various applications. Phytoplankton communities and some selected environmental variables were collected from two predefined sampling sites (open water and littoral) using a seasonal campaign between March to May (dry season) and June to August (wet season) in 2022. The analysis of the physicochemical characteristics of this study showed that the lake’s water was well-oxygenated (6.8–16.7 mg/L), warm (25.8–29.8 °C), turbid (154–317 NTU), had poor water transparency (4.3–16.1 cm), and was alkaline (pH = 7.29–11.31). The concentrations of inorganic nutrients (phosphate and nitrate) were notably high, ranging from 2.12–5.26 and 2.19–10.64 mg/L, respectively. A total of 34 phytoplankton taxa from four divisions were identified in Lake Arekit. Bacillariophyceae (18 taxa) and Chlorophyceae (10 taxa) were the major groups of phytoplankton which together represented the largest (82%) phytoplankton taxa. The total biovolume of phytoplankton in the lake was to be 384.15 mm3/L. Cyanobacteria contributed the largest (41%) phytoplankton biovolume followed by Bacillariophyta (32%). The highest biovolume (about 75%) was constituted in the Microcystis aeruginosa, Cylindrospermopsis raphidiopsis, Anabaena spiroides, Pediastrum duplex, Aulacoseira granulate, Navicula schroeteri, and Nitzschia palea. The distribution of environmental factors and phytoplankton communities showed greater seasonality. High phytoplankton biovolume was observed in the dry season at both sampling sites concurrently with high water transparency and low water temperature. Findings from this study revealed that Lake Arkeit was a moderately polluted but productive lacustrine ecosystem that can still support aquatic life, fish production, irrigation, and aquaculture. The primary source of the pollution is the entry of inorganic and organic wastes from a brewery and other water bottling industries nearby and around the lake, as well as possible excessive nutrient levels due to the lake’s geological background. It is advised that commercial factories stop producing or releasing waste in open spaces that are heavily washed and enter the lake via flooding and tributary rivers and streams. Additionally, the local government should work with the nearby communities to set up a buffer zone where people are prohibited from engaging in agricultural activities to protect and reduce pollution, which will help to preserve the lake’s water and ecosystem.

Prediction of Residual NPK Levels in Crop Fruits by Electronic-Nose VOC Analysis following Application of Multiple Fertilizer Rates

The excessive application of nitrogen in cucumber cultivation may lead to nitrate accumulation in fruits with potential toxicity to humans. Harvested fruits of agricultural crops should be evaluated for residual nitrogen, phosphorus, and potassium (NPK) nutrient levels. This is necessary to avoid nutrient toxicity from the consumption of fresh produce with excessive nutrient levels. Electronic noses are instruments well-suited for the nondestructive detection of fruit and vegetable quality based on volatile organic compound (VOC) emissions. This proof-of-concept study was designed to test the efficacy of using an electronic nose with statistical regression models to indirectly predict excessive fertilizer application based on VOC emissions from cucumber fruits grown under controlled greenhouse conditions to simulate field conditions but eliminate most environmental variables affecting plant volatile emissions. To identify excess nitrogen in cucumber plants, five different levels of urea fertilizer application rates were tested on cucumbers (control without fertilizer, 100, 200, 300, and 400 kg/ha). Chemometric methods, such as the partial least squares regression (PLSR) method, the principal component regression (PCR) method, and the multiple linear regression (MLR) method, were used to create separate regression models to predict nitrogen (N), phosphorus (P), and potassium (K) levels in cucumber fruits following application of different fertilizer rates to greenhouse soils. The correlation coefficients for the MLR model (based on the optimal parameters of PCR and PLSR) were 0.905 and 0.905 for the calibration sets and 0.900 and 0.900 for the validation sets, respectively. The nitrogen prediction model for fruit nitrates was more accurate than other nutrient models. The proposed method could potentially be used to indirectly detect excessive use of fertilizers in cucumber field crops.

High removal of nitrogen and phosphorus from black-odorous water using a novel aeration-adsorption system

Black-odorous waters are an increasingly common phenomenon characterized by excessive levels of nutrients, the formation of metal sufide precipitates, volatile sulfurous compounds, low dissolved oxygen and high chemical oxygen demand. Black-odorous waters frequently occur in lake and river systems where inputs have restricted circulation. The key remediation issue is the removal of nitrogen and phosphorus. Here, we present a novel aeration-adsorption system using fiber balls and we study treatment parameters and removal mechanism. Kinetics and changes of the solid phase were followed using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Results show complete removal of ammonia N, initially at 31 mg/L, and 92.8% removal of total nitrogen, initially at 29 mg/L, after a 24 h reaction time at pH 9.67. At pH 5.67 and 9.67, total phosphorus and phosphate could be significantly reduced by 90–92% at 3.2–5.2 mg/L after 24 h. Treatment met China’s integrated wastewater discharge standards, demonstrating an effective and robust treatment capability. First-order and second-order kinetic models provided a good fit to the treatment data, indicating physical and chemical adsorption were involved in the treatment reactions. The reaction mechanism involved hydrogen substitution and binding to oxygen. These results present a cost effective and robust approach for the removal of N and P from black, odorous water, providing opportunity to abate environmental contamination.

Eutrophication causes invertebrate biodiversity loss and decreases cross-taxon congruence across anthropogenically-disturbed lakes

Eutrophication is a major problem currently impacting many surface water ecosystems. Impacts of increased nutrient concentrations on biodiversity may differ between different scales, different organism groups, and different trophic states. Surveys at different spatial scales have suggested that biodiversity of different taxa may exhibit significant cross-taxon congruence. In our study, we examined the diversity of zooplankton and zoobenthos across 261 lakes in the Lake Taihu watershed, an area that is undergoing a severe eutrophication process. We tested the cross-taxon congruence in species richness and Shannon-Wiener diversity between zooplankton and zoobenthos along a nutrient gradient across the lakes. Our findings were consistent with the intermediate disturbance hypothesis, considering nutrient input as the disturbance. Also, we found significant cross-taxon congruence between zooplankton and zoobenthos diversities. Our results confirmed that excess nutrient levels resulted in diversity loss and community simplification. Zoobenthos were more sensitive to nutrient increases compared with zooplankton, which decreased cross-taxon congruence because these organism groups did not respond similarly to the anthropogenic disturbance.

Assessment of plant growth performance and nutrient release for application of phosphorus-loaded layered double hydroxides as fertilizer

Abstract Seed germination and early growth assays of lettuce (Lactuca sativa L.) were used as means in the evaluation of different dosage performances of P-loaded layered double hydroxides (P-LDHs). Of these two experiments, results from the former showed that P-LDH application at lower concentrations (0.5 and 1.0 g) influenced the slightly delayed germination, which decreased by no more than approximately 12% compared to that of untreated seeds, whereas the total germination failure was observed once seeds were established with higher ones (2.5 and 5.0 g) because of Al toxicity. Statistical analysis also revealed that a significant dose-dependent inhibition of seed germination was attained after P-LDH administration of at least 1.0 g. On the contrary, beneficial effects were obtained in the successive experiments, where P-LDHs at 0.5, 1.0, 2.5, and 5.0% (w/w) were applied to the growing media. P-LDHs applied at 1.0% outperformed other treatments as well as the control in stimulating plant improvement. The length of lettuce shoots and roots was improved by at least 6.75% compared to those of the non-treated samples and by 10.80% to 30.83% compared with other application rates. The greatest biomass accumulation (1.723 g) was also found in lettuce supplemented with 1.0% of P-LDHs, whereas those without P-LDHs reached their lowest fresh weight (1.422 g). In this experiment, an inadequate supply of Mg could be detrimental to plants from the last two treatment groups. In addition, findings of nutrient leaching verified that P stored in these products was released slowly, and thus they were able to deliver this essential nutrient to plants gradually over a longer period. In summary, this study pointed out that post-adsorption LDHs did not have the ability to boost seed germination, regardless, they could be reused as an agricultural fertilizer to encourage crop quality cultivated under substrate or soil conditions, where an application rate of 1.0% (w/w) was recommended in order to avoid the exposure of excess nutrient levels to the targeted plants.

Can ruminant urine-N rate and plants affect nitrate leaching and its isotopic composition?

ABSTRACTWorldwide there is an increasing awareness of the potential risks that pasture grazing systems pose to freshwater. Excess nutrient levels, predominately nitrate (), result in reduced water quality. This study focused on further understanding how the presence or absence of perennial ryegrass (Lolium perenne L) and bovine urine (BU) influenced both the isotopic signature and the amount of leached. Plant presence resulted in lower -N concentrations and reduced -N leaching over the nine-month trial period. A total of 15, 79 and 234 kg/N/ha was leached from the 0, 300 and 700 kg/N/ha BU treatments, respectively. Drainage volumes varied with season and plant treatments (plants 420±47 mm, no-plants 539±29 mm total drainage). The isotope values were found to be most influenced by plant treatment in the absence of BU. Under BU these isotopic signatures varied temporally due to denitrification and were influenced by plant treatment in the absence of BU, but this does not confound interpretation of isotope data when BU is applied. Nitrate isotopes show potential for identifying sources and soil processes forming and removing . Further datasets are required to improve our understanding of BU rate effects on the temporal dynamics.

Elevated O-GlcNAcylation enhances pro-inflammatory Th17 function by altering the intracellular lipid microenvironment

Chronic, low-grade inflammation increases the risk for atherosclerosis, cancer, and autoimmunity in diseases such as obesity and diabetes. Levels of CD4+ T helper 17 (Th17) cells, which secrete interleukin 17A (IL-17A), are increased in obesity and contribute to the inflammatory milieu; however, the relationship between signaling events triggered by excess nutrient levels and IL-17A-mediated inflammation is unclear. Here, using cytokine, quantitative real-time PCR, immunoprecipitation, and ChIP assays, along with lipidomics and MS-based approaches, we show that increased levels of the nutrient-responsive, post-translational protein modification, O-GlcNAc, are present in naive CD4+ T cells from a diet-induced obesity murine model and that elevated O-GlcNAc levels increase IL-17A production. We also found that increased binding of the Th17 master transcription factor RAR-related orphan receptor γ t variant (RORγt) at the IL-17 gene promoter and enhancer, as well as significant alterations in the intracellular lipid microenvironment, elevates the production of ligands capable of increasing RORγt transcriptional activity. Importantly, the rate-limiting enzyme of fatty acid biosynthesis, acetyl-CoA carboxylase 1 (ACC1), is O-GlcNAcylated and necessary for production of these RORγt-activating ligands. Our results suggest that increased O-GlcNAcylation of cellular proteins may be a potential link between excess nutrient levels and pathological inflammation.

Nutrient Sensor Challenge Winners Announced at ASLO Conference

The winners of the Nutrient Sensor Challenge were announced at a special awards session at the ASLO Aquatic Sciences Meeting in Honolulu, Hawaii, on Thursday, March 2. Launched in December 2014, the Nutrient Sensor Challenge aimed to accelerate the development, production, and use of affordable, reliable, and accurate nutrient sensors. These sensors will enable automated and high-resolution nutrient monitoring in aquatic environments ranging from freshwater lakes and streams to the coastal ocean. Nutrient pollution is one of the nation's most difficult environmental challenges. While nutrients are essential compounds for functioning ecosystems and the production of food, fiber, and livestock feed, excessive nutrient levels can dramatically alter aquatic environments and threaten economic and human health. An independent judging panel selected Systea S.p.A. as the winner for both Nitrate and Phosphate sensors. The Systea instruments represent a cost-effective, commercially available solution for measuring both nitrate and phosphate in an integrated package. It uses a wet chemistry approach to measure both nitrogen and phosphorus, and performed well in lab testing and across the three field deployments, including 72 days in Chesapeake Bay. The judging panel awarded an Honorable Mention for Innovation and Potential to the National Oceanography Centre (NOC) team. The NOC sensor represents a fundamentally new approach to the wet chemical in situ analyzer method, using chip-based microfluidics technology. Though some engineering challenges need to be addressed for continuous, full-scale field deployment, the sensor performed well in the lab and maintained accuracy and precision across a wide range. The sensor is also forecast to be near the Challenge goal for purchase price. For the past two years, the Challenging Nutrients Coalition has been working to facilitate the development of nutrient sensors that will provide the data needed to inform decisions to reduce nutrient loads on land, in the air, and in waterways and to track progress. The Coalition is an extensive collaboration between government agencies (including Environmental Protection Agency, National Oceanic and Atmospheric Administration, United States Geological Survey, and National Institute of Standards Technology), NGOs, and academia that deploys open innovation and incentive prize approaches to advance nutrient pollution management and reduction. To stimulate these new innovations, the Coalition launched the Nutrient Sensor Challenge in collaboration with the Alliance for Coastal Technologies (ACT). The challenge goal was for new, more accurate, precise and reliable technologies to be commercially available by 2017 for a purchase price of less than $5,000 and with other significant savings in cost-of-ownership. After two years of development, and rigorous field and laboratory testing by ACT, the winners were selected by an independent panel of expert judges. “Many thanks go to the many technology innovators, our technical advisory committee, and independent judging panel,” said Mario Tamburri, Executive Director of the Alliance for Coastal Technologies. “The next step is to get these next-generation sensors into the hands of users to help stop the nutrient pollution problem.” All instrument performance testing results will be available to the public in a series of individual verification reports published on the ACT website in April 2017. More information on the nutrient pollution issue, the Nutrient Sensor Challenge, and the winners can be found at www.nutrients-challenge.org. Denice Shaw from EPA Office of Research and Development presenting award to Pompeo Moscetta of Systea. Amy Pelsinsky, Director of Public Relations, University of Maryland Center for Environmental Science, Baltimore, MD, U.S.A., apelsinsky@umces.edu

Silicon facilitates manganese phytoextraction by cucumber (Cucumis sativus L.)

The effect of excess nutrient levels of manganese (Mn, 50 and 100 mM) on the growth inhibition and the appearance of Mn-toxicity symptoms in the leaves was studied in cucumber plants (Cucumis sativus L. cv. Chinese long). Silicon (Si), when supplied as 1.5 mM silicic acid, clearly decreased symptoms of Mn-toxicity despite approximately the same total Mn content in the leaves. In treated plants, Si improves growth and biomass production compared with that of non-Si treated plants. Inert deposition of Si in the leaf cell walls of cucumber (a Si-accumulating species) enhanced cell wall stability. The mechanism of Si protection is proposed to act by Si-induced compartmentation of Mn hence increasing Mn2+-binding sites in the cell wall (e.g. Mn-silicate polymers) finally resulting in decreased toxic free Mn within the plant tissue rather than decrease of Mn uptake. These results suggest that Si nutrition can improve the phytoextraction potential of plants due to enhanced metal tolerance in leaf tissues.

Agroecological and social characteristics of New York city community gardens: contributions to urban food security, ecosystem services, and environmental education

There is growing public interest and participation in food-producing urban community gardens in North America, yet little research has examined agricultural production and ecological processes in these spaces. We describe the agroecological and social characteristics of 61 food-producing gardens in New York City, drawing on gardener interviews, land-use maps, plant species inventories, arthropod scouting, and soil sampling and analysis. Gardens contained agricultural crops, food production infrastructure, ornamental plants, and recreational areas in varying proportions, indicating that gardens serve multiple and distinct purposes depending on community needs and interests. On average, gardeners devoted the greatest proportion of garden area (44 %) to food production, and supplied a large share of their households’ produce needs from their community gardens. Solanaceae, Brassicaceae, and Cucurbitaceae crops dominated food crop areas, hindering effective crop rotation to prevent disease and pest problems. Most gardeners grew crops in raised beds constructed with clean fill and compost. These soils generally had sandy textures, low water-holding capacity, high organic matter levels (with a large proportion from recent inputs) and excessive nutrient levels. Soil water content at field capacity increased exponentially with total soil carbon, suggesting that organic matter enhances water-holding capacity. Insect pest densities greatly exceeded action thresholds in nearly all gardens for aphids and whiteflies on Brassica crops, aphids on Cucurbit crops, and two-spotted spider mites on tomatoes. Predator and parasitoid densities were generally low (less than one per plant on average), perhaps partially due to low floral and woody perennial cover in most gardens (12 % and 9 % on average, respectively). Dominant groups of natural enemies were minute pirate bugs, spiders, and parasitoid wasps. A wide variety of people of differing experience levels, incomes, and ethnicities participate in community gardening in NYC, and most gardens host multiple languages. Promising directions for urban gardening research, education, and practice include: 1) Cover cropping to improve soil quality and nutrient management, and diversify crop rotations; 2) Improving access to soil testing and guidance on appropriate use of soil amendments, 3) Enhancing habitat for arthropod natural enemies that provide biological control of insect pests with floral and woody perennial plantings; and 4) Incorporating ecological knowledge and inquiry-based approaches into gardening workshops, educational materials, and technical support, and offering these resources in multiple languages.

A Model of Chronic Nutrient Infusion in the Rat

Chronic exposure to excessive levels of nutrients is postulated to affect the function of several organs and tissues and to contribute to the development of the many complications associated with obesity and the metabolic syndrome, including type 2 diabetes. To study the mechanisms by which excessive levels of glucose and fatty acids affect the pancreatic beta-cell and the secretion of insulin, we have established a chronic nutrient infusion model in the rat. The procedure consists of catheterizing the right jugular vein and left carotid artery under general anesthesia; allowing a 7-day recuperation period; connecting the catheters to the pumps using a swivel and counterweight system that enables the animal to move freely in the cage; and infusing glucose and/or Intralipid (a soybean oil emulsion which generates a mixture of approximately 80% unsaturated/20% saturated fatty acids when infused with heparin) for 72 hr. This model offers several advantages, including the possibility to finely modulate the target levels of circulating glucose and fatty acids; the option to co-infuse pharmacological compounds; and the relatively short time frame as opposed to dietary models. It can be used to examine the mechanisms of nutrient-induced dysfunction in a variety of organs and to test the effectiveness of drugs in this context.

Phytoplankton distribution in the Nador lagoon (Morocco) and possible risks for harmful algal blooms

1 - Phytoplankton populations and environmental parameters were analysed seasonally in the lagoon of Nador (Morocco) over an annual cycle (2006-2007) at six stations. Seven phytoplankton Classes were observed: Diatomophyceae, Dinophyceae, Raphidophyceae, Prasinophyceae, Euglenophyceae, Dictyochophyceae and Cyanophyceae. Seven taxa were identified that may present a risk of inducing harmful blooms i.e. Alexandrium minutum, Pseudonitzschia delicatissima and P. fraudulenta, Prorocentrum minimum, Prorocentrum rhatymum, Dinophysis sacculus, Gymnodinium catenatum and Karenia mikimotoi. Physico-chemical analyses were carried out on water samples: Dissolved Organic Carbon (DOC) and nutrients (NH4 +, NO3-, PO4 3- and SiO2).2 - Favourable and unfavourable factors for bloom development were identified. The possible relations between environmental parameters and the occurrence of potentially harmful phytoplankton blooms were investigated through a Factorial Discriminant Analysis. The proliferation of potentially harmful phytoplankton was linked to the availability of various nutrients (N, P, Si). Prorocentrum minimum tolerated waters with high nitrate contents, while Alexandrium minutum tolerated nutrientpoor waters. The most frequently observed taxa, Pseudonitzschia species and Dinophysis sacculus, were adapted to variations of water quality. Excessive levels of nutrients appeared as inhibiting for proliferation of potentially harmful phytoplankton which disappeared for the benefit of a very dense bloom of Tetraselmis sp. (Prasinophyceae).3 - A risk of toxicity was observed during all samplings throughout the lagoon, it was particularly pronounced during the summer sampling in the northern continental part of the lagoon with proliferation of Pseudonitzschia species.

The big picture of marsh loss

A landscape-scale experiment shows that excessive nutrient levels can cause the loss of salt marshes — a result that was not seen in smaller studies. This illustrates the value of large-scale, long-term studies in ecology. See Letter p.388 Salt marshes provide important ecosystem services such as storm protection for coastal cities, nutrient removal and carbon sequestration, but despite protective measures these ecosystems are in decline. Nine years of data from a whole-ecosystem nutrient-enrichment experiment now demonstrate that current levels of coastal nutrient loading can alter key salt-marsh-ecosystem properties, leading to the collapse of creek banks and, ultimately, the conversion of salt marsh into mudflat. The potential deterioration of coastal marshes owing to eutrophication adds another dimension to the challenge of managing nitrogen while meeting food-production demands in the twenty-first century.

Phosphorus: A Resource in Decline

This article discusses the decline in phosphorus resources due to its over‐production as a fertilizer. and as a result of phosphorus‐mining, the threat it poses as it enters the ecosystem as waste, thus leading to excessive nutrient levels in waterways. Pearl®, a nutrient recovery process technology developed by Ostara, a Vancouver, B.C., company, is presented as being effective at removing up to 20% of the phosphorus load to wastewater treatment plants. The Pearl process is based on a proprietary fluidized bed reactor in which magnesium is added to sludge dewatering liquor to precipitate struvite under a controlled chemical reaction.

More is not necessarily better: the impact of limiting and excessive nutrients on herbivore population growth rates

Abstract 1. The body tissues of insect herbivores contain higher concentrations of nitrogen and phosphorus than do their host plants, leading to an elemental mismatch that can limit herbivore growth, fecundity and ultimately influence population dynamics. While low nutrient availability can limit herbivore growth and reproduction, nutrient levels that exceed an organism’s nutritional requirements, i.e. an organisms’ threshold elemental ratio, can also decrease performance.2. We conducted a laboratory experiment to examine the impacts of nitrogen and phosphorus additions on population growth rates of a phloem‐feeding insect herbivore.3. Herbivore per capita population growth rates were highest at intermediate foliar nitrogen concentrations, indicating a performance cost on the highest nitrogen foliage. While there was no direct effect of foliar phosphorus concentration on insect performance, there was a strong and unexpected indirect effect. High soil phosphorus availability increased both foliar nitrogen concentrations and aphid tissue nitrogen, resulting in low population growth rates when both soil nitrogen and phosphorus availabilities were high.4. In this study, experimental increases in foliar nitrogen levels led to a decrease in herbivore performance suggesting that excessive nutrient levels can limit herbivore population growth rates.

Soil Test Nutrient Changes Induced by Poultry Litter under Conventional Tillage and No‐Tillage

Poultry litter (PL) can supply N, P, K, and other plant nutrients; however, excessive application may cause environmental problems, depending on management and crop nutrient demand. Changes in soil test (ST) nutrient content in a Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) during a 10‐yr period of PL use was evaluated at the USDA‐ARS J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. During the cotton (Gossypium hirsutum L.) cropping phase (1995–2000), 4.4 Mg PL ha−1 yr−1 resulted in small changes in ST nutrient content in the surface 15 cm. Differences were observed between tillage treatments, with less accumulation of Ca, Mg, and Mn and greater accumulation of Zn for no‐till (NT) than conventional tillage (CT). During the corn (Zea mays L.) cropping phase (2001–2005), average annual PL inputs (11.2 Mg ha−1) increased P and Zn contents, with changes being similar for CT and NT. After 10 yr, ST nutrient contents in the surface 15 cm reflected 25, 4, 45, 26, 17, and 97% of the input from PL for P, K, Ca, Mg, Mn, and Zn, respectively. Changes in soil profile nutrient content (to a depth of 60 cm) from 1997 to 2005 were predominantly at 0 to 15 cm, where P and Zn increased >200%. Accumulation of Ca, K, P, and Zn at lower depths was also observed. Strategies for increasing nutrient removal following repeated long‐term application of PL should be considered to avoid excessive levels of nutrients.

Looking for metrics to assess the trophic state of ponds. Macroinvertebrates and amphibians

1. Ponds are particularly rich habitats and play an essential role in the conservation of aquatic biodiversity. Therefore it is necessary to develop a specific method for evaluating their biological integrity, and particularly their water quality. Metrics have proved to be efficient for studies on running waters. Such an approach would be particularly useful for ponds and therefore needs to be tested. 2. Eight metrics based on the richness of invertebrates and amphibians and 73 others derived from the biological/ecological trait categories linked to Coleoptera, Odonata and Gastropoda were tested for their potential as indicators of the trophic state of 94 ponds in Switzerland. The relationships between these metrics and the state of water eutrophication were explored. 3. Four metrics based on richness responded to excessive nutrient levels in the colline vegetation belt. These were: aquatic Coleoptera species richness; the pooled species richness of aquatic Coleoptera, aquatic Gastropoda, adult Odonata and Amphibia (COGA); the family-level richness of macroinvertebrates and the family-level richness of the combined Megaloptera and Odonata groups (MO). At altitudes above 800m (i.e. montane-subalpine and alpine vegetation belts), two to four other metrics were identified as pond water-quality indicators. 4. Furthermore, many trait categories were sensitive to excessive nutrient levels. In the colline belt. 13 out of the 33 metrics derived from the biological/ecological traits responded to an increase in the trophic state (i.e. at least one metric for each of the three invertebrate groups tested). However, the patterns of the relationships are unclear and further investigations are required to identify and select the relevant metrics for an assessment of water quality. 5. In conclusion, for the future assessment of pond quality, four metrics derived from richness could be taken into consideration. Nevertheless. further investigations are required to identify the biological/ecological traits that could be combined with these richness metrics.

Effect of Whole Wheat Dilution on Performance and Carcass Characteristics of Male Turkeys

Field trials and published research suggest that it is possible to dilute commercial turkey and broiler chicken rations with whole wheat and suffer little or no loss in performance. It has been hypothesized that birds fed whole wheat have improved gizzard health and are able to self-select whole grain to better meet their individual nutritional needs. In 6 dietary treatments, the effect of diluting turkey diets with different amounts of whole and pelleted wheat was investigated. In the diets diluted with whole wheat, the whole wheat was blended with the other feed ingredients after they had been steam pelleted. In the diets diluted with pelleted wheat, the extra wheat used to dilute the rations was ground and then blended with the other ingredients prior to pelleting. The influence of adding extra synthetic amino acids to diluted diets was also studied. All diets were supplemented with a commercial feed enzyme. Dilution, without extra synthetic amino acid supplementation, resulted in large reductions in body weight, feed efficiency, and breast meat yield. At the highest level of dilution, where whole wheat dilution was 50% of the diet, body weight and weight of breast meat per bird were reduced by 15 and 20%, respectively. No advantage was observed in diluting with whole wheat compared with pelleted wheat. Addition of extra synthetic amino acids restored 66% of the body weight and 56% of the breast meat lost at the highest level of whole wheat dilution. These results suggest that reports of successful dilution of poultry rations are more likely due to formulation with excess nutrient levels of the undiluted diets rather than to a specific benefit to feeding whole grain.

GIS‐BASED HYIROLOGIC MODELING OF RIPARIAN AREAS: IMPLICATIONS FOR STREAM WATER QUALITY1

ABSTRACT: Riparian buffers have potential for reducing excess nutrient levels in surface water. Spatial variation in riparian buffer effectiveness is well recognized, yet researchers and managers still lack effective general tools for understanding the relevance of different hydrologic settings. We present several terrain‐based GIS models to predict spatial patterns of shallow, subsurface hydrologic flux and riparian hydrology. We then link predictions of riparian hydrology to patterns of nutrient export in order to demonstrate potential for augmenting the predictive power of land use/land cover (LU/LC) maps. Using predicted hydrology in addition to LUILC, we observed increases in the explained variation of nutrient exports from 290 sites across Lower Michigan. The results suggest that our hydrologic predictions relate more strongly to patterns of nutrient export than the presence or absence of wetland vegetation, and that in fact the influence of vegetative structure largely depends on its hydrologic context. Such GIS models are useful and complimentary tools for exploring the role of hydrologic routing in riparian ecosystem function and stream water quality. Modeling efforts that take a similar GIS approach to material transport might be used to further explore the causal implications of riparian buffers in heterogeneous watersheds.

PHENOTYPIC PLASTICITY IN POLYGONUM PERSICARIA. III. THE EVOLUTION OF ECOLOGICAL BREADTH FOR NUTRIENT ENVIRONMENT.

Norms of reaction for a number of growth and reproductive characters were determined for 15 randomly sampled Polygonum persicaria genotypes, from two natural populations originating in sites with very different nutrient availabilities. Under severely limiting nutrient conditions, these genotypes shared not only plastic responses such as increased root-to-shoot ratio, but a surprising constancy in such functionally essential characters as leaf area ratio, leaf nitrogen concentration, and propagule nitrogen content. Because functional homeostasis depends on flexibility in underlying characters, similar homeostatic results can be achieved through different combinations of underlying plastic and fixed responses in genetically different entities. For example, plants in each population maintained a relatively constant propagule nitrogen content under extreme low-nitrogen conditions by varying either the size or the tissue nitrogen concentration of propagules. These genotypes also tolerated excessive nutrient levels toxic to many plants, evidently by storing excess nutrients in shoots. Although development was altered under such circumstances, reproductive fitness was maintained.