Mussel-derived stimulation of benthic filamentous algae: The importance of nutrients and spatial scale

The reoccurrence of benthic filamentous algal (FA) blooms in the Great Lakes, without associated increases in phosphorus loading, has stimulated renewed interest in determining the causes of Great Lakes benthic algal blooms. We investigated the potential roles of invasive mussels and nutrient limitation with experimental substrata within inner Saginaw Bay. FA abundance on live mussel substrata was typically significantly greater than that on inert (empty shell or rock) substrata. Nutrient addition (from an artificial source) significantly increased FA abundance on inert substrata. These results suggest that: 1) mussel nutrient excretion could be a primary stimulatory mechanism; 2) mussel-mediated stimulation may be even stronger in other, more oligotrophic, Great Lakes nearshore zones; and 3) increased nutrient loading to inner Saginaw Bay may exacerbate existing FA blooms. FA abundance on inert substrata was not affected, even in close proximity to mussels, indicating that the observed stimulatory effect of mussel-derived P on live mussels attenuated at very small spatial scales, on the order of centimeters or less.     

Nutrient flows in smallholder production systems in the humid forest zone of southern Cameroon

The flows and balances of N, P and K were studied in 20 farms in the Campo Ma’an area in Cameroon between March and August 2002 to assess the nutrient dynamics in smallholder farms. Data were collected through farmer interviews, field measurements and estimates from transfer functions. Nutrient input from mineral (IN1), animal feed (IN2a) and inorganic amendments (IN2b) was absent. Major outputs were through crop (OUT1a) and animal (OUT1b) products sold. Partial budgets for farmer managed flows were negative: −65 kg N, −5.5 kg P and −30.8 kg K ha⁻¹ year⁻¹. For inflows not managed by farmers, deep capture (IN6) was the major source: 16.6, 1.4 and 6.6 kg ha⁻¹ year⁻¹ of N, P and K, respectively. Atmospheric deposition (IN3) was estimated at 4.3 kg N, 1.0 kg P and 3.9 kg K ha⁻¹ year⁻¹, and biological nitrogen fixation (IN4) at 6.9 kg N ha⁻¹ year⁻¹. Major losses were leaching (OUT 3a): 26.4 kg N, and 0.88 kg K ha⁻¹ year⁻¹. Gaseous losses from the soil (OUT 4a) were estimated at 6.34 kg N, and human faeces (OUT 6) were estimated at 4 kg N, 0.64 kg P and 4.8 kg K ha⁻¹ year⁻¹. The highest losses were from burning (OUT 4c), i.e. 47.8 kg N, 1.8 kg P and 14.3 kg K ha⁻¹ year⁻¹. Partial budgets of environmentally controlled flows were negative only for N −4.8 kg N, +2.4 kg P and +9.6 kg K ha⁻¹ year⁻¹. The overall farm budgets were negative, with annual losses of 69 kg N, 3 kg P and 21 kg K ha⁻¹. Only cocoa had a positive nutrient balance: +9.3 kg N, +1.4 kg P and +7.6 kg K ha⁻¹ year⁻¹. Nutrients reaching the household waste (1.9 kg N, 2.8 kg P and 18.8 kg K ha⁻¹ year⁻¹), animal manure (4.9 kg N, 0.4 kg P and 1.6 kg K), and human faeces (4 kg N, 0.64 kg P and 4.8 kg K ha⁻¹ year⁻¹) were not recycled. Five alternative management scenarios were envisaged to improve the nutrient balances. Recycling animal manure, household waste and human faeces will bring the balance at −62.6 kg N, 0 kg P and +1 kg K ha⁻¹ year⁻¹. If, additionally, burning could be avoided, positive nutrient balances could be expected.     

Faecal separation for nutrient management––evaluation of different separation techniques

The aim of this study was to evaluate the potential of different separation techniques for local recovery of faecal nutrients. Separation by Aquatron, filtration, flotation and sedimentation was tested in the laboratory. Only the separation of faecal matter from flushwater was investigated. For efficient nutrient capture, the system has to be combined with urine-diverting toilets.In this study we found that the extraction of nutrients from the faeces to the liquid occurred rapidly. Therefore, to effectively separate the faecal nutrients and particles from the flushwater, the separation has to be performed locally, preferably at house level.The Aquatron and the filtration gave a fraction of separated solids with 10% dry matter, which contained 70–80% of the incoming plant nutrients nitrogen, phosphorus and potassium. The other two methods investigated did not prove effective for local separation of faeces.Using urine-diverting toilets, where all the urine is diverted, and collected and 70% of the faecal nutrients are separated locally, the potential for local nutrient recovery from the household wastewater is 88% for nitrogen, 75% for phosphorus and 55% for potassium, mainly in the form of directly plant available nutrients.     

Molecular Structure of Feeds in Relation to Nutrient Utilization and Availability in Animals: A Novel Approach

The invention and development of new research concepts, novel methodologies, and novel bioanalytical techniques are essential in advancing the animal sciences, which include feed and nutrition science. This article introduces a novel approach that shows the potential of advanced synchrotron-based bioanalytical technology for studying the effects of molecular structural changes in feeds induced by various treatments (e.g., genetic modification, gene silencing, heat-related feed processing, biofuel processing) in relation to nutrient digestion and absorption in animals. Advanced techniques based on synchrotron radiation (e.g., synchrotron radiation infrared microspectroscopy (SR-IMS) and synchrotron radiation X-ray techniques) have been developed as a fast, noninvasive, bioanalytical technology that, unlike traditional wet chemistry methods, does not damage or destroy the inherent molecular structure of the feed. The cutting-edge and advanced research tool of synchrotron light (which is a million times brighter than sunlight) can be used to explore the inherent structure of biological tissue at cellular and molecular levels at ultra-high spatial resolutions. In conclusion, the use of recently developed bioanalytical techniques based on synchrotron radiation along with common research techniques is leading to dramatic advances in animal feed and nutritional research.     

Chemical characterization of Opuntia dillenii and Opuntia ficus indica fruits

The chemical compositions (moisture, °Brix, total fibre, protein, fat, ash, pH, acidity, ascorbic acid, total phenolics, Na, K, Ca, Mg, Fe, Cu, Zn, Mn, Ni and Cr) were determined in fruits belonging to two species of prickly pear, Opuntia ficus indica and Opuntia dillenii, from Tenerife Island. The chemical compositions of the two species were clearly different. However, no important differences were observed between orange and green prickly pears within the specie O. ficus indica. An important contribution to the intakes of fibre, ascorbic acid, Mn, Cr and total phenolics is provided by the consumption of prickly pears, particularly from fruits of O. dillenii. Applying factor and/or discriminant analysis, the prickly pear samples were differentiated according to the species, altitude and region of cultivation in the island.     

Modelling nutrient transport in hollow fibre membrane bioreactor for growing bone tissue with consideration of multi-component interactions

Current work in bone tissue engineering (BTE) suggests that hollow fibre membrane bioreactors (HFMBs) can be used to grow artificial bone tissue which may then be implanted in humans to treat various bone defects. The HFMBs mimic the blood capillary networks in human bones and are able to maintain high concentrations of nutrients by minimising mass transfer distance. To further establish this method and to develop effective BTE protocols, nutrient transport behaviour in the HFMB must be characterised. By doing so, the quantitative relationships between the cell environments and, bioreactor operating conditions and designs can be elucidated. This also paves the way for possible improvement and optimisation of the HFMB performance. However, characterising the nutrients transport properties in HFMB are not straightforward as online measurements of key parameters are almost impossible at the moment. This is due to the very small size and the stringent operating conditions of the bioreactors. Hence, much work is needed on mathematical modelling of mass transport in these bioreactors. In this paper, we present a rigorous framework for modelling mass transport in HFMB for growing bone tissue. In particular, we consider the effects of hydrodynamics and multi-component interactions on nutrient transport profiles. The developed framework is then used to study the behaviour of nutrient transport in HFMB for bone tissue growth for various operating conditions with a view to generalise their effects as far as possible. Maxwell-Stefan, Navier-Stokes and reaction kinetic equations are combined to quantify the multi-component nutrient transport behaviour in the bioreactor. The framework also relies on the use of a single hollow fibre (Krogh cylinder assumption), which is representative of the whole fibre bundle. The numerical solutions of the governing model equations are obtained using finite element method. The effects of different bioreactor designs (e.g., fibre length, lumen thickness, etc.) and process parameters (e.g., nutrient inlet concentration, fluid velocity, etc.) on multi-component nutrient concentration profiles (e.g., glucose and oxygen) are simulated. The results show that the HFMB designs and process parameters may be optimised to further enhance mass transport for growing bone tissues.     

Comprehensive life cycle inventories of alternative wastewater treatment systems

Over recent decades, the environmental regulations on wastewater treatment plants (WWTP) have trended towards increasingly stringent nutrient removal requirements for the protection of local waterways. However, such regulations typically ignore other environmental impacts that might accompany apparent improvements to the WWTP. This paper quantitatively defines the life cycle inventory of resources consumed and emissions produced in ten different wastewater treatment scenarios (covering six process configurations and nine treatment standards). The inventory results indicate that infrastructure resources, operational energy, direct greenhouse gas (GHG) emissions and chemical consumption generally increase with increasing nitrogen removal, especially at discharge standards of total nitrogen <5 mgN L⁻¹. Similarly, infrastructure resources and chemical consumption increase sharply with increasing phosphorus removal, but operational energy and direct GHG emissions are largely unaffected. These trends represent a trade-off of negative environmental impacts against improved local receiving water quality. However, increased phosphorus removal in WWTPs also represents an opportunity for increased resource recovery and reuse via biosolids applied to agricultural land. This study highlights that where biosolids displace synthetic fertilisers, a negative environmental trade-off may also occur by increasing the heavy metals discharged to soil. Proper analysis of these positive and negative environmental trade-offs requires further life cycle impact assessment and an inherently subjective weighting of competing environmental costs and benefits.     

Ammonium removal from digested sludge liquors using ion exchange

Liquors arising from the dewatering of digested sludge typically contain ammonium levels in the range 200-700mgl(-1) NH(4)(+)-N. These liquors are frequently recycled to the head of the wastewater treatment works (WwTW) untreated and can constitute >25% of the total nitrogen load entering the works at inlet. This paper investigates the use of a clay-based material, MesoLite, as an ion exchange medium for ammonium removal from recycle streams. Pilot-scale studies performed at Didcot WwTW, part of the Thames Water wastewater treatment network, indicate that MesoLite is highly selective for the ammonium ion. Results show that >95% of ammonium was removed from belt press liquors with an initial ammonium nitrogen concentration >600mgl(-1), with an overall ion exchange capacity >51g NH(4)(+)-Nkg(-1) medium and this resulted in an operating capacity in the range 27-36gNH(4)(+)-Nkg(-1).     

马齿苋的营养成分与药用价值

马齿苋是在我国生长甚广的一种野生蔬菜,含有蛋白质、脂肪、维生素等多种营养物质。马齿苋还含有生理活性物质,对人体具有保健作用。药理研究证明,马齿苋具有预防心脏病、消炎抗菌、清除尘毒、止血化瘀等功效。     

灌水和钾用量对烤烟干物质积累及养分吸收的影响

采用大田试验研究了灌水和钾肥用量对烤烟干物质积累及养分吸收的影响。结果表明,灌水和施用钾肥均可以促进烤烟干物质积累和养分吸收,显著提高叶片氮、钾含量。其中,灌水对增进烤烟干物质积累和烟株吸收磷素的效应大于施用钾肥,而施用钾肥对增加烤烟吸收氮素和钾素的作用大于灌水,水钾耦合对烤烟干物质积累和烟株养分吸收均有不同程度的正互作效应。