Showing papers by "University of Western Australia published in 1991"

Efficient lipid staining in plant material with sudan red 7B or fluorol [correction of fluoral] yellow 088 in polyethylene glycol-glycerol.

Abstract: Polyethylene glycol (400) with 90% glycerol (aqueous) is introduced as an efficient solvent system for lipid stains. Various lipid-soluble dyes were dissolved in this solvent system and tested for their intensity, contrast, and specificity of staining of suberin lamellae in plant tissue. The stability (i.e., lack of precipitation) of the various staining solutions in the presence of fresh tissue was also tested. When dissolved in polyethylene glycol-glycerol, Sudan red 7B (fat red) was the best nonfluorescent stain and fluorol yellow 088 (solvent green 4) was an excellent fluorochrome. These two dyes formed stable staining solutions which efficiently stained lipids in fresh sections without forming precipitates. Estimations of the solubilities of these dyes in the solvent compared with their solubilities in lipids of various chemical types indicated that they should both be effective stains for lipids in general.

Overtraining in athletes. An update.

Abstract: Overtraining appears to be caused by too much high intensity training and/or too little regeneration (recovery) time often combined with other training and nontraining stressors. There are a multitude of symptoms of overtraining, the expression of which vary depending upon the athlete's physical and physiological makeup, type of exercise undertaken and other factors. The aetiology of overtraining may therefore be different in different people suggesting the need to be aware of a wide variety of parameters as markers of overtraining. At present there is no one single diagnostic test that can define overtraining. The recognition of overtraining requires the identification of stress indicators which do not return to baseline following a period of regeneration. Possible indicators include an imbalance of the neuroendocrine system, suppression of the immune system, indicators of muscle damage, depressed muscle glycogen reserves, deteriorating aerobic, ventilatory and cardiac efficiency, a depressed psychological profile, and poor performance in sport specific tests, e.g. time trials. Screening for changes in parameters indicative of overtraining needs to be a routine component of the training programme and must be incorporated into the programme in such a way that the short term fatigue associated with overload training is not confused with the chronic fatigue characteristic of overtraining. An in-depth knowledge of periodisation of training theory may be necessary to promote optimal performance improvements, prevent overtraining, and develop a system for incorporating a screening system into the training programme. Screening for overtraining and performance improvements must occur at the culmination of regeneration periods.

Review of seafloor spreading around Australia. I. synthesis of the patterns of spreading

Abstract: The existing data on Late Mesozoic and Cenozoic seafloor spreading isochrons (reviewed in the companion paper by Veevers & Li) and fracture zone trends provide the basis for 12 reconstructions of the seafloor around Australia that spread during the dispersal of Argo Land, India, Antarctica, Lord Howe Rise/New Zealand and the Papuan Peninsula. The major changes of plate geometry in the Jurassic, Early Cretaceous, mid‐Cretaceous, early Paleocene and early Eocene reflect global events. The pattern of spreading around Australia was determined by two long‐standing (earlier Phanerozoic) factors that operated in a counter‐clockwise direction: (1) penetration from the northwest by the Tethyan divergent ridge; and (2) rotation from the northeast of the Pacific convergent arc and back‐arc. The only new feature of the modern pattern is the deep penetration by the Indian Ocean ridge into eastern Gondwanaland to fragment it into continents in contrast with the pattern up to 160 Ma ago of breaking off micro‐continents.

On the Nature of Turbulence in a Stratified Fluid. Part I: The Energetics of Mixing

Abstract: The definition of the flux Richardson number Rf is generalized to be the ratio of the turbulent buoyancy flux b to the net turbulent mechanical energy m available from all sources. For mechanically energized turbulence where turbulence kinetic energy is used to sustain an upward buoyancy flux (b > 0), it is shown the magnitude of Rf is quantitatively determined by the location of the event in the FrT,–ReT where FrT and –ReT are the local instantaneous overturn Froude number and Reynolds number. In this parameter space the value of Rf varies between 0 and 0.20 for a fluid with Prandtl number greater than one, and between 0 and 0.15 for a fluid with a Prandtl number less than one. For turbulence sustained by a negative buoyancy flux (b < 0), such as penetrative convection in a cooling surface layer, it is shown that the flux Richardson number Rf is a fraction of depth below the surface Rf−1 varies between 0.55 at the surface and –∞ towards the base of the surface layer where the buoyancy flux vanis...

Towards Understanding Skeletal Muscle Regeneration

Abstract: Factors which effect proliferation and fusion of muscle precursor cells have been studied extensively in tissue culture, although little is known about these events in vivo. This review assesses the tissue culture derived data with a view to understanding factors which may control the regeneration of mature skeletal muscle in vivo. The following topics are discussed in the light of recent developments in cell and molecular biology: 1) Injury and necrosis of mature skeletal muscle fibres 2) Phagocytosis of myofibre debris 3) Revascularisation of injured muscle 4) Activation and proliferation of muscle precursor cells (mpc) in vivo Identification of mpcs; Satellite cell relationships; Extracellular matrix; Growth factors; Hormones; Replication. 5) Differentiation and fusion of muscle precursor cells in vivo Differentiation; Fusion; Extracellular matrix; Cell surface molecules: Growth factors and prostaglandins 6) Myotubes and innervation.

Antifungal antibiotics produced by Trichoderma spp

Abstract: In recent years plant pathologists and commercial companies have shown considerable interest in the application of biological control agents. Trichoderma spp have received particular attention as agents for the biological control of fungai pathogens of plants and appear to be likeiy candidates for successful exploitation in the future. Despite extcnsivc research over the last 50 years on the capability of Trichoderma spp to reduce the incidence of disease caused by soil-borne plant pathogens, the mcchanisms by which disease control is achicvcd are not clearly understood. The mechanisms suggcstcd to bc involved in biocontrol by thcsc fungi arc antibiosis, lysis, competition. mycoparasitism and promotion of plant growth (Hcnis, 1984; Papavizas, 1985; Chet, 1987; Baker, 1988; Lynch, 1990) It seems rcasonablc to assume that successful antagonism may rely on a combination of these modes of action. In this rcvicw we document the ability of Tri~hodermu spp to produce antibiotics and discuss the nature and possible ecological relevance of the antibiotics produced by these fungi. Four reviews on Trichoderma have appeared in recent years (Evcleigh, 1985; Papavizas, 1985; Taylor, 1986; Chct, 1987) but none have specifically considered these topics.

The effect of soil disturbance on vesicular-arbuscular mycorrhizal fungi in soils from different vegetation types

Abstract: summary The infectivity of vesicular–arbuscular (VA) mycorrhizal fungi in three soils from different vegetation types was compared before and after disturbance. The relative quantities of infective propagules in the disturbed soils were estimated by an infectivity test after the soils were diluted. Spare numbers and mycorrhizal roots were also quantified in each soil. The mycorrhizal colonization of clover roots in the infectivity st was not decreased after soil from an annual pasture had been disturbed. In contrast, in both a forest soil and a heathland soil, the percentage root length colonized of test plants was almost halved if the soils had been disturhtd. In the pasture soil up to 10 times or 25 times more propaguies survived disturbance than in the forest soil or the heathland soil respectively. The large number of propaguies may allow the VA mycorrhizal fungi in the pasture soil to maintain maximum infectivity after soil disturbance.

Longitudinal assessment of changes in reproductive hormones during normal pregnancy.

Abstract: The concentrations of hormones measured in serum from maternal blood change dramatically during pregnancy. While the relative contributions of sex steroids shift from maternal ovaries and adrenals to the fetoplacental unit, other maternal tissues such as pituitary and liver respond to increasing concentrations of estrogen and secrete increasing amounts of prolactin and sex-hormone-binding globulin. To determine longitudinal changes in circulating maternal hormones, we collected blood from 60 women on three occasions during their pregnancies. We observed a 1.7-fold increase in testosterone concentration in serum; concentrations of sex-hormone-binding globulin in serum rose 5.6-fold. The major increase (6.8-fold) in estradiol in serum occurred within the first 16 weeks, followed by a further 4.8-fold increase by term. Mean concentrations of progesterone, 17-hydroxyprogesterone, and androstenedione in serum increased 11.9-, 3-, and 1.3-fold, respectively, whereas concentrations of dehydroepiandrosterone sulfate (DHEAS) fell by 50%. Mean serum prolactin concentrations increased 3.8-fold during the first trimester and by a similar amount during the final 24 weeks of pregnancy. We used these data, obtained from a cohort of women with uncomplicated pregnancies, to construct reference intervals for hormones in maternal serum.

Pigmentary and cutaneous risk factors for non-melanocytic skin cancer—A case-control study

Abstract: The roles of ethnic origin, pigmentary traits, sun sensitivity and other cutaneous characteristics as risk factors for basal-cell carcinoma (BCC) and squamous-cell carcinoma (SCC) were examined in a case-control study of prevalent and incident cases of histopathologically confirmed skin cancers. Two hundred and twenty six confirmed cases of BCC, 45 of SCC and 1,015 controls with no lesions were identified in a population-based survey of skin cancer in 1987 in Geraldton, Western Australia. The risk of both cancers was higher in native-born Australians than in migrants. The risk of BCC decreased with increasing age at arrival in Australia. Southern European ancestry was strongly protective against BCC (for any southern European grandparents) and SCC (no case of SCC had any grandparents of southern European origin). Inability to tan was the strongest pigmentary risk factor for both BCC and SCC. Among factors that incorporated a measure of sun exposure as well as sun sensitivity, freckling on the arm in childhood was important for both cancers, the number of moles on the back was important for BCC, and forearm skin colour and having a permanent colour difference between the neck and adjacent protected areas were important for SCC. Among measures of sun damage to the skin, solar elastosis of the neck was a strong risk factor for both BCC and SCC, loss of fine texture of the skin of the back of the hands (as measured by cutaneous microtopography) was important for BCC and telangiectasia of the face for SCC. When all important variables for each cancer were examined together in a single model with age, sex, migrant status or age at arrival in Australia, and ethnicity, in ability to tan, solar elastosis of the neck, and the number of moles on the back were independently significant risk factors for BCC and solar elastosis of the neck and having a permanent colour difference between the neck and adjacent protected areas were independently significant risk factors for SCC. The effects of age at arrival or migrant status and ethnic origin remained important in the models incorporating these factors. A history of ever having acne and a history of warts were protective for BCC and a history of acne was protective for SCC.

A test of the human sperm acrosome reaction following ionophore challenge. Relationship to fertility and other seminal parameters.

Abstract: Acrosome reaction capacity was tested on semen samples from 53 fertile and 26 subfertile men. Preparations were divided into two aliquots after 3 or 24 hours of culture. One aliquot received 10 mumol/L calcium ionophore A23187 in dimethyl sulfoxide (DMSO) and the other received DMSO alone. Acrosome reactions were scored on ethanol-permeabilized smears using fluorescein isothiocyanate (FITC)-conjugated Pisum sativum lectin. The following factors were analyzed: the spontaneous reaction rates (control); induced reaction rates (ionophore-challenged); and the difference between the two, being the proportion of spermatozoa in the population capable of reacting in response to calcium influx (acrosome reaction to ionophore challenge [ARIC]). While spontaneous reactions bore no relation to fertility, induced reactions and ARICs were significantly reduced or absent in subfertile men, indicating acrosomal dysfunction as a likely cause of fertilization failure. The test was shown to have a predictive value for fertility comparable to that of the hamster ovum sperm penetration assay and to be a simple and cost-effective addition to existing semenology.

Reflex sympathetic dystrophy: the significance of differing plasma catecholamine concentrations in affected and unaffected limbs.

Abstract: SUMMARY In 26 patients with features of reflex sympathetic dystrophy, venous blood was collected from painful and unaffected limbs. Levels of plasma adrenaline, noradrenaline and its intracellular metabolite, 3,4-dihydroxyphenylethyleneglycol (DHPG), were measured by combined gas chromatography/mass spectrometry. Plasma DHPG was lower on the painful side. Concentration of plasma noradrenaline was also lower on the painful side in patients with widespread allodynia, and in those with hyperhidrosis in the affected hand or foot. These findings do not support the widely held view that autonomic disturbances in reflex sympathetic dystrophy are due to sympathetic overactivity. Rather, they suggest that sweating and changes in peripheral blood flow result from supersensitivity to sympathetic neurotransmitters. After injury, supersensitivity to noradrenaline may also contribute to spontaneous pain and allodynia by disrupting efferent sympathetic modulation of sensation. This would explain why pain and allodynia are relieved by sympathetic blockade, and why noradrenaline rekindles pain in sympathectomized skin.

Contrast adaptation and contrast masking in human vision.

Abstract: After a preliminary study of visual evoked potentials (VEPS) to a test grating seen in the presence of masks at different orientations, psychophysical data are presented showing the effects of adaptation and of masking on thresholds for detecting the same test grating. The test is a vertical grating of spatial frequency 2 cycles per degree; adapting and masking gratings differ from the test either in orientation or in spatial frequency. The effects of adaptation and masking are explained by a single mechanism model that assumes: (i) adaptation and masking both alter the contrast response (or transducer) function of the mechanism that detects the test; (ii) masks, but not adaptors, stimulate the mechanism that detects the test; and (iii) a test is detectable when it raises response level by a constant amount. The model incorporates two distinct tuning functions, a broad adaptive contrast function and a narrow effective contrast function. It accounts adequately for all the data, including the location and size of the facilitative dip found in some masking functions, the constant slopes of the threshold elevation segments of adaptation functions and the varying slopes of masking functions. It also predicts the sometimes surprising joint effects of adaptation followed by masking and of two masks operating simultaneously.

On the Nature of Turbulence in a Stratified Fluid. Part II: Application to Lakes

Abstract: A strong debate has continued for a number of years over the magnitude of the ratio of the buoyancy flux b to the rate of production of turbulent kinetic energy from the mean velocity sheer. This ratio has traditionally been called the flux Richardson number Rf. In part I of Ivey and Imberger this definition was generalized by broadening the denominator to include all sources and sinks of mechanical turbulent kinetic energy, the net being defined as m. It was shown that for mechanically energized turbulence (m > 0, b > 0) the magnitude of Rf was completely determined by the magnitude of the overturn Froude FrT and the Reynolds ReT numbers By contrast, for the penetrative convection case (b < 0) Rf was shown to be dependent only on the distance from the source of buoyancy. In the present contribution, scaling arguments are presented for the magnitudes of FrT and ReT. It is shown that these may vary widely and depend, in the first instance, on the physics of the underlying processes energizing the ...

Restricted gene flow in a moving hybrid zone of the newts triturus cristatus and t. marmoratus in western france.

Abstract: Two hybridizing species of newts, Triturus cristatus and T. marmoratus, with overlapping distributions show a parapatric distribution when surveyed in detail. The factors that govern the distribution of cristatus vs. marmoratus in the departement (province) of Mayenne in western France are identified as forestation and relief. The parapatric hybrid zone running through Mayenne is narrow but widens to approximately 20 km in an area with mixed habitat. In this area most breeding sites are shared and F1 hybrids form about 4% of the total population. Analysis of survey data collected about 30 years previously also shows an essentially parapatric distribution. Comparison of past and present distribution maps reveals that cristatus has superseded marmoratus over large areas in the south of Mayenne. An area where marmoratus replaced cristatus also exists, but it is more limited in size. Gene flow between cristatus and marmoratus is analyzed using 10 diagnostic genetic markers [9 protein loci and mitochondrial (mt) DNA]. In syntopic populations nuclear gene flow is bidirectional with a mean frequency of introgressed alleles (f) of 0.3%. In allotopic populations of cristatus and marmoratus gene flow is present in areas of species replacement (f = 0.3%), while gene flow appears to be absent in those areas that have been continuously occupied by a single species. At the biogeographic level, the presence or absence of introgression is paralleled by the persistence or absence, respectively, of pockets of cristatus-marmoratus syntopy. All F1 hybrids possess the cristatus type mtDNA. This may be due to asymmetric interspecific mate choice and would explain the observed absence of introgression of the maternally inherited mtDNA genome in areas where cristatus replaced marmoratus. The cristatus-marmoratus hybrid zone bears characteristics of both the clinal (parapatric) hybrid zone model and the mosaic hybrid zone model. Such a mixed model-for which we propose the term "reticulate hybrid zone"-can be appreciated only if studied over a two-dimensional geographic area and also through time.

A carboxyl-terminal peptide from the parathyroid hormone-related protein inhibits bone resorption by osteoclasts.

Abstract: PTH-related protein (PTHrP) interacts, via its amino-terminal 34 residues, with PTH receptors on osteoblasts to stimulate osteoclastic bone resorption indirectly. We now report that mature hPTHrP-f 1-141) (EC50, -l0-11 M) and a carboxyl-terminal fragment, PTHrP-(107–139) (EC50, -10-15 M), are potent inhibitors of resorption in an isolated rat osteoclast bone resorption assay, whereas hPTHrP-(l–108) and hPTHrP-(1–34) are inactive in this respect. PTHrP-(107–139) also inhibits resorption in a rat long bone organ culture system and reduces osteoclast spreading. PTHrP-(107–139) does not act on osteoclasts via a cAMP signal transduction mechanism, but its effects may be mediated by protein kinase-C. This previously unrecognized action of PTHrP, to inhibit osteoclastic bone resorption directly, indicates that PTHrP may be a precursor of multiple biologically active peptides with differing physiological functions. (Endocrinology 129: 1762–1768, 1991)

Displaying proportions and percentages

Abstract: Pie and bar charts are commonly used to display percentage or proportional data, but professional data analysts have frowned on the use of the pie chart on the grounds that judgements of area are less accurate than judgements of lenth. Thus the bar chart has been favoured. When the amount of data to be communicated is small, some authorities have advocated the use of properly constructed tables, as another option. The series of experiments reported here suggests that there is little to choose between the pie and the bar chart, with the former enjoying a slight advantage if the required judgement is a complicated one, but that both forms of chart are superior to the table. Thus our results do not support the commonly expressed opinion that pie charts are inferior. An analysis of the nature of the task and a review of the psychophysical literature suggest that the traditional prejudice against the pie chart is misguided.

Optimal stiffness of series elastic component in a stretch-shorten cycle activity

Abstract: Twelve experienced male weight lifters performed a rebound bench press and a purely concentric bench press lift. Data were obtained pertaining to 1) the benefits to concentric motion derived from a prior stretch and 2) the movement frequency adopted during performance of the stretch-shorten cycle (SSC) portion of the rebound bench press lift. The subjects also performed a series of quasi-static muscular actions in a position specific to the bench press movement. A brief perturbation was applied to the bar while these isometric efforts were maintained, and the resulting damped oscillations provided data pertaining to each subject's series elastic component (SEC) stiffness and natural frequency of oscillation. A significant correlation (r = -0.718, P less than 0.01) between maximal SEC stiffness and augmentation to concentric motion derived from prior stretch was observed. Subjects were also observed to perform the SSC portion of the rebound bench press movement to coincide with the natural frequency of oscillation of their SEC. These results are interpreted as demonstrating that the optimal stiffness in a rebound bench press lift was a resonant-compliant SEC.

Biologically active metabolites from Xenorhabdus spp., Part 1. Dithiolopyrrolone derivatives with antibiotic activity.

Abstract: Five related antibiotic compounds, named xenorhabdins, were isolated from cultures of Xenorhabdus spp., bacteria symbiotically associated with insect-pathogenic nematodes. Their chemical structures were elucidated by X-ray crystallography, nmr, and mass spectral analyses to be N-acyl derivatives of either 6-amino-4,5-dihydro-5-oxo-1,2-dithiolo [4,3-b] pyrrole (compounds 1-3) or 6-amino-4,5-dihydro-4-methyl-5-oxo-1,2-dithiolo[4,3-b] pyrrole (compounds 4 and 5). They are previously unreported members of the pyrrothine family of antibiotics. Antimicrobial and insectidical activities were found. These metabolites are specific to phase one Xenorhabdus.

Transferrin and iron uptake by the brain: effects of altered iron status.

Abstract: Transferrin (Tf) and iron uptake by the brain were measured in rats using 59Fe-125I-Tf and 131I-albumin (to correct for the plasma content of 59Fe and 125I-Tf in the organs). The rats were aged from 15 to 63 days and were fed (a) a low-iron diet (iron-deficient) or, as control, the same diet supplemented with iron, or (b) a chow diet with added carbonyl iron (iron overload), the chow diet alone acting as its control. Iron deficiency was associated with a significant decrease and iron overload with a significant increase in brain nonheme iron concentration relative to the controls. In each dietary treatment group, the uptake of Tf and iron by the brain decreased as the rats aged from 15 to 63 days. Both Tf and iron uptake were significantly greater in the iron-deficient rats than in their controls and lower in the iron-loaded rats than in the corresponding controls. Overall, iron deficiency produced about a doubling and iron overload a halving of the uptake values compared with the controls. In contrast to that in the brain, iron uptake by the femurs did not decrease with age and there was relatively little difference between the different dietary groups. 125I-Tf uptake by the brains of the iron-deficient rats increased very rapidly after injection of the labelled proteins, within 15 min reaching a plateau level which was maintained for at least 6 h. The uptake of 59Fe, however, increased rapidly for 1 h and then more slowly, and in terms of percentage of injected dose reached much higher values than did 125I-Tf uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the biomass and species composition of macroalgae in a eutrophic estuary

Abstract: More than 20 years of data are presented on the macroalgal biomass, species composition and water quality of Peel-Harvey estuary in south-western Australia. The occurrence of macroalgal blooms was a sudden event in the late 1960s, and appears to have resulted from nutrient availability surpassing a threshold of some kind. Cladophora dominated the system until 1979 and appears to have had a competitive advantage in deep-water areas because of its morphology. A catastrophic event compounded by a series of unfavourable conditions resulted in the loss of Cladophora from the deep areas and its estuary-wide replacement by Chaetomorpha, which was more competitive in the shallows. Since 1979, changes in water quality have been reflected in changes in biomass and species composition in the system. Average annual biomass is linearly related to average light attenuation over the summer growth period. Periods of high nutrient concentrations favour Ulva and Enteromorpha, while Chaetomorpha resumes dominance during periods of lower mean nutrient concentrations. Nutrient concentrations appear to be more influential on an inter-annual than seasonal scale, except in the case of Ulva which, on the basis of tissue N and P concentrations, is seasonally nitrogen-limited. Light attenuation appears to have seasonal and long-term effects. The data support the hypothesis of other workers that inter-annual differences in hydrographic events and phytoplankton dynamics influence macroalgal dynamics. The concept is examined further in light of this extensive database.

An unusually strong Einstein ring in the radio source PKS1830–211

Abstract: High-resolution radio images of PKS1830 - 211 are obtained to study the possibility that the double structure is a gravitationally lensed object. The VLBI observations, taken from interferometric radiotelescope networks, reveal an elliptical ring that connects two bright spots of similar composition. Because the lens and the lensed object are closely aligned, and because of the structure of the two spots, the source is concluded to be a radio Einstein ring. The source is found to be close to the galactic plane, and the lens and the lensed object are extragalactic. The source is also found to be unusually bright, suggesting that it is aligned with a bright background source or amplified by some mechanism related to a source that is not so bright.

Relapse versus reinfection with Clostridium difficile.

Abstract: Relapse of Clostridium difficile-associated diarrhoea occurs in 15-20% of patients; however, whether relapse is due to an endogenous source of the organism or reinfection from the environment remains unclear. Restriction enzyme analysis (REA) of chromosomal DNA was used to type multiple isolates from ten patients who had experienced apparent relapses. More than half the relapses were due to infection with a new strain of C. difficile. The remaining patients were infected with the same strain, but whether this strain was acquired from the environment or from endogenous sources could not be determined. Relapses with a different strain of C. difficile could occur if an individual harboured more than one strain in their gastrointestinal tract. To investigate this possibility ten other patients were assessed for carriage of multiple strains. Ten colonies from a primary culture plate from each patient were typed by REA and tested for their ability to produce cytotoxin. All isolates from the same patient were identical by both methods, indicating that multiple carriage of strains may be a rare event.

Macroalgal-sediment nutrient interactions and their importance to macroalgal nutrition in a eutrophic estuary

Abstract: The potential for algal banks to influence water quality and sediment nutrient flux was examined through laboratory experiments and in situ monitoring of algal banks. Loose macroalgal banks displayed seasonal changes in tissue nutrient concentrations suggesting a strong dependence on water column nutrients. These banks fail to generate conditions suitable to sediment nutrient release. Dense banks generated low oxygen conditions in the inter-algal water (0–1 mg l−1), corresponding to zones of high, and relatively stable, phosphate and ammonium concentrations (up to 96 μg l−1 PO4P and 166 μg l−1 NH4N). Laboratory experiments confirmed that macroalgal banks can generate reducing conditions at the sediment surface, regardless of the aeration regime, through the decomposition of macroalgal tissue. Platinum electrode potentials as low as −200 mV were recorded in the inter-algal water. In such banks, redox-dependent sediment nutrient release and anaerobic accumulation of nitrogen accounted for inter-algal nutrient concentrations of over 60 μg l−1 phosphate and 800 μg l−1 ammonium. The generation of reducing conditions in inter-algal water required 7 days of still conditions and so this mechanism of nutrient generation is unlikely to be important in winter, when strong winds frequently shift the algal banks. It is suggested that in summer this mechanism may provide a source of nutrients to dense algal banks, supplementing reserves stored in winter.