Low-mass molecular dynamics simulation for configurational sampling enhancement: More evidence and theoretical explanation

It has been reported recently that classical, isothermal–isobaric molecular dynamics (NTP MD) simulations at a time step of 1.00 fs of the standard-mass time (Δt=1.00 fs^smt) and a temperature of ≤340 K using uniformly reduced atomic masses by tenfold offers better configurational sampling than standard-mass NTP MD simulations at the same time step. However, it has long been reported that atomic masses can also be increased to improve configurational sampling because higher atomic masses permit the use of a longer time step. It is worth investigating whether standard-mass NTP MD simulations at Δt=2.00 or 3.16 fs^smt can offer better or comparable configurational sampling than low-mass NTP MD simulations at Δt=1.00 fs^smt. This article reports folding simulations of two β-hairpins showing that the configurational sampling efficiency of NTP MD simulations using atomic masses uniformly reduced by tenfold at Δt=1.00 fs^smt is statistically equivalent to and better than those using standard masses at Δt=3.16 and 2.00 fs^smt, respectively. The results confirm that, relative to those using standard masses at routine Δt=2.00 fs^smt, the low-mass NTP MD simulations at Δt=1.00 fs^smt are a simple and generic technique to enhance configurational sampling at temperatures of ≤340 K.     

Characteristics in coarse woody debris mediated by forest developmental stage and latest disturbances in a natural secondary forest of Pinus tabulaeformis

Coarse woody debris (CWD) characteristics are expected to reflect forest stand features. Few studies evaluated logging-induced stand characteristics of secondary coniferous forests by quantifying the quality and quantity in CWD. After selective logging, the form of secondary forest of Pinus tabulaeformis in the Qinling Mountains is inferior and the regeneration is poor. We measured the CWD characteristics of the forest which had an average CWD biomass amount of 12.56 t hm⁻², and was predominated by abundant logs (65.68%), followed by snags (33.13%). The CWD biomass of P. tabulaeformis and Toxicodendron vernicifluum was significantly higher than that of other species, which took up 85.51% of the total. Although there was no significant difference among different diameter sizes (P > 0.05), the CWD biomass of diameter 30–40 cm occupied 46.26% of the total (5.81 t hm⁻²). Similarly, the CWD biomass of decay class I and II accounted for 39.89% (5.01 t hm⁻²) and 33.04% (4.15 t hm⁻²) of the total CWD biomass respectively, despite no significant difference among those 5 decay classes (P > 0.05). The results indicated that the combination of young forest developmental stage caused by past selective logging and natural and anthropogenic disturbances such as strong wind, tapping lacquer, firewood collection, and illegal tree felling played a crucial role in distribution characteristics of CWD in this secondary forest of P. tabulaeformis.     

The stability and thermodynamic parameters of a very thermostable and calcium-independent α-amylase from a newly isolated bacterium,Anoxybacillus beppuensis TSSC-1

Anoxybacillus beppuensis TSSC-1 (GenBank Number, EU710556), a thermophilic bacterium isolated from a hot spring reservoir, was found to optimally secrete a monomeric α-amylase at 55 °C and pH 7. The enzyme was purified to homogeneity by a single-step purification on phenyl sepharose 6FF, achieving a 58% yield, 10,000 U/mg specific activity and 19.5 fold purification. The molecular weight, K_m and V_max were 43 kD, 0.5 mg ml^?1 and 3571.42 μmol ml^?1 m^?1, respectively. The enzymatic catalysis of soluble starch was optimum at 80 °C and pH 7. The thermodynamic parameters, K_d, t_1/2, ΔH*, ΔS*, E and ΔG*, were consistent. The very compact structure of the enzyme and the transitional enzyme–substrate complex resisted denaturation at extreme temperatures and alkaline pH. The K_d and t_1/2 measurements were consistent with the high thermostability and pH tolerance observed. The structural stability of the enzyme was also reflected by the values of ΔH*, ΔS*, E and ΔG*. While the enzyme did not exhibit metal ion dependency, it was resistant to chemical denaturation. The broad thermo- and pH-tolerance of this enzyme suggests potential commercial opportunities.     

Shape matters in sampling plant diversity: Evidence from the field

The identification of shape and size of sampling units that maximises the number of plant species recorded in multiscale sampling designs has major implications in conservation planning and monitoring actions. In this paper we tested the effect of three sampling shapes (rectangles, squared, and randomly shaped sampling units) on the number of recorded species. We used a large dataset derived from the network of protected areas in the Siena Province, Italy. This dataset is composed of plant species occurrence data recorded from 604 plots (10 m × 10 m), each divided in a grid of 16 contiguous subplot units (2.5 m × 2.5 m). Moreover, we evaluated the effect of plot orientation along the main environmental gradient, to examine how the selection of plot orientation (when elongated plots are used) influences the number of species collected. In total, 1041 plant species were recorded from the study plots. A significantly higher species richness was recorded by the random arrangement of 4 subplots within each plot in comparison to the ‘rectangle’ and ‘square’ shapes. Although the rectangular shape captured a significant larger number of species than squared ones, plot orientation along the main environmental gradient did not show a systematic effect on the number of recorded species. We concluded that the choice of whether or not using elongated (rectangular) versus squared plots should dependent upon the objectives of the specific survey with squared plots being more suitable for assessing species composition of more homogeneous vegetation units and rectangular plots being more suited for recording more species in the pooled sample of a large area.     

Tree species composition rather than diversity triggers associational resistance to the pine processionary moth

The reduction of insect herbivory is one of the services provided by tree diversity in forest ecosystems. While it is increasingly acknowledged that the compositional characteristics of tree species assemblages play a major role in triggering associational resistance to herbivores, underlying mechanisms are less well known. We addressed this question in the ORPHEE experiment by assessing pine processionary moth infestations (Thaumetopoea pityocampa) across a tree diversity gradient from pine monocultures to five species mixtures. We showed that tree species richness per se had no effect on the probability of attack by this pest. By contrast, the infestation rate was strongly dependent on plot composition. Mixtures of pines (Pinus pinaster) and birches (Betula pendula) were less prone to T. pityocampa infestations, whereas mixtures of pines and oaks (Quercus spp.) were more often attacked than pine monocultures. By taking into account the relative height of pines and associated broadleaved species, this effect could be explained by pine apparency. Pines were on average 343 ± 5 cm height. Birches, as fast growing trees, were slightly taller than pines (363 ± 6 cm), while oak trees were significantly smaller (74 ± 1 cm). Host trees of T. pityocampa were then partly hidden in mixtures of pines and birches but more apparent in mixtures with oaks. We suggest that reduced pine apparency disrupted visual cues used by female moths to select host trees prior to oviposition. This study highlights the need to take into account tree traits such as growth rate when selecting the tree species that have to be associated in order to improve forest resistance to pest insects.     

Spatial distribution of soil penetration resistance as affected by soil compaction: The fractal approach

Using semivariograms and fractal dimension (D), we identified the spatial variation of penetration resistance (PR) in variously compacted silty loam in the Lublin region, South-East Poland. Four compaction treatments were as follows: zero traffic (0p), one pass of tractor (1p), three passes of tractor (3p), and (8p) eight passes. Penetration resistance was measured in a square net of 0.6 m × 0.6 m with grid density of 0.05 m, in horizontal planes at depths of 0.05, 0.15, 0.25, 0.35, 0.45 and 0.55 m in each traffic treatment. The data were analysed in 6 horizontal planes and 12 vertical planes. The vertical planes were obtained by transforming the measured data along one side of the square at every 0.05 m. Total number of penetrations was 864. Fractal dimension (D) was estimated from the slope of the log–log semivariogram plots. The semivariograms showed spatial autocorrelation of penetration resistance in the horizontal and vertical planes. Direction in space was important in this study. In the horizontal planes the differentiation of penetration resistance semivariance at different depths was considerable and not clearly related with traffic intensity. In the vertical planes the semivariograms showed spatial dependence of the PR and evident decreasing of semivariance with increasing traffic intensity. Kriging-interpolated maps revealed that the differentiation of penetration resistance was higher in the vertical than in the horizontal planes. The vertical differentiation was higher in 0p than in the remaining treatments. The overall mean fractal dimensions in the vertical planes increased with increasing compaction levels and can be a useful indicator of the compaction level. The opposite courses of fractal dimension in the vertical and horizontal planes indicate spatial anisotropy in distribution of penetration resistance.     

Horizontal transmission of the Picea glauca foliar endophyte Phialocephala scopiformis CBS 120377

We have studied the presence of the foliar endophtye of Picea glauca (white spruce) Phialocephala scopiformis CBS 120377 and its affect on the growth of Choristoneura fumiferana (spruce budworm). Here we examine the transmission of this fungus from 50 trees planted in a test field site to 250 P. glauca seedlings planted under the emerging canopies. After 3 y, the endophyte spread to 40 % of these trees (now 20–30 cm) with an average rugulosin (an anti-insect toxin) concentration of 1 μg g^?1. All woody plants within 2 m of the test trees were collected. These were all shown to be negative for P. scopiformis except for some spruce seedlings that arose from seeds (natural generation). This is positive evidence for the horizontal transmission of P. scopiformis and its apparent specificity to P. glauca under field conditions.     

The Quételet index revisited in children and adults

BackgroundThe body mass index (BMI) is based on the original concept that body weight increases as a function of height squared. As an indicator of obesity the modern BMI assumption postulates that adiposity also increases as a function of height in states of positive energy balance.ObjectiveTo evaluate the BMI concept across different adiposity magnitudes, in both children and adults.MethodsWe studied 975 individuals who underwent anthropometric evaluation: 474 children and 501 adults. Tetrapolar bioimpedance analysis was used to assess body fat and lean mass.ResultsBMI significantly correlated with percentage of body fat (%BF; children: r = 0.893; adults: r = 0.878) and with total fat mass (children: r = 0.967; adults: r = 0.953). In children, body weight, fat mass, %BF and waist circumference progressively increased as a function of height squared. In adults body weight increased as a function of height squared, but %BF actually decreased with increasing height both in men (r = −0.406; p < 0.001) and women (r = −0.413; p < 0.001). Most of the BMI variance in adults was explained by a positive correlation of total lean mass with height squared (r² = 0.709), and by a negative correlation of BMI with total fat mass (r = −0.193).ConclusionsBody weight increases as a function of height squared. However, adiposity progressively increases as a function of height only in children. BMI is not an ideal indicator of obesity in adults since it is significantly influenced by the lean mass, even in obese individuals.     

Purification,kinetic and thermodynamic characterization of soluble acid invertase from sugarcane (Saccharum officinarum L.)

We report for the first time kinetic and thermodynamic properties of soluble acid invertase (SAI) of sugarcane (Saccharum officinarum L.) salt sensitive local cultivar CP 77-400 (CP-77). The SAI was purified to apparent homogeneity on FPLC system. The crude enzyme was about 13 fold purified and recovery of SAI was 35%. The invertase was monomeric in nature and its native molecular mass on gel filtration and subunit mass on SDS-PAGE was 28 kDa. SAI was highly acidic having an optimum pH lower than 2. The acidic limb was missing. Proton transfer (donation and receiving) during catalysis was controlled by the basic limb having a pKa of 2.4. Carboxyl groups were involved in proton transfer during catalysis. The kinetic constants for sucrose hydrolysis by SAI were determined to be: k_m = 55 mg ml^?1, k_cat = 21 s^?1, k_cat/k_m = 0.38, while the thermodynamic parameters were: ΔH* = 52.6 kJ mol^?1, ΔG* = 71.2 kJ mol^?1, ΔS* = ?57 J mol^?1 K^?1, ΔG*_E–S = 10.8 kJ mol^?1 and ΔG*_E–T = 2.6 kJ mol^?1. The kinetics and thermodynamics of irreversible thermal denaturation at various temperatures 53–63 °C were also determined. The half -life of SAI at 53 and 63 °C was 112 and 10 min, respectively. At 55 °C, surprisingly the half -life increased to twice that at 53 °C. ΔG*, ΔH* and ΔS* of irreversible thermal stability of SAI at 55 °C were 107.7 kJ mol^?1, 276.04 kJ mol^?1 and 513 J mol^?1K^?1, respectively.     

Scales characterising a high density thin layer of Dinophysis acuta Ehrenberg and its transport within a coastal jet

An investigation into the distribution of Dinophysis spp. in coastal waters off the south coast of Ireland was carried out in July 2007. Dinophysis acuta was present as a sub surface layer containing up to 55,000 cells L⁻¹. The population had a high percentage of viable cells (mean: 89%; median: 94%; n = 24) with a high specific division rate (∼0.55 d⁻¹). The layer, of approximately 5 m thickness, did not coincide with the fluorescence maximum and was present as a patch of horizontal dimension less than 10 km × 7 km. Both conventional and towed undulating CTD used in conjunction with high vertical resolution sampling methods showed the patch of Dinophysis to move with a similar speed and direction as the coastal flow, which ran parallel to the coast in the form of a coastal jet with speed of the order of 6.5–7 km day⁻¹. The implications of the alongshore transport of populations of harmful species in coastal jets for monitoring programmes and predictive models are discussed.     

N-acetylcysteine prevents glucose/glucose oxidase-induced oxidative stress,mitochondrial damage and apoptosis in H9c2 cells

AimsHigh blood glucose may auto-oxidize and generate free radicals, which are proposed to induce apoptosis in cardiac cells. The aim of the present study was to investigate the cell damage induced by glucose/glucose oxidase-dependent oxidative stress and the protective effect of N-acetylcysteine (NAC) on H9c2 cardiac muscle cells.Main methodsH9c2 cells were exposed to 33 mM glucose (G) + 1.6 milliunits (mU) of glucose oxidase (GO) and termed G/GO. Cell apoptosis, generation of reactive oxygen species (ROS-super oxide anion and hydrogen peroxide) and reactive nitrogen species (RNS-peroxinitrite), and the change in mitochondrial membrane potential (ΔΨm) was studied using flow cytometry and confocal microscopy, and cytochrome c release was measured using confocal microscopy. The expression of Bcl-2, Bax and the activation of procaspase-9 was studied by western blot.Key findingsExposure of H9c2 cells to G/GO resulted in a significant increase in cellular apoptosis (P < 0.05) and the generation of ROS and RNS (P < 0.001). Further, G/GO treatment led to a decrease in ΔΨm, release of cytochrome c, decrease in Bcl-2, increase in Bax expression and the activation of procaspase-9. Treatment with NAC significantly decreased apoptosis (P < 0.05) and reduced the levels of ROS and RNS (P < 0.001). NAC was also able to normalize ΔΨm, inhibit cytochrome c release, increase Bcl-2 and decrease Bax expression and procaspase-9 activation.SignificanceOur studies suggest that NAC has antioxidative and antiapoptotic activity against G/GO-induced oxidative stress through the inhibition of mitochondrial damage in H9c2 cells.     

Mapping biodiversity in three-dimensions challenges marine conservation strategies: The example of coralligenous assemblages in North-Western Mediterranean Sea

Multi-facet diversity indices have been increasingly widely used in conservation ecology but congruence analyses both on horizontal and vertical axes have not yet been explored. We investigated the vertical and horizontal distributions of α and β taxonomic (TD), functional (FD) and phylogenetic diversity (PD) in a three-dimensional structured ecosystem. We focused on the Mediterranean coralligenous assemblages which form complex structures both vertically and horizontally, and are considered as the most diverse and threatened communities of the Mediterranean Sea. Although comparable to tropical reef assemblages in terms of richness, biomass and production, coralligenous assemblages are less known and more rarely studied, in particular because of their location in deep waters. Our study covers the entire range of distribution of coralligenous habitats along the French Mediterranean coasts, representing the most complete database so far developed for this important ecosystem. To our knowledge, this is the first analysis of spatial diversity patterns of marine biodiversity on both horizontal and vertical scales.Our study revealed that taxonomic diversity differed from functional and phylogenetic diversity patterns at the station level, the latter two being strongly structured by depth, with shallower stations generally richer than deeper ones. Considering all stations, phylogenetic diversity was less congruent to taxonomic diversity (Pearson's correlation of r = 0.48) but more congruent to functional diversity (r = 0.69) than randomly expected. Similar congruence patterns were revealed for stations deeper than 50 m (r = 0.44 and r = 0.84, respectively) but no significantly different congruence level than randomly expected was revealed among diversity facets for more shallow stations. Mean functional α- and β-diversity were lower than phylogenetic diversity and even lower than taxonomic α- and β-diversity for both vertical and horizontal scales. Low FD and PD values at both α- and β-diversity indicated functional and phylogenetic clustering. Community dissimilarities (β-diversity) increased over depth especially in central and eastern part of the French Mediterranean littoral and in northern Corsica, indicating coralligenous vertical structure within these regions. Overall horizontal β-diversity was higher within the 50–70 m depth belts.We conclude that taxonomic diversity alone is inadequate as a basis for setting conservation goals for this ecosystem and additional information, at least on phylogenetic diversity, is needed to preserve the ecosystem functioning and coralligenous evolutionary history. Our results highlight the necessity of considering different depth belts as a basis for regional scale conservation efforts. Current conservation approaches, such as the existing marine protected areas, are insufficient in preserving coralligenous habitats. The use of multi-facet indices should be considered, focusing on preserving local diversity patterns and compositional dissimilarities, both vertically and horizontally.     

The age of monumental olive trees (Olea europaea) in northeastern Spain

Trees can reach ages that in some cases amount to thousands of years. In the Mediterranean region, olive trees (Olea europaea) have traditionally been considered a particularly long-lived species. The main objective of this study was to assess the age of large olive trees considered to be millenarian and classified as monumental trees in northeastern Spain. We extracted cores of 14 individuals and obtained 8 sections of trees which had already been cut in the area where the largest olive trees in the northeastern Iberian Peninsula are found. The age of the sampled olive trees was assessed by counting the number of annual growth rings. Tree rings did not cross-date well, neither within nor between individuals, but boundaries between likely annual rings were clearly distinct. We found a linear relationship between DBH and tree age (in years) (Age = 2.11 × diameter(cm) + 88.93, R² = 0.80), which was used to estimate the age of unsampled olive trees. The maximum estimated age (627 ± 110 years) is among the greatest ages reported for olive trees around the world (700 years) and among the oldest trees in Mediterranean ecosystems.     

Structural characterization of thermostable,solvent tolerant,cytosafe tannase from Bacillus subtilis PAB2

Tannase production by Bacillus subtilis PAB2, was investigated under solid state fermentation using tamarind seed as sole carbon source and it was found as the highest titer (73.44 U/gds). The enzyme was purified to homogeneity, which showed the molecular mass around 52 kDa (K_m = 0.445 mM, V_max = 125.8 mM/mg/min and K_cat = 2.88 min^–1). The enzyme was found stable in a range of pH (3.0–8.0) and temperature (30–70 °C) with an optimal activity at pH 5.0, pI of 4.4 and at 40 °C temperature. It exhibited half-life (t_1/2) of 4.5 h at 60 °C. The enzyme comprised a typical secondary structure containing α-helix (9.3%), β-pleated sheet (33.6%) and β-turn (17.2%). The native conformation of the enzyme was alike a 44 nm spherical nanoparticle upon aggregation. Thermodynamic parameters of tannase revealed that it was stable at 40 °C and showed Q₁₀, ΔG_d and ΔS_d values of 2.08, 99.37 KJ/mol and 252.38 J mol⁻¹ K⁻¹, respectively. Organic solvents were stimulatory with regard to enzyme activity. Moreover, the altered enzyme activity was determined to be correlated with the changes in structural conformation in presence of inducer and inhibitor. Tannase was explored to have no cytotoxicity on Vero cell line as well as rat model study.     

The interface of hypothalamic–pituitary–adrenocortical axis and circulating brain natriuretic peptide in prediction of cardiopulmonary performance during physical stress

Brain natriuretic peptide (NT-pro-BNP) was implicated in the regulation of hypothalamic–pituitary–adrenocortical (HPA) responses to psychological stressors. However, HPA axis activation in different physical stress models and its interface with NT-pro-BNP in the prediction of cardiopulmonary performance is unclear. Cardiopulmonary test on a treadmill was used to assess cardiopulmonary parameters in 16 elite male wrestlers (W), 21 water polo player (WP) and 20 sedentary age-matched subjects (C). Plasma levels of NT-pro-BNP, cortisol and adrenocorticotropic hormone (ACTH) were measured using immunoassay sandwich technique, radioimmunoassay and radioimmunometric techniques, respectively, 10 min before test (1), at beginning (2), at maximal effort (3), at 3rd min of recovery (4). In all groups, NT-pro-BNP decreased between 1 and 2; increased from 2 to 3; and remained unchanged until 4. ACTH increased from 1 to 4, whereas cortisol increased from 1 to 3 and stayed elevated at 4. In all groups together, ΔNT-pro-BNP2/1 predicted peak oxygen consumption (B = 37.40, r = 0.38, p = 0.007); cortisol at 3 predicted heart rate increase between 2 and 3 (r = −0.38,B = −0.06, p = 0.005); cortisol at 2 predicted peak carbon-dioxide output (B = 2.27, r = 0.35, p < 0.001); ΔACTH3/2 predicted peak ventilatory equivalent for carbon-dioxide (B = 0.03, r = 0.33, p = 0.003). The relation of cortisol at 1 with NT-pro-BNP at 1 and 3 was demonstrated using logistic function in all the participants together (for 1/cortisol at 1 B = 63.40, 58.52; r = 0.41, 0.34; p = 0.003, 0.013, respectively). ΔNT-pro-BNP2/1 linearly correlated with ΔACTH4/3 in WP and W (r = −0.45, −0.48; p = 0.04, 0.04, respectively). These results demonstrate for the first time that HPA axis and NT-pro-BNP interface in physical stress probably contribute to integrative regulation of cardiopulmonary performance.     

Gender discrimination in undernutrition with mediating factors among Bengalee school children from Eastern India

This study was undertaken to determine age and sex variations in the prevalence of underweight and stunting, and to assess the impact of some socio-economic variables on undernutrition among 6–16 year old school children of Bengalee ethnicity in Chapra, West Bengal, India. The subjects were selected randomly from various schools and madrassas of the Chapra Block. A total of 725 children (342 boys and 383 girls) aged 6–16 years were measured and data on their socio-economic status were collected. Age and sex combined rates of underweight and stunting were 44.40% and 37.20%, respectively. Weight-for-age Z-score (WAZ) showed significant association with per-capita income (PCI) among boys (F = 5.45) and girls (F = 8.14). Height-for-age Z-score (HAZ) has also shown the association with per-capita income among boys (F = 4.43) and girls (F = 9.69). The WAZ was significantly associated with fathers’ educational status (FOS) (t = ?2.95) and the number of living rooms (NLR) (t = ?2.91) among girls. The HAZ showed significant association with number of siblings (NS) among girls (F = 4.25). Linear regression analyses revealed that NLR (t = 2.04) and NS (t = 1.95) had a significant impact on HAZ among boys. Among girls, PCI (t = 3.38), FOS (t = 2.87) and NLR (t = 2.81) had a significant impact on WAZ and also PCI (t = 3.28) and FOS (t = 2.90) had a significant impact on HAZ. NLR had significant associations with underweight (χ² = 3.59) and stunting (χ² = 4.20) among boys. Among girls, PCI had significant associations with underweight (χ² = 11.15) and stunting (χ² = 11.64). FOS also showed significant associations with underweight (χ² = 8.10) as well as stunting (χ² = 8.28) among girls. NLR showed a significant association with underweight (χ² = 7.75). Logistics regression analyses revealed that FOS (Wald = 8.00) and NLR (Wald = 4.09) were significant predictors of stunting among boys. Among girls, PCI was a significant predictor of underweight (Wald = 10.95) as well as stunting (Wald = 10.45). FOS, NLR and NS were also significant predictors of stunting (Wald = 8.16), underweight (Wald = 7.68) and stunting (Wald = 6.97) respectively. The present study revealed that the nutritional status of the children was unsatisfactory and it is of paramount importance not only to increase the amount of food supplementation given but also to promote gender equality.     

Assessment of spatial distribution and cysts resources of Artemia in late autumn in Dangxiong Co salt lake

Based on the vertically interval sampling in 25 sampling sites in Dangxiong Co salt lake in 2011, a preliminary investigation on population spatial distribution and cysts resources of Artemia in the lake has been conducted. The study achieves four new progresses. First, the average density of Artemia and Artemia cysts in the lake is 4.157 × 10³ ind. m⁻² and 8.069 × 10⁴ ind. m⁻², respectively. Among Artemia, the adults account for 60.31%; Second, different from other salt lakes in horizontal distribution, the Artemia population mainly distributes in the open water, only a little in the shallow water, and there is no distribution in the longshore area in the north part and the estuary region; Third, in vertical distribution, 44.24% of individuals intensively distribute in the upper water layer within 2.0 m, especially 0–0.2 m, where the average density of Artemia and cysts are maximum (129.488 ind. L⁻¹ and 5.728 ind. L⁻¹, respectively). A decrease of distribution density is accompanied by an increase of water depth basically, the percentage of Artemia and cysts decrease to 0.68% and 4.60%, respectively; Fourth, the cysts resources of 14.96 t in the lake are assessed using contour map. 66.35% of them distributed in 0.0–2.0 m water layer and 49.06% concentrate in the 18.21% areas of the central water; Fifth, quantity of cysts suitable for development in the lake is 2.399 ± 0.320 t, with an upper limit of 0.879 t. The study can provide a reference for the sustainable development and exploitation of Artemia in Dangxiong Co salt lake.     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.