Effects of a plume front on the distribution of inorganic and organic matter off the Rhône River

Hydrological and chemical structures off the Rhône River estuary resulting from the introduction of the river flow into the Mediterranean Sea are described. The effect of the fresh-water/sea-water interface on the distribution of inorganic and organic matter off the Rhône river is investigated. Strong vertical gradients of inorganic and dissolved organic matter such as lipids characterized the first few meters in this area (from 83.7 to 0.6 N-NO₃ µgat l^–1, from 6.39 to 0.92 N-NH₄ µgat l^–1 and from 299 to 73 µg l^–1 of total dissolved lipids). At the interface, substantial increases of particulate organic (PON: from 45 µg l^–1 at surface to 118 µg l^–1 at the interface, POC: from 462 to 876 µg l^–1, total particulate lipids: from 33 to 648 µg l^–1) and suspended matter in general (from 18 to 22.2 mg l^–1) were observed. High phytoplanktonic production may account for some of this enrichment, although passive accumulation might also be involved.     

The influence of substratum age on patterns of protozoan assemblages in freshwater Aufwuchs — a case study

The sulfate reduction rate was measured for almost four years in the profundal sediments of Lake Kizaki, a mesotrophic lake in central Japan. The rate was generally highest in the surface layer and decreased with depth. Seasonally, sulfate reduction tended to be high in spring and summer, and then to decrease until the end of stratification (December) in spite of a constant in situ temperature of around 6 °C, although fluctuations were found in every year. The rate also fluctuated greatly according to year. The maximum rate of sulfate reduction was 0.33 mmol m⁻² d⁻¹ in May, 1990, and the minimum was 0.004 mmol m⁻² d⁻¹ in March, 1993. These relatively low rates, compared with those reported for freshwater sediments, seem to be due to low concentrations of sulfate in the sediments (5–23 μmol l⁻¹ in the surface layer). The rate was highly correlated with the concentration of sulfate in the sediments. The addition of sulfate stimulated sulfate reduction in all sediment samples tested, but adding lactate did not. Therefore, sulfate reduction should be limited mainly by the supply of sulfate. Measurements of sulfate reduction rates at different concentrations of added sulfate revealed a low concentration of half-saturation constant as low as 12 μmol l⁻¹.     

The influence of solvent on conformational properties of peptides with Aib residue—a DFT study

The conformational propensities of the Aib residue on the example of two model peptides Ac-Aib-NHMe (1) and Ac-Aib-NMe₂ (2), were studied by B3LYP and M06-2X functionals, in the gas phase and in the polar solvents. To verify the reliability of selected functionals, we also performed MP2 calculations for the tested molecules in vacuum. Polarizable continuum models (PCM and SMD) were used to estimate the solvent effect. Ramachandran maps were calculated to find all energy minima. Noncovalent intramolecular interactions due to hydrogen-bonds and dipole attractions between carbonyl groups are responsible for the relative stabilities of the conformers. In order to verify the theoretical results, the available conformations of similar X-ray structures from the Cambridge Crystallographic Data Center (CCDC) were analyzed. The results of the calculations show that both derivatives with the Aib residue in the gas phase prefer structures stabilized by intramolecular N–H?O hydrogen bonds, i.e., C₅ and C₇ conformations, while polar solvent promotes helical conformation with φ, ψ values equal to +/?60°, +/?40°. In addition, in the case of molecule 2, the helical conformation is the only one available in the polar environment. This result is fully consistent with the X-ray data.

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Graphical abstract Effect of solvent on the Ramachandran maps of the model peptides with Aib residue

     

The effects of short-term pH decrease on the reproductive output of the copepod Acartia bifilosa – a laboratory study

This laboratory study reports some reproductive responses of the copepod Acartia bifilosa to rapid variations in pH. The imposed changes mimic those that copepods could experience due to coastal upwelling, changed mixing conditions or vertical migration. We measured effects of low pH on egg production, hatching and early nauplii development (H₀: no effects on response variables between low and ambient pH). On treatment with low pH, we found positive effects on egg production rate and nauplii development time. The positive response to low pH could be an initial stress response or show that A. bifilosa is tolerant to the experimental pH values. The result suggests that A. bifilosa is adapted to pH changes as it performs daily migrations between the depths with differing pH. It could also be advantageous for population development if eggs hatch at high speed and so reduce the possibility that they will sink into anoxic and low pH waters.     

The influence of vegetation pattern on the productivity,diversity and stability of vegetation: The case of `brousse tigrée' in the Sahel

Sample sites of `brousse tigrée' and related vegetation types are described for Mali and Niger. Species composition and physical structure of the herbaceous layer as well as woody plant population were recorded at all sites together with data on soils and natural resource management. Herbage yield was measured whereas foliage yield and wood mass were calculated using allometry equation calibrated for each species. `Brousse tigrée' is characterized by the regularly alternating bare-soil stripes with dense linear thickets arranged perpendicularly to the slope. There was no clear superiority in total plant production of `brousse tigrée' when compared to neighbouring site with diffuse vegetation. However, the pattern of `brousse tigrée' tended to favour woody plant yield to the detriment of herbage yield. The number of herbaceous species recorded per site (22–26) was slightly above Sahelian vegetation average despite low number of species per 1-m² quadrat (6–9), bare soil excluded. This species richness reflects the diversity in edaphic niches resulting from the redistribution and local concentration of water resources and shade. The high spatial heterogeneity and species richness of the herbaceous layer in `brousse tigrée' did not attenuate the interannual variation in herbage yield despite low yields. Except for the herb layer, little evidence was found of grazing influence on the vegetation structure and yield a few hundred metres away from livestock concentration points. On the other hand, the clearing of thickets for cropping led to severe soil erosion which threaten the resilience of `brousse tigrée'. These observations and the well-defined climatic, soiland topographic situations under which the `brousse tigrée' occurs invalidate the hypothesis of an anthropic origin of that vegetationpattern.     

The effect of phosphorus binding clay (Phoslock®) in mitigating cyanobacterial nuisance: a laboratory study on the effects on water quality variables and plankton

This laboratory study examined the lanthanum modified clay Phoslock^® for its effectiveness to bind soluble reactive phosphorus (SRP), release of nutrients from this modified clay, its influence on water quality variables (pH, oxygen saturation %, conductivity and turbidity), effects on phytoplankton growth (green alga Scenedesmus obliquus, cyanobacteria Microcystis aeruginosa and Anabaena sp.), and, lastly, its effect on the population growth of the rotifer Brachionus calyciflorus. A clear dose–response for SRP binding by the modified clay was observed. A small amount of ammonium is released from Phoslock^®. We found no effect of Phoslock^® on pH or oxygen saturation. Conductivity increased with the increasing concentration of Phoslock^®. An application of Phoslock^® caused a transient increase of turbidity up to 211 NTU. However, due to rapid settlement, turbidity fell below 13 NTU (~1 m Secchi depth), after 6 h. Phoslock^® addition caused a reduction in growth of all phytoplankton species tested that we attribute to the combined effects of light limitation, flocculation with the bentonite and binding of SRP to Phoslock^®. We estimated the EC₅₀ of Phoslock^® on the population growth of rotifer B. calyciflorus to be 0.15 g Phoslock^® l^?1. Overall, the results of our study indicate Phoslock^® seems to be suitable for field applications.     

The influence of varying illumination on steroid 5α-reductase activity and gonadotropin levels in the rat

The influence of varying illumination on rat hypothalamic, pituitary and prostatic steroid 5α-reductase (SR), body and prostatic weights and plasma FSH, LH and PRL levels was studied. Male rats weighing 50–60 g on arrival were divided as follows: controls (C) received 14 hours of daylight and 10 hours of darkness (14:10), constant light (CL) (24:0), and constant dark (CD) (0:24). After one month the animals were weighed, killed and the following tissues removed for analysis: prostate, hypothalamus, pituitary and blood. Prostates were weighed. Plasma concentrations of LH, FSH and PRL were determined by radioimmunoassay. Other tissues were analyzed for SR. CD animals gained less weight and had less heavy prostates/ 100 g body weight than either C or CL animals. Prostatic and hypothalamic SR activities were reduced following CD, while the pituitary enzyme was unaffected. Gonadotropin levels were unchanged in the CD group. Neither body nor prostatic weights were affected in CL treated animals. Prostatic SR activity increased following CL, while hypothalamic and pituitary enzymes remained unchanged. Plasma LH values were reduced in the CL group. FSH and PRL concentrations did not differ from controls. The prostate appeared most responsive to environmental lighting. It is suggested that observed changes in target organ (prostate) growth due to ambient lighting conditions are mediated via changes in SR.     

A preliminary study on the distribution patterns of endemic species of Fulgoromorpha (Hemiptera,?Auchenorrhyncha) in Iran

Iran is known as the most complex and varied country in southwest Asia, in terms of geography, vegetation, climate and consequently biological diversity. The rather high number of recorded endemic species of Fulgoromorpha in Iran indicates a high potential for speciation in some areas.In this study, in order to identify the endemic zones for Fulgoromorpha of Iran, three main biogeographic regions of the country were divided into 13 primary zones, mainly according to the distribution of published and unpublished locality records of endemic species. Using Venn diagrams and cluster analyses on the primary zones, 6 final endemic zones were recognized: Caspian zone, southern slopes of Alborz, Zagros Mountains, Kerman Mountains, Khorasan Mountains, and Baluchestan and Persian Gulf coasts. Then a similarity map was produced for endemic zones using a Multidimensional analysis (Alscal) and the differences between the positions of the same zones in the similarity and geographic maps were discussed.     

Some mathematical aspects of chemotherapy—II: The distribution of a drug in the body

In a previous paper (Bellman, Jacquez, and Kalaba,Bull. Math. Biophysics,22: 181–198, 1960) a model of the processes occurring in the exchange of a drug between capillary plasma, extracellular space and intracellular space was developed. This included the possibility of a reaction between the drug and a component of the intracellular space. The equations developed thus describe the events within a capillary bed. In the present paper, a simplified model of the body is set up. Each organ is treated as a single capillary bed and is linked to other organs via the circulation, in the parallel and/or series arrangements found in the body. Mixing in the circulation is included at the simplest possible level. The concentration of drug entering any one capillary bed is determined by the concentrations leaving all other capillary beds, the time lags, and mixing involved in the circulation. The equations describing these processes in conjunction with the equations of the processes occurring within each capillary bed lead to a large set of differential-difference equations.     

Description of the female and new data on the distribution of Annitella apfelbecki Klapálek, 1899 (Insecta: Trichoptera)

Annitella apfelbecki is one of three Annitella species with distribution ranges restricted to the Balkan Peninsula. In this paper, we describe the hitherto unknown female of A. apfelbecki and give the most important morphological features to enable its identification and separation from the other Annitella females. Additionally, we provide new data on distribution and discuss zoogeography, life cycle and ecology of this species.     

Seasonal and sexual variation in diel activity rhythms of pine martenMartes martes in the Białowieża National Park (Poland)

From 1991–1996, the activity rhythms of 14 radio-collared pine martensMartes martes (Linnaeus, 1758) (6 males and 8 females) were studied in the pristine deciduous and mixed forests of the Białowieża National Park. Tracking data (5823 h) indicated that the activity rhythms of pine martens varied between sexes and seasons. In spring, male activity peaked at 20.00–00.00 h, whereas in summer and autumn-winter, activity was bimodal, peaking at 18.00–22.00 h and 02.00–04.00 h. Female activity in spring was more evenly distributed than that of males, but in summer their activity peaked at 20.00–00.00 h, while in autumn-winter females had a bimodal rhythm with peaks at 18.00–20.00 h and 02.00–06.00 h. In breeding females, activity rhythms changed in the course of pregnancy and nursing. On average, martens started their activity 73±209 (SD) min before sunset and finished 87±245 min after sunrise. Females became active earlier than males but both sexes terminated activity at the same time. For both males and females the daily activity rhythm was not related to the diurnal course of temperature.     

Vertical distribution and abundance of gymnamoebae (Rhizopoda) in bottom sediments of the brackish water Nivå Bay (Baltic Sea,The Sound)

The sandy sediments of Niv? Bay (Baltic Sea, The Sound, Denmark) are often covered with the mats of sulphur bacteria and are temporarily anoxic. The vertical distribution and abundance of naked amoebae species in three sediment cores from this bay were studied. Amoebae were most abundant and diverse in the upper 1 cm of sediment, and their number and diversity decreased with increasing depth into the sediment. Amoebae were recovered from both upper oxygenated and deep anoxic layers of sediments. The species composition and abundance of amoebae was very heterogeneous, even at spatial scales of several centimeters, suggesting the existence of microhabitats selectively occupied by particular species. All species found were recorded from aerobic cultures and some of these amoebae occur in both the aerobic and anaerobic layers of the sediment. Minimal possible number of amoebae in the sediments, estimated for the first time as areal abundance integrated for depth was: core 1 -597 cm(-2); core 2 -1,110 cm(-2); core 3 -1,430 cm(-2). These abundances are probably best regarded as "potential" abundances of amoebae hidden in the sediments, as the question of the ratio between active and resting amoebae remains open.     

The palaeoenvironments of coastal lagoons in the southern Baltic Sea,II. δ13C and δ15N ratios of organic matter — sources and sediments

Organic carbon and nitrogen isotope values (δ¹³C, δ¹⁵N) and C/N ratios of six sediment cores from six coastal lagoons (including the Oder Estuary) were measured to chart the coastal development and to reconstruct the local palaeoenvironments of the southern Baltic Sea region during the Holocene. In addition, δ¹³C, δ¹⁵N and C/N values of major organic matter sources in the coastal lagoons and their drainage areas are investigated to determine the origin of organic matter (i.e. terrigenous or marine) in the sediments: plankton, aquatic macrophytes, typical C3 shore plants and peat. The δ¹³C, δ¹⁵N and C/N values of the samples collected show the clearly identifiable stages in the development of the water bodies: post-glacial lake stages with sandy sedimentation, lacustrine phases with high autochthonous productivity, terrestrial stages with peat formation, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands. These stages are the results of sea level changes in the region. The values allow derivation of differences in the palaeoenvironments of the lagoons in the study area. A distinct terrestrial input is evident in the sediments of the lagoonal Oder Estuary, which can be attributed to the direct inflow of the Oder River into the lagoon. The isotope and C/N values also suggest a contribution of C4 plant detritus for the water bodies in the northeastern part of the study area (Barther Bodden, Grabow). The burial of autochthonous organic matter (i.e. plankton, aquatic macrophytes) in the sediment could be derived for all lagoons in this investigation.     

The feeding biology of the triclad Phagocata vitta (Dugès): A laboratory study

A series of laboratory experiments investigated the diet and feeding behaviour of Phagocata vitta (Dugès). Its fundamental food niche comprises oligochaetes and chironomid larvae, in order of importance. Other arthropod groups, when wounded, are also eaten.Increasing prey density resulted in the ingestion rate increasing in a type 2 functional response curve, sensu Holling. Group feeding by triclads did not widen the food niche but did result in small triclads being more successful in obtaining a meal.When a range of size classes of prey were offered to various size classes of triclad, small triclads were found to take mainly small prey, whilst other sizes would take prey sizes in proportion to their presence in the mixture.Mucous traps do not appear to have an important role in the feeding biology of the triclad.     

Soft and persistent—The influence of sand-flooring and calves on the resting behavior of a zoo-kept African elephant (Loxodonta africana) group

Caring for all aspects of zoo elephants’ well-being is considered a major challenge. Providing an appropriate flooring substrate to facilitate lying rest presents a meaningful part of a holistic management concept. Investigating the impact of a new sand flooring on the nocturnal resting behavior of a breeding group of seven African elephants living at one zoo revealed more total lying rest, longer bouts of lying rest and a reduced side preference in the adult females. With an average total daily lying rest of about 1.5–2.0 hrs, the investigated zoo elephants expressed longer lying rest compared to recently reported data from free-ranging individuals in Botswana. In addition, the presence of nursing calves in the observed elephant group seemed to impact the resting pattern of all group members, with around 60% of all lying bouts being discontinued after interruption by the youngsters. With respect to observed nursing during leaning rest, we encourage the installation of appropriate horizontal structures in breeding facilities to support leaning rest behavior of their female elephants. In doing so, zoos may improve rest quality of nursing females, and, in general, the welfare aspect of sleep for their elephants.     

The influence of thick floating vegetation (Water hyacinth: Eichhornia crassipes) on the physico — chemical environment of a fresh water wetland

Measurements made in fresh water wetland have shown that temperature, pH, dissolved oxygen and bicarbonate alkalinity in the hyacinth infested area were lower, but dissolved free carbon dioxide concentration was excitingly greater than in the open water area. This extreme hypoxic and hypercarbic condition of hyacinth covered areas was caused by the thick coverage of Eichhornia crassipes which was crucial for the composition of the characteristic flora and fauna.     

The spatial distribution pattern of the brown planthopperNilaparvata lugens Stål (Homoptera: Delphacidae) in west Java,Indonesia

Spatial distribution pattern of the brown planthopper (BPH) was analyzed at 9 experimental fields in the northern part of West Java during two consecutive rice cropping seasons, i.e., wet and dry seasons. The population of each developmental stage and wing form of BPH at each location showed consistent departure from the random (Poisson) distribution, the variances of the densities in most cases exceeding their means. Namely, the distribution pattern of BPH per hill of rice plant was found to have a general tendency to be aggregated or contagious and to fit fairly well to the negative binomial model. The tendency for aggregation was further confirmed by both the β-values of -m regression being larger than unity and the C_A-values being larger than zero for each developmental stage. Although significant variations in the distribution pattern as measured by β- or C_A-value were observed between different developmental stages, between wing forms and among locations, the degree of aggregation for a given developmental stage at each experimental field remained fairly stable throughout the crop period, despite wide temporal changes in population density. Possible factors to explain these characteristics of the spatial distribution pattern of the BPH in West Java were discussed with reference to the process generating it.