Influence of natural amphipod (<Emphasis Type="Italic">Victoriopisa</Emphasis><Emphasis Type="Italic">australiensis</Emphasis>) (Chilton, 1923) population densities on benthic metabolism,nutrient fluxes,denitrification and DNRA in sub-tropical estuarine sediment

The influence of natural populations of the sub-surface deposit-feeding amphipod Victoriopisa australiensis on sediment biogeochemistry was assessed by randomly collecting 21 sediment cores in a zone of Coombabah Lake, southern Moreton Bay, Australia, where the benthic infauna was dominated by this species. Cores were incubated sequentially to determine sediment–water column fluxes of oxygen, dissolved inorganic carbon and inorganic N species, followed by incubations to determine rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) using the isotope pairing technique. Finally, each core was sieved in order to determine the population and biomass of amphipods present. Whilst all measures of overall benthic metabolism (sediment oxygen demand, and effluxes of inorganic carbon and nitrogen) showed increased with amphipod density, with rates being stimulated 70–220% at the highest categorised density range of 2,500–3,500 ind m⁻², only the correlation with dissolved inorganic carbon was statistically significant. In contrast, there were no discernable trends between amphipod densities and any of the N-cycle processes with the slopes of all correlations being very close to zero. These results highlight the differences in mesocosm simulations of fauna effects, which primarily relate to shifts in rates of organic matter turnover, compared to natural sediments where fauna effects relate more to induced changes in rates of organic matter deposition. Therefore, while mesocosms represent a powerful tool to investigate the mechanisms by which fauna influences microbial metabolism in the sediment, only studies of natural sediments can determine to what extent these mechanisms function in situ. Handling editor: Pierluigi Viaroli     

<Emphasis Type="Italic">Spartina maritima</Emphasis> influence on the dynamics of the phosphorus sedimentary cycle in a warm temperate estuary (Mondego estuary,Portugal)

During the last decades the Mondego estuary has been under severe ecological stress mainly caused by eutrophication. In this salt march system, Spartina maritima covers about 10.5 ha of the intertidal areas. The objective of the present study was to evaluate the effect of Spartina maritima marshes on the dynamics of phosphorus (P) binding in the surface sediment. We compare phosphate and oxygen fluxes, P-adsorption capacity, phosphate concentrations and total amount, and the extractable P forms in the upper 20 cm of sediment in vegetated sediment with adjacent mudflats without vegetation. Sediment pore-water profiles followed a clear trend, with lower P concentrations in more superficial layers, and increasing with depth. The vegetated mudflats presented lower concentrations of dissolved inorganic phosphorus than adjacent bare bottom mudflats, lower phosphate total amount, as well as higher P-adsorption capacity. Results from the extraction procedure show that the superficial layers are the most important for estuarine phosphorus dynamics, since maximum concentrations of labile P pools are present here. In contrast, higher proportions of refractory P pool are found in deeper layers. Spartina marsh sediments had less total P, less iron bound P, and less exchangeable P than adjacent bare bottom mudflats. Also the pool of loosely sorbed P is lower in the Spartina marsh. Phosphate regeneration from the sediment to the overlying water was only 11.8 kg ha⁻¹ year⁻¹ in vegetated sediment while 25.8 kg ha⁻¹ year⁻¹ in the bare mud flat. Plant uptake for growth combined with an enhanced P-adsorption capacity of the sediment, may explain these differences. Therefore, Spartina marshes are very important agents in the sedimentary P cycle worldwide, and can be considered a useful management tool in estuarine ecosystem recovery efforts.     

Tidal effects on the organic carbon mineralization rate under aerobic conditions in sediments of an intertidal estuary

Laboratory experiments and field measurements were conducted to examine the effect of tide on the organic carbon mineralization rate in sediments under aerobic conditions of an intertidal estuary. Core samples of surface sediments were collected from an intertidal estuary of the Kurose River, Hiroshima, Japan. To mimic low and high tide in the intertidal estuary, organic carbon mineralization rates in the samples were measured in the laboratory under both air-exposed and submerged conditions. Mineralization rates under air-exposed conditions were two to five times higher than those under submerged conditions. Field measurements of the rate of CO₂ emission from the sediment surface revealed a rapid increase in the rate as the sea level fell during ebb tide. The estimated amount of daily organic carbon mineralization assuming a constantly submerged condition was 30% less than that estimated when considering the semi-diurnal fluctuation in sea level. These results indicate that tide has a marked impact on the organic carbon mineralization rate in sediments under aerobic conditions on an intertidal estuary, and tidal effects need to be considered when the amount of mineralized organic carbon is estimated.     

Effects of Exogenous Electromagnetic Fields on a Simplified Ion Channel Model

In this paper, we calculate the effect of an exogenous perturbation (an electromagnetic field [EMF] oscillating in the range of microwave frequencies in the range of 1 GHz) on the flux of two ion species through a cylindrical ion channel, implementing a continuous model, the Poisson–Smoluchowski system of equations, to study the dynamics of charged particle density inside the channel. The method was validated through comparison with Brownian dynamics simulations, supposed to be more accurate but computationally more demanding, obtaining a very good agreement. No EMF effects were observed for low field intensities below the level for thermal effects, as the highly viscous regime and the simplicity of the channel do not exhibit resonance phenomena. For high intensities of the external field (>10⁵ V/m), we observed slightly different behavior of ion concentration oscillations and ion currents as a function of EMF orientation with respect to the channel axis.     

New species in the genus <Emphasis Type="Italic">Francisella</Emphasis> (Gammaproteobacteria; Francisellaceae); <Emphasis Type="Italic">Francisella piscicida</Emphasis> sp. nov. isolated from cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>)

A Francisella strain, GM2212, previously isolated from moribund farmed Atlantic cod (Gadus morhua) in Norway, is closely related to Francisella philomiragia among Francisella spp. according to its complete 16S rDNA, 16S-23S intergenic spacer, 23S rDNA, 23S–5S intergenic spacer, 5S rDNA, FopA, lipoprotein TUL4 (LpnA), malate dehydrogenase and hypothetical lipoprotein (LpnB) sequences. A comparison between GM2212 and the type strain of Francisella philomiragia were performed by DNA–DNA hybridization and fatty acid analysis. The DNA–DNA hybridization showed a 70% similarity. The fatty acid analysis showed only minor differences between the Francisella isolates. Due to the inconclusive result from the DNA–DNA hybridisation, major emphasis concerning the status of this isolate is made on previously published molecular, phenotypic and biochemical characters. All characteristics taken together support the establishment of GM2212 as a novel species, for which the name Francisella piscicida sp. nov. is proposed (=CNCM I-3511^T = DSM 18777^T = LMG registration number not yet available).     

Bioconversion of lovastatin to a novel statin by Amycolatopsis sp.

3-Hydroxy-3-methylglutaryl–coenzyme A (HMG–CoA) reductase catalyzes the conversion of HMG–CoA to mevalonic acid, which plays a significant role in cholesterol synthesis. Several statins, inhibitors of HMG–CoA reductase, can be synthesized and converted by microorganisms. Among 700 strains obtained from culture collections, one strain could convert lovastatin to a novel statin, wuxistatin. The strain was identified as a member of the genus Amycolatopsis based on 16S rRNA gene sequence, morphology analysis, and chemotaxonomic properties. Wuxistatin, a novel HMG–CoA reductase inhibitor, was purified by chromatography, and the structure was determined by electrospray ionization mass and nuclear magnetic resonance spectroscopy. The results show that wuxistatin was butanoic acid, 2-methyl-,1,2,3,5,8,8a-hexahydro-5-hydroxy-7-methyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl) ethy]-1-naphthalenyl ester. An additional hydroxyl group was added to lovastatin at the 5-position to yield wuxistatin. This modification enhanced the intrinsic inhibitory activity (IC50) of wuxistatin (41 ± 5 nM) for fourfold compared with lovastatin (160 ± 10 nM). A stoichiometric conversion of lovastatin to wuxistatin occurred.     

Four new species of the genusSporobolomyces isolated from leaves in Thailand

Thirteen undescribed strains of ballistoconidium-forming yeasts, isolated from leaves collected in the suburbs and along the southeast seacoast of Bangkok, Thailand, were divided into four different groups in the genusSporobolomyces on the basis of morphological, physiological, biochemical, and chemotaxonomical characteristics, and analyses of the sequences of 18S rDNA and internal transcribed spacer regions. DNA-DNA reassociation experiments with related species revealed that these four groups were four new distinct species.Sporobolomyces nylandii sp. nov.,S. poonsookiae sp. nov.,S. blumeae sp. nov. andS. vermiculatus sp. nov. are proposed for these strains.     

Decomposition of four macrophytes in wetland sediments: Organic matter and nutrient decay and associated benthic processes

Decomposition rates of Phragmites australis, Carex riparia, Nuphar luteum and Salvinia natans and benthic processes were measured from December 2003 to December 2004 in a shallow wetland (Paludi di Ostiglia, Northern Italy) by means of litter bags and intact cores incubations. Decay rate was highest for N. luteum (k = 0.0152 d⁻¹), intermediate for S. natans (k = 0.0041 d⁻¹) and similar for P. australis (k = 0.0027 d⁻¹) and C. riparia (k = 0.0028 d⁻¹).Benthic metabolism followed a seasonal pattern with summer peaks of O₂ demand and TCO₂, CH₄ and NH₄⁺ efflux whilst soluble reactive phosphorus (SRP) fluxes were negligible also under hypoxic conditions, indicating that P was mainly retained by sediment. The initial C:P ratio was similar in N. luteum and S. natans (170) and significantly lower than that of P. australis and C. riparia (360). During the detritus decay P was progressively lost by N. luteum and S. natans tissues, whereas, after an initial leaching, it was probably re-used during the microbial decomposition of the more refractory P. australis and C. riparia detritus. Nuphar luteum, P. australis and S. natans had comparable initial C:N mass ratio (15), significantly lower than that of C. riparia (26). The C:N ratio was rather constant for N. luteum (12.9 ± 1.5) and S. natans (14.6 ± 0.9), decreased slightly to below 20 for C. riparia and increased up to 30 for P. australis. Overall, differences among species were likely due to the recalcitrance of decomposing detritus, whilst process rates were controlled by limitation of microbial processes by nutrients and electron acceptor availability.     

The impact of the 2003 summer heat wave and the 2005 late cold wave on the phytoplankton in the north-eastern English Channel

The phytoplankton composition was investigated at two fixed stations in the north-eastern English Channel from November 1997 to December 2005. The warmest temperatures in European historical records were recorded in August 2003. This event was associated with an exceptional abundance peak of the dinoflagellates Akashiwo sanguinea (9600 cells L(-1)) and Ceratium fusus. The lowest February temperatures for the 1998-2005 period were recorded in 2005, coinciding with the absence, for the first time in recent decades, of the spring bloom of Phaeocystis globosa. The 'de-eutrophication', mainly the reduction of river nutrient loads, is progressively reducing the magnitude of the Phaeocystis blooms. Exceptionally in 2005, the colder temperatures increased water column mixing, favouring the dominance of tychoplanktonic diatoms until early March (pre-bloom period). The delay in spring stratification, lower light availability due to turbidity (resuspended sediment) and organic matter, and competition with tychoplanktonic diatoms contributed to retard the timing of the spring phytoplankton bloom and disadvantage the development of Phaeocystis. The summer 2003 European heat wave is expected to have had little influence on total annual primary production, because it occurred at mid-summer, the period of lowest annual phytoplankton abundance. However, the anomalous weather in the second half of winter 2005 did affect the annual primary production.     

Organic matter distribution and fluxes within a holm oak (Quercus ilex L.) stand in the Etna volcano

Located at 1100 m above sea level, on the western site of the Etna volcano, the ecophysiology of the Mount Minardo holm oak coppice has been investigated for more then twenty years. In this stand, now 31 years old, the above ground biomass amounts to 15000 g m^-2 of organic material, including leaves and perennial woody material. During these 31 years, the mean annual production has been around 775 g m^-2. The yearly mean litterfall amounts to 310 g m^-2, including 200 g m^-2 of leaves, mostly two years old. The soil surface is covered by a litter layer amounting to 3150 g m^-2. Each year, following Jenny's decomposition rate and field measurements, 290 g m^-2 of the litter turns into CO₂, or becomes incorporated in the soil organic matter.     

The benthic macro-algae of Georgian Bay,the North Channel and their drainage basin

Thirty-nine subgeneric taxa of macroalgae have been collected from 83 sites in Georgian Bay, the North Channel and their drainage basin. There were 15 species in the Bay and Channel and 32 species in streams, rivers and impoundments in the basin. Only 8 of the Bay and Channel species were also found in the watershed. Cladophora glomerata was the most important species in Georgian Bay and the North Channel, having an estimated 640 × 10³ m² cover and 19 × 10⁴ kg fresh weight standing crop. However, this species was largely concentrated on the southwestern shorelines of these water bodies. Its distribution along the northeastern shoreline appears to be limited by total ion and phosphorus levels. Chara globularis/vulgaris was the subdominant taxon in Georgian Bay and the North Channel with an estimated 70 × 10³ m² cover and 15 × 10³ kg fresh weight biomass. This species was more widely distributed than C. glomerata. No other taxon contributed significantly to the standing crop including the frequently occurring Ulothrix zonata, Zygnema spp. and Spirogyra spp. The maximum benthic macroalgal biomass was estimated to be approximately 10% of the phytoplankton biomass.     

杉木和米槠凋落叶DOM对土壤碳矿化的影响

DOM(Dissolved organic matter)是土壤微生物呼吸的重要底物,凋落物淋溶的DOM对土壤碳矿化具有重要影响。选择中亚热带地区具有代表性的杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)凋落叶作为研究对象,通过两个月的短期室内培养,把不同凋落叶浸提出的DOM添加到培养瓶中,定期测定土壤碳矿化速率,计算土壤碳累积矿化量,探讨两种等浓度等量DOM添加对土壤碳矿化的影响,并分析DOM化学性质在土壤碳矿化过程中的重要性。结果表明:米槠凋落叶浸提得到的DOC(Dissolved organic carbon)和DON(Dissolved organic nitrogen)浓度均显著高于杉木凋落叶的(P0.05),而杉木凋落叶浸提得到的DOM的UV吸收值(SUVA_(254))和HIX(Humification index)均显著低于米槠凋落叶的(P0.01)。添加等浓度等量杉木和米槠凋落叶DOM到土壤中均显著增加了土壤碳矿化速率,在第1天内分别比对照高198%和168%,3d后下降到61.8%和44.1%,14d后基本处于平稳状态,表明外源有机物添加对土壤碳矿化的前期影响较大。培养过程中,添加杉木和米槠凋落叶DOM的土壤碳矿化累积量均能采用双因素指数模型进行拟合(r~2=0.99),但添加两者凋落叶DOM后土壤碳矿化累积量没有显著差异。     

Two new species of the family Dicranophoridae (Rotifera, Ploima) from the littoral psammon, with notes on other brackish water rotifers in Denmark

The rotifer fauna has been investigated at three littoral brackish water localities in the Öresund, Denmark. Samples taken from plankton, periphyton and psammon yielded 14 rotifer species. Two of these are new to science and are described herein. Both species were found in psammon at the same locality. Erignatha longidentata n. sp. is characterised by having toes with swollen bases, convex outer margins and concave inner margins. The trophi have a pair of large subunci and relatively large unci. The other new species, Paradicranophorus wesenberglundi n. sp., is characterised by having two large red pigmented eyespots and large conical toes. The rami are lyrate, and intramallei and supramanubria are present in the mallei.     

In vitro evaluation of Trichoderma and Gliocladium antagonism against the symbiotic fungus of the leaf-cutting ant Atta cephalotes

The antagonistic activity of Trichoderma and Gliocladium isolates against Attamyces sp., a symbiotic fungus of the leaf-cutting ant Atta cephalotes, was investigated. A. cephalotes cultures this fungus as the primary food source. Most of the Trichodema and Gliocladium isolates tested in vitro (82.6%) inhibited the Attamyces sp. mycelial growth, which was probably due to their colonization ability and competition for nutrients, both of them known mechanisms of some species of these genera. T. lignorum strain T-26 was the strongest inhibitor achieving a colonization of 23%. Microscopical observations indicate that the inhibitory effect was caused by an interaction that took place in close contact with the host hypha, causing wall deformation that led to the collapse of the turgor pressure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simultaneous mineralization of glyphosate and diuron by a consortium of three bacteria as free- and/or immobilized-cells formulations

A bacterial consortium able to mineralize two herbicides, glyphosate (Pseudomonas 4ASW) and diuron (Arthrobacter sp. N4 and Delftia acidovorans), was cultivated in both a synthetic culture medium without phosphate and a sediment extract medium. In the aim at optimizing glyphosate and diuron mineralization, all the combinations, i.e., free and/or immobilized cells in Ca-alginate beads were tested. With the synthetic medium, the simultaneous mineralization of glyphosate and diuron required at least the immobilization of Pseudomonas 4ASW. Conversely, with the sediment extract medium, only the mineralization of diuron was observed, most probably, because of both nutrient deficiency and phosphate in the sediment extract medium.     

Diversity of benthic macrofauna in the eastern English Channel: comparison among and within communities

The diversity of benthic macrofaunal assemblages in the eastern English Channel is described from 707 samples collected with a Rallier-du-Baty dredge during 1971–1975. Four assemblages were primarily defined by means of multivariate data analyses and clustering methods: the Abra alba community, the Ophelia borealis community, the pebbles community and a mixed assemblage of the first three communities. Spatial heterogeneity of these communities is significantly correlated with sedimentary characteristics, although local variability appears to be controlled by both physical and biological processes. Ecological diversity of these communities was analysed considering species richness (S), the Shannon diversity index (H), and rank-frequency diagrammes (RFD). These analyses were performed at two spatial scales: for a single sample, and for a 'site of 10 pooled samples. Thus, several sites were chosen in order to compare diversity patterns and species quantitative structure among and within the communities. The greatest species richness was recorded for the pebbles (57–69) and the A. alba (63–79) communities. In the former, high values may be due to the complexity of microhabitats and the large flux of food related to strong currents. In the latter, both organic matter and terrestrial inputs associated with the mud favour the presence of deposit-feeder organisms. No clear trend was observed among and within the community sites in terms of the species quantitative structure. Thus, convex RFD shapes were observed in three assemblages: the mixed assemblage (offshore site), the A. alba (North Sea), and the pebbles (Normandy coast). Sigmoid shapes were observed in the pebbles (Dover Strait) and A. alba (English coast) communities. Presumably, these shapes can be caused by the combined action of physical (strong currents, substrate stability, mud content in the sediments) and biological factors (co-occurrence of species from different communities, strong species recruitment, relative dominance of carnivorous species).     

Changes in fish assemblage structure with variability of flow in two different channel types

Despite the fact that flow and channel morphology are two critical factors that need to be taken into account when considering the conservation or restoration of river environments, there are no reports on the response of fish assemblages to changes involving both variables in combination. This study examined the response of fish assemblages to artificially induced changes in flow discharge in an experimental stream that had simple (a glide reach) and complex (pool–riffle reach) morphologies. When the flow of the glide reach was increased, the fish assemblage structure changed from one dominated by the demersal species Misgurnus anguillicaudatus and Cobitis sp. to one dominated by the water-column species Zacco platypus and Gnathopogon elongatus. In the pool–riffle reach, the fish assemblage structure changed from one dominated by Cobitis sp. and Z. platypus to one dominated by Plecoglossus altivelis altivelis. When the flow discharge was low, the fish assemblages of both reach types resembled each other in being dominated largely by demersal species, but when flow was increased these similarities faded and distinct assemblages emerged. In the glide reach, increasing the flow volume caused a linear increase in both water depth and velocity and a gradual increase in the diversity of water-column species, their relative abundance, and size. The number of Z. platypus increased fivefold whereas the number of M. anguillicaudatus decreased to less than a quarter of their original number. In the pool–riffle reach, the number of P. altivelis altivelis grew conspicuously although increased flow produced no clear increase in depth or velocity. Calculation of the availability of physical habitat environments suitable for Z. platypus and P. altivelis altivelis in each reach type indicated that preferable habitat for both species was more available in the glide reach. The lower abundance of P. altivelis altivelis in the glide reach was attributed to the relatively low availability of algal food resource due to the sand-predominated substrate whereas pebbles predominated in the pool–riffle reach providing good conditions for algal growth. Our findings suggest the need for a framework for considering environmental flow that takes into account variables such as channel morphology and food resource conditions.     

Introducing inter-individual growth variability in the assessment of a cephalopod population: application to the English Channel squid Loligo forbesi

A new approach is presented here to better take into account inter-individual growth variability in age-structured models used for stock assessment. Cohort analysis requires knowledge of the age structure of the catch, generally derived from an age–length key and length-structure information. Age distribution at length is estimated by applying conditional quantile regression to a data set of lengths and ages estimated from calcareous parts. A “stochastic” age–length key that describes the probability of age-at-length is applied to the English Channel squid Loligo forbesi. Age distribution at length from quantile regression proved to be considerably less biased than that resulting from both polymodal decomposition (PD) and two separate slicing methods. Both catch-at-age and stock size were underestimated using classical methods. Estimations of fishing mortalities from classical methods were higher causing underestimation in yield simulations. Quantile regression offers a more complete statistical analysis of the stochastic relationships among random variables than mean regression and PD.     

Expression of a neuropeptide similar to allatotropin in free living turbellaria (platyhelminthes)

Mechanisms coordinating cell–cell interaction have appeared early in evolution. Allatotropin (AT), a neuropeptide isolated based on its ability to stimulate the synthesis of juvenile hormones (JHs) in insects has also been found in other invertebrate phyla. Despite this function, AT has proved to be myotropic. In the present study we analyze its expression in two groups of Turbellaria (Catenulida, Macrostomida), and its probable relationship with muscle tissue. The results show the presence of an AT-like peptide in the free living turbellaria analyzed. The analysis of the expression of the peptide together with phalloidin, suggests a functional relationship between the peptide and muscle tissue, showing that it could be acting as a myoregulator. The finding of immunoreactive fibers associated with sensory organs like ciliated pits in Catenulida and eyes in Macrostomida makes probable that AT could play a role in the physiological mechanisms controlling circadian activities. Furthermore, the existence of AT in several phyla of Protostomata suggests that this peptide could be a synapomorphic feature of this group. Indeed, the presence in organisms that do not undergo metamorphosis, could be signaling that it was first involved in myotropic activities, being the stimulation of the synthesis of JHs a secondary function acquired by the phylum Arthropoda.     

Construction of a Tn5 derivative encoding bioluminescence and its introduction in Pseudomonas, Agrobacterium and Rhizobium

Summary A simple method based upon the use of a Tn5 derivative, Tn5-Lux, has been devised for the introduction and stable expression of the character of bioluminescence in a variety of gram-negative bacteria. In Tn5-Lux, the luxAB genes of Vibrio harveyi encoding luciferase are inserted on a SalI-BglII fragment between the kanamycin resistance (Km^r) gene and the right insertion sequence. The transposon derivative was placed on a transposition suicide vehicle by in situ recombination with the Tn5 suicide vector pGS9, to yield pDB30. Mating between Escherichia coli WA803 (pDB30) and a strain from our laboratory, Pseudomonas sp. RB100C, gave a Km^r transfer frequency of 10^-6 per recipient, a value 10 times lower than that obtained with the original suicide vehicle pGS9. Tn5-Lux was also introduced by insertion mutagenesis in other strains of gram-negative soil bacteria. The bioluminescence marker was expressed in the presence of n-decanal, and was monitored as chemiluminescence in a liquid scintillation counter. The recorded light intensities were fairly comparable among the strains, and ranged between 0.2 to 1.8x10⁶ cpm for a cell density of 10³ colony forming units/ml. Nodules initiated by bioluminescent strains of Rhizobium leguminosarum on two different hosts were compared for intensity of the bioluminescence they produced.