Anaerobic submerged membrane bioreactor (AnSMBR) treating low-strength wastewater under psychrophilic temperature conditions

An anaerobic submerged membrane bioreactor (AnSMBR) treating low-strength wastewater was operated for 90 days under psychrophilic temperature conditions (20 °C). Besides biogas sparging, additional shear was created by circulating sludge to control membrane fouling. The critical flux concept was used to evaluate the effectiveness of this configuration. Biogas sparging with a gas velocity (U_G) of 62 m/h together with sludge circulation (94 m/h) led to a critical flux of 7 L/(m² h). Nevertheless, a further increase in the U_G only minimally enhanced the critical flux. A low fouling rate was observed under critical flux conditions. The cake layer represented the main fouling resistance after 85 days of operation. Distinctly different volatile fatty acid (VFA) concentrations in the reactor and in the permeate were always observed. This fact suggests that a biologically active part of the cake layer contributes to degrade a part of the daily organic load. Hence, chemical oxygen demand (COD) removal efficiencies of up to 94% were observed. Nevertheless, the biogas balance indicates that even considering the dissolved methane, the methane yield were always lower than the theoretical value, which indicates that the organic compounds were not completely degraded but physically retained by the membrane in the reactor.     

Microbial behaviors involved in cake fouling in membrane bioreactors under different solids retention times

Biomass characteristics and membrane performances in the MBRs operated at a high flux of 30 L/m² h under different SRTs (10, 30 days, and infinity) were monitored. Results showed that more serious cake-fouling happened in the SRT-infinity MBR, which correlated with the activated sludge characteristics such as smaller floc size and greater EPS amount. DGGE analysis indicated that the microbial community shifted in different ways under various SRTs, which also influenced EPS productions in the MBRs. Different microbial communities were developed on the membrane surfaces at various operating stages and SRTs. Possibly, the activated sludge characteristics (such as MLSS concentration, EPS properties) and hydrodynamic conditions influenced by the SRTs were associated with cake layer development and membrane fouling propensity. Insight into the EPS characteristics and deposition behaviors of bacterial flocs will be crucial to explore appropriate biofouling control strategies in MBRs.     

Correlation between fouling propensity of soluble extracellular polymeric substances and sludge metabolic activity altered by different starvation conditions

Soluble extracellular polymeric substances (EPSs) cause membrane fouling in membrane bioreactors (MBRs), correlated with MBR sludge characteristics. Effects of F/M ratios on the evolution of soluble EPSs, fouling propensity of supernatants, and sludge metabolic activity were measured in this study in a two-period sequencing batch reactor (SBR). The experimental results show that fouling propensity was directly correlated with soluble-EPS concentration and composition. Sludge that had entirely lost active cells by long-term starvation released 64.4 ± 0.9 mg/L of humic acids, which caused a rapid increase in membrane resistance (40.67 ± 2.24 × 10¹¹ m⁻¹) during fouling tests. During short-term starvation, induced by incubation at a normal to low F/M ratio of 0.05 d⁻¹, sludge can use previously secreted utilization-associated products (UAPs) to maintain endogenous respiration. Therefore, the strategies of accumulating sludge and prolonging sludge retention time in MBRs may create long-term starvation and promote membrane fouling.     

A mechanistic study of in situ chemical cleaning-in-place for a PTFE flat sheet membrane: fouling mitigation and membrane characterization

This study aimed at unfolding the role and mechanisms of chemically enhanced cleaning-in-place (CIP) regimes in fouling control of polytetrafluoroethylene (PTFE) made flat sheet (FS) membrane bio-reactors (MBRs). The trans-membrane pressure (TMP) was successfully maintained below 10 kPa using a daily CIP regime consisting of 100 to 600 mg l^?1 of NaOCl and cake layer resistance control was shown to be critical for effective high-flux MBR operation. In contrast, in the control unit without the CIP, the TMP exceeded 35 kPa at a flux of 40 LMH. The extracellular polymeric substances associated with proteins (EPS_protein) were also controlled effectively with a daily application of the CIP to the fouled membrane. Moreover, the CIP prompted a thinner and looser bio-cake layer on the membrane surface, suggesting that in situ CIP can be a favorable method to control FS membrane fouling at high-flux MBR operation.     

Microbial community developments and biomass characteristics in membrane bioreactors under different organic loadings

Microbial community developments and biomass characteristics (concentration, particle size, extracellular polymeric substances (EPS), and membrane fouling propensity) were compared when three MBRs were fed with the synthetic wastewater at different organic loadings. Results showed that the bacterial communities dynamically shifted in different ways and the EPS displayed dissimilar profiles under various organic loadings, which were associated with the ratios of food to microorganism and dissolved oxygen levels in the MBRs. The membrane fouling tendency of biomass in the low-loading MBR (0.57 g COD/L day) was insignificantly different from that in the medium-loading MBR (1.14 g COD/L day), which was apparently lower than that in the high-loading MBR (2.28 g COD/L day). The membrane fouling propensity of biomass was strongly correlated with their bound EPS contents, indicating cake layer fouling (i.e., deposition of microbial flocs) was predominant in membrane fouling at a high flux of 30 L/m² h.     

Effect of aeration and agitation on the protease production by S<Emphasis Type="Italic">taphylococcus aureus</Emphasis> mutant RC128 in a stirred tank bioreactor

The modified rotating simplex method has been successfully used to determine the best combination of agitation rate and aeration rate for maximum production of extracellular proteases by Staphylococcus aureus mutant RC128, in a stirred tank bioreactor operated in a discontinuous way. This mutant has shown altered exoprotein production, specially enhanced protease production. Maximum production of proteases (15.28 UP/ml), measured using azocasein as a substrate, was obtained at exponential growth phase when the bioreactor was operated at 300 rpm and at 2 vvm with a volumetric oxygen transfer coefficient (K _L a) of 175.75 h⁻¹. These conditions were found to be more suitable for protease production.     

Phenol removal from hypersaline wastewaters in a Membrane Biological Reactor (MBR): operation and microbiological characterisation

In this study, two Membrane Biological Reactors (MBR) with submerged flat membranes, one at lab-scale conditions and the other at pilot-plant conditions, were operated at environmental temperature to treat an industrial wastewater characterised by low phenol concentrations (8-16 mg L⁻¹) and high salinity (∼150-160 mS cm⁻¹). During the operation of both reactors, the phenol loading rate was progressively increased and less than 1 mg phenol L⁻¹ was detected even at very low HRTs (0.5-0.7 days). Membrane fouling was minimized by the cross flow aeration rate inside the MBRs and by intermittent permeation. Microbial community analysis of both reactors revealed that members of the genera Halomonas and Marinobacter (gammaproteobacteria) were major components. Growth-linked phenol degradation by pure cultures of Marinobacter isolates demonstrated that this bacterium played a major role in the removal of phenol from the bioreactors.     

Pretreatment with alum or powdered activated carbon reduces bacterial predation-associated irreversible fouling of membranes

This study evaluated the co-application of bacterial predation by Bdellovibrio bacteriovorus and either alum coagulation or powdered activated carbon adsorption to reduce fouling caused by Escherichia coli rich feed solutions in dead-end microfiltration tests. The flux increased when the samples were predated upon or treated with 100 ppm alum or PAC, but co-treatment with alum and predation gave the best flux results. The total membrane resistance caused by the predated sample was reduced six-fold when treated with 100 ppm PAC, from 11.8 to 1.98 × 10¹¹ m^?1, while irreversible fouling (R_p) was 2.7-fold lower. Treatment with 100 ppm alum reduced the total resistance 14.9-fold (11.8 to 0.79 × 10¹¹ m^?1) while the R_p decreased 4.25-fold. SEM imaging confirmed this, with less obvious fouling of the membrane after the combined process. This study illustrates that the combination of bacterial predation and the subsequent removal of debris using coagulation or adsorption mitigates membrane biofouling and improves membrane performance.     

Bending undulations and elasticity of the erythrocyte membrane: effects of cell shape and membrane organization

The undulatory excitations (flickering) of human and camel erythrocytes were evaluated by employing the previously used flicker spectroscopy and by local measurements of the autocorrelation function K (t) of the cell thickness fluctuations using a dynamic image processing technique. By fitting theoretical and experimental flicker spectra relative values of the bending elastic modulus K _c of the membrane and of the cytoplasmic viscosity were obtained. The effects of shape changes were monitored by simultaneous measurement of the average light intensity I ₀ passing the cells and by phase contrast microscopic observation of the cells. Evaluation of the cellular excitations in terms of the quasi-spherical model yielded values of K _c /R _inf0 ^sup3 and · R ₀ (R ₀=equivalent sphere radius) and allowed us to account (1) for volume changes, (2) for effects of surface tension and spontaneous curvature and (3) for the non-exponential decay of K (t). From the long time decay of K (t) we obtained an upper limit of the bending elastic modulus of normal cells of K _c = 2–3 · 10^–19 Nm which is an order of magnitude larger than the value found by reflection interference contrast microscopy (RICT, K _c , = 3.4 · 10^–20 Nm, Zilker et al. 1987) but considerably lower than expected for a bilayer containing 50% cholesterol (K _c = 5 · 10^–19 Nm, Duwe et al. 1989). The major part of the paper deals with long time measurements (order of hours) of variations of the apparent K _c and values of single cells (and their reversibility) caused (1) by osmotic volume changes, (2) by discocytestomatocyte transitions induced by albumin and triflouperazine, (3) by discocyte-echinocyte transitions induced by expansion of the lipid/protein bilayer (by incubation with lipid vesicles) and by ATP-depletion in physiological NaCI solution, (4), by coupling or decoupling of bilayer and cytoskeleton using wheat germ agglutinin or erythrocytes with elliptocytosis and (5) by cross-linking the cytoskeleton using diamide. These experiments showed: (1) K _c and are minimal at physiological osmolarity and temperature and well controlled over a large range of these parameters. (2) Echinocyte formation does not markedly alter the apparent membrane bending stiffness. (3) During swelling the cell may undergo a transient discocyte-stomatocyte transition. (4) Strong increases of the apparent K _c and after cup-formation or strong swelling and deflation are due to the effect of shear elasticity and surface tension. Our major conclusions are: (1) The erythrocyte membrane exhibits a shear free deformation regime which requires ATP for its maintenance. (2) Shape transitions may be caused by relative area changes either of the two monolayers of the lipid/protein bilayer (corresponding to the bilayer coupling hypothesis) or of the bilayer and the cytoskeleton where the latter mechanism appears to be more frequent. (3) The low bending stiffness and the shear free deformation regime are explained in terms of a slight excess area of the lipid bilayer leading to a pre-undulated surface profile. Freeze fracture electron microscopy studies provide direct evidence for a pre-undulated bilayer with an undulation wavelength of approximately 100 nm. Offprint requests to: E. Sackmann     

Aldosterone regulates paracellular pathway resistance in rabbit distal colon

Summary Regulation of the paracellular pathway in rabbit distal colon by the hormone aldosterone was investigated in vitro in Ussing chambers by means of transepithelial and microelectrode techniques. To evaluate the cellular and paracellular resistances an equivalent circuit analysis was used. For the analysis the apical membrane resistance was altered using the antibiotic nystatin. Under control conditions two groups of epithelia were found, each clearly dependent on the light: dark regime. Low-transporting epithelia (LT) were observed in the morning and high-transporting epithelia (HT) in the afternoon. Na⁺ transport was about 3-fold higher in HT than in LT epithelia. Incubating epithelia of both groups with 0.1 mol·1^-1 aldosterone on the serosal side nearly doubled in LT epithelia the short circuit current and transepithelial voltage but the transepithelial resistance was not influenced. Maximal values were reached after 4–5 h of aldosterone treatment. In HT epithelia due to the effect of aldosterone all three transepithelial parameters remained constant over time. Evaluation of the paracellular resistance revealed a significant increase after aldosterone stimulation in both epithelial groups. This increase suggests that tight junctions might have been regulated by aldosterone. The hormonal effect on electrolyte transport was also dependent on the physiological state of the rabbit colon. Since net Na⁺ absorption in distal colon is, in addition to transcellular absorption capacity, also dependent on the permeability of the paracellular pathway, the regulation of tight junctions by aldosterone may be a potent mechanism for improving Na⁺ absorption during hormone-stimulated ion transport.Abbreviations V _t transepithelial potential difference (mV) - R _t transepithelial resistance (·cm²) - G _t transepithelial conductance (mS·cm^-2) - I_sc calculated short circuit current (A·cm^-2) - V _a apical membrane potential difference (mV) - V _bl basolateral membrane potential difference (mV) - voltage divider ratio - R _a apical membrane resistance (·cm²) - R _bl basolateral membrane resistance (·cm²) - R _c cellular resistance ( of apical and basolateral resistance) (·cm²) - R _p resistance of the paracellular pathway (·cm²) - G _a apical membrane conductance (mS·cm^-2) - G _bl basolateral membrane conductance (mS·cm^-2) - G _p paracellular conductance (mS·cm^-2) - G _t transepithelial conductance (mS·cm^-2) - HT _contr high transporting control epithelia - LT _contr low transporting control epithelia - HT _aldo aldosterone incubated high transporting epithelia - LT _aldo aldosterone incubated low transporting epithelia     

The partly folded back solution structure arrangement of the 30 SCR domains in human complement receptor type 1 (CR1) permits access to its C3b and C4b ligands

Human complement receptor type 1 (CR1, CD35) is a type I membrane-bound glycoprotein that belongs to the regulators of complement activity (RCA) family. The extra-cellular component of CR1 is comprised of 30 short complement regulator (SCR) domains, whereas complement receptor type 2 (CR2) has 15 SCR domains and factor H (FH) has 20 SCR domains. The domain arrangement of a soluble form of CR1 (sCR1) was studied by X-ray scattering and analytical ultracentrifugation. The radius of gyration R_G of sCR1 of 13.4(±1.1) nm is not much greater than those for CR2 and FH, and its R_G/R₀ anisotropy ratio is 3.76, compared to ratios of 3.67 for FH and 4.1 for CR2. Unlike CR2, but similar to FH, two cross-sectional R_G ranges were identified that gave R_XS values of 4.7(±0.2) nm and 1.2(±0.7) nm, respectively, showing that the SCR domains adopt a range of conformations including folded-back ones. The distance distribution function P(r) showed that the most commonly occurring distance in sCR1 is at 11.5 nm. Its maximum length of 55 nm is less than double those for CR2 or FH, even though sCR1 has twice the number of SCR domains compared to CR2 Sedimentation equilibrium experiments gave a mean molecular weight of 235 kDa for sCR1. This is consistent with the value of 245 kDa calculated from its composition including 14 N-linked oligosaccharide sites, and confirmed that sCR1 is a monomer in solution. Sedimentation velocity experiments gave a sedimentation coefficient of 5.8 S. From this, the frictional ratio (f/f₀) of sCR1 was calculated to be 2.29, which is greater than those of 1.96 for CR2 and 1.77 for FH. The constrained scattering modelling of the sCR1 solution structure starting from homologous SCR domain structures generated 5000 trial conformationally randomised models, 43 of which gave good scattering fits to show that sCR1 has a partly folded-back structure. We conclude that the inter-SCR linkers show structural features in common with those in FH, but differ from those in CR2, and the SCR arrangement in CR1 will permit C3b or C4b to access all three ligand sites.     

Measurement of net ecosystem production and ecosystem respiration in a Zoysia japonica grassland,central Japan,by the chamber method

Measuring light, temperature, soil moisture, and growth provides a better understanding of net ecosystem production (NEP), ecosystem respiration (R _eco), and their response functions. Here, we studied the variations in NEP and R _eco in a grassland dominated by a perennial warm-season C₄ grass, Zoysia japonica. We used the chamber method to measure NEP and R _eco from August to September 2007. Biomass and leaf area index (LAI) were also measured to observe their effects on NEP and R _eco. Diurnal variations in NEP and R _eco were predicted well by light intensity (PPFD) and by soil temperature, respectively. Maximum NEP (NEP_max) values on days of year 221, 233, 247, and 262, were 2.44, 2.55, 3.90, and 4.17 μmol m⁻² s⁻¹, respectively. Throughout the growing period, the apparent quantum yield (α) increased with increasing NEP_max that ranged from 0.0154 to 0.0515, and NEP responded to the soil temperature changes by 44% and R _eco changes by 48%, and R _eco responded from 88 to 94% with the soil temperature diurnally. NEP’s light response and R _eco’s temperature response were affected by soil water content; more than 27% of the variation in NEP and 67% of the variation in R _eco could be explained by this parameter. NEP was strongly correlated with biomass and LAI, but R _eco was not, because environmental variables affected R _eco more strongly than growth parameters. Using the light response of NEP, the temperature response of R _eco, and meteorological data, daily NEP and R _eco were estimated at 0.67, 0.81, 1.17, and 1.56 g C m⁻², and at 2.88, 2.50, 3.51, and 3.04 g C m⁻², respectively, on days of year 221, 233, 247, and 262. The corresponding daily gross primary production (NEP + R _eco) was 3.5, 3.3, 4.6, and 4.6 g C m⁻².     

Autotrophic and heterotrophic respiration in needle fir and Quercus-dominated stands in a cool-temperate forest, central Korea

To investigate annual variation in soil respiration (R _S) and its components [autotrophic (R _A) and heterotrophic (R _H)] in relation to seasonal changes in soil temperature (ST) and soil water content (SWC) in an Abies holophylla stand (stand A) and a Quercus-dominated stand (stand Q), we set up trenched plots and measured R _S, ST and SWC for 2 years. The mean annual rate of R _S was 436 mg CO₂ m⁻² h⁻¹, ranging from 76 to 1,170 mg CO₂ m⁻² h⁻¹, in stand A and 376 mg CO₂ m⁻² h⁻¹, ranging from 82 to 1,133 mg CO₂ m⁻² h⁻¹, in stand Q. A significant relationship between R _S and its components and ST was observed over the 2 years in both stands, whereas a significant correlation between R _A and SWC was detected only in stand Q. On average over the 2 years, R _A accounted for approximately 34% (range 17–67%) and 31% (15–82%) of the variation in R _S in stands A and Q, respectively. Our results suggested that vegetation type did not significantly affect the annual mean contributions of R _A or R _H, but did affect the pattern of seasonal change in the contribution of R _A to R _S.     

Interaction of cryptogein with its binding sites in tobacco plasma membrane studied using the piezoelectric biosensor

Elicitins are low-molecular-weight proteins representing the elicitor family secreted by many species of the oomycete Phytophthora. Elicitins induce a hypersensitive reaction in tobacco, a process that is triggered by binding of elicitin to the high-affinity site on the plasma membrane. Specific interaction of cryptogein with the binding sites on tobacco plasma membranes was studied using the piezoelectric biosensor in real time in a flow-through mode. Cryptogeins (wild-type and mutant forms) were covalently immobilized on the sensing surface, and membrane vesicles containing receptors were in solution. Kinetic characterization of the interaction provided values of kinetic rate association (k_a) = 5.74 · 10⁶ M¹ s⁻¹ and kinetic rate dissociation (k_d) = 6.87 10⁻⁴ s⁻¹ constants, respectively. The kinetic equilibrium dissociation constant was calculated as K_D = 12.0 nM. The piezoelectric biosensor appeared to be a convenient tool for studying interactions of receptors embedded in membrane vesicles.     

The production of xylitol from d-xylose by fermentation with Hansenula polymorpha

We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone. Thus, at an initial pH of 5.5, the maximum specific production rate (μ_m) was 0.41 h⁻¹, the overall biomass yield (Y _x/s ^G) was 0.12 g g⁻¹, the specific d-xylose-consumption rate (q _s ) was 0.075 g g⁻¹ h⁻¹ (for t = 75 h), the specific xylitol-production rate (q _Xy ) was 0.31 g g⁻¹ h⁻¹ (for t = 30 h) and the overall yields of ethanol (Y _E/s ^G) and xylitol (Y _Xy/s ^G) were 0.017 and 0.61 g g⁻¹ respectively. Both q _s and q _Xy decreased during the course of the experiments once the exponential growth phase had finished. Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998     

An immortal cell line to study the role of endogenous cftr in electrolyte absorption

Summary The intact human reabsorptive sweat duct (RD) has been a reliable model for investigations of the functional role of “endogenous” CFTR (cystic fibrosis transmembrane conductance regulator) in normal and abnormal electrolyte absorptive function. But to overcome the limitations imposed by the use of fresh, intact tissue, we transformed cultured RD cells using the chimeric virus Ad5/SV40 1613 ori-. The resultant cell line, RD2(NL), has remained differentiated forming a polarized epithelium that expressed two fundamental components of absorption, a cAMP activated Cl⁻ conductance (G_cl) and an amiloride-sensitive Na⁺ conductance (G_Na). In the unstimulated state, there was a low level of transport activity; however, addition of forskolin (10⁻⁵ M) significantly increased the Cl⁻ diffusion potential (V_t) generated by a luminally directed Cl⁻ gradient from − 15.3 ± 0.7 mV to −23.9 ± 1.1 mV,n=39; and decreased the transepithelial resistance (R_t) from 814.8 ± 56.3 Ω.cm² to 750.5 ± 47.5 Ω.cm²,n=39, (n=number of cultures). cAMP activation, anion selectivity (Cl⁻>I⁻>gluconate), and a dependence upon metabolic energy (metabolic poisoning inhibited G_Cl), all indicate that the G_Cl expressed in RD2(NL) is in fact CFTR-G_Cl. The presence of an apical amiloride-sensitive G_Na was shown by the amiloride (10⁻⁵ M) inhibition of G_Na as indicated by a reduction of V_t and equivalent short circuit current by 78.0 ± 3.1% and 77.9 ± 2.6%, respectively, and an increase in R_t by 7.2 ± 0.8%,n=36. In conclusion, the RD2(NL) cell line presents the first model system in which CFTR-G_Cl is expressed in a purely absorptive tissue. It provides an opportunity to study the properties and role of CFTR in the context of absorptive function in immortalized epithelial cells.     

Optimization of production of C-phycocyanin and extracellular polymeric substances by Arthrospira sp.

The key factors influencing the production of C-phycocyanin (C-PC) and extracellular polymeric substances (EPS) by photoautotrophic culture of Arthrospira sp. were optimized using Taguchi method. Six factors were varied at either three or two levels as follows: light intensity at three levels; three initial culture pHs; two species of Arthrospira; three concentrations of Zarrouk’s medium; three rates of aeration of the culture with air mixed with 2% v/v carbon dioxide; and two incubation temperatures. All cultures ran for 14 days. The optimal conditions for the production of C-PC and EPS were different. For both products, the best cyanobacterium proved to be Arthrospira maxima IFRPD1183. The production of C-PC was maximized with the following conditions: a light intensity of 68 µmol photons m⁻² s⁻¹ (a diurnal cycle of 16-h photoperiod and 8-h dark period), an initial pH of 10, the full strength (100%) Zarrouk’s culture medium, an aeration rate of 0.6 vvm (air mixed with 2% v/v CO₂) and a culture temperature of 30 °C. The concentration of Zarrouk’s medium was the most important factor influencing the final concentration of C-PC. The optimal conditions for maximal production of EPS were as follows: a light intensity of 203 µmol photons m⁻² s⁻¹ with the earlier specified light–dark cycle; an initial pH of 9.5; a 50% strength of Zarrouk’s medium; an aeration rate of 0.2 vvm (air mixed with 2% v/v CO₂); and a temperature of 35 °C. Production of C-PC and EPS in raceway ponds is discussed.

     

Assessing the resistance risk to emamectin benzoate in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae): selection,cross-resistance dynamics and estimates of realized heritability

Emamectin benzoate, a non-systemic, translaminar, and broad spectrum insecticide, is excessively used in cotton. It kills the pest by suppressing the muscle contraction. Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is one of the major sap sucking pests of cotton in many countries and has been shown resistance to various insecticides. In this study, we have continuously selected P. solenopsis with emamectin benzoate in the laboratory from G₃ to G₁₈ to determine the resistance development and resistance risk to emamectin benzoate and also to evaluate the dynamics of cross-resistance (CR) development with three other insecticides. After continuing selection of P. solenopsis for 16 generations with emamectin benzoate, the emamectin selected strain (Ema-SEL) developed a 280.15-fold resistance when tested at G₁₉. Ema-SEL strain showed no CR to abamectin (0.28–1.65-fold), and profenofos (0.12–0.29-fold), but a very low to low CR to cypermethrin (6.02–11.29-fold). Abamectin was negatively cross-resistant with emamectin benzoate in Ema-SEL strain at G₁₃, G₁₅ and G₁₉ while profenofos also exhibited similar results at G₁₃, G₁₅, G₁₇ and G₁₉. Realized heritability (h²) of resistance to emamectin benzoate was 0.24 from G₃ to G₁₉. The results of projected rate of resistance development showed that if h² = 0.24, 0.34, and 0.44 at slope = 1.08, then 2.03, 1.43, and 1.11 generations, respectively are required for tenfold increase in LC₅₀ at 95 % selection intensity. Results of the present study suggested that P. solenopsis has the ability to develop resistance to emamectin benzoate but it can be managed by the alternate use of other insecticides including abamectin, profenofos and cypermethrin due to lack of/or very low to low CR with these insecticides.     

Growth characteristics of Uranoscopus scaber Linnaeus 1758, inhabiting the Iskenderun Bay (Northeastern Mediterranean)

This study aimed to determine the age and some growth characteristics of Atlantic stargazer (Uranoscopus scaber) from Iskenderun Bay (Northeastern Mediterranean). For this purpose, a total of 150 Atlantic stargazer ranging in size from 9.1 to 28.0 cm in total length (weight: 11.7–345.7 g) were collected as by-catch from a commercial trawl fishing boat at a depth of 80–100 m between May 2015 and January 2016. The bottom trawl gear used was equipped with a 44 mm stretched mesh size net at the cod-end. The percentage of females and males were 46.7% and 53.3% respectively. The total length–weight relationships equation with coefficient of determination (R²) were found as W = 0.011*TL^3.131, R² = .9728, for all individuals, W = 0.015*TL^3.021, R² = .9512 for females and W = 0.0102*TL^3.136, R² = .9553 for males. By using the von Bertalanffy equation, the growth parameters of Atlantic stargazer were estimated to be L_∞ = 42.35 cm, k = 0.098, t₀ = −1.8474 for all individuals; L_∞ = 36.92 cm, k = 0.138, t₀ = −1.2693 for females and L_∞ = 38.77 cm, k = 0.1, t₀ = −2.334 for males. In this study, age reading was done by two independent readers and index of average percentage error (IAPE) was calculated as 6.1%. The highest condition factor value calculated as 1.81 in the age group 6 and the lowest condition factor value was calculated as 1.48 in the age group 1.     

Iodine-infused aeration for hull fouling prevention: a vessel-scale study

Biofouling is a significant economic and ecological problem, causing reduced vessel performance and increases in fuel consumption and emissions. Previous research has shown iodine vapor (I₂)-infused aeration to be an environmentally friendly method for deterring the settlement of fouling organisms. An aeration system was deployed on a vessel with hull sections coated with two types of antifoulant coatings, Intersleek^® 1100 (fouling-release) and Interspeed^® BRA-640 (ablative copper biocide), as well as an inert epoxy barrier coating, to assess the effectiveness of aeration in conjunction with common marine coatings. I₂-infused aeration resulted in consistent reductions of 80–90% in hard fouling across all three coatings. Additionally, aeration reduced the soft fouling rate by 45–70% when used in conjunction with both Intersleek^® and Interspeed^® BRA versus those coatings alone. The results of this study highlight the contribution of I₂-infused aeration as a standalone mechanism for fouling prevention or as a complement to traditional antifouling coatings.