Effects of temperature on metabolic rate and lower dissolved oxygen tolerance of juvenile speckled peacock bass Cichla temensis

The speckled peacock bass Cichla temensis is a popular sport and food fish that generates substantial angling tourism and utilitarian harvest within its range. Its popularity and value make this species important for management and a potential aquaculture candidate for both fisheries enhancement and food fish production. However, little is known of optimal physiochemical conditions in natural habitats, which also are important for the development of hatchery protocols for handling, spawning and grow-out. Speckled peacock bass have been documented to have high sensitivity to extreme temperatures, but the metabolic underpinnings have not been evaluated. In this study, the effects of temperature (25, 30 and 35°C) on the standard metabolic rate (SMR) and lower dissolved oxygen tolerance (LDOT) of juvenile speckled peacock bass (mean ± standard error total length 153 ± 2 mm and wet weight 39.09 ± 1.37 g) were evaluated using intermittent respirometers after an acclimation period of 2 weeks. Speckled peacock bass had the highest SMR at 35°C (345.56 ± 19.89 mgO₂ kg⁻¹ h⁻¹), followed by 30°C (208.16 ± 12.45 mgO₂ kg⁻¹ h⁻¹) and 25°C (144.09 ± 10.43 mgO₂ kg⁻¹ h⁻¹). Correspondingly, the Q₁₀, or rate of increase in aerobic metabolic rate (MO₂) relative to 10°C, for 30–35°C was also greater (2.76) than from 25 to 30°C (2.08). Similarly, speckled peacock bass were the most sensitive to hypoxia at the warmest temperature, with an LDOT at pO₂ of 90 mmHg (4.13 mg l⁻¹) at 35°C compared to pO₂ values of 45 mmHg (2.22 mg l⁻¹) and 30 mmHg (1.61 mg l⁻¹) at 30 and 25°C, respectively. These results indicate that speckled peacock bass are sensitive to temperatures near 35°C, therefore we recommend managing and rearing this species at 25–30°C.     

Kinetic comparisons of mesophilic and thermophilic aerobic biomass

Kinetic parameters describing growth and decay of mesophilic (30°C) and thermophilic (55°C) aerobic biomass were determined in continuous and batch experiments by using oxygen uptake rate measurements. Biomass was cultivated on a single soluble substrate (acetate) in a mineral medium. The intrinsic maximum growth rate (μ _max) at 55°C was 0.71±0.09 h⁻¹, which is 1.5 times higher than the μ _max at 30°C (0.48±0.11 h⁻¹). The biomass decay rates increased from 0.004 h⁻¹ at 30°C to 0.017 h⁻¹ at 55°C. Monod constants were very low for both types of biomass: 9±2 mg chemical oxygen demand (COD) l⁻¹at 30°C and 3±2 mg COD l⁻¹at 55°C. Theoretical biomass yields were similar at 30 and 55°C: 0.5 g biomass COD (g acetate COD)⁻¹. The observed biomass yields decreased under both temperature conditions as a function of the cell residence time. Under thermophilic conditions, this effect was more pronounced due to the higher decay rates, resulting in lower biomass production at 55°C compared to 30°C. Electronic Publication     

The Antarctic notothenioid fish <Emphasis Type="Italic">Pagothenia borchgrevinki</Emphasis> is thermally flexible: acclimation changes oxygen consumption

Antarctic marine organisms are considered to have extremely limited ability to respond to environmental temperature change. However, here we show that the Antarctic notothenioid fish Pagothenia borchgrevinki is an exception to this theory. P. borchgrevinki was able to acclimate its resting metabolic rate and resting ventilation frequency after a 5°C rise in temperature. Acute exposure to 4°C resulted in an elevation in metabolic rate (57.8 ± 4.79 mg O₂ kg⁻¹ h⁻¹) and resting ventilation rate (40.38 ± 1.61 breaths min⁻¹) compared with fish at −1°C (metabolic rate 34.45 ± 3.12 mg O₂ kg⁻¹ h⁻¹; ventilation rate 29.88 ± 3.72 breaths min⁻¹). However, after a 1-month acclimation period, there was no significant difference in the metabolic rate (cold fish 29.52 ± 3.01; warm fish 31.13 ± 2.30 mg O₂ kg⁻¹ h⁻¹), or the resting ventilation rate (cold fish 28.75 ± 0.98; warm fish 34.25 ± 2.28 breaths min⁻¹) of cold and warm acclimated fish. Acclimation changes to the rate of oxygen consumption following exhaustive exercise were complex. The pattern of oxygen consumption during recovery from exhaustive exercise was not significantly different in either cold or warm acclimated fish.     

Cell-substrate separation: effect of applied force and temperature

We measure the change in cell-substrate separation in response to an upward force by combining two relatively new techniques, Electric Cell-substrate Impedance Sensing (ECIS) to measure average cell-substrate separation, and collagen-coated magnetic beads to apply force to the top (dorsal) surface of cells. The collagen-coated ferric oxide beads attach to integrin receptors in the dorsal surfaces of osteoblastlike ROS 17/2.8 cells. Magnetic force is controlled by the position and the number of permanent magnets, applying an average 320 or 560 pN per cell. Comparing model calculations with experimental impedance data, the junctional resistivity of the cell layer and the average distance between the lower (ventral) cell surface and substrate can be determined. The ECIS analysis shows that these forces produce an increase in the distance between the ventral cell surface and the substrate that is in the range of 10 to 25%. At temperatures of 4°, 22° and 37 °C, the measured cell surface-substrate distances without magnetic beads are 84 ± 4, 45 ± 2 and 38 ± 2 nm. The force-induced changes at 22° are 11 ± 3 and 21 ± 3 nm for 320 and 560 pN, and at 37° they are 5 ± 2 and 9 ± 2 nm. The resulting cell-substrate spring constants at 22° and 37° are thus about 28 and 63 pN nm^–1 (dyne cm^–1). Using a reasonable range for the number for individual integrin-ligand adhesion bonds gives a range for the spring constant of the individual adhesion bond of from about 10^–3 to 10^–1 pN nm^–1. These data also provide evidence that the number of adhesion bonds per cell increases with temperature. Received: 20 June 1997 / Accepted: 24 August 1997     

The critical thermal limits for the stone loach, Noemacheilus barbatulus, from three populations in north-west England

1. The chief objective was to determine the upper and lower thermal limits for feeding and survival in the stone loach, Noemacheilus barbatulus, using juveniles (total length 30–45 mm, live weight 0.25–0.80 g) from one population and adults (total length 77–100 mm, live weight 3.6–7.9 g) from three populations. 2. Fish were acclimatized to constant temperatures of 3, 7, 10, 15, 20, 25 and 27°C; then the temperature was changed at a rate of 1°C/30min to determine the critical limits for feeding, survival over 7 days (incipient lethal temperature), or survival for 10 min or less (ultimate lethal temperature). The rate of 1°C/30min was the optimum value from preliminary experiments, using nine rates from 0.5°C/48h to 18°Ch^?1. As values for adults were not significantly different between populations, they were pooled to provide arithmetic means (with 95% CL) for the thermal limits at each acclimation temperature. 3. Feeding limits increased with acclimation temperature to upper and lower mean values of 28.0 ± 0.15°C and 5.1 ± 0.55°C for adults, 25.0 ± 0.54°C and 6.1 ± 0.92°C for juveniles. Incipient lethal levels defined a tolerance zone within which stone loach survive for a considerable time; upper limits increased with acclimation temperature to reach a maximum plateau of 29.1 ± 0.18°C for adults and 29.0 ± 0.40°C for juveniles; lower limits also increased from near 0°C to 3.0 ± 0.40°C for adults and juveniles. Upper limits for the ultimate lethal level increased with acclimation temperature to a maximum plateau of 33.5°C for adults (95% CL ± 0.19) and juveniles (95% CL ± 0.40), whilst the lower limits increased from near 0°C to 2.5 ± 0.30°C. At acclimation temperatures below 20°C, upper incipient and ultimate lethal values were significantly lower for juveniles than those for adults. 4. The thermal tolerance of stone loach was higher than that of juvenile Atlantic salmon or brown trout, one or both of these species often being dominant in streams with stone loach.     

Acute Toxicity of Arsenic under Different Temperatures and Salinity Conditions on the White Shrimp Litopenaeus vannamei

The aim of this study was to determine acute toxicity in the post larvae of the white shrimp Litopenaeus vannamei after 96 h of exposure to dissolved arsenic under three different temperatures and salinity conditions. Recent reports have shown an increase in the presence of this metalloid in coastal waters, estuaries, and lagoons along the Mexican coast. The white shrimp stands out for its adaptability to temperature and salinity changes and for being the main product for many commercial fisheries; it has the highest volume of oceanic capture and production in Mexican shrimp farms. Lethal concentrations (LC₅₀–96 h) were obtained at nine different combinations (3?×?3 combinations in total) of temperature (20, 25, and 30 °C) and salinity (17, 25, and 33) showing mean LC₅₀–96 h values (±standard error) of 9.13?±?0.76, 9.17?±?0.56, and 6.23?±?0.57 mgAs?L^?1(at 20 °C and 17, 25, and 33 salinity); 12.29?±?2.09, 8.70?±?0.82, and 8.03?±?0.59 mgAs?L^?1 (at 25 °C and 17, 25, and 33 salinity); and 7.84?±?1.30, 8.49?±?1.40, and 7.54?±?0.51 mgAs?L^?1 (at 30 °C and 17, 25, and 33 salinity), respectively. No significant differences were observed for the optimal temperature and isosmotic point of maintenance (25 °C–S 25) for the species, with respect to the other experimental conditions tested, except for at 20 °C–S 33, which was the most toxic. Toxicity under 20 °C–S 33 conditions was also higher than 25 °C–S 17 and 20 °C (S 17 or 25). The least toxic condition was 25 °C–S 17. All this suggests that the toxic effect of arsenic is not affected by temperature changes; it depends on the osmoregulatory pattern developed by the shrimp, either hyperosmotic at low salinity or hiposmotic at high salinity, as observed at least on the extreme salinity conditions here tested (17 and 33). However, further studies testing salinities near the isosmotic point (between 20 and 30 salinities) are needed to clarify these mechanisms.     

Effect of different doses of organic fertilizer (cow dung) on pond productivity and fish biomass in stillwater ponds

The effects of five (5 000, 10 000, 15 000, 20 000, 24 000 kg ha^?1 year^?1) different doses of organic fertilizer (cow dung) were studied on pond productivity in terms of plankton production and fish biomass in freshwater fish ponds. The grow out period was 60 days. Physico-chemical factors of pond waters were also monitored. With an increase in the fertilizer dose, biochemical oxygen demand (BOD) (1.7 ± 0.1 – 10.35 ± 0.05 mg L^?1), O-PO₄ (0.04 ± 0.0 – 0.77 ± 0.02 mg L^?1) and NH₄-N (0.03 ± 0.02 – 0.32 ± 0.02 mg L^?1) increased significantly (P < 0.05). Alkalinity (79.0 ± 1.6 – 164.0 ± 3.8 mg L^?1) also increased with the increase in fertilizer dose, declining after 60 and 75 days (48.8 ± 1.13 – 67.9 ± 2.1 mg L^?1). NO₃-N was maximum (1.66 ± 0.2 mg L^?1) in the ponds which received cow dung at 15 000 kg ha^?1 year^?1, and declined (0.94 ± 0.5 mg L^?1) at higher doses. Dissolved oxygen (DO) remained significantly high (4.7 mg L^?1) up to the third (15 000 kg ha^?1 year^?1) treatment. Highest plankton population (phytoplankton 17 350.0 ± 1 250.0 no L^?1), zooplankton (373.0 ± 22.0 no L^?1), species diversity (phytoplankton 3.0, zooplankton 2.3), fish biomass (4.45 kg) and specific growth rate (SGR) (2.36 % body weight (BW) d^?1) were also observed in ponds which were treated with fertilizer at 15 000 kg ha^?1 year^?1. However, at higher doses, a decline in these parameters (phytoplankton, 0.0 – 8 810.0 ± 690.0 no L^?1; zooplankton, 0.0 – 205.0 ± 25.0 no L^?1; fish biomass, 2.3 kg; SGR, 1.25 % body weight (BW) d^?1) was observed. Furthermore, with a decrease in the water temperature from 24 °C (on day 60) to 21 °C (on day 75), a decline in nutrient release, plankton population L^?1 and species diversity was observed. Sediment analysis indicated that with an increase in the fertilizer dosage, a significant and progressive increase in the accumulation of organic carbon (0.787 ± 0.006 – 0.935 ± 0.01), total nitrogen (0.877 ± 0.071 – 1.231 ± 0.03), NH₄-N (54.4 ± 0.57 – 68.95 ± 0.81), NO₃-N (78.5 ± 1.21 – 98.5 ± 0.35), total P (140.0 ± 0.50 – 151.0 ± 1.27) and soluble P (7.15 ± 0.18 – 10.1 ± 0.56) took place; similarly, electrical conductivity (EC) values of sediment also increased progressively (from 200.0 ± 7.1–300.0 ± 10.63 μ mhos cm^?1).     

Influence of temperature on process efficiency and microbial community response during the biological removal of chlorophenols in a packed-bed bioreactor

Two reactors, initially operated at 14 and 23±1°C (RA and RB, respectively), were inoculated with a bacterial consortium enriched and acclimatized to the respective temperatures over 4 months. The biofilms, formed in the reactors, were studied using scanning electron microscopy, cultivation of the biofilm microflora, and physiological analysis of the isolates. Two bacteria able to mineralize chlorophenols under a large range of temperature (10–30°C) were isolated from the biofilm communities of reactors RA and RB and characterized as Alcaligenaceae bacterium R14C4 and Cupriavidus basilensis R25C6, respectively. When temperature was decreased by 10°C, the chlorophenols removal capacity was reduced from 51.6 to 22.8 mg l⁻¹ h⁻¹ in bioreactor RA (from 14 to 4°C) and from 59.3 to 34.7 mg l⁻¹ h⁻¹ in bioreactor RB (from 23±1 to 14°C). Fluorescence in situ hybridization (FISH) of the biofilm communities showed that, in all temperatures tested, the β-proteobacteria were the major bacterial community (35–47%) followed by the γ-proteobacteria (12.0–6.5%). When the temperature was decreased by 10°C, the proportions of γ-proteobacteria and Pseudomonas species increased significantly in both microbial communities.     

Removal of Co by carbonaceous material obtained through solution combustion of tamarind shell

New carbonaceous materials were obtained through solution combustion process of tamarind shell in the presence of urea and ammonium nitrate, and all of them were tested for Co removal. The effect of temperature (from 600 to 1000°C) and water volume on surface texture of carbonaceous material and its adsorptive capacity was evaluated. Scanning electron microscope, Fourier transform infrared spectroscopy, X-ray powder diffraction, and Brunauer–Emmett–Teller (BET) model were used to characterize the obtained carbonaceous material before applying for the removal of cobalt. The point of zero charge was also determined. The results indicate that BET-specific surface areas ranged from 6.40 to 216.72 m²g^?1 for the carbonaceous materials obtained at 600, 700, 800, 900, and 1000°C. The one obtained at 900°C (CombTSF₉₀₀) was found to be the most effective adsorbent for the removal of Co(II) ions from aqueous solutions, with a maximum sorption capacity (Q_max) of 43.56 mg/g. Carbonaceous material obtained through the solution combustion process improves morphological characteristics of adsorbent in a short time, and could be used as an alternative method for the removal of cobalt.     

Microtuberization in potato (Solanum tuberosum L.)

Twenty-two genotypes of potato (Solanum tuberosum L.) were induced to form microtubers under six in vitro culture conditions. Cultures maintained under a short photoperiod (10 h of 6–12 μmol m^–2 s^–1) and low temperatures (day 20°±2°C and night 18°±2°C) had both a higher yield (255 mg/plantlet) and a greater number (2/plantlet) of microtubers than those maintained under long days (16 h of 38–50 μmol m^–2 s^–1) combined with high temperatures (day 28°±2°C and night 25°±2°C) (yield 207 mg/plantlet; microtuber number, 0.9/plantlet), over a wide range of genotypes. After the plantlets had been cultured under long days for an initial period of 60 days, continuous darkness advanced microtuberization by 2–3 months in various genotypes. Under short-day and low-temperature conditions the addition of 6-benzylaminopurine increased microtuber yield from 255 mg/plantlet to 645 mg/plantlet and average microtuber weight from 115 mg to 364 mg. A similar pattern was observed under conditions of long days and high temperature, and continuous darkness and low-temperature. Microtubers produced under light had a greater number of eyes (maximum average: 5.96/microtuber) than those produced in the dark (maximum average: 3.50/plantlet). The genotype × cultural conditions interactions were significant indicating the importance of developing genotype-specific protocols to maximize microtuberization. Received: 17 September 1997 / Revision received: 12 December 1997 / Accepted: 1 January 1998     

Biomass and terpenoids produced by mutant strains of <Emphasis Type="Italic">Arthrospira</Emphasis> under low temperature and light conditions

The filamentous Cyanobacterium Arthrospira is commercially produced and is a functional, high-value, health food. We identified 5 low temperature and low light intensity tolerant strains of Arthrospira sp. (GMPA1, GMPA7, GMPB1, GMPC1, and GMPC3) using ethyl methanesulfonate mutagenesis and low temperature screening. The 5 Arthrospira strains grew rapidly below 14?°C, 43.75 μmol photons m^?2 s^?1 and performed breed conservation at 2.5?°C, 8.75 μmol photons m^?2 s^?1. We used morphological identification and molecular genetic analysis to identify GMPA1, GMPA7, GMPB1 and GMPC1 as Arthrospira platensis, while GMPC3 was identified as Arthrospira maxima. Growth at different culture temperatures was determined at regular intervals using dry biomass. At 16?°C and 43.75 μmol photons m^?2 s^?1, the maximum dry biomass production and the mean dry biomass productivity of GMPA1, GMPB1, and GMPC1 were 2057?±?80 mg l^?1, 68.7?±?2.5 mg l^?1 day^?1, 1839?±?44 mg l^?1, 60.6?±?1.8 mg l^?1 day^?1, and 2113?±?64 mg l^?1, 77.7?±?2.5 mg l^?1 day^?1 respectively. GMPB1 was chosen for additional low temperature tolerance studies and growth temperature preference. In winter, GMPB1 grew well at mean temperatures <10?°C, achieving 3258 mg dry biomass from a starting 68 mg. In summer, GMPB1 grew rapidly at mean temperatures more than 28?°C, achieving 1140 mg l^?1 dry biomass from a starting 240 mg. Phytonutrient analysis of GMPB1 showed high levels of C-phycocyanin and carotenoids. Arthrospira metabolism relates to terpenoids, and the methyl-d-erythritol 4-phosphate pathway is the only terpenoid biosynthetic pathway in Cyanobacteria. The 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) gene from GMPB1 was cloned and phylogenetic analysis showed that GMPB1 is closest to the Cyanobacterium Oscillatoria nigro-viridis PCC711. Low temperature tolerant Arthrospira strains could broaden the areas suitable for cultivation, extend the seasonal cultivation time, and lower production costs.     

Dissolved oxygen and thermal regimes of a Ugandan crater lake

This paper quantifies the temporal pattern of thermal stratification and deoxygenation in Lake Nkuruba, a small (3 ha), deep (maximum depth = 38 m) crater lake in western Uganda. Dissolved oxygen penetrated to an average depth of 9 m and a maximum depth of 15 m below which the lake was permanently anoxic over the 2 years of study. Although surface oxygen levels were correlated with both surface water temperature and rainfall, seasonal cycles of dissolved oxygen were not well-defined and may have been obscured by the high frequency of short-term fluctuations and by inter-annual variations caused by shifts in rainfall. Surface water temperature averaged 23.3±0.7 °C (S.D.) and varied directly with air temperature. Both diurnal changes and top-bottom temperature differentials were small averaging 1.7±0.7 °C and 1.6±0.8 °C, respectively. Thermal stability ranged from 101.3 to 499.9 g-cm cm^-2 and was positively related to surface water temperature suggesting that this small protected lake responds rapidly to short-term meteorological changes. Because contribution to the annual heat exchange cycle was confined to upper waters, the lake's annual heat budget was low, 1,073.8 cal cm^-2 yr^-1. However, net primary productivity was relatively high averaging 1.3 g C m^-2d^-1. The region where Lake Nkuruba is situated experienced a very strong earthquake (6.2 on the Richter scale) on 4 February, 1994. Subsequently, water levels dropped markedly in the lake, falling 3.14 m over a 5-month period. This revised version was published online in September 2006 with corrections to the Cover Date.     

The critical thermal limits for the bullhead, Cottus gobio, from three populations in north-west England

1. The objective was to determine the thermal limits for feeding and survival in the bullhead, Cottus gobio, using juveniles (total length 20–30 mm, live weight 0.5–1.5 g) from one population and adults (50–70 mm, 3.5–5.5 g) from three populations. 2. Fish were acclimated to constant temperatures (3, 7, 10, 15, 20, 25 or 27 °C) and the temperature was then changed at a rate of 1 °C /30 min to determine the critical limits for feeding, survival over 7 days (incipient lethal temperature), or survival for 10 min or less (ultimate lethal temperature). The rate of 1 °C/30 min was the optimum value from preliminary experiments, using nine rates from 0.5 °C/48 h to 18 °C h^?1. As values for adults were not significantly different between populations, they were pooled to provide arithmetic means (with 95% CL) for the thermal limits at each acclimation temperature. 3. Feeding limits increased with acclimation temperature to upper and lower mean values (± 95% CL) of 26.5 ± 0.16 °C and 4.2 ± 0.20 °C for adults, 26.6 ± 0.59 °C and 5.0 ± 0.55 °C for juveniles. Incipient lethal levels defined a tolerance zone within which fish survive indefinitely; upper limits increased with acclimation temperature to a plateau of 27.6 ± 0.22 °C for adults and 27.5 ± 0.47 °C for juveniles, lower limits increased from near 0 °C to 2.5 ± 0.31 °C for adults and 2.7 ± 0.47 °C for juveniles. Ultimate lethal levels increased with acclimation temperature to a plateau of 32.5 ± 0.24 °C for adults and 32.6 ± 0.46 °C for juveniles, whilst the lower limits increased from near 0 to 0.9 ± 0.29 °C. Upper feeding, incipient and ultimate lethal values were significantly lower for juveniles than those for adults at acclimation temperatures < 20, < 20 and < 15 °C, respectively. 4. The thermal tolerance of bullheads was slightly lower than that of stone loach, similar to that of juvenile Atlantic salmon and higher than that of brown trout; the thermal limits for feeding were much wider than those for salmon or trout.     

Age‐ and temperature‐dependent oviposition model of Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) with Tetranychus urticae as prey

In this study, we developed an oviposition model of Neoseiulus californicus (McGregor) with Tetranychus urticae Koch as prey. To obtain data for the model, we investigated the longevity, fecundity and survivorship of adult female N. californicus at six constant temperatures (16, 20, 24, 28, 32 and 36°C), 60–70% RH and a photoperiod of 16 : 8 (L : D) h. Longevity (average ± SE) decreased as temperature increased and was longest at 16°C (46.7 ± 5.25 days) and shortest at 36°C (12.8 ± 0.75 days). Adult developmental rate (1/average longevity) was described by the Lactin 1 model (r² = 0.95). The oviposition period (average±SE) was also longest at 16°C (29.8 ± 2.93 days) and shortest at 36°C (6.7 ± 0.54 days). Fecundity (average±SE) was greatest at 24°C (43.8 ± 3.23 eggs) and lowest at 36°C (15.9 ± 1.50 eggs). The oviposition model comprised temperature‐dependent fecundity, age‐specific cumulative oviposition rate and age‐specific survival rate functions. The temperature‐dependent fecundity was best described by an exponential equation (r² = 0.81). The age‐specific cumulative oviposition rate was best described by the three‐parameter Weibull function (r² = 0.96). The age‐specific survival rate was best described by a reverse sigmoid function (r² = 0.85).     

Production enhancement of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in Halogeometricum borinquense,characterization of the bioplastic and desalination of the bioreactor effluent

Polyhydroxyalkanoates (PHAs) are a replacement of conventional single-use plastics. Bioprocess conditions of the extreme halophilic archaeon Halogeometricum borinquense strain RM-G1 were selected resulting in the synthesis of 66.80 ± 1.69 % PHA (of cell dry mass) in 72 h using glycerol and tryptone as carbon and nitrogen sources respectively, yielding volumetric productivity of 0.206 ± 0.006 gL⁻¹ h⁻¹ in a repeated batch process in a small-scale bioreactor where 20 % of the production medium was used as the inoculum for the subsequent batch. The purified PHA was characterized as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 10.21 mol% 3-hydroxyvalerate content possessing glass transition temperature -12.6 °C, degradation temperature 285 °C, number average molecular weight 156,899 Da, weight average molecular weight 288,723 Da, polydispersity index 1.8 and melting temperatures 139.1 °C and 152.5 °C. Maximum (21.7 ± 0.6 L m^-2 h⁻¹) and average (17.2 ± 0.6 L m^-2 h⁻¹) flux values were their respective highest and crystallization time was its least (3.0 ± 0.16 h) when ΔT was 90 °C and polytetrafluoroethylene membrane was applied for desalination of the bioreactor effluent by Direct Contact Membrane Distillation. While using polyvinylidene fluoride membrane, maximum 25.5 ± 0.5 L m^-2 h⁻¹ and average 18.6 ± 0.2 L m^-2 h⁻¹ fluxes were obtained and crystallization time decreased (3.25 ± 0.16 h) even when ΔT was lowered by 20 °C.     

Temperature Dependence of the Sodium Pump is Altered in the Cerebral Cortex of CCK<Subscript>2</Subscript> Receptor-Deficient Mice

Previously we have shown that the temperature dependence of the sodium pump (Na⁺,K⁺-ATPase) is altered under different neuropathological conditions. In this study we compared temperature dependence of the Na⁺,K⁺-ATPase in the fronto-parietal cortex of CCK₂ receptor-deficient (homo- and heterozygous) and normal (wild-type) mice. The Arrhenius plot for Na⁺,K⁺-ATPase from wild-type brain is non-linear with a breakpoint at 20.3 ± 0.4°C. In case of the brain cell membrane of CCK₂ receptor-deficient mice (homo- and heterozygous) the breakpoint on Arrhenius plot was detected at 26.0 ± 1.1°C and 25.4 ± 0.4°C, respectively. The shift of the breakpoint on the Arrhenius plot established in CCK₂ receptor-deficiency as well as in case of some other pathological conditions confirms that such kind of alteration in the Na⁺,K⁺-ATPase temperature dependence is likely related to the homeostatic adjustment of altered function of the sodium pump.     

Effects of acute temperature changes on the swimming abilities and oxygen consumption of Ptychobarbus kaznakovi from the Lancang River

Water temperature is known to be a particularly important environmental factor that affects fish swimming performance, but it is unknow how acute temperature changes affect the fish performance of Ptychobarbus kaznakovi. P. kaznakovi in the Lancang River have declined quickly in recent years, and this species was used to examine the effects of acute temperature changes on swimming abilities and oxygen consumption in a Brett‐type swimming tunnel respirometer. The standard metabolic rate (SMR) and routine metabolic rate (RMR) showed 216% and 134% increases, respectively, at 22°C (an acute increase from 17 to 22°C) compared to those at 12°C (an acute decrease from 17 to 12°C). Moreover, the RMR was approximately 1.7, 1.6 and 1.3 times the value of the SMR at 12°C, 17°C and 22°C, respectively. The critical swimming speed (U_crit) of P. kaznakovi at 22°C was 5.45 ± 0.45BL/S, which was 45% higher than that at 12°C (3.77 ± 0.92BL/S). The oxygen consumption rates (MO₂) reached their maximum values at swimming speeds near the U_crit for all the temperature treatments. The maximum metabolic rate (MMR) values at 12°C, 17°C and 22°C were 274.53 ± 142.60 (mgO₂ kg^?1 hr^?1), 412.85 ± 216.34 (mgO₂ kg^?1 hr^?1) and 1,095.73 ± 52.50 (mgO₂ kg^?1 hr^?1), respectively. Moreover, there was a narrow aerobic scope at 12°C compared to that at 17°C and 22°C. The effect of acute temperature changes on the swimming abilities and oxygen consumption of P. kaznakovi indicated that water temperature changes caused by dam construction could directly affect energy consumption during the upstream migration of fish.     

Temperature effects on oxygen thresholds for hypoxia in marine benthic organisms

The effect of warming on the oxygen requirements and the survival of benthic organisms under hypoxia was tested using a meta‐analysis of published results of experiments evaluating the effects of temperature on the median lethal time and median lethal concentration of benthic macrofauna under hypoxia. The meta‐analysis confirmed that survival times under hypoxia were reduced by on average 74% and that median lethal concentration increased by on average 16% when marine benthic organisms were exposed to warmer temperatures. Warming reduced survival times of marine benthic macrofauna under hypoxia by a median of 3.95±1.67 h °C^?1 and increased the oxygen thresholds for hypoxia‐driven mortality by a median of 1.02±0.15% saturation °C^?1 or 0.07±0.01 mg O₂ L^?1 °C^?1. The corresponding Q₁₀ values averaged 3.01±0.29 for the median survival time and 2.09±0.20 for the median lethal oxygen concentration. Use of these Q₁₀ values predicts that the 4 °C warming expected during the 21st century will lead to survival times 35.6% lower under hypoxia and that the threshold oxygen concentrations for high mortality to occur will increase by, on average, 25.5% if bottom water temperature increased by 4 °C. Hence, ocean warming is expected to increase the vulnerability of benthic macrofauna to reduced oxygen concentrations and expand the area of coastal ecosystems affected by hypoxia.     

Response of macrophyte litter decomposition in global blue carbon ecosystems to climate change

Blue carbon ecosystems (BCEs) are important nature-based solutions for climate change-mitigation. However, current debates question the reliability and contribution of BCEs under future climatic-scenarios. The answer to this question depends on ecosystem processes driving carbon-sequestration and -storage, such as primary production and decomposition, and their future rates. We performed a global meta-analysis on litter decomposition rate constants (k) in BCEs and predicted changes in carbon release from 309 studies. The relationships between k and climatic factors were examined by extracting remote-sensing data on air temperature, sea-surface temperature, and precipitation aligning to the decomposition time of each experiment. We constructed global numerical models of litter decomposition to forecast k and carbon release under different scenarios. The current k averages at 27 ± 3 × 10⁻² day⁻¹ for macroalgae were higher than for seagrasses (1.7 ± 0.2 × 10⁻² day⁻¹), mangroves (1.6 ± 0.1 × 10⁻² day⁻¹) and tidal marshes (5.9 ± 0.5 × 10⁻³ day⁻¹). Macrophyte k increased with both air temperature and precipitation in intertidal BCEs and with sea surface temperature for subtidal seagrasses. Above a temperature threshold for vascular plant litter at ~25°C and ~20°C for macroalgae, k drastically increased with increasing temperature. However, the direct effect of high temperatures on k are obscured by other factors in field experiments compared with laboratory experiments. We defined “fundamental” and “realized” temperature response to explain this effect. Based on relationships for realized temperature response, we predict that proportions of decomposed litter will increase by 0.9%–5% and 4.7%–28.8% by 2100 under low- (2°C) and high-warming conditions (4°C) compared to 2020, respectively. Net litter carbon sinks in BCEs will increase due to higher increase in litter C production than in decomposition by 2100 compared to 2020 under RCP 8.5. We highlight that BCEs will play an increasingly important role in future climate change-mitigation. Our findings can be leveraged for blue carbon accounting under future climate change scenarios.     

Understanding the early ontogenetic stages of Mugil liza (Mugilidae): Morphological traits and digestive/metabolic profile of pre-juveniles after recruitment

The family Mugilidae consists mainly of diadromous species, whose reproduction occurs in offshore waters. Pre-juveniles shift their diet in the surf zone (zooplanktophagous to iliophagous). Later, during their recruitment into estuaries, huge changes take place in their digestive system. However, digestive and metabolic characteristics and some morphological traits at recruitment are unknown for Mugilidae. We performed comparative studies on early and late pre-juveniles of Mugil liza recruited in Mar Chiquita Coastal Lagoon (37°32′–37°45′S, 57°19′–57°26′W, Argentina). We determined digestive enzyme activities (intestine), energy reserves (liver/muscle), total/standard length, total weight, intestinal coefficient, hepatosomatic index and retroperitoneal fat. Pre-juveniles exhibited amylase, maltase, sucrase, lipase, trypsin and aminopeptidase-N (APN) activities, which were maintained over a wide range of pH and temperature, and exhibited Michaelis–Menten kinetics. In late pre-juveniles, amylase (422 ± 131 μmol maltose min⁻¹ mgprot⁻¹), sucrase (86 ± 14 mg glucose min⁻¹ mgprot⁻¹), trypsin (84 ± 9 μmoles min⁻¹ mgprot⁻¹) and APN (0.58 ± 0.08 μmoles min⁻¹ mgprot⁻¹) activities were higher (42%, 28%, 35% and 28%, respectively) than in the early stage. Also, the intestinal coefficient was higher in late (3.04) compared to early (2.06) pre-juveniles. Moreover, the liver appeared to be a main site of glycogen and triglyceride storage in late pre-juveniles, muscle being the site of storage in early pre-juveniles, exhibiting higher glycogen, free glucose and protein concentrations (92%, 82%, 32%, respectively). The results suggest that pre-juveniles of M. liza exhibit an adequate digestive battery to perform complete hydrolysis of various dietary substrates, availability of energy reserves and morphological characteristics to support their feeding habit and growth after recruitment. Our results represent an important contribution to knowledge of the ecology and digestive physiology of pre-juveniles of Mugilidae in the wild.