Ambient Water Temperature Research Articles

Temperature modulates estrone degradation and biological effects of exposure in fathead minnows

Environmental pollutants, including estrogens, are widespread in aquatic environments frequently as a result of treated wastewater effluent discharged. Exposure to estrogens has been correlated with disruption of the normal physiological and reproductive function in aquatic organisms, which could impair the sustainability of exposed populations. However, assessing the effects of estrogen exposure on individuals is complicated by the fact that rates of chemical uptake and environmental degradation are temperature dependent. Because annual temperature regimes often coincide with critical periods of biological activity, temperature-dependent changes in estrogen degradation efficacy during wastewater treatment could modulate biological effects. We examined the interactions between ambient water temperature and degradation of estrone (E1) during wastewater treatment. In addition, we exposed mature fathead minnows (Pimephales promelas) to three environmentally relevant concentrations of E1 at four different water temperatures (15°C, 18°C, 21°C, and 24°C) to reflect natural seasonal variation. E1 degradation occurred with and without the support of robust nitrification at all temperatures; however, the onset of E1 degradation was delayed at cooler water temperatures. In addition, we observed significant interactive effects between temperature and E1 exposure. Female morphometric endpoints were more susceptible to temperature-modulating effects while physiological endpoints were more strongly affected in males. Collectively, the data demonstrate that natural seasonal fluctuations in temperature are sufficient to affect E1 degradation during wastewater treatment and induce sex-dependent physiological and anatomical changes in exposed fish.

The life and time of clams: Derivation of intra-annual growth rates from high-resolution oxygen isotope profiles

The paired analysis of subannual microincrements and serially-sampled oxygen isotope data affords insights into the physiological and environmental conditions controlling bivalve growth. However, daily microincrements are faint or absent in many taxa, difficult or ambiguous to count under the best conditions, and are often constrained to the earliest years of ontogeny, limiting the practicality of intra-annual comparisons between growth rate and environmental parameters. We present a computational approach to derive growth rates using only serially-sampled oxygen isotope data, thereby allowing for broader application of bivalve growth rate studies. Variation in the isotopic composition of shell carbonate along an ontogenetic sampling profile reflects temporal variation in ambient water temperatures, while variation in the position of isotope values in the distance domain reflects intra-annual variation in rates of shell accretion. Thus, the shape of the isotope profile in distance space over a given year records the concomitant influence of subannual variation in temperature (y-axis) and growth rate (x-axis). Presumption that annual variation in temperature is sinusoidal allows for the determination of an intra-annual growth rate function that best approximates observed δ18Ocarb data. The fidelity of the approach is affirmed using synthetically generated isotope datasets and previously published isotope profiles. The method offers a variety of applications to sclerochronologic studies. Using only oxygen isotope values determined along an ontogenetic trajectory, the approach can be used to quantify spatial and temporal patterns of intra-annual accretion within populations. Additionally, the model can be applied to long time series such that year-to-year variations in the growth profiles can be used to identify ontogenetic and climatic trends. While we focus here on isotope-distance records from bivalve shell carbonate, this method is equally applicable to similar data from other accretionary biogenic skeletal materials.

Solar desalination using solar still enhanced by external solar collector and PCM

In this work, an experimental study on water desalination using a solar still having phase change material (PCM) and connected to a solar collector was carried out. The PCM is used to store solar thermal energy collected by the system at daytime as latent heat, to provide heat during night time thus continuous operation. Water in the basin and the PCM were heated by direct solar radiation and by hot water flowing through a coil heat exchanger, fixed in the basin, heated by a solar collector. The produced water vapor from the basin condensed on the inner side of the water cooled double-glass cover. The condensate was withdrawn as fresh water. The effect of hot water circulation flow rate, cooling water flow rate, and basin water level on the amount of fresh water produced were studied. The production rate of desalinated water was proportional to the increase in ambient temperature and hot water circulation flow rate. There also is an optimum value of cooling water flowrate (about 10ml/s) at which the unit productivity was the highest. Additionally, as the water level in the basin increased the productivity decreased. The unit was capable of producing 4300ml/day·m2, of which about 40% was produced after sunset. The economic evaluation reveal that such units are feasible mainly in remote areas.

Reprint of: Dealing with dust – Some challenges and solutions for enabling solar energy in desert regions

In India, the desert regions of Rajasthan and Gujarat are preferred for installation of solar photovoltaic (PV) and concentrated solar thermal (CST) systems because of a high level of both DNI and GHI components of solar radiation. However, such regions pose substantial challenges in terms of dust, a high ambient temperature and scarcity of water. This paper is an attempt to address issues related to the deposition of dust (a) on a mirror with stand depicting PV panel or heliostat in the wake of a similar geometry and (b) in the porous absorber of an open volumetric air receiver (OVAR). A detailed insight to the wake-region behind an inclined flat-plate or heliostat is provided based on analysis and experiment. These indicate possible measures such as modification of the geometry of collectors to mitigate the problem of dust deposition. Also, the use of a cyclone separator with defined parameters based on a decision variable has been suggested for reliable operation of an OVAR. These problems being generic in nature, similar strategies are expected to be applicable in other desert regions subject to their specific conditions.

Modern planktic foraminifers in the high-latitude ocean

Abstract Planktic foraminifers can be sensitive indicators of the changing environment including both the Arctic Ocean and Southern Ocean. Due to variability in their ecology, biology, test characteristics, and fossil preservation in marine sediments, they serve as valuable archives in paleoceanography and climate geochemistry over the geologic time scale. Foraminifers are sensitive to, and can therefore provide proxy data on ambient water temperature, salinity, carbonate chemistry, and trophic conditions through shifts in assemblage (species) composition and the shell chemistry of individual specimens. Production and dissolution of the calcareous shell, as well as growth and remineralization of the cytoplasm, affect the carbonate counter pump and to a lesser extent the soft-tissue pump, at varying regional and temporal scales. Diversity of planktic foraminifers in polar waters is low in comparison to lower latitudes and is limited to three native species: Neogloboquadrina pachyderma, Turborotalita quinqueloba, and Globigerina bulloides, of which N. pachyderma is best adapted to polar conditions in the surface ocean. Neogloboquadrina pachyderma hibernates in brine channels in the lower layers of the Antarctic sea ice, a strategy that is presently undescribed in the Arctic. In open Antarctic and Arctic surface waters T. quinqueloba and G. bulloides increase in abundance at lower polar to subpolar latitudes and Globigerinita uvula, Turborotalita humilis, Globigerinita glutinata, Globorotalia inflata, and Globorotalia crassaformis complement the assemblages. Over the past two to three decades there has been a marked increase in the abundance of Orcadia riedeli and G. uvula in the subpolar and polar Indian Ocean, as well as in the northern North Atlantic. This paper presents a review of the knowledge of polar and subpolar planktic foraminifers. Particular emphasis is placed on the response of foraminifers to modern warming and ocean acidification at high latitudes and the implications for data interpretation in paleoceanography and paleoclimate research.

Optimum Temperatures for Net Primary Productivity of Three Tropical Seagrass Species.

Rising sea water temperature will play a significant role in responses of the world's seagrass meadows to climate change. In this study, we investigated seasonal and latitudinal variation (spanning more than 1,500 km) in seagrass productivity, and the optimum temperatures at which maximum photosynthesis and net productivity (for the leaf and the whole plant) occurs, for three seagrass species (Cymodocea serrulata, Halodule uninervis, and Zostera muelleri). To obtain whole plant net production, photosynthesis, and respiration rates of leaves and the root/rhizome complex were measured using oxygen-sensitive optodes in closed incubation chambers at temperatures ranging from 15 to 43°C. The temperature-dependence of photosynthesis and respiration was fitted to empirical models to obtain maximum metabolic rates and thermal optima. The thermal optimum (Topt) for gross photosynthesis of Z. muelleri, which is more commonly distributed in sub-tropical to temperate regions, was 31°C. The Topt for photosynthesis of the tropical species, H. uninervis and C. serrulata, was considerably higher (35°C on average). This suggests that seagrass species are adapted to water temperature within their distributional range; however, when comparing among latitudes and seasons, thermal optima within a species showed limited acclimation to ambient water temperature (Topt varied by 1°C in C. serrulata and 2°C in H. uninervis, and the variation did not follow changes in ambient water temperature). The Topt for gross photosynthesis were higher than Topt calculated from plant net productivity, which includes above- and below-ground respiration for Z. muelleri (24°C) and H. uninervis (33°C), but remained unchanged at 35°C in C. serrulata. Both estimated plant net productivity and Topt are sensitive to the proportion of below-ground biomass, highlighting the need for consideration of below- to above-ground biomass ratios when applying thermal optima to other meadows. The thermal optimum for plant net productivity was lower than ambient summer water temperature in Z. muelleri, indicating likely contemporary heat stress. In contrast, thermal optima of H. uninervis and C. serrulata exceeded ambient water temperature. This study found limited capacity to acclimate: thus the thermal optima can forewarn of both the present and future vulnerability to ocean warming during periods of elevated water temperature.

Processing freshly harvested banagrass to improve fuel qualities: Effects of operating parameters

Mechanical dewatering and leaching were used to process freshly harvested banagrass (Pennisetum purpureum X Pennisetum glaucum) and improve fuel properties relevant to thermochemical conversion. A factorial, 23 experiment determined the effects of process operating parameters: particle size (1 mm and 80 mm), rinse water temperature (25 °C and 75 °C), and rinse duration (1 min and 3 min). Characterization of the samples from the process included moisture and ash contents of solid samples, potassium (K) and chlorine (Cl) contents of solid and liquid samples, and chemical oxygen demand, total solids, and total suspended solids of liquid samples. These were used to assess the effectiveness of treatment on reducing K and Cl in the processed material, estimate material/energy losses associated with the processing, and identify further treatment requirements and opportunities for material recovery. The effects of particle size, rinse water temperature, and their interaction indicate that processing with low-grade hot water (75 °C) can improve K and Cl removal by over 10% compared to treatment using ambient temperature water for larger particles (80 mm). The former could result in reduced capital and operating costs for size reduction, as well as reduced material losses during processing.

In vitro study on the regulation of cellular mRNA levels by changes in transcription rate and transcript stability in fish red blood cells.

The interplay of transcriptional and post-transcriptional processes in the regulation of gene expression has been extensively studied in mammals but little is known in other vertebrates so far. Most non-mammalian vertebrates are faced with environmental cues and stressors distinct from those experienced by mammals and thus it is likely that the gene expression strategies differ from those of mammals. Here we performed experiments to study in vitro the various levels of gene expression regulation in nucleated fish red blood cells. Three critical environmental cues frequently experienced by fish were chosen: exposure to hypoxia (2.5%), ambient water temperature increase by 10°C (from 10°C to 20°C), and exposure to stress hormones (represented by the β-adrenergic agonist isoproterenol). We found that β-adrenergic stimulation increases the stability of the β3b-adrenergic receptor (β3b-ar) mRNA, suggesting that mRNA stability can play a role in the regulation of hormonal stress responses in fish. The β3b-ar gene encodes a unique β-adrenergic receptor subtype in fish red blood cells which controls the β-Na+/H+ exchanger activity - an important component of responses to oxygen limitations. Our results furthermore show a yet undescribed link between the Hif1a signaling pathway and the β-adrenergic receptor response. After β-adrenergic stimulation, the transcription of hif1a was activated significantly after 4 hours of exposure. So far, such a response has only been described from mammalian species. This indicates that the β-AR is fundamental to the molecular and physiological responses to hypoxia and that Hif1a might have additional functions than those already known.

Enhanced Recovery Process of Calcium Oxide and Metals from Steelmaking Slag with Net Carbon Sequestration

The iron and steel making (ISM) industry is one of the largest CO2 emitters in the world. Despite a sustained global research effort, utilization of best available technologies will not result in CO2 reductions for the industry that are sufficient to meet the Paris Climate Agreement. One area of the ISM process that still contains a large untapped potential for CO2 reduction is the recycling of slag. Currently ∼46% of ISM slag in Japan is used as an additive in cement production, reducing CO2 emissions. However, substantial grinding of slag is necessary prior to usage, which reduces the net CO2 offset of this process.We propose an alteration to current cooling methods in order to reduce the grinding energy of slag. Additionally, this new method recovers more low entropy metallic species than current processes. Molten slag is poured into shallow trays and allowed to settle in order to increase the separation of accidentally entrained metals from the calcium silicate melt. Upon reaching the solidification temperature the slag is cooled rapidly enough to induce the amorphous structure necessary to use slag as a cement additive. After solidification, the slag is quenched from high temperature in an ambient temperature water bath to create fractures throughout the slag due to high thermal stresses. These fractures reduce the subsequent grinding energy and liberate disparate species. This method results in a potential reduction of CO2 emissions for the Japanese ISM industry of ∼12.4 Mt/year; an increase of 3.0 and 2.1 times that of water-based and air-based cooling methods that include heat recovery, respectively. The process is validated by simulation and experimental results.

Assessment of the Water Quality of Saba River, Osogbo, Nigeria

The water quality and concentrations of selected heavy metals (cadmium, lead, and zinc) in Saba River, Osogbo were assessed monthly over a period of six months with a view to providing information on the water quality of the potentially polluted urban river system. Three sampling sites were selected along the Saba River (the upper reach of the river (Station A), mid-point of the river (Station B) and the lower reach of the river where it emptied into River Osun (Station C)). The recorded ambient air and water temperature, pH, alkalinity conductivity, total hardness, BOD and COD, as well as the phosphate and nitrate levels of Saba River, were within the maximum allowable regulatory limits of WHO (2011). The dissolved oxygen level between March and April in all the sampling points were in the limit of putting aquatic life under stress (<5.0 mg/L). Also the alkalinity level in station B between February and June, and in Station C from February till May were however above the maximum allowable desirable range of EPA (2001) and WHO (2011). The concentration of zinc, which ranged from 717 to 1,000 µg/L, was the highest amongst the selected metals assayed in the water. However, the mean concentration of lead in the water samples collected from Stations B and C (26 µg/L and 24 µg/L, respectively) was found to be above recommended regulatory acceptable limits of 20 µg/L of WHO (2011) and FEPA (2007). The study concluded that the physico-chemical indices of the water quality indicated that the river was mildly polluted.

First observations of temperature tolerances of adult male snow crab (Chionoecetes opilio) from the Barents Sea population and the effects on the fisheries strategy

ABSTRACTThis study investigates the effects of temperature on the survival, food intake, oxygen consumption and growth during long-term live holding of captive male snow crab (Chionoecetes opilio) (average = 0.7 kg). The crabs were held at three different temperatures, 3, 6 and 9°C. The trials were done using groups of snow crabs held in nine land-based holding tanks (three replicates per temperature treatment). The results showed that temperature had a significant effect on survival. The survival rate at 3°C (61%) was significantly higher than at 6°C (33%) and at 9°C (28%). Specific oxygen consumption rates of unfed crab at 6°C were significantly higher than at 9°C and 3°C. In summary, the current study shows that the Barents Sea snow crab have a narrow temperature range in which they thrive compared with the Barents Sea red king crab (Paralithodes camtschaticus). Barents Sea snow crab has similar metabolic and physiological attributes to other major snow crab populations. In conditions when ambient temperatures are approximately 6°C, it may prove beneficial for animal welfare and also be financially advantageous to reduce ambient water temperatures in live snow crab holding facilities on boat or on land.

Temperature dependence of δ18O in otolith of juvenile Japanese sardine: Laboratory rearing experiment with micro-scale analysis

We evaluated the use of the stable oxygen isotope (δ18O) in the otolith as a proxy for the temperature history of Japanese sardine Sardinops melanostictus individuals. Japanese sardine juveniles were reared in three different water temperatures over the course of a month. Otolith δ18O (δotolith) was analyzed by extracting the portions formed during the rearing period using a micromill. δ18O of the rearing water (δwater) was also analyzed. A linear relationship between otolith δ18O and ambient water temperature was identified as follows: δotolith−δwater=−0.18*T+2.69 (r2=0.91, p<0.01). This equation is different from that proposed for inorganic aragonite or other Sardinops spp., with resulting application to wild Japanese sardine captured in the Pacific Ocean showing that it estimates a more realistic in situ temperature. Our findings suggest that the Japanese sardine-specific isotopic fractionation equation should be used when interpreting otolith δ18O of the Japanese sardine, and the methods presented here could also be useful to understand the temperature history of other fish species.

Optimum connection modes for photovoltaic thermal collectors in different radiation zones of China

The connection mode of photovoltaic thermal (PVT) collectors is critical factor influencing the performance of PVT system. While determining optimum connection modes for PVT collectors in different radiation zones has not been previously reported in published literatures. In this study, a dynamic heat transfer model representing different connection modes for a PVT hot water system was developed, validated, and applied. By considering the ambient temperature, solar radiation, and heating load concurrently, the optimum connection mode in 10 different cities was determined based on an optimization index of realized combined electrical energy. The results indicated that the connection modes corresponding to the maximum realized combined electrical energy were N=2 and N=3 in radiation zone II and III, respectively, where N is the number of collectors in series. In Shantou, high ambient and main water temperatures contributed to a 40MJ increase in the realized combined electrical energy when the connection mode changed from N=3 to N=2. The results of this study provide good guidance for determining optimum connection modes for PVT hot water systems in different radiation zones.

Conceptualising the interactive effects of climate change and biological invasions on subarctic freshwater fish.

Climate change and species invasions represent key threats to global biodiversity. Subarctic freshwaters are sentinels for understanding both stressors because the effects of climate change are disproportionately strong at high latitudes and invasion of temperate species is prevalent. Here, we summarize the environmental effects of climate change and illustrate the ecological responses of freshwater fishes to these effects, spanning individual, population, community and ecosystem levels. Climate change is modifying hydrological cycles across atmospheric, terrestrial and aquatic components of subarctic ecosystems, causing increases in ambient water temperature and nutrient availability. These changes affect the individual behavior, habitat use, growth and metabolism, alter population spawning and recruitment dynamics, leading to changes in species abundance and distribution, modify food web structure, trophic interactions and energy flow within communities and change the sources, quantity and quality of energy and nutrients in ecosystems. Increases in temperature and its variability in aquatic environments underpin many ecological responses; however, altered hydrological regimes, increasing nutrient inputs and shortened ice cover are also important drivers of climate change effects and likely contribute to context‐dependent responses. Species invasions are a complex aspect of the ecology of climate change because the phenomena of invasion are both an effect and a driver of the ecological consequences of climate change. Using subarctic freshwaters as an example, we illustrate how climate change can alter three distinct aspects of species invasions: (1) the vulnerability of ecosystems to be invaded, (2) the potential for species to spread and invade new habitats, and (3) the subsequent ecological effects of invaders. We identify three fundamental knowledge gaps focused on the need to determine (1) how environmental and landscape characteristics influence the ecological impact of climate change, (2) the separate and combined effects of climate and non‐native invading species and (3) the underlying ecological processes or mechanisms responsible for changes in patterns of biodiversity.

Dealing with dust – Some challenges and solutions for enabling solar energy in desert regions

In India, the desert regions of Rajasthan and Gujarat are preferred for installation of solar photovoltaic (PV) and concentrated solar thermal (CST) systems because of a high level of both DNI and GHI components of solar radiation. However, such regions pose substantial challenges in terms of dust, a high ambient temperature and scarcity of water. This paper is an attempt to address issues related to the deposition of dust (a) on a mirror with stand depicting PV panel or heliostat in the wake of a similar geometry and (b) in the porous absorber of an open volumetric air receiver (OVAR). A detailed insight to the wake-region behind an inclined flat-plate or heliostat is provided based on analysis and experiment. These indicate possible measures such as modification of the geometry of collectors to mitigate the problem of dust deposition. Also, the use of a cyclone separator with defined parameters based on a decision variable has been suggested for reliable operation of an OVAR. These problems being generic in nature, similar strategies are expected to be applicable in other desert regions subject to their specific conditions.

Effects of long-term elevated temperature on covering, sheltering and righting behaviors of the sea urchin Strongylocentrotus intermedius.

Increases in ocean temperature due to climate change are predicted to change the behaviors of marine invertebrates. Altered behaviors of keystone ecosystem engineers such as echinoderms will have consequences for the fitness of individuals, which are expected to flow on to the local ecosystem. Relatively few studies have investigated the behavioral responses of echinoderms to long-term elevated temperature. We investigated the effects of exposure to long-term (∼31 weeks) elevated temperature (∼3 °C above the ambient water temperature) on covering, sheltering and righting behaviors of the sea urchin Strongylocentrotus intermedius. Long-term elevated temperature showed different effects on the three behaviors. It significantly decreased covering behavior, including both covering behavior reaction (time to first covering) and ability (number of covered sea urchins and number of shells used for covering). Conversely, exposure to long-term elevated temperature significantly increased sheltering behavior. Righting response in S. intermedius was not significantly different between temperature treatments. The results provide new information into behavioral responses of echinoderms to ocean warming.

Temperature increase and fluctuation induce phytoplankton biodiversity loss - Evidence from a multi-seasonal mesocosm experiment.

Global climate change scenarios predict lake water temperatures to increase up to 4°C and extreme weather events, including heat waves and large temperature fluctuations, to occur more frequently. Such changes may result in a reorganization of the plankton community structure, causing shifts in diversity and structure toward a community dominated by fewer species that are more adapted to endure warmer and irregular temperature conditions. We designed a long‐term (8 months) mesocosm experiment to explore how ambient water temperature (C: control), induced increased temperature (T: +4°C), and temperature fluctuations (F: ±4°C relative to T) change phytoplankton phenology, taxonomical diversity, and community structure, and how such changes affected zooplankton abundance and composition. Synthesis. Our results show that T and F relative to C significantly decreased phytoplankton diversity. Moreover, there was a clear effect of the temperature treatments (T and F) on phytoplankton size structure that resulted in a significantly lower growth of large species (i.e., large Chlorophyta) compared to C. Decreased diversity and evenness in the T and F treatments pushed the community toward the dominance of only a few phytoplankton taxa (mainly Cyanobacteria and Chlorophyta) that are better adapted to endure warmer and more irregular temperature conditions. The observed shift toward Cyanobacteria dominance may affect trophic energy transfer along the aquatic food web.

Population-specific genotype x genotype x environment interactions in bacterial disease of early life stages of Pacific oyster larvae.

The consequences of emerging marine diseases on the evolutionary trajectories of affected host populations in the marine realm are largely unexplored. Evolution in response to natural selection depends on the genetic variation of the traits under selection and the interaction of these traits with the environment (GxE). However, in the case of diseases, pathogen genotypes add another dimension to this interaction. Therefore, the study of disease resistance needs to be extended to the interaction of host genotype, pathogen genotype and environment (GxGxE). In this study, we used a full‐sib breeding design crossing two genetically differentiated populations of the Pacific oyster Crassostrea gigas (Thunberg, 1793), to determine the influence of host genotype, pathogen genotype and temperature on disease resistance. Based on a controlled infection experiment on two early life stages, that is, D‐larvae and Pediveliger larvae at elevated and ambient water temperatures, we estimated disease resistance to allopatric and sympatric Vibrio sp. by measuring survival and growth within and between genetically differentiated oyster populations. In both populations, survival was higher upon infection with sympatric Vibrio sp., indicating that disease resistance has a genetic basis and is dependent on host genotype. In addition, we observed a significant GxGxE effect in D‐larvae, where contrary to expectations, disease resistance was higher at warm than at cold temperatures. Using thermal reaction norms, we could further show that disease resistance is an environment dependent trait with high plasticity, which indicates the potential for a fast acclimatization to changing environmental conditions. These population‐specific reaction norms disappeared in hybrid crosses between both populations which demonstrates that admixture between genetically differentiated populations can influence GxGxE interactions on larger scales.

Life Table Analysis of Culex pipiens Under Simulated Weather Conditions In Egypt.

The effect of fluctuating ambient air and water temperatures and relative humidity (RH) on the population parameters of Culex pipiens was studied using life table data during the winter-spring and summer-autumn seasons in Giza Province, Egypt. In winter-spring (20.46 ± 1.8°C and 51.68 ± 3.63% RH), the preadult survival rate for Cx. pipiens was 80.65%, which was higher than the 50.00% observed in the summer-autumn (30.19 ± 0.67°C and 52.68 ± 8.04% RH). During the winter-spring period, the developmental time of egg, larvae, and pupae of Cx. pipiens was 3.52, 12.69, and 5.92 days, respectively. There was a significantly shorter developmental period for summer-autumn (1.0, 8.59, and 2.04 days, respectively). Both female and male adults survived longer during winter-spring (61.83 days for female and 42.62 days for male adults) than during summer-autumn (24.38 days for female and 20.83 days for male adults). The fecundity (F) of female Cx. pipiens (524.7 eggs/female) and the net reproductive rate (R0) (245.4 offspring) were significantly higher during winter-spring seasons than in the summer-autumn (163.3 eggs/female and 38.10 offspring). Despite the higher F and R0 values in winter-spring, the intrinsic rate of increase (rm = 0.1181/day) and the finite rate of increase (λ = 1.1253/day) of the Cx. pipiens population were significantly lower compared to summer-autumn (rm = 0.1648/day; λ = 1.1792/day). Consequently, the mean generation time during winter-spring was significantly longer (46.6 days) than during summer-autumn (22.09 days). The data suggest that Cx. pipiens is an r-strategist.

Influence of process parameters on the extraction of soluble substances from OFMSW and methane production

Microorganisms involved in anaerobic digestion require dissolved substrates to transport them through the cell wall to different processing units and finally to be disposed as waste, such as methane and carbon dioxide. In order to increase methane production, this work proposes to separate the soluble substances from OFMSW and analyse methane production from extracts and OFMSW. Using water as solvent, four extraction parameters were proposed: (1) Number of consecutive extractions, (2) Duration of mixing for every consecutive extraction, (3) OFMSW to water mass ratios 1:1, 1:2, and 1:3 and, (4) The influence of temperature on the extraction process. Results indicated that is possible to separate 40% of VS from OFMSW with only three consecutive extraction with mixing of 30min in every extraction using ambient temperature water. For every OFMSW to water combination, the first three consecutive extracts were analysed for biochemical methane potential test during 21days at 35°C; OFMSW was also tested as reference. Methane production from all substrates is highest during the first day and then it slowly decreases to increase again during a second stage. This was identified as diauxic behaviour. Specific methane production at day 21 increased with increasing water content of the extracts where OFMSW methane production was the lowest of all with 535NL/kgVS. These results indicate that it is feasible to rapidly produce methane from extracted substances.