Decrease In Water Temperature Research Articles

저온 폐열 활용을 위한 2중 효용 2단 흡수식 히트펌프 시뮬레이션

막대한 산업용 에너지가 폐열로 버려지는 상황에서 폐열, 특히 저온 폐열의 효과적인 이용은 매우 중요하다. 본 연구에서는 $160^{\circ}C$ 의 고온 열원과 $17^{\circ}C$ 저온 하수열을 사용하여 $50^{\circ}C$ 의 온수를 $70^{\circ}C$ 로 승온시키며 성적계수는 1.6을 만족하는 2중 효용 2단 흡수식 히트펌프 사...

Effects of temperature change on physiological and biochemical responses of Yesso scallop, Patinopecten yessoensis

Water temperature can be a significant environmental stressor that affects the physiological and biochemical responses of mollusks. Yesso scallop, Patinopecten yessoensis, is influenced by water temperature fluctuations caused by the Northern Yellow Sea Cold Water Mass. Here, the effects of acute seawater temperature change, gradual temperature change, and fluctuating temperature on the physiological and enzymatic activities in Yesso scallop were studied. Scallops were transferred directly from rearing temperature (15°C) to 5, 10, or 20°C for the acute water temperature change treatment. Scallops in the gradual water temperature change treatment were acclimated to different temperatures (5, 10, and 20°C) by increasing or decreasing seawater temperature progressively (1–2°C/day). The results showed that oxygen consumption and ammonia-N excretion rates in the 20°C-acute water temperature change treatment were significantly higher than those in the gradual treatment (one-way ANOVA, P<0.01). However, scallop ingestion rate decreased significantly in response to an acute water temperature decrease from 15 to 5°C, compared with equivalent groups exposed to a gradual temperature drop (one-way ANOVA, P<0.01). Moreover, hepatopancreatic superoxide dismutase (SOD), catalase (CAT), acid phosphatase (ACP), and lysozyme (LSZ) activities reached their highest levels in the 20°C-acute treatment after 12h. Malondialdehyde (MDA) content increased significantly following the acute water temperature changes and reached the highest level in 10°C-acute treatment after 72h. Heat shock protein70 gene (Hsp70) expression levels also increased significantly when water temperature was increased rapidly from 15 to 20°C or decreased rapidly from 15 to 10°C (P<0.01). In the fluctuation treatment, seawater temperature was altered every 12h for a total of six fluctuations. Scallops were transferred directly from 15 to 7°C (first fluctuation), moved from 7 to 15°C for the next 12h (second fluctuation), and then transferred from 15 to 7°C again (third fluctuation) and so on. As results, significant increases in SOD and CAT activities and MDA content, and decreases in ACP and LSZ activities were observed (one-way ANOVA, P<0.01). Significantly upregulated Hsp70 expression was also found in hemocytes, gills, and the adductor muscle of scallops in the fluctuating temperature treatment (one-way ANOVA, P<0.01). In conclusion, acute water temperature changes and fluctuations impacted the physiological and enzymatic activities of Yesso scallops and upregulated Hsp70 expression.

NEW APPARATUS TO RAISE THE PERFORMANCE OF ENGINE COOLING WATER CYCLE

Internal combustion engines consider as a power source of all machines in agricultural operations. To obtain the optimum performance of these engines there temperature must be maintained at the optimum level. To achieve the previous aim, the engine cooling system must be responsible for the absorption of excess heat from the engines particularly in hot regions. Therefore, this study was conducted in order to solve a problem of failure engine water cooling cycle in warm areas by appending an additional unit to the engine cooling water circuit consisting of an additional thermally insulated tank of water cooled by two pieces of peltier sheets and electric cooling fans. When engine temperature rise above the allowed level, the cooling water path throw the assistant cooling apparatus (peltier cooling unit) to maintain the engine temperature at the ideal level. Four main parameters were taken in this study, five levels of electric current intensity CI (1, 2, 3, 4 and 5 Ampere), four levels of water flow rate FR (0.5, 1, 1.5 and 2 liter/min.), four levels of temperature of inlet water WT (75o, 80o, 85o and 90oC), and two types of flow water FT (free flow and in serpentine). Absorbed heat energy Q=kJ/min was calculated at different levels of studied parameters under study. The obtained results showed that, the peltier sheets with second type of flow water (in serpentine) gained an effective decrease in water temperature, this condition decreased with the increase of inlet water temperature WT above 85oC. The highest value of absorbed heat energy Q =502.2 kJ/min was gained with (CI5 = 5 amp.), (FR4 = 2 lit/min.) and (WT1 = 75o) at serpentine type of flow water rate (FT1).

Preliminary water flow monitoring of a vertical fractures system in a sandstone rock mass

Fractured sandstone by tectonic and gravity actions could be classified as aquitard or aquifer according to the number and aperture of the fractures inside the rock mass. This kind of rock mass outcrops not frequently and sparsely in the Apennine and Alps chains. In the Emilian Apennines, which is mainly composed by sedimentary rocks (rich in clay), this type of rock is part of the Epiligurian Succession that outcrops for a 20% of the chain. The aim of the paper is to highlight the first results of the semi-continuous water flow monitoring (discharge, electrical conductivity and temperature) of the spring that represents the drainage point of a vertical fractures system. This network joint characterizes the vertical scarp of a sandstone slab with thickness of 100 meters. The results shows that the spring flow rate, the water electrical conductivity and temperature are influenced by the rainfall distribution pattern. Consequently every rainfall event the spring discharge and water electrical conductivity increase, while the water temperature decreases. The new infiltrate water reacts the spring with a delay of 10-60 hours. The discharge variability index is around 270%. The fractured system is characterized by replacement effect of the preexistent groundwater. During the infiltration event, dissolution phenomena are observed along the wall of the fractures. A preliminary groundwater budget calculation highlights that only a potential infiltration coefficient higher that 75% is admitted to justify the total annual volume discharge from the fractures.

Effect of Temperature on Biochemical Composition, Growth and Reproduction of the Ornamental Red Cherry Shrimp Neocaridina heteropoda heteropoda (Decapoda, Caridea)

The effect of water temperature on biochemical composition, growth and reproduction of the ornamental shrimp, Neocaridina heteropoda heteropoda, was investigated to determine the optimum temperature for its culture. The effect of embryo incubation temperature on the subsequent performance of juveniles was also evaluated. Ovigerous females and recently hatched juveniles (JI) were maintained during egg incubation and for a 90-day period, respectively, at three temperatures (24, 28 and 32°C). Incubation period increased with decreasing water temperature, but the number and size of JI were similar among treatments. At day 30 of the 90-day period, body weight and growth increment (GI) at 24°C were lower than those at 28 and 32°C. On subsequent days, GI at 24°C exceeded that at 28 and 32°C, leading to a similar body weight among treatments. These results suggest growth was delayed at 24°C, but only for 30 days after hatching. The lipid concentration tended to be lowest, intermediate and highest at 28, 32 and 24°C, respectively, possibly as a consequence of the metabolic processes involved in growth and ovarian maturation. Protein and glycogen concentrations were similar among treatments. Both the growth trajectory and biochemical composition of shrimps were affected by the temperature experienced during the 90-day growth period independently of the embryo incubation temperature. During the growth period, shrimps reached sexual maturity and mated, with the highest proportion of ovigerous females occurring at 28°C. All the females that matured and mated at 32°C lost their eggs, indicating a potentially stressful effect of high temperature on ovarian maturation. Based on high survival and good growth performance of shrimps at the three temperatures tested over the 90-day period it is concluded that N. heteropoda heteropoda is tolerant to a wide range of water temperatures, with 28°C being the optimum temperature for its culture.

Effects of seasonal seston and temperature changes on lake zooplankton fatty acids

We investigated how seston fatty acids (FA) and water temperature explained seasonal variation in cladoceran and copepod FA over three years in pre-alpine, oligotrophic Lake Lunz, Austria. Using the mostly algal-derived polyunsaturated FA (PUFA: arachidonic, ARA; eicosapentaenoic, EPA; docosahexaenoic acid, DHA), terrestrial FA (TFA, 22 : 0, 24 : 0), and bacterial FA (BAFA, 15 : 0, 17 : 0 and their branched homologues) as source-specific biomarkers, we show that cladocerans consistently contained more ARA and EPA and copepods more DHA than the available food (seston). None of these physiologically important PUFA were significantly related between zooplankton and seston across the entire study period but copepod DHA increased with seston DHA during the coldest months (< 8°C, based on a significant seston FA*temperature interaction). EPA, conversely, increased with decreasing water temperature in both zooplankton groups. For the nonessential FA, TFA were lower in zooplankton than in seston and not related to dietary supply or water temperature. However, cladoceran and copepod BAFA increased significantly with increasing seston BAFA and decreasing water temperature. These findings suggest that physiological regulation in response to changing water temperature had a significant impact on cladoceran and copepod EPA and the extent of dietary tracking for copepod DHA. TFA available in the seston may not have been consumed or were poorly incorporated by zooplankton, but BAFA were good indicators of available resources throughout multiple seasonal cycles. Based on our study, both FA type and water temperature impact the extent that dietary vs. nondietary processes govern cladoceran and copepod FA in oligotrophic lakes.

Hiatus in global warming - example of water temperature of the Danube River at Bogojevo gauge (Serbia)

The research included trends in water temperature of the Danube River at Bogojevo gauge and surface air temperature at the nearby meteorological station Sombor, as well as an analysis of the results obtained in relation to the claims of the existence of the hiatus in global air temperature increase in the period 1998-2012. In the period 1961-2013, there was a statistically significant increase in the mean annual water temperature (0.039?C/year), as well as all the average monthly values. However, with annual values for the period 1998-2013, there was a decrease. The longest periods of negative trend (27 years) were recorded for January and February. A high correlation was found between the surface air temperature and water temperature for all monthly and seasonal values. In the mean annual air temperature the presence of the hiatus is not observed, but a negative trend is recorded in March (32 years), December (43 years) and February (49 years). The highest correlations between water temperature and North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and Atlantic Multidecadal Oscillation (AMO) were obtained for the NAO in January (0.60), the AMO in autumn (0.52) and the NAO in winter (0.51). For surface air temperature, the highest correlations were registered for the AMO in summer (0.49) and the NAO in winter (0.42). The results indicate the dominant role of natural factors in the decrease of winter air temperature and water temperature of the Danube.

Mechanisms of trichloramine removal with activated carbon: Stoichiometric analysis with isotopically labeled trichloramine and theoretical analysis with a diffusion-reaction model

This study investigated the mechanism by which activated carbon removes trichloramine, a byproduct of water treatment that has a strongly offensive chlorinous odor. A stoichiometrical mass balance for 15N before and after activated carbon treatment of laboratory-prepared 15N-labeled trichloramine solutions clearly revealed that the mechanism of trichloramine removal with activated carbon was not adsorption but rather reductive decomposition to nitrogen gas. There was a weak positive correlation between the surface decomposition rate constant of trichloramine and the concentration of basic functional groups on the surface of the carbon particles, the suggestion being that the trichloramine may have been reduced by sulfhydryl groups (–SH) on the activated carbon surface. Efficient decomposition of trichloramine was achieved with super powdered activated carbon (SPAC), which was prepared by pulverization of commercially available PAC into very fine particles less than 1 μm in diameter. SPAC could decompose trichloramine selectively, even when trichloramine and free chlorine were present simultaneously in water, the indication being that the strong disinfection capability of residual free chlorine could be retained even after trichloramine was effectively decomposed. The residual ratio of trichloramine after carbon contact increased somewhat at low water temperatures of 1–5 °C. At these low temperatures, biological treatment, the traditional method for control of a major trichloramine precursor (ammonium nitrogen), is inefficient. Even at these low temperatures, SPAC could reduce the trichloramine concentration to an acceptable level. A theoretical analysis with a diffusion-reaction model developed in the present study revealed that the increase in the trichloramine residual with decreasing water temperature was attributable to the temperature dependence of the rate of the reductive reaction rather than to the temperature dependence of the diffusive mass transfer rate.

A Comparative Study of the Health Status of Tilapia Fish Through Various Environmental Changes

A number of 360 apparently healthy and naturally infected Nile tilapia with body weight range (40-80) grams were obtained from Abassa fish farms, Sharkia Governorate, Egypt, random collected from pond with uncovered cement ponds (A) and greenhouse cement ponds (B) (180 from each) during winter season of 2013 /2014 ( December and January). Water parameters were recorded at the collection time namely temperature, ammonia and dissolved oxygen. At the present work tilapia fish were subjected to clinical and post mortem examination. All Fish were examined for isolation and identification of bacterial, mycotic and parasitic pathogens and histopathological examinations were performed on infected fish tissue. The isolated bacteria were Pseudomonas aeruginosa , Pseudomonas fluorescens , Proteus vulgaris , Escherichia coli , Enterobacter intermedius , Enterobacter aerogenes , Enterobacter cloacae and Aeromonas hydrophila . The bacterial prevalence was higher in pond B (57.8%) than in pond A (33.3%). Mycological examination revealed that fungal isolation of four genera were isolated from pond (A) ( Penicillium spp, Aspergillus niger , Blastomyces spp and Scopulariopsis brevicaulis ) but in pond (B) were positive to fiver genera ( Penicillium spp, Aspergillus niger , Blastomyces spp and Scopulariopsis brevicaulis ). The fungal isolates were higher in pond (B) 77.8% than in pond (A) 55.6%. The examination of tilapia fish revealed the presence of four different parasitic agents which were identified, as Myxobolus tilapiae , Trichodina heterodentata and two encysted metacercariae (EMC) Centrocestus formosanus in gills and Heterophyes sp in muscles .The parasitic agents was higher in pond (B) 77.8% than in pond 55.6%(A). The results of the histopathological examination of naturally infected fish were also discussed. It was concluded that it be good to using greenhouse in fish culture to avoid the decrease in water temperature during winter season but other factors must be taken in consideration like water sources to avoid spread of diseases.

Longitudinal study of winter mortality disease in Sydney rock oysters Saccostrea glomerata.

Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa-B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.

A high-elevation MIS 5 hydrologic record using mollusks and ostracodes from Snowmass Village, Colorado, USA

Sediments containing terrestrial and aquatic mollusks and ostracodes from the Ziegler Reservoir fossil site (2705m elevation) near Snowmass Village, Colorado, span ~130–87ka (MIS 5e through 5b). The southeastern area of the site where taxa were recovered was a relatively fresh, shallow, well-vegetated wetland during MIS 5e through 5c time, approximately 2m deep, with a total dissolved solids value of ~200–1000mgL−1. The wetland was seasonally or annually variable and groundwater discharged along the margins of the bounding moraine. Groundwater likely contributed solutes to the system and may have contributed 18O-enriched water. Based on stable isotopes from ostracode calcite (δ18OOST and δ13COST), seasonal evaporation occurred and the dissolved inorganic carbon pool was unexpectedly enriched in 13C. The mollusk and ostracode faunas changed little across the MIS 5e/5d/5c boundaries, whereas a distinct change in the ostracode fauna occurred between the deposition of Unit 11 and Unit 13, which corresponds in time to the MIS 5c/5b boundary, indicating some combination of increased surface and/or groundwater flow, a decrease in water temperature, and a freshening and a possible deepening of the wetland.

Asynchronous responses of fish assemblages to climate-driven ocean regime shifts between the upper and deep layer in the Ulleung basin of the East Sea from 1986 to 2010

Past studies suggested that a basin-wide regime shift occurred in 1988–1989, impacting marine ecosystem and fish assemblages in the western North Pacific. However, the detailed mechanisms involved in this phenomenon are still yet unclear. In the Ulleung basin of the East Sea, filefish, anchovy and sardine dominated the commercial fish catches in 1986–1992, but thereafter common squid comprised > 60% of the total catch in 1993–2010. To illuminate the mechanisms causing this dramatic shift in dominant fisheries species, I related changes in depth-specific oceanographic conditions from 0 to 500 m to inter-annual changes in the fish assemblage structure from 1986 to 2010. In the upper layer of 50–100 m depths, water temperature suddenly increased in 1987–1989, and consequently warm-water epi-pelagic species (anchovy, chub mackerel, and common squid) became dominant, while sardine, relatively cold-water epi-pelagic species, nearly disappeared. An annual index of the volume transport by the Korea Strait Bottom Cold Water, originating from the deep water of the Ulleung Basin, displayed a sudden intensification in 1992–1993, accompanied by decreased water temperature and increased water density in the deep water and replacement of dominant bentho-pelagic species from filefish, warm-water species, to herring and cod, cold-water species. The results suggest that climate-driven oceanic changes and the subsequent ecological impacts can occur asynchronously, often with time lags of several years, between the upper and the deep layer, and between epi-pelagic and deepwater fish assemblages.

Vibrio coralliilyticus Strain OCN008 Is an Etiological Agent of Acute Montipora White Syndrome

Identification of a pathogen is a critical first step in the epidemiology and subsequent management of a disease. A limited number of pathogens have been identified for diseases contributing to the global decline of coral populations. Here we describe Vibrio coralliilyticus strain OCN008, which induces acute Montipora white syndrome (aMWS), a tissue loss disease responsible for substantial mortality of the coral Montipora capitata in Kāne'ohe Bay, Hawai'i. OCN008 was grown in pure culture, recreated signs of disease in experimentally infected corals, and could be recovered after infection. In addition, strains similar to OCN008 were isolated from diseased coral from the field but not from healthy M. capitata. OCN008 repeatedly induced the loss of healthy M. capitata tissue from fragments under laboratory conditions with a minimum infectious dose of between 10(7) and 10(8) CFU/ml of water. In contrast, Porites compressa was not infected by OCN008, indicating the host specificity of the pathogen. A decrease in water temperature from 27 to 23°C affected the time to disease onset, but the risk of infection was not significantly reduced. Temperature-dependent bleaching, which has been observed with the V. coralliilyticus type strain BAA-450, was not observed during infection with OCN008. A comparison of the OCN008 genome to the genomes of pathogenic V. coralliilyticus strains BAA-450 and P1 revealed similar virulence-associated genes and quorum-sensing systems. Despite this genetic similarity, infections of M. capitata by OCN008 do not follow the paradigm for V. coralliilyticus infections established by the type strain.

Food consumption and digestive enzyme activity ofClarias batrachusexposed to various temperatures

The effect of temperature on the food consumption rate and the digestive enzyme activities of Clarias batrachus (80.60 ± 5.34 g) were evaluated. Fish were exposed to six different temperatures of 10, 15, 20, 25, 30 and 35 °C following an acclimation temperature of 25 °C. The rate of temperature change was 2 °C day−1. Highest food consumption was recorded at 25 °C. It gradually reduced with decreasing water temperature. Food consumption rate was significantly (P < 0.05) lower at 10 °C compared with other treatments. Hence, 46.67, 8.20–23.58 and 1.02–6.15% reduced food consumptions were recorded in groups exposed at 10, 15 and 20 °C temperatures, respectively, compared with the 25 °C. The consumption rate was not affected in fish exposed at 30 and 35 °C. Total protease, trypsin and chymotrypsin activities were significantly (P < 0.05) higher in fish exposed at 25 °C compared with others. Lipase activity was significantly (P < 0.05) higher in fish exposed at 30 °C compared with others. Lowest enzyme activities were recorded at 10 °C. Water temperature below 25 °C affected the food consumption and digestive enzyme activities in fish that served as indicators of stress in fish.

Response of dissolved oxygen and related marine ecological parameters to a tropical cyclone in the South China Sea

It is well known that tropical cyclones can cause upwelling, decrease of sea surface temperature, increase of chlorophyll-a (Chl-a) concentration and enhancement of primary production. But little is known about the response of dissolved oxygen (DO) concentration to a typhoon in the open ocean. This paper investigates the impact of a typhoon on DO concentration and related ecological parameters using in situ and remote sensing data. The in situ data were collected 1week after the passage of the super-typhoon Nanmadol in the northern South China Sea in 2011. An increase in DO concentration, accompanied by a decrease in water temperature and an increase in salinity and Chl-a concentration, was measured at sampling stations close to the typhoon track. At these stations, maximum DO concentration was found at a depth of around 5m and maximum Chl-a concentration at depths between 50 and 75m. The layer of high DO concentration extends from the surface to a depth of 35m and the concentrations stay almost constant down to this depth. Due to the passage of the typhoon, also a large sea level anomaly (21.6cm) and a high value of Ekman pumping velocity (4.0×10−4ms−1) are observed, indicating upwelling phenomenon. At the same time, also intrusion of Kuroshio waters in the form of a loop current into the South China Sea (SCS) was observed. We attribute the increase of DO concentration after the passage of the typhoon to three effects: (1) entrainment of oxygen from the air into the upper water layer and strong vertical mixing of the water body due to the typhoon winds, (2) upwelling of cold nutrient-rich water which stimulates photosynthesis of phytoplankton and thus the generation of oxygen, which also increases the DO concentration due to cold water since the solubility of oxygen increase with decreasing water temperature, and, possibly, (3) transport of DO enriched waters from the Western Pacific to the SCS via the intrusion of Kuroshio waters.

Spatio-temporal attributes of water temperature and macroinvertebrate assemblages in the headwaters of the Bushmans River, southern Drakensberg

Currently, there is little understanding of the controls that instream thermal limits and hydraulic biotype diversity have on macroinvertebrate assemblages, particularly in association with changing altitude within given southern African mountain drainage systems. Thus, the aim of this research was to examine aquatic macroinvertebrate assemblage changes in response to spatial and temporal geo-hydrological contexts (temperature and hydraulic biotype) along the upper Bushmans River, southern Drakensberg. Instream temperature was continuously logged at 3 altitudes (1 760, 2 030, 2 280 m amsl) along the Bushmans River to the east of the Great Escarpment, and in the headwaters of the Sani River (2 860 m amsl) to the west of the escarpment, for the period January–May 2007. Aquatic macroinvertebrates were sampled during early December 2006, late March 2007, and late May 2007. The study demonstrates that decreasing water temperatures, both spatially (with increasing altitude) and seasonally (from summer to winter), and/or decreasing diversity of hydraulic biotypes associated with stream-channel narrowing in Drakensberg rivers/streams, are associated with a general decrease in the absolute number of macroinvertebrate families, a lower dissimilarity coefficient along the Bushmans River altitudinal transect, and a decreasing variance in the numbers of macroinvertebrate families across various hydraulic biotypes.Keywords: Aquatic macroinvertebrates, water temperature, hydraulic biotypes, Drakensberg

Impact of barrages on downstream air entrained in water and on upstream river water quality

This research studies the effect of barrages on upstream river water quality and on its self-assimilative. Also, the impact of barrages on upstream water temperature profile is studied. The amount of entrained air in water at river downstream side as a result of barrage existence is also studied. Constructing barrages in river reaches will alter its hydraulics and thus its water quality and thermal regime. A mathematical model is developed to simulate river hydraulics, water quality parameters and temperature. A case study of a Nile River reach in Egypt was studied, to investigate the impact of the existence of Esna barrage on water quality and temperature at its upstream side. Barrages were found to have negative impacts on upstream self-assimilative capacity of rivers. On the other hand, they have positive impacts on DO concentrations and air entrained at the downstream side. Finally, barrages cause a slight decrease in water temperature.

Development ofTrachelomonasspecies (Euglenophyta) during blooming ofPlanktothrix agardhii(Cyanoprokaryota)

This paper reports data on a community of Trachelomonas species (Euglenophyta) occurring during Planktothrix agardhii bloom formation in a shallow, highly eutrophic dam reservoir. The results come from a long-term study of Siemianowka Dam Reservoir, located on the upper Narew River (NE Poland). From April to October 2007, 132 alga taxa were identified, including 32 Trachelomonas taxa, 23 of which are new for the reservoir; of those, three are first records for Poland: T. armata (Ehrenberg) Stein var. heterospina Swirenko, T. atomaria Skvortzov var. minor Hortobagi and T. minima Drez uepolski. One variety, T. curta var. pappilata Wooowski, is described as new for science. The ultrastructural details of Trachelomonas species are illustrated. The highest number of Trachelomonas taxa was recorded in August in the shore zone of the re- servoir. At the end of summer 2007, the conspicuous development of P. agardhii (Gomont) Anagnostidis et Komarek, caused a rapid decrease of Trachelomonas biomass due to lower water transparency and the oxygen concentration. In addition, a decline in the Trachelomonas taxa and biomass was associated with a decrease of water temperature. The negative impact of extracellular microcystin on the Trachelomonas development requires further study.

Influence of temperature during four following spawning seasons on the spawning effectiveness of common bream, Abramis brama (L.) under natural and controlled conditions

The common bream, Abramis brama (L.) in Kortowskie Lake (north-eastern Poland) usually spawn when the water temperature during the late spring rises to 20°C. The optimal water temperature for embryonic development of this population is 21°C. However, in some cases, the temperatures of the spawning grounds during bream spawning are much higher, becoming semi-lethal or even lethal for bream embryos. The aim of the study was to investigate the natural and artificial spawning effectiveness of bream during a 4-year study regarding the reproductive effectiveness of the wild bream population in relation to thermal fluctuation (optimal and semi-lethal) of their ecosystem during the natural spawning season. During four following seasons, the bream spawners, as well as the eggs, were collected from the spawning grounds and incubated at optimal (21°C) and semi-lethal (23°C) temperatures. The spawning of mature bream was artificially induced and the obtained eggs were also incubated at the same temperatures. The period of observed spawners on the spawning grounds was different in different years: the longest time of bream spawning was in the second year of the study and the shortest was during the third year of the study. In the last year, a decrease in water temperature caused a break in the spawning. Thermal changes in water temperature during the spawning season may have caused a high mortality level of bream embryos and decreased the recruitment of the next species generation.

Effect of temperature decrease on hemocyte apoptosis of the white shrimp Litopenaeus vannamei

This study investigated the effect of continuous temperature decrease on hemocyte apoptosis of the white shrimp Litopenaeus vannamei. In the stress group, water temperature decreased from 26 to 17 °C at a rate of 1 °C/h. Shrimp kept at 26 ± 0.5 °C were used as control group. Total hemocyte count (THC), reactive oxygen species (ROS) production, cytoplasmic free-Ca2+ (CF-Ca2+) concentration, mitochondrial membrane potential (MMP), apoptotic cell ratio, and caspase-3 activity of L. vannamei hemocytes were determined when water temperature decreased to 23, 20, and 17 °C, respectively. Increased ROS production in hemocytes was observed when water temperature decreased to 20 and 17 °C. Decreased THC and cellular MMP, increased CF-Ca2+ concentration, apoptotic cell ratio, and caspase-3 activity were shown when water temperature decreased to 17 °C. These results indicate that water temperature decrease can induce oxidative stress on shrimp hemocytes and then cause mitochondria and caspase-3 mediated hemocyte apoptosis and THC reduction, when water temperature decreased to an unconformable level.