Effect Of Low Water Temperature Research Articles

Experimental analysis of the effect of low water temperature on oogenesis of juvenile chum salmon

The state of gonads is examined for juvenile chum salmon exposed for two weeks at low water temperature, for different stages of their embryonic-larval development. The transfer of the embryos and larvae from the water with temperature of 10.0–12.0 о C to the water with temperature of 1.3–1.8 о C slowed both somatic growth of the fish and development of their germ cells in all cases. The deficit in body weight and ovarian weight of experimental fish was not compensated later. However, the gonad weight was decreased in the somatic component and did not affect the fund of germ cells, in the medium term. The state of ovaries did not differ between the control and experimental groups of fish 50 days after the end of exposure, regardless of the initial condition of gonads in the experiment.

Effects of different regimes of low temperature on egg hatching of Dactylogyrus vastator (Monogenea: Dactylogyridae)

The development of dactylogyrids is dependent on water temperature, and their eggs fail to hatch below 5 °C. In the field, however, mean abundance of Dactylogyrus species increases and reaches a high level in winter, which suggests that infective oncomiracidia hatch from eggs in winter. Therefore, the effect of low water temperature on in vitro egg hatching of D. vastator was determined in laboratory. D. vastator hatching success was 65.3%, 62.7%, 42.6% and 22.3% when eggs were firstly incubated for 0, 7, 14 and 21 days at 5 °C and then consecutively maintained for 15 days at 20 °C. When eggs were directly incubated at 5 °C, eggs failed to hatch within one month. However, hatching success was 69.8% and 66.7%, respectively, when maintained at 5 °C after 12 and 24 h incubation at 20 °C. The results suggested that egg incubation for more than 1 week at 5 °C had significant impacts on hatching success of D. vastator subsequently maintained at 20 °C. But low temperature (5 °C) had no effect on hatching success when eggs were firstly exposed to room temperature (20 °C) for one day.

Responses in shoot elongation, carbohydrate utilization and growth recovery of an invasive species to submergence at different water temperatures

Widely distributed amphibious exotic plant species may respond plastically to water temperatures when submerged. Alternanthera philoxeroides, a highly flood-tolerant species, originates from tropical regions and has successfully invaded temperate regions. The wide distribution of this species suggests it can respond to flooding at different water temperatures. In this study, the plastic responses of A. philoxeroides plants to submergence at water temperatures of 10 °C, 20 °C and 30 °C were investigated. The A. philoxeroides plants had large pools of non-structural carbohydrates, which were readily mobilized upon submergence. Submergence hindered biomass accumulation and decreased the carbohydrate content level and respiration rate (P < 0.05). Water temperature had remarkable effects on shoot elongation, carbohydrate utilization and recovery growth. With decreasing water temperature, the respiration rate was lower and carbohydrate content decreased more slowly, but the post-submergence biomass accumulation was faster (P < 0.05), indicating a beneficial effect of low water temperature for recovery. However, high water temperatures accelerated shoot elongation (P < 0.05), which benefitted the submerged plants more if contact with air was restored. These results suggest that the species can respond to different water temperatures plastically, which may provide hints for its invasion success in regions with diverse climates.

Fatty acid composition in the white muscle of Cottoidei fishes of Lake Baikal reflects their habitat depth

Lake Baikal is a unique freshwater environment with maximum depths over 1600 m. The high water pressure at the lakebed strengthens the solidifying effect of low water temperature on animal tissue lipids, and thus the effective temperatures in the depths of the lake equal subzero temperatures in shallow waters. Cottoidei species has colonized the different water layers of the lake, and developed different ecology and physiology reflected in their tissue biochemistry. We studied by gas chromatography the composition of fatty acids (FAs), largely responsible for tissue lipid physical properties, in the white muscle tissue of 13 species of the Cottoidei fish; five benthic abyssal, six benthic eurybathic and two benthopelagic species. The FA profiles reflected habitat depth. The muscles of the deepest living species contained little polyunsaturated FAs (PUFAs) and were instead rich in monounsaturated FAs (MUFAs), which may be due to occasional weak food web links to the PUFA-rich primary producers of the photic water layer, high MUFA supply from their benthic diet, and conversion of saturated FAs (SFAs) to MUFAs in the tissues of the fish. Despite the MUFA percentage among the abyssal species reached even 50% (by weight) of total FAs, the PUFA percentage still remained above 20% in every species. The muscle MUFA/SFA ratio correlated negatively with the PUFA content of the fish muscle, suggesting viscosity control integrating the fluidity contributions from the dietary PUFAs and potentially endogenous MUFAs.

Effect of low water temperature at reproductive stage on yield and glutamate metabolism of rice (Oryza sativa L.) in China

In rice, plants exposure to low water temperature (Tw) treatment during reproductive stage severely affects the yield-related traits, diminishes physiological and metabolic processes leading to low yield. In higher plants, the glutamate metabolism playes central roles in the amino acid metabolism, plant defense and productivity. In order to understand how low Tw treatment during reproductive stage affects the yield and relative physiological parameters of glutamate metabolism, the rice were subjected to 17°C low Tw for varying length of time (three, six, nine, twelve, and fifteen days) at reproductive stage (microsporogenesis). The indexes of yield, yield-related traits, amino acid content, enzyme activities of glutamate metabolism, and the relationships among them were investigated, respectively. The results revealed that the changes degree of yield, yield-related traits and glutamate metabolism varies with rice varieties and duration of exposure. Multiple stepwise regression identified glutamate (Glu) content and glutamate dehydrogenase (GDH) activity as important traits that influenced the grain yield and spikelet sterility, respectively. By adjusting the glutamate metabolism level of leaves in rice, we can thus improve rice cold tolerance, and reduce the effect of low Tw (17°C) treatment on grain yield and spikelet sterility during reproductive stage.

Experimental infection of infectious myonecrosis virus (IMNV) in the Pacific white shrimp Litopenaeus vannamei (Boone, 1931)

Bioassays are essential in detecting resistant animals based on standardized challenge tests. A controlled bioassay system for Infectious myonecrosis virus (IMNV) was developed through two methods of infection, by ingestion and injection, in Litopenaeus vannamei. For ingestion bioassays, shrimp (2–3.9 g) were exposed to four feeding infection treatments (feeding with infected tissue-FIT without stress; FITS-salinity stress; FITES-temperature and salinity stresses and FITA-alkalinity stress). No signs of disease were observed and 30 % of the animals were infected, with FITS treatment exhibited the higher proportion of infected animals (p ≤ 0.05). In the injection treatments, a stock inoculum was quantified (viral load of 9.82 × 105 IMNV copies µg−1 of total RNA) and a tenfold serial dilution was tested at 28 °C and, from 10−5 to 10−9 at 26 °C. Over 60 % of infected animals were obtained for dilutions between 10−5 and 10−7 at 28 °C, while at 26 °C; these values ranged from 30 to 50 %, with a clear effect of low water temperature in reducing the proportion of infected shrimp. In general, higher survival probabilities of infected shrimp were achieved 5 days after exposure, followed by a quick decrease at the tenth day post-inoculation. Median infectious dose (ID50) was determined between 2.44 × 10−8 and 1.19 × 10−7 at 28 °C and between 1.76 × 10−6 and 1.28 × 10−5 at 26 °C for 15 days post-infection, respectively. Injection treatments based on known infectious dose were the most reliable method of estimating viral infectivity for IMNV selection. Moreover, FITS treatment was identified as an environmental risk factor, contributing to increase in IMNV infection prevalence.

Effect of low water temperature on viral replication of white spot syndrome virus in Procambarus clarkii

This study evaluated the effect of low water temperature (10 ± 1 °C) on viral infection and replication of white spot syndrome virus (WSSV) in crayfish, Procambarus clarkii, under standardized conditions. Crayfish were (i) maintained at 24 ± 1 °C before challenge and 10 ± 1 °C afterwards, or (ii) maintained at 10 ± 1 °C before challenge and 24 ± 1 °C afterwards. No mortality was observed when crayfish were held at 10 ± 1 °C after challenge, but mortality reached 100% when they were transferred to 24 ± 1 °C. Competitive PCR showed that viral levels at 10 ± 1 °C rose from 10 6 to 10 8 copies/mg of gill tissues, while at 24 ± 1 °C levels increased from 10 6 to 10 10 copies/mg of gill tissues during the same time interval. These results showed that a low water temperature of 10 ± 1 °C could reduce viral replication when compared to 24 ± 1 °C but could not prevent it.

Effect of Low Water Temperature on Rice Yield in California

Water temperature has increasingly become a matter of concern for California rice (Oryza sativa L.) growers due to a need for public water agencies to improve habitat for fish. Prudent management of water resources to balance the needs of environmental and agricultural interests requires the quantification of water temperature effects on rice productivity. Our objective was to evaluate two alternative thermal unit models for the effect of low water temperature on yield. One model was based on the total number of hours below a given threshold water temperature Tb (abbreviated TNHB Tb) and the other was based on the concept of inverse degree days (i.e., degree days below a given threshold water temperature) (abbreviated IDD). We tested these models at a range of values of Tb between 10 and 25°C on data from two commercial fields during 2 yr. Results showed that the effect of low water temperature may be much greater than would be apparent from the visual appearance of the rice plants. Values of IDD and TNHB Tb were very highly correlated for 4 of the 4‐yr field combinations. A logistic curve model based on TNHB 20°C provided the best fit to the aggregated data.

Low-temperature incubation of walleye pollock (Theragra chalcogramma) eggs from the southeast Bering Sea shelf and Shelikof Strait, Gulf of Alaska

To determine the effect of low water temperature on development, walleye pollock (Theragra chalcogramma) eggs from the Bering Sea were reared at � 0.61C, 0.41C, 2.01C, and 3.81C. One group of eggs was reared at 3.91C under a diel light cycle (14 h light, 10 h dark) to observe the effect of light on development and hatching. Development was normal for all temperatures except � 0.61C; abnormal development of the tail and lack of development of eyes occurred in some embryos. Time to 50% hatch was 820, 620, and 424 h at 0.41C, 2.01C, and 3.81C. Eggs incubated in diel light at 3.91C developed at the same rate as eggs incubated in constant dark at 3.81C, but required an additional 72 h to reach 50% hatch. A piece-wise regression model was generated to predict egg age for incubation temperatures of � 0.61C to 3.81C. For temperatures recorded in the southeastern Bering Sea 1995–1998, the model predicted incubation periods for walleye pollock eggs that varied by 13 days between the warmest and coldest years. Walleye pollock eggs from Shelikof Strait, Alaska, were incubated at 0.21C, 1.81C, and 2.81C. Development was normal for all temperatures. A piece-wise regression model (as above) was generated for incubation temperatures 0.2–2.81C. When the regression models were compared, Bering Sea eggs (1.4–1.7 mm in diameter), required more time for development prior to hatch than Shelikof Strait eggs (1.2–1.3 mm in diameter) at 1.81C and 2.81C. However, for temperatures 0.2–2.01C, Bering Sea walleye pollock began hatching earlier and at a developmentally younger age than Shelikof Strait walleye pollock. Published by Elsevier Science Ltd.

Age determination in the Antarctic shrimp Notocrangon antarcticus (Crustacea: Decapoda), using the autofluorescent pigment lipofuscin

Determination of basic population parameters in long-lived Crustacea is hindered by a lack of appropriate methods for age determination. This study uses the pigment lipofuscin as an age marker in the common Antarctic decapod Notocrangon antarcticus (Pfeffer, 1887) from the eastern Weddell Sea. Resin brain sections of the lateral somacluster of the olfactory lobe of 189 specimens were digitally recorded by confocal microscopy and images were subsequently analyzed. A modal progression analysis of the lipofuscin concentration–frequency distribution revealed a total of eight regularly spaced modes presumed to reflect consecutive annual age classes. All eight modes contained females, and the first four contained males. No regular modes were obvious in the comparable length-frequency distribution. The average yearly pigment accumulation was nearly linear and estimated as 0.02% area fraction year−1, which is considerably lower than rates published for species from lower latitudes. This is probably explained by the effect of low water temperature on metabolism and lipofuscin accumulation rate. The growth parameters CL∞ and k from the von Bertalanffy growth function were 22.3 mm and 0.79 year−1 for females, respectively, and 16.9 mm and 0.64 year−1 for males, respectively. Mortality, estimated from catch curves, amounted to 0.44 year−1 in females and 0.92 year−1 in males, whereas P/B, calculated from the mass specific growth rate method, was slightly lower. The results indicate that the lipofuscin-inferred population parameters are an improvement over what can be learned about N. antarcticus with traditional methods.

Effect of low water temperature on metabolism and growth of a subtropical strain of Caulerpa taxifolia (Chlorophyta)

The cold tolerance capacity of samples of the marine green alga Caulerpa taxifolia, ob- tained from Moreton Bay, Brisbane, Australia, was investigated by exposing samples to seawater tem- peratures of 9 to 15°C, for periods of 4 to 10 wk, after maintenance at 22°C. Residual effects of cold wa- ter exposure were evaluated by re-acclimating samples to 22°C. Phenotypic expression and survivorship were monitored throughout both cold treatment and re-acclimation phases. Measurements of photo- synthesis and respiration were made toward the end of the cold treatments and after re-acclimation. Samples exposed to 9 and 11°C water exhibited retraction or loss of chloroplasts (or chlorophyll) from the mid-rib regions of the pseudo-fronds. After 4 wk of exposure to 9°C the only green coloured regions of the fronds were the extremities of the pinnules; 1 to 2 wk later these samples began to decompose. Sam- ples kept at 11°C retained the bulk of their photosynthetic pigments and survived throughout experi- ments. The stolons of samples tended to grow upward toward the seawater surface rather than parallel to the substratum. Samples at all treatment temperatures tended to become progressively detached from the substratum through stolon extension without intermittent rhizoid attachment. Several samples be- came fragmented and covered with mucilaginous epiphytes during re-acclimation, such that those lack- ing rhizoid anchorages, rose to the seawater surface, buoyed by metabolic gases trapped in the mu- cilage. During cold treatment, the maximal rates of gross and net photosynthesis (Pm g and Pm n ), normalised to dry weight or tissue protein content, and the ratio of Pm g to dark respiration (-R) varied directly with temperature. The irradiance required for compensation (Ic) varied inversely with temperature. The rate of dark respiration increased with cold exposure. Calculation of whole day net production indicated that rates of photosynthesis among samples incubated at 13°C or below were insufficient to maintain exist- ing tissue biomass. There were no residual effects of cold exposure after re-acclimation, except that 11°C samples failed to increase in relative protein content as a function of ambient irradiance, perhaps due to nitrogen limitation. Results indicate a cold-tolerance threshold of 9 to 11°C, thus genetic modification does not need to be invoked to explain the occurrence of C. taxifolia in the northwest Mediterranean.

Temperature Effects on Flocculation Kinetics Using Fe(III) Coagulant

The effect of low water temperature on flocculation kinetics was examined using ferric nitrate to coagulate kaolin clay in water under tightly controlled treatment conditions. Both the particle size distribution data obtained from an automatic image analysis system and the on-line measurement of the degree of turbidity fluctuation in a flowing suspension by a photometric dispersion analyzer were used to measure flocculation kinetics. Results show that cold water temperature had a pronounced detrimental effect on flocculation kinetics. To improve flocculation kinetics at low water temperature, maintaining constant pOH to adjust water chemistry for temperature changes was founded to be partially effective, but only in the more acidic pH range studied (≤pH 6.8). However, the improved performance did not reach the performance at room temperature.