Influence Of Seasonal Factors Research Articles

Towards a validation of a cellular biomarker suite in native and transplanted zebra mussels: A 2-year integrative field study of seasonal and pollution-induced variations

Two of the questions raised in the validation process of biomarkers are their relevance in the identification and discrimination of environmental perturbations, and the influence of seasonal factors on these biological endpoints. Determining the advantages and restrictions associated with the use of native or transplanted animals and comparing their responses is also needed. To obtain this information, a 2-year integrative field study was conducted in the vicinity of a nuclear power plant in northeastern France. A station was located in the reservoir receiving the cooling waters of the plant, and two other sites were studied 2 km upstream and 5 km downstream from the reservoir's discharge in the Moselle river. Elevated temperatures, copper contamination and a 1.4-fold-concentration factor of dissolved salts affected water quality of the reservoir. Native and transplanted zebra mussels ( Dreissena polymorpha) were collected monthly and their digestive glands were processed for histochemical determinations of the lysosomal and peroxisomal systems and of the lipofuscin and neutral lipid contents. The responses were quantified using automated image analysis and stereology. Apart from neutral lipid contents, there were no systematic seasonal patterns in mussel populations or from 1 year to another. Principal Component Analyses showed a general higher discrimination potential of biological responses in transplanted organisms compared to native ones. They also pointed out the relationships between the cellular and physiological markers and abiotic factors. The present multiple biomarker integrative approach in transplanted D. polymorpha brings promising elements in their validation process as relevant biomonitoring tools.

The influence of seasonal factor on chemical dissolving of limestone variability in Svrljiska valley

How big is the influence of climatic factor on the intensity of rocks dissolving (limestone) in Serbia? Previous investigations of rivers water chemistry changes have shown it insignificance. This investigation shows significant collective influence of climatic elements contained in "seasonal factor".

The size of the thymus: an important immunological diagnostic tool?

The report on the influence of seasonal factors on thymic size in early life describes a pattern of ultrasonographically measured thymic growth in Gambian infants including the finding of a smaller thymus in the hungry season. These factors raise a number of important questions: Is the size of the thymus relevant to its function and could measurement of the thymus be a useful immunological diagnostic tool in the investigation of thymic function in humans with a depressed immune system? Studies using the size of the thymus as an immunological diagnostic tool should be encouraged.

Breaking physical dormancy in seeds – focussing on the lens

○The influence of seasonal factors on the germination of impermeable seeds of Fabaceae was studied. Seeds of 14 herbaceous species were buried for up to 2.5 yr and exposed to natural seasons. At regular intervals, seeds were exhumed and germination was tested in four different temperature regimes. Some species had a very low percentage germination regardless of season, others germinated predominantly in the autumn. Six species showed a marked seasonal cycle with high germination percentages in spring and very low percentages in other seasons. The results of the burial experiment were similar to the pattern of seedling emergence in field conditions. ○ High percentage germination in spring could be simulated in controlled conditions for Melilotus albus, Medicago lupulina, Lotus corniculatus, Trifolium pratense and T repens. Seeds of T. pratense had a high percentage germination after cold treatment, whereas seeds of the other four species were brought to germination by chilling for 8 wk followed by exposure to daily alternating temperatures (15/6°C or 20/10°C). Without previous chilling, these seeds did not respond to the alternating temperatures. ○At least for some legume species, a combination of temperature treatments may act as a signal for seeds and induce water uptake and germination. If the temperature requirements are not fulfilled, seeds remain impermeable and dormant until the next favourable season.

The silt carrying in Jerma river basin

The silt carrying in the upper part of Jerma river basin in amount of 82.3 t/km/year is relatively high, considering the situation in all Serbia. The specific silt carrying in the upper part of Crnica river basin is 23.9 t/km/year (Manojlovic P.), while it is even lower in the basin of Crni Timok river (3.5 t/km/year; Manojlovic P, Gavrilovic Lj. 1991.). In the Kolubara river basin, the specific mechanical water erosion is between 4.6 t/km/year (Gradac) and 73.2 t/km/year in Tamnava basin (Dragicevic S. 2002). Greater erosion in the upper part of Jerma river basin is result of great part of metamorphic stones that intensively disintegrates and significant anthropogenic influence in Znepolje. The great slopes at the left side of the basin, under the Ruj mountain, should be considered, too. That doesn't mean that the erosion is strong, because, for example in the basin of Beli Timok, between Knjazevac and Zajecar, it is 186 t/km/year. Following regression, base on flow and silt concentration values can calculate the silt carrying very precisely: t/day=6251+26875 - C+1058 - Q Based on beta coefficients (0.73 for silt and 0.31 for flow) it could be concluded that concentration of silt has greater influence on erosion, than flow. More interesting is the influence of seasonal factor on the carrying of suspended silt. Months with the highest amount of carried suspended material are March, April and May. During these months 50.5 % of average yearly value is evacuated from a basin. Similar excessivity has been noticed in the other basins (Dragicevic S. 2002), only in other months.

Effect of season on fertility of sows

Reduced fertility of sows during the warmer period of the year is a well-known occurrence in practical production. Namely, during summer months gilts become sexually mature later, the interval from weaning to estrus is prolonged, there is a greater number of postlactation silent estruses anestrias and ovarian cysts, the value of conception is lower, there are more irregular failed fertilizations, there is a higher degree of embryo mortality, and the litter size is smaller. This is why this occurrence presents an important zootechnological, veterinary-medical and economic problem. Most scientific research shows that this phenomenon is a consequence of the effects of an extended daily photoperiod and a higher ambient temperature. However, the degree of the individual effect of these factors has not been determined clearly, or the physiological and endocrinological mechanisms of their action. It is probably not possible completely to avoid the negative influence of seasonal factors on reduced fertility in sows during the summer period. However, it can be significantly alleviated with a regular maintenance technology, diet, hygiene and medical protection of sows. This paper presents knowledge acquired so far on the manifestation of this phenomenon, its physiological and endocrine bases, as well as possibilities for its practical resolving.

Restoration of body mass in King Penguins after egg abandonment at a critical energy depletion stage: early vs late breeders

In fasting‐incubating seabirds, it has been proposed that egg abandonment and refeeding should be induced when a low body mass (BM) threshold is attained, thus ensuring adult survival at the expense of immediate breeding. In the context of life‐history trade‐offs in long‐lived birds, we have tested this hypothesis by comparing short‐term survival and restoration of BM in King Penguins Aptenodytes patagonicus that abandoned their egg to those that were relieved normally by their mate at the end of the first incubation shift. Since King Penguins have an extended laying period, the possible influence of seasonal factors was also examined by comparing early and late breeders. Forty incubating males were experimentally forced to fast until egg abandonment by preventing relief by the female. At egg abandonment of both early and late breeding males, BM was below the BM threshold, fasting duration was eight days (about 30%) longer than for relieved birds, and plasma uric acid level was elevated (signature of increased body protein catabolism, phase III of fasting). All abandoning birds survived and came back from sea at a BM similar to that of relieved penguins. The duration of the foraging trip of abandoning early breeders was the same as that of relieved birds, and some abandoning birds engaged in a new breeding attempt. Abandoning late breeders, however, made foraging trips twice as long as those of relieved males. This difference can be explained by time constraints rather than nutritional constraints, abandoning early breeders having enough time left in the breeding season to engage in a new breeding attempt in contrast to abandoning late breeders. These observations lend support to the suggestion that not only BM but also an internal clock intervene in the decision to engage in breeding or not. By preventing a lethal energy depletion ashore and by acting at a fasting stage where the capacity to restore BM at sea is unaffected, abandonment at a low body condition threshold plays a major role in the trade‐off between adult penguin survival and reproduction.

Seasonal development of phytoplankton and zooplankton in a high-rate algal pond

An experiment with high rate algal ponds (HRAP) was carried out in the Mediterranean region. Plankton populations and physicochemical parameters were measured weekly over a two year period in a high rate algal pond treating domestic wastewater. The residence time was kept at 8 days. The pond was mixed with a paddle wheel. The objective of the work presented here was to characterise the seasonal successions of phytoplankton and zooplankton in this hypereutrophic ecosystem. There was intensive photosynthetic activity in the pond. Chlorophyll concentrations approached 5 mg/l. Because of the extremely eutrophic environment, phytoplanktonic diversity was restricted (3-12 taxa). Chlorella and Scenedesmus were the predominant taxonomic units. Scenedesmus dominated in Spring whilst Chlorella, with its more rapid reproduction rate, dominated during the months with lower irradiance (winter and autumn) when there was less predation. The influence of seasonal factors on the zooplankton translated into alternating populations dominated by protozoa with a short generation time in autumn and winter and metazoans (with a longer generation time) in spring and summer. A multivariate factor analysis of the variables sampled showed the effect of the physico-chemical variables on the major plankton successions in this ecosystem. A comparison of the successions in this hypereutrophic ecosystem with those observed and modelled by Sommer (1989) in the natural environment showed a good correlation between these two ecosystems despite their differences in hydrodynamic characteristics.

Seasonal development of phytoplankton and zooplankton in a high-rate algal pond

An experiment with high rate algal ponds (HRAP) was carried out in the Mediterranean region. Plankton populations and physicochemical parameters were measured weekly over a two year period in a high rate algal pond treating domestic wastewater. The residence time was kept at 8 days. The pond was mixed with a paddle wheel. The objective of the work presented here was to characterise the seasonal successions of phytoplankton and zooplankton in this hypereutrophic ecosystem. There was intensive photosynthetic activity in the pond. Chlorophyll concentrations approached 5 mg/l. Because of the extremely eutrophic environment, phytoplanktonic diversity was restricted (3-12 taxa). Chlorella and Scenedesmus were the predominant taxonomic units. Scenedesmus dominated in Spring whilst Chlorella, with its more rapid reproduction rate, dominated during the months with lower irradiance (winter and autumn) when there was less predation. The influence of seasonal factors on the zooplankton translated into alternating populations dominated by protozoa with a short generation time in autumn and winter and metazoans (with a longer generation time) in spring and summer. A multivariate factor analysis of the variables sampled showed the effect of the physico-chemical variables on the major plankton successions in this ecosystem. A comparison of the successions in this hypereutrophic ecosystem with those observed and modelled by Sommer (1989) in the natural environment showed a good correlation between these two ecosystems despite their differences in hydrodynamic characteristics.

Zooplankton population dynamics in experimentally toxified pond ecosystems

To evaluate ecosystem response to and recovery from toxic contamination, we added phenolic compounds to a series of experimental ponds. Toxicants were added repeatedly in a temporally staggered sequence to evaluate the influence of seasonal factors and previous exposure history on the responses to toxicant stress. We hypothesized that seasonal changes in ecosystem structure, e.g. shifts in the relative importance of ''top-down'' and ''bottom-up'' controls on energy flow, would influence the system-level responses to the toxicant. Information from these experiments is being incorporated into models that predict ecological risk and system-level behavior under toxicant stress. Here we focus on the responses of zooplankton populations to toxicants, and factors which may affect the apparent severity of toxic effects. 9 refs., 4 figs.

Seasonal factors affecting egg production and viability of eggs of Acartia tonsa Dana from East Lagoon, Galveston, Texas

Egg production and hatching success were determined between March 1981 and March 1982 for the copepod Acartia tonsa Dana from East Lagoon, Galveston, Texas. During three-day experiments in the laboratory, field collected females were fed diets of (1) natural particles collected over the water column, (2) some modification of this and (3) the diatom Thalassiosira weissflogii. The latter served to isolate the effects of temperature and salinity from the effects of the natural particle diets on egg production. Specific rates of egg production, i.e. μg egg biomass/μg body biomass/time, were consistently higher per unit carbon than nitrogen. The influence of seasonal factors on egg production was compared. Salinity was inversely correlated with egg production, but had less effect than temperature. Positive correlations with temperature were always higher for specific rates per unit nitrogen than carbon. At 15°C, females produced ∼0·25 of their body carbon (or nitrogen) as eggs per day, whereas at 28°C, they produced at least their own biomass as eggs per day (up to 1·80). These high rates of A. tonsa were probably due to its reproductive biology and adaptation to the subtropical habitat as well as the high temperatures and food concentrations. The correlation between specific egg production rate and temperature was less with the natural particle diets than with the unialgal diet. This indicated that the quantity or quality of natural particle assemblages in East Lagoon influenced egg production. Egg viability was highest in the spring, but was not related to diet or the percentage of females with spermatophores.

Environmental design for a total animal health care system

The design requirements to achieve a good environment for healthy animals are described. Mechanically ventilated livestock buildings are usually insulated, with a constant maintained temperature of about 40 °F or above, extra heat being applied as necessary; naturally ventilated buildings depend on air movements, have no insulation, and inside temperatures approximate to outside temperatures. The fresh air inlet and exhaust systems are discussed in detail for mechanical ventilation; types of fans are described and rating tables illustrate their performance. Rules for the location of fans and the design of the fresh air intake system are emphasized and the influence of seasonal factors is discussed. The location of naturally ventilated buildings should be at least 50 ft away from other structures; ridge and wall openings are discussed in terms of dimensions; the roof underside should be steep and smooth and of proper construction.