Cumulative Water Temperature Research Articles

A measure to prevent relapse of reddening adductor disease in pearl oysters ( Pinctada fucata martensii) by low-water-temperature culture management in wintering fisheries

In this study, we prove that the mass die-offs occurring in conjunction with red adductor disease in pearl oysters are caused by an infection. Our research also reveals the influence of water temperature on the onset of the disease and its progress, and we propose measures that are effective in mitigating harm from the disease. To analyze the effect of water temperature on the onset and progress of the disease, laboratory infection experiments were performed over a range of water temperatures (13 °C–31 °C). The experiments showed that disease onset and progress were highly dependent on water temperature. No outbreak was observed at temperatures below 16 °C, while the adductors of experimentally infected oysters turned red in a short time at temperatures between 19 °C and 31 °C. Our research showed that the cumulative water temperature value for days when water temperature was above 19 °C (AT 19 = Σ( T i), T i > 19) is an effective numerical indicator for the onset of red adductor disease. We also found that when pearl oysters already infected with red adductor disease at a high rate are kept at water temperatures below 16 °C in the winter for a certain minimum period of time, clinical signs regress, and that this treatment is also effective in delaying relapses of the disease with rising water temperatures in the spring. We determined a numerical indicator for finding the low-temperature index that is most effective in delaying disease onset. This is the low-temperature burden based on the number of days with water temperatures of 16 °C or below and those days' temperatures (LTI 16 = Σ(16 − T i), T i < 16 °C). We found that the larger the LTI 16 value, the greater the effectiveness in suppressing the onset of red adductor disease. Hence, appropriate low-water-temperature management in the winter helps prevent the relapse and progress of the disease in the spring and beyond when water temperature rises. Results of this research strongly suggest that the LTI 16 value in wintering fisheries and the cumulative water temperature of the days in spring and beyond when the water temperature is above 19 °C (AT 19) make it possible to predict when red adductor disease will break out in pearl oysters, and therefore help efforts to mitigate damage from relapses.

Derivation of quantitative management objectives for annual instream water temperatures in the Sabie River using a biological index

Adaptive management of river systems assumes uncertainty and makes provision for system variability. Inherent within this management approach is that perceived limits of 'acceptable' system variability are regarded not only as testable hypotheses, but also as playing a central role in maintaining biodiversity. While the Kruger National Park currently functions as a flagship conservation area in South Africa, projected increases in air temperatures as a consequence of global climate change present challenges in conserving this biodiversity inside the established land boundaries. Within the rivers of the Kruger National Park, a management goal of maintaining biodiversity requires a clearer understanding of system variability. One component of this is water temperature, an important water quality parameter defining the distribution patterns of aquatic organisms. In this study, Chiloglanis anoterus Crass (1960) (Pisces: Mochokidae) was selected as a biological indicator of changes in annual water temperatures within the Sabie River in the southern Kruger National Park. Relative abundances of C. anoterus were determined using standard electro-fishing surveys. The presence or absence of C. anoterus was linked to cumulative annual heat units using a logistic regression model, and a critical annual cumulative water temperature threshold estimated. A correlative relationship between this temperature threshold and a biological index using a C. anoterus condition factor provides river ecologists with a tool to assess ecologically significant warming trends in Sabie River water temperatures. A similar approach could be applied with relative ease to other Southern African river systems. Further testing of this hypothesis is suggested, as part of the adaptive management cycle.

Effects of water temperature on embryonic development in the northern Pacific asteroid, Asterias amurensis, from the southern coast of Korea

Summary Although the starfish, Asterias amurensis, has been known to cause severe damage to benthic shellfish populations through predation, few studies have been made of the basic biology of this species in Korean waters. Laboratory experiments were performed to obtain information on the effects of temperature on the embryonic development during the early life stage of A. amurensis. Developmental time decreased as temperature increased, and the elapsed time to develop to the bipinnaria larva at 10,15, and 20°C was 120,72, and 60 h, respectively. The average biological minimum temperature was estimated to be 0.97°C. The cumulative water temperatures for some developmental stages from 2-cell to bipinnaria larva were calculated. Temperature did not affect the fertilization rate (p = 0.866), while it significantly affected the rate of hatching and larval normality (p <0.001). Between 10 and 15°C, there was no significant difference in the rate of hatching (p = 0.157) and larval normality (p = 0.437). However, at 20°C, major reduction in rates of hatching and larval normality were found. We therefore suggest that the optimal temperature for embryonic development of A. amurensis is 15°C.

Analysis of key variables controlling phosphorus removal in high rate oxidation ponds provided with clarifiers

This study evaluates the influence of hydraulic retention time (HRT), solar radiation, and water temperature on phosphorus removal from two experimental high rate oxidation ponds (HROP) with clarifiers. Both HROPs were operated for a period of one year with different HRTs (3 to 10 d), but under the same environmental conditions. Phosphorus species, phytoplankton biomass, solar cumulative radiation, water temperature and pH were measured once a week. Average total phosphorus removal (TP) was higher in the HROP operated with a higher HRT (43%) than in that using a lower HRT (32%). TP removal was due to dissolved reactive phosphorus (DRP) removal in the mixed liquor of the HROPs and transformation of DRP into particulate phosphorus (PP), with subsequent sedimentation of PP in the clarifiers. The influence of HRT on TP removal was due mainly to its control over DRP removal, which was observed to be more important in autumn and winter. The lowering of solar radiation and temperature in autumn and winter and their influence on DRP removal can barely be compensated by HRT to obtain a significant TP removal. This work indicates that DRP transformation into PP depends mainly on environmental factors through their mediated influence on pH and chemical precipitation. WaterSA Vol.28(1) 2002: 55-62

Growth of large and small forms of pond smelt Hypomesus nipponensis in Lake Kasumigaura, Japan

SUMMARY: Growth formulae of two forms of pond smelt Hypomesus nipponensis in Lake Kasumigaura were estimated using frequency distribution of body length, and the relationship between water temperature. Their growth was studied based on specimens collected by fisheries during the period from June 1992 to February 1998. The growth parameters of von Bertalanffy, Gompertz, and Logistic models and their modified models in which the growth rate changes with one or two cycles per year were calculated by the non-linear weighted least squares method. On the basis of the AIC (Akaike’s Information Criterion) values, the modified models in which the growth rate changes with two cycles per year were selected as the best-fitting models for both forms. These formulae represent biological characteristics of the pond smelt in Lake Kasumigaura, i.e. the growth is superior in spring and autumn but inferior in summer and winter. The growth patterns of both forms were similar, but the large form showed a more superior growth rate than the small form from June to July. As for the relationship between the growth and water temperature, until the middle of September the growth was inferior as the cumulative water temperature increased, after which the small form grew to about 82 mm and the large form grew to about 108 mm without any influence from water temperature.

Pikeperch, Stizostedion lucioperca (L.), catch in relation to juvenile density and water temperature in Pärnu Bay, Estonia

Abstract The abundance of 0+ pikeperch, Stizostedion lucioperca (L.), in trawls was compared with water temperature, water level and commercial catches 6–9 years later. The abundance of juveniles in autumn was positively correlated with the water temperature but not with water level in May or in June. The sum of a year abundance of juveniles showed a strong correlation with the catch years later. This abundance and the cumulative water temperature between August and October inclusive in five consecutive years one year prior to recruitment into the commercial fishery explained 86% of the variation in catches. This empirical model indicates that catches of pikeperch depend on both juvenile abundance and water temperature.

Modeling Flowering Time of Rice Plants under Natural Photoperiod and Constant Air Temperature

AbstractRice (Oryza sativa L.) plants respond to variations in photoperiod. The prediction of flowering time of photoperiod‐sensitive rice plants is important for crop management. The objective of this study was to analyze the photoperiod sensitivity of rice plants under natural photoperiod and constant air temperature, and to derive a simple model to predict flowering time under these conditions. Rice cultivars were sown at 2‐wk intervals during 1 yr in a greenhouse maintained at a constant air temperature. The number of days required from emergence to flowering was constant for rice plants sown between August and February, while those sown between March and July required more time. On the basis of these results, the authors derived an equation describing the cumulative water temperature over the time required for flowering as a function of photoperiod [f(P)] and sowing date. The form of f(P) was calculated using nonparametric methods. The value of f(P) was almost zero when the photoperiod was shorter than the critical photoperiod (Po); when the photoperiod was longer, however, the value of f(P) increased proportionally. The function was simplified to represent the effective photoperiod. The equations of this model were able to analyze quantitatively the photoperiod sensitivity of rice plants, and the observed flowering time was accurately estimated.

A New Standard Formula for Seasonal Growth of Fish in Population Dynamics.

This formula is based on the Richards formula, which includes well-known growth formulae, and is invariant for allometry. It is expanded by exchanging the independent variable from time to its function, in other words the cumulative water temperature. This standard formula includes the method of substituting values for the cumulative water temperature into the time term, the mathematical model of adding sine functions to the time term, and switched growth rate models. This standard model is given by general theory, which makes the character of parameters clear and helps to analyze the growth formula statistically.

A MODEL FOR GAMETE RELEASE IN ASCOPHYLLUM NODOSUM (PHAEOPHYTA)1

ABSTRACTThe question of what controls gamete release in Ascophyllum nodosum (L.) Le Jolis was studied at six sites along the central coast of Maine. Percent release was assessed weekly along randomly marked transect lines in the mid‐intertidal zone. Six independent variables–water temperature at high tide, air temperature at low tide, nitrogen (ammonia, nitrite, and nitrate), and salinity–were measured concurrently. Stepwise multiple regression analysis on the percentage of plants having released gametes revealed that water temperature at high tide accounted for most of the among‐site variation (R2= 0.77) in the timing of release. The addition of Julian day increased the R2 to 0.82; no other variables were significant. Probit analysis, based on water temperature at high tide, generated an environmentally realistic model for predicting gamete release. The model predicts the onset, midpoint, and termination of gamete release at 6, 10, and 15°C, respectively, and the midpoint at a cumulative water temperature of 358°C. This model has value for developmental studies and, potentially, for reseeding A. nodosum populations. Probits may be useful for characterizing phenological events in other fucoids and algal species.

Larval Instars and Growth Pattern of a Univoltine Black Fly, Prosimulium kiotoense (Diptera: Simuliidae), in Kyushu, Japan

Seven larval instars were detected for a natural population of Prosimulium kiotoense Shiraki in Kyushu, Japan, from the size frequency distribution of postgenal lengths. Growth in P. kiotoense larvae followed a geometric progression from first to sixth instars, but the size ratio between sixth and seventh instars was smaller than between other successive stadia. The linear relationship between the mean instar value and daily cumulative water temperature indicated that development between instars required 82.6 degree-days (DD). The accumulated temperature for larval development of this species was estimated to be 600 DD.

Incubation of salmon eggs and rearing of alevins: Natural temperature fluctuations and their influence on hatchery requirements

The eggs and alevins of Atlantic salmon ( Salmo salar L.) are normally reared in Scotland using surface water in open flow systems. The literature indicated that incubation temperatures should generally be in the range 4°–11°C. A strategy that might lead to most success would be to keep green eggs at 6°C and then reduce the temperature to 4°C during subsequent development. Genetic variations between races of salmon in different river systems may partly account for differences in reported incubation times. Several northern stocks are known to be cold-adapted and it seems clear that standardised incubation regimes are inappropriate in the absence of standardised fish and water quality. The cumulative ambient water temperatures at four Scottish hatcheries were shown to approximate those required by the industry, although some very low temperatures were regularly experienced. The technology for temperature control is generally available, but has not been widely used. To be most succussful it should be geared towards producing fish ready for first feeding by the end of April, as natural temperatures are increasing rapidly (10°–14°C), so that an open flow system can be used for feeding. A review of the literature showed that temperature effects should not be considered in isolation. Low pH, resulting from acid rain and snow-melts, was also recognised as a potential problem as was subsequent metal pollution. To be most effective, recycle systems should be designed to control both temperature and pH.

On the Advantages of Earlier Transplanting of Rice in Miyagi Prefecture

Traditional planting date of rice seedlings on flooded paddy fields is around 10th of May in Pacific Ocean costal district (Miyagi prefecture) of south Tohoku in Japan, and it has been believed that the transplanting before this date is difficult because air temperature is not yet high enough for rice growth, or even harmful. In this district, however, one of the peak periods of solar radiation intensity appears in the spring. This work was made with the aim to increase the rice yield by advancing the planting date so as to utilize the rich radiation energy in the spring of this district.The temperature conditions in this district were re-examined in 1977 and 1978 for the last decade of April. Several observation spots were spaced over this district (see Fig. 1), and air and water temperatures were measured. Since the numbers of the spots for the water temperature were limited, the spatial distribution of the water temperature was estimated from those of the air by using empirical equations given in Table 1. The averages of the daily maximum, the daily minimum and the daily mean air temperatures over the last decade of April in this district were found to distribute in the ranges of 14-17°C, 2-6°C and 8-12°C, respectively (Figs. 2 and 3), and these temperature conditions were considered not to be sufficient for the rice growth, or even harmful. As is shown in Figs. 2 and 3, however, the averages of the daily maximum, the daily minimum and the daily mean water temperatures over the same period were in the ranges of 24-28°C, 3-9°C and 11-15°C, respectively and considerably higher than those of the air. Since the shoot apical region of rice is in water at the early growth stage of the plant, the rice at this stage is more strongly affected by water temperature than by air temperature. From these facts we concluded that in most part of this district the water temperature at the last decade of April is high enough to permit the rice growth and developments without suffering severe cold damages.The effects of early transplantings on the growth and yield of rice were, then, examined by the field experiments made in 1977 and 1978. The rice cultivar used for the experiments was ‘Sasanishiki’ and 10 experimental fields were distributed over this district (Fig. 1). In each field the rice seedlings (raised in a nursery green house) were transplanted on different dates, which were 0-18 days before the traditional planting date. With advancing the planting date, the plant dry weight and the grain yield, both, linearly increased in both years (Figs. 5 and 6). When the plants were transplanted before the end of April, the yield in both years was above 600kg/10a which was significantly higher than the traditional yield level of this district. The advantage in the yield of the early transplantings was considered to be realized mainly through inceased total sunshine duration that the plants received during the growth, because the sunshine duration increased with advancing the transplanting date and because the yield was approximately linearly proportional to the sunshine duration (Fig. 5). The cumulative water and air temperatures at the grain-filling stage (40 days after the heading) also increased 3 to 7% by the early transplanting of 20th of April.