Spring Pond Research Articles

Thermal Advantages of Communal Egg Mass Deposition in Wood Frogs (Rana sylvatica)

Embryos of most anurans develop within a special microhabitat consisting of the jelly secreted around the eggs by the female parent. The jelly envelope covering each embryo effectively provides a buffer between it and the surrounding water; moreover, the three-dimensional structure of the gelatinous egg mass is thought to represent an adaptation to thermal stresses and gas exchange requirements likely to be encountered by the developing embryos. Jelly masses of North American ranid frogs can be categorized into two species-specific types related to these environmental factors: globular-shaped and surface film forms (Moore, 1940). Frogs that breed early in the spring deposit their eggs in globular masses, which may facilitate the concentration and retention of heat (obtained from solar radiation) within the egg masses. Such traits may be particularly adaptive in the cold water characteristic of ponds in early spring. In contrast, frogs breeding in late spring and summer generally deposit their eggs in monolayer surface film masses. Because embryos of these species develop in much warmer conditions, their metabolic rates are higher than those of early-breeding species and the oxygen tension in the water is lower; thus this egg mass form may represent an adaptation to maximize surface area for gas exchange (reviewed in Salthe and Mecham, 1974). In some instances, this surface film structure may also functionally cool the eggs (Ryan, 1978). Wood frogs (Rana sylvatica) are the most northerly distributed ectothermic tetrapod in North America, with a range extending from north of the Arctic Circle to Georgia. In temperate regions, wood frogs breed in early spring, frequently before ice has completely melted from breeding ponds. Wood frogs deposit their egg masses in communal clumps within limited areas, thereby compounding insulation effects provided by their individual egg masses. Although several investigators have suggested that clumping of egg masses warms embryos (R. sylvatica: Herreid and Kinney, 1967; Hassinger, 1970; Howard, 1980; Seale, 1982; R. temporaria: Savage, 1950, 1961; Guyetant, 1966; Beattie, 1980; R. pipiens: Zweifel, 1968; Hassinger, 1970; Merrell, 1977; R. aurora, R. pretiosa: Licht, 1971), differences in temperatures of egg masses at various positions within clumps have not been investigated. We studied egg masses in two woodland ponds near Ithaca, New York during April 1978 and 1980. The ponds are shallow (less than 0.8 m depth) permanent pools, with little submerged or emergent vegetation. Most egg masses were deposited in clumps in the shallowest water (less than 0.25 m depth), attached to submerged vines, reeds, and twigs. Generally, all egg masses in a pond were deposited at one site, leading to the formation of one clump per pond. However, in 1978 at one pond, six clumps consisting of variable numbers of egg masses were formed, allowing us to compare characteristics of egg masses based upon clump size within the same pond. Clumps consisted of between 3 and 150 egg masses. To investigate the temperature of egg masses in relation to their positions within a clump, we measured temperatures of some egg masses (approx. 3 cm within each egg mass) both at the center and at the periphery of clumps, as well as those of single egg masses deposited outside clumps. We then compared these temperatures with that of the surrounding water, 10 cm outside the clump (5 cm below the water surface). All temperature data were obtained with a Schultheis quick-reading thermometer. To quantify the of each egg mass to the surrounding water, we visually estimated the percentage surface area of each egg mass not in direct contact with surrounding egg masses (on its lateral and ventral surfaces). Observations were made on clumps consisting of various numbers of egg masses, and in clumps on both sunny and overcast days. Although most egg masses within clumps were warmer than the surrounding water, egg masses in central locations within a clump were warmer than those at the edge of that clump. Temperature elevation of egg masses was inversely correlated with their exposed surface area. Moreover, egg mass temperatures increased (in all clump positions) as the size of the clump increased (Fig. 1). This finding suggests that the presence of additional egg masses in a clump provides added insulation, improving the heat retention capacity of the clumped egg masses. The correlation of temperature elevation of an egg mass with its surface area exposure was apparent both on sunny and on cloudy days. Figure 2 shows temperature elevation of egg masses as a function of their position within a clump of 36 egg masses on two successive afternoons. The first day was sunny and central egg masses were 3.0-3.2?C above ambient. Weather conditions the

Production of the freshwater prawn Macrobrachium rosenbergii in Israel : II. Selective stocking of size subpopulations

At the end of a temperate zone growout phase which lasts from May until mid-November, approximately 25% of the prawns would remain under market size. Two methods were employed to reduce this loss: overwinter storage in heated facilities with continual growth in production ponds in the following season, and selective stocking of separated juvenile size subpopulations into production ponds in the first growout season. Small (c. 10 g) prawns stocked in vacant nurseries at high densities at the end of the growout season reached the market size of > 25 g within 87 days. Small prawns were also released into production ponds in early spring after overwinter storage and reached the large market size after an additional growout period of 54 days. Nursed juveniles, undergoing secondary nursery, demonstrate a wide size distribution which allowed separation into two distinct size subpopulations. The large juveniles group, averaging 7.8 g, was transferred into intensive prawn monoculture ponds, while the small juveniles group, averaging 5 g, was stocked at low densities in a fish polyculture system. Stocking separated large juveniles, as opposed to stocking a whole mixed population in intensive monoculture, improved yields (1367 and 1127 kg·ha −1 respectively); average weight (47 and 40 g respectively); and the percentage of large market size prawns (61 and 48% respectively). Almost all of the small juveniles stocked in polyculture reached the large market size (54 g average) with a survival rate of 86%. The two methods of selective stocking of size subpopulations provide the means to maximize the percentage of marketable prawns within a single growout season, under the constraints of the temperate zone winter.

Analysis and structure of four lentic communities on the Colorado (U.S.A.) shortgrass prairie

AbstractFour natural lentic habitats on the Central Plains Experimental Range in Colorado were intensively studied physically, chemically, and biologically for 2 yr (1968–1970) and intermittently for 5 (1971–1975). Lynn Lake and Lake George were chosen as examples of ephemeral or temporary sites, while Cottonwood Pond and Spring Pond were chosen as permanent habitats. Chemically, the waters of each site were analytically separated into dissolved and suspended (sestonic) components. The temporary sites were characterized by their exceptionally high seston loads, the presence of Eubranchiopoda, the prevalence of Ca as the major dissolved cation, ana the high Fe content of their sediments. The two permanent sites, on the other hand, had high total dissolved salt content, rich and varied flora and fauna, Na as the prevalent cation in the dissolved fraction, and high Ca content in the sediments. All four of the sites were “seston digesters” with large amounts of wind‐blown organic material being entrapped, decomposed, and mineralized. By comparison with adjacent soils the sediments of all four basins were much richer in K, Zn, Fe, Cu, and Mn. Both temporary and permanent sites function as nutrient sinks. Rates of daily and annual phytoplankton primary productivity are reported for the two permanent sites.

Wisconsin desmids. II. Aufwuchs and plankton communities of selected soft water lakes, hard water lakes and calcareous spring ponds

This report summarizes the results of summer studies of five soft water lakes, five hard water lakes and six calcareous spring ponds in Wisconsin with respect to the composition of the plankton and aufwuchs communities and the relative role of desmids in those communities. The results are compared with similar data obtained from selected acid bog lakes, alkaline bog lakes and closed bogs. Soft water lakes harbored a greater aufwuchs and plankton desmid diversity than hard water lakes or spring ponds; however, diversity in acid bog lakes was substantially greater than in any other lake type. Utricularia contained the greatest desmid diversity and population density in every lake where it occurred. Staurastrum was the most prevalent genus in the plankton and it was the only one recorded from hard water lakes and calcareous spring ponds. Desmid aufwuchs population densities were roughly comparable in hard water lakes, soft water lakes and acid bogs and the contribution of desmids to the total aufwuchs population was similar for the latter two lake types. However, the plankton of acid bog lakes generally harbored substantially greater desmid populations and these populations contributed much more to the total population than in any other lake type. Aufwuchs data are presented for several hosts and comparisons of population densities are given among hosts within a given lake and between the same host in different lakes of a given type. Data for other algal groups are also included.

Hydrogen Ion Concentration, Dissolved Oxygen, and Carbon Dioxide dislsoved in the Lake Waters of the Tugaru Zyûniko Lake Group. Limnological Studies of the Tugaru Zyûniko Lake Group. Part 3

In connection with these lakes, the writer studied the pH, O2, and CO2 on three occasions, namely, in the middle of Aug., 1933, in the beginning of July, 1934, and the end of July 1934, having been assisted by Messesrs. K. Koba, N. Obara, I. Nagatu, N. Ando, and K. Sibata. The data obtained are given in Table 1-3, 6-9, and 13-16. From the viewpoint of chemical stratifications during summer, the Tugaru Zyuniko Lake Group consists of two different kinds of lakes. The first kind is a spring pond, such as Lake Aoike, which receives a large supply of cold spring water. The chemical stratifications are not well established. Although the water in every layer contains sufficient free carbon dioxide, it is undersaturated in dissolved oxygen. It reacts either weakly acidic or almost neutral. The other kind is a deep lake with but little spring water, such as Lakes Kosigutinoike and Ooike. In these lakes, chemical stratifications are very well developed. The surface water is saturated or supersaturated in oxygen and is poor in carbon dioxide. It reacts neutral or weakly alkaline. In most of lakes of this type, oxygen is suddenly reduced in the metalimnion, and the bottom water contains no oxygen. The bottom water contains much free carbon dioxide, and reacts weakly acidic. Two kinds of stratification are met with in lake of this class. The one characterized by marked maximum in the middle layer where oxygen is dissolved in supersaturation. It is due to the assimilation of diatoms. The water reacts strongly alkaine. The other stratification is recognized either in rather shallow and clear lakes or in deep and turbid lakes. Owing to the shallowness of the compensation depth or to the great turbulences in these lakes, no metalimnion maximum is established. Most Japanese lakes with anaerobic strata have dichotomous stratification of pH. Due to the strong buffer action of the water, except L. Yabureike, the lakes of the Tugaru Zyuniko have no such stratification. The lakes in the neighbourhood of Mt. Kuzureyama (east of the district) contain large amounts of hydrocarbonate CO2, and react neutral, while those in the western part are poor in HCO3-CO2, and react weakly acidic.

Water Temperature and Transparency of the Tugaru Zyûniko Lake Group. (2) Limnological Studies of the Tugaru Zyûniko Lake Group. Part 2

In connection with these lakes, the writer studied in the water temperatures together with the air temperatures on three occasions, namely, in the middle of Aug. 1933, in the begining of July 1934, and on the last of July 1934 being assisted by Messrs. K. KOBA, N. OBARA, I. NAGATU, N. ANDÔ, and K. SIBATA. Accurate observations of deep water temperature were attempted by means of a RICHTER & WIESE reversing thermometer attached to an EKMAN water bottle. The data obtained are given in Table. 5 (pp. 351-355). The effects of climate and lake morphology on the thermal conditions of these lakes appear to be alike in all of them. Since all these lakes, being situated in hollows are well protected from wind, the differences in thermal conditions in summer are due not to winds, but to another cause, namely the inflowing of cold spring and cold river water which, except in the case of Subalpine lakes, which are fed by turbid water of large rivers formed by melting snow, however do not as a rule play so great a rôle in Japanese lakes. We can easily classify them into three thermal types. _??_ The above figures are those for the last ten days of July, 1934. The Ôike Type corresponds to the thermal type of L. Hangetuko, the Otikutinoike type to the Oodairanuma subtype, and the Aoike type to the Tutanuma subtype of the writer, according to his published paper on thermal types of Japanese lakes in summer.(1) The Ôike type includes small and deep lakes with or without warm inflowing water that does not disturb the deep water temperature. The water of the bottom is very cold. A temperature as low as 3.88°C was observed at 25 meters in Ôike lake in July 1934. The Otikutinoike type includes on the other hand, those in which enter a large amount of cold water from the springs in the upper stream. The Aoike type corresponds to the thermal conditions of small spring ponds. Slight dichothermics were discovered in Lakes Aoike and Ôike in the Kosigutinoike Lake Group. That in the former is due to the inflowing of two kinds of springs with different temperatures and salinities at different levels. Although the latter is probably due to sublacustrine springs, it is probable that its warm bottom temperature is a sign of the autumnal warming of the previous year, a possibility recently proposed by FINDENEGG in the case of Austrian lakes. The water of spring ponds were blue and very transparent. A 25cm white disc was visible down to their bottoms (7 to 9 meters). Lakes withh poor phytoplankton production were green, and their transparency exceeded 5 meters. The maximum value in the summer was 8.3 meters. The transparency of lakes with abundant growth of Diatomn, chiefly Astrionella formos and Melosira granulata, were reduced to 2-3 meters. The most turbid water (transparency between 0.7 to 1.6 meters) was in Lakes Itobatakenoike and Gobônoike, due to thick water bloom of the blue algae Anabaena sp. Suspension of fine clay particles derived from the pearlitic tuff that composes the region also helped to reduce the transparency of all lakes of the Tugaru Zyûniko Lake Group.