Search

The article discusses the marine and ocean resources threats with the advancement of technology in the U.S. According to the author, technological advancement permits man to exploit the raw materials on the ocean floor beyond the traditional boundaries of national power and the government has difficulty in assuring protection over property rights in ocean and sea bed resources. He further asserts that there is no way of escaping reality that the degree to which mankind benefits from ocean resources is influenced as much by the interplay of national interests as by technology elevates. In conclusion, it states that if human improvement and world peace gains from the innovation of international organization, then ocean space furnishes unique opportunities that are in danger of being lost.

In this paper the effect of a fulvic acid fraction on the growth of a Pseudomonas sp. from fresh water is reported. The presence of fulvic acid in the culture medium caused an increase in the cell yield and in the cell yield per μl O2 taken up by the Pseudomonas. The observed stimulating effect has been explained in terms of co-metabolism of fulvic acid by the Pseudomonas. [ABSTRACT FROM AUTHOR]

Sieving efficiency, defined as the percent increase in yield of numbers or biomass of organisms, obtained by use of a sieve with 0.25-mm mesh openings instead of a 0.50-mm meshed sieve, was investigated in a lotic habitat over a 12-month period. Greatest efficiencies obtained were 300 to 600% for mayflies, chironomids, simuliids, ‘other dipterans,’ water mites and plecopterans and 90 and 190% for trichopterans and coleopterans, respectively. For the fauna as a whole, efficiency varied from 95 to 325% over the study period. Efficiency in estimating biomass was not as great as that with numbers and generally was below 10% for trichopterans, mayflies, ‘other dipterans’, coleopterans and the fauna taken as a whole. For chironomids, simuliids and water mites efficiencies generally were higher than 10% and reached as high as 174%, 60% and 80%, respectively. In all groups efficiency varies throughout the year with lowest occurring during winter months. The findings are compared with data found in the literature and discussed in relation to structural, behavioural, and life history characters. [ABSTRACT FROM AUTHOR]

The life cycles and sexual development of adult specimens of four Cenocorixa species were studied by quantitative sampling in British Columbia and Washington. Variation in the life cycles was found: a partial second generation, complete second generation, or a partial third generation was observed. This variation apparently reflects mostly differences in the latitude and temperature of the habitats. In general, all four species had life cycles that may be regarded as very much alike: the species are not asynchronous. When the nature of the habitats is taken into account, and the species are compared, there is no evidence of seasonal reproductive isolation between the four species studied. In the sexual maturity study, in all four species, overwintered males were mature at the time of ice break-up; new generation insects that occurred in early- to mid-summer, reached maturity by the time of emergence; late summer males remained immature until October-November, but reached sexual maturity before mid-winter. Sexual maturity in adult females was similar to that in the males, but overwintering females remained immature: ovarian maturation occurred after ice break-up in the spring. A consideration of the arrest in sexual development that occurs in both males and females suggests that photoperiod may not always be of major importance: nutritional factors may also be involved. [ABSTRACT FROM AUTHOR]

Hydrobiological studies were carried out on three Rhodesian reservoirs in 1970–71. Lake McIlwaine receives sewage effluent and has become highly eutrophic. Mazoe and Mwenje dams are not enriched, but Mwenje shows certain eutrophic features, probably because it is the most recently constructed. Seasonal variation was investigated and the three lakes conform to the warm monomictic type, with stratification in summer and isothermal conditions in winter. Most physico-chemical parameters follow this pattern, except in Mwenje which remains de-oxygenated in winter, probably because of trapped organic matter in the bottom waters. As a result, alkalinity, conductivity and pH also remain stratified in Mwenje during winter. De-oxygenation does not persist in McIlwaine despite its eutrophic condition, which appears to be a result of complete mixing brought about by its weak thermal structure and its open exposed morphometry. Mazoe shows no peculiar thermal features and the basic monomictic pattern is clearly defined in this lake. Diurnal variation of physico-chemical conditions was also investigated and found to be slight. No evidence of polymixis or hypolimnetic mixing was found. Phytoplankton populations in the three lakes are clearly related to their chemical nature. Lake McIlwaine has a large population of blue-greens, reflecting its eutrophic nature, whilst the other two have more diverse populations reflecting their mesotrophic status. Primary productivity, in turn, is related to phytoplankton populations. Productivity as measured by oxygen production is extremely high in Lake McIlwaine and is about three times higher than in the other lakes. [ABSTRACT FROM AUTHOR]

The distribution of Crenobia alpina, Polycelis felina and Phagocata vitta was examined in five streams in North Wales. The streams were chosen to include a range of gradients and temperature regimes in order to gain insight into the relative importance of these two factors in determining patterns of distribution. The significance of calcium content and pH of the water was assessed from a survey of ninety-three streams and limited observations on the oxygen content of a stream were also made. Laboratory experiments involving tolerance to high temperature and current velocity were carried out on each of the three species and the results were used in the interpretation of the field data. Phagocata vitta appeared to be confined to cool water of low calcium content (≤ 14.4 mg/l) in North Wales, despite its ability to live and reproduce in hard water under laboratory conditions. Crenobia alpina was shown to be capable of living permanently in cool springs with a gradient of 50 % whilst P. felina was limited to gradients of 27% or less in the streams investigated. In two of the streams examined in detail, where populations of C. alpina and P. felina were very important components of the fauna, species composition fluctuated dramatically alongside rapid changes in stream gradient. Crenobia alpina was dominant over P. felina on the steeper gradients whilst P. felina became the dominant species on gradients in the region of 16% and less in circumstances where the temperature regime could not have been the limiting factor for C. alpina. Interspecific competition appears to be an attractive hypothesis to explain the dominance of P. felina over C. alpina at low gradients in streams where high temperature is not limiting to either species, but further work is required on the food resources of these species to establish substantial food overlap. [ABSTRACT FROM AUTHOR]

The Upper Nile swamps lie in a flat featureless expanse of territory surrounded by a semicircle of hills and mountains. Rivers enter this area from Ethiopia, Uganda and the Nile-Congo divide, and have for thousands of years deposited sediments, mainly heavy clays. The rivers with a very slight slope are subject to heavy water losses by spill and evaporation. Three zones can be distinguished: permanent swamps which fringe rivers and standing water bodies; lands seasonally inundated by a combination of rising river levels and rainfall; and some dry ridges emerging a few metres above the flooded land. The vegetation is arranged correspondingly. Rivers, standing waters and temporal inundations have different characteristics both in their chemico-physicat make-up and their biological intensity. The most conspicuous difference is in the plankton; though the species are the same the densities in standing waters are much higher. The Bahr el Ghazal region shows a character of its own where richness of desmids indicates a peculiar limnological character. The role of currents in rivers is discussed, their complex differentiation creating varying opportunities for biological development. The region is inhabited by a number of Nilotic tribes whose annual life and migrations are dictated by the layout of the country and its hydrological regime. The higher vertebrate fauna is also adapted to the swamp conditions by composition (birds) or by migrations (mammals) as in humans. Two specific sections deal with the remarkable fauna of the floating plant Pistia stratiotes and the terrestrial fauna of umbels of Cyperus papyrus showing a succession from fresh to dry stage of the umbels. [ABSTRACT FROM AUTHOR]

Discusses the use of laboratory stream ecosystems in the study of stream ecology. Advantages in using the systems; Consideration for the conceptualization of stream processes or restriction of the application of knowledge; Function of laboratory streams.

The article presents an experimental study of the composition of the fallen leaves from terrestrial plants entering an aquatic environment. The experimental study was conducted to test the percentages of protein in the leaves, percentage of moisture and protein in the organisms and changes with the protein content. Findings in the six experiments depict a protein content increase with the elm leaves compared to the other leaves leading to the conclusion that different species of leaves behave differently. The article also cites several factors that signify the level of importance of autumn-shed leaves in bodies of water including the temperature and quality of water and the type of microflora presented in the leaf decomposition.

The article presents a study which examines the effects of oxygen balance to plants on rivers in England. It investigates the productivity of aquatic communities such as coral reefs in a chalk stream by measuring the changes in dissolved oxygen of water flowing over the areas. It offers analysis of diurnal dissolved-oxygen curves including the release of oxygen into the water as a result of photosynthesis by plants and the uptake of oxygen from the water due to the respiration of plants, animals and aerobic bacteria.

The article discusses a study which investigates the sublittoral seaweeds in Scapa Flow and Bay of Firth in Orkney, Scotland. The researcher has divided the study into three parts, which include the development of the view box, survey of the Scapa Flow and the survey of the Bay of Firth. Moreover, the researcher aims to determine the sublittoral seaweeds condition and develop preservations plan using the view box. Accordingly, using the view box method in the survey, the result indicates that it is possible to survey sublittoral zone with an increasing accuracy through small motor-boat. Moreover, the result shows that Laminaria species, which are common in Scottish coast, grow below 17 meters from sea level.

The article reports on the Rivularia bullata-balanus community. The occurrence of this community gives rise to a number of ecological considerations especially as featuring an instance of biotic reactions and as emphasizing the relevance of considering the sea shore as a biotic community or biome. The Rivularia genus propagates both by hormogones and spores and the hormogones provides an effective method for increasing the size of the colony and the formation of new colonies. This report of the Rivularia-Balanus community gives evidence of a study of both adelophycean stages and biotic relationships in attempting to clarify problems connected with marine ecology of the littoral region.

The article discusses the marine algal ecology and the factors that determine the distribution in British Isles. The main subject of the observation were the two reefs of rock at Peveril Point, to define the ecological position of marine algae species and their relation to the tidal flow. It was found that each dominant algal species has a definite range of exposure above or below, in which the amount of exposure has been calculated. It is cited that there is a problem with the bare zone that occurs between the Fucus spiralis and Laurencia-Corallina.

The article describes several external factors that govern the production of plankton in the sea. The three categories of these factors are nutritive factors proper, general conditions of life and indirect factors of production. Nutritive factors like light, heat, and inorganic food substances influence the speed of plankton growth, while indirect factors of production are responsible for the presence or absence within the limits of phytoplankton utilization. The vertical circulation caused by the up-welling of the sub-surface layers results to the presence of nutrient materials in the upper layers of the southern region of California.

The article presents the findings of the vegetation survey conducted at the Esthwaite Water in Lancashire, England in July and August 1914, and continued in August 1915. It is mentioned that the forces moulding lake shores have an important impact upon aquatic vegetation. Moreover, it was observed that wave-cut terraces are frequent in Esthwaite Lake, while reed-swamps and water-lilies are absent along the exposed eastern shore. Three different types of substrata found in the location are identified including substrata comprised of rock, gravel, or rounded stones; substrate where silting is in slight excess of the disturbing factors; and substrata where sedimentation is rapid and independent of disturbing factors.

The rotifer plankton was studied in some freshwater and brackish water localities in easternmost Central Sweden. Concerning the general character and rotiter plankton, some or the lakes agreed with the type previously studied e.g on the island of Gotland and designated as "oligotrophic — highly calcareous". Some of the lakes were recently separated from the sea, and in some others brackish water still intrudes at times. In such localities Synchaeta gyrina Hood was abundant. This rotifer evidently constitutes an edge species between brackish and fresh waters In the purely brackish localities, on the other hand, the species composition was similar to that found elsewhere in Baltic zooplankton. [ABSTRACT FROM AUTHOR]

Numbers of Potamothrix hammoniensis (michaelsen) varied between 10,000 and 25,000/m² over six years (1954-1960) in the profundal of the eutrophic lake Esrom, Denmark. Dry weight equivalents of preserved specimens varied between 0.75 and 1.80 g/m². Cocoons, deposited from late May to July, hatched in August. Growth was most rapid in autumn and spring and no weight increase occurred during summer stagnation. Reproductive individuals were, in some cases, three years old, but most were four. Total life span was at least five years. Reproduction of P. hammoniensis was related to numbers of Chironomus anthracinus Zett. When the Chironomus population was large the reproduction of P. hammoniensis was lowered. [ABSTRACT FROM AUTHOR]

In order to detect sublethal poisoning in living fish, they are subjected to flowing water that is caused to rotate in a narrow tube around the direction of flow. On acceleration from zero to the maximum number of revolutions per minute (40 or 60 r.p.m.) the "critical r.p.m." is that at which the fish is unable to compensate for the torque and is forced to rotate. Sublethal poisoning with methyl-mercuric hydroxide (MM-OH) significantly decreases the critical r.p.m., as does a stay in captivity without food. The decrease in the critical r.p.m. of fishes exposed to MM-OH is linearly correlated to the amount of mercurial found per unit wet weight of muscles. [ABSTRACT FROM AUTHOR]

A qualitative and quantitative investigation of the bottom fauna was made in spring and autumn in the years 1961 to 1963 in polluted areas of the southern Sound (between southern Sweden and Zealand). The quantitative samples were taken with a 0.1 m² Smith-McIntyre spring loaded mud sampler. The purpose was to establish the present condition of the bottom fauna and to calculate the faunistic changes over a longer period compared with previous investigations. Moreover the purpose was to give an exposition over the effect of pollution on the bottom fauna and to examine the value of certain organisms as indicators of pollution. This part deals with the present condition of the bottom fauna. In Tab. 1 a survey is given of the situation of sampling stations, the types of bottoms, the depths and the bottom vegetation. A statement of the investigation has been given in Tab. 2 and Figs. 3 to 11 on the content of the fauna, distribution, vertical extention, number of individuals and biomass. [ABSTRACT FROM AUTHOR]

1. The rate at which adult individuals of Marisa cornuarietis prey on adult and juvenile Bulinus truncatus and Lymnaea caillaudi increases with temperature up to about 30°C, then decreases slightly again. 2. This predatory activity normally decreases to some extent in presence of abundant vegetable material edible to the predators. 3. It seems that adult Marisa, while preying on Bulinus and Lymnaea, develop a certain progressive predatory habit, and that with the development of such habitual predation their attack on both these snails becomes less affected by the presence of vegetable food. 4. The rate of predation is more or less directly proportional to the ratio of predators to prey, and is far less affected by population densities. 5. Adult and juvenile Marisa are capable of preying freely on newly hatched individuals of Bulinus, Biomphalaria alexandrina and Lymnaea. There is strong evidence that Marisa ingest whole such very small individuals. With larger specimens, they attack only the soft parts. In the case of Biomphalaria, however, Marisa can only devour small specimens with shell diamater less than 5 mm. 6. Adult Marisa are capable of consuming the egg-masses of the three vector snails investigated and with a greater voracity than do newly hatched and juvenile individuals of Marisa. 7. The predation of Marisa of all ages on the egg-masses and newly hatched individuals of Bulinus, Biomphalaria and Lymnaea does not take place only accidentally while the predators are browsing and feeding on aquatic plants, but also deliberately. 8. It seems probable that Marisa of all ages are capable of reducing considerably Bulinus, Biomphalaria and Lymnaea populations. [ABSTRACT FROM AUTHOR]

1. The present paper deals with the effects of river regulations on the fauna living in the rapid regions of the River Stora Lule Älv, which is influenced by the Suorva Reservoir since 1927. The conditions in the natural river system of the river Lilla Lule Älv are compared. 2. The changed rhythm in which the water runs off caused by the regulation is explained by several examples of natural rivers. 3. As opposed to the unregulated river Lilla Lule Älv the river Stora Lule Älv shows anormal glaciation whith radical influences on the topography of the river bottom and its flora and fauna. 4. The damming up of snow and glacier melting waters cause essential divergences from the natural development of temperature in regulated rivers, disturbing the vital function of the organisms. 5. Investigations on the way in which the waters run off dammed and natural lakes show, taking into consideration the »Organic Drift« and the bottom fauna, the negative consequences of the regulation on the rapid regions below power dams. 6. An experiment at the power dam of Selsforsen showed that by taking plankton rich surface water also below power dams a rich bottom fauna can live in the river. [ABSTRACT FROM AUTHOR]

The present investigation gives a quantitative view of subaquatic meadows in Ösbysjön (Lake Ösby), Djursholm, Stockholm. The species investigated are: Nitella mucronata, Chara fragilis, Ceratophyllum demersum and Myriophyllum verticillatum. Standing crop and production have been studied and some analyses of the plant ash performed. Chara has the highest figure for standing crop with 1,130 g/m² (oven-dry weight). Lower values are noted for Ceratophyllum (680), Nitella (310) and Myriophyllum (240). The high figure of Chara is mainly due to calcareous incrustation. The highest productivity data, as average values per period (oven-dry weight), also are for Chara (8.6 g/m²/day) while Nitella has the lowest (2.5). In the autumn when dissimilation is greater than assimilation the data are negative: Chara (-2.0) and Nitella (-0.9). The figures of productivity show that subaquatic vegetation of this type has a rather low production rate. But the production of organic matter per square meter in the meadows can exceed the production of phytoplankton per square meter by 3 to 4 times. The weight of Ca in Chara is compared with the total weight of the same constituent in the water. During a period of 70 days, 800 kg Ca disappear from the water, while the Ca in Chara during the same period increases by about 1,000 kg. The content of phosphorus in Chara and Nitella has been estimated and the figures are compared with the total weight of phosphorus in the water. The total content of phosphorus in the two species is nine times greater than that in the entire water body of the lake when the standing crops reach their maxima. The two species cover together one fourth of the lake area. The concentration factors for phosphorus show that the element in these plants is concentrated 4,400–6,700 times more than in the water. [ABSTRACT FROM AUTHOR]

The article studies temporary variations in certain marine ceratia. It was early recognized that such changes were influenced by external conditions, and it was assumed that a certain adaptation to the external conditions took place by readjustment of the buoyancy of the plankton organisms. It was discovered that the rate of sinking is directly proportionate to the preponderance in weight and inversely proportionate to the shape resistance, or the external frictional resistance, and to the viscosity of the water. The latter factor mainly depends on the salinity and the temperature of the water. Researcher Steemann Nielsen has discussed various factors that may be assumed to play a part in the variations in the ceratia. Besides the assumption of direct dependence on temperature variation, other factors are suggested as forces likely to influence the change in size, viz., oceanic-neritic influences, the amount of nutrient salts and the quantity of plankton, the salinity, and the density of the water varies with the temperature and the salinity. The variation in size of ceratia and the dependence of the change on external factors have subsequently been dealt with by several investigators.

The article focuses on some laboratory experiments on the Coccolithophorid Coccolithus Huxleyi. Pontosphaera huxleyi occurs in the Atlantic and the Mediterranean in great numbers. Three unialgal clones were used: two from the Marine Biological Laboratory, Plymouth, and one from Weather ship in the Norwegian Sea. Schreiber sea water with soil extract was used as culture medium and both fluorescent tubes and ordinary incandescent lamps as light sources. A preliminary experiment showed that the growth rate was uniform as long as the population did not exceed 300,000 cells per ml. Experiments with diffuse fluorescent light and with a light beam, in different cases, recorded phototactic movement and an accumulation of cells in areas where the light intensity was from 600 to 5000 Lux. Experiments, mainly by changes in light intensity and nutrient supply, were undertaken to induce the formation of coccoliths in naked cells, but without positive results. The experimental results obtained with these coccolith-free or coccolith-poor cultures may not be representative for populations which have abundant coccolith formation.

The article discusses the specializations of habitat of fresh-water organisms such as benthos, chaoborus, and zooplankton. It states that forms of life in water is determined by environmental factors such as temperature, dissolved gases, and light besides other physiochemical and biological factors. Seasonal rhythms and nutritional changes, food cycles, and direction of flow of water determines the population of the organisms in that ecological zone. It suggests that the number and variety of organisms also depends on the volume, area, age, and location of the bodies of water.

The paper presents information on factors influencing maximum feeding-rates (measured in the laboratory) in larvae of the damselfly Pyrrhosoma nymphula, and compares estimates of feeding rates in the field with maximum feeding-rates for larvae of the same size at the same temperature. Maximum feeding-rates in Pyrrhosoma larvae of different sizes were measured at 4, 5, 10 and 15°C. At low temperatures (4–5°C) maximum feeding-rate was depressed more than predicted either from the effects of temperature on the gut-clearance time of larvae or their respiratory rate. Maximum feeding-rate declined steadily throughout metamorphosis in the final instar and stopped completely prior to emergence of the adult. Feeding-rates in the field were calculated from ‘balanced’ energy equations, i.e. from the sum of larval growth, respiration and the production of faeces and exuviae. Feeding rates in the field were always much less than maximum feeding-rates for the same size of larva at the same temperature, and at the most were never more than 70% of the latter; they were closer to the maximum in summer than in winter, when they fell as low as 20% of the maximum. The relevance of these findings to studies on the efficiency with which carnivores utilize energy in the field, and the importance of Odonata larvae as predators in aquatic ecosystems is discussed. [ABSTRACT FROM AUTHOR]

Five species of helminth parasites were found in adults and tadpoles of the newts Triturus helveticus, T. vulgaris, and T. cristatus, caught at eight different localities in Somerset. These parasites were Acanthocephalus anthuris, A. ranae, Megalobatrachonema terdentatum, Thominx filiformis and Oswaldocruzia molgeta. Mean worm burdens did not change through the year, and egg-producing females of Acanthocephalus anthuris and Megalobatrachonema terdentatum were found throughout. There was no difference in the level of infection of male and female newts. [ABSTRACT FROM AUTHOR]

Fewer species and more individuals of Tubificidae were present in the soft sediments of a polluted ditch than in the relatively unpolluted Bere Stream. Changes in width frequency of natural populations of Tubifex tubifex and Limnodrilus hoffmeisteri throughout the year were similar at both the sites investigated. In laboratory experiments larger populations of Tubifex tubifex developed in fine sediments than coarse. By means of a width-dry-weight relationship it was possible to estimate the weight of the experimental populations. [ABSTRACT FROM AUTHOR]

In the present paper four species of water-mites belonging to four genera previously unrecorded from Britain are described and figured. The genera belong to four different families. The female of Azugofeltria motasi Schwoerbel 1961 is described and figured for the first time. The species discussed were found in samples of water and detritus taken from the interstitial (phreatic, hyporheic) habitat of exposed, superficial riverine gravels using the technique of Karaman/Chappuis (see Gledhill, 1969). [ABSTRACT FROM AUTHOR]

(1) Analysis of data from samples of chub taken at monthly intervals from two tributaries of the Herefordshire Wye revealed an annual cycle of scale growth with the formation of a check during May or June. The frequency distributions of ages determined from scale checks and the length-frequency distributions showed close similarities. It was concluded that age determinations based on an examination of the scales were valid, provided care was taken in the identification of the first scale cheek. The maximum age observed was 15 years. (2) Examination of the population structure revealed an overall sex ratio close to unity but there was a significant increase in the proportion of females in the 11+ and older age groups. Dominant year-classes were observed. The strongest was 1959, which was attributed to exceptionally warm, dry, sunny weather during the period May–September. (3) Female chub grew more rapidly and attained greater ultimate size than the males. Changes in the pattern of growth during the life-span were attributed to the attainment of sexual maturity, especially in the females. The length-weight relationships of the sexes differed slightly but were almost identical for the same sex in the two rivers studied. Seasonal variations in the growth-rate were followed. Most rapid growth occurred after check formation in May or June and continued until September. [ABSTRACT FROM AUTHOR]

A typical marl lake of the Upper Great Lakes region has very few quantitatively important aquatic macrophytes. The macrophytes, however, dominate the total primary production of the lake. Submersed vegetation is extremely sparse on the shallow (less than I m) marl bench that characterizes the littoral of these lakes, and is completely dominated by one. little-known species (Scirpus subterminalis Torr.) between 1 and 7 m. A detailed investigation of the spatial and seasonal distribution of macrophytic species and biomass showed that S. subterminalis strongly dominated the lake (79% of total biomass). S. subterminalis represented an almost pure stand (to 200 g m-2 mean annual ash-free dry weight) at all times of the year at intermediate depths of macrophytic growth (1–6 m). Two species of Chara (of eight varieties and forms) were present in significant quantities (12% of total biomass; to 100 g m-2) but were severely limited to shallow depths (0.5–1 m) and protected areas. Several annual submersed angiosperms were present (9% of total biomass), but only two species were quantitatively important. Potamogeton illinoensis Morong, and P. praelongus Wulfen formed brief summer peaks (less than 100 g m-2) at 3 and 4–6 m, respectively. A striking feature of the seasonal biomass distribution of Scirpus subterminalis was the higher, viable biomass (to 150gm-2) throughout the winter under ice cover. Cyclic fluctuations of the S. subterminalis populations were discerned at different depths, each with different periodicities. The population at 2 m exhibited a fall peak; that at 4 m had a summer maximum. The lowest overall biomass of S. subterminalis occurred in the 2 m population in June. Chara populations at 0–2 m also exhibited a relatively constant biomass throughout the year. The appearance of Nitella at 7 m in July–October and of Chara at 5 m in September-October was interpreted as an interaction between light, thermal, and carbon stratification. Estimates of macrophytic productivity of perennial (‘evergreen’) species populations whose biomass remains relatively constant throughout the year were made employing several different methods of calculation and turnover factors. All methods resulted in productivity estimates in good agreement with the conservative value of 178 g m-2 year-1 for the entire lake. In comparison to the other components (phytoplanktonic, epiphytic and epipelic algae) of the primary production of Lawrence Lake, the aquatic macrophytes constituted a major portion (anuual mean 82.77 g C m-2 year-1 or 48.3 %) of the total production of the lake. The low diversity but relatively high quantitative importance of macrophytes in marl lakes is attributed to an adverse dissolved inorganic and organic chemical milieu which inhibits phytoplanktonic production and allows only certain adapted macrophytes to develop strongly. The phenomenon of perennial biomass levels throughout the year is believed to be much more common than previously suspected and has likely resulted from adaptations of submersed macrophytes to ameliorated conditions of water and temperatures relative to the terrestrial situation in winter. [ABSTRACT FROM AUTHOR]

Actinomycetes of the family Actinoplanaceae, especially Actinoplanes, are readily isolated from the flowing waters of local rivers and streams and it seems clear that such lotic environments are favoured for colonization by these organisms. In this contribution evidence is produced that part at least of this activity can be ascribed to the utilization of wood as a growth substratum. Some other aquatic Actinomycetes of less certain affinity were also shown to be capable of growth on wood, under the conditions of pure culture. [ABSTRACT FROM AUTHOR]

The article reports on the study conducted on the impact of nuclear explosives in constructing a sea-level canal in Panama. The main objective of the study is to provide estimates of the potential internal intake of various radionuclides by indigenous populations in the areas contaminated by the fallout from nuclear excavation of a canal. Researchers found that these radionuclides would be redistributed by ecological processes and transported to man in the form of contaminated foods and water. Discussed are the details of the experiment.

The article reports on the study conducted in the U.S. on the impact of radionuclides to terrestrial and aquatic environments in the sea-level canal in Atlantic-Pacific. Researchers use the specific activity approach proposed by the National Academy of Sciences in predicting hazards from radioactive fallout and contamination. Studies reveal that marine foods accumulate relatively small amounts of phosphorus per unit wet weight, and because small amounts of the element are ingested by man as compared to his total body weight, the rate of addition of the element and its radionuclide is sufficiently small to allow the human body pool to significantly dilute the added nuclides.

The article focuses on the freshwater ecological studies conducted in eastern Panama and northwest Colombia. These studies were designed to acquire the necessary data for the evaluation and prediction of the potential radiation dose to indigenous populations in regions proposed for sea-level canal nuclear excavations. An analysis of the ecosystem is considered the most realistic method of estimating the potential radiation dose to human populations living in or near the likely fallout contamination areas. However, there are more conservative but still acceptable approaches to this method of analysis, including the specific activity concept and the concentration factor concept.

The article focuses on the possible biological effects of the planned sea-level canal to be built in the vicinity of the Isthmus of Panama. Several ecological studies have stated that the new infrastructure would affect a number of marine invertebrate species that are inhabiting the deep and shallow waters of the region. Studies also state that the presence of canal will change the tidal currents in the area which will enable marine animals to migrate in either direction, affecting the species diversity and ecological balance.

The article discusses the results of several studies which examine the excretion of dissolved organic compounds (DOC) by aquatic macrophytes. Researchers have noted that the kinetics of the algal excretion of DOC vary markedly in relation to light intensity, carbon availability, and other factors. It states that these variations are of particular significance to the complex relationships among the inorganic and dissolved organic composition of lake water, nutrient cycling, and a host of bacterial and algal metabolic interactions. Results of analyses suggest that the exosmotic excretion of DOC by aquatic macrophytes demonstrate relatively high rates of photosynthesate loss.

The author presents the outline of the proposed classification of animal habitat which is believed to be useful for zoological study. The author compellingly posits that the proposed classification meets the qualifications as it is existing in Eastern Canada, and welcomes further criticisms, discussions and necessary amendments of the proposal from ecologists. The classification proposal is mainly divided into four categories of animal habitat which are hydrotheric formation or fresh water, thalassitheric formation of marine, helotheric formation or marshes land and poitheric formation or grass-land.

The article reports on the experiment conducted at Bristol Bay, Alaska by researchers James F. Fish of the Naval Undersea Research and Development Center, and John S. Vania of the Alaska Department of Fish and Game on underwater sounds. Fish and Vania have discovered that underwater sound could be effectively used in preventing white whales, or belugas, from entering the Kvichak River. An underwater sound projector was used to test the effectiveness of underwater sound for stopping the invasion of the belugas into the river. In addition, playback of killer whale vocalization was 100% effective in keeping the whales down river.

The article presents information on the biological characteristics of estuaries in the U.S. It cites that there are about 900 estuaries of interaction between land drainage and the ocean. According to the article, estuaries are complex and challenging, and they serve more human uses than any other kind of aquatic entity. It further states that the biological system of an estuary is vulnerable to environmental changes which have not been within the experience of the species involved. Moreover, threats to estuaries are the changes which may damage energy flow, community structure, or species success.