Freshwater Areas Research Articles

Prevalence of the kidney worm (Gnathostoma miyazakii) in river otters (Lutra canadensis) in Virginia

The overall prevalence of Gnathostoma miyazakii Anderson, 1964 in 368 river otters (Lutra canadensis) from Virginia was 52.45%. Neither sex nor age of otters significantly affected prevalence of G. miyazakii. More (P < 0.005) otters were infected from saltwater areas than from freshwater areas of the state. Kidney weights of infected otters were significantly (P < 0.05) higher than those of noninfected otters.

Incidence and level of Vibrio parahaemolyticus associated with freshwater plankton.

We isolated Vibrio parahaemolyticus from plankton samples collected from different freshwater areas in the vicinity of Calcutta, India. Levels of this organism in association with freshwater plankton were low (less than 90 organisms per g). All of the 16 strains of V. parahaemolyticus isolated in this study were Kanagawa negative, and all except 1 were untypable. The occurrence of V. parahaemolyticus in association with freshwater plankton suggests that adsorption onto plankton may aid the survival of this moderately halophilic organism in freshwater milieus.

Characteristics of Peat Deposits in Mississippi River Delta Plain: ABSTRACT

Variations in organic-rich sediment (peat) from the Mississippi River delta plain can be explained by differences in three interrelated parameters: (a) depositional setting, (b) balance between subsidence and detrital influx, and (c) marine inundation. Variations are observed in geometry of the overall deposits, organic matter content, and the mineralogy of peats and related ashes. Using a vibracorer, samples were collected from two brackish areas (Avery Island/Sale-Cypremort and Barataria basin) and one freshwater area (Gueydan). Geometries of the deposits are different for the two brackish settings; interdistributary peats of Barataria basin tend to be discontinuous and somewhat thicker than blanket peats of Avery Island/Sale-Cypremort. The freshwater peat is an elongate body in a Pleistocene channel cut. Peats in all areas average 90% moisture content. Dried peat averages 81.3% organic matter with a bulk density of 0.12 g/cm3. Holocene differential compaction has been minimal (< 4%). Conventional ash values indicate different distributions of organic material for the two brackish areas. For the area containing interdistributary peats, approximately 5% of the subsurface contains more than 70% End_Page 1466------------------------------ organic matter, whereas for blanket peats, 14% of the section has more than 70% organic matter. Mineralogic data collected on low-temperature ashes indicate that major minerals in brackish peat consist of kaolinite, quartz, and water-soluble salts, whereas minerals from freshwater samples are primarily kaolinite and quartz. X-ray diffraction and electron microscopy show the presence of smectite, illite, abundant siliceous spicules, framboidal pyrite, biotite, pyroxene, and rutile in the insoluble fraction. Suitability of these deposits as coal precursors has been discussed by several workers. Superficial examination of data generated so far suggests that only thin coal seams with high ash would be produced. However, the presence of decomposing siliceous sponge spicules in the ash and the possibility of ash being leached by fresh ground water, suggest that much ash may be lost during early diagenesis. Hence, this environment may have more potential as a modern coal-forming model than it first appeared. End_of_Article - Last_Page 1467------------

Studies on the juvenile Japanese sea bass in the Chikugo estuary of Ariake Bay. Changes in distribution pattern and condition coefficient of the juvenile Japanese sea bass with the Chikugo River ascending.

The research on the juvenile Japanese sea bass in the Chikugo River estuary of Ariake Bay is proceeded from 1979. In this paper, we examined the changes in the distribution pattern and the condition coefficient with the ascending progress, mainly using the data obtained in 1980. The researches of seven days in total were executed in mid March, late March and mid April. Surface towing by a larva net with 1.3m in a diameter and environmental observations were performed at seven stations set from the estuary to the river basin. 1) A total of 5314 postlarvae and juveniles were collected by 183 tows. As the researches proceeded, the mode of the distribution moved from higher to lower salinity. 2) The mean of standard length during each research was 14.6, 16.1 and 20.1mm, respectively. The ratio of body depth increases in proportion to the length growth and after 20mm in standard length, the ratio keeps stable. Condition coefficient continues to increase with a gentle curve for a while after 20mm. 3) We could not examine an actual distribution of sea basses only in reference to the salinity in the research area. The concept of distance was introduced to the temporal changes in catch and salinity in 1979. In the year 1979, the continual samplings at each station were performed. 4) In mid March, sea basses were mainly distributed in the sea side of the boundary zone between sea and fresh river waters. In mid April, half the number had already reached the fresh water area. Individuals in the fresh water area had considerably increased the condition coefficient. Changes in body length and condition coefficient under ascending a river were examined. 5) Remarkable change in catch when the tide is turning at high or low tide and more catch during rising than during ebbing tide were observed. It may be said that the sea basses display alternative distribution patterns dependent on tidal levels and tidal hours. Preliminary notes on the ascending mechanism of the sea basses were given.

Vegetation and man in the Basin of Mexico

The Basin of Mexico (Fig. 1) lies at an elevation of about 2,000 m. Surrounded by mountains on the east, south and west, it receives drainage from all directions, but drainage from the north is less. As a consequence of continued input and no outlet from the Basin, water accumulated in the past in the valley to form 5 large, shallow lakes during the dry seasons. During the period of historical observation, these at least partially coalesced, particularly during heavy rainy seasons. Generally, the level of the lakes at the time of Spanish Conquest is stated to have been 2,240 m. In the historic period, a drain was opened to the north to reduce the lakes to their present condition. Colonial period accounts (Rojas et al., 1974) indicate that various causeways constructed prehistorically were still functional in providing overwater access to Tenochtitlan (Mexico City) and in separating the waters of Lake Texcoco (Fig. 1) into an eastern saline body and a western fresh water area as well as separating lakes Xochimilco and Chalco. Fresh water from the mountains to the west and south provided a flow which made possible the utilization of the lake water for intensive farming with the development of the unique chinampa system (Armillas, 1971). The lakes of the Basin of Mexico made the area very attractive to prehistoric people who found game animals plentiful and useful plants from a number of different associations within easy reach (Lorenzo et al., 1975). With development of cultivation, undoubtedly around the margins of the lakes initially, the Basin became the site of one of the earliest urban populations in the Americas. However, in order to understand the development of a burgeoning population it is necessary to provide the biological background in which this developed.

A search for fucoidan-degrading bacteria in coastal sea environments of Japan.

Fucoidan-degrading bacteria were isolated by duplicate elective precultivations accompanying surface inoculation procedure from various samples from coastal sea areas. Fucoidan employed was prepared from a brown seaweed Nemacystus decipiens, and the medium used here consisted of inorganic salts, fucoidan as carbon source, and extract of sea bottom mud. In total32 isolates were obtained from 396 samples, and sea bottom sand and mud were good sources for isolating. It seemed most likely that the great part of the isolates (28 strains) belonged to the genus Vibrio, but the genus of a few isolates (4 strains) was unknown. The isolates could utilize 41% to 84% of the fucoidan in the medium in a 4-day incubation period at 25°C. Cell extract from a repre-sentative isolate of Vibrio sp. conversed about 30% of fucoidan to fucose in exhaustive digestion. On the contrary, no fucoidan-degrading bacteria were found in 213 samples collected from land and freshwater areas.

Karyological and gonadal sex of eels(Anguilla anguilla) from the German Bight and the lower River Elbe

Yellow eels(Anguilla anguilla) taken during summer from random commercial trapnet samples in the littoral area of Helgoland (n=116) and from a freshwater area of the River Elbe near Hamburg (n=109) were examined with regard to their karyological (i.e. existence of female sex chromosomes) and gonadal sex. In 47 % and 21 % of the two samples, respectively, chromosomes were unidentifiable because of insufficient numbers of mitotic plates. All eels from Helgoland, except one phenotypically undetermined fish, exhibited female gonads: 48 had female sex chromosomes and 13 were karyologically males. As found previously in the River Elbe, eels with male gonads predominated (n=55); 25 were undifferentiated. Of the gonadal males 26 were karyological males and 16 karyological females; the rest could not be identified by chromosome patterns. In contrast, all but one of the Elbe eels with female gonads (n=28) had female sex chromosomes. Some aspects of the sex reversal documented in the eel are considered.

Orbital Sensing of Mackenzie Bay Ice Dynamics

Satellite images are a useful tool in the study of sea ice dynamics. The results of studies using satellite images of Mackenzie Bay during the break-up and freeze-up periods are presented in maps and tables. These indicate important temporal variations in the processes of bay ice break-up and freeze-up. Though the Mackenzie Bay break-up proceeds from the south and from the north, the southern melt rate is faster because of an influx of warm water from the Mackenzie River. The freeze-up proceeds from south to north, i.e., from the fresh water area to the saline water area of the bay. The study of Mackenzie Bay ice dynamics is important because of the barge traffic through the Mackenzie River and also because of offshore drilling activities in the Beaufort Sea.

Sources of heavy metals in sediments of the Hudson river Estuary

Abstract Sediments in the Hudson Estuary contain zinc, copper and lead from metal pollutants discharged to the harbor in the New York City area, from dispersed sources of contamination introduced upstream, and from natural weathering processes. The magnitude of the contribution from each of these three sources to particular sites can be estimated on the basis of total metal abundances, relative proportions of several metals, and other sediment properties. The pattern of recent heavy-metal contamination in Hudson sediments closely follows the distribution in sediments of 137Cs which was derived over the past two decades from global fallout and local releases from a commercial nuclear reactor. Several simple empirical corrections related to grain size and mineralogy variations are suggested for comparing heavy-metal contamination levels of sandy continental shelf sediments with fine-grained estuarine and coastal sediments. Iron has little variation in Hudson sediments while manganese is greater in surface sediment of some low-salinity and fresh-water areas than deeper in the sediments, and generally less in the high-salinity area of rapid sediment deposition in New York harbor. Much of the pollutant Cu added to the harbor appears to be rapidly deposited in the sediments.

TWO TROPHIC GROUPS OF BACTERIA, OLIGOTROPHS AND EUTROPHS: THEIR DISTRIBUTIONS IN FRESH AND SEA WATER AREAS IN THE CENTRAL NORTHERN JAPAN

Two groups of bacteria were determined as oligotrophs and eutrophs. The former can grow only on a poor medium and not on a rich medium, and the latter can grow on a rich medium. Based on such trophic nature of bacterial groups, a method was established for counting viable cell number of oligotrophs and eutrophs, employing poor and rich media. The present method was used to examine water samples of fresh and sea water areas including rivers and lakes in Toyama Prefecture, off the coast of Toyama Bay, and open sea area at Yamato Bank in the Japan Sea. Physical and chemical environmental factors in these areas were also estimated. Based on the result of an extensive survey on these oligotrophic and eutrophic water samples, two general conclusions were deduced: (a) Oligotrophs and eutrophs responded quite similarly to respective chemical environmental factors, and (b) the number of these trophic groups remained almost constant at even higher concentrations of these factors. In fresh water areas, the number of oligotrophs usually exceeded that of eutrophs, and limiting substances for the size of these bacterial populations were considered to be nitrate-nitrogen and dissolved organic nitrogen. From the effect of rainfall on the number and trophic flora of bacteria in a river, the source of river bacteria was suggested at least in part to be attributed to the soil bacteria.

Additional Range Expansion in Florida of the Introduced Walking Catfish

In April 1975, the Walking Catfish (Clarias batrachus) was known to be established in ten counties of Florida. The present range of this exotic species covers 18 counties or somewhat more than 25 % of the freshwater area of Florida, and this has happened in the ca ten years since the first specimens were found in the wild. Severely cold winters have failed to stem range expansion, and future northward migration in peninsular Florida can be expected.

Toxicity of alkyldinitrophenols to some aquatic organisms

The toxicity of alkyldinitrophenols to juvenile Atlantic salmon increases with increasing octanol-water partition coefficient of these compounds. Some alkyldinitrophenols are extremely toxic to juvenile Atlantic salmon, larvae and adult lobsters, but comparatively nontoxic to crayfish. The unexpected low toxicity of dinoseb to crayfish is interesting also from the point of structure-activity relations and emphasizes the need of testing these in different species of aquatic fauna. No data are available on the levels of alkyldinitrophenols in fresh water, estuaries, and coastal areas. There is an indication that at least in certain streams the concentration may temporarily exceed many times the lethal threshold and have a severe impact on aquatic life. Alkyldinitrophenols are not likely to be bio-accumulated and biomagnified and their presence would not be detected by analyses of aquatic fauna. A detailed survey of their levels in surface waters, linked to their usage patterns, should be carried out.

Concentrations of copper, iron, lead, nickel and zinc in freshwater algal blooms

The concentrations of copper, iron, lead nickel and zinc in algal blooms from freshwater areas near zinc smelting wastes in the Lower Swansea Valley have been compared with metal levels in algae and waters from areas outside the valley. The metal concentrations of the blooms are considered with respect to: (i) their nature and origin; (ii) metal levels in the water and (iii) algal uptake and concentration factors. It is concluded that most of the differences in algal metal content are related to environmental effects. The measurement of metal concentrations in freshwater algae to indicate the presence of environmental metal is discussed and a monitoring technique outlined.

Science for Canada’s Fisheries Rehabilitation Needs

A brief, generalized review of the current status of salmonid fisheries on the west and east coasts, and of selected representative waters in the freshwater area is presented. It is concluded that many fish communities and/or fish stocks are depressed, collapsed, or extinct as a result of severe stresses imposed directly, or indirectly, by man’s activities. Rehabilitation of fish stocks and fish communities to levels approximating those of early years, and to levels capable of supporting more stable yields to meet growing client requirements appears practical. The need for explicit policy decisions with regard to sea ranching and rehabilitation as options for approaches to increasing fish abundance is stressed. Rehabilitation of stocks and communities will require additional science in areas such as hatching, rearing and selective breeding, fisheries engineering, and in the more precise definition of natural productive capacity of waters. Effective fisheries rehabilitation programs, and fisheries management generally, require: development of fisheries information systems; an adaptive or experimental approach; more social and economic data; synthesis and communication of science available; and fundamental reconsideration of the traditional institutional arrangements for fisheries work. Some important fisheries rehabilitation programs, carefully planned and assessed, can proceed immediately with confidence in their success; others must await improvement in water quality.

The vertical distribution of some West African mosquitoes (Diptera, Culicidae) over open farmland in a freshwater area of the Gambia

AbstractMosquitoes flying at low levels over open farmland were sampled by means of electrical suction traps. These were set up at nine levels from ground level up to 6 m. From the vertical profiles obtained it was possible to recognise three patterns of behaviour: (1) a low-flying group with relatively very high densities below 1 m, comprisingMansonia (Man-sonioides)spp.,Aedesspp. and some species ofAnopheles; (2) an intermediate group with densities rather evenly distributed at the lower levels but declining above 2–4 m, comprisingA. funestusGiles,A. gambiaeGiles andCulex neaveiTheo.; (3) a high-flying group with catches at 6 m greater, or much greater, than at 1 m, composed ofC. antennatus(Becker),C. thalassiusTheo. andC. poicilipes(Theo.). For all species, catches after 23.00 h showed an increase in the proportion of mosquitoes taken in traps at the lower levels, this being most marked at ground level and 0·5 m. No influence of either moonlight or wind speed could be detected to account for this. Biting catches on human baits showed a generally similar pattern to suction-trap catches, although differences between baits at 1-m intervals at the higher levels were less than with unbaited traps.

NUMERICAL MODEL FOR DENSITY CURRENTS IN ESTUARIES

In the estuarine mixing areas of salt water and fresh water the vertical stream velocity profile generally is strongly affected by the baroclinic forces, giving rise to upstream currents near the bottom. Such reverse currents occur not only in stratified estuaries, but also in estuaries of the well-mixed type |1|, and they may cause problems like strong shoaling areas, salt intrusion, or difficulties when disposing wastes or dredged material |3|. The contributions of the salinity variations to the tidal motion are comparable to the contributions from the fresh water upland discharge |1|. For well-mixed estuaries with negligible fresh water discharge, the tidal velocities and water elevations may be obtained from numerical vertically averaged models or from physical homogeneous-flow models, but for all other conditions or desired results one has to use numerical vertically discretized models or physical inhomogeneous-flow models. As numerical and physical models have different properties and deficiencies, they may be used complementarily rather than concurrently |4|, the farfield regime apparently becoming the domain of numerical models. The increased public and scientific interest in water quality problems led to the development and application of baroclinic numerical tidal models |5, 6| . The present paper is concerned with the question, how well the action of baroclinic forces can be represented by numerical techniques. As a test example, the salt wedge problems is tackled. Studies on salt wedges by means of physical models have been very sucessful |1, 7|, but mathematical approches were confined to analytical solutions for the stationary salt wedge |8 - 10| and simple geometric boundaries only. The numerical approach is free from these restrictions, giving a solution of the complete equations of motion, continuity, and convection-diffusion simultaneously.

Loch Lomond: Man's Effects on the Salmonid Community

Loch Lomond, the largest area of fresh water in Great Britain, has been utilised by man for many hundreds of years. There are fifteen species offish at present in the loch: all of these are native. Several of them have formed the basis of commercial and sport fisheries in the past but the only two species of importance at present (as sport fish) are salmon (Salmo salar) and trout (Salmo trutta). Man has influenced the loch in ways other than fishing: several fish species have been introduced (none successfully); nutrient input is increasing; loch water is used for domestic and industrial supply; many forms of recreation take place on the loch; and it is of major importance as an amenity. In spite of these stresses there is no indication of any major change in the fish populations within recorded time; nor is there any evidence that they will alter in the foreseeable future, providing a rational conservation programme is developed for the area.

Artificial radioactivity in freshwater and estuarine systems.

The nature and origin of artificial radioactivity in freshwater and estuarine environments are described and the situation to the end of the century, particularly as regards the expansion of nuclear power, is reviewed. The policy in the U. K. concerning the disposal of radioactive waste is stated and the system of control used to achieve the objectives of this policy - that no person shall be exposed to more than the internationally accepted standards for safe exposure of members of the public - is described. Data on the behaviour of artificial radionuclides, on which systems of control are initially based, are reviewed, and information on the current radiological status of U. K. freshwater and estuarine disposal areas is presented.

The range of attraction of animal baits and carbon dioxide for mosquitoes. Studies in a freshwater area of West Africa

In an inland area of the Gambia the density of flying mosquitoes at successive distances from a pair of bait-calves or an equivalent source of carbon dioxide was measured with ramp-traps to determine the maximum range at which orientation towards the bait was initiated. Thirty-six traps were operated at intervals of 7·5 m up to a distance of 60 m from the bait, on 66 nights. Anopheles ziemanni Grünb., Mansonia uniformis (Theo.) and Aedes spp. were responding to the presence of the baitcalves from a distance of 22·5–30 m; with carbon dioxide as bait the same species showed a clear response at 15 m but, with the doubtful exception of M. uniformis, not at 22·5–30 m. M. africana (Theo.) responded to both calf and carbon dioxide baits at 15 m but not at more distant ranges. Culex thalassius Theo. and C. univittatus Theo. showed a response at 7·5 m but not at any greater distance. C. decens group showed no response to either bait even in the nearest traps (7·5 m). The parous rate in Mansonia spp. varied with distance from the bait. Similar variation in the proportion of females infested with mites was not detected.

Native fishes of the Central Plateau area-Tasmania

In comparison with the northern hemisphere, the major continents of the southern hemisphere have a relatively small freshwater fish fauna. This is probably due to the fact that the predominant portions of the main southern hemisphere land-masses lie in tropical, subtropical or temperate zones and except for the southern-most extremities are not overendowed with rivers and lakes. Consequently the potential for invasion of fish into freshwater areas where they can become established is limited. Most freshwater fishes living today are considered to be derived from marine ancestors which have subsequently invaded freshwater. Evidence for this can be found in the fact that many groups of fishes which are considered to be predominately freshwater species periodically descend to the sea or to the estuaries to spawn or carry out some other phase of the life cycle.