bluuebunny/crossref_metadata_2025 huggingface dataset:
Anguillicola in Dutch Eelfarms; Current State
Authors: Kamstra A.
Published: February 2007

Anguillicola crassus was introduced into Dutch eelfarms by infected stocking material originating from inland fisheries. Within farms, suitable intermediate hosts for transmission of the parasite are available and uninfected stock becomes rapidly infected. In farming situations, only very heavy infections with the parasite can cause significant damage to fish, mainly by secondary infections. Treatment of fish infected with A. crassus is possible with L‐Levamisole as a bath treatment or mixed with the feed, which results in complete immobilisation of the nematode. Transmission of the infection within farms can be controlled by keeping populations of copepods low. This can be accomplished by avoiding accumulations of organic matter within systems and/or control with chemical means. It can be stated that Anguillicola crassus does not pose the threat to intensive eel culture it once seemed to be.
Limnology of a Sewage Polluted Lake: The Lower Lake (Bhopal, India)
Authors: Valecha V. , Valecha R. , Bhatnagar G. P.
Published: February 2007

Seasonal and vertical distribution of temperature, pH, dissolved oxygen, free CO2, alkalinity, nitrate, phosphate and phytoplankton have been studied at the deepest point of the Lower Lake, Bhopal from September 1979 to August 1981. Stratification was noticed in almost all the parameters. Bottom was frequently anoxic. The dominant groups among phytoplankton were Chlorophyceae, Cyanophyceae and Bacillariophyceae.
The Combined Effects of Food and Temperature on the Life History Parameters of Brachionus patulusMULLER (Rotifera)
Authors: Sarma S. S. S. , Rao T. Ramakrishna
Published: February 2007

The combined effects of different levels of temperature (15°, 25° and 35°C) and food Chlorella (1,2 and 4 × 106 cells/ml) on the life history parameters (lifespan, life expectancy, net reproductive rate, intrinsic rate of increase, developmental time, and generation time) of a laboratory population of the rotifer Brachionus patulus were investigated. Both food and temperature, independently and in interaction, significantly influenced nearly all the parameters. The reproductive performance was a direct function of the food level, but the magnitude of food effect was temperature‐dependent. The observed temperature × food interaction effects are explained in terms of the energetics of resource apportionment between metabolism and reproduction.
The Microbial Food Web in Eutrophic Shallow Estuaries of the Baltic Sea
Authors: Schiewer Ulrich , Jost Günter
Published: February 2007

Microbial food webs are responsible for the main carbon flow in shallow eutrophic estuaries of the Baltic Sea. Bacteria account for respirative use most of the autotrophic production. Bottom‐up influences are mainly directed to the phytoplankton. Massive increase of phytoplankton biomass has only little effect on the biomasses of the heterotrophic plankton. The investigated ecosystem obviously differs by its high bacteria/non‐bacteria heterotrophs‐relation from other aquatic ecosystems.
Tendencies in the Herring Population Development of the Baltic Sea
Authors: Rechlin Otto K. W.
Published: February 2007

During the 1960's a change in population structure of Baltic herring started which resulted in the dominance of spring spawners in the entire Baltic since the beginning 1970's. Autumn spawning herring is very rare in the yields of fisheries since. This development has been accompanied by a likely increase of the total stock biomass of herring in the area. Yields of herring fisheries increased remarkable up to 1984, partly as a result of increased fishing effort. Recent developments of stock biomasses point to dependencies on fluctuations of growth rates. Growth is influenced by several environmental factors but is very likely especially dependent on abundance of food and on temperature. Eutrophication of the Baltic Sea increased perhaps the abundance of food for the planktonfeeding herring but it may have been contributing to the depletion of autumn spawning herring via the declining oxygen content of bottom water layers during the past 20 years.
Changes of Structure and Stock in Exploited Fish Communities in Estuaries of the Southern Baltic Coast (Mecklenburg‐Vorpommern, Germany)
Authors: Winkler Helmut M.
Published: February 2007

By means of analyses of catch values of selected fish species possible effects of eutrophication on the estuaries are described. Although the registered stock changes are not only a result of eutrophication a stock increase in pikeperch could be verified at the end of the first half of this century.

With progressive eutrophication a great decline of migratory fish stocks took place at the end of the sixties/beginning of the seventies.

The decline of eel stocks is not caused by eutrophication. Afterwards pike stocks show an aggravating decline in hypertrophic estuaries which are related to the decline of macrophytes. Baltic whitefish has still kept up its stock level under these conditions.

Symptoms for a growing danger of an unexpected disaster are increasing to the whole fish community of extremely polluted waters.
Long‐term Changes in Macrozoobenthos of the Gdańsk Deep
Authors: Zmudziński Ludwik , Osowiecki Andrzej
Published: February 2007

The paper presents an analysis of the bottom fauna occurrence in the central part of the Gdańsk Deep in the past four decades. In 53% of the samples there were not any bottom invertebrates at all and they periodically disappeared in every decade. At the beginning of the study period, Priapuloidea, Bivalvia, Crustacea and Polychaeta were present in the bottom fauna communities, while only the two latter groups occurred towards the end of the period and the hemipelagic polychaete Harmothoe sarsi was often noted as the only species of the macrozoobenthos.
Nitrogen Metabolism in Ecosystems—A New Approach
Authors: Ripl Wilhelm , Feibicke Michael
Published: February 2007

Using the new Energy‐Transport‐Reaction Model, the nitrogen‐cycle is presented in relation to energy flow in a system. This model is applied exemplary to three degraded inland water bodies. The decrease in the density of energy flow in a spatially limited system provides the framework for this model. By this model the N‐cycle can be observed in relation to other abiotic and metabolic processes. The N‐cycle proves to be an important indicator, sensitive to disturbances in the hydrologic cycle. A poorly managed hydrologic cycle will increase resource losses from the watershed, and stimulate the formation of loss processes. The model allows an evaluation of a catchment's management according to its ion losses related to its nitrogen losses. Based on a longterm sustainable function of a catchment the integrity of the system is measured by its degree of closure of material cycles and lack of losses. Moreover, loss‐minimizing management practices can be derived from the model. Planning and management can be directed towards this goal of minimizing losses and evaluated accordingly.
A Study on the Impact of Urban and Industrial Development in the Linggi River Basin, Malaysia. 1. Morphometry and Physical Environment
Authors: Khan I. S. A. Nather
Published: February 2007

The Linggi River Basin is one of the most polluted river basins in Malaysia and drains an area of about 1,399km2 in the state of Negri Sembilan. An extensive multidisciplinary research was carried out to develop a predictive mathematical model to manage the Linggi River basin effectively. This paper reports only the morphometry and other physical environmental conditions of the Linggi River Basin which was carried out between January, 1983 and January, 1984. Topography, vegetation, landuse pattern, general geology and lithology, population distribution and water usage by the people are discussed. In addition, physical information such as air and water temperatures, precipitation, sunshine, discharge, suspended solids and dissolved solids data collected before and after the study period are discussed in detail.
Diurnal Patterns of Mixing Depth and its Influence on Primary Production in a Shallow Lake
Authors: Nixdorf Brigitte , Pagenkopf Wolf‐Gunther , Behrendt Horst
Published: February 2007

The influence of turbulence induced mixing on phytoplankton metabolic processes was investigated by hydrophysical and biological measurements in the eutrophic shallow lake Großer Müggelsee (mean depth = 4.9 m). To trace spatial and temporal changes in the mixing depth, high resolution temperature profiles were recorded and analysed.

The vertical transport of algae in the mixed layer was simulated by the lift method, which allows an adjustment of the depth and the velocity of particle movement in a wide range (0.5‐10 cm, 0.03–3 cm · s−1). The results of this dynamic incubation were compared with those of the conventional static incubation.

In general, turbulence induced mixing enhances the areal daily primary production. Net oxygen production in cycled bottles is increased up to three times compared to the areal O2‐release of algae which were incubated at a fixed position. This was proved particularly during afternoon incubation indicating the increasing importance of mixing during the course of a day. Changes in the mixing depth have only weak influence on primary production. There is a tendency towards higher O2‐production as the mixing depth increases. Remarkable diurnal changes were observed in community respiration and compensation depth. Furthermore, the influence of photoinhibition, O2‐saturation of the lake water and the diurnal changes in Chl a‐concentration on primary production were measured and discussed.
Denitrification, Nitrificastion and Nitrogen Fixation in Sublittoral Sediments of the South China Sea
Authors: Odintsov Vyacheslav S. , Propp Michail V. , Dultseva Olga A.
Published: February 2007

Measurements of denitrification, nitrification and nitrogen fixation rates were made alongside with measuring of chemical and physical properties in sublittoral sediments of the South China Sea near the coast of Vietnam. Studied sediments were suboxic (Eh was positive as a rule), had 0.18–1.5 % of organic carbon, 0.004–0.135 % of total nitrogen and 3‐12 % of total iron. The numbers of denitrifying and nitrate‐reducing bacteria were as high as millions and hundreds of millions cells per gram wet weight of sediment matter, respectively. The processes of nitrification and denitrification were not spearated spacely. The nitrification was measured in both superficial layer and in a 10‐cm sediment column. There were indirect evidences suggesting possibility of anaerobic ammonium oxidation. Denitrification was detectable in the sediments from two sites of sampling; maximal value was 86.2 μmoles N m−2h−1. The denitrification potential determined at 1 mM nitrate decreased regularly from the upper to lower layers. Its values in the different sediments ranged from 134 to 532 μmoles N m−2h−1. Nitrogen fixation (from 4.8 to 86μmoles N m−2h−1) was close to that found in similar sediments in temperate waters in summer, and was not a significant source of nitrogen. It was comparable with diffusion of ammonium from sedimnts.
The Influence of Environmental Factors and Microhabitat Availability on the Distribution of an Aquatic Oligochaete Assemblage in a Mediterranean River Basin
Authors: Prenda José , Gallardo Alfonso
Published: February 2007

Some aquatic oligochaete species, mainly certain naidids and tubificids, are often associated with polluted environments, with high levels of organic matter and oxygen deficit. However, in the stations sampled in the Guadaira river basin, which can be arranged on an axis of organic pollution, the main aquatic oligochaete species (Nais elinguis and Tubifex tubifex) inhabiting these environments do not show a distribution pattern significantly related to the water physico‐chemical characteristics measured. Nor, have we registered any association between these species and any kind of microhabitat, defined here: water current, presence of different types of vegetation, substrate coarseness and presence of anoxic sediments. Paranais litoralis is the exception, being related to areas without water current, located at higher altitudes, with high levels of dissolved organic matter and an anoxic substrate made up of fine particles.

These results can be explained by the highly fluctuating nature of Mediterranean ecosystems and by the marked generalist character and ubiquity of the oligochaete assemblage species, able to colonize any kind of environment.
In situ Development of Perch Eggs, Perca fluviutilis L. (Pisces, Percidae) in a Small Eutrophic Lake, Lake Plussee, Holstein, Germany
Authors: Reyes Mario R. Delos , Arzbach Hans‐Hermann , Braum Erich
Published: February 2007

Naturally spawned egg strands of perch, Perca fluviatilis L. were sampled from exposed fir trees submerged in Lake Plußsee, Holstein, Northern Germany from April to May 1989. These were incubated in situ and in the laboratory to estimate the viability, development and abnormalities of the embryos. From the in siru incubated eggs 91.6% embryos were viable, the nonviable portion comprising 1.1 % unfertilized eggs, 5.1 % dead and 2.2 % with abnormalities. As compared to the eggs incubated in the laboratory with 84.1 % viable embryos, the nonviable portion consisting 1.1 % unfertilized eggs, 11.3 % dead and 3.5 % with abnormalities. Incubation rate of P. fluviatilis embryos both in situ and laboratory, ranged from 200‐210 ATUs (10°C in situ and 8°C in the laboratory) with incubation period of 20‐27 days from fertilization to 50 % hatching.
A Population of the Sea Anemone Anemonia viridis (FŐRSKAL, 1775) and its Associated Flora and Fauna, in the North Aegean Sea
Authors: Chintiroglou Charis , Koukouras Athanasios
Published: February 2007

The assemblage of Anemonia viridis which is an important component of the photophilic soft algae biocoenosis, has not been adequately studied up to date. The A. viridis assemblage studied, was poor in species number compared to other photophilic soft algae assemblages, possibly because of its peculiar physiology and competition for space. Three age groups of A. viridis were distinguished, two of which (the first and the third) showed significant seasonal variations. The reasons for this are still unclear and may depend on recruitment, competition among small‐sized individuals, predation or other mortality factors, and migration of larger individuals.
Investigations on the Ecology and Fish Fauna of the Mahakam River in East Kalimantan (Borneo), Indonesia
Authors: Christensen Mikkel S.
Published: February 2007

Water quality was determined on the Mahakam River floodplain from 1980 to 1987. Five water‐body types were distinguished, i.e. slow‐flowing and faster‐flowing rivers, lakes, small waterbodies and swamps. Water quality in large rivers was stable in the short but not the long term. In all other ecotypes variability was higher, with marked fluctuations being recorded in small waterbodies.

A total of 147 indigenous freshwater fish species have so far been identified from the Mahakam. The zoogeographical consequences are discussed.

Migratory patterns were inferred for four fish species, Helostoma temmincki, Leptobarbus hoe‐venii, Puntius schwanenfeldii and Thynnichthys vaillanti. Juvenile H. temmincki (< 3 cm SL) migrate at the surface in schools of 40‐80 individuals at speeds of 0.48‐1.08 km · h−1, travelling 3.8‐8.6 km · h−1. Fecundities for P. schwanenfeldii (7,900–16,000 eggs), T. vaillanti (2,900–24,000 eggs) and H. temmincki (6,200–9,100 eggs) were determined.
The Life Histories of Two Temporarily Coexisting, Pond Dwelling Cladocerans
Authors: Maier Gerhard
Published: February 2007

Investigations on the life histories of two cladocerans, Moina brachiata and Daphnia obtusa, in a small, nearly temporary pond in South Germany revealed that M. brachiata is better adapted to fluctuating environmental conditions; the species dominated from May to October. D. obtusa was present in spring and autumn/winter but disappeared completely during the summer months. Both species coexisted for extended periods in spring and autumn; abundance of D. obtusa was generally by an order of magnitute lower. Four periods of low water level were slightly preceded by or coincided with a decrease of clutch size, a decrease of the proportion of egg bearing females indicating that both species suffered from food shortage.

Laboratory investigations on life history parameters showed that the two species have different temperature tolerances and preferences. M. brachiata showed its highest reproductive success at 25 and 30°C but died at temperatures <15°C and ≥ 35°C. D. obtusa experienced a broader temperature range (2 to 25°C) but could not withstand temperatures ≥ 30°C. Short term starvation periods (3d) caused the death of M. brachiata females, while D. obtusa soon recovered and reproduced when being refed.

M. brachiata is a typical r‐species with early reproduction, rapid development, high population growth rates and a high tendency to produce resting eggs; D. obtusa pursues more the concept of k‐selection.
Study on the Decomposition of Pistia stratiotes L. (Araceae) in Cisne Reservoir, Uruguay
Authors: Sommaruga Ruben , Crosa Dario , Mazzeo Nestor
Published: February 2007

A study on the decomposition process of Pistia stratiotes L. was carried out in Cisne Reservoir, Uruguay. For this purpose, leaves and roots were considered separately, and the process was studied in the littoral and the pelagic zone. The litter bag technique was used to estimate dry weight losses at different times. Leaves decomposed faster than roots in both zones. Pistia decomposed faster in the pelagic zone due to better oxygen conditions and a more intensive water movement that removes material from within the bags. Phosphorus, potassium, sodium and magnesium were leached rapidly during the first week. Nitrogen content in the leaves initially increased, reaching its maximum in the littoral zone that coincided with that of bacterial numbers colonizing the litter. The number of macroinvertebrates, dominated by Chironomidae, was low. A rough estimation of the phosphorus impact on the littoral zone associated to the decomposition process shows that after 24 h between 13.9 and 16.8 μg‐at.1−1 have been released to the water.
Seasonal and Long‐term Variability of Nutrients in Lake Müggelsee
Authors: Kozerski Hans‐Peter , Gelbrecht Jörg , Stellmacher Rita
Published: February 2007

Seasonal and long‐term variability of the nutrients phosphorus, nitrogen, and silicon were investigated in the eutrophic Lake Müggelsee and its inflow from 1979 to 1990. The lake concentrations were internally controlled during the summer season and by the inflowing river in winter, respectively. The lake acts as a sink of nutrients. 18% of N and 3.5% of P were retained in the 12‐years‐period. Phosphorus retention differed from year to year. The average retention rate of the investigated period was only 4 kgP/d, but in some years it was negative due to strong P‐release from sediment. The P‐retention rate was also influenced by bank filtration (withdrawal for a waterworks).
Postimpoundment Changes in Water Quality and Fish Stocks in Two Large West African Reservoirs (Manantali and Sélingué, Mali)
Authors: Anne J. , Lelek A. , Tobias W.
Published: February 2007

The recently established large reservoirs Manantali on the river Bafing, tributary to the Senegal River and Sélingué, located on the river Sankarani, tributary to the Niger River, have followed similar changes in limnology and fish populations as those established in West Africa 20 to 30 years ago. Basic water parameters, such as oxygen content, pH, electrical conductivity and temperature show seasonal variations largely determined by the changes in wet and dry seasons. Both waterbodies are monomictic, with water mixing taking place in January, the coldest period of the year. Pre‐impoundment forest clearence of the future reservoir bottom in the shallow Sélingué reservoir was carried out only in the proximity of the dam site. In the deeper reservoir Manantali the savanna forest was cleared from an area of about 25 percent, and the tree gallery was cleared along the river. The initial filling of Manantali reservoir was followed by a nearly complete drainage of the reservoir. After refilling some months later, the dissolved oxygen content stayed reasonably high and therefore there was no fish mortality. Also no hydrogen sulphide or a large‐scale spread of noxious aquatic plants developed. At present the fish fauna is dominated by cichlids and pelagic species, i.e. at Sélingué by clupeids. and at Manantali by cyprinids (Leptocypris niloticus). In both reservoirs was the genus Citharinus considerably reduced. At Sélingué reservoir disappeared Protopterus annectens. The fish yield estimate is 27 kg/ha/year for Manantali, and 40 kg/ha/year for Sélingué. Both rerservoirs have recorded a slight increase in electrical conductivity. They both serve as a valuable water resource and fish supply for the Sahel region.
Fisheries in Semi‐Arid Northeast Brazil with Special Reference to the Role of Tilapias
Authors: Gurgel J. J. S. , Fernando C. H.
Published: February 2007

The reservoir fisheries in the semi‐arid Northeast Brazil have been studied based on the data collected by the Department of Action Against Droughts and placed against the background of what is known of similar fisheries in the tropics elsewhere. Of about 60,000 reservoirs in the region, DNOCS controls about 100 reservoirs since 1970. Physical characteristics are provided together with total areas of the reservoirs. Unfortunately very little basic limnological data are available.

In all 42 species of fish and crustaceans were introduced into these reservoirs of which only fourteen fish species and one shrimp were successful in establishing self‐propagating populations, others being stocked on a regular basis. The recent stocking ofColossoma macropomumandCyprinus carpioare however unsuccessful in reservoirs.

The fish yield of DNOCS controlled reservoirs for 1950–1990 was 112 kg.ha−1(Davies, 1972; Gurgel and Oliveira, 1987). It amounts now to about 20,000 tons annually taking into account incomplete and scaled down reporting of catches. This indicates a total fish catch from 60,000 reservoirs in the Northeast of Brazil of very substantial size.

The CPUE and catches of all species and that ofTilapia rendalliandOreochromis niloticusare given together with a discussion of the fisheries and recommendations for management. The total CPUE varied from 18–1,100 kg.ha−1. However, most fishermen are only part‐timers.

It appears likely that very substantial yields of fish are being harvested in Northeast Brazil but are under‐reported. Management strategies now in operation in reservoir fisheries are still very pragmatic. With the accumulation of data and generalizations, more viable strategies could be devised.
Low Fish Predation Pressure in the London Reservoirs: I. Species Composition, Density and Biomass
Authors: Kubečka Jan , Duncan Annie
Published: February 2007

The London reservoirs sited in the lower Thames valley form part of a continuously flowing, drinking water supply system and as such have been wholly designed, constructed and operated by man for this sole function. This paper adds some information on the potential impact of the fish populations on the ecology of these relatively deep reservoirs. The fish fauna was studied by night shore seining (to detect inshore fish communities) and acoustically (to detect the offshore fish communities). Ruffe (Gymnocephalus cernuus) and perch (Perca fluviatilis) are the main species capable of reproduction on the steeply sloping concrete walls of the reservoirs. Cyprinids are almost absent in Wraysbury Reservoir whilst in Queen Mary and Queen Elizabeth II reservoirs they are more abundantly represented due to enhanced spawning possibilities associated with inundated marginal terrestrial plants in Queen Mary and the net‐sides of empty fish cages in Queen Elizabeth II reservoir. Fish biomasses of the three London reservoirs studied are low: 6.8 kg/ha in Wraysbury Reservoir, 28.6 kg/ha in Queen Mary reservoir and 45.6 kg/ha in Queen Elizabeth II Reservoir. Coinciding with this is a zooplankton of unusually large‐sized cladocerans, largely daphnids, and high fish growth rates.
Lake Number, a Quantitative Indicator of Mixing Used to Estimate Changes in Dissolved Oxygen
Authors: Robertson Dale M. , Imberger Jörg
Published: February 2007

Lake Number, LN, values are shown to be quantitative indicators of deep mixing in lakes and reservoirs that can be used to estimate changes in deep water dissolved oxygen (DO) concentrations. LN is a dimensionless parameter defined as the ratio of the moments about the center of volume of the water body, of the stabilizing force of gravity associated with density stratification to the destabilizing forces supplied by wind, cooling, inflow, outflow, and other artificial mixing devices. To demonstrate the universality of this parameter, LN values are used to describe the extent of deep mixing and are compared with changes in DO concentrations in three reservoirs in Australia and four lakes in the U.S.A., which vary in productivity and mixing regimes. A simple model is developed which relates changes in LN values, i.e., the extent of mixing, to changes in near bottom DO concentrations. After calibrating the model for a specific system, it is possible to use real‐time LN values, calculated using water temperature profiles and surface wind velocities, to estimate changes in DO concentrations (assuming unchanged trophic conditions).
The Seasonal Occurrence of Glass Eels (Anguilla Anguilla L.) in the Rio Minho between 1991 and 1993 (North of Portugal)
Authors: Antunes Carlos
Published: February 2007

Glass eels were sampled monthly at two stations in the Rio Minho. The experimental fishery was carried out in the estuary between November 1991 and July 1992 and at an upstream site between December 1991 and March 1993. The yield differed at each station, especially in summer and between the official seasons of the experimental glass eel fishery. Early pigmentation stages were more frequent in the estuary and the maximum lengths and weights were observed in autumn and winter. The official statistics of the professional glass eel fishery are briefly mentioned.
The Distribution of Hydrobiids and the Effects of Sediment Characteristics on the Population Dynamics of Hydrobia ventrosa in a Coastal Region of the Southern Baltic
Authors: Bick Andreas , Zettler Michael L.
Published: February 2007

The composition of the hydrobiid fauna in a coastal water of the southern Baltic was studied in 1990/91 at three stations with different sediment characteristics (grain size, organic content). Four species were found (Hydrobia ventrosa, H. ulvae, H. neglecta and Potamopyrgus jenkinsi). H. ventrosa was dominant at all stations. The mean hydrobiid abundances were 4,000 (stn. C), 18,000 (stn. B) and 40,000 (stn. A) ind./m2 respectively. Abundance was found to correlate with the organic content of the sediment. The reproduction and growth of H. ventrosa was studied. Two reproduction phases were observed, one in summer and the other in late autumn. The autumn reproduction peaks were staggered owing to the different growth rates at the various stations. Possible correlations between the differences in shell size of H. ventrosa at the various stations and both sediment characteristics and abundance are discussed.
Lebensgemeinschaften koexistierender Arten der Wasserkäfergattung Hydroporus aus zwei norddeutschen Untersuchungsgebieten (Coleoptera; Dytiscidae)
Authors: Behr Hauke
Published: February 2007

The community structure of 15 species of the genus Hydroporus was investigated in various pools with the multivariate software DECORANA, TWINSPAN and CANOCO. Abiotic values measured at 22 bog pools were correlated to DECORANA‐data. Typical communities in the Ohemoor (near Hamburg) are related to the factors shaddow, absorption, calcium, and sodium. Data of coexisting Hydroporus species (including other small Dytiscidae, Haliplidae, Noteridae) from 93 pools (near Seedorf/Schleswig‐Holstein) could be devided into 4 typical communities (bog, wood, sand‐pit, agricultural areas).
Diurnal Variations in Swimming Activity of Rutilus rutilus (Cyprinidae) in a Group under Tank Conditions
Authors: Hammer Cornelius , Temming Axel , Schubert Hans‐Joachim
Published: February 2007

Measurements of the swimming activity of a group of roach (12–19 cm TL, average) in a circular swimming chamber revealed two distinct activity patterns: a diurnal and a nocturnal one. The experiments showed that, having the choice, two factors stimulated the rhythmicity of the swimming behaviour of the fish, i.e. light intensity and the presence of a current field in the proximity of the fish. During daytime (bright light conditions) the fish moved into the current field and swam on average at 0.4 BL/s (resting swimming). The roach remained swimming at this speed even if no current field was established, however, then distributed evenly in the basin. By contrast, during night (dim light conditions) the fish predominantly chose the still water section but swam on average with a cruising speed of 1.6 BL/s (night swimming). Accordingly, they did not seek the still water section for night swimming if the light was kept on. Then again, the fish distributed more or less evenly in the basin. The results support the hypothesis that the fish migrate during night‐time and do this preferably in still water.
The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet‐and‐Dry Climatic Zone: I. Physical and Chemical Causes and Biological Effects in the Pantanal of Mato Grosso, Brazil
Authors: Heckman Charles W.
Published: February 2007

The tropical wet‐and‐dry climatic zone is characterized by aquatic environments that cover extensive areas during part of the year and shrink to small standing water bodies or rivers with minimal water levels during the dry seasons. Even in the small permanent water bodies, the conditions fluctuate radically during each annual cycle. While there are often strong currents in the water courses during the high water periods, most aquatic habitats are strictly lentic during the dry seasons. Studies conducted in the Pantanal of Mato Grosso, one of the largest wetlands of the world, revealed major features of changes in physical and chemical parameters during the annual cycle. The general features of the climate include a hot, rainy period usually lasting from late October through late April, a cool, dry period from late April through late August, and a hot, dry period from late August through late October. Considerable year to year variations are encountered in the dates of onset and end of the various seasons, however. Four annual periods are recognized according to the water level in the Pantanal. Generally, the concentrations of dissolved inorganic substances are very low and stable during the high water period and variable and usually high in the remaining standing water bodies when much of the region has dried out. The amount of mineral nutrients increases as the water level rises during the early rainy season but decreases again as the aquatic macrophyte populations develop. Some of the reasons for the many short‐term changes in mineral nutrient concentrations and the roles of the various aquatic communities are discussed. The results presented will serve as a basis for subsequent studies on the seasonal succession of the flora and fauna.
Some Bag Experiments on Tibbs Run Lake, W.V., A Eutrophic Acidified Lake
Authors: Yates Carl , Decosta John
Published: February 2007

Tibbs Run Lake was sampled from December 1979 to December 1980, monthly during the winter and biweekly during the spring, summer, and autumn. Primary production was measured from March 1980 to February 1981, either monthly or biweekly, as indicated above. The mean annual hydrogen ion concentration was equivalent to pH 4.33. This pH was 46% lower (based on H+ concentrations) than the 1977–1978 mean. The low pH of the lake is due to inputs of acid precipitation and the low buffering capacity of the watershed. Predictions of further reductions in the lake pH, based on mean annual hydrogen ion concentrations and hydrogen ion retention coefficients (RH) from Shellito (1979) and this study, indicate that the lake pH should reach an equilibrium with the precipitation pH between 1982 and 1985, assuming the precipitation pH continues to average 4.10. The stratified period mean chlorophyll a and total phosphorus concentrations were 22.1 mg/m3 and 19.3 μg/1, respectively. Total phosphorus loading to the lake was 0.233 gP/m2/yr.

To examine the effects of neutralization and fertilization with phosphorus an in situ bag enclosure experiment, lasting 16 days, was performed during the summer of 1980. In the bags, phosphorus (20 μg/1 on days 0,4,8,12 as KH2PO4) was added alone and in combination with a base addition (IN KOH). The base additions raised the pH to approximately 7.8. Other treatments included base addition alone and a control. The maximum chlorophyll a concentration was found in the phosphorus treatment (∼30 mg/m3) on day 6. The phosphorus plus base treatment exhibited a 10 day lag before reaching a maximum chlorophyll a concentration (∼27 mg/m3) on day 16. The highest production rate was found in the phosphorus plus base treatment on day 12 (∼27 mgC/m3/hr.).

A similar bag experiment, lasting 46 days, was performed during the late summer and early autumn of 1980. The treatments were the same as in the first experiment, however, the nitrate‐nitrogen depletion in the lake and treatments necessitated the addition of nitrogen (2 mg/1 as NaNO3) to one of each replicate treatment on day 5. On day 34, the maximum chlorophyll a concentrations were found in the phosphorus plus base nitrogen treatment (∼120 mg/m3) and the phosphorus plus nitrogen treatment (∼38.8 mg/m3). The control plus nitrogen treatment was submerged and possibly contaminated on day 5. All treatments not receiving nitrogen, except for the phosphorus plus base treatment, decreased in the chlorophyll a concentration throughout the experiment. The phosphorus plus base treatment peaked in the chlorophyll a concentration on day 45 (∼28 mg/m3) despite non‐detectable levels of nitrate‐nitrogen. The maximum primary production rate was found in the phosphorus plus base plus nitrogen treatment (∼32 mgC/m3/hr.) on day 11.
Ecology and Gametogenic Biology of the Genus Umbellula (Pennatulacea) in the North Atlantic Ocean
Authors: Tyler P. A. , Bronsdon S. K. , Young C. M. , Rice A. L.
Published: February 2007

Four putative species of the seapen genus Umbellula, U. lindahli, U. thomsonii, U. durissima and U. monocephalus, are found at bathyal and abyssal depths in the Porcupine Seabight and Abyssal Plain in the NE Atlantic Ocean and at bathyal depths off the Bahamas. The most common species, U. lindahli, has a cosmopolitan distribution in the world ocean. In situ observations, from bathyal depths in the Bahamas, of the posture of U. lindahli show that the polyps are spread out to maximize particle capture from the water column. In addition, the individuals of U. lindahli from the Bahamas suggest that the tentacles are cropped by a predator, but there is no evidence of predation in the NE Atlantic specimens. Reproduction in U. lindahli is typical of that previously observed in pennatulids. Fecundity is high, although most of the oocytes present are previtellogenic with only a few developing through to maximum size at any one time. Some specimens of U. lindahli appear to be infested with a small flatworm.
Abyssal Megafaunal Necrophages: Latitudinal Differences in the Eastern North Atlantic Ocean
Authors: Thurston Michael H. , Bett Brian J. , Rice Anthony L.
Published: February 2007

A pop‐up time‐lapse camera system (BATHYSNACK) was used to study megafaunal organisms attracted to bait at three abyssal localities in the eastern North Atlantic Ocean, a northern site on the Porcupine Abyssal Plain and two sub‐tropical sites on the Madeira Abyssal Plain. Fish and decapod crustaceans appeared on 47% of photographs taken during deployments of up to seven days duration. The fishes Coryphaenoides (Nematonurus) armatus and Pachycara bulbiceps and the decapod Munidopsis spp. dominated appearances at the northern locality whereas over 95% of records at the two subtropical localities were of the decapod Plesiopenaeus armatus.

Cyclical variations in necrophage abundance did not correlate with tidal cycles of near‐bottom currents, although high P. armatus numbers were inversely related to current speed. Most of the frequently recorded entities showed contagious intraspecific distributions. In contrast, many of the interspecies relationships were non‐random, with co‐occurrences lower than expected, probably as a result of physical disturbance or potential predation. Population densities based on times of first arrival were calculated.

Assemblages dominated by fish at higher latitudes and crustaceans at lower latitudes are discussed in terms of organic carbon supply to the deep sea and pelagic community structures.
On the Vertical Distribution of the Metazoan Meiofauna in Shelf Break and Upper Slope Habitats of the NE Atlantic
Authors: Vanreusel Ann , Vincx Magda , Schram Danielle , van Gansbeke Dirk
Published: February 2007

The metazoan meiofauna of nine stations in shelf break and upper slope areas (70 to 1500 m water depth) of the N.E. Atlantic were investigated in order to assess which environmental factors are important in the control of densities and sediment profiles. Total meiofaunal densities (ranging between 368 and 1523 ind/10 cm2) were correlated with bacterial densities, an important food source for meiofauna. However, considering sediment vertical distribution profiles, the relative importance of both food and oxygen on the meiofauna became obvious. A combination of both bacterial densities and oxygen supply could explain about 95% of the variability in the vertical profiles of the meiofauna densities. Meiofauna numbers increase in proportion to food availability in the surface sediment layers, but this relationship breaks down in deeper sediment layers where the oxygen supply is often limiting, particularly in fine sediments.
Micro‐ and Nanoforaminifera from Abyssal Northeast Atlantic Sediments: A Preliminary Report
Authors: Gooday Andrew J. , Carstens Marina , Thiel Hjalmar
Published: February 2007

Rose Bengal stained benthic foraminifera which pass through a 63 μm mesh (microforaminifera and nanoforaminifera) have been extracted by handsorting the fine sieve residues (> 45 μm, 31 μm, 28 μm, 20 μm, 15 μm) of abyssal sediment samples. The samples were collected using a multiple corer in four areas of the northeast Atlantic between 31° N and 59° N. The abundance of these minute foraminifera varied from 2 specimens per 1 cm2 (Madeira Abyssal Plain) to > 110 per 1 cm2 (BIOTRANS area). They include a variety of taxa, the most common being certain rotaliid species, hormosinaceans and other multilocular agglutinated forms, the unilocular agglutinated genus Lagenammina, soft‐bodied agglutinated sphaeres and flasks (saccamminids and psammosphaerids) and allogromiids. Some specimens are < 63 μm in maximum dimension but others belonging to elongate taxa are longer.

Two samples taken 10 cm apart on the Porcupine Abyssal Plain suggest that minute foraminifera may be patchily distributed on a small scale. One sample, which was overlain by substantial amounts of phytodetritus, contained > 100 stained specimens (> 30 per 1 cm2) while the other, in which much less phytodetritus was present, yielded only 10 specimens (2.9 per 1 cm2). This observation suggests that some micro‐ and nanoforaminifera may flourish in the presence of decaying organic matter, perhaps consuming the associated bacteria. The presence of phytodetritus may also explain why two of our samples from the Madeira Abyssal Plain (MAP) contained an order of magnitude more stained tiny foraminifera than two other MAP samples in which phytodetritus was absent.
The Effect of Reservoirs on Phosphorus Concentration
Authors: Straškraba Milan , Dostálková Iva , Hejzlar Josef , Vyhnálek Vojtêch
Published: February 2007

The annual average degree of phosphorus retention (both TP and OP) in reservoirs was found to depend mainly on the theoretical retention time (RT). The phosphorus retention (RP) is shown for some reservoirs in Czech Republic to be well approximated (standard deviation = 10.9) with RP(TP) = 74.7* (1‐exp(‐0.0255* RT)) (N = 38, 7 ≤ RT ≤ 604 days).

The inclusion of 13 additional reservoirs for which data were assembled from literature resulted in an almost identical relationship: RP(TP) = 76.1* (1‐exp(‐0.0282* RT)) (N = 51, range of RT nearly unchanged).

The retention of soluble reactive phosphorus RP(OP) studied on data from literature seems to be higher than that of TP.

Statistical comparison with data for RP(TP) of lakes has shown a significantly lower retention in lakes than in reservoirs for comparable RP, resulting in RP(TP) = 66.0* (1‐exp(‐0.00419* RT)) (N = 59, 5.8 ≤ RT ≤ 260000 days).

The differences between RP(OP) and RP(TP) and differentiation of lakes and reservoirs are discussed and a need for more thorough theoretical analysis stressed. Consequences for watershed management are summarized.
Die Steuerung der externen Belastung der Sächsischen Talsperren als wesentliche Strategie ihrer Wassergütebewirtschaftung The Control of the External Loading of Saxonian Reservoirs — an Important Strategy of the Water Quality Management
Authors: Pütz Klaus
Published: February 2007

The Reservoir‐administration of Saxony continuously investigates the development of water quality in its numerous reservoirs. 25 of these reservoirs are used for drinking water supply. About 40 reservoirs have considerable importance for recreation and fishing.

The following priorities of water quality management are based on the results of scientific investigations:

protection against eutrophication

prevention of increase of nitrate concentrations

protection against polutants, especially pesticides, heavy metals, hydrocarbons, mineral oils

acidification of waters

The objectives of the water quality of the Saxonian reservoirs refer to EU‐guidelines, to DVGW‐guidelines, to the drinking water ordinance of FRG, to guidelines of LAWA and to the actual knowledge of limnology.

The evaluation of the most important reservoirs in the period from 1991 to 1994 shows the following result:

These objects can be achieved by two main strategies:

the reduction of the external loading

the control by means of the internal ecological mechanisms

To investigate the loadings of the reservoirs and the sources of the nutrients mass balances particularly for phosphorus and nitrogen were based on periodic analyses. From these mass balances the strategies of water qualilty management were derived. An important consequence in this conection is the following:

“The protection of the water is a basic requirement to the security of water quality”

Therefore, the reduction of external loading is the main field of the strategy. In the case of high nutrient loaded reservoirs, par example eutrophic waters, a combination with the strategy of internal control, particularly with the biomanipulation is carried on.
Nutrient Elimination in an Underwater Pre‐Dam
Authors: Paul Lothar
Published: February 2007

The nutrient elimination was investigated in the underwater pre‐dam Haselbach (UWHA) situated in the mouth region of the Saidenbach reservoir (Saxony, Germany). The pronounced thermal stratification with the depth of the thermocline determined by the top height of the underwater dam (4,8 m below surface) resulted in epilimnetic inflow and hydraulic short circuit between inlet and main basin of the reservoir in summer. A simple model was developed for the approximation of nutrient elimination. Epilimnetic nitrate was used as a quasi‐conservative discharge tracer. Compared with a “normal” pre‐dam of the same size, the estimated mean phosphorus elimination of less than about 20% in UWHA was low. However, the UWHA proved to be an efficient settling basin for allochthonous particulate P.
Phenology and Abundance of Ephemeroptera, Plecoptera and Trichoptera Caught by Emergence Traps at the Weidlingbach near Vienna, Austria
Authors: Waringer J. A.
Published: February 2007

A total of 1136 Ephemeroptera, Plecoptera and Trichoptera were caught from March 1993 to March 1994 at the Weidlingbach, a first to fourth order forest brook near Vienna. Austria, using pyramid‐type emergence traps at tree sampling stations (390, 360 and 260 m above sea level). Five species comprised 67.1 % of the catch: the ephemeropterans Paraleptophlebia submarginata (Stephens), Habroleptoides confusa Sartori and Jacob and Habrophlebia lauta Eaton, and the plecopterans Nemoura flexuosa Aubert and Leuctra hippopus Kempny. Most taxa emerged from April to August, but the plecopterans Leuctra prima Kempny and Capnia bifrons (Newman) were caught early in the year (January to April), and Leuctra digitata Kempny (Plecoptera), Chaetopteryx fusca Brauer and Chaetopteryx major McLachlan (Trichoptera) emerged in September and October. In Ephemeroptera and Trichoptera, similarities between species groups were highest at the two upstream sampling stations; in Plecoptera and in pooled taxa, however, similarities were highest at the middle and downstream sites. Except in Trichoptera, diversity was highest at the middle station situated at 360 m above sea level.
Changes in the Trophic Structure of Benthic Macroinvertebrate Communities Associated with Food Availability and Stream Flow Variations
Authors: Basaguren A. , Elosegul A. , Pozo J.
Published: February 2007

Macroinvertebrate communities were studied in relation to food (particulate organic matter and periphyton) availability and hydrologic regime in two reaches (autotrophic and heterotrophic) of the Agüera stream (Northern Spain). The structure of macroinvertebrate community reflected the trophic characteristics (main food sources) at each site. From a temporal point of view, both food availability and hydrologic regime seem to be the main factors that determine the dynamics and structure of the community. In the autotrophic reach, shredder density showed significant relationship with CPOM, and scrapers with periphyton both in terms of density and biomass.
The Seasonal Succession of Biotic Communities in Wetlands of the Tropical Wet‐and‐Dry Climatic Zone: IV. The Free‐Living Sarcodines and Ciliates of the Pantanal of Mato Grosso, Brazil
Authors: Hardoim Edna Lopes , Heckman Charles W.
Published: February 2007

This fourth paper in a series on the effects of the wet‐and‐dry climate on the northern Pantanal, Mato Grosso, Brazil, provides an outline of the seasonal activity of sarcodine and ciliate species. Both of these groups of protozoans include grazers on bacteria and algae, predators, and omnivores. Apparently because of their more complex trophic relationships and competition from small metazoans, the fauna of these groups in the Pantanal is considerably less rich in species than the alga flora, and the populations of most species remain small throughout the year. The presence of only 97 species was recorded during a period of study lasting about three and a half years. While the number of testacean species encountered is not notably less than expected, the number and diversity of the ciliate fauna are remarkably low compared to those encountered not only in the eutrophic waters of the temperate zones but also in water bodies in the eastern part of Brazil. The species found are almost exclusively cosmopolitan or circumtropical in distribution.