bluuebunny/crossref_metadata_2025 huggingface dataset:
ATP as an Index of Phytoplankton Productivity. The Chl a/ATP Quotient
Authors: Nωges Tiina
Published: February 2007

The seasonal changes in the adenosine triphosphate (ATP) and chlorophyll a (Chi a) concentrations in two eutrophic lakes (Lake Peipus, Lake Vōrtsjärv; Estonia) were studied in the course of two years. Comparative measurements were performed in the Baltic Sea. The main task was to examine how the ATP content of the water characterizes the functional state of the phytoplankton community. Primary production, total phosphorus and total nitrogen were measured as supplementary parameters. The under‐ice bloom in Lake Vōrtsjärv was also observed. The under‐ice bloom, consisting mainly of the diatom Melosira islandica spp. helvetica, started at the bottom of the water body and spread over the whole water column in a few days. The ATP content correlated well with changes in the chl a concentration of the bottom water, but in the uppermost regions of the water column no correlation was found. Obviously most of the cells had died before reaching the surface layers. Seasonal observations showed an accumulation of “dead” chlorophyll in autumn. The Chi a/ATP ratio increased in the following order: sea—eutrophic lake—hypereutrophic lake. The values of the index increased exponentially as the phytoplankton standing stock increased.
Perch, Perca fluviatilis L., in Small Lakes: Relations between Population Characteristics and Lake Acidity
Authors: Rask Martti
Published: February 2007

Perch population characteristics of small lakes were examined with a special reference to lakes which have acidified recently due to atmospheric deposition of air pollutants.

The population density and biomass of perch were higher in an acid (pH 4.5) clear water lake with low aluminium concentration than in recently acidified (pH 4.3–4.7) clear water lakes with higher aluminium levels. The structure of perch population in an acid (pH 4.4) humic lake was similar to recently acidified clear water lakes.

The population density and the biomass of perch were significantly higher in 6 lakes with pH>5.0 than in 6 lakes of pH<5.0 whereas the mean age and length at a given age were higher in the more acid lakes.
Amphipoda (Crustacea) in the Littoral Zone of Lake Balaton (Hungary). Qualitative and Quantitative Studies
Authors: Muskó Ilona B.
Published: February 2007

Species composition, size distribution, egg number and biomass of different amphipod species on littoral submerged aquatic vegetation (Myriophyllum, spicatum and Potamogeton perfoliatus stands) and on the stony shores of Lake Balaton at Tihany were estimated in August 1983 and 1985. Three species occurred in the material: Corophium curvispinum, Dikerogammarus haemobaphes and Dikerogammarus villosus. The bulk was formed by C. curvispinum. The mean number of eggs per female of the three investigated species showed differences at the different sampling stations and ranged between the following values: C. curvispinum from 3.3 to 8.8, D. haemobaphes from 16.4 to 22.8 and D. villosus from 8.0 to 17.5. The total biomass of amphipods was 1.8 and 3.5 mg dry weight/g fresh weight of macrophytes in 1983 and 1985 respectively, and 4.7 mg animal per dm2 stone surface in the stony littoral zone in 1983.
Daphnia and Toxic Blooms of Microcystis aeruginosa in Bautzen Reservoir (GDR)
Authors: Benndorf Jürgen , Henning Manfred
Published: February 2007

As a part of a whole‐lake, long‐term experiment in biomanipulation in. the hypertrophic Bautzen reservoir (G.D.R.), during three years (1984–1986) the dynamics of mouse‐related LD 50 of Microcystis aeruginosa was compared with the biomass development of this blue‐green and the grazing pressure exerted by Daphnia galeata. Since the three summer averages of the biomass of D. galeata revealed strong differences due to decreasing predation activity of fish from 1984 to 1986, the effects of different grazing pressure on Microcystis toxicity could be investigated under field conditions. Microcystis was nontoxic at the beginning of the growing season and developed high toxicity during its first strong biomass increase in summer in all three years. But this decrease of the LD 50 together with the first biomass increase of the season is found in quite different periods in different years (1984: August, 1985: July, 1986: June). It is obvious that the higher the mean effective filtration rate of D. galeata during summer is found the faster the toxicity of Microcystis is formed. If these observations are combined with findings of other authors, the conclusion can be drawn that the development of toxic Microcystis blooms seems to be promoted by a combination of five conditions:

(1) Presence of a mixture of toxic and nontoxic Microcystis strains at the beginning of the growing season even if the portion of toxic strains is very low, (2) physical and chemical growth conditions which favour Microcystis over other phytoplankton, (3) high grazing pressure by zooplankton on edible food particles over a rather long period, (4) patchy distribution of the different Microcystis strains if nonselective filtrators such as Daphnia dominate the zooplankton, and (5) absence of defense mechanisms of Microcystis against grazing which are not coupled with toxicity (e.g. large colony size). These conclusions contribute to a better understanding of the possibilities and limits of in‐lake eutrophication control by biomanipulation and emphasize the need to combine top‐down and bottom‐up control mechanisms in eutrophic and hypertrophic waters.
The Effect of pH on Copper Toxicity to Blue‐Green Algae
Authors: Lüderitz V. , Nicklisch A.
Published: February 2007

The effect of pH on copper toxicity to two planktonic blue‐green algae, Aphanizomenon gracile and Oscillatoria redekei, was investigated. Growth rates of the algae without copper treatment decrease with pH, Aphanizomenon is earlier and more affected than Oscillatoria. On the other hand, pH‐lowering leads sooner to a toxicity enhancement in Oscillatoria. In the acid range, toxicity retardation occurs in Aphanizomenon. At pH 5.1, shortening of the interval between copper toxicity and copper stimulus is characteristic for both species.
Some Observations on the Irradiance and Carbon Fixation in Grane Langsø
Authors: Nygaard G.
Published: February 2007

Photosynthetically active radiation (PAR) was registered daily in 0.25 m and 11.25 m in 3 years. Upwards irradiance of green light was 1 % of downward irradiance. Incubator 14C experiments showed that the phytoplankton enhanced its carbon uptake substantially with increasing concentrations of the carrier CO2 in the ampoules. Severe carbon limitation of photosynthesis occurred in spring and summer 1961, where the real carbon fixation was only about 34 % of that calculated by the usual procedure. Utilization of light and DIC by the phytoplankton and its compensation depth was determined. Photoinhibition occurred down to 10–11 m, and net primary production was nearly always positive in any depth down to the lake bottom.
Field and Laboratory Studies on Nile Phytoplankton in Egypt III. Some Physical and Chemical Characteristics of Aswan High Dam Lake (Lake Nasser)
Authors: Ahmed Ahmed M. , Mohammed Ahmed A. , Springuel  , El‐Otify Ahmed M.
Published: February 2007

Seasonal, local and monthly vertical variations in physical and chemical characteristics of Aswan High Dam Lake (AHDL) were followed during the period from March 1982 to February 1984. The results show that there were distinct seasonal thermal variations. Similarly, thermal stratification was evident from late spring through early autumn. Oxygen content appeared to vary with the changes in pH value. Water transparency in the southern part was greatly reduced by the incoming silt laden flood especially in summer months. Consequently, nitrate‐nitrogen and total residue increased considerably in this part during summer. The recorded minimum N‐concentration (2.35μg l−1) was certainly limiting the growth of phytoplankton. Suspended and organic matter exhibited somewhat irregular variations at least during the period of this study.
Field and Laboratory Studies on Some Photosynthetic Bacteria in Aswan High Dam Lake I. Some Physical and Chemical Characteristics
Authors: Shoreit A. A. M. , Ahmed A. M. , Shabeb M. S. A.
Published: February 2007

Seasonal variations in some physical and chemical characteristics of samples collected from summer 1984 to spring 1985 and vertically from the surface to the bottom at two sites along the main body of Aswan High Dam Lake and in two side Khors were studied. Water temperature showed seasonal as well as vertical variations. The pH values were in the vicinity of 8.0. Dissolved oxygen concentrations were higher at the surface than at the bottom. The total dissolved solids showed seasonal as well as irregular vertical variations. Bicarbonates, nitrates, and silicates showed a marked increase with depth, while sodium, potassium, calcium and magnesium showed generally a slight or, sometimes, marked increase with depth. Phosphates and sulfates showed a slight or marked decrease with depth. Chlorophyll a decreased with depth while bacteriochlorophyll a increased.
A Mathematical Model for 137Cs Uptake and Release by Filamentous Algae
Authors: Švadlenková Marie , Dvořák Zdenêk , Slávik Ondrej
Published: February 2007

A mathematical model of the dynamics of radiocaesium transport in the aquatic phase—algae system is suggested in this work. Allowance is made for algae growth and for both reversible and irreversible absorption of this radionuclide by the algae. The algae biomass is divided hypothetically into two compartments with different exchange kinetics. The parameters of the model are time dependent. The model is quantified using experimental data for the concentrations of 137Cs in Cladophora glomerata filamentous algae and in water, obtained in situ in the environment of a nuclear power station. The model fits the data reasonably well and can be applied, for example, in bioindication of radioactivity in aquatic recipients in the environment of nuclear power stations.
Reproduction and Larval Ecology of the Blue Swimming Crab Portunus pelagicus in Ragay Gulf, Philippines
Authors: Ingles Jose A. , Bkaum Erich
Published: February 2007

The Ragay Gulf situated at the southeastern part of Luzon is an important fishing area especially for the blue crabs. Commercial landings are caught by traps, gillnets and trawls. Most prevalent catching method is by means of baited traps called “Bubo” in Pilipino. Landings fluctuate yearly and were 641 t in 1984 and 210 t in 1985. The hydrographic situation especially the current system changes seasonally with existing monsoon periods. Females of the blue swimming crab in the Gulf reach maturity at a mean carapace width of 10.5 cm. In tank experiments they spawned 13 days after copulation. Though berried females were found throughout the whole year, two main spawning periods exist namely, one from February to April and another from July to October. Larvae hatched 5 to 6 days after oviposition at 29.5 °C and 4 zoea stages were observed. The horizontal and vertical distribution as well as the possible transport mechanism of zoeae are discussed in relation to the existing current systems and the orientation behaviour of the larvae. Because of the very few megalopa samples caught in this study, its distribution pattern has only preliminary character.
Collembola in the Bed Sediments of an Alpine Gravel Stream (RITRODAT‐Lunz Study Area, Austria)
Authors: Bketschko G. , Christian E.
Published: February 2007

In the creek “Oberer Seebach”, 355 springtails belonging to 42 species were collected from the water‐filled pore space of the bed gravel proper and the adjacent bank sediment. Almost 10 % of 2094 samples contained Collembola, with a mean density of 1.8 specimens per positive sample. The topographic distribution of the most abundant species Lepidocyrtus lignorum, Agrenia bidenticulata, and Folsomia quadrioculata suggests that riparian and eurytopic forms are frequently washed into the channel and transported down to a considerable sediment depth without injury to the animals. The rising groundwater table in the bank sediment traps no riparian, but predominantly hemiedaphic species. Euedaphic springtails are rare, especially in the groundwater samples.
Fish Community Structure on a Deep Ocean Outfall, Barber's Point, Oahu, Hawaii
Authors: Russo Anthony R.
Published: February 2007

The Barber's Point, Oahu, Hawaii sewer outfall structure attracts large numbers of fish (500 — 1000 per 336 m2 bottom area) and fish species (23—29) not normally seen over flat, soft bottoms characteristic of the diffuser (66 m) isobath. Except for fish species strictly associated with corals, the adult fish community parameters (species richness, abundance, and composition) were similar to shallower natural Hawaiian reef environments. The adult fish species composition at the diffuser changed significantly during the discharge of heavy flocculated pre‐treated sewage (15 mgd). High rates (15 mgd) of pre‐treated sewage may cause decreases in total fish abundance and species richness when compared with the discharge of primary effluent with little or no flocculation between 0 and 19 mgd. Two fish species, which were generally abundant in Hawaiian waters during the years of observation, were absent at the outfall during discharge of heavy flocculated pre‐treated effluent.
Ecology of Some Ricefields in Japan as Exemplified by Some Benthic Fauna, with Notes on Management
Authors: Kurihara Yasushi
Published: February 2007

The role of tubificids and mud snails in the ricefield ecosystem was elucidated using their ecology as a basis for highlighting problems in the strategy of recycling between agricultural and urban activities.

Tubificid oligochaetes occur in high densities in ricefields where irrigation water is polluted with sewage, high organic matter content is present in the soil and when highly toxic insecticides are not used. High tubificid densities reduce and even eliminate weeds, change the composition and density of bacteria and increase the density of zooplankton. Also they serve as a high quality source of food for fish comparable to that of insects. Conditions that promote a healthy growth of tubificids obviate or reduce the need for weedicides and high levels of inorganic fertilizers.

Mud snails which thrive in ricefields have been used as an important source of protein food for humans in rural Japan. The snails can consume a sludge‐reed compost mixture used as a fertilizer in ricefields. However the high heavy metal content in the sludge is accumulated by the snails which are thus unfit for human consumption. Based on these results and the known ecology of tubificids and the snails, a possible recycling system comprising sewage sludge, reeds, fish, insects and egrets using these two kinds of benthic organisms is proposed.
Live Algae in Deep Sediment Layers
Authors: Wasmund Norbert
Published: February 2007

Examination of sediment cores taken from shallow coastal regions of the Baltic showed that some algae were still alive at depths beyond the depth of light penetration. Their cells contained chlorophyll and photosynthesis resumed when they were exposed to light. Photosynthesis was detected by simultaneous measurement of oxygen production and 14C uptake. Autoradiography was used to detect incorporated 14C. The autoradiographic method was improved by a few modifications.
Response of Phytoplankton to Copper Treatment with Reference to Species Sensitivity
Authors: Lüderitz Volker , Nicklisch Andreas
Published: February 2007

Responses of different planktonic algae species to copper treatment were tested using semi‐continuous culture and compared with studies on copper‐induced changes in species composition of phytoplankton samples. Blue‐green algae exhibit lowerEC100‐values than diatoms andScenedesmus.

The four tested strains ofMicrocystis aeruginosashowed different copper sensitivity.

Four response types can be distinguished.

1. rapid biomass loss after copper application but subsequent growth recovery.

2. fluctuations of growth but no loss of biomass at sublethal concentrations

3. continuous recovery of growth rates after initially affected growth.

4. growth inhibition (dormancy) and recovery after inoculation into a copper‐free medium.

Species response to copper application within a phytoplankton sample agrees with pure culture behaviour.
Sediment Chemistry of Lake Bhim Tal, U. P., India
Authors: Gupta P. K. , Pant M. C.
Published: February 2007

Certain chemical constituents (NO3‐N, bio‐available P, Ca, Na, K, Mn, Cu, Co and organic matter) together with pH, Eh and clay content of surface sediments at various depths of the overlying water in Lake Bhim Tal were examined during 1977—1978. In addition, NH3‐N and dissolved oxygen at the mud‐water interface (water immediately above the sediments) were measured.

The values of Eh, pH and NO3‐N in the sediments showed a negative relationship with water depth and positive relationship with dissolved oxygen at the interface. The other variables of the sediment were positively related to water depth and negatively related to dissolved oxygen at the interface. Organic matter, K, Na and Ca showed positive relationship with the amount of clay while the cations (K, Na, Ca) and trace metals (Cu, Mn, Co) showed a positive relationship with the amount of organic matter in the sediments.
Toxicity of Piperonyl Butoxide — Carbaryl Synergism on the Snail Lymnaea acuminata
Authors: Singh D. K. , Agarwal R. A.
Published: February 2007

Effects of piperonyl butoxide and carbaryl synergism were studied on the metabolism of the snail Lymnaea acuminata. Snails were exposed to 40 % and 80 % of the 48 h LC50 of carbaryl or carbaryl + piperonyl butoxide mixture (1:5). The amount of carbaryl present in the LC50 mixture was only 0.23 % of the LC50 of carbaryl alone. The treatments caused a dose‐dependent decrease in glycogen and protein levels and acetylcholinesterase (AChE) and alkaline phosphatase activity; simultaneously, there was an increase in levels of lactic acid, reducing sugars and amino acid and the activity of acid phosphatase. Significant differences in AChE and phosphatase activity were also observed between the effects of equivalent concentrations of carbaryl and carbaryl‐synergist.
Succession of Chironomus Meigen Species (Diptera, Chironomidae) in Newly Filled Ponds
Authors: Matêna Josef
Published: February 2007

The colonization by Chironomus spp. of two ponds filled after a dry period was investigated. Field data were collected by means of quantitative benthic samples and emergence traps. C. melanescens. C. annularius, C. riparius, C. piger, C. luridus, C. obtusidens, C. plumosus, C. dorsalis and Camptochironomus tentans were determined cytotaxonomically in ponds investigated. C. melanescens and C. annularius appear to be the most characteristic species colonizing in high numbers in newly filled ponds. Larvae of C. annularius grew more slowly in ponds compared with the former one which resulted in a characteristic succession of both larval types. Most species mentioned disappeared completely from the ponds investigated after the metamorphosis of a single cohort. They were replaced by C. plumosus which was often attended by C. annularius in smaller ponds.
The Entomostracan and Rotifer Communities Associated with Submerged Plants in the Norfolk Broadland — Effects of Plant Biomass and Species Composition
Authors: Irvine Kenneth , Balls Hilary , Moss Brian
Published: February 2007

The microcrustacean and rotifer communities associated with submerged aquatic plants were studied over a three‐year period in a series of experimental ponds, created within a fenland drainage ditch. Seasonal abundance and spatial distributions were assessed. The ponds contained a varying amount of vegetation, dominated either by Ceratophyllum demersum or Stratiotes aloides and this had consequences for the ponds' animal communities. Increasing densities of Ceratophyllum were associated with increases in weed‐associated entomostracans whereas increases in Stratiotes led to a general decrease in associated animals. Increases in both plant species led to reductions in abundance of Daphnia, but to differing amounts. A relatively low density plant population in the presence of zooplanktovorous fish did not provide a refuge from predation for large‐bodied Cladocera.
Long‐term Dynamics of Benthic Invertebrate Standing crop Palos Verdes Shelf, Southern California
Authors: Maurer Don , Haydock Irwin
Published: February 2007

Wet weight standing crop of macrobenthic invertebrates from the Palos Verdes Shelf, California showed several major fluctuations from 1972 to 1986, mainly due to the bivalve Parvilucina tenuisculpta and the echiuroid Listriolobus pelodes. From 1972 to 1986 mean biomass was 285 g/m2. When this value was compared with standing crop from other shelves, Palos Verdesstanding crop fell within the range documented for the tropics to higher latitudes. There was a small decline with increased effects of El Nino in 1983. When Palos Verdes standing crop was compared to the biomass portion of the Pearson‐Rosenberg SAB curve, it was concluded that their model is probably not applicable on this portion of the shelf. Finally, the long‐term data base provided the opportunity to propose several hypotheses. These concerned the potential effect of L. pelodes on species diversity and hydrogen sulfide in the sediment and the influence of L. pelodes on excess standing crop.
Die Feinstruktur der Kolbenzellen (Schreckstoffzellen) in der Epidermis von Astyanax mexicanus Filippi 1853 (Characinidae, Pisces) und seinen Höhlenderivaten “Anoptichthys”
Authors: Peters Nicolaus , Schmidt Wiebke , Fricke Diethard
Published: February 2007

Fine Structure of the Club Cells (Alarm Substance Cells) in the Epidermis of Astyanax mexicanus Filippi 1853 (Characinidae, Pisces) and its Cave Forms “Anoptichthys”

The club cells in the epidermis of Astyanax mexicanus are of the same ultrastructure as those in other Ostariophysan fish. There are also no essential differences to be found between the club cells of epigean Astyanax mexicanus and its cave forms “Anoptichthys”. Our findings correspond to former statements in that the function of the club cells producing and releasing alarm substances has been maintained in the cave forms.
Phosphorus Losses from the Epilimnion in Římov Reservoir
Authors: Porcalová Petra
Published: February 2007

The amount of settling phosphorus was measured in Římov Reservoir using sediment trap technique from April 1986 to April 1987. Sediment traps were placed at three depths near the dam of the reservoir and at the bottom along the reservoir.

The highest amount of phosphorus in trapped material was found during the fall turnover in the epilimnion and near the bottom in both spring periods (1986,1997). During the growing season the changes in dry weight and total phosphorus in settling seston were related to changes of phytoplankton biomass in the trophogenic layer. The amount of trapped phosphorus was higher near the bottom than in the upper layers of the reservoir throughout the year.
Assessment of Water Pollution using Diatom Community Structure and Species Distribution — A Case Study in a Tropical River Basin
Authors: Khan I. S. A. Nather
Published: February 2007

A study on biological assessment of water pollution using diatom community structure and species distribution was carried out in the Linggi River Basin, Malaysia which was polluted by various urban, industrial and agricultural wastes. A total of 86 diatom taxa belonging to 21 genera were recorded from all eight sampling stations located in the basin, of which 70 species were found on artificial substrates; the remaining 16 species were recorded exclusively on natural substrates. The number of diatom species observed between the stations varied from 22‐47 species. The dominant diatom species in decreasing order of abundance were Eunotia vanheurckii, Nitzschia palea, Achnanthes saxonica, Gomphonema parvulum and Achnanthes minutissima. The most common clean water species were Achnanthes minutissima, A. linearis and Synedra rumpens. The most tolerant species were Nitzschia palea followed by Gomphonema parvulum and Pinnularia braunii. Eunotia vanheurckii and Navicula cryptocephala occurred in high densities at both unpolluted and polluted stations and can be considered as the common facultative or indifferent species. Although a large number of species were recorded at the unpolluted stations, equivalent number of species were also found at the moderately polluted stations. However, the number of species was reduced at grossly polluted stations. Nevertheless, a marked variation in species association exists between the unpolluted and polluted stations, but not among the polluted stations to distinguish the type and degree of pollution.
The Mechanism Controlling Plant Nutrient Concentrations in the Northern Adriatic Sea
Authors: Gilmartin Malvern , Degobbis Danilo , Revelante Noelia , Smodlaka Nenad
Published: February 2007

A 20 year data set for the northern Adriatic was analyzed and the factors establishing the nutrient environment identified. Concentrations ranged widely (TIN 0.0–78, PO2 0.01–1.1, and SiO4 0.0–59 mmol m−3). In early winter remineralization increased concentrations. Characteristic winter, late spring and fall phytoplankton blooms alternately decreased and increased concentrations, as modified by river input. In summer nutrients were minimal under a semi‐closed circulation pattern and high vertical stability, due to closely coupled nitrogen and phosphorus assimilation‐regeneration processes and biogenic silica sedimentation. “New” primary production supported mainly by river input of “new” nutrients approximated “regenerated” primary production supported by regenerated nutrients, making the ecosystem especially sensitive to eutrophication pressure from anthropogenic increases in the Po River nutrient load.
Factors Responsible for Retarding the Eutrophication Rate of Some Mesotrophic Lowland Lakes in N.E. Poland
Authors: Hillbricht‐Ilkowska Anna
Published: February 2007

The chemical composition of watershed waters supplying 13 mesotrophic lakes (in N.E. Poland) including as the deepest lake L. Hańcza, z = 108.5 m (summer total phosphorus [TP] content ≤0.050 mg · 1−1, chlorophyll a ≤5μg · 1−1, SD≥2.5 m) in a typical postglacial lake district (Suwalski Landscape Park) as well as surface and bottom waters of the lakes were studied in summer. Although the underestimated (i.e. including only surface runoff, river inflows and precipitation) yearly TP loading is equal to or higher than the permissible value, the lakes have maintained their mesotrophic features for 20 to 30 years. P sorption to the allochthonous inorganic material as well as decalcification processes in the lakes are probably responsible for this situation, as there is a strong difference between the chemical content of supplying waters and lake waters and as there is a considerable enrichment of P on sestonic particles. As a consequence of the low bio‐availability of P, the midsummer amount of chlorophyll a is lower than predicted from the “TP—chlorophyll‐a” relation found for harmoniously eutrophicating (i.e. P‐limited) lakes.
Zooplankton Dynamics of Lake Escondido (Rio Negro, Argentina), with Special Reference to a Population of Boeckella gracilipes (Copepoda, Calanoida)
Authors: Balseiro Esteban G. , Modenutti Beatriz E.
Published: February 2007

The zooplancton dynamics and the populations of Boeckella gracilipes Daday of Lake Escondido (Rio Negro, Argentina) were studied from March 1987 to March 1988. Rotifers and Cladocerans showed high densities during spring and summer, while copepods were densest in autumn. The vertical distribution study showed that rotifers prefer upper levels of the water column, while cladocerans and copepods prefer lower levels, especially during thermal stratification.

Boeckella gracilipes had a sex ratio biassed toward female, though changes in the sex ratio were observed. The clutch size was high in winter when the proportion of ovigerous females was low. The instantaneous birth rates were low during winter and high in summer. This result is related to the thermal cycle of the lake, by the influence of temperature on egg development time. The mortality rates showed a similar pattern, and maximum values were registered in spring and summer.
Diel emergence patterns of chironomids
Authors: Learner Michael , Pickering James , Wiles Roy
Published: February 2007

The diel emergence patterns of 16 chironomid species from a Berkshire lake are characterized. A study of these patterns and those described previously in the literature indicate that the diel pattern for any chironomid species can often be predicted on the basis of the Tribe to which it belongs. Chironomini spp. usually emerge at dusk or at night. Macropelopiini spp. and Metrioenemini spp. characteristically emerge during daylight but the former peak in the morning and the latter peak in the afternoon. Orthocladiini and Tanytarsini spp. exhibit more varied patterns although bimodalism is a frequent feature. The phylogenetic conservatism in the diel patterns displayed implies that these patterns became established early during chironomid evolution, and are, therefore, plesiomorphic.
Note on the survival of algal resting cells during long‐term maintenance in darkness and minimum lake bottom temperature. Comparison of Anabaena (cyanobacteria) and Haematococcus (volvocales)
Authors: Braune Wolfram
Published: February 2007

Resting cell formation in algae and cyanobacteria is one of the strategies developed for withstanding adverse environmental conditions. This note informs about the different capacities of such resting cells to germinate after long‐term dark preservation at 4 °C in Anabaena variabilis (Cyanobacteria, Cyanophyta) and Haematococcus lacustris (Chlorophyta, Volvocales).
European Catches of Elver of 1928‐1988
Authors: Moriarty Christopher
Published: February 2007

Data on quantities of glasseels and elvers caught at 11 stations on the western and northern coast of Europe together with abundance indices for glass eels at Den Oever, Netherlands and for larvae in the Bay of Biscay are presented covering the period 1924 to 1988. Large catches were made in the 1960's and 1970's followed by a sudden and widespread, but not universal, decline in the 1980's. Catches within years between stations showed significant correlations in some cases but not in all.
Distribution and Abundance of Glass‐Eels Anguilla spp. in East Australian Waters
Authors: Beumer John , Sloane Robert
Published: February 2007

The invasion of glass‐eels Anguilla species into coastal waters of Eastern Australia is described from the results of sampling as well as a review of pertinent literature. A. reinhardtii has a year‐round invasion in tropical and sub‐tropical waters while A. australis has a similar invasion pattern in temperate waters. The former species is most abundant in latitudes 20‐34° S with the latter species most abundant in latitudes 35‐44° S. A. australis glass‐eels were longer and heavier than those of A. reinhardtii. The recorded distribution and abundance patterns are discussed in terms of rainfall regimes and the movements of inshore currents.
Shape Analysis of Otoliths—a Tool for Indirect Ageing of Eel, Anguilla anguilla (L.)?
Authors: Doering Peer , Ludwig Jürgen
Published: February 2007

Eel otolith shapes can be separated into distinct groups which can be assigned to certain age groups. The shape is described exactly through Fourier series using the maximum‐projection‐area. Clusters formed by the magnitudes of Fourier descriptors agreed with age groups of three year intervals by 66% (kappa = · 522, p<.001). Artificial shapes for the resulting clusters were constructed from the mean Fourier descriptors. Further studies with eels of known age are needed to validate shape analysis of otoliths as an objective measure for indirect ageing.
Age Determination of Eels in the French Mediterranean Lagoons Using Classical Methods and an Image Analysis System
Authors: Panfili J. , Ximenes M.‐C. , Do Chi T.
Published: February 2007

Several methods are used for age determination of eels in the French mediterranean lagoons (observation of the whole otolith after clearing, grinding and polishing, dyeing, SEM and image analysis). Two types of otoliths are observed depending on the width of the growth rings which is probably related to the environmental conditions. Furthermore, the growth checks are located nearby or inside the opaque rings. A computer assisted method is developed, with reference to the other methods, with the aim of improving the efficiency of collecting and processing age and growth data. With further developments and increasing knowledge of the life‐history of elvers and juvenile eels, it seems possible to use an image analysis system for ageing eels in lagoons. Nevertheless, the most important point is to validate the results before using them for growth populations studies.
Gonad Sex Differentiation of Anguilla anguilla by Sex Steroids
Authors: Colombo Giuseppe , Grandi Gilberto
Published: February 2007

Anguilla anguilla elvers, reared in warm fresh water, were treated with 17 a‐methyltestosterone (MT) and with 17 α‐ethynilestradiol (EE), administered with a commercial diet. A very low proportion of untreated elvers developed as females. A very high proportion of the EE treated elvers developed as females and the gonads differentiated as ovaries at an earlier growth stage. Among the MT treated elvers, in a very low proportion of eels the gonads developed as ovaries, most into a undifferentiated testis‐like gonad and some with abnormal histological features.
Eel Biomass in a Small Lowland Stream
Authors: Moriarty Christopher , Nixon Eugene
Published: February 2007

A total of 399 eels were recovered from a rotenone operation in part of a tributary stream of the River Nore. Figures for biomass of 52 kg per ha or 42 kg per km were calculated. Small eels were scarce and the youngest aged was 6 years. The oldest was 28 years and measured 57 cm. The majority of eels in the stream measured between 30 cm and 50 cm and were aged between 10 and 20 years.
Caractéristiques d'une pêcherie d'anguille (Anguilla anguilla) au verveux dans un petit estuaire (Blavet, France). Characteristics of an Eel (Anguilla anguilla) Fyke‐net Fishery within a Small Estuary (River Blavet, France)
Authors: Fontenelle G. , Gascuel D. , Mounaix B.
Published: February 2007

From 1983 to 1986, an eel fyke‐net fishery was studied within the estuary of Blavet River (Brittany) which was not fished yet. The monthly mean CPUE issued from logbook data can reach 4.8 kg/gear · 24 hours. They largely depend on the locations (the higher the more downstream they are) and on the season as well. The results suggest a rather narrow home range within all the year long. By analyzing the CPUE‐Effort relationship, no overfishing can be noticed, up to now.
Short Note on the Silver Eel Catch on the Lower River Shannon
Authors: Moriarty Christopher
Published: February 2007

Catches of eel from the Shannon lake system of 35,000 ha have fluctuated from 10 to 46 t per annum over the period 1964 to 1988. Peak catches are observed at intervals from 3 to 5 years. Catches increased following improvement of fishing gear but otherwise remained steady in spite of a sustained increase in stocks. Migration was observed every month except June. The numbers of female eels>60cm decreased over the period. Male eels ranged from 39 to 44 cm, ages 5 to 15; females from 45 to 99 cm, ages 8 to 30 years.
A Survey of Heavy Metal Levels in Eels (Anguilla anguilla) from some Rivers in East Anglia, England: the Use of Eels as Pollution Indicators
Authors: Barak N. A.‐E. , Mason C. F.
Published: February 2007

A survey was made of mercury, cadmium and lead in the liver and flesh of 517 eels from eleven rivers in East Anglia. Eels from some sites showed high metal levels, indicating sources of metal contamination. Eel liver is a suitable indicator of inorganic pollution and the flesh is a suitable indicator of organic pollution.
La pêcherie de civelle (Anguilla anguilla) en Loire (France) en 1987: Evaluation des prises accessoires et impact halieutique. The Glass Eel (Anguilla anguilla) Fishery in the Loire Estuary (France) 1987: Estimate of By Catch and its Effects on Resources
Authors: Guerault D. , Desaunay Y.
Published: February 2007

By‐catch is estimated by sampling the whole fishery (February to April 1987) on the basis of a survey of the fishing effort: 16 species of commercial interest are considered, among them 3 species are dominant: Flounder, sprat and brown shrimp (98,4% of the 49,3 million individuals). By‐catch consists mainly of very young animals (larval or 0‐group stages). An attempt is made to consider the ratio between by‐catch and the potential natural mortality of juveniles.
Studies of Gonadal Steroids Involved in Final Gonadial Maturation in the Japanese Eel, Anguilla japonica, a Review
Authors: Yamauchi Kohei
Published: February 2007

Vitellogenesis in females and spermatogenesis in males were stimulated by exogeneous gonadotropic preparations. However, the subsequent oocyte maturation and spermiation did not advance because of the insuffiency of circulating 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (17α, 20β‐diOHprog). At the time of maturation, the injection of 17α, 20β‐diOHprog induced oocyte maturation and ovulation in females and spermiation (increase in volume of seminal plasma and acquisition of sperm motility) in male. These results suggest strongly that 17α, 20β‐diOHprog play a key role in the final maturation of the Japanese eel.
The Use of Mycelia of Penicilium sp. as an Ingredient for Glass Eel Nutrition
Authors: Gonçalvks J. F. , Gomes E. , Amaral L. , Coimbra J.
Published: February 2007

Three isoproteic and isoenergetic diets containing fish meal as a protein source (control diet) or incorporating 10 and 20% of protein from mycelia Penicilium sp. as a fish meal substitute were tested during three months for eel fingerlings growth.

Some preliminary “in vitro” experiments on the L‐Lysin intestinal absorption in the presence and in the absence of Penicilin (500 mg/l) after 17 h of contact show a positive effect of this antibiotic. No residues of Penicilin were detected in carcass of eels fed 7 days with 100 mg/kg Penicilin in the food.

The present results show that the use of Penicilin mycelia in eels diets will have the advantage of increasing growth without any appreciable change in the quality of the carcass and also, eventually, reductions of nitrogen excretion with a positive effect in effluent quality.
Are the same Compounds in Microcystis responsible for Toxicity to Daphnia and Inhibition of its Filtering Rate?
Authors: Jungmann Dirk , Henning Manfred , Jüttner Friedrich
Published: February 2007

Three strains of Microcystis when supplied to Daphnia in mixtures with Scenedesmus differed in their power to inhibit filtering rates. The axenic strain PCC 7806 had the strongest effect (93% inhibition with 50% Microcystis in the food). This strain was toxic to daphnids since Daphnia died faster under these conditions than without any food. Strain PCC 7806 also exhibited strong toxicity against mice (LD50 22 mg/kg). When the toxicity against Daphnia and mice was tested with cells of Microcystis PCC 7806 which has been subjected to various extraction procedures, the extraction of freeze‐thawed cells with water slightly reduced the mouse toxicity, eliminated Daphnia toxicity and reduced the inhibition of the filtering rate. After treatment with a lipophilic solvent, the cells of PCC 7806 still showed low mouse toxicity, but no longer inhibition of the filtering rate and no toxicity to Daphnia. Thus, our data suggest that Daphnia toxicity and inhibition of the filtering rate are caused by different compounds, but we cannot rule out the possibility that the factors toxic to mice and inhibitory to the filtering rate are identical.
On the Occurrence of Aphanizomenon flos‐aquae var. Flos‐aquae in Fish Ponds
Authors: Pechar Libor , Fott Jan
Published: February 2007

Summer blooms of Aphanizomenon flos‐aquae var. flos‐aquae accompanied by dense populations of Daphnia were common in fish ponds of the district Blatná in 1950s‐1960s. Changes in management (increased stocking densities, decreased usage of superphosphate as fertilizer) made this type of plankton less frequent. The present study documents this trend and suggests explanations.
Seasonality in Nutrients and Phytoplankton Production in Two Shallow Lakes: Waigani Lake, Papua New Guinea, and Barton Broad, Norfolk, England
Authors: Osborne P. L.
Published: February 2007

Waigani Lake, near Port Moresby, Papua New Guinea and Barton Broad, Norfolk, England are both shallow lakes nutrient‐enriched from sewage effluent disposal. In Waigani Lake phytoplankton biomass varied seasonally with lower levels (100‐200 mg chlorophyll α m−3) during the wet season increasing to over 400 mg chlorophyll α m−3 at the end of the dry season. Secchi disc depths varied between 0. 11 and 0. 34 m. Phytoplankton productivity in Waigani Lake was very high throughout the year (range: Amax 4,370‐21,000 mg O2 m−3 h−1) but production was lower during the wet season (range: Amax 4,370‐12,700 mg O2 m−3 h−1). High surface productivity was recorded from August to December except on sampling days when the weather was overcast. Productivity throughout the year declined rapidly with depth. Algal biomass in Barton Broad varied from 3‐10 mg chlorophyll α m−3 in winter but increased in spring and was very high in summer (200‐500 mg chlorophyll α m−3). Secchi disc depth varied from 0.21 m in August 1976 to 1.76 m in December. Phytoplankton production in Barton Broad was low in winter (range: Amax 247‐1,250 mg O2 m−3 h−1) but increased markedly in spring and summer with the highest rate (Amax 6,850 mg O2 m−3 h−1) being recorded in August. Surface inhibition was observed during summer except when the weather was overcast. Seasonality in nutrients and phytoplankton in Waigani Lake appear to be related to rainfall. Nutrient concentrations in Barton Broad are more closely related to phytoplankton activity which, in turn, correlates with seasonality in solar radiation.
Structural and Functional Characteristics of Aquatic Animal Communities
Authors: Alimov A. F.
Published: February 2007

Structural and functional characteristics of macrobenthic animal communities have been studied in several rivers and lakes. Shannon diversity index (H) has been used as a measure of animal community structure. Relation of community production (Pb) to metabolic rate of all animals in the community (Rb) was regarded as its functional characteristic. Quantitative relations between structural and functional characteristics of aquatic animal communities have been established. The work deals with steadiness and stability and complexity of aquatic animal communities with regard to their structural and functional characteristics. For a better understanding of possible changes in communities brought about by human impact a notion of community durability is introduced, which means their ability to resist environmental changes maintaining their structure and functions.
Optical Limnology of a Hypertrophic Gravel‐Pit Lake
Authors: Cobelas Miguel Alvarez
Published: February 2007

The underwater light field has been studied in a hypertrophic, gravel‐pit lake close to Madrid (Spain) during a one year cycle. Both the inherent and the apparent properties of the underwater light field have been weekly surveyed. As theoretically expected, there is a link between inherent and apparent properties in this lake. Evidence is given suggesting that a seasonal trend in the underwater light field seems to occur. The main factor attenuating light in the vertical column is phytoplankton chlorophyll “a” but humic substances also appear to play an importtant role in light attenuation.
Phytoplancton du lac Ichkeul (Tunisie): Composition, structure et activité photosynthétique Phytoplankton of Lake Ichkeul (Tunesia): Composition, Structure and Photosynthetic Activity
Authors: Rejeb‐Jenhani Amel Ben , Kartas Fredj , Lemoalle Jacques , Amblard Christian
Published: February 2007

Phytoplankton evolution was established during a study carried out on lake Ichkeul (Tunisia) from January 1985 to June 1988. During this period, the flora, composed of 51 species is distributed principally between Diatomophyceae and Chlorophyceae. Succesional changes of phytoplankton were often unpredictable and characterized by populations with monospecific trend. Photosynthetic activity and the parameters Aopt and IK were studied regularly along the year 1985 by oxygen method (GOLTERMANN, 1969). The relations between phytoplankton composition and photosynthetic activity were discussed.
Current Trends in Hydrographic and Chemical Parameters and Eutrophication in the Baltic Sea
Authors: Nehring Dietwart , Matthäus Wolfgang
Published: February 2007

Analysis of phosphate and nitrate data recorded in the winter surface layer of the Baltic Sea from 1958 to 1989 indicate positive overall trends, although the rate of accumulation has decreased since 1978. The long term accumulation of these algal nutrients in the oxic deep water below the halocline has also decreased since 1977. Under anoxic conditions, however, the trend shown by the phosphate concentration is distinctly positive in recent times owing to phosphate remobilization from the sediment.

The salinity has decreased in the surface water and even more rapidly below the halocline in the central Baltic basins during the period marked by the absence of major salt water inflows since 1977. The oxygen conditions have also deteriorated in the near‐bottom water layer during this time as shown by the considerable rise in the hydrogen sulphide concentrations. These changes, including the recent phosphate accumulation under anoxic conditions, can thus be considered natural rather than anthropogenic.

The impact of long‐term variations in nutrients and hydrographic parameters is discussed with respect to the development of Baltic fish stocks.
The Ecological State of the Waddensea. An Assessment
Authors: Höpner Thomas
Published: February 2007

Since the present quality state of the Wadden Sea is judged more discordantly than that of the North Sea, it is examined whether the Wadden Sea is a separate ecosystem. The nutrient load into the Wadden Sea and the trend of the load are assessed. Biological indicators of the ecological state of the Wadden Sea are examined with the result that there are signs of a bad as well as of a good state. This contradiction is assigned to the fact that quality standards are absent. Self‐protection mechanisms of the Wadden Sea are discussed with respect to their responsibility for the relatively good state. A qualitative model is proposed to explain the long‐term behaviour of the ecosystem.
The Microbial Food Web and its Sensitivity to Eutrophication and Contaminant Enrichment: A Cross‐system Overview
Authors: Weisse Thomas
Published: February 2007

The relative contribution to the pelagic carbon flux of bacteria, autotrophic picoplankton (APP), and heterotrophic nano‐ and microplankton is highest in pristine oligotrophic waters. Increased nutrient loading stimulates picoplankton production but reduces the importance of the microbial food web. Not all microorganisms are affected in the same way by eutrophication and contaminant enrichment. In contrast to bacteria and heterotrophic nanoflagellates, the APP was found to be highly sensitive to heavy metal contamination. The changing significance of the microbial loop has far‐reaching consequences for the entire ecosystem including alterations occurring in the benthos. The structure and functioning of the microbial food web is similar in marine, brackish, and freshwater ecosystems.