bluuebunny/crossref_metadata_2025 huggingface dataset:
The Upper Limit of Phytoplankton Production as a Function of Nutrient Load, Temperature, Retention Time of the Water, and Euphotic Zone Depth
Authors: Uhlmann Dietrich
Published: February 2007

In laboratory models of sewage ponds operated on a semicontinuous‐flow basis, the net primary production II of the phytoplankton was measured by harvesting the suspended matter both from the outflow and the bottom of the vessels at daily intervals. The maximum value of II was as high as 50 mg dry weight/l day (corresponding to 20 mg C/l day). With the nutrient load L kept ad a constant level, the steady state phytoplankton biomass x decreased with decreasing water residence time t in accordance with the dropping inflow concentration of the nutrients. On the other hand, at 20 °C no higher x was yielded at t=40 than at t=5 days. This result obviously has to be attributed to a substantial increase in grazing rate with progressing t at the temperature level of 20 and 30 °C. In this connection extremely low magnitudes of II may result despite optimum levels of nutrient supply, radiation and temperature.

The highest estimates of II hitherto measured and recorded in the literature relate to the euphotic zone depth (zeu in m) as follows:
equation image
The Diatoms, Productivity and Morphometry of 43 Lakes in New York State, U.S.A
Authors: Shero Brian R. , Parker Michael , Stewart Kenton M.
Published: February 2007

Diatoms were examined in surface sediments collected from 43 lakes throughout New York State to determine the interrelationships among the abundances of various diatom taxa,' lake productivity and lake morphometry. Diatom ratios, including the A/C, C/P and five new quotients, were not well correlated with lake productivity, probably because of the diversity of the taxa which they employ. The abundance of individual genera or combinations of genera were better indicators of productivity. Cyclotella was the best single indicator of productivity being most abundant in low productivity lakes. Several fairly distinct diatom associations were identified by correlations between all possible pairs of diatom taxa. Finally, lake productivity was found to be significantly correlated with morphometry, being highest in small/shallow lakes.
The Crustacean Zooplankton of Grasmere Before and After a Change in Sewage Effluent Treatment
Authors: Smyly W. J. P.
Published: February 2007

The limnetic crustaceans of Grasmere, a small lake in the English Lake District, were studied from February 1969 to December 1970 (23 months) and from January to December 1975. These observations were made before and after a change in sewage effluent treatment effected in May 1971. Planktonic species, except for one cladoceran, were more abundant in the second than the first period, while hypolimnetic and profundal forms either became less abundant or modified their life‐style in conjunction with a developing hypolimnetic oxygen‐deficit.
Influence of the Season and of Preservation Methods on Wet‐ and Dry Weights of Larvae of Chironomus plumosus L
Authors: Landahl C. C. , Nagell B.
Published: February 2007

Preservation in 70% ethanol or 4% formaldehyde solution resulted in the leaching of ca. 30% arid ca. 10% dry matter, respectively. Subsequent soaking in water considerably increased leaching. The percent ratio of dry weight to live weight decreased during the summer from ca. 15% in June to ca. 11 % in September for the fourth instar larvae. The results indicate that formaldehyde can chemically react with the larvae, thereby increasing their dry weight. The dry weight of the gut content was ca. 4% of the total dry weight.
On the Food of the Air‐breathing Catfish, Clarias batrachus (LINN.) Occurring in Wild Waters
Authors: Thakur Nirmal K.
Published: February 2007

The paper describes the food of Clarias batrachus (LINN.) occuring in derelict and swampy waters of the Bihar region of the Indian subcontinent. The study revealed that the early post‐larval stage is exclusively planktophagous while in the late post‐larval stage it starts including larger organisms in its diet. Juvenile stage is predominantly insectivorous. Though adults have a wide range of food preference, the insect material forms by far the most important source of their food. The fish did not appear to possess enough sense to sort out edible from non‐edible forms. March and September are the peak periods of relatively intensive feeding. The intensity of feeding in relation to the size of the fish showed that the average weight of food/g weight of the fish decreases with increasing weight of the fish.
The Characteristics of a Temperate Eutrophic, Dimictic Lake (Lake Mikołajskie, Northern Poland)
Authors: Kajak Zdzisław
Published: February 2007

Gross primary production equals 3160 kcal Xm−2 ×yr−1, 38% coming from the littoral. The efficiencies of both nonpredatory and predatory zooplankton production are high. The production of phytoplankton is expended mostly for sedimentation in April, for grazing by zooplankton in June, heterotrophic respiration and cumulation of dissolved and particulate organic matter in August—September and sedimentation in late autumn. Almost total elimination of zooplankton is done by predators, mostly invertebrates. About 10% of autochthonically produced plus allochthonic matter is annually removed from cycling, mostly as permanent bottom deposits. The annual load of phosphorus is 3 times higher than the permissible VOLLENWEIDER'S level. About 70% of phosphorus load, but only two percent of its reserve in the lake is annually removed from cycling. Progressing eutrophication resulted in several times increased phytoplankton biomass, decrease of phytoplankton P/B and share of nannoplankton, increase of decomposition in epilimnion, etc, during 10 years. Inspite of this, pelagic community in spring still has rather mesotrophic than highly eutrophic character. Increased eutrophication due to human impact (deforestation, agriculture, erosion) is also seen in bottom deposits since the 15th century.
Trophic Changes in Reservoirs; An Hypothesis Using Phosphorus Budget Models
Authors: Ostrofsky Milton L.
Published: February 2007

Current empirical models used to predict phosphorus concentration from loading, retention and discharge data assume a phosphorus load which is constant in time. Such models are clearly inappropriate in relation to reservoirs. In a study of several lakes and a reservoir in western Labrador, the phosphorus budget model was found to be an excellent predictor of phosphorus concentration in the natural lakes, but seriously underestimated phosphorus concentration in the reservoir.

Since leaching of nutrients from inundated soils and vegetation is generally considered to be the cause of trophic changes in reservoirs, a time dependent “leach loading” component was built into the steady state phosphorus budget model. This component not only allowed the budget to be balanced, but allowed the estimation of leaching coefficients describing the rate of phosphorus loss from submerged soils and vegetation. Using literature data from other reservoirs, the modified model predicted phosphorus dynamics consistent with other observed trophic status indicators.
Distribution and Fractionation of Arsenic in Selected Fresh Water Lake Sediments
Authors: Huang Pan M. , Liaw Wen K.
Published: February 2007

The distribution and nature of the As‐bearing components of the sediments of selected fresh water lakes in Saskatchewan, Canada, were studied. The total As contents ranged from 2.7 to 13.2 ppm As and were found to be present in both colloidal and non‐colloidal fractions of the lake sediments. The proportion of the As bound to carbonates, organic matter and sesquioxides accounted for 12 to 74% of the total As of the sediments. The remaining As was apparently associated with apatite and silicates. The data indicate that the bulk of As in the lake sediments resides in sesquioxidic components and apatite. The release of As from the lake sediments would thus be affected by the stability of these As‐bearing components in a series of particle size fractions. Furthermore, based on information on the geographical distribution of As in the lake sediments, land erosion and agricultural runoff appear to be contributing significantly to the As concentration in lake sediments. It is thus suggested that close attention should be paid to land management and soil conservation to prevent further enrichment of As in lake sediments and to curtail the subsequent As contamination of the food chain.
Plankton Biogeography of the Indian Ocean
Authors: Krishnamurthy K. , Naidu W. Damodara , Santhanam R.
Published: February 2007

Knowledge of plankton biogeography for the Indian and adjacent seas is necessary for an understanding of the regional characteristics and changes in the plankton composition. Some of the plankters will serve as good biogeographical indicator species. Some phytoplankters and tintinnids among zooplankton are promising for use as such labels for the presence of different waters in the Porto Novo (Coromandel coast, Bay of Bengal) region. A biogeographical classification of the local phytoplankton and peculiarities in the distribution of some rare tintinnids occurring there are discussed.
Some Factors Influencing the Diversity and Species Composition of Benthic Invertebrate Communities in Twenty Arctic and Subarctic Lakes
Authors: Moore James W.
Published: February 2007

The factors influencing the density, diversity and species composition of benthic invertebrate communities in 20 lakes in the Canadian arctic and subarctic were determined during 1975, 1976 and 1977. Despite small differences in nutrient and phytoplankton levels among the lakes, there was a strong positive correlation between these parameters and the density and diversity of the communities. Other factors, including maximum summer water temperature, lake depth and surface area had little overall effect on the communities. The densities of 2 ultra‐oligotrophic chironomids (Heterotrissocladius oliveriandMicropsectracf.groenlandica) increased markedly in cold deep lakes. However the abundance of the majority of species, most notablyProcladius denticulatus, Tanytarsussp., andStictochironomussp., was not effected by temperature. Other species, (Pontoporeia affinis, Monodiamesa bathyphilaandDicrotendipes nervosus) were probably restricted in their northern distribution by temperature. Surface area usually had little effect on the densities of all common species.
Winter Anomalies of Seston, Phytoplankton and Cations in a Colorado (U.S.A.) Alpine Flowage Lake
Authors: Heermann Scott J.
Published: February 2007

Year‐round changes of phytoplankton, organic and inorganic seston, and dissolved and suspended concentrations of Ca, Mg, Na, K, Fe, Mn, Zn, and Cu were studied and correlated in Long Lake, an ultra‐oligotrophic alpine flowage lake of northcentral Colorado, U.S.A. Dissolved cation levels for Ca, Mg, Na, K, Mn, and Fe, both sestonic fractions and phytoplankton densities reached and sustained a maximum during April and May under heavy cover of ice and snow, and a minimum during open‐season from mid‐June to mid‐October. Rates of monthly water renewal varied greatly with a low of 0.28 turnovers in April and a high of 15.37 turnovers in June. Massive flushing in June and July reduced dissolved Fe levels to <0.060 mg/l from a typical maxima >8.0 mg/l in April and May. Tests for linear correlation between the various cations, sestonic fractions and phytoplankton showed in most cases positive and significant (p <.05) relationships. For most dissolved Fe and Mn pairings with phytoplankton and seston exceptionally significant (p < 0.001) relationships were observed.
Some Problems in the Estimation of Chlorophyll‐a and Phaeopigments from Pre‐ and Post‐acidification Spectrophotometrie Measurements
Authors: Moed Jan R. , Hallegraeff Gustaaf M.
Published: February 2007

The rate of conversion of chlorophyll‐a to phaeophytin‐a in dilute acid organic solvents is markedly pH‐dependent. The widely used spectrophotometric measurement before and after acidification to discriminate between chlorophyll‐a and phaeopigments is applicable only between pH 2.6—2.8. At higher pH the reaction proceeds slowly and occasionally may be incomplete. At lower pH complicating reactions may occur, such as breakdown of certain carotenoid pigments causing (time‐dependent) increase of background absorption, and formation of di‐cations of phaeophytin with spectral characteristics different from the usually obtained mono‐cations of phaeophytin. Consequently, it is stressed to control carefully the acid concentration, the water content of the solvent, and the amount of MgCO3 used in the filtration procedure. In general, for the purpose of spectrophotometric acidification experiments, acidification by dilute hydrochloric acid added to organic solvents containing 10—20% water, and omission of MgCO3 would be preferable.

On the basis of observed complications in the red part of the absorption spectrum of the pigment extract, it is recommended to use the above stated pH‐range.
Beiträge zur Morphologie und Entwicklung des Semipoljes Amvrakia (Limni Amvrakia), Westgriechenland. Contributions to the Morphology and Development of the Semipolje Lake Amvrakia (Limni Amvrakia), Western Greece
Authors: Verginis S. , Leontaris S.
Published: February 2007

Lake Amvrakia is judged by the authors to be a semipolje. Chalky formations 1—5 m above present water level indicate that formerly the level was higher.
Composition and Distribution of Caspian Fauna in the Light of Modern Data
Authors: Mordukhai‐Boltovskoi Philaret D.
Published: February 2007

The composition of the Caspian fauna is considered in the light of modern data. The number of autochthonous species known for the Caspian Sea has now reached 435 and the Caspian species in the Pontoazov basin and Lake Aral number 178 and 41 species, respectively, i. e. 25–30% more than stated in the lists in my previous review (1960, 1964). The distribution of the Caspian fauna outside the Caspian Sea is discussed and it is shown that the ranges of many species have diminised owing to unfavourable conditions. However, in some species, especially mysids, the ranges have become substantially larger on account of their artificial acclimatization.
The Size‐Depth Relationship in Deep Ocean Animals
Authors: Polloni Pamela , Haedrich Richard , Rowe Gilbert , Hovey Clifford C.
Published: February 2007

In response to Thiel's (1975). hypothesis that the food‐limited deep sea is a small organism habitat, further data on average size of individuals representing various deep‐sea taxa are presented. Our data were gathered with trawls and box corers between 200 and 5000 meters, in the western North Atlantic. For echinoderms, decapods and macrofauna there appears to be no steady, logarithmic decline in size with increasing depth, but fishes are bigger – deeper.
Résultats de la mission Hydratlante I du N. O. Jean Charcot (au large des côtes atlantiques françaises). 2. Pigments phytoplanctoniques
Authors: Travers Marc
Published: February 2007

Results of Hydratlante I Cruise of R. V. Jean Charcot (off the Atlantic French Coast). 2. Phytoplankton Pignients

Measurements of phytoplankton pigments have been made at all levels and stations prospected during Hydratlante I. In neritic as well as oceanic waters, the chlorophyll a content of seston was low: only 0.07–0.08 mg · m−3 at 5 and 20 m; maximum average value at 50 m: 0.14 mg · m−3. The chlorophyll a content of phytoplankton cells averages 6.2 pg but varies greatly with population density. The plant carotenoids, relatively more abundant than chlorophyll, average 0.7 mg · m−3 at 5 m; 0.9 at 20 m and 1.2 at 50 m. Pigment distributions seem to be largely dependent on thermal structure and nutrient concentration. They are also more or less strongly correlated with water transparency, rate of 14C fixation and organic seston content. Comparisons with previous results in the same area reveal a rather good agreement.
Glucose in Freshwater of Central Amazon Lakes: Natural Substrate Concentrations Determined by Dilution Bioassay
Authors: Rai Hakumat
Published: February 2007

A bioassay method has been employed to measure concentrations of glucose in the Central Amazon lakes. Michaelis‐Menten enzyme kinetics parameters from the 14 bioassay measurements were made during this study. Concentrations of glucose found in Lago Tupé (10–485 μg/1)., Lago Cristalino (8–393 μg/1). and Lago Janauari (1‐485 μg/1). are greater than anticipated. The bioassay method is applicable in determining concentrations of glucose in freshwater of the Central Amazon.
A Comparison of Methods for the Estimation of Phytoplankton Primary Production
Authors: Salonen Kalevi , Holopainen Anna‐Liisa
Published: February 2007

The primary productivity of phytoplankton in several lakes with different trophic status was estimated by radiocarbon and dissolved inorganic carbon (DIG). consumption methods. On an average, the direct DIC consumption method with light and dark bottles yielded 46% higher results than the radiocarbon method. The exact nature of the difference is obscure, but it is suggested that greater attention should be paid to heterotrophic consumption during the experiment than has been done in previous studies, as this is intimately linked with primary production.

The liquid scintillation and Geiger Müller (GM). counts resulted in similar estimates of primary productivity when the radioactivity of the stock NaH14CO3‐solution for the GM method was determined by the biological method of Steemann Nielsen. This and the fairly close agreement of the results with those of the DIC consumption method indicate that the radiocarbon method is equally useful in estimating primary productivity in lakes ranging in status from oligotrophic to very eutrophic.
Experimentelle Untersuchungen zur Anpassung von Fungiiden (Scleractinia, Fungiidae). an unterschiedliche Sedimentations‐und Bodenverhältnisse.
Authors: Schuhmacher Helmut
Published: February 2007

Experiments on Adaptations to Sedimentation and Substrate in Fungiid Corals (Scleractinia, Fungiidae)

Experimental evaluation of the sediment rejecting behaviour in fungiid corals shows: a). sediments easily slide off from cupolate coralla; b). some flat corals inflate the polyp to get rid off sediments; c). in most species sediments are entangled in mucus and removed by ciliary action. However mucus production is limited by the number of functioning mucous cells.

During continuous stress by weighting sediments the tissue overlying the septal ridges gets cut and worn off. Damage instantly occurs in species with sharp septa, but relatively late in those with broad septa. Even minute tissue remains are capable of regenerating trophozoids attached to the old skeleton. Species which endure only low sedimentation rates, are mainly confined to hard bottoms (e.g. reef slope).
Assimilation by Aquatic Oligochaeta
Authors: Brinkhurst Ralph O. , Austin Merelene J.
Published: February 2007

Aquatic oligochaetes selectively ingest material from sediments given as food. Determinations of the quantity of organic material presented, left in the residue, and voided as feces enabled estimation of assimilation. These figures were not significantly different from those obtained by summing growth as observed in the experiment with respiration determined independently. Short term experiments yield estimates of assimilation of 77 to 181 cals/g dry wt/day, long term experiments yield an estimate of 232 cals/g dry wt/day, both for mixed populations of Tubifex tubifex and Limnodrilus hoffmeisteri.
The Horizontal Distribution of Baltic Epi‐ and Metalimnic Zooplankton Species
Authors: Sandström Olof
Published: February 2007

The horizontal distribution of epi‐ and metalimnic zooplankton species in the northern region of the Bothnian Sea was studied in July and August 1975. The distribution was determined by vertical sampling with plankton nets at randomly selected stations in two areas (4 and 8 km2). Most species were clearly nonrandomly distributed in these two sampling areas. Horizontal patchiness within areas of a few km2 could be shown by grouping closely adjacent stations according to similarity or difference in average values. At the individual stations, there were only a few cases where any marked deviations from randomness were found. The age distributions of copepods differed in different parts of the areas. This is thought to be an important factor for the creation of patchiness.
Adsorption of Arsenite by Lake Sediments
Authors: Huang Pan M. , Liaw Wen K.
Published: February 2007

The sediments in Blackstrap Lake, a prairie lake, contain over 90% of the non‐clay fractions and its pH is near neutrality. Calcium and Mg carbonates, sesquioxidic components and their complexes with silica are present in a series of particle size fractions. The major clay minerals of the sediments are mica, montmorillonite, chlorite, vermiculite, kaolinite, and quartz.

Organic matter of the lake sediments is relatively less important in the adsorption of arsenite. Calcium and Mg carbonates, micas, vermiculite, montmorillonite, kaolinite and chlorite are the active components but not the dominant components of the lake sediments in adsorbing arsenite. The porous sesquioxides and silico‐sesquioxidic complexes present in a series of particle size fractions (clay, silt and sand). are the primary components in adsorbing arsenite. The retention of arsenite by these active components present in sediments would suppress the level of arsenite in fresh water and may thus restrain its movement to the food chain.
Seasonal Changes of Bacterioplankton in a Reservoir Related to Algae. I. Numbers and Biomass
Authors: Straškrabová Vêra , Komárková Jaroslava
Published: February 2007

A reservoir for drinking water supply was studied at 10 day intervals for one season. Changes in bacterial microscopic counts and chlorophyll and algal biomass showed a similar pattern. Bacterial peaks usually lagged slightly behind the algal maxima. Average volumes of bacterial cells, corrected for shrinkage, were mostly lower than 0.2 μm3. The average concentration of bacterial C in water was estimated to be 18 μg μg 1 −1 (from a volume biomass of 0.09 mm3 per litre). Several years' fluctuations in bacterial numbers were compared with hydrological data and phyto‐ and zooplankton changes.
Caracteristiques du microphytobenthos d'un lac volcanique meromictique (Lac Pavin, France). I. Biomasse chlorophyllienne et déterminisme du cycle annuel
Authors: Romagoux Jean‐Claude
Published: February 2007

Characterization of the Microphytobenthos in a Volcanic Meromictic Lake (Lake Pavin, France). I. Chorophyll Biomass and Determination of the Annual Cycle

The sediments in Lake Pavin are almost exclusively biogen. The fine fraction (≤ 40 μm). comprises 99% of these sediments, making them appear as very fine and fluid silt. Up to 85% of the microphytobenthos is composed of epipelic Bacillariophyceae. The benthos at the different depths studied (10 m, 20 m, 30 m, 40 m, 50 m, and 60 m). are colonized by characteristic populations of diatoms. Analyses of the sediments revealed high concentrations of pigments ( ≥ 1 mg/g dried sediment). Such high concentrations usually result from phytoplankton sedimentation. The deepest area of the lake, as expected, contains the highest concentation of accumulated pigment, while shallower locations are richer in active pigments.
The Availability of Condensed Phosphates for the Algal Strain Scenedesmus obtusiusculus Chodat, with Special Regard to Conditions Characteristic in Lake Balaton
Authors: Dobolyi Elemér , Ördög Vince
Published: February 2007

The limiting factor in the water of Lake Balaton was calculated by means of Verduin's equation. If only the orthophosphate‐phosphorus concentration is inserted into the equation, phosphorus is the primary limiting factor. If, however, total phosphorus is considered, the factor intensity of nitrogen will be the least, i. e. nitrogen will be the primary limiting‐factor of plant growth. According to measurements during 1976, average values for the total dissolved phosphorus and orthophosphate‐phosphorus content of Balaton Lake water were 15,66 mg/m3 and 7.66 mg/m3, respectively. Experiments with the algal strain Scenedesmus obtusiusculus Chod. (Chlorophyceae, Chlorococcales). were designed to test the availability of the condensed phosphorus form for the algae. The experiments were performed partly with synthetic polyphosphates, partly, with polyphosphates isolated from Balaton Lake water. The results showed, contrary to our expectations, that phosphates present in the condensed form (irrespective of their structure and degree of condensation). were not utilized by the algae under sterile conditions, i. e. in the absence of bacterial activity. In the light of the above it is recommended to consider only orthophosphate‐phosphorus when calculating the limiting factor.
Effect of Nutrient Inflow on the Bacterial Flora in the River Sakuragawa, Japan
Authors: Seki H. , Takahara Y.
Published: February 2007

The relationship between nutrient level and microorganisms in the waters of the River Sakuragawa, Japan, was studied from 1976 to 1977. Statistical analyses show that the organic nutrients for the bacteria were mainly autochthonous, and that the water system of the River Sakuragawa was never polluted enough to fall into a condition that could be classified as dystrophic.
Sur la taxonomie et l'éthologie de quelques Orbioninés (Isopoda Epicaridea).
Authors: Bourdon Roland
Published: February 2007

La détermination des Orbioninés de Madagascar (Bourdon, 1979). nous a amené à examiner les types de certaines autres espèces ainsi que des spécimens de provenance variée. Nous présenterons ici les observations morphologiques ou faunistiques nouvelles effectuées sur ce matériel. Sur le plan de la systématique, cet article comprend la description de Parapenaeonella lamellata n. sp. et d'Epipenaeon ingens latifrons n. ssp. et, conséquence d'une meilleure connaissance de la variabilité intra‐spécifique dans la sous‐famille, la mise en synonymie d'Orbione halipori var. libera, O. natalensis, Epipenaeon nobilii et E. grande.
The Effect of Natural and Artificial Shade on the Macrophytes of Lowland Streams and the Use of Shade as a Management Technique
Authors: Dawson F. H. , Kern‐Hansen U.
Published: February 2007

The reduction of the biomass of three main problem species of submerged aquatic macrophytes was proportional to the light at the stream surface both under artificially shaded sections of stream and in naturally shaded areas when compared to the biomass in adjacent open and unshaded sections of stream. The effect of marginal vegetation in varying the shading effect given to streams of differing width and orientation are described. It is recommended that light should be reduced to about half that presently available in the open, by shading from marginal vegetation but it is warned that too much shade is detrimental to the fish populations of the stream and leads to accentuated local accumulations of leaves. The long term effects are considered but it is expected that partial shading will increase the diversity of submerged plant species. It is suggested that the practice of stream realignment is discontinued and that the natural tendency of streams to create their own meandering channels is allowed but within some defined and generally acceptable framework.
Relations between Phytoplankton and Light Climate in two Swedish Forest Lakes
Authors: Ramberg Lars
Published: February 2007

The succession, biomass and production of phytoplankton was studied during 7 years in two Swedish forest lakes in relation to nutrients, temperature and light climate. The succession of species and taxonomic groups can be described by their different demands concerning temperature and light climate while the total biomass is correlated to light climate and total phosphorus concentration. Differences in production between the two lakes can be explained by different taxonomic groups having different efficiencies.
Development of the Periphytic Community on Artificial Substrates in Fish Ponds
Authors: Markošová Ružena
Published: February 2007

The development of the periphytic algae and macrofauna was examined in two fish ponds. 43 genera of algae (mainly diatoms) were found on the substrates, and the maximum of algae was reached on the 10th day. The periphytic macrofauna consisted of 37 taxonomical groups (mainly Chironomidae). Larvae of Cricotopus intersectus were the most abundant species. Since the 2nd day of exposure, the number of Cricotopus larvae strongly increased by immigration of 2nd instars until the maximum was reached on the 15th day. No further significant oscillations were found in either the algal or animal component until the 75th day of exposure.

The field observations and laboratory experiments confirmed that:

The distribution of frequencies of Cricotopus larvae found on 200 cm2 surfaces could be approximated by the normal distribution.

The density of the algal periphyton is controlled by abiotic factors, not by grazing by chironomid larvae.

The Cricotopus larvae of the 2nd instar colonize the substrate only after the algal film has been formed. Later instars are sedentary and do not colonize new substrate (except under stress conditions).

Food and predation do not seem to be the factors controlling the Cricotopus population density. The main factor is considered to be the territorial behaviour of the larvae.
The Freshwater Zooplankton of Sri Lanka, with a Discussion of Tropical Freshwater Zooplankton Composition
Authors: Fernando C. H.
Published: February 2007

Based on the study of over 500 zooplankton samples collected in Sri Lanka (Ceylon) during 1965–1974, the species composition from different habitats is analysed. The zooplankton assemblage is typically tropical with relatively few species of Cladocera and Copepoda. The Rotifera include a large number of species of the genus Brachionus. The limnetic zooplankton resembles the pond zooplankton closely in that all the eurytopic species found in the different types of habitats, including ponds, also occur in the limnetic zooplankton. The large Cladocera belonging to the genus Daphnia are very rare. In general, large zooplankters are absent. The size composition of the zooplankton has a smaller range than in temperate regions. This is due to the absence of large‐sized zooplankton species.

The reasons for the differences in species variety and size composition between zooplankton of temperate and tropical regions is perhaps due to a number of factors. These include the effects of high and uniform temperatures, food availability and predation by fish and invertebrates.
The Rotifera of Hummock‐Hollow Formations in a Poor (Mesotrophic) Fen in Newfoundland
Authors: Bateman Lois E. , Davis Charles C.
Published: February 2007

Rotifers encountered from a poor (mesotrophic) fen, Avalon Peninsula of Newfoundland, are listed. Sixty‐four species and varieties, including 25 Bdelloidea and 39 Monogononta, were recorded. All but 4 of the reported species and varieties are new records for the Province of Newfoundland, while 27 are new records for Canada; of these, 13 are new for North America.

A seasonal quantitative study of rotifer communities in the hummock‐hollow formations on the fen was carried out from August 1973 to October 1974. An average of 354 rotifers/cm2 (17 species) was found per formation. Monogononta almost totally disappeared during winter, while the Bdelloidea decreased somewhat in numbers. The tops of hummocks contained mainly bdelloid species. The number of monogononts increased both in species and individuals on the slopes of hummocks and was greatest in the hollows, although the total number of rotifers was less in these areas than in the hummock tops.

Some physical and biological factors affecting the rotifer communities were examined. Rotifers in these sites are not subjected to dessication. Predation was not an important factor.

A quantitative sampling method was devised for procuring relatively accurate samples from living Sphagnum, and for extracting rotifers from these samples.
Acidification of a Small Watershed in Southern Norway and Some Characteristics of Acidic Aquatic Environments
Authors: Nilssen Jens Petter
Published: February 2007

Continuous monitoring of a small watershed in southern Norway shows that pH has decreased significantly by almost half a unit (from 5.9 to 5.4), conductivity increased from 23 to 29 μS/cm within the period from 1965–1975. Changes are also detected in sediment analyses where Daphnia and Chaoborus are only found deeper than 3–4 cm. Forest clear‐cutting activities have probably accelerated the acidification processes of the already highly vulnerable freshwater localities. The acidic lakes show a solute content below 0.4 meq/1, and the bicarbonate buffer system may no longer work efficiently. Spring thaw and autumn rain episodes are accompanied by strong alternations in the chemical environment of the lakes; by considerable drop in pH and increasing conductivity and sulphate content. With increasing acidification the planktonic community changes from a fish predation governed system (brown trout and Eurasian perch as dominant species) to an invertebrate predation governed one with dominant predators Heterocope and pelagic corixids. Pelagic zooplankton are primarily composed of littoral species: Bosmina longispina, Diaphanosoma brachyurum, Eudiaptomus gracilis and Heterocope saliens. The littoral plant and invertebrate communities are described and discussed.
Seasonal Distribution of Phytoplankton in Yellowknife Bay, Great Slave Lake
Authors: Moore James W.
Published: February 2007

The factors influencing the seasonal distribution of phytoplankton were determined between July 1975 and December 1977 in Yellowknife Bay, Great Slave Lake. The initiation of the spring bloom occurred during April of each year in response to changing light conditions and despite the 0 °C water temperatures. Although the plankton showed some fluctuations in density (100–400 mg/m3) during the summer, there was no vernal decrease in the size of the populations. The end of the growing season was characterized by a sharp drop in numbers near the end of October. Multiple regression analysis indicated that changes in the standing crop of the plankton during the summer were primarily related to temperature (r = 0.60) and the concentrations of NO3–N (r=–0.74) and SiO2 (r=–0.82). Changing light conditions probably had little effect on the population during the growing season.

Chlamydomonas lapponica was dominant during April of each year. While the growth of this species caused a reduction in the concentrations of total phosphorus and NO3–N, the level of SiO2 remained constant and consequently diatoms (Asterionella formosa, Stephanodiscus astraea, Diatoma tenue var. elongatum and Melosira islandica) waxed rapidly during May. By the first of June, nutrient concentrations were low, thereby permitting the development of Dinobryon bavaricum and Dinobryon cylindricum. The extremely rapid decrease in the densities of common species during the fall was probably due to the rapid decline in temperature and light levels and the formation of ice on the bay.
On the Mechanism Reducing the Phosphate Concentration in the Water of Lake Balaton
Authors: Dobolyi Elemér , Herodek Sándor
Published: February 2007

The aim of the investigations was to identify the main process controlling the rather low phosphate concentration in the water of Lake Balaton. Three processes were taken into consideration: a) phosphate uptake by algae, b) coprecipitation with biogenic lime, and c) adsorption on suspended sediment particles. A plexiglass box open at the bottom was placed in the shallow water with its sides extending into the sediment. The water in the box was stirred. When phosphate alone was added to the water in the box, its concentration decreased very rapidly. On the other hand, if NaOCl was also added in order to kill algae and bacteria, the phosphate concentration remained constant. This proves the priority of life processes in phosphate removal. In the next experiment phosphate and EDTA‐Na2 were added simultaneously to the water in the box. The complexing agent prevented biogenic lime formation but did not influence the rapid phosphorus removal. This fact indicates that the main process involved in phosphate control is direct uptake by algae. The same conclusion was obtained in laboratory experiments where labelled phosphate was added to the bottles containing Lake Balaton water. It was demonstrated by the photo‐oxidation technique that the phosphate removed from the water was incorporated into the organic particulate matter.
The Species and Size Composition of Tropical Freshwater Zooplankton with Special Reference to the Oriental Region (South East Asia)
Authors: Fernando C. H.
Published: February 2007

A contrast between temperate and tropical Cladocera, Copepoda and Rotifera zooplankton fauna shows a markedly different size composition and species diversity. There are fewer species, and these are generally smaller in the tropics than in either the North or South Temperate Zones. Larger species of the generaDaphniaandSimocephalusare relatively rare in the tropics, while members ofEurycerusandSayciaare absent. Members of the families Holopedidae, Leptodoridae and Polyphemidae increase in abundance toward the temperate regions. Two small cyclopoid copepods are common in tropical zooplankton, while many of the common larger species of other regions are absent or very rare. The chief rotifer components areKeratella tropicaand species ofBrachionus.
Automated Pattern Recognition of Phytoplankton – Procedure and Results
Authors: Schlimpert Olaf , Uhlmann Dietrich , Schüller Martina , Höhne Erhard
Published: February 2007

Pictures of phytoplankton samples were analyzed as raster images by means of a television camera and a Robotron 4200 computer. A feature vector described the objects irrespective of their angle. Each of the five genera involved were identifiable by a characteristic point cluster in a p‐dimensional feature space. A learning method was used during development of the classification structure, and the quality of identification was increased incrementally to the greatest possible degree.

Asterionella formosa was identified in all cases without error despite the relatively coarse scanning grid. Errors in the identification of Fragilaria crotonensis can be reduced by improving the resolution (over 100 picture elements per colony).
Contribution to the Study on Bottom Sediment in Lake Balaton. I. Determination of Phosphorus Minerals in the Sediment
Authors: Dobolyi Elemér , Bidló Gábor
Published: February 2007

The aim of the investigation was to determine the phosphorus containing minerals present in Lake Balaton sediment. Chemical, electron microscope and X‐ray diffraction analysis succeeded in identifyinghydroxylapatite.No proof was found for the presence of other phosphorus minerals.
Salinity Tolerance in Some Selected Aquatic Oligochaetes
Authors: Chapman Peter M. , Brinkhurst Ralph O.
Published: February 2007

Salt tolerance of the freshwater tubificid Limnodrilus hoffmeisteri varied from an LD 50 of 10 ppt to 10.5 ppt for mature and immature worms without sediment, 9.4 to 10.5 in sand, and 14.3 for immatures acclimated to 5 ppt. Ilyodrilus templetoni was similarly intolerant to higher salinities. The estuarine Tubificoides gabriellae tolerated salt water, but was susceptible to freshwater, with LD 50's of 2 and 3.5 when acclimated to 5 and 10 ppt sea water. It survived immersion in freshwater for 3 hours. The estuarine naidids Paranais litoralis and frici experienced mortalities at both high and low salinities but showed a wide tolerance range. The coastal tubificid Monopylephorus irroratus showed almost complete tolerance to the salinity range employed. The findings reflected field distributions especially when interstitial salinities were measured, but worms did not occupy the full range of habitats possible in terms of salinity alone.
Notobaetis: A New Genus of Baetidae (Ephemeroptera) from South America
Authors: Morihara D. K. , Edmunds George F.
Published: February 2007

A new genus and species, Notobaetis penai, n. gen., n. sp., of Baetidae (Ephemeroptera), is described based upon reared specimens collected from the Cordoba Province of Argentina. This new genus appears to be phenetically intermediate between Baetis Leach and Centroptilum Eaton while possessing a unique combination of characters and one autapomorphic character.
The Non‐swimming Chydorid Cladocera of Wet Forests, with Descriptions of a New Genus and Two New Species
Authors: Frey David G.
Published: February 2007

Included among the diversified aquatic fauna occurring in the water associated with bryophytic coverings of cloud forests and rain forests and with the bottom litter of such forests are two closely related species of chydorid Cladocera – Bryospilus repens gen. et sp. nov. known from Puerto Rico, Venezuela, and New Zealand, and Bryospilus bifidus gen. et sp. nov. known only from New Zealand. Beyond the certainty that these species belong in the subfamily Aloninae because of the nature of their mandible articulation, the location of the minor headpores in a far lateral position, and the general pattern of setation on the trunk limbs, little more can be said. In several respects, most strikingly the lack of a compound eye and certain peculiarities of the mandible articulation, Bryospilus resembles Monospilus more closely than any other chydorid, although this may have resulted from convergence. The species are quite unique in their reduction of setation on the antennae and trunk limb I. The animals cannot swim. Instead they crawl about slowly but effectively in the wet bryophytes and forest litter. They have been collected from as high as 3–5 m above the forest floor, presumably having got there by their own efforts. This habitat is suspected to be comparable in its continuity over time to the ancient lakes of the World and hence can be expected to harbor other “endemic” species as well.
The Phytoplankton Biomass and Species Composition at Two Stations in Western Lake Erie, 1975/76
Authors: Gladish D. W. , Munawar M.
Published: February 2007

Integrated phytoplankton samples from two stations in the northern waters of western Lake Erie were analyzed by the Utermöhl technique for the period from June, 1975 to September, 1976, with weekly sampling in the summer of 1975. No consistent differences were observed between the two stations. Two annual peaks were found: the first was a vernal pulse (1.4 to 4.8 g/m3) comprised primarily of diatoms (86.0–95.7% of total biomass; principal species were Tabellaria fenestrata (Lyngb.) Kg., Stephanodiscus hantzschii Grun., and Fragilaria capucina Desm.); the second peak (3.1 to 9.9 g/m3) was in late summer – early fall. This latter peak consisted of initially diatoms (Coscinodiscus rothii Ehr. Grun. and Melosira granulata (Ehr.) Ralfs being the chief components), later dominated by bluegreens (Aphanizomenon flos‐aquae (L.) Ralfs and Chroococcus minutus (Keutz.) Naegeli), and finally diatoms (Coscinodiscus rothii, Stephanodiscus spp., Fragilaria crotonensis (Edw.) Kitton, and Melosira granulata). The importance of phytoflagellates (25.5 to 93.4% of total biomass), especially Gymnodinium sp., Cryptomonas erosa Ehrb., and Cryptomonas erosa v. reflexa Marsson., in June – early July samples and the overwhelming dominance of diatoms during the remainder of the year are stressed. No patterns in biomass and composition could be observed in vertical phytoplankton profiles. The present study provides an important connecting link between past and future studies performed with the standard Utermöhl technique.
Nutrient and Sediment Retention in a Temperate Marsh Ecosystem
Authors: Maccrimmon Hugh R.
Published: February 2007

The Wye marsh, an undeveloped wetland of 639.9 ha, serves as a receiving water for a 19,600 ha agricultural watershed before discharging into the Great Lakes. Seasonal and diel changes in limnological variables, most notably nitrogen, phosphorus, silica and turbidity, have been examined in the Wye river, marsh and discharge waters over an 11‐month period and related to the composition of marsh sediments. Retention rates of the marsh ecosystem for incoming nutrients and suspended solids have been estimated by calculations of mean monthly inflow to outflow ratios using the levels of these factors in the Wye River and the marsh discharge. Calculated mean monthly retention rates of the marsh for incoming nutrients is estimated at no less than 61% for nitrogen‐N, 36% for total phosphate, and 14% for soluble silica during the ice‐free period. Based on observed turbidity levels, the retention of incoming suspended solids is estimated at 65% for the same period. The Wye marsh is a substantial sump for inorganic and organic materials which are retained within the water column, biomass and unconsolidated sediments.
Eine neue tropische Unterart von Keratella cochlearis (Rotatoria)
Authors: Thomasson Kuno
Published: February 2007

A new subspecies of Keratella cochlearis, viz. Keratella cochlearis pachyacantka is described. It has been recorded from Africa and South America.
The Occurrence of Bulbella abscondita (Bryozoa, Ctenostomata) in Brackish Waters of Northern Italy
Authors: Jebram Diethardt , Pisano Eva
Published: February 2007

The victorellid bryozoans, Tanganella muelleri and Bulbella abscondita, have been found in the delta of the River Po, Northern Italy. Our finds seem to be the first recorded of B. abscondita in waters in Italy.
The Role of the Limnologist in Ground Water Studies
Authors: Danielopol Dan L.
Published: February 2007

The following topics are discussed: the advantages of an interdisciplinary approach to ground water studies; the porous aquifer as an open system; the problem of the terminology used in ground water ecology; the interest of ecologists in hydrogeological terminology; biological activity in the unsaturated zone of porous aquifers; the distribution of ground water fauna in the saturated zone of porous aquifers; ground water animals as environmental indicators; the manipulation of ground water ecosystems; basic lines for the further development of ground water ecological studies.
A Study of the Excretion and Extracellular Products of Natural Phytoplankton in Lake Nakanuma, Japan
Authors: Watanabe Yasunori
Published: February 2007

Excretion of photosynthetic products by phytoplankton in Lake Nakanuma ranged from 8 to 54% of the total carbon assimilated. Percentage of excretion increased under the conditions of high and very low light intensity, low temperature and nutrient deficiency. Estimated daily production of extracellular products in the lake was about 150 mg C/m2 in the summer season and the major components of it were glycolic acid, polysaccharides and polypeptides.
Caractéristiques du microphytobenthos d'un lac volcanique. Characterization of the Microphytobenthos in a Volcanic Meromictic Lake (Lake Pavin, France). II. Productivity and Relationships
Authors: Romagoux Jean‐Claude
Published: February 2007

The collection of microphytobenthos for primary production studies in Lake Pavin was performed with a Jenkin sampler. This corer permits sampling at different levels below the surface of the lake. Five levels (10, 20, 30, 40, and 60 m below the surface) were regularly investigated for more than one year. Each was inhabited by a characteristic population of dominant diatoms. The primary production, which was very large during the summer, decreases with depth. During the winter, the 14C assimilation occurs at a very low rate in clear incubators, but in dark incubators, the rate is high. Therefore, the 14C fixation in darkness is greater than the photosynthetic assimilation. This phenomenon together with the very important data recorded for photosynthetic efficiency (especially at the lowest levels, 40 and 60 m deep) suggest that microphytes on the bottom of the lake assimilate organic compounds during much of the year.