bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Submerged Macrophytes in the Treated Sewage Channel Wuhle (Berlin, Germany)
Authors: Körner S. , Kühl H.
Published: February 2007

The environmental conditions for submerged macrophytes in sewage channels are different to those of natural waters. Mainly 6 eutraphent species occur in two communities on the flowing stretch of the Berlin treated sewage channel Wuhle. The survival time of the above ground biomass of the annual species is relatively long due to the higher water temperatures in winter. The average biomass of the different parts of the flowing stretch is between 50 and 830 g DM/m2 in summer. With decreasing concentrations of ammonia and BOD an increase of the biomass and the colonization density could be noticed over the last few years.
A Proposed Framework for the Management of Water Quality in Arid‐Region Lakes
Authors: Parparov Arkadi , Hambright K. David
Published: February 2007

For arid‐region lakes, management conflicts are likely to occur between quantity and quality of water supplied: increasing quantity of water supply can lead to water quality deterioration. Such conflicts can best be resolved within an effective management program based on awareness and cooperation at all levels of water management from policy makers to experts. We propose a general framework for designing effective water resource management programs for lakes based on concrete definitions of management criteria such as water quality. The proposed system requires close interaction between policy makers, water resource managers, water suppliers and users, hydrological engineers and limnologists. The significance of mathematical modeling as a self‐organizing tool of the management program is emphasized, especially with regards to designing limnological investigations directed toward lake management. We illustrate the application of this approach to water resource management in arid‐region lakes (Lake Kinneret, Israel and Lake Sevan, Armenia), where artificial variability of lake morphometry due to water use is a forcing function affecting water quality.
Bionomy of Macrobenthic Molluscs in Evros Delta (North Aegean Sea)
Authors: Kevrekidis T. , Gouvis N. , Koukouras A.
Published: February 2007

The composition and distribution of the macrobenthic molluscs in Evros Delta (North Aegean Sea) were investigated by quantitative sampling. The molluscan distribution shows a zonation mainly related to the degree of “confinement”. Based on similarity in distribution among stations, 2 groups of species were distinguished. One group includes marine species (Tellina tenuis, Bittium reticulatum) found only in coastal stations and the second group is typical of estuarine species (Hydrobia acuta, Abra ovata and Cerastoderma glaucum) distributed in almost all stations. Spatial fluctuations of the 3 estuarine species reflect their preferences in the various parameters (“confinement”, salinity, grain size and organic matter of sediment). The most isolated stations support the highest values of total mollusc abundance and biomass.
Prey Selection by the Water Bug Aphelocheirus aestivalis Fabr. (Heteroptera: Aphelocheiridae)
Authors: Lemb Markus , Maier Gerhard
Published: February 2007

Feeding experiments were conducted in situ in flow through boxes to determine the vulnerability of different prey types (the mayfly larvae Baetis, Ephemerella and Ecdyonurus spp., the caddisfly larva Hydropsyche spp. and the crustacean Gammarus spp.) to the predaceous water bug Aphelocheirus aestivalis and to estimate the predation impact of Aphelocheirus on prey populations. Experiments with equal densities of mixed prey and experiments where each prey was tested individually revealed that Baetis and Ephemerella were most vulnerable to Aphelocheirus predation: Hydropsyche, Ecdyonurus and Gammarus were little/not preyed upon. The present results suggest that vulnerability of prey depends mainly upon prey mobility and microhabitat overlap between predator and prey and that feeding behaviour of Aphelocheirus resembles more that of megalopterans than of stoneflies. Experiments with different prey densities (120–720 prey m−2) showed that the predation rate of Aphelocheirus increased with increasing prey density. Experiments with different substrates documented that mortality rates of prey decreased with increasing substrate complexity. When substrate conditions were complex mortality rates in the control and in the experimental boxes were the same which suggest little importance of Aphelocheirus predation on mayflies in the study site.
Diurnal vertical migration study during a winter bloom of Cryptophyceae in a floodplain pool
Authors: Pithart David
Published: February 2007

The diurnal vertical migration (DVM) of the phytoplankton community was studied in a small (270m2), shallow (1.8m), and frozen floodplain pool. Steep vertical gradients were detected in O2, NH4+‐N, NO3−‐N and PO43‐‐P profiles. The phytoplankton of the pool is characterized by year round dominance of Cryptophyceae: Cryptomonas curvata and Cryptomonas marssonii created more than 90% of total phytoplankton biomass during the time of study. DVM was studied by analysing vertical profiles six times during a 24 hour cycle; samples were taken at 20 cm intervals along the profiles. Koliella planktonica, the only non‐motile alga, showed a stable uniform distribution. Dinobryon divergens and Chrysococcus rufescens created a stable distinct concentration maximum at 40cm. Unlike these three species, both Cryptomonas spp. actively changed their position during the 24 hour cycle with distinctive evening downward and morning upward migration. The absence of filtering zooplankton excluded its influence on the patterns of phytoplankton DVM. The results showed the key role of PhAR (Photosynthetic active irradiance) in day ‐ positioning of Cryptomonas. Night‐time uptake of phosphate and/or ammonium at the bottom is probable, although direct evidence is lacking.
Thiamine dynamics in aquatic ecosystems and its biological implications
Authors: Niimi Arthur J. , Jackson Chung‐Ja C. , Fitzsimons John D.
Published: February 2007

Thiamine concentrations were monitored in various organisms ranging from plankton to fish in the Lake Ontario ecosystem. The low concentrations found in most samples indicated thiamine levels were not strongly influenced by the trophic status of an organism. A similar conclusion was indicated from data reported by other studies in freshwater and marine ecosystems. Thiamine is produced by microbes and microalgae, and is acquired by higher trophic level organisms through the diet. The issue of thiamine deficiency in wild fish was also examined. It was concluded that increased dietary consumption of prey containing thiaminase was an important factor that can reduce thiamine levels in higher trophic level species.
Effects of a seasonal salinity change on periphyton biomass in a shallow tropical lagoon
Authors: Arfi Robert , Bouvy Marc , Luquet Pierre
Published: February 2007

In the Ebrié Lagoon (Cǒte d'Ivoire), growth of periphyton on bamboo stuck in the sediment is at the basis of the acadja, a low‐cost system developed in order to enhance aquaculture of omnivorous fish like the tilapia Sarotherodon melanotheron. A survey based on hydrological, bacterial and algal data (including phytoplankton and periphyton) was conducted from November 1992 to June 1993 in an experimental structure. Climatic and hydrological seasonality was marked during the study. Succeeding to a rainy season, the oligohaline situation starting in November was characterized by low bacterial and chlorophyll biomass attached to the bamboo (respectively 1 and 18 mg m−2). The mesohaline situation observed from January featured a sharp increase in periphyton biomass, with a maximum in April (16 and 177 mg m−2 for bacterial and algal biomass, respectively). The flood of the Agnéby river, induced in June by the local rains, originated again oligohaline conditions. The biomass decrease observed in May and June resulted from a shift towards low salinity (from 9.8 to 1.8 psu), a decrease in light availability (combined effects of a decreasing solar radiation during the rainy season and an increase of water turbidity due to the flood) and a lower phytoplankton biomass (therefore limiting the secondary epiphytism potentialities). In this shallow tropical environment characterized by high nutrient concentrations (due to local hydrology and organic nature of the substrate), the combination of seasonal variations of climatic (light availability), hydrological (salinity) and biological (abundance or lack of epiphytic algae) seems to control the periphyton biomass growing on bamboo. Therefore, marked seasonality in the production of resource available for the target fish would limit the interest of the acadja as an aquaculture system in brackish ecosystems.
Behavioural responses of different blackfly species to short‐term oxygen depletion
Authors: Kiel E. , Frutiger A.
Published: February 2007

Behavioural changes of four larval blackflies (Simulium noelleri, S. ornatum (complex), S. trifasciatum [syn. S. spinosum] and S. variegatum) to experimental reduction of dissolved oxygen were investigated with videotechniques. Since these species are characterised by different habitat preferences, they were expected to respond differently to oxygen depletion. During experiments lasting 120–140 min., dissolved oxygen (DO) was reduced to 0.3–0.6 mg/1 within the first hour and kept constant for another hour. Water velocity in the laboratory channel was 135 cm/s. Transparent plastic walls allowed video‐recording of larval behavioural responses to oxygen depletion. Blackflies did not engage in undulative or other ventilation movements, and they did not increase locomotory activity, nor did they actively drift. Oxygen depletion mainly altered filter‐feeding activity and non‐locomotory movements (bending and sweeping). With decreasing DO concentrations larvae of all four species reduced and finally ceased filter‐feeding. Non‐locomotory movements first temporarily increased and then also ceased, except in S. variegatum, where these movements were immediately suspended. DO‐threshold values for cessation of filter‐feeding and movements, as well as mortality indicated S. variegatum to be the most sensitive species in respect to oxygen depletion, while S. noelleri seems to be the most tolerant among the four blackfly species tested here.
Some physical and biological factors affecting a spring‐summer phytoplankton dynamics in a shallow, temperate lake of South Andes (Argentina)
Authors: Queimaliños Claudia P.
Published: February 2007

The phytoplankton dynamics of Laguna Ezquerra (Río Negro, Argentina) was analysed on the basis of high frequency sampling, each 3–4 days during a spring‐summer period, in relation to physical factors and to the zooplankton community structure. The phytoplankton biomass presented a marked seasonality, accompanied by similar seasonal patterns in temperature and zooplankton dynamics. Community variations were reflected in the diversity, dominance and equitability values. The greatest change was associated during a short flooding period produced in late spring. The wind exposure was irregular during the whole study period, and was assumed to be a factor of stress for the phytoplankton growth. During spring and early summer, the phytoplankton community was dominated by nanoplanktonic forms likeRhodomonas lacustris, and the large sizedAsterionella formosapresented an exponential increment at late summer. ThisAsterionellagrowth permitted to affirm that the community evolved towards plagioclimatic stages, attending the highly disturbed conditions of the shallow and wind exposed environment.
Nitrogen and carbohydrate pools of two rhizome types of Phragmites australis (Cav.) Trin. ex Steudel
Authors: Woitke Peter , Kiehl Annette , Kühl Harald , Kohl Johannes‐Günter
Published: February 2007

Carbohydrate and total nitrogen contents as well as free amino acid (FAA) concentrations were determined in distinct types of rhizomes of two genetically homogeneous stands of reed (Phragmites australis (Cav.) Trin. ex Steudel) differing in morphology, productivity and nutrient supply in order to evaluate the storage capacity of vertical rhizomes and expansion rhizomes. The expansion rhizomes possess significantly higher amounts of FAA and of total nitrogen but similar carbohydrate concentrations in comparison to the vertical rhizomes. However, no significant differences were found for total nitrogen, FAA and total carbohydrates between both investigated stands indicating a comparable storage capacity of rhizomes independent of nutrient availability. Only the composition of the FAA pool varied in the alanine/asparagine ratio probably influenced by the oxygen supply of the rhizome/root system.
Determinations of clusters, functional groups and variants among lake and catchment area variables
Authors: Håkanson Lars
Published: February 2007

A cluster is a family of variables showing high internal correlation. For example, conductivity, hardness and Ca‐concentration which generally appear with correlation coefficients (r) > 0.8 for mean annual values among lakes. They indicate the amount of salts and ions in the water. A functional group is a family of variables which describe a particular process or mechanism in an ecosystem, like mean depth relative depth and volume development. All of these could be related to resuspension. Such variables would also constitute a cluster if they are well correlated across many lakes belonging to a given lake type. These three parameters express different form elements of lakes, they belong to the same functional group in contexts of lake resuspension, but they do not constitute a cluster since they are only rather poorly correlated (the r‐values between these parameters is generally <0.5). A variant is a value for a given variable from a defined period of time, like a mean annual or monthly value. One can then ask: Which variant from which time period should be used in relation to a given y‐variable one wants to predict to obtain a model with a high predictive power? Variables belonging to the same cluster can often replace one another in models without significantly altering predictive accuracy. The aim of this work is to determine clusters among standard groups of water variables, lake morphometric parameters and catchment parameters. The analysis uses a comprehensive data‐set from 95 Swedish lakes. There are about 83,000 lakes in Sweden, about 81,000 belong to this lake type of glacial lakes, which is the most common lake type on Earth. Selected results: Among the catchment parameters, one may note that the proportion of lakes does not co‐vary closely with any other parameter, but that the percentage of morainic soils is negatively associated with the area covered by bedrock and flat rocks. Two clusters of morphometric parameters can be identified: Size parameters (e.g., volume and area) and form parameters (e.g., relative depth and dynamic ratio). Among the water variables, colour, iron concentration and Secchi depth are strongly correlated. The concentration of total phosphorus, which is functionally associated with the production of algae, is also related to Secchi depth.
Population dynamics of autotrophic picoplankton in a southeastern U.S. Reservoir
Authors: Ochs Clifford A. , Rhew Kyeongsik
Published: February 2007

Reservoirs typically exhibit a gradient along their longitudinal axis in turbidity, nutrient flux, and algal biomass. We utilized these characteristics to examine factors influencing temporal and spatial patterns in abundance, biomass, composition, and production of epilimnetic autotrophic picoplankton (APP) in Sardis Reservoir, Mississippi, USA. Over a 18‐month period, APP abundance varied between about 15,000 and 700,000 cells ml−1. Both APP abundance and APP biomass were closely linked to APP production and temperature. On an annual basis, the contribution of APP to total algal biomass and light‐standardized production ranged between 15–47%, and 5–40%, respectively. Prokaryotes comprised more than 95% of all APP in summer, but eukaryotes dominated the APP community in winter. During the nutrient‐depleted summer period, APP decreased in number but tended to increase in the percentage of total algal biomass and production, from the uplake riverine zone to the downlake lacustrine zone. Only in the second year of the study, when reservoir water residence time was more than four times greater than in the first year, were there significant differences in biomass and productivity of APP between the uplake and downlake regions. We suggest that, particularly in years or at times of the year when water‐flow through the reservoir is slow, the importance of APP in Sardis Reservoir reflects a spatial and temporal gradient in nutrient availability.
Gradients of nutrients, dissolved oxygen and sulfide in wave‐protected and unsheltered stands of Phragmites australis
Authors: Rolletschek Hardy
Published: February 2007

The horizontal and vertical distribution of TN, TP, TC, and TIC in littoral sediments and O2 and total soluble sulfide (∑S2‐) in the overlying water was determined to assess characteristic patterns and the extent of littoral accumulation in Lake Müggelsee. Wave extinction by helophytes allows the formation of deposition zones at the land/water‐interface and inside the reed bed. Organogenic sediments (LOI >60% dm, TP >1.2 mg P/g dm, TN >2% dm) declined non‐linear towards open water. Additionally, irregular periods of anaerobiosis and increased ∑S2‐ concentrations (1.316 μg S2‐/1) were measured. Wave breakers, which were built in front of mechanically damaged reed significantly promote littoral accumulation and protect deposition zones from erosion. However, embankment with fagots produces a fine‐grained organogenic mud towards open water. These sediments revealed significantly increased O2 consumption rates (610 mg O2/m2 · d) and steeper gradients of NO3−, SO42‐ and CH4 indicating intensified anaerobic reduction processes when compared with unsheltered sites. The nutrient gradients differed from those of ‘natural’ accumulation zones and caused diminished O2 saturation (by 30%) specially in summer months. ∑S2‐ concentration was positively correlated to TC content of sediments and temperature and negatively to distance from shore. The annual mean concentration ranged among 10 and 51 μg S2‐/1 and was not affected by wave breakers.
Oxygen consumption of a Chaoborus species from a neotropical reservoir (socuy reservoir, Venezuela)
Authors: Corona Alnair , López Carlos
Published: February 2007

Oxygen consumption of all four larval instars of a Chaoborus species from Socuy Reservoir in western Venezuela was studied under laboratory conditions at 25°C. On a logarithmic basis, oxygen consumption per organism increased as a smooth, linear function of body weight (0.49 power of body weight). Observed rates were lower than other Chaoborus species with comparable body weight at the same temperature. Oxygen consumption per unit weight decreased from smaller to large instar larvae. With the exception of instar I, values of oxygen consumption per unit weight were lower than values reported for other Chaoborus species. The results suggest that our species have low energy demands for maintenance, and are consistent with suggestions about high efficiency in use of energy in genus Chaoborus.
Patterns of benthic fauna and benthic respiration on the celtic continental margin in relation to the distribution of phytodetritus
Authors: Duineveld G. C. A. , Lavaleye M. S. S. , Berghuis E. M. , de Wilde P. A. W. J. , van der Weele J. , Kok A. , Batten S. D. , de Leeuw J. W.
Published: February 2007

In‐situ and shipboard measurements of sediment community oxygen consumption (SCOC), in conjunction with a study of the distributions of macro and megafauna and phytopigments, were used to determine and, where possible, explain the distribution of labile particulate organic matter (POM) on the NE Atlantic continental slope (Goban Spur, SW Ireland). A specific issue concerned the existence of depocentres of labile POM on the slope caused by lateral transport, a phenomenon that has been found previously in the NW Atlantic. The SCOC data from October 1993 and May 1994 showed a steady decrease with increasing water depth. SCOC values ranged from 5.4 mmol m−2 d−1 at the shelfbreak to 0.3 mmol m−2 d−1 at 4,500 m depth. No evidence was found for seasonal variation in SCOC. A clear seasonal signal was observed with regard to sediment phytopigments and phytopigment fluxes into sediment traps attached to the benthic lander. The upper‐ and mid‐slope values of both parameters were much higher in May 1994 than in October 1993 and August 1995. This is consistent with the normal spring bloom pattern; but because of the degraded state of the May phytodetritus in the near‐bottom water, reflected in the lack of a response in SCOC and the low chlorophyll‐a concentrations, it was concluded that the material was not derived from the overlying photic zone, but instead transported from elsewhere in the benthic nepheloid layer (BNL). In August 1995, the lower slope (>3,000 m) had received a strong and fresh phytodetritus pulse (3 g C m−2) forming a mucous layer on top of the sediment. Using phytopigments and sterols as molecular markers, it was shown that the pulse was derived from an offshore bloom with an important contribution by dinoflagellates. By contrast, no mucous layer was found on the upper slope stations in August 1995. Macrofauna biomass showed a distinct decline from the upper slope down to the lower slope conforming to the diminishing supply of labile POM. The total wet biomass of megafauna reached relatively high values at the lower slope (>3,500 m) owing to large motile sea cucumbers. The presence of these “vacuum‐cleaner” sea cucumbers is considered indicative of the occurrence of phytodetritus pulses. In spite of their assumed adaptation to periodic pulses, the estimated contribution by the sea cucumbers to the total benthic mineralization is minor. When combining data from different years/seasons we observed decoupling between the food supply to the lower slope and the upper and mid slopes. The major pulse to the former comes from an offshore summer bloom. The upper and mid slope appear to be fuelled by spring bloom material which is subsequently redistributed on the upper slope in a BNL. The quality of the seston in the BNL diminished in the offshore direction as indicated by the phytopigment concentrations.
Freshwater oligochaeta of some urban watercourses in the Russian far east
Authors: Timm Tarmo
Published: February 2007

40 oligochaete species are identified in the lowland watercourses near Ussurijsk and Vladivostok. In the Razdol'naja River, Naididae are common, increasing in numbers in enriched urban stretches where tubificids become abundant, including Limnodrilus hoffmeisteri Claparède and Tubifex tubifex (Müller). A freshwater population of Monopylephorus rubroniveus Levinsen exists there. The endemics of the Amur zoogeographical Province, Haber amurensis (Sokol'skaja et Hrabê) and Piguetiella amurensis Sokol'skaja, are redescribed. Stylaria fossularis Leidy is a valid species. Rhyacodrilus coccineus (Vejdovsky) and its East Asian congeners form a closely related species complex. A new generic name is proposed instead Muliercula (Timm). According its oligochaete fauna, the Amur‐Japanese freshwater zoogeographical Subregion is closer to the Holarctic than to the Sino‐Indian Region.
Physico‐chemical and biological dynamics of a sewage‐polluted limestone aquifer
Authors: Malard Florian , Reygrobellet Jean‐Louis , Winiarski Thierry
Published: February 2007

The spatio‐temporal pattern of groundwater contamination at a 500 m2 fractured limestone site polluted with sewage effluent was investigated over two years. In the context of a previously defined conceptual groundwater flow model, a multidisciplinary approach involving the collection of physico‐chemical, bacteriological and biological (macro‐ and meiofauna) data was developed. Results showed that much of the sewage‐polluted water infiltrated rapidly through some large subvertical fractures at the site and circulated with little or no contaminant attenuation through the solution‐enlarged parts of a bedding joint. In such preferential contaminant paths, groundwater had low physico‐chemical and bacteriological “stability”, highest average contaminant concentrations, and a high epigean organism component. Observation of the spatial distribution of organisms a short period after flooding also suggested that contaminants circulating through these conductive fractures entered the adjacent small‐sized fissure matrix of the saturated zone. In this small aperture region of the site that was recharged by slow infiltrations of sewage‐polluted surface water, groundwater had a greater physico‐chemical and bacteriological “stability”, lowest average contaminant concentrations, and a high hypogean organism component. This lower sensitivity to surface pollution was partly due to attenuation processes such as retention of fecal indicator bacteria or nitrification of effluent ammonium which occurred in slow‐moving water parts of the unsaturated zone.
The effects of a change in withdrawal operations on phytoplankton and nutrient dynamics in eau galle reservoir, Wisconsin (USA)
Authors: Barbiero Richard P. , James William F. , Barko John W.
Published: February 2007

Selective withdrawal through the surface outlet was employed in Eau Galle Reservoir to reduce phytoplankton populations by 1) strengthening thermal stability, thereby decreasing vertical entrainment of hypolimnetic phosphorus (P); and 2) increasing epilimnetic flushing rate and discharge of algae. In spite of substantial release of sediment P over the growing season, epilimnentic P concentrations were overwhelming dominated by external sources, and thus insensitive to changes in withdrawal depth. Nor did surface withdrawal increase flushing rate sufficiently to affect phytoplankton biomass. In one year, an increase in thermal stability, due in part to surface withdrawal, permitted the development of a metalimnetic chlorophyll maximum in a summer that also experienced relatively low populations of ‘nuisance’ cyanophytes, and can be regarded as a positive effect of the change in operations.
Effects of food limitation, notonectid predation, and temperature on the population dynamics of Daphnia carinata
Authors: Barry Michael J.
Published: February 2007

The relative contributions of invertebrate predation (Notonectidae: Anisops spp.), food limitation, and certain abiotic factors in driving the population dynamics of Daphnia carinata were studied for a two year period in a large farm dam in southern Victoria, Australia. Detailed measurements were made on the population densities of Daphnia and Anisops spp., the amount of food available, the nutritional status, and the size‐specific fecundity of Daphnia.

The density of the Daphnia population at the field site oscillated closely with water temperature. The amplitude of the population fluctuations varied seasonally, being much greater during the warmer months of the year and switching to fluctuations with low peaks when water temperature dropped below approximately 15°C. Anisops spp. densities were greatest in winter and declined during the spring of each year. Nymphs appeared in late spring and early summer and numerically dominated the population. During the warmer periods of the year, the daphnid population went through a series of rapid growth phases leading to over‐exploitation of food resources and subsequent population collapses. Daphnia population densities were not correlated with Anisops numbers suggesting that predation was not a major regulatory factor during the warmer periods of the year. When water temperatures fell below ca. 15°C daphnid population densities remained low despite high food levels. During this period the impact of Anisops may have been greater. Two distinct phases were identified: a warm water period when food limitation was the main regulatory factor, and a cool water period when Anisops predation may have been the paramount factor. Low oxygen concentrations were associated with heavy rainfall in the spring and may have had a limiting effect on Daphnia for short periods. Daphnia may have had an important role in sustaining the Anisops population in the pond over each winter.
The Influence of Extremely High Concentrations of Inorganic P at Varying pH on the Growth and Photosynthesis of Unicellular Algae
Authors: Nielsen E. Steemann , Rochon T.
Published: February 2007

An increase in the phosphate concentration due to severe pollution is without real toxic effect for the phytoplankton in eutrophic lakes, although the various species have a variable tolerance against high concentrations. Experiments on photosynthesis and growth were made with cultures of two algae, Chlorella pyrenoidosa and Nitzcshia palea, using phosphate concentrations much higher than ever found in nature. The tolerance decreases with rising pH. This seems not to be due to a higher ratio of secondary phosphate at a high pH. Nor is the rise in the osmotic pressure apparently the cause of the decrease in the growth rate at high phosphate concentrations.
The Vertical Distribution Patterns of Heterotrophic Bacteria in the Depths of the World Ocean and the Importance of their Regularity to Oceanography
Authors: Kriss A. E.
Published: February 2007

Many years' research into the concentration of unstable organic matter in ocean waters from many regions of the World Ocean is compiled. The relative amounts of this matter, as determined by counts of heterotrophic bacteria, are presented as three‐dimensional illustrations, depicting specific ocean areas from the surface to the sea floor. The merits of using this information in oceanography are discussed, particularly in cases where other parameters are indistinct. In many cases, this is viewed as the best method for determining the origin of water layers at various depths, and of following the movement of water masses in the ocean.
Beiträge zur Ökologie der benthischen Algen des Hochgebirges in den Pyrenäen II. Cyanophyceen und übrige Algengruppen
Authors: Backhaus Diedrich
Published: February 2007

Little research has been made on the litoral algal flora of unpolluted high mountain lakes and streams. Since the algal flora is often used to estimate the water quality, it is of great value to know more about the ecology of benthic forms living under extreme oligotrophic conditions.

An investigation was made of the benthic and littoral microphytic vegetation of Esteragne torrent, and Lac de Port‐Bielh in the High Pyrenees. Both waters combine a low calcium content with a consistently basic pH. A comparison of their flora with that of other lakes may help to deal with the problem of whether the algal flora is determined more by the calcium content or the pH.

The algal flora of Esteragne torrent differs little from that of low‐calcium streams of the central European highlands. In Lac de Porth‐Bielh there is a distinct depth‐zonation among the dominant algae. The dominant taxa at a depth of 0–0,5 metres are: Schizothrix lacustris f. lutescens, Sch. calcicola, Gloeocapsa tornensis, Pleurocapsa minor with Cyanostylon microcystoides and Hydrococcus cesatii particularly on the undersides of the stones; from 0,5 to 1,5 m: a massive growth of Nostoc zetterstedtii; from 2,5 to 4,5 m: Schizothrix funalis; from 7 m: Nitella flexilis. In addition the lake includes a number of rare and little known forms such as? Onkonema sp., of. Desmosiphon maculans, Lyngbya lachneri, Homeothrix sinensis, Chantransia chalybea v. profunda, Siphononema polonicum status chamaesiphonoides. Green algae were almost completely absent from the upper zones, in contrast to the usual findings. The littoral flora has a very distinctive character, and is not directly comparable with that usually found in lakes with either high or low calcium content. A certain resemblance to lakes with a high calcium content can be found only if all the forms present particularly with lower abundances are considered. The very strong development of lithophytes should be emphasized in contrast to their usually low density in lakes with low calcium content.

The systematic section deals with systematic and taxonomic problems in a number of difficult forms.
Mathematisches Modell zur Deutung der durch intermittierende Belichtung von Phytoplanktern hervorgerufenen Mehrleistung der Photosynthese
Authors: Baumert Helmut
Published: February 2007

In the turbulent, turbid water body of a river, lake, reservoir or ocean, the light intensity for a phytoplankton individuum is time‐dependent. But current production equations are based on time‐independent light conditions. A mathematical model for the photosynthetic oxygen production under the simple condition of intermittent light is developed. It consists of one nonlinear algebraic and one linear differential equation of the first order. For the photosynthetic apparatus a global effective relaxation time τ is given. The model is proved with the data published by Warburg (1919). It shows, coupled with an empirical relation for τ, a good qualitative and quantitative agreement with experimental results.
Oxygen Deficits, Clarity, and Eutrophication in some Madison Lakes
Authors: Stewart Kenton M.
Published: February 2007

Oxygen deficits, rates of oxygen depletion, and Secchi disk measurements were the major indices examined in this study to determine trends in trophic conditions in Lakes Mendota, Monona, and Waubesa near Madison, Wisconsin. On the basis of available data, there is little that can be said reliably with respect to documenting eutrophication, particularly in Lake Mendota in the past several decades, that could not be attributed to normal variability. Better evidence for eutrophication comes from cores of some of the lakes.

A comparison of oxygen deficits without simultaneous information on mean hypolimnetic temperatures and the lateness of ice out may provide a misleading interpretation of trophic variations over time.
Zur Bildung mathematischer Modelle limnischer Ökosysteme mittels rekursiver Schätzverfahren. Mathematical Modeling of Limnic Ecosystems with Recursive Estimation Methods
Authors: Gnauck Albrecht , Wernstedt Jürgen , Winkler Winfried
Published: February 2007

In the past many authors have described mathematical models of limnic ecosystems by means of differential equations and time‐stationary statistical methods. But an accurate description of the ecosystem processes is only possible by time‐varying methods. Approaching deterministic techniques often leads to hardly computable nonlinear differential equations with distributed parameters.

In this paper recursive estimation methods of ecosystems modeling in real‐time are presented and first results of the application to Saidenbach reservoir are given. In practice the oxygen balance of the surface and of two lower layers (depth 10 m and 35 m) of the reservoir was modeled. The structure of all models was p‐canonic with oxygen as output and temperature, oxygen deficiency (BOD2), seston, chlorophyll, nitrate‐nitrogen, COD(Mn), phosphate (PO4) as inputs on each level. For surface model the Secchi disk‐transparency was used as an additional input.
Abschätzung von Turbulenzkorrekturen für die phytoplanktische O2‐Produktion bei schwacher Turbulenz. Estimation of Turbulence Correction Terms for the Phytoplankton Production (O2) Under Conditions of Low Turbulence
Authors: Baumert Helmut
Published: February 2007

The turbulence correction terms for the photosynthetic oxygen production of phytoplankton given by BAUMERT (1974) are used for the case that the variations in velocity are exponentially autocorrelated. In case of the P(I)‐relation by STEEMANN NIELSEN one can show that the value of the relative correction term is — in the worst case — less than, or equal to 1% if the depth of epilimnion (mixing depth) and the light intensity at the water surface are high.

The demand for weak turbulence and light extinction — necessary for validity of the equations — is met for some real objects, especially for oligotrophic seas and lakes.
Assimilation de glucose dans la zone de divergence de Méditerranée Nord‐occidentale. Glucose Uptake in the North Western Mediterranean Divergence Zone
Authors: Cahet Guy , Jacques Guy
Published: February 2007

Conditions governing the utilization of glucose by the pelagic communities of the Northwest Mediterranean have been studied and it is concluded that (1) the vertical distribution of heterotrophic activity first reaches a maximum at about 50 m, close to the maximum of the phytoplankton while a second maximum occurs at 150 m; furthermore, within the first 200 m, the mineralization of carbon is almost complete and (2) the response of the microorganisms to increasing amounts of substrate follows the kinetic law of MICHAELIS‐MENTEN.
The Relation Between Adenosine Triphosphate and Microbial Biomass in Diverse Aquatic Ecosystems
Authors: Paerl Hans W. , Williams Noel J.
Published: February 2007

By using autoradiographic examination of 14C labeled viable cells, natural phytoplankton communities were separated into living and non‐living components. Comparisons of carbon to adenosine triphosphate (ATP) content of living cells yielded consistent ratios with depth, during periods of high and low nutrient supply at Lake Tahoe. Over time the ratio fluctuated by no more than ± 17% of the mean between the time of maximum nutrient supplies and nutrient depletion. The viability of specific phytoplankton groups was surprisingly low at times, indicating that conventional counting methods tend to overestimate live biomass. A survey of lakes differing in trophic states and having diverse phytoplankton and bacterial assemblages has shown that ATP measurements can be used as an accurate measure of total living microbial biomass.
An Improved Reineck Box for Sampling Coarse Sand
Authors: Farris Richard A. , Crezée M.
Published: February 2007

A Reineck Box core sampler has been modified for quantitative use in the marine benthos. The modifications are inexpensive and easily accomplished in any machine shop. Samples have been successfully taken in medium coarse to fine sands for layer by layer analysis. The apparatus has a high degree of efficiency, takes a large volume of sediment, and produces an undisturbed core.
Study of Domestic Sewage Waste Treatment by the Polychaetes, Neanthes japonica and Perinereis nuntia var. vallata, on an Artificial Tidal Flat
Authors: Kurihara Yasushi
Published: February 2007

In order to establish a new biological method of treating sewage waste, mass cultures of the polychaete annelids, Neanthes japonica and Perinereis nuntia var. vallata, were employed. These species are known to ingest a large quantity of sewage sludge extracted from domestic sewage treatment plants. During this study, laboratory experiments were carried out to determine the effects of changes in various environmental factors on sludge consumption and growth. A pilot plant with an artificial tidal flat simulating natural estuarine tidal flat conditions was constructed and operated as a habitat for the polychaetes. The suitability of this artificial tidal flat for the treatment of sewage waste was discussed.
Theory of the Upper Limit to Phytoplankton Production per Unit Area in Natural Waters
Authors: Baumert Helmut , Uhlmann Dietrich
Published: February 2007

Using the maximum quantum yield of photosynthesis, the maximum daily integral of photosynthetically active radiation (PAR) and the euphotic zone depth as a basis, general formulae for the upper limits to gross and net carbon fixation in natural waters are derived by theoretical considerations. The results are compared with a set of extremely high production data published by independently working authors, including data from algal mass cultures, oxidation ponds, freshwater and salt lakes, reservoirs, rivers and canals, coastal and other marine waters, including upwelling areas. The comparison reveals a quite surprising degree of agreement and suggests that the derived formulae represent a new, theoretically sound general approach to phytoplankton production. In particular, it can be shown that the upper limit to phytoplankton production in natural waters is about three times higher than earlier estimates in the literature. The maximum energy efficiency is of the same order of magnitude as in terrestrial plant communities.
Size Structure of Deep‐Sea Meio‐ and Macrobenthos in the Western Pacific
Authors: Shirayama Yoshihisa
Published: February 2007

The size structure of deep‐sea meio‐ and macrobenthos was studied using 12 USNEL box corer samples collected in the Western Pacific. Both macro‐ and meiobenthos decreased in abundance with increasing water depth, as expected, but contrary to previous findings, the rate of decrease did not differ significantly between the two size classes of organisms. The median size index of total meiobenthos decreased with increasing water depth, while when the vertical distribution of organisms in the sediment was considered, such a trend was restricted to the organisms found in the upper 1 cm layer. In contrast, the median size of the nematodes increased with increasing water depth, and a possible cause for this correlation is discussed.
On the Occurrence of “Arctic” Cladocera with Special Reference to those along the Strait of Belle Isle (Quebec, Labrador, Newfoundland)
Authors: Meijering Meertinus P. D.
Published: February 2007

In September, 1978, ten ponds inhabited by Cladocera were sampled along the coasts of the Strait of Belle Isle. Fourteen out of nineteen species that were found there also occur in Greenland. On the other hand, a comparison with faunal lists for the island of Newfoundland and several faunal regions of Western Europe, and the ecological distribution of all European Cladocera reveals that the Arctic is settled exclusively by euryecious species, so that the relatively strong “arctic” element within the cladoceran fauna along the Strait of Belle Isle indicates simply the extreme conditions. Macrothrix hirsuticornis NORMAN & BRADY and Daphnia pulex LEYDIG are new for the island of Newfoundland.
Skeletal morphology and postmetamorphic ontogeny of Acris crepitans (Anura: Hylidae): A case of miniaturization in frogs
Authors: Maglia Anne M. , Pugener L. Analía , Mueller Jessica M.
Published: February 2007

Acris crepitans is a small, semiaquatic member of the treefrog family Hylidae. Much recent attention has been paid to this species because of reports of population declines and malformations, yet few works have considered the skeletal anatomy of this common North American frog. Herein, we provide a detailed description of the morphology and adult ontogeny of the skeleton of A. crepitans, and discuss novel morphologies, interesting postmetamorphic developmental patterns, and intraspecific skeletal variation. The reduced amount of adult ossification, as well as several novel morphologies present in this species, are consistent with patterns of miniaturization seen in other anurans. For example, the skull is poorly ossified, but most of the cranial cartilages are heavily mineralized, the nasal bones are fused to endochondral ossification of the tectum nasi, the palatines are reduced, and the prootics and exoccipitals are not fused to one another (although the prootics are well‐developed and ornamented). In addition, several specimens exhibit abnormalities, which might indicate that: (1) the population was under an acute malformation outbreak, (2) a high incidence of small skeletal malformations is normal in this species, (3) the population is under stress because of habitat fragmentation, (4) there is environmental deterioration in the region where the specimens were collected, and/or (5) the species is now showing signs of decline in southern Missouri. Regardless of the cause, it is clear that further examination of skeletal variability in A. crepitans, including ossification patterns and the frequency of abnormalities, is warranted. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Explanation and policy in land degradation and rehabilitation for developing countries
Authors: Blaikie Piers
Published: February 2007

The paper examines why land management practices are not carried out, and what can be done about this. It focuses on the need to obtain an accurate explanation of why degradation has occurred, and highlights the need to examine: whether degradation really is taking place; the identification of those for whom land degradation is, or will be, a problem; the identification of why land degradation is taking place; the need to find solutions and means to reach them (i.e. policy formulation).
Soil degradation: I. Basic processes
Authors: Lal R. , Hall G. F. , Miller F. P.
Published: February 2007

This paper examines soil and land degradation. It describes basic processes and factors responsible for degradation, illustrates the cause‐effect relationships and differentiates between natural and man‐induced regressive effects. The ‘critical limit’ concept is described in terms of properties beyond which the soil will not support an economically‐viable agriculture. This paper is not an exhaustive literature review but emphasizes the scientific principles involved and highlights natural against man‐induced processes. Important natural processes are: laterization, hard‐setting, fragipan and clay pan formation, and geologic erosion. In comparison, man‐induced processes consist of: soil compaction, accelerated erosion, desertification, salt accumulation and leaching and acidification. One of the principal constraints is the problem of data reliability. A reliable database and precise criteria are definitely lacking and hinder the assessment of the extent, type and degree of soil degradation and establishing the cause‐effect scenario. Improving our database is, therefore, of a high priority if we are to adopt land use policy for sustainable soil management and long‐range resource management. Also outlined, are vital research and development strategies. Judicious resource management policy should emphasize managing prime agricultural land to produce to its maximum potential so that there is no need to cultivate marginal and easily‐degraded fragile ecosystems. A strict code of conduct is needed for utilizing marginal/fragile lands. Methods of restoring the productivity of degraded lands must be researched so as to minimize the need to clear and develop new lands.