Calcite covering of sediment as a possible way of curbing blue-green algae

Natural calcite precipitation in lakes is a well-known control mechanism of eutrophication. In hard-water lakes, calcite deposits on the flat bottoms of shallow lakes and near the shores of deeper lakes resulted from biogenic decalcification during the millenia after the last glacial period. The objective of a new restoration technology is to intensify the natural process of precipitation by utilizing the different qualities of calcareous mud layers. In a pilot experiment in Lake Rudower See, East Germany, phosphorus-poor deeper layers of the sediments were flushed out and spread over the phosphorus-rich uppermost sediments, to promote the co- precipitation of calcite with phosphorus from the water-column.

Development of trophic state and phytoplankton in an oligo-mesotrophic reservoir (Kleine Kinzig) in Black Forest, Germany

Since 1989, intensive studies have been made on a relatively new (1983-84) oligotrophic reservoir and its pre-reservoir in the Black Forest. This paper briefly reports on the hydrochemistry, especially annual variations in phosphorus loadings, and the seasonal development of phytoplankton in 1989 and 1990.

Changes of water quality and sediment phosphorus of a small productive lake following decreased phosphorus loading

Esthwaite Water is the most productive or eutrophic lake in the English Lake District. Since 1945 its water quality has been determined from weekly or biweekly measurements of temperature, oxygen, plant nutrients and phytoplankton abundance. The lake receives phosphorus from its largely lowland-pasture catchment, sewage effluent from the villages of Hawkshead and Near Sawrey, and from a cage-culture fish farm. From 1986 phosphorus has been removed from the sewage effluent of Hawkshead which was considered to contribute between 47% and 67% of the total phosphorus loading to the lake. At the commencement of phosphorus removal regular measurements of phosphorus in the superficial 0-4 cm layer of lake sediment were made from cores collected at random sites. Since 1986 the mean annual concentration of alkali-extractable sediment phosphorus has decreased by 23%. This change is not significant at the 5% level but nearly so. There has been no marked change in water quality over this period. Summer dominance of blue-green algae which arose in the early 1980s after decline of the previous summer forms, Ceratium spp., has been maintained. Improvement in water quality is unlikely to be achieved at the present phosphorus loading.

Eutrophication in the River Meuse

The severe problems caused by large phytoplankton populations in the River Meuse date back to the beginning of the 1980s. However, no clear relationship can be established between an increase of algal growth and dissolved nutrient concentrations, at least in the Belgian part of the river. Most probably, plankton algae start developing in France, utilizing large inputs of phosphorus from some of the tributaries: this point will be investigated further, as well as the effect of a reduction in the releases of phosphorus. A mathematical model helps to understand the main factors which control algal growth: underwater light, temperature, discharge and grazing by zooplankton. The last is a major loss process in summer and, as shown by recent observations, may trigger a seasonal succession leading to dominance by large phytoplankton taxa. With regard to water quality, eutrophication is a major problem in drinking-water treatment (filter clogging, etc.) and large numbers of decomposing algae may adversely affect the oxygen budget of the river. On the other hand, algal photosynthesis is the most important oxygen source at periods of low discharge, and reduced algal production may result in dramatic oxygen decreases in heavily polluted stretches of the river.

Physical measures to inhibit planktonic cyanobacteriae

In a small lake, intermittent destratification was installed after several other physico-chemical and physical in-lake therapy measures (phosphorus immobilization, permanent destratification) had been tested without great success. If an aerobic sediment-water interface can be maintained, intermittent destratification removes cyanobacteria and prevents optimal development of other members of the photoautotrophic plankton. During growing seasons, increasing abundances of small-bodied herbivores (Bosmina) and Daphnia may have accounted for relatively low phytoplankton biomass as well. Intermittent destratification is a very fast-working in-lake measure and seems to be applicable even in relatively shallow lakes (< 15 m), in which permanent destratification seems to be risky.

Active reservoir management: a model solution

Steady-state procedures, of their very nature, cannot deal with dynamic situations. Statistical models require extensive calibration, and predictions often have to be made for environmental conditions which are often outside the original calibration conditions. In addition, the calibration requirement makes them difficult to transfer to other lakes. To date, no computer programs have been developed which will successfully predict changes in species of algae. The obvious solution to these limitations is to apply our limnological knowledge to the problem and develop functional models, so reducing the requirement for such rigorous calibration. Reynolds has proposed a model, based on fundamental principles of algal response to environmental events, which has successfully recreated the maximum observed biomass, the timing of events and a fair simulation of the species succession in several lakes. A forerunner of this model was developed jointly with Welsh Water under contract to Messrs. Wallace Evans and Partners, for use in the Cardiff Bay Barrage study. In this paper the authors test a much developed form of this original model against a more complex data-set and, using a simple example, show how it can be applied as an aid in the choice of management strategy for the reduction of problems caused by eutrophication. Some further developments of the model are indicated.

Management of Biesboch reservoirs for quality control with special reference to eutrophication

The three Biesbosch Reservoirs are pumped storage reservoirs, fed with rather polluted and highly eutrophic water from the River Meuse. Air injection at the bottom of the reservoirs prevents thermal stratification, which would otherwise result in serious water quality deterioration. Reservoir mixing also serves as an economic algal control measure; mixing over sufficient depth causes light to play the role of limiting factor and this, combined with zooplankton grazing, keeps the biomass of phytoplankton at acceptable levels. Special problems are caused by benthic, geosmin-producing Oscillatoria species growing on the inner embankment. Rooting up the bottom with a harrow is used as the method of control, based on underwater observations by biological staff trained as SCUBA-divers. With regard to pollutant behaviour the three reservoirs act as a series of fully mixed reactors. This enables the application of kinetic models to describe their behaviour and allows the use of a selective intake policy, e.g. for suspended solids with associated contaminants, ammonia and polynuclear aromatic hydrocarbons. A combination of selective intake and self- purification processes - enhanced by the compartmentalisation of the storage volume in three reservoirs - leads to a striking improvement for many water-quality parameters.

Summary and concluding remarks

This chapter summarises the meeting, entitled ���Eutrophication: Research and Application to Water Supply���. The general feeling was that academic research on the process of eutrophication had progressed significantly over the past decade, but there had been little contact with the water managers, i.e. those whose work was at the sharp end of dealing with the associated problems. This chapter summarises the sessions held by experts in the field.

Structural dynamic eutrophication models

This article discusses problems of modelling the seasonal succession of algal species in lakes and reservoirs, and the adaptive selection of certain groups of algae in response to changes in the inputs and relative concentrations of nutrients and other environmental variables. A new generation of quantitative models is being developed which attempts to translate some important biological properties of species (survival, variation, inheritance, reproductive rates and population growth) into predictions about the survival of the fittest, where ���fitness��� is measured or estimated in thermodynamic terms. The concept of ���exergy��� and its calculation is explored to examine maximal exergy as a measure of fitness in ecosystems, and its use for calculating changes in species composition by means of structural dynamic models. These models accomodate short-term changes in parameters that affect the adaptive responses (species selection) of algae.

A tool for better management of water quality during periods of algal blooms: the case of the River Oise

Like other rivers in the Paris area, the Oise is subject to important seasonal algal blooms. This eutrophication generates notable problems for the production of drinking-water from a treatment plant on the river at M��ry. A mathematical model has been developed to simulate variation in water quality in a pre-treatment storage basin, and another model is currently being adapted to model the River Oise. Integration of the two models should provide a comprehensive tool for predicting variations of phytoplankton and water-quality parameters associated with algal blooms. This will be a decision-aid for optimizing control of the treatment process for providing potable water.

A control of gas-vacuolate cyanobacteria

The cyanobacteria that cause problems in water supply are principally the colonial forms that are buoyed up by gas vesicles. The success of these organisms is due, in part, to their gas vesicles, which enable them to perform vertical migrations or to maintain themselves in the euphotic zone. The gas vesicles are also the root cause of the problems. In calm periods they cause the cyanobacteria to float to the water surface forming noxious scums, and they may prevent the colonies from sedimenting in water treatment plants. Gas vesicles are hollow, gas-filled structures; they are rigid but can be collapsed by the application of pressure. Their critical collapse pressure is influenced by their dimensions, which vary in different organisms. Gas vesicles are formed by the assembly of two types of protein, which determine their mechanical and physical properties. Methods for collapsing gas vesicles in natural populations of cyanobacteria will be considered. They may have application to the control of cyanobacteria in water supply.

The microbiological quality of water: the nature of the problem

Improvements in methods for the detection and enumeration of microbes in water, particularly the application of techniques of molecular biology, have highlighted shortcomings in the ���standard methods��� for assessing water quality. Higher expectations from the consumer and increased publicity associated with pollution incidents can lead to an uncoupling of the cycle which links methodological development with standard-setting and legislation. The new methodology has also highlighted problems within the water cycle, related to the introduction, growth and metabolism of microbes. A greater understanding of the true diversity of the microbial community and the ability to transmit genetic information within aquatic systems ensures that the subject of this symposium and volume provides an ideal forum to discuss the problems encountered by both researcher and practitioner.

Kazetaritza euskaraz. Oraina eta geroa

Txikiegia, agian. Euskarazko Kazetaritzaren mundua oraindik ere txikiegia izan daiteke, bai behintzat inguruan dituen erdarazko kazetaritzekin alderatuz gero: ur tanta apala ozeanoaren erdian, kimu txiker la��oa basoaren handitasunean. Handiak zeharka begiratu izan dio beti txikiari, eta txikiak, inbidiaz, handiari. Txikitasunetik datozkio arazo gehien Euskarazko Kazetaritzari. Hala ere, bere txikitasunean handia da, eta maitagarria. Unibertso zabala biltzeko gai izan da, itsasoak eskaintzen duen kolore-aniztasunaren pareko, basoak opa digun joritasunaren kideko. Itsasoan eta basoan, ordea, den-dena ez da eder eta kolore bizi. Batean zein bestean, alde ilun eta ezezagun ugari daude, baita mehatxu franko ere. Esku artean duzun liburua dibertsitate horren isla da, lagun. Horixe du helburu, behintzat. Alde horretatik, oso pozgarria da ondorengo orrialdeetan bildu diren adituen ekarpenen maila zein jasoa den egiaztatzea. Euskarazko Kazetaritzaren inguruan ez da inoiz horrenbeste gogoetarik egin, ezta ere horrenbeste iritzi eta azterketarik bildu testu bakar batean. Mundu hau dezente aldatu dela azken hamarkadetan. Duela hogeita hamar bat urte, esaterako, Euskal Herrian oso gutxi ziren euskaraz jarduten zuten profesionalak. Orduko kazetari euskaldunek oso aukera gutxi zeuzkaten: Herria, Zeruko Argia, Anaitasuna, Goiz Argi, Herri Irratiak��� eta ezer gutxi gehiago. Gaur egun, ordea, Euskarazko Kazetaritza Euskal Herri osoan presentzia duen errealitatea da: 700 profesional inguru eta 250etik gora hedabide dira horren lekuko. Baditugu Euskal Herri osoan eta euskaraz diharduten egunkari, atari elektroniko, astekari, irrati eta telebistak. Horretaz gain, badugu, herriz herri, eta sektorez sektore, osatzen joan den hedabide txiki berri eta ertainen sare zabala: zortzi herri telebista, 30 irrati, 60 herri aldizkari, 61 aldizkari espezializatu, 60 berripaper, 34 eskoletako argitalpen eta hamarnaka hedabide elektroniko. Hori guztia 779.788 hiztun dituen komunitate batean. Bistan denez, Euskarazko Kazetaritza izugarri hazi da, oso handia baita mundu honek berezkoa duen indar-sortzailea. Errealitate hori makina bat pertsona, elkarte, gizarte-mugimendu eta erakunderen ahalegin eta elkarlanaren ondorioa izan da. Orobat, hazkunde ikaragarri horrek agerian utzi ditu sektorean dauden hainbat ahulezia: egoera soziolinguistikoa, merkatu txikiak, lan-baldintza makurrak eta dirulaguntza-politika definitu gabeak, besteak beste. Euskarazko Kazetaritza beregaintasuna lortzetik urrun da, oraindik ere. Horretaz guztiaz hitz egiten da liburu honetan. Hemen Euskarazko Kazetaritzaren baitan edo inguruan dabiltzan 50 inguru profesional eta adituk hartu dute hitza beren ikuspuntua plazaratzeko, beren ikerketak azaltzeko, beren kezkak agertzeko eta, etorkizunari begira, planteatzen diren erronkez beren gogoetak egiteko. Iraganari erreparatu zaio, baina indar gehien orainean eta geroan jarri nahi izan dugu. Ondorengo orriotan Euskarazko Kazetaritzaren diagnostikoa egiten da, testu zientifiko batek exijitzen dituen zehaztasun eta zintzotasunez. Lehen atala Euskarazko Komunikazioaren Esparrua definitzeari eskaini diogu, oso garrantzitsua baita zer garen edota zer ez garen hasiera-hasieratik jakitea. Baina ez gaude soilik geure zilborrari begira egoteko. Horregatik txertatu ditugu hemen George Jones galestarrak, G��nther Rautz tiroldarrak eta Logi Bergmann Ei��sson islandiarrak ekarri dizkiguten ikuspuntuak eta esperientzia aberasgarriak. Bigarren atala -���Euskarazko hedabideak��� izenekoa- da gizenena. Euskaraz diharduten hedabide garrantzitsuenek dute hemen beren esperientziak eta erronkak plazaratzeko agertokia, baita Internet bidez zabaltzen direnek ere. Berton euskarazko publizitatearen inguruan dauden gabeziez ere egiten da gogoeta. ���Bideak eraikitzeko ahaleginean��� da hirugarren atalari eman zaion izenburu nagusia. Euskarazko Kazetaritza gaur egun errealitate emankorra bada, neurri handi batean berton diharduten eragileek historikoki elkarlanerako erakutsi duten prestutasun nabarmenari esker izan da. Gizarte-eragile esanguratsuek hartu dute hitza beren ikuspuntuak eta premiak agertzeko, beren kezkak gizarteratzeko. Guztion ahotan gogoeta bera: sinergiak sustatu eta baliabideen erabilera optimizatu egin behar dira. Laugarren atala etorkizunari begira jarri dugu, handiak baitira ate joka ditugun erronka eta jomugak; ez soilik teknologia berriei begira, baita hizkuntza eta kazetari euskaldunon lan-baldintza hobetzeari erreparatuta ere. Azken atalean ondorio nagusiak bildu ditugu. Gure uste apalean, liburu honetatik atera daitezkeen gogoetarik funtsezkoenak dira. Behar-beharrezkoa da horiei arretaz erreparatzea, Euskarazko Kazetaritzak aurrera egin nahi badu behintzat. Mardula da, zalantzarik gabe, esku artean duzun liburua. Hasieran azpimarratu ditugun aniztasuna eta joritasuna islatu nahi izan ditugu hemen. Euskarazko Kazetaritzare