Louis Van Liere

Growth Kinetics of Oscillatoria agardhii Gomont in Continuous Culture, Limited in its Growth by the Light Energy Supply

Summary: Growth efficiency (c) and specific maintenance rate constant (μe) were determined in continuous cultures of the cyanobacterium Oscillatoria agardhii Gomont, in light energy-limiting conditions, according to the formula μ = cq E – μe in which q E is the specific light energy uptake rate. Values of the efficiency factor c varied with irradiance from 0.23 at 0.5 W m−2 to 0.05 at 40 W m−2. The specific maintenance rate constant was 0.001 h−1. The culture pH value influenced c and μe . A diurnal light/dark cycle with a 16 h photoperiod did not affect either of the two parameters, μe and c. The relationship between growth rate and light energy uptake rate, embodied in the above formula, was also valid for nitrogen (nitrate)-limited cultures.

Occurrence of Oscillatoria Agardhii and Some Related Species, a Survey

Oscillatoria agardhii is often found in intermediate water layers in stratified lakes, but also in shallow eutrophic lakes. The conditions prevailing in several of these lakes are compared in order to determine which factors are of importance with respect to the dominance of Oscillatoria agardhii. These data, taken from the literature, are also compared with our findings with laboratory cultures of this organism.

Growth and physiology of Oscillatoria agardhii gomont cultivated in continuous culture with a light-dark cycle

The cyanobacterium Oscillatoria agardhii Gomont was cultivated with a diurnal light-dark cycle (photoperiod 16 h) in continuous culture. There were found to be large differences in specific synthesis rates of the different biopolymers. The specific rates of change of proteins and nucleic acids (except DNA) matched the dilution rate, both in the light and in the dark period. Carbohydrates were synthesized and stored at a very high rate during the photoperiod, and were metabolized for the provision of energy, and for biosynthesis of other biopolymers in the dark. Cell counts showed no evidence of phased synchrony, although this conclusion was contradicted by changes in DNA and pigments.

Loosdrecht Lakes, origin, eutrophication, restoration and research programme

The Loosdrecht Lakes area is briefly described, light has been shed on its morphology, history, the process of eutrophication with its concomitant phenomena, as well as the planned restoration and research programme.

Restoration and Recovery of Shallow Eutrophic Lake Ecosystems in The Netherlands

Preface. Part One: Aspects of Water Quality Research in Loosdrecht Lakes. Part Two: Eutrophication Research in the Netherlands, with Emphasis on Additional Measures. Part Three: Eutrophication Control in the Netherlands.

Primary production in the various parts of Loosdrecht Lakes

The primary production of the Loosdrecht Lakes, L. Breukeleveen and L. Vuntus is described. A comparison is made between the values found in 1983 (a year with a considerable inlet of phosphorus-rich water, and those of 1984 (when the inlet water was dephosphorized). Production rates in L. Breukeleveen and L. Vuntus were significantly lower than in the Loosdrecht Lakes. This was partly ascribed to horizontal mass transport. The annual production in 1984 was not significantly lower than in 1983.

The state of the environment of the Loosdrecht lakes

The Loosdrecht lakes are a system of shallow, interconnected, peat lakes in the centre of The Netherlands. The main environmental functions of the Loosdrecht lakes are nature and recreation. From the point of view of the Dutch policy, a Specific Environmental Quality (‘Bijzondere Milieukwaliteit’) should be set for these lakes.The most serious environmental problem of the area is eutrophication. The Loosdrecht lakes have, by increasing external phosphorus loading, changed, from clear lakes with few macrophytes, followed by a period of abundant characean growth, to turbid lakes dominated by cyanobacteria and detrital matter. Eutrophication was counteracted by use of sewerage systems and dephosporization of the supply water. The resultant decrease in external phosphorus loading did not result in a decrease of turbidity by suspended particles.The eutrophication of the lake ecosystems was described as a series of phases. One of those phases, the status around 1940, has been used as an ecological reference system.By means of a graphical presentation technique, the so-called ‘AMOEBE-approach’, the state of the environment of the Loosdrecht lakes has been visualized. Thirty-two ecological parameters, including both biotic and abiotic factors, have been selected and quantified. Concrete target values for these parameters have been derived from historical reports and from Lake Western Loenderveen, located close to the Loosdrecht lakes, but less eutrophic.The general conclusion is that the state of the environment of the Loosdrecht lakes is far from what is required with respect to a Specific Environmental Quality, as many of the selected parameters, like water transparency, total phosphorus, mineral nitrogen, cyanobacteria, bream, pike, macrophytes, birds and otter, deviate by over an order of magnitude from their desired levels.

The eutrophic Loosdrecht Lakes: current ecological research and restoration perspectives

Features of the Loodsrecht Lakes, with emphasis on the main lake, are discussed with reference to restoration.Characteristics of the present situation are: (1) very low water transparency-Secchi-disc readings around 0.3 m occur in all seasons; (2) relatively small seasonal changes in sestonic matter; (3) important input of resuspended particles into the seston; (4) predominance of filamentous blue-green algae for most of the year; (5) relative scarcity of crustacean zooplankton, while rotifers are abundant; (6) poor development of littoral communities, and absence of benthic producers. The blue-green algae maintain high population density at very low growth rates: rates of loss are low. The zooplankton grazing rate is low due to inefficient filtering, but predation of larger crustaceans by fish may also be important. Studies on epipelon indicated that loss by deposition may be largely compensated by resuspension.Starting in 1984, the external phosphorus loading was markedly reduced. Results for 1984 and 1985 indicate that complementary measures are needed in order to improve water quality. Action should be directed towards increasing the phytoplankton turnover rates. Accelerated specific growth rate can be expected to accompany lower biomass, more successful competition by other algal groups, and enhancement of grazing pressure.Considering the shallowness of the system, promotion of littoral development and return of submerged vegetation may be important in establishing a new equilibrium of the system.

Growth ofOscillatoria agardhii Gom.

SummaryThe growth kinetics of the blue-green algaOscillatoria agardhii Gom. were studied both in batch culture and in chemostat culture; these allowed Ks and μm values for nitrogen (nitrate) limitation to be determined. There were large differences between the growth kinetics of this organism in batch culture compared with chemostat culture. Some information is further given regarding the influence of various growth limitations on pigmentation and cell composition.

Working group Water Quality Research Loosdrecht Lakes: its history, structure, research programme, and some results

In 1984 the external phosphorus load to the Loosdrecht lakes ecosystem was decreased substantially. A working group, Water Quality research Loosdrecht lakes (WQL), was formed to study the consequences for recovery of the lakes, and to evaluate the water management measures taken. Its history from the start in 1979 is described. The working group had an interdisciplinary character; its organization structure (project management) is depicted. From March 1983 a coordinate multidisciplinary research programme was started, carried out uninterrupted up to December 1990. The programme paid special attention to the flow of phosphorus through the lake ecosystems. The results were presented at several international conferences. The WQL was also involved in the international working group ERiFER (Ecosystem Research in Freshwater Environment Recovery). Important financial support was given by Dutch ministries, the Commission of European Communities, regional water authorities, and private funds.The measures taken to counteract eutrophication were not successful. It has been the task of the WQL to explain the ecosystem resilience.