Ramesh D. Gulati

• M.Sc. Ph.D. (Limnology)
• Professor Emeritus at Netherlands Institute of Ecology (NIOO-KNAW) Wageningen, the Netherlands

Changes in body length, carbon content and somatic and reproductive partitioning of assimilated carbon during the lifespan of Euchlanis dilatata lucksiana Hauer are described. The greatest increase in animal size was observed within the first two days of its lifespan, the biomass (expressed in carbon units) of females increased sharply between 1 an...

Lake Zwemlust, a small highly eutrophic lake, was biomanipulated without reducing the external nutrient loading, and the effects were studied for four years. In this paper we pay special attention to the shifts in relative distribution of nitrogen and phosphorus in the different trophic levels and to the changes in growth limitation of the autotrop...

The capacity of Elodea nuttallii (Planch.) St. John and Elodea canadensis Michx. to remove nitrogen from water was evaluated in laboratory experiment. The growth rate of plants and their effect on the nitrogen level of hypertrophic Lake Zwemlust (the Netherlands) as well as on lake water enriched with nitrogen were investigated. The plants grew bes...

Changes in body length, carbon content and somatic and reproductive partitioning of assimilated carbon during the lifespan of Euchlanis dilatata lucksiana Hauer are described. The greatest increase in animal size was observed within the first two days of its lifespan, the biomass (expressed in carbon units) of females increased sharply between 1 an...

During the symposium Restoration and recovery of shallow lake ecosystems in The Netherlands studies on restoration of eutrophic lakes were addressed and discussed. Many Dutch shallow lakes have received high external loadings of phosphorus through supply water that is influenced by the River Rhine and loadings in The Netherlands. Two important Acti...

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 ha...

Data on the water temperature, Secchi depth, water chemistry and phytoplankton and zooplankton of the Loosdrecht lakes, collected during an eight-years monitoring study (1983–1990), were examined using Principal Components Analysis (PCA) and Redundancy Analysis (RDA). The Loosdrecht lakes are highly eutrophic lakes, in which several restoration mea...

Ecosystem research by the working group Water Quality Research Loosdrecht lakes (WQL) was carried out from 1979 to 1990. A coordinated research programme, involving several research institutes and laboratories in The Netherlands, was initiated in 1983, i.e. a year before the reduction of external phosphorus loading by stripping, became effective. T...

The paper summarizes the results of a ten-year (1981–1991) zooplankton research on the Lake Loosdrecht, a highly eutrophic lake. The main cause of the lake's eutrophication and deteriorating water quality was supply up to mid 1984 of water from the River Vecht. This supply was replaced by dephosphorized water from the Amsterdam-Rhine Canal in 1984....

Eurytemora affinis, a calanoid copepod, has been encountered in Volkerak-Zoommeer (Rhine delta region, S.W. Netherlands) both before this lake system was isolated in 1987 from the estuarine influence, and after. It was the main particle-feeding crustacean at all the 3 sampling stations in March–April 1990 when it reached densities of up to 215 ind....

Lake Breukeleveen (180 ha, mean depth 1.45 m), a compartment of the eutrophic Loosdrecht lakes system, was selected to study the effects of whole-lake foodweb manipulation on a large scale. In Lake Loosdrecht (dominated by filamentous cyanobacteria), due to water management measures taken from 1970–1984 (sewerage systems, dephosphorization) the ext...

Lake Zwemlust (area 1.5 ha, Zm 1.5 m) has been the object of an extensive limnological study since its biomanipulation involving removal of planktivorous fish (bream) in March 1987 and emptying of the lake. In the subsequent summer period of 1987 the Secchi depth increased to the lake bottom (2.5 m), compared withca 30 cm in the earlier summers. Th...

At the First Biomanipulation Conference held in Amsterdam (8–11 August 1989), studies presented considered mainly trophic interactions in lakes, enclosures and laboratory systems. Studies on the interactions between phytoplankton and zooplankton emphasized the edibility of the phytoplankton in relation to the zooplankton size structure and the trop...

Whole-lake food-web manipulation was carried out in the hypertrophic Lake Zwemlust (The Netherlands), with the aim of studying the effects on the lake's trophic status and to gain an insight into complex interactions among lake communities. Before manipulation this small (1.5 ha) and shallow (1.5 m) lake was characterized byMicrocystis blooms in su...

In two years after biomanipulation of Lake Zwemlust (The Netherlands), macrophytes (helophytes, elodeids) and filamentous algae developed luxuriantly in the lake. They influenced the structure of macroinvertebrate communities inhabiting them. Macrophytes and algae, by changing environmental and trophic conditions, also affected the composition of m...

Structure and grazing activities of crustacean zooplankton were compared in five lakes undergoing manipulation with several unmanipulated eutrophic (shallow) and mesotrophic (deep) lakes in The Netherlands. The biomanipulated lakes had lesser number of species and their abundance, both of rotifers and crustaceans, and had much larger mean animal si...

A five-year zooplankton study (1982–86) on three shallow and highly eutrophic lakes in the Loosdrecht area (The Netherlands) did not reveal any significant changes following the considerable reduction in external P-loading (from about 1.0 g to 0.3 g P m−2 year−1) since mid-1984. The recent annual fluctuations in the rotifer and crustacean densities...

External phosphorus loads to three shallow lakes in the Netherlands were reduced by eliminating waste-water discharge and by dephosphorization of the supply water, with which water level is controlled. Concentrations of total-phosphorus and chlorophyll a were significantly reduced during 1980–1986 in L. Breukeleveen, but not in L. Vuntus and L. Loo...

Biomanipulation was carried out in order to improve the water quality of the small hypertrophic Lake Zwemlust (1.5 ha; mean depth 1.5 m). In March 1987 the lake was drained to facilitate the elimination of fish. Fish populations were dominated by planktivorous and benthivorous species (total stock c. 1500 kg) and were collected by seine- and electr...

Visual observations and experiments on food preference of Euchlanis dilatata lucksiana show that this euchlanid can feed on blue-green algae not consumed by the most planktonic animals. Nevertheless, even in lakes with blooms of blue-green algae, E. d. lucksiana occur infrequently and generally in low numbers. The paper is an attempt to explore int...

The hypertrophic Lake Zwemlust, a small water body used as a swimming pool, was characterized by algal blooms in summer, reducing the Secchi disk transparency to less than 0.3 m. Since in The Netherlands a Secchi disk transparency of 1 m is obligatory for swimming waters, corrective measures were called for to improve the light climate of the lake....

The biomanipulation study in Lake Zwemlust (area 1.5 ha; mean depth 1.5 m) is among the series of such investigations initiated recently in The Netherlands. The effects of the lake's reffilling (after it was first completely drained empty) almost entirely the nutrient-rich seepage water from the River Vecht flowing nearby and of removal of the plan...

Phosphorus (PO4-P) and nitrogen (NH4-N) excretion rates of Euchlanis dilatata lucksiana, a rotifer, isolated from Lake Loosdrecht (The Netherlands) and cultured in the lake water at 18–19 °C, were measured in the laboratory. In a series of experiments, the effects of experiment duration on the P and N excretion rates were examined. The rates measur...

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1. Effects of cadmium exposure (0.010-0.100 ppm) on food consumption and assimilation rates of crustacean zooplankton from 2 lakes were studied in laboratory using radioisotope (14C) technique. 2. The inhibiting effects were significant 48 hr after Cd-exposure, but not after 20 hr exposure. 3. Daphnia spp. were the most affected cladocerans; copepo...

Phosphorus and nitrogen excretion rates by zooplankton communities from two eutrophic and shallow Dutch lakes were measured in laboratory. The variations in excretion rates in the lakes (May–October) were caused mainly by fluctuation in zooplankton biomass. Mean summer excretion rates (June–September) were 2.4 and 0.9 g PO4P1–1d–1 in Lake Loosderch...

Feeding of Euchlanis dilatata lucksiana, a brachionid rotifer isolated from the Loosdrecht Lakes (The Netherlands), was examined in the laboratory using 14C-labelled food. The gut-filling time at a food concentration of 9.6 g C ml–1 was about 15 minutes. Animals which were fed on 3 size fractions of the lake seston (< 7="" m,="" 7–15="" m,="" and="...

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 in...

During the years 1982- 1984 a number of Dutch and Belgian ecologists studying grazing of zooplankton discussed the methods being employed by them in a working group formed to operate within the Organization for Biological Research in The Netherlands (BION), section Aquatic Ecology. It was felt that the thorough discussions of scientists from the di...

Some of the technical problems specific to the application of radiotracer techniques for measuring grazing of zooplankton are highlighted and, in some cases, the corrective measures suggested. The major drawbacks of measuring zooplankton grazing in the laboratory, for studying the role of zooplankton in nature, namely, changes in water temperature...

The existing data on the species composition of zooplankton and grazing intensities of crustacean plankton are discussed in the light of trophic status, particularly in the Dutch lakes of varying trophy. Several species of rotifers in northern Europe and North America are considered to indicate eutrophic environments. However, unanimity is less reg...

In order to assess the role of the planktonic rotifers in relation to the dynamics of the ecosystem of Parakrama Samudra, the filtering and feeding rates of Brachionus caudatus from Parakrama Samudra and B. calyciflorusfrom the Milk Factory Tank were measured on natural food particles of less than 33 µm, using a radio-tracer technique. The concentr...

The existing data on the species composition of Zooplankton and grazing intensities of crustacean plankton are discussed in the light of trophic status, particularly in the Dutch lakes of varying trophy. Several species of rotifers in northern Europe and North America are considered to indicate eutrophic environments. However, unanimity is less reg...

One station in Parakrama Samudra was sampled at four depths in a 1.6-m water column on seven occasions on 1 September 1979. Sixteen species of rotifers were present, of which ten were carrying eggs. Counts revealed changes in the percentage composition of rotifer species as well as in their distribution with depth throughout the day. The abundance...

The structure, feeding and metabolism of the filterfeeders community of Lake Vechten (The Netherlands) were investigated for seven years in relation to the functioning of the lake’s ecosystem. The 14C-technique used in the grazing and assimilation study is discussed in detail with a critical analysis of the methodological errors. The three major sp...

The review of the present status of limnological studies in India is based on Indian publications in Hydrobiologia since the inception of the Journal. About 325 Indian papers have appeared up to 1979; nearly two-third appeared in the last one decade. Ponds occupy first place among the freshwater bodies studied. There are only a few papers on the ri...

A classified list of the fresh water crustacea of the Netherlands is presented with remarks on the taxonomy, salient features and ecology of common species. The food relations of crustacea, particularly in the light of studies on grazing and assimilation rates of filter feeders in two Dutch lakes, are discussed.

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The studies on the phyto- and zooplankton interrelationships in lakes Vechten and Tjeukemeer are in progress since 1972. For detailed description of the lakes and the techniques employed see GULATI (1974, 1975).

The laboratory techniques for the measurement of secondary production with special reference to herbivore zooplankton are discussed. The hitherto known techniques for the estimation of food budget parameters, i.e., feeding, assimilation, respiration and productivity are critically considered. The recent developments and the application of radioisot...