Coupling of phytoplankton and detritus in a shallow,eutrophic lake (Lake Loosdrecht,The Netherlands)

An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake's trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.     

Juvenile migration of the exclusively pelagic cyprinid,Gnathopogon caerulescens (Honmoroko) in Lake Biwa,Central Japan

Migration of wild and cultivated juvenile honmoroko Gnathopogon caerulescens of from the spawning and nursery areas in Lake Biwa were investigated, both in the Ibanaiko Lagoon and its outlet to Daido River, using beam‐trawl surveys in 2013 and 2014. The study demonstrated migration of G. caerulescens from a nursery lagoon toward Lake Biwa after the juvenile stage. These findings appear to be the first direct evidence for migration of an exclusively pelagic cyprinid species from a littoral nursery to a pelagic adult habitat in a large deep lake.     

Growth rate of alpine phytoplankton assemblages from contrasting watersheds and N‐deposition regimes exposed to nitrogen and phosphorus enrichments

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Salinity and DOC Influence the Distribution of Free-living and Particle-attached Aerobic Anoxygenic Phototrophic Bacteria in the Qinghai–Tibetan Lakes

Aerobic anoxygenic phototrophic bacteria (AAPB) are widespread and play an important role in carbon cycling in the lakes of the Qinghai–Tibetan Plateau. However, little is known about how free-living and particle-attached AAPB distribute with salinity in the Qinghai–Tibetan lakes. In the present study, the abundance and diversity of free-living and particle-attached AAPB were investigated in seven Qinghai–Tibetan lakes with salinity ranging from freshwater to almost saturation (1.2 g L^?1 241.1 g L^?1). An integrated approach was employed including pufL-M gene (encoding the photosynthetic reaction center of AAPB) based quantitative polymerase chain reaction (qPCR) and PCR-cloning phylogenetic analysis. The qPCR data showed that the ratio between particle-attached and free-living AAPB was positively correlated (R² = 0.73, p < 0.01) with increasing salinity. The phylogenetic analysis of pufL-M gene showed that the composition of AAPB population varied with salinity in the studied Qinghai–Tibetan lakes. These results suggested that salinity may be the important factor shaping the AAPB distribution in the studied Qinghai–Tibetan lakes, and AAPB may be adapted to the harsh conditions in the Qinghai–Tibetan lakes by attaching to particles.     

Species composition and seasonal abundance of zooplankton in two Ethiopian Rift Valley lakes — Lakes Abiata and Langano

The composition and annual cycle of the zooplankton of two Ethiopian Rift Valley soda lakes is described. Lake Langano has a conductivity of 1 400 to 1800 µS cm^–1 and a permanent mineral turbidity. Lake Abiata is more concentrated (conductivity 19 000 to 23 000 µS cm^–1) and more alkaline but less turbid; it is characterised by dense phytoplankton blooms, mainly cyanophytes.The zooplankton assemblage is typically tropical, with relatively few species of Cladocera and Copepoda. There was a marked difference in zooplankton between the two lakes, Lake Abiata showing much higher concentrations and greater wet season/ dry season differences. The species composition was also different. Lake Abiata lacked Cladocera, and calanoid copepods occurred only during the wet season with lower conductivities. These two phenomena were attributed to high sodium bicarbonate concentration and to dense cyanophyte blooms. Eleven species of rotifers occurred in Lake Abiata, including six Brachionus spp. but B. rubens was the only rotifer found in Lake Langano. The seasonal variation of the zooplankton is discussed in relation to seasonal fluctuations in conductivity and Chl a concentration.     

Reproductive biology of four large riverine fishes (Cyprinidae) in a man-made lake,Orange River,South Africa

The reproductive biology ofBarbus holubi, B. kimberleyensis, Labeo capensis andL. umbratus was examined in a large reservoir on the Orange River, South Africa. The findings are integrated into the existing knowledge on largeBarbus andLabeo species, which coexist in most river systems in Africa and Asia.LargeBarbus spawn on gravel beds within the river channel during floods in spring or summer. In continuously flowing regulated rivers, time of spawning is governed by water temperatures. They have moderate fecundity; large eggs, incubation time of several days and the larvae are initially immobile with large yolk sacs. In the impoundment, they spawn in the inflowing regulated river withB. kimberleyensis spawning four to six weeks later than the more cold-tolerantB. holubi, the dominant largeBarbus. Survival is generally good and the juveniles disperse throughout the lake, but unseasonal release of cold water from an upstream impoundment may cause poor reproductive success.In contrast,Labeo species generally spawn on newly flooded ground, usually leaving the main river channel. Spawning may or may not be preceded by a longitudinal migration. Labeos are relatively fecund with small (30%Barbus size) eggs which hatch quickly and the larvae swim in bursts up into the water column before sinking down again.L. capensis does not require a longitudinal spawning migration and breeds throughout the lake, depending on local conditions. Large temporal variation in gonadal development within the population can result in more than one spawning. Dispersal within the lake is poor.L. umbratus uses larger inflowing tributaries for spawning thanL. capensis and its juveniles have a much greater power of dispersal. Early dependence on external feeding and undependable occurrence of conditions for spawning and juvenile feeding makes for variable reproductive success.     

Aspects of the history and evolution of Alpine lakes in Austria

The age of lake basins, the onset of meromictic conditions and some consequences of eutrophication and reoligotrophication of Austrian Alpine lakes are presented. The obviously conflicting view of archeologists about lake levels during the period of lake dwellings is brought forward and some data about the effects of fish stocking are discussed.     

Comparison of sediment energy-texture relationships in marine and lacustrine environments

Sediments in the marine environment are generally subject to higher energy levels than those of lake systems, and lakes are virtually unaffected by tidal range which modifies beach structures formed in response to wave effects. However, despite different energy levels, the textural characteristics of both marine and lacustrine sediments are very similar. The main difference between marine and lacustrine facies is the depth range over which these characteristics remain consistent. In lakes, depth limitation may influence the development of surface waves and restrict textural distributions.Simple textural relationships can be used to describe comparable marine and lacustrine sedimentary conditions. Sediments which have been altered by post-depositional erosion, such as lag deposits, or by ice-drop or wind blown settlement, show comparable textural modifications.The settlement of silt and clay size particulates, in the marine environment and lakes, may differ slightly because of the chemical differences between salt and fresh water.     

A technique for examining microspatial distribution of Cladocera associated with shallow water macrophytes

Cladocera living in close association with shallow water macrophytes were collected from specific locations on plants using a device similar to an aspirator bottle. The proposed technique did not differ significantly from plastic bag or cylindrical tube enclosure techniques in sampling Cladocera living on Chara stems. Shaking the plants followed by collection of the surrounding waters seriously underestimated the abundance of plant associated organisms.The method successfully demonstrated diel changes in the microdistribution of Chydorus brevilabris living on stems of the emergent plant Hydrolea ovata. C. brevilabris was most abundant at the bases of vertical stems at midday and appeared to move up the stems and into the water column at night.     

An introduction to the limnology of the Friesian lakes

Between November 1970 and November 1972 nine sampling trips were carried out in the Friesian Lake District. Fourteen lakes were sampled. The chemical composition of the lake water, chlorophyll-a content and the species composition and population densities of zooplankton and benthos were determined simultaneously. Results are discussed in relation to the hydrology of the Lakes system and the morphometry of the individual lakes. The lakes showed a high degree of similarity.