Metabolism of a subtropical Brazilian lagoon

Total community, planktonic and benthic metabolisms were measured by using the carbon dioxide production and consumption, the diurnal curve' method and the in situ bottle incubation technique over an annual cycle in two sublagoons of the Saquarema Lagoon, Brazil. Metabolic rates of the phytoplankton-based lagoon were characterized by considerable daytime and daily variability in production and respiration, by a seasonal shift between net autotrophy and heterotrophy and by an annual balance of production (P = 105 ± 65 mmoles/m²/dayn = 25) and respiration (R = 102 ± 50 mmoles/m²/dayn = 25). Total community metabolism was similar throughout the lagoon, but phytoplankton assimilation rates and benthic respiration showed spatial differences. Bottle incubations compared to total community free water respiration suggested that the pelagic community was 2–5 times more active than the benthos     

Rapid acquisition of three-dimensional triple-resonance experiments using pulsed field gradient techniques

Summary A rapid method for recording three-dimensional triple-resonance experiments utilising pulsed field gradient techniques is proposed, and applied to the HNCO experiment. In order to optimise the sensitivity of the method, a short phase cycle is used in conjunction with the pulsed field gradients to select the desired coherence transfer pathway. The method is demonstrated for the HU protein.     

青龙河底栖无脊椎动物群落结构及其水质评价

本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。     

Species number, species abundance and body length of arboreal arthropods associated with an Australian rainforest tree

Abstract.

• 1 The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over-storey rainforest tree from Australia, Argyrodendron actinophyllum (Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2-year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.
• 2 The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log-series nor the log-normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.
• 3 The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three-dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.
• 4 Although several factors may complicate the interpretation of the three-dimensional plots, long-term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structure in rain forests.

     

Observations on the relation between phytoplankton diversity and environmental factors in the Vaal River at Balkfontein,South Africa

The relationship between specific environmental factors as independent variables and temporal changes in phytoplankton community structure in the Vaal River (a turbid system) during 1984 was investigated by employing different diversity indices. Temporal changes in community structure reflected temporal changes in certain environmental factors. Phytoplankton diversity, measured with Shannon-Wie H' and Hurlbert PIE indices, was related firstly to discharge and discharge derived variables (such as SO₄, Si, N and P loading) and secondly to turbidity derived variables (such as euphotic zone depth). Discharge appears to be of prime importance in affecting diversity. Observations were made that shed new light on conditions contributing to the development of an August peak (dominated by Stephanodiscus hantzschii fo. tenuis and Micractinium pusillum) in phytoplankton concentration. Increased environmental stress may reduce the number of sensitive species, thus reducing interspecific competition between tolerant species which could then exploit the — for them — more favourable conditions resulting in an increase in their numbers to peak concentrations.     

Enucleation of protoplasts derived from suspension cultures of winged bean and from a crown gall cell line ofParthenocissus tricuspidata

Protoplasts derived from suspension cultures of the winged bean and a crown gall lineof Parthenocissus tricuspidata were enucleated by centrifugation on iso-osmotic discontinuous Percoli gradients and on discontinuous sucrose-mannitol density gradients. Enucleation was achieved according to the buoyant density of the protoplasts and preparations of both cytoplasts and miniprotoplasts were recovered. The Percoll gradients gave more satisfactory results than the sucrose-mannitol gradients. Enucleation was increased by raising the centrifugal force from 20 kg to 60 kg. The presence of nuclei was determined by the DNA specific probe 4′6-diamidino-2-phenylindole (DAPI). Membrane integrity, as measured by staining with fluorescein diacetate, showed that some 85 % of the cytoplasts were bounded by an intact plasma membrane.     

Pelagic rotifers of Lake Glubokoe from 1897 to 1984

After alteration in the pattern of drainage of run-off from the surrounding swamps and changes in the colour and transparency of the Lake Glubokoe water, the previously epilimnial Trichocerca similis, Conochilus unicornis and Keratella cochlearis showed a shift of their maximum numbers to deeper layers. Pompholyx sp. and Trichocerca capucina, which are regarded as indicators of eutrophic waters, have disappeared from the pelagic zone of the lake and Conochilus hippocrepis, Synchaeta pectinata, Gastropus stylifer, Asplanchna herricki, Ascomorpha ecaudis, Ascomorpha saltans, Euchlanis dilatata and Trichocerca porcellus have made their appearance. Most of the new species are considered to be indicators of oligotrophic conditions. However the total density of pelagic rotifers remained at the same level. Apparently the establishment of the new species of rotifers was possible due to some ‘rarefaction’ of the epilimnion, the disappearance of predaceous Mesocyclops leuckarti and the invasion of the pelagic zone by Peridinium cinctum.     

Suivi pluriannuel du peuplement à Abra alba dans la partie méridionale de la Mer du Nord (région de Dunkerque-France)

The Abra alba community is considered as a faunistical unity well established on coastal areas of North Sea. This community shows, since several years, very important recruitments of certain species. Since 1978, recruitments of Abra alba, Tellina fabula, Phyllodoce (Anaïtides) mucosa, Lagis koreni or Lanice conchilega have been observed. However these demographic phenomena does not affect the structure of the community, which shows, through rank-frequency diagrams, the characteristic of a mature population, principally constituted of 7 species.An annual cycle study shows a succession of recruitments of several species. A correspondance factorial analysis was realised from grain size datas as well as abundances of 18 main species. This analysis shows an annual cycle which seems to be linked to the clay part. Maximal values of clay part appears in summer and minimal values at the end of winter or early springtime.The hydrological parameters studied, allowed to make the difference between external factors (continental contributions, phytoplanctonic activity etc...) and benthic activity.

     

The fish community of the Loosdrecht Lakes and the perspective for biomanipulation

In a two-year-study, the fish community of the Loosdrecht Lakes area was characterized with regard to the professional fishery and the forage base. The lakes are shallow (mean depth 2 m) and eutrophic to hypertrophic. The bream,Abramis brama, dominates the fish biomass. The pikeperch,Stizostedion lucioperca, is the main predator.Bream up to 30 cm have a slow growth rate and are in a bad condition. A faster growth rate and a better condition are shown by bream of 30 cm and more. The small bream feeds on chironomid larvae, benthic cladocerans and zooplankton. The better condition of bream over 30 cm is explained by the more efficient feeding of larger bream onChironomus plumosus larvae. Pikeperch show a fast growth rate and a good condition. Recruitment is limited by the low densities of smelt,Osmerus eperlanus, leaving cannibalism as the most important way for the 0+ pikeperch to become piscivorous and to manifest a fast growth.The impact of the professional gillnet fishery on bream and pikeperch is small because the mesh sizes in use are as large as 75–100 mm bar mesh.The planktivorous 0+ pikeperch consumes mainly the carnivorous zooplanktersLeptodora kindtii and cyclopoids. The zooplankton community lacks large herbivorous species likeDaphnia hyalina, capable of consuming bluegreens. A possible experiment in biomanipulation with a view to find out whether the development ofD.hyalina is depressed by the small planktivorous cyprinids, is predator enhancement with the aid of a stocking programme for indoor-raised 0+ pikeperch in early summer.