Ecological studies on the planktonic protozo of a eutrophic reservoir (Rio Grande Reservoir — Brazil)Barbieri, Sioni Maluf;Orlandi, Mirna J. L. Godinho
doi: 10.1007/BF00005966pmid: N/A
Abstract The abundance, composition and seasonal distribution of planktonic protozoans and physical and chemical variables such as temperature, dissolved oxygen content, pH, and chlorophyll a concentration were analyzed monthly from February 1985 to January 1986 in eutrophic Rio Grande Reservoir. Analyses were performed on water samples collected at the surface and bottom (0.5 m above the sediment) in three stations, and individual distribution profiles were constructed for the major species. Dominant protozoan taxa included Codonella cratera, Coleps amphacantus, Coleps hirtus, Halteria grandinella, Mesodinium pulex, Tintinnidium sp., Urotricha spp., Vorticella spp., and Difflugia sp.. The distribution of some species was probably related to temperature and dissolved oxygen content.
Ciliated Protozoan communities in a fluvial ecosystemdel Pilar Gracia, Ma;Castellon, C.;Igual, J.;Sunyer, R.
doi: 10.1007/BF00005967pmid: N/A
Abstract The ciliated protozoan communities in the Llobregat River (Barcelona, Spain) were studied for one year. Samples were taken from 11 different stations. The physical-chemical factors of the water as well as the qualitative and quantitative nature of the ciliate populations were considered. 105 species of ciliates, grouped in 13 orders, were found. The species which constantly appeared at all 11 stations (although not every month) were Litonotus fasciola, Trithigmostoma cucullulus, Cyclidium glaucoma, Glaucoma scintillans, Vorticella microstoma, Oxytricha sp., Stylonychia mytilus, Aspidisca costata and Aspidisca lynceus. The index of diversity at the different stations, and the affinity between the most abundant species, were also determined.
Erosion, phosphorus and phytoplankton response in rivers of South-Eastern NorwayKrogstad, Tore;Løvstad, Øivind
doi: 10.1007/BF00005968pmid: N/A
Abstract The development of P fractions and phytoplankton was studied in three rivers with varying concentrations of seston. Less than 1% of the yearly TP transport may take place during periods with high algal biomass. The observation of a high growth rate of phytoplankton in the rivers coinciding with high concentrations of RP, low content of seston and high TP:Chl a ratio, indicate that the growth was often not P-limiting. During short periods with high phytoplankton biomass the ratio TP:Chl a may be low, indicating that a high fraction of TP was available. The content of P in soil samples and in samples with high seston content was about 0.1% of dry weight, and the algal availability of P often varied between 25 and 75% of TP for both types of samples. Decreasing biomass or low growth rates were observed at secchi depths less than 0.5 m and seston concentrations less than about 25 mg dry weight 1−1. High flow rate also depressed the development of the total phytoplankton biomass. The assimilation of available P is incomplete under such conditions, i.e. under conditions of light limitation and high dilution rate. The availability of P for phytoplankton in rivers with different length, light conditions and stream velocity is discussed.
New species and new records of Callionymus from the Pacific Ocean (Teleostei: Callionymidae)Fricke, Ronald
doi: 10.1007/BF00005970pmid: N/A
Abstract Recently obtained material of Callionymus from the Pacific Ocean includes: Callionymus marquesensis sp. n. (Marquesas Islands), characterized within the C. variegatus-group of the subgenus Calliurichthys by its preopercular spine formula of \(1\tfrac{{4 - 7}}{ - }1\) with an upcurved main tip and a bony keel between the points on the dorsal margin, and a spotted dorsal fin without filaments which is higher than the 1st D2 ray in both sexes; C. pleurostictus Fricke, 1982, record from New Britain and Solomon Islands, with a discussion of competition with C. delicatulus; C.simplicicornis Valenciennes, 1837, record from Society Islands and Marquesas Islands, with a discussion of competition with C. marquesensis; C. obscurus sp. n. (Ambon, Indonesia) which is characterized within the subgenus Spini-capitichthys by its preopercular spine formula \(1\tfrac{3}{{1 - 2}}1\) with an upcurved main tip and very small ventral serrae, its weakly armed head, and its 7 anal fin rays.
Downstream drift of the larvae of Chironomidae (Diptera) in the River Chew, S.W. EnglandWilliams, C. J.
doi: 10.1007/BF00005971pmid: N/A
Abstract The drift of larval Chironomidae (Diptera) was investigated at two sites on the River Chew, using a pump filtration system with 50 µm mesh-aperture aerial nets, situated on the river bank. Chironomid larvae were found to drift in far greater numbers than previously reported, even in slow-flowing water. First and second instar larvae dominated the drift. Variation in drifting behaviour between taxa was observed, where Orthocladiinae drifted in all instars and Chironominae predominantly as first and second instars. Proportionally different rates of drift were observed between these taxa from the benthos at the two sites. It is suggested that the majority of chironomid drift represents an active dispersal and colonisation mechanism by which population redistribution and habitat selection occurs.
Aspects of the phosphorus cycle in Hartbeespoort Dam (South Africa) Phosphorus loading and seasonal distribution of phosphorus in the reservoirThornton, J. A.;Ashton, P. J.
doi: 10.1007/BF00005972pmid: N/A
Abstract Hartbeespoort Dam, a hypertrophic, warm monomictic impoundment in South Africa, receives extremely high phosphorus loads (14.6–25.9 g m−2 a−1) that are dominated by point source discharges from municipal wastewater treatment works. The reduced state of the phosphorus discharged from the works has led to the dominance of the dissolved phosphorus pool by low molecular weight orthophosphates which are analytically detectable as soluble reactive phosphorus (SRP; 60% of total phosphorus pool). Seasonality in the in-lake total phosphorus pool is regulated by a combination of abiotic and hydrological processes; biotic processes appear to play a minor role. Mass balance calculations indicate that between 62 and 77% of the annual total phosphorus inflow load is retained within the impoundment each year.