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Genetic testing is still rarely used for the diagnosis of dyslipidemia, even though gene variants determining plasma lipids levels are not uncommon.

Consumer biomass and spatial distribution in the equatorial alkaline-saline Lake Nakuru were studied from 1972–1976. These data will provide the basis for estimating feeding and production rates and for quantifying energy flow at the consumer level. Two of the main consumers, the Lesser Flamingo (Phoeniconaias minor) and the Soda Tilapia (Sarotherodon alcalicus grahami), were covered by earlier papers. The biomass of the only planktonic crustacean, the copepod Lovenula (=Paradiaptomus) africana was very high (1.5 gDW (dry weight)·m-3, mean in 1972/73) in comparison with other tropical lakes. Lovenula was absent in 1974 and 1975, and at very low levels (0.1–0.4 gDW·m-3) in part of 1976. Among the rotifers Brachionus dimidiatus dominated in 1972/73 (˜0.2 gDW· m-3), but was outnumbered by B. plicatilis throughout most of 1974 to 1976 (mean total rotifer biomass 1.4 gDW· m-3, peak densities 7 gDW·m-3); during high salinity periods (>20‰) Hexarthra jenkinae occurred in very low numbers. For short periods rotifers can be the dominant species of L. Nakuru. Aquatic heteroptera (four species) played a minor role: they contributed 0.4% to total consumer biomass in 1972/73; in 1974–1976 the lake had no aquatic heteroptera. Benthic biomass (0.4 gDW·m-2) was within the range of other tropical lakes, it consisted almost exclusively of Leptochironomus deribae. Bird counts of the twelve most important species are given for the years 1972–1974: Pelecanus onocrotalus accounts for ˜90% of the biomass (0.44 gDW·m-3, mean 1972/73) with peak densities of almost 20,000 birds.-The consumer organisms covered by this and the two preceding papers represent >99% of L. Nakuru's consumer biomass. Population dynamics of various consumer species are discussed.

The ultraviolet (UV) sensitivity of five species of freshwater zooplankton (three Cladocera, two Copepoda) were investigated. The animals were exposed to varying levels of UV-radiation in a sunshine-simulator and the UV doses for 10 and 50% mortality (LD10, LD50) were estimated using a dose-response model. To place these doses in context they were compared with modelled clear-sky surface UV irradiances in New Zealand. The cladocerans Daphnia carinata and Ceriodaphnia dubia were sensitive to levels of UVB irradiance of LD10 = 18-25 kJ m-2 and LD50 = 35-37 kJ m-2. These sensitivities are consistent with published values for other cladocera. In contrast a third cladoceran, Bosmina meridionalis, exhibited no higher mortality over the full range of the cumulative UVB-doses used (3-40 kJ m-2) than controls receiving no UV exposure. The copepod Boeckella delicata showed the highest UV-sensitivity of all organisms tested (LD10 = 7 kJ m-2, LD50 = 33 kJ m-2) whereas for Boeckella triarticulata, which was more heavily pigmented than B. delicata, no UV-induced mortality was observed. Under natural conditions UV irradiances of up to 100 kJ m-2 day-1 can fall on the surface of New Zealand lakes. Although this is attenuated in natural waters, these data suggest that UVB irradiance may be a significant ecological variable to some zooplankton species.

Vertical migration is a key subject in understanding zooplankton ecology and its influence on aquatic ecosystems. This paper introduces a device for automatically recording vertical plankton migrations to study proximate factors regulating the stimulus, timing and amplitude of these movements under controlled laboratory conditions. The instrument records the light scattered by organisms at their respective depths and processes the signals in real time to a graphic representation of the organisms vertical distribution. Organisms of different taxa from a size of <40 μ, to > 10 000 μm were used for these experiments. Daphniamigrations in response to UV light are used to demonstrate the basic functions of the instrument.

Depth-dependent photoadaptational responses of the Red Sea zooxanthellate coral (Leptoseris fragilis) were studied down to 160 m from the research submersible GEO. Light saturation curves for photosynthesis revealed, with IC=1-2, IK=10.9 and Isat=20 µE·cm-2·sec-1, the lowest values of photokinetic parameters ever reported for a symbiotic coral. In summer, positive net production occurs only around noon at approx. 100m depth. Biomass parameters of corals at 100–135 m are negatively correlated with depth in algal cell density, protein, chlorophyll and carotenoid but not in pigment ratios or cell based pigment content. Coral size decreased with depth. Corals transplanted from 110–120 m original depth to 40, 70, 90 and 160 m showed high survival after one year. O2-production and dark O2-uptake increased with decreasing transplantation depth. After one year, transplants at 70 and 90 m but not at 40 m had higher algae density and pigment concentrations. The host light-harvesting systems described by Schlichter, Fricke and Weber (1986) are partially destroyed in 40 m but not in 70 and 90 m transplants. Different light exposures alter P-I-responses (Pmax, IC, IK, Isat) but not biomass parameters, indicating molecular or biochemical adaptation. The coraal's optimal light fields lie between 70 to 90 m. Its exceptional bathymetric distribution is linked with the newly discovered host light-harvesting systems which probably enhance photosynthetic performance in a dim environment.

The Cichlid fish Tilapia grahami (-Sarotherodon alcalicum grahami) was introduced into Lake Nakuru (Kenya) in about 1960 and is now one of the main herbivores. Spatial distribution and biomass changes were estimated from lift net catches from 1972–1974 which were partly continued until 1976. The length/weight relationship is represented by the equation W=0.008·l2.98 (W=dry weight=24% of fresh-weight; l=standard length=85.1% of total length). The fish distribution is very patchy (aggregation coefficient 5.2–12.2). The density decreased and the mean fish size increased from in-shore to off-shore regions. At noon the fish concentrate near the shore and at hight they move off-shore, a migration pattern probably reflecting a preferance for higher temperatures. 70% of Tilapia concentrate in the top 50 cm and 80% in the top 100 cm. The total ichthyomass of the lake had a mean of 90 t dry weight (=2.1 g/m2) in 1972 and it increased to a mean of 400 t dry weight (=10.2 g/m2) during 1973. Possible causes for the spatial distribution and the biomass variations are discussed. The high density of Spirulina platensis makes nutritional competition among the herbivores unlikely. The main impact of Tilapia grahami on the lake's ecosystem is a substantial increase in diversity by extending the food chains to fish eating birds, of which the Great White Pelican is dominating. The breeding of Pelicans at a neighbouring lake causes a considerable nutrient export (~13 t phosphorus/year).

Consumer production and consumption were studied in the equatorial alkaline-saline Lake Nakuru from 1972 to 1976. Together with earlier reports (including a study of the dominant consumer, the Lesser Flamingo Phoeniconaias minor), the data provide the basis for estimating the major pathways of energy flow. Detritus food chains were not included in this project.

The major pathways of energy flow in Lake Nakuru (East Africa) are presented. The trophic structure of this equatorial alkaline-saline lake shows no predictable long term continuity. During the five years of this study it had a bloom of Spirulina platensis that persisted at least two years, it had periods with low algal densities and in addition it had various transitional phases with dramatic fluctuations of species composition and density.

Abiotic factors, standing crop and photosynthetic production were studied in the equatorial alkaline-saline closed-basin Lake Nakuru (cond. 10,000–160,000 µS). Meteorological conditions and abiotic factors offer suppositions for a high primary productivity: mean solar radiation is 450–550 kerg·cm-2·s-1, with little seasonal variation, regular winds circulate the lake every day and nutrient concentrations are usually high (>100 µg P-PO4·l-1). Oxygen concentrations near sediments were <1 gO2·m-3 for at least 6 h·d-1 in 1972/73, resulting in a release of ~45 mg P-PO4·m-2·d-1. Attenuation coefficients vary from 3.6–16.5 according to algal densities and mean depth from 0–400 cm. Algal biomass was ~200 g·m-3 (d.w.) in 1972/73, due to a lasting Spirulina platensis bloom (98.5% of algal biomass). In 1974 algal biomass suddenly dropped to 50 g·m-3 (d.w.). Spirulina and several consumer organisms almost vanished, but coccoid cyanobacteria, Anabaenopsis and diatoms increased. Several causes for this change in ecosystem structure are discussed. The use of the light/dark bottle method to measure photosynthetic production in eutrophic alkaline lakes is discussed and relevant experiments were done. Oxygen tensions of 2–35 gO2·m-3 do not influence primary production rates. Net photosynthetic rates (mgO2·m-3·h-1; photosynthetic quotient=1.18) reached 12–17.7 in 1972/73 and 2–3 in 1974, but vertically integrated rates were only 1–1.4 in 1972/73 and 0.8 in 1974, and daily net photosynthetic rates (gO2·m-3·24 h-1) 3.5 in 1972/73 and 1 in 1974. 50% of areal rates were produced within the 10 most productive cm of the depth profile. The disproportion between high algal standing crops and relatively low production rates is due to self-shading of the algae, reducing the euphotic zone to 35 cm in 1972/73 and 77 cm in 1974. Efficiency of light utilization is 0.4–2%, varying with time of day and phytoplankton density. In situ efficiencies show an inverse relationship to light intensities. Photosynthetic rates of L. Nakuru remain within the range of other African lakes (0.1–3 gO2·m-2·h-1). The relation of O2 produced/Chl a of the euphotic zone is 50% lower then in tropical African freshwater lakes and conforms to lakes of temperate regions.

The shallow, alkaline pan of Lake Nakuru (conductivity 15,000–25,000 µmho/cm, 20°C) usually maintains an exceptionally high standing crop of the cyanophyte Spirulina platensis (150–200 mg DW/l; DW=dry weight), the main food of a large population of the lesser flamingo (Phoeniconaias minor). The abundance and feeding of the lesser flamingo were studied in an attempt to quantify the lake's energy flow. Some data on other rift valley lakes with similar chemical and biological conditions are included, since they are inhabited by flamingos as well. The spatial distribution and total population of the flamingos were monitored on a monthly basis. The birds were counted automatically from aerial photographs by a particle counter. The mean was 915,000 in 1972 and 1973, and in 1974 the population dropped to a mean of 113,000. The population also showed pronounced short time fluctuations that are correlated with algal densities. Other possible causes for flamingo migrations are discussed. Flamingos feed by filtering planktonic organisms from the water with their bill. Feeding experiments with caged birds gave a clearing rate of 31.8±1.3 l/h (SE; SE=standard error) for an adult flamingo, a pumping rate of 17.5 strokes/s and a feeding rate of 5.6 g DW/h at the mean algal concentration of 180 mg DW/l in 1972/73. The mean feeding time in that period was 12.5 h/d, which gave a daily feeding rate of 72±6.5 g DW for an adult bird and 66±6 g DW for the average bird (juveniles included). Therefore the whole flamingo population extracted per day ~60 t DW of algae (0.7 g DW/m3/d or 3 kcal/m3/d) from the lake. This is 50–94% of the daily primary production or 0.4 to 0.6% of the algal biomass and two to three times the amount all other primary consumers are feeding. About 0.75 kcal/m3/d are returned by fecal and urinary wastes. These feeding rates are slightly lower than calculations based on basic metabolic rates of birds.

Single olfactory receptor cells of the migratory locust and of honeybee drones were stimulated with the two enantiomeric forms of 4-methylhexanoic acid. In the majority of cells, equal stimulus quantities of either the (+)- or the (-)-isomer elicited a greater number of nerve impulses. Behavioral discrimination of the two enantiomers was demonstrated in drones. Here, the proboscis extension response served as indicator of the discrimination following the conditioning to one or the other steric antipode. These findings are explained by a minimum of two variants of one structurally highly stabilized type of acceptor present in different numbers on the membranes of individual cells of this type.

The proboscis extension reflex was used for conditioning worker and drone bees to odours. Six odours, including queen substance and the scent to the Nassanoff gland were used as conditioning stimuli. The animals could clearly distinguish the odours from one another.

Abstract: The poster gives main results of a study on the relevance ofPhaeocystis globosa (Haptophyceae) as a food source forM. edulis (Ökosytemforschung Niedersächsisches Wattenmeer, TP A 3.1). DensePhaeocystis blooms were suspected to be one reason for the observed decrease of the mussel population of the Wadden Sea of Lower Saxony within the last decade. During the same period density and duration ofPhaeocystis blooms increased in the coastal regions of the North Sea. These blooms are dominated by the colony form ofPhaeocystis (diameter of colonies: some urn up to 2 mm; max. observed density 100,000 colonies 1−1). It was suggested, that mussels would not be able to feed on the gelatinous colonies ofP. globosa due to inhibition of filtration. Therefore, mussels would suffer from starvation during bloom time, leading to growth reduction.