Murchison Bay Research Articles

Relationships between wetland ecotones and inshore water quality in the Ugandan coast of Lake Victoria

Much of the lake shore in Lake Victoria is covered by extensive wetlands, often dominated by dense papyrus stands that extend out over the lake waters. These wetlands, their extension and management play a role in the physical, chemical and biological conditions of the inshore waters. Continuous transects along 180 km of shoreline together with spatial grids of sampling sites in eight bays were performed in the Ugandan inshore waters in order to analyze the relationships between the wetland characteristics and water quality. Measurements of extension of the wetland ecotones, water temperature (T), pH, Secchi disk depth (SD), dissolved oxygen (DO), total nitrogen (TN), total phosphorous (TP), dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and chlorophyll-a (CHL) were made in each sampling area. Data of T, pH and DO collected during the transects showed that the water characteristics of the bays differ from the open shoreline. Moreover, the magnitude of these physical–chemical differences is strongly conditioned by the dimension of the bordering wetlands. Bays with extensive wetlands ecotones were characterized by cooler, more acidic and poorly oxygenated waters. TN : TP ratios and especially DIN : SRP ratios decreased with the wetland presence along the coastline, showing a higher probability of N limitation in the inshore waters where large wetlands are present. Results point to denitrification processes in the wetland ecotones as the cause of this trend. The distribution of CHL was found to be highest in the presence of two significant point loading sources: a river (in Katonga Bay) and a major population centre (Kampala, in Murchison Bay). The reduction of external P loading is shown as an important step in the management of the eutrophication process of Lake Victoria inshore waters.

Active biomonitoring of trace heavy metals using fish ( Oreochromis niloticus) as bioindicator species. The case of Nakivubo wetland along Lake Victoria

The Nakivubo wetland in Uganda, which feeds Lake Victoria at Murchison bay, has become severely degraded over recent years and is particularly threatened by the expansion of industry, settlement and cultivation on its fertile fringes. The aim of this study was to actively biomonitor selected trace heavy metals using Nile tilapia ( Oreochromis niloticus). Nile tilapia was set in cages at six sampling sites in Murchison bay for a period of six weeks, and sampling was done every 2 weeks for active biomonitoring and weekly for physico-chemical variables. The control (site 7) was at the Aquaculture Research and Development centre, Uganda. Fish tissue was dissected and gills, liver and muscle removed for heavy metal analysis. Water samples and fish tissue from each site were analysed using Atomic Absorption Spectrophotometer (AAS) to determine metal concentrations of zinc, copper, chromium and manganese. Site 4 had the highest average NH 4–N of 14.28 ± 12.73 mg/l which was above effluent standards for Uganda. From the findings, there were significantly higher concentrations of heavy metals in fish than in water ( p > 0.01). Fish kills were recorded highest for sites 4 (55%), 5 (77.5%) and 6 (60%) in less than six weeks indicating high levels of pollution. Gills showed the highest accumulation of copper after a period of six weeks as compared to other metals with a mean ± SE of 11.7 μg/mg wet weight. In general, the order of accumulation of metals in tissue after six weeks was in order; copper > zinc > chromium > manganese and gills > liver > muscle. In conclusion, active biomonitoring was found to be a good tool for monitoring water quality as it integrates responses to combinations of all contaminants thereby indicating overall effects in a water body. To improve the study, there is need to incorporate post mortem studies and biomarker analysis since the later can give early warning of pollution before fish kills are observed.

Comparative assessment of the value of papyrus and cocoyams for the restoration of the Nakivubo wetland in Kampala, Uganda

Nakivubo wetland, located on the northern shores of Lake Victoria, separates the city of Kampala from the Inner Murchison Bay of Lake Victoria (the sole raw water supply for Kampala). It provides tertiary treatment for the secondary effluent from the Bugolobi sewage treatment works, and heavily polluted wastewater (run-off, domestic and industrial effluents) from the Nakivubo channel. However, more than half of the wetland has been drained for agriculture and the natural papyrus vegetation ( Cyperus papyrus) has been progressively replaced by cocoyams ( Colocasia esculenta). In order to provide information that could be used in the restoration of Nakivubo wetland, a pilot study was carried out to assess the ecological characteristics (nutrient retention and growth characteristics) of the two plants. The plants were grown in wastewater effluent from the Bugolobi sewage treatment works, in experimental buckets under floating and rooted conditions. The wastewater was replaced every seven days. Papyrus plants were more efficient at removing NH 4-N while growing floating in wastewater or rooted in gravel (maximum values being 89.4% and 79%, respectively) than were cocoyams (67.7% and 68.3%) or the controls without plants (11% and 9%, respectively). The removal of orthophosphate by papyrus was also greater under the two growing conditions (values being 80% and 73%) than by cocoyams (66% and 63%) or the controls (11% and 14%). Biomass densities of papyrus were also higher (16.9 kg Dw/m 2 for the floating plants and 18.7 kg Dw/m 2 for the rooted ones) than of yams (5.9 kg DW/m 2 and 6.8 kg DW/m 2, respectively). It was also observed that the rhizomes of yams did not develop well under the floating conditions and were often rotten. It is concluded that, since papyrus has better wastewater treatment efficiency and superior growth characteristics, it should be encouraged to grow again in the wetland. It was also noted that if encroachment of the wetland by agricultural activities is halted, papyrus would eventually out-compete the yams. Keeping Nakivubo wetland inundated would offer papyrus a competitive advantage, since yams grow poorly when floating in water.

Lake flies in Lake Victoria: Their biomass and potential for use in animal feeds

Insects exhibiting swarming habits in Lake Victoria include mainly the Chironomidae, the Chaoboridae and Povilla adusta (Ephemeroptera). Their early life cycles are spent in the lake as benthos and standard bathymetric procedures were undertaken to estimate the standing crop biomass of the larvae in Murchison Bay. Povilla was principally a boring invertebrate preferring dried logs (113 g Povilla nymphs per kg of host plant material). Cyperuspapyrus carried 5 g C. denudatus 2.5 g and Phragmites mauritanus 1.0 g of Povilla per kg of host plant material. Povilla also occurred in the benthos at 40 g/m2. The Chironomidae and Chaoboridae had a mean standing crop biomass of 80 g/m2 and 3 g/m2 respectively. Their total biomass for the bay was estimated at 16060 metric tonnes for the Chironomidae, 7920 m. t. for Povilla and 660 m. t. for the Chaoborids. Adult swarming habits of the lakefly were closely correlated with lunar phases and the adu Its were easily trapped at night using kerosene lamps. Biochemical tests of the nutrient value of lakefly showed high levels of protein content (62%), minerals (18%), a low fat content (3.9%) and low moisture content (9%). This makes the lakefly ideal as an additive in animal feeds and growth experiments with poultry and aquaculture fish are currently going on to test the suitability of lakefly as an ingredient in animal feeds.

Observations on the benthos of Murchison Bay, Lake Victoria, East Africa

SummaryThere is paucity of data on benthic organisms in Lake Victoria, as in many other African lakes. A study to ascertain the biomass, standing crop and spatial distribution of benthic organisms in the northern shores of Lake Victoria indicated a rich benthic fauna composed mainly of insects, molluscs and oligochaetes. Total biomass for the 200 km2 Murchison Bay was 146,000 tonnes. The lamellibranchs formed the highest biomass (68,940t) followed by gastropods (30,840t), insects (25,760 t) and annelids (20,460 t). Mean standing crop biomass values for genera in the various taxa were determined from their spatial distribution patterns (mean numbers per unit area) and mean individual weights. The high benthic biomass is currently under‐utilized by benthic organisms at higher trophic levels and consequently represents utilizable organic matter directly or indirectly for man's benefit. Hence, a lakewide study is recommended.RésuméOn possède peu de données sur les organismes benthiques du lac Victoria come de beaucoup d'autres lacs africains. Menée dans le but de connaître la biomasse, l'inventaire et la distribution spatiale des organismes benthiques sur les bords nord du lac Victoria, une étude a révélé une faune benthique riche, composée principalement d'insectes, de mollusques et d'oligochétes. La biomasse totale pour les 200 km2 de la Murchison Bay était de 146,000 tonnes. Les lamellibranches en composaient la plus grande part (68,940 t), suivis par les gastéropodes (30,840t), les insectes (25,760t) et les annelides (20,460t). Les valeurs moyennes de biomasse par genre des différents taxons ont été déterminées à partir du schéma de leur distribution spatiale (nombres moyens par unité de surface) et du poids individuel moyen. La biomasse benthique élevée est actuellement sous‐utilisée par les organismes benthiques des ordres trophiques supérieurs et représente par conséquent une matière organique directement ou indirectement utilisable au profit de l'homme. On recommande donc une étude à l'échelle du lac entier.

Driftwood in Svalbard as an Indicator of Sea Ice Conditions

The amount and type of driftwood logs on raised beaches in Svalbard probably indicate variations in sea ice conditions through time in the Arctic Ocean. This idea is based on the fact that wood floating in water has a limited buoyancy. The maximum period of buoyancy for coniferous wood (Picea/spruce, Larix/larch, Pinus/pine) is between 10 and 17 months: for broadleaves (Betula/birch, Salix/willow, Populus/aspen) from 6 to 10 months. The buoyancy depends on many circumstances but foremost on the properties and basic density of wood when the drift starts. Two dominant drift features are evident in the Arctic Ocean. The Pacific Gyral has a clockwise circulation in the Beaufort Sea. There are large variations in the rate of drift of this circulation, but the average speed is probably 700-800 km/year. The Transpolar Drift Stream runs from the Siberian coast to Svalbard and north Greenland and the average drift rate 600 km/year may be close to the actual net speed of an ice floe or a log of driftwood. The passage from the Siberian coast to the Svalbard area takes, roughly, five years. A trunk with the best possible buoyancy sinks after a third of that time. However, because of rafting on or in the sea ice, driftwood logs land on the islands of Svalbard. Most of the wood on the eastern islands of the archipelago is coniferous wood of Siberian origin. There are at least two easily noticeable zones on the shores with raised beaches where the amount of driftwood is small. These zones probably represent climatic conditions with periods of summers; a high percentage of open water and a northerly position of the ice limit. Introduction and field work During the YMER-80 expedition in July and August 1980, field investigations were made in the Svalbard area (Schytt 1981). The research of the land parties was concentrated to studies of the present and Pleistocene glaciation of Svalbard. A field party with six members worked primarily with lake sediments in Nordaustlandet and another party on Storoya with glaciological investigations. A third group, Lars Brydsten, Anders Haggblom and Ann-Cathrine Ulfstedt started the field work on Glenhalvoya, Nordaustlandet. Brydsten and Haggblom continued the field investigations at Braastadskardet, the north coast of Hopen and later on Kapp Platen, Nordaustlandet. The icebreaker Ymer called at both Stor6ya and Murchison Bay (Kinnvika, the old polar research station from I.G.Y. 1957-59) on her way to Longyearbyen. Members of the landparties left Svalbard by the regular airline to Norway. Already after our investigations on Hopen in 1965 (cf. Hoppe et al. 1969) the interest was focused on driftwood. An interpretation of both the origin of wood and the varying amount of driftwood on the raised beaches seemed important. The field studies of beach morphology and Arctic driftwood were therefore included as a part of the land-based research during YMER-80. The icebreaker and research vessel Ymer was an excellent base for both the scientific work and the important transports. Driftwood in the Arctic The occurrence of driftwood along Arctic beaches was noted by the first polar explorers. The driftwood along the beaches of Iceland was described in detail as regards type, amount, economic usefulness and origin by Olavius in an economic report from Iceland (Olavius 1780). The biological context of the driftwood in northern Svalbard, particularly that from Ltagoya, was described by Pennant in 1784. This resource had been exploited by people of the Arctic cultures long before that. When Eurola (1971) published a summary of earlier studies concerning Arctic driftwood, he noted that one hundred years had passed since Agardh's (1869) classical work on driftwood appeared. Eurola also describes botanical analyses of the wood structure of 19 of his own samples from Agardh Bay in Spitsbergen. Common to previous studies of driftwood have been analyses of wood structure in order to Geografiska Annaler 64 A (1982) 1-2 81 This content downloaded from 157.55.39.144 on Wed, 07 Sep 2016 05:24:27 UTC All use subject to http://about.jstor.org/terms

On the possible influence of the magnetic activity on the atmospheric electric parameters

The potential gradient and air-earth conduction current density measurements made simultaneously at Payerne and Murchison Bay during the periods July–October 1957 and July-October 1958 have been analysed to yield what is believed to be an indirect evidence of the influence of the geomagnetic activity.

Statistical studies of the performance of cosmic ray recording instruments

A method is presented to determine the variance of statistical fluctuations in cosmic ray data derived from the neutron monitor, the duplex cubical counter telescope and the directional telescopes. The standard deviation of the error distribution from instruments at the cosmic ray stations at Uppsala, Murchison Bay and Mt. Wellington is estimated by the method. The results are compared with the Poisson distribution and it is stressed that the use of the Poisson distribution will give an underestimate. The results offer standard error calculations of cosmic ray data. DOI: 10.1111/j.2153-3490.1962.tb00117.x

Direction of the cosmic ray anisotropy

Inclined meson telescopes at Uppsala, Kiruna, and Murchison Bay have been employed to determine the direction of the C.R. diurnal anisotropy. The six mean asymptotic directions are distributed between approximately 15° N and 80° N. It is being shown that the flow of excess particles responsible for the anisotropy is parallel to the orbital plane of the earth. All atmospheric effects have been considered as well as the partial smoothing out of the diurnal variation through the longitudinal distribution of the asymptotic directions. Inside the limits of error the yearly mean amplitudes fit a linear function of the cosine of the angle between the equatorial plane and the mean asymptotic direction. The direction of the anisotropy makes an angle of approximately 90° with the earth-sun line, the flow of excess particles overtaking the earth. DOI: 10.1111/j.2153-3490.1962.tb00116.x

On the pressure dependence of the cosmic ray intensity recorded by the standard neutron monitor

Pressure coefficients have been determined for some standard neutron monitors at high latitudes for the years 1957–1959 with due regard to variations of primary origin. The following coefficients were obtained: (1) for Murchison Bay and Uppsala ? = ?0.710±0.006 per cent/mb; (2) for Resolute, Churchill and Ottawa ? = ?0.725±0.005 per cent/mb; (3) for Mawson and Mt. Wellington ? = ?0.736±0.004 per cent/mb. The differences in ? between the three groups of stations are certainly not due to a purely statistical scattering. They probably reflect dissimilarities in the neutron monitors and the pressure recording devices. As a by-product it has proved that for two stations above the latitude knee, the quotient between the pressure corrected daily neutron intensities is remarkably constant in time. It can thus be used as a sensitive indicator of changes in counting rate. DOI: 10.1111/j.2153-3490.1962.tb00118.x

Statistical studies of the performance of cosmic ray recording instruments

A method is presented to determine the variance of statistical fluctuations in cosmic ray data derived from the neutron monitor, the duplex cubical counter telescope and the directional telescopes. The standard deviation of the error distribution from instruments at the cosmic ray stations at Uppsala, Murchison Bay and Mt. Wellington is estimated by the method. The results are compared with the Poisson distribution and it is stressed that the use of the Poisson distribution will give an underestimate. The results offer standard error calculations of cosmic ray data.

Direction of the cosmic ray anisotropy

Inclined meson telescopes at Uppsala, Kiruna, and Murchison Bay have been employed to determine the direction of the C.R. diurnal anisotropy. The six mean asymptotic directions are distributed between approximately 15° N and 80° N. It is being shown that the flow of excess particles responsible for the anisotropy is parallel to the orbital plane of the earth. All atmospheric effects have been considered as well as the partial smoothing out of the diurnal variation through the longitudinal distribution of the asymptotic directions. Inside the limits of error the yearly mean amplitudes fit a linear function of the cosine of the angle between the equatorial plane and the mean asymptotic direction. The direction of the anisotropy makes an angle of approximately 90° with the earth-sun line, the flow of excess particles overtaking the earth.

On the pressure dependence of the cosmic ray intensity recorded by the standard neutron monitor

Pressure coefficients have been determined for some standard neutron monitors at high latitudes for the years 1957-1959 with due regard to variations of primary origin. The following coefficients were obtained: (1) for Murchison Bay and Uppsala α = – 0.710 ± 0.006 per cent/mb; (2) for Resolute, Churchill and Ottawa α = – 0.725 ± 0.005 per cent/mb; (3) for Mawson and Mt. Wellington α = –0.736 ± 0.004 per cent/mb. The differences in a between the three groups of stations are certainly not due to a purely statistical scattering. They probably reflect dissimilarities in the neutron monitors and the pressure recording devices. As a by-product it has proved that for two stations above the latitude knee, the quotient between the pressure corrected daily neutron intensities is remarkably constant in time. It can thus be used as a sensitive indicator of changes in counting rate.

Atmospheric Effects on the Meson Intensity Recorded by the International Standard Cube at a High Latitude Station

Cosmic ray data and upper air data recorded at Murchison Bay during the IGY have been used to estimate the atmospheric effects on the sea level meson intensity recorded by the standard cube. The pressure corrected nucleonic intensity has been used to eliminate variations due to fluctuations in the primary intensity. It is shown that the regression equations proposed by Duperier and Dorman lead to practically identical corrections for the atmospheric effects. DOI: 10.1111/j.2153-3490.1961.tb00085.x

Atmospheric Effects on the Meson Intensity Recorded by the International Standard Cube at a High Latitude Station

Cosmic ray data and upper air data recorded at Murchison Bay during the IGY have been used to estimate the atmospheric effects on the sea level meson intensity recorded by the standard cube. The pressure corrected nucleonic intensity has been used to eliminate variations due to fluctuations in the primary intensity. It is shown that the regression equations proposed by Duperier and Dorman lead to practically identical corrections for the atmospheric effects. DOI: 10.1111/j.2153-3490.1961.tb00085.x

Standard Errors at Harmonic Analysis on Cosmic Ray Data

Standard errors of harmonic analysis have been calculated by three different methods. These methods are discussed and numerical calculations have been carried out from the results of harmonic analyses made on data from the neutron monitors in Uppsala and Murchison Bay. Periods covering from single days up to the mean of three years have been used for the comparison between the results. Although the standard error calculated according to the three methods include different types of variations, the results show good similarity. One of the methods also gives indications that only in some cases the addition of a second harmonic will be an improvement of the fit. DOI: 10.1111/j.2153-3490.1961.tb00070.x

Standard Errors at Harmonic Analysis on Cosmic Ray Data

Standard errors of harmonic analysis have been calculated by three different methods. These methods are discussed and numerical calculations have been carried out from the results of harmonic analyses made on data from the neutron monitors in Uppsala and Murchison Bay. Periods covering from single days up to the mean of three years have been used for the comparison between the results. Although the standard error calculated according to the three methods include different types of variations, the results show good similarity. One of the methods also gives indications that only in some cases the addition of a second harmonic will be an improvement of the fit.

Atmospheric Effects on the Meson Intensity Recorded by the International Standard Cube at a High Latitude Station

Cosmic ray data and upper air data recorded at Murchison Bay during the IGY have been used to estimate the atmospheric effects on the sea level meson intensity recorded by the standard cube. The pressure corrected nucleonic intensity has been used to eliminate variations due to fluctuations in the primary intensity. It is shown that the regression equations proposed by Duperier and Dorman lead to practically identical corrections for the atmospheric effects.

The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

In both places the monitors were of the standard pattern with 12 proportional counters filled with 97 per cent enriched B10F8. The first and second harmonics of the mean daily variation have been determined both for yearly periods and for each sun rotation period. Vector sum diagrams for the first harmonics in the latter case are given covering the intervals 31 Aug. 1956 to 15 Aug. 1959 for Uppsala and 13 Sept. 1957 to 29 April 1959 for Murchison Bay. In some instances a considerable phase shift has taken place from one sequence of sun rotation periods to another. These phase shifts were not contemporary at the two stations. The first harmonic of the 12-month means displays a high degree of constancy with only a small secular phase shift. The amplitudes of the second harmonics are very small. Conditions are especially favourable concerning the deviation in the earth’s magnetic field of the particles registered by the Murchison Bay monitor. Accordingly it has been possible to determine the direction of the anisotropy with a fairly good accuracy. The Murchison Bay records do not show any prominent phase shift with the Kp index. Concerning Uppsala, days with [Kp]max ≤ 1+ have a later time of maximum than other days. The influence of single days with an abnormal daily variation is discussed.