The benthic and weed-bed faunas of Lake Awasa (Rift Valley, Ethiopia)

Kibret, Tilahun; Harrison, A. D.

doi:10.1007/bf00006053

Cited by 23 publications

(17 citation statements)

References 15 publications

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“…Most Orthocladiinae are dependent on highly oxygenated water (Petr 1970a), and in tropical regions comprised a large proportion of chironomids from cool, lotic habitats (63%, n ϭ 16, Harrison and Hynes 1988, rivers in highland Ethiopia; 53%, n ϭ 45, Lehmann 1979, rivers in eastern, highland DR Congo), perhaps because oxygen is less soluble in warmer water, and higher temperatures speed up decomposition of organic material which also depletes oxygen (Eggermont and Verschuren 2003b). Consistent with this interpretation, the proportion of orthocladiines was lower in lower altitude rivers and streams (29%, n ϭ 38, Lehmann 1981, rivers in central DR Congo) and in highland lakes (21% n ϭ 32, Verschuren 1997, Lake Naivasha, Kenya); 15%, n ϭ 27, Kibret and Harrison 1989, Lake Awasa, Ethiopia). Although they acknowledge that some of their sub-fossil types may have washed in with sediment from feeder streams and rivers, Eggermont and Verschuren (2003b) argue that the consistently strong wave action characteristic of the large Rift Valley lakes may create the conditions for oxygenation usually encountered in fast moving streams and rivers and, by extension, an environment favorable to at least some orthocladiine species.…”

Section: Notes On the Chironomid Taxa From Aquatic Plantssupporting

confidence: 77%

“…In most of the other studies, chironomid species richness was relatively low. In highland Ethiopia, Kibret and Harrison (1989) recorded only 13 chironomid species from aquatic plants in Lake Awasa, but these represented nearly half of the 27 total species collected at light or by sweep net. Two other studies focused on unstable lake systems; Kariba in Zimbabwe, a manmade, recently-dammed lake (MacLachlan 1969a), and the shallow, intermittently saline Lake Chilwa in Malawi (MacLachlan 1975).…”

Section: Discussionmentioning

confidence: 98%

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The Diversity of Chironomidae (Diptera) Associated withHydrilla verticillata(Alismatales: Hydrocharitaceae) and Other Aquatic Macrophytes in Lake Tanganyika, Burundi

Copeland

Nkubaye

Nzigidahera

et al. 2012

Annals of the Entomological Society of America

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To search for potential biological control agents of the aquatic weed, Hydrilla verticillata (L.f.) Royle, emerging chironomid adults were collected from aquatic macrophytes sampled between 2007 and 2009 from near shore sites in Lake Tanganyika, Burundi. Initial surveys identified H. verticillata populations at all sampled locations between Bujumbura and Nyanza Lac. Twenty-six (26) species of Chironomidae emerged from collections of four plant species; Hydrilla, Ceratophyllum demersum variety apiculatum (Cham.) Asch., Potamogeton schweinfurthii A.Benn., and Vallisneria spiralis f. aethiopica (Fenzl) T.Durand and Schinz. Twenty-four of the chironomid species were new country records, but none of them represented undescribed species. Dicrotendipes fusconotatus (Kieffer) dominated the chironomid community, comprising 82% of 32,090 reared adults. The six most common species contributed over 96% of the total midge fauna. Most species were uncommon or rare; nine species were represented by 10 or fewer specimens. A species accumulation curve for the 25 chironomid species reared from Hydrilla suggested that our sampling completely describes the community associated with this plant in northern Lake Tanganyika. Quantitative β-diversity values indicated that chironomid communities of the two Hydrocharitaceae species, Hydrilla and Vallisneria, were most similar to each other, even though they have very different growth forms. Chironomids also emerged in greater numbers from the two Hydrocharitaceae than from the other plants. No chironomid species, including Polypedilum wittei Freeman and Polypedilum dewulfi Goetghebuer, two species formerly considered for possible biological control of Hydrilla, were specific to that plant. Polypedilum species emerged from all sampled aquatic macrophytes. No chironomid-caused damage was seen on Hydrilla. African Chironomidae do not appear to be suitable candidates for biological control of Hydrilla.

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Section: Notes On the Chironomid Taxa From Aquatic Plantssupporting

confidence: 77%

Section: Discussionmentioning

confidence: 98%

The Diversity of Chironomidae (Diptera) Associated withHydrilla verticillata(Alismatales: Hydrocharitaceae) and Other Aquatic Macrophytes in Lake Tanganyika, Burundi

Copeland

Nkubaye

Nzigidahera

et al. 2012

Annals of the Entomological Society of America

View full text Add to dashboard Cite

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“…The silt content in the water is relatively low because the large swampy area to the east on the Tikur Wuha River acts as an efficient settling area for silt coming from the higher hills and mountains of the eastern escarpment of the Rift Valley (Kibret and Harrison, 1989).…”

Section: Environmental Conditionsmentioning

confidence: 99%

The composition of fish communities of nine Ethiopian lakes along a north-south gradient: threats and possible solutions

et al. 2012

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Fish populations of nine Ethiopian freshwater lakes were quantitatively sampled with a standardized protocol, using multi-mesh gill nets. In total, 27 species were identified, but only 14 species were common. Based on the common species, the fish communities showed large differences in their species composition, except for Lake Abaya and Lake Chamo which were similar. Most fish species were observed in only one or two lakes. Compared with the information reported in literature the present study generally underestimated the species richness. The empirical model of Amarasinghe and Welcomme (2002) for African lakes was used to estimate fish species richness, which was compared with species presence reported in literature. Biodiversity in the two northern highland lakes is low, but not lower than the model estimate. Lake Tana has a high biodiversity which is close to what is estimated by the model, but three Rift Valley lakes have low biodiversity, lower than estimated by the model. There are also strong indications for the Rift Valley lakes that species richness was higher in the past because the species richness reported in the older literature was generally much higher than those observed by us in the present study and those reported in the more recent literature. Threats like overfishing, high sediment load and degradation of habitats were identified. It is recommended that Ethiopia should develop guidelines for fishery legislation and implement it through an enforcement agency. Moreover, catchments management should be practiced to save the water bodies and their fish communities.

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“…Destratification is initiated in June by a decrease in solar radiation and cool rains (Elizabeth Kebede, 1987). Wind varies on both a diel and seasonal basis in Lake Awasa (Elizabeth Kebede, 1987;Tilahun Kibret & Harrison, 1989), and perhaps a combination of cool temperatures and high rainfall are critical in inducing lake mixing during May to June (Elizabeth Kebede, 1987). The lake lies in a closed basin with a total area of 1250 km 2 .…”

Section: Study Site: Lake Awasamentioning

confidence: 99%

Seasonality and abundance of some dominant crustacean zooplankton in Lake Awasa, a tropical rift valley lake in Ethiopia

Mengestou

Fernando

1991

Hydrobiologia

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The zooplankton of a Rift Valley lake in Ethiopia, Awasa, was sampled at 3 stations for 2 years (1986 and 1987) concurrently with various meteorological and limnological measurements. The spatial and temporal variation in abundance of some numerically dominant crustaceans, Mesocyclops aequatorialis similis (Copepoda), Thermocyclops consimilis (Copepoda) and Diaphanosoma excisum (Cladocera) is discussed. Temporal (months, sampling dates) rather than spatial (station) variability accounts for more than 50 % of the total variance in zooplankton abundance but horizontal patchiness exists during periods of high zooplankton density. Sampling errors were generally low, except for counts of cyclopoid nauplii (subsampling) and Diaphanosoma (inter-replicate variance).Zooplankton showed distinct seasonality associated with the mixing cycle of the lake. Total numbers increased to more than 200000 m-3 during the unstratified period (July to September). Low numbers were evident during stratification (February to May) when zooplankton numbers did not exceed 15000 m -3 . Individual zooplankton species and age classes showed variable seasonal amplitudes, ranging from 6.4 (nauplius 3) to 44.8 (copepodite 3 of Mesocyclops). We discuss some possible causes for zooplankton seasonality in Lake Awasa, and also review zooplankton seasonal cycles in other tropical lakes, especially African ones.

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The benthic and weed-bed faunas of Lake Awasa (Rift Valley, Ethiopia)

Cited by 23 publications

References 15 publications

The Diversity of Chironomidae (Diptera) Associated withHydrilla verticillata(Alismatales: Hydrocharitaceae) and Other Aquatic Macrophytes in Lake Tanganyika, Burundi

The Diversity of Chironomidae (Diptera) Associated withHydrilla verticillata(Alismatales: Hydrocharitaceae) and Other Aquatic Macrophytes in Lake Tanganyika, Burundi

The composition of fish communities of nine Ethiopian lakes along a north-south gradient: threats and possible solutions

Seasonality and abundance of some dominant crustacean zooplankton in Lake Awasa, a tropical rift valley lake in Ethiopia

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