Those that remained have been well preserved due to lack of oxygen and the depth of the lake, and can be seen by divers with both a permit and the skill required to reach such depths.ДЄlso said to be in the lake is a safe with six million gold marks, though it has not been seen to date. Some of these were recovered and can be seen at Tsumeb museum nearby. In 1915 - during world war I, the lake was a dumping ground for German weaponry, before surrendering to advancing British soldiers. It is almost circular in shape, with a diameter of about 104 m and its sides are so steep that a rope ladder is necessary to get in or out - especially when water levels fall.ДЄs you dive deeper, its diameter increases making it possible to swim underneath the rocky crater rim. The deepest recorded depth exceeds 140 m, though the lake is said to have a cave system underneath. Its name comes from the Herero word for 'deep hole' and no exploration to date has been able to find its bottom. D.Д«iodiversity in Sub-Saharan Africa and its islands: Conservation, management and sustainable use, Occasional Papers of the IUCN Species Survival Commission No.The smaller of only two permanent natural lakes in namibia, formed after the collapse of a Karst cave. 'Diversity and distribution of freshwater fishes in East and Southern Africa'ДЄnnals of the Royal Central Africa Museum (Zoology) 275 Journal of the Namibia Scientific Society 42ДЄ complete guide to the freshwater fishes of Southern Africa 'The status of fishes from sinkholes and caves in Namibia' South African National Scientific Programs Report 40 Aikab hemicenote, and other karst phenomena in the Etosha National Park' Biospeleology, ecology, and conservation of Dragon's Breath Cave' 'Conservation aspects of karst waters in Namibia' 'Species richness and conservation of Namibian freshwater macro-invertebrates, fish and amphibians' Namibian National Biodiversity Task Force.Д¬urtis, B., Roberts, K. Irish (1991) recommends the collection of information on the cryptic fauna of springs, the stygobiotic fauna (aquatic species living permanently underground in the dark zone of caves) of unsampled subterranean waters, and more detailed geohydrological information. These studies should determine the status of isolated populations and the effects that water abstraction has had on these systems. Several of the caves and their lakes within this ecoregion have been mapped and explored (Irish 1991, 1992 Marais & Irish 1997), although further studies are warranted. The lengthy period of isolation that the Karstveld fauna have experienced, as well as the particularly stable conditions within the lakes, have led to the evolution of a number of endemic species (Skelton 1987, 1990).ДЇair. The biogeographic affinities of the Karstveld fauna are Zambezian, and a number of taxa are shared with the Okavango, Cunene, and Zambezi Rivers. The boundaries of this ecoregion are defined by the extent of Karstveld, the extensive dolomite and limestone formations located to the southeast and east of the Etosha Pan in Namibia. The endangered polychromatic Otjikoto tilapia, Tilapia guinasana, is endemic to Lake Otjikoto (Skelton 1987 Irish 1992). The species is endangered and may have a population of less than 200 individuals (Irish 1992 Barnard 1998). This depigmented fish has reduced eyes and feeds on bat droppings, animal carcasses, and insects that fall into the water from overhead (Skelton 1994).

Mountainous savanna dominates the vegetation in the Karstveld ecoregion.Д¬larias cavernicola, endemic to Aigamas Cave, is southern AfricaвЂ™s only true cavefish (Skelton 1993). The sinkhole lakes are moderately clear and water temperatures average 19-27вЊ (Stuart et al. Cenotes are water-filled sinkholes, and hemi-cenotes are cenotes with openings that are small relative to the size of the water surface below ground. Cave lakes occur in laterally developed horizontal cave systems. The Karstveld groundwater system consists of a number of distinct water bodies including subterranean cave lakes, cenotes, and hemi-cenotes. The karstic waters are permanent and mainly underground (Irish 1992 Barnard 1998 Curtis et al. This process forms water-filled underground caves, and sinkholes result when the roof of a cave collapses. Sinkhole lakes and caves are karst features characteristic of dolomite that are formed as water penetrates cracks in the dolomite and leaches away the rock. The area covers the Otavi Mountains and continues westward through the northern parts of Outjo District as far as Otjovasandu (Irish 1992).

The Karstveld is the name given to extensive dolomite and limestone formations located to the southeast and east of the Etosha Pan in Namibia. The Karstveld sinkhole lakes and caves are distinctive subterranean habitats, supporting a substantial number of endemic aquatic species within several taxonomic groups.

Lake otjikoto namibia africa