Lake Bermin

Lake Bermin (sometimes spelled Bemin or Beme) is a small lake in the volcanic chain in the Southwest Region of Cameroon. It is a volcanic lake with a diameter of about 700 m (2,300 ft)^[3] and a crater rim that rises to a height of about 46 m (150 ft).^[1] This highly isolated lake is roughly circular in shape, lacks an inflow, but has an outflow into the Cross River system.^[4]

Lake Bermin
Lake Bermin Show map of Cameroon Lake Bermin Show map of Africa
Coordinates	5°09′30″N 9°38′0″E / 5.15833°N 9.63333°E / 5.15833; 9.63333Coordinates: 5°09′30″N 9°38′0″E / 5.15833°N 9.63333°E / 5.15833; 9.63333
Lake type	Volcanic crater lake
Primary inflows	None
Primary outflows	Cross River system
Basin countries	Cameroon
Surface area	144 acres (58 ha)^[1] or 280 acres (110 ha)^[2]
Max. depth	15 m (49 ft)^[2]

Biology

Despite its very small size, it supports nine endemic species of coptodonine cichlid fishes (C. bakossiorum, C. bemini, C. bythobates, C. flava, C. gutturosa, C. imbriferna, C. snyderae, C. spongotroktis, and C. thysi).^[1] This number of endemic fishes per area is the highest recorded anywhere.^[5] Early genetic evidence suggested that these probably were the result of sympatric speciation.^[4] Later studies indicate a level of secondary gene flow between the Bermin cichlids and Cross River C. guineensis, although it is unclear if this facilitated speciation among the former group.^[3] They are a relatively recent radiation.^[6] They are quite similar in their general appearance and morphology but vary greatly in feeding behavior, including specialists like C. spongotroktis that eat pieces of the large sponges that grow in the lake.^[6] The Lake Bermin cichlids are small fish, none surpassing 14 cm (5.5 in) in standard length.^[7] At up to 5 cm (2 in) in standard length,^[7] C. snyderae is the smallest known tilapia.^[6]

All the Bermin cichlids are critically endangered by pollution and sedimentation from human activities, and potentially also by large emissions of carbon dioxide (CO₂) from the lake's bottom (compare Lake Nyos),^[8][9][10] although Bermin is too shallow to contain very high amounts of this gas.^[2]

See also

• Lake Barombi Koto
• Lake Barombi Mbo
• Lake Dissoni
• Lake Ejagham
• Lake Oku

References

1. Dickinson, C. (2005). The Tilapia of Lake Bernin, Cameroon. 2012-03-13 at the Wayback Machine Modern Aquarium -Greater City A.S. (NY): 15–16
2. Freeth, S.J.; C.O. Ofoegbu; and K.M. Onuoha (1992). Natural Hazards in West and Central Africa, pp. 50–52. ISBN 978-3-663-05239-5
3. Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422. doi:10.1111/evo.12674
4. Schliewen, U.K., Tautz, D., and Pääbo, S. (1994). Sympatric speciation suggested by monophyly of crater lake cichlids. Nature 368(6472): 629–632.
5. Freshwater Ecoregions of the World (2008). Western Equatorial Crater Lakes. 2011-10-05 at the Wayback Machine
6. Thieme, M.L.; R. Abell; N. Burgess; B. Lehner; E. Dinerstein; and D. Olson (2005). Freshwater Ecoregions of Africa and Madagascar: A Conservation Assessment, pp. 58–60. Island Press. ISBN 1-55963-365-4
7. Froese, Rainer and Pauly, Daniel, eds. (2018). Species of Coptodon in FishBase. June 2018 version.
8. Moelants, T. (2010). "Tilapia bakossiorum". IUCN Red List of Threatened Species. 2010: e.T21888A9335381. doi:10.2305/IUCN.UK.2010-3.RLTS.T21888A9335381.en. Retrieved 25 December 2017.
9. Moelants, T. (2010). "Tilapia gutturosa". IUCN Red List of Threatened Species. 2010: e.T21892A9336298. doi:10.2305/IUCN.UK.2010-3.RLTS.T21892A9336298.en. Retrieved 25 December 2017.
10. Moelants, T. (2010). "Tilapia thysi". IUCN Red List of Threatened Species. 2010: e.T21896A9337065. doi:10.2305/IUCN.UK.2010-3.RLTS.T21896A9337065.en. Retrieved 25 December 2017.