Lake Turkana

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Lake Turkana
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I Will Discuss

• Data on Lake Turkana
• Wildlife and Fish that inhabit the area
• Issues of the region
• Study on mercury levels in fish

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Introduction

• Formerly known as Lake Rudolf
• Located in the Great Rift Valley of Eastern
  Africa in the country of Kenya
• The largest permanent desert lake in the world
• Also the largest alkaline lake in the world

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Data

• Volume 237 km3
• Surface Area 7,500 km2
• Mean depth 31 m
• Maximum depth 114 m
• Origin Tectonic
• The primary inflow sources are the Omo River,
  Turkwel River, and Kerio River
• It is a terminal lake, meaning it has no outlets
  of water, other than evaporation
• It is monomictic, mixing only once a year

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Aerial view of Lake Turkana
Crater at the southern end of Lake Turkana
Cinder Cone at Lake Turkana
Dunes in the Rift Valley south of Lake Turkana
Lake Turkana is surrounded by rocky lava shores
on the East and South, while dunes and flats are
located on the West and North. There are 3
islands North, Central, and South Islands.
Central Island is an active volcano.
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Land Cover
Percent Forest Cover 11.9 Percent
Grassland/Savanna/Shrubland 50.2 Percent
Wetlands 5.9 Percent Cropland 20.8 Percent
Irrigated Cropland 0.3 Percent Dryland Area
42.4 Percent Urban and Industrial Area
0.1 Percent Loss of Original Forest Cover 59.6
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Population
Basin Area (sq. km.) 209,096 Average Population
Density (people per sq. km.) 61 Number of Large
Cities (gt100,000 people) 0 Water Supply per
Person (1995)(m3/year) 4,450 Degree of river
fragmentation - Number of Dams (gt15m high) in
Basin 1 Number of Dams (gt150m high) in Basin
0 Number of Dams (gt60m high) under Construction
0 Number of Dams (gt15m high) on Main Stem of
River 0 Number of Dams (gt150m high) on Main Stem
of River 0
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Biodiversity
Number of Fish Species 47 Number of Fish
Endemics 17 Number of Amphibian Species
51 Number of Wetland-Dependent Important
Bird Areas 7 Number of Endemic Bird Areas
3 Percent Protected Area 8.6
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Wildlife

• Turkana's fish include the Nile perch reaching
  weights of over 800 kilograms (360 pounds).
  Tilapia and tigerfish are also common.
• It also has more than its fair share of Nile
  crocodiles, they breed on Central Island.
• Birds in this area include the Little Stint, the
  Wood and Common Sandpipers, the African skimmer,
  and the Greater flamingo.
• Grevys zebra and oryx (antelope) are some grazers
  in this region.

Nile Perch
Tilapia
Nile Crocodile
Little Stint
Wood Sandpiper
Common Sandpiper
Greater Flamingo
Grevys Zebra
oryx
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Issues

• The main problems affecting Turkana are
• Drought
• Famine
• Poverty

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Selected Publication

• Titled Mercury in fish from three rift valley
  lakes (Turkana, Naivasha, and Baringo by
  Campbell.
• Total mercury (THg) concentrations were measured
  for various fish species in each lake.
• They measured each fish and cut a 10cm2 section
  of muscle tissue for measuring the mercury
  concentration.
• Concentrations were measured on a dry weight
  basis and were then changed to a wet-weight
  basis, assuming 80 water.

METHODS
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Mercury

• When mercury reaches an aquatic environment, it
  can be transformed into methylmercury.
  Methylmercury is very toxic, much more toxic than
  elemental mercury, it dissolves easily in water,
  and accumulates.
• The total mercury concentrations in fish from are
  dependent on which trophic level they are in and
  the amount of THg available for uptake.
• If a fish has a high trophic position and they
  are piscivorous, they have a higher chance of
  having high levels of mercury present, due to the
  concept of bioaccumulation.
• Bioaccumulation is the accumulation of a
  substance, such as a toxic chemical, in various
  tissues of a living organism. It takes place
  within an organism when the rate of uptake of a
  substance is greater than the rate of excretion
  of that substance.

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RESULTS
Campbell, 2003
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Fig. 1 Total mercury concentrations versus total
length for each fish species Dashed lines
represent the European Economic Community (EEC)
marketing limit of 500ng g-1 Solid lines
represent the World Health Organization (WHO)
limit of 200ng g-1
-In most African lakes, low THg levels are
normal, and this study demonstrated just that.
-However, one fish species found in Lake Turkana
had a high level of total mercury, (Hydrocynus
forskahlii). -The total level of mercury for
this species was 636ng g-1 which exceeds the
World Health Organizations marketing limit of
200ng g-1.
Campbell, 2003
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Hydrocynus forskahlii
(Tiger Fish)

• Silver with a long and slender profile. Tail fin
  forked with bright red color.
• An open water predator often found near the
  surface.
• Forms shoals and feed on other fish. They are
  also cannibalistic.

Source http//www.fishbase.org/summary/SpeciesSum
mary.php?id4496
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CONCLUSIONS

• The high mercury concentrations in Hydrocynus
  forskahlii deserve a closer examination, it is
  likely due to the tigerfishs high tropic
  position and highly piscivorous diet.
• With the exception of Hydrocynus forskahlii from
  Lake Turkana, total mercury (THg) concentrations
  in fish from Kenyan lakes do not pose an
  unacceptable risk to human consumers.

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Summary

• Lake Turkana is located in the Great Rift Valley
  of Eastern Africa in Kenya.
• It is the largest permanent desert lake in the
  world.
• Known as the Jade Sea due to algae that rise to
  the waters surface.
• It is a terminal lake which means it has no
  outlets of water, other than evaporation.
• The areas population is not very high.
• The lake is home to more than 40 species of fish,
  Nile crocodiles, and many water birds.
• There are currently no major management issues
  with the lake, but there are problems affecting
  the natives such as drought, famine, and poverty.
• Total mercury concentrations in most Kenyan fish
  species are not toxic, but more studies need to
  be made on the tigerfish.