www.saltworkconsultants.com Salty MattersJohn Warren - Friday, May 23, 2016 Lake Nakuru flamingoes– Life’s response to feast and famine in schizohaline lacus- trine hydrologies The Flamingo Connection Nakuru, leaving enough pink carcases to spur an interna- tional newspaper to describe the lake as a “flamingo death An aviator once described Lake Nakuru as “a crucible of camp.” Two years prior, 43,800 of the birds had perished pink and crimson fire,” with a million flamingos painting at Tanzania’s Lake Manyara, the first major die-off docu- an astonishing band of colour that burst into pieces as the mented at that alkaline, soda-rich lake. Previous mass die- birds took flight (Figure 1). offs occurred at Lake Nakuru and two other Kenyan lakes Flamingo population levels in Lake Nakuru and any mass in 1993, 1995, and 1997, as well as at two lakes in Tanzania “die-offs” are popularly considered as indicators of the en- in 2002. At the same time, birds were gathering in places vironmental health of Nakuru and other lakes in the Af- they have never been documented before. Since 2006 there rican rift valley with significant flamingo populations. In have been additional population crashes at Nakuru and El- 2006, more than 30,000 of the birds were found dead at mentia (Table 1). Figure 1. Flamingo ock feeding on the edge of Lake Nakuru (full-size image can be downloaded from http://www.yannarthusber- trand2.org) Page 1 www.saltworkconsultants.com Date of crash Lake Reference where these birds dominate the macrofauna in 1971 Elmenteita Melack and Kilham 1974 some modern saline lakes, are described by Scott 1973 Nakuru Vareschi et al. 1981 et al. (2009, 2012). Ancient avian counterparts can 1973 (Mar- Sep) Bogoria Melack 1976 leave a characteristic set of trackways and trace 1973, 1974 Elmenteita Melack 1988 fossils (including nest mounds) that can be used 1974 Nakuru Vareschi 1982 1974, 1976 Elmenteita Tuite 1981 to refine mid-late Tertiary lacustrine depositional 1974 (Jan-Mar) Nakuru Tuite 2000 models (Melchor et al., 2012). Flamingo-like an- 2001 (Jun) Nakuru Ballot et al. 2004 cestors, which would give rise to modern ducks, 2001 (Oct) Bogoria Harper et al. 2003 even left traces in the shallow saline mudflats of 2002 (Sep) Elmenteita Ballot et al. 2004 Eocene soda lake sediments that define the saline 2004 Elmenteita Schargel and Odour 2008 portions of the trona/nahcolite-bearing sediments 2004 (Jul to Oct) Bogoria Schargel and Odour 2008 of the Green River formation in Utah (Figure 2). 2006 Bogoria Krienitz & Kotut 2010 2008 (Dec) - 2009 Nakuru Kaggwa etal. 2012 Two species of flamingo gather in huge numbers (Apr) & 2009 (Sep- in Lake Nakuru and a few other East African rift Oct) & 2013 lakes, namely, the greater and the lesser flamingo 2011 Elmenteita Krienitz at al., 2013 (Phoenicoptus ruber roseus and P. minor respec- 2012 Nakuru Krienitz et al. 2013 tively), with the lesser flamingo having character- Table 1. Biotal crashes in alkaline saline lakes of the African rift (from Schagerl et al., 2015) istic and spectacular pink-red colouration in their feathers. These bright pink waders feed and breed in mesohaline rift lake waters where cyanobacte- Flamingos numbers in Lake Nakuru are perhaps one of rial blooms can be so dense that a Secchi disc disappears the most visually impressive responses to episodic but very within a few centimetres of the lake’s water surface (War- high levels of organic productivity, driven by a well-adapt- ren, 1986, 2011). Lake Natron (Koeppen climate Aw), ed species feeding in a layered saline water body subject where trona is the dominant evaporite, is a major breeding to periodic salinity stress (Warren, 2011). The fluctuating ground for flamingos in East Africa and is the only regular richness of the lake’s flamingo population was dubbed the breeding site for the lesser flamingo in Africa (Simmons “flamingo connection” in a benchmark paper by Kirkland 1995). Lesser flamingos build nesting platforms on the and Evans (1981) that considered mesohaline evaporitic carbonates as hydrocarbon source rocks. Flamingo biology Flamingos (Aves, Phoenicopte- ridae) are an ancient lineage of long-legged, microphagous, colo- nial wading birds. Although popu- larly misperceived as tropical spe- cies, flamingo distribution is more closely tied to the great deserts of the world and to hypersaline lake sites, than it is to equatorial regions (Bildstein, 1993). Flamingos are filter feeders that thrive on halo- tolerant cyanobacterial blooms in mesohaline shallows of saline lakes around the world. This creates the context between flamingos, me- sohaline planktonic blooms, and saline lakes, well documented in Lake Nakuru by Vareschi (1982) A. B. and first noted in the geologi- cal literature in that benchmark Figure 2. Bird trackways in mudats of soda lakes - present and past. A. Flamingo tracks in the mudats of modern Lake Nakuru (fohuman footprint for scale). B. Kirkland and Evans paper. Sed- Flamingo-like trackways in the carbonate mudats of the Eocene Green River Group imentary textures and structures (Soldiers Hill locality - wedding ring for scale) associated with flamingo lifestyles, Page 2 www.saltworkconsultants.com b Sandai Wasages R. Lake Bogoria (Figure 3). Rift Valley Lakes Lake Nakuru Alluvial & colluvial deposits Loboi Landslips (megabreccias) Sands, silts, muds (deltaic) Lake Natron has the highest con- of the African Rift Njiro Sandai Organic muds & evaporites delta Volcanic rocks centration of breeding flamingos a Comorant Hydrothermal hot springs Point Quat. volcano Namarunu of any lake in East Africa. Both 2°N Rift lake Rift fault Emuruan- the greater and the lesser flamin- goglak Silali Lomudioc 4.4 go are found there, with the lesser Paka Ndolaita Korosi Maji ya flamingo outnumbering the great- Lake Bogoria Moto er by a hundred to one. Lesser fla- Lake Bogoria 0° Loburu mingos bred at Lake Natron in 9 Nyanza Rift 4.4 delta Lake Nakuru L. Elmenteita out of 14 years from 1954 to 1967. 4.3 Mawe Eburru L. Naivasha Baboon Cli Moto Olkaria Longonot But while the trona-rich nearby Suswa Lake Natron is an essential breed- ing site, it is not a focal feeding site 100 km Lake Magadi 3 3.9 Kipsirian R. Emsos 2°S 1 km 1.1 fan-delta for flamingos. Major feeding sites Parkimchai R. Lake Natron 1 in the Africa rift valley are Lakes A. Ol Doniyo B. C. 4 km 36°E 38°E Lengai Water depths in metres Makarlia Nderit Emsos Nakuru and Bogoria (formerly Figure 3. African rift valley A) Location of lakes and Quaternary volcanoes in the African rift valley centred Lake Hannington) in Kenya and on Lake Nakuru and Lake Bogoria. B) Lake Nakuru bathymetry (Dec 1979) and subsequent strandzone entrain waters that are mesohaline changes. Solid isopleths are actual shorelines at dierent lake levels over a 20 year period; from outer to inner are December 1979, January 1969, January 1967 and January 1961. Dashed isopleths are based on with an abundance of halotolerant soundings taken in December, 1971. Two sewage plants are located at a and b (after Vareschi, 1978) C) cyanobacteria, dominated by Ar- Surface geology of Lake Bogoria (after McCall, 2010). throspira (Schagerl et al., 2015). Lake Nakuru is a mesohaline soda trona pavement in the more central parts of the lake. These lake with a pH ≈ 10.5 and a typi- spectacular birds not only feed in saline waters, they can cal annual salinity range of 15-45‰, nearby lake Bogoria choose to build nest mounds on evaporite pavements! is somewhat larger, also an alkaline soda lake, with some- what higher salinities. The Lake Nakuru depression mea- Worldwide, only six sites are used for breeding by the lesser sures some 6.5 km by 10 km, with a water covered area of flamingos: Lake Natron (Tanzania), Etosha Pan (Namib- some 5-45 km,2 experiencing an annual pan evaporation ia), Makgadikgadi-Pan (Botswana), Kamfers Dam (South rate of 1500 mm beneath a Cfb Köppen climate (Figure Africa), as well as two pans in the “Little Rann of Kachchh” 3b; Vareschi,1982; Krienitz and Kotut, 2010). It contains a (India). Recent estimates of lesser flamingos at the main eutrophic bottom water mass in the lake centre, with ther- distribution areas are as follows: 1.5–2.5 million in eastern mally stratified water column that can be up to 4.5 metres Africa; 390,000 in northwestern India; 55,000-65,000 in deep. The Lake Bogoria’ water mass is up to 4 km wide, southwestern Africa; and 15,000–25,000 in western Af- some 17 km long with thermally stratified eutrophic wa- rica. The highest population densities occur in Kenya (1.5 ters up to 10 m deep. It lies beneath a Cfb climate with a million) and Tanzania (600,000) (Childress et al. 2008). pan evaporation of 2600 mm. It is fed by a combination of Lesser flamingos are well adapted to the harsh con- 4 ditions associated with liv- 3.5 Mean annual rainfall = 750 mm Nakuru water depth ing and breeding in hyper- (peaks in Nov-Dec and Apr.-May 1930-1999 saline alkaline conditions. 3 Mean annual evaporation = 1800 mm Worldwide, they follow an 2.5 Lake elevation 1759 m.s.l itinerant lifestyle, ranging Mean water depth 2.5m, maximum 4.5m across their distribution ar- 2 eas in search of saline wa- 1.5 ter bodies with appropriate (m) Lake level 1 cyanobacterial blooms. In the east African rift the no data flocks can travel up to 200 0 no data km a day between feeding 1930 1931 1932 1933 1993 1994 1995 1996 1997 1998 1999 and breeding sites, which 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 YEAR are generally at geograph- 1980-1992 1934-1949 ically separate locations Figure 4.