Assessment of alternative food resources of the lesser flamingo (phoeniconaias minor) in some Rift Valley saline lakes in Kenya and Tanzania
The saline lakes of Kenya and Tanzania are of high economic value and of great conservation and scientific value. They host >75% of the world's lesser flamingo population, which are a major income earner for these countries. The lesser flamingos iPhoeniconaias minor) are of scientific concern as they are near threatened. The analysis of the food resources that sustain the lesser flamingo populations and the ecology of alkaline saline ecosystems are useful in developing conservation strategies for these lakes and the flamingos. The study was carried out at saline lakes of the eastern rift valley within Kenya and Tanzania. The lakes were Bogoria, Nakuru, Elementeita, Oloidien, Sonachi and Natron. The study explored the diversity of the lesser flamingo food resources and their significance to the lake's ecology. Four categories of the food resources that are utilized by lesser flamingos are presented here. These include planktonic, sedimented,epipelic food resources and algae growing on wet mud. The planktonic food resource which occurred within the water column was mainly composed of Arthrospira spp. Sedimented A. fusiformis was observed at Lake Bogoria where it formed a film on the sediment in the shallow water. The epipelic food resource was mainly composed of benthic diatoms which grow on the water-sediment interface in shallow water where light penetrated to the sediment. The wet mud resource was also composed of diatoms growing on mud along the lake edges. The study confirmed that lesser flamingos are indeed the main primary consumers on the saline lakes. At a daily energy intake of 314 kcal for body maintenance, the species can consume> 92% of the cyanobacteria at Lake Bogoria, Lake Oloidien and Lake Sonachi. It was found that epipelic and wet mud diatoms significantly contribute to the lesser flamingo diet. These food resources supported >98% of the lesser flamingo's food requirement at Lake Natron's southern lagoon. This was also true for Lake Elementeita in August 2009 when the lake level was very low and the maximum wadeable depth was not more than 3 cm. Lesser flamingos cannot be sustained by cyanobacterial and algal food alone. Their diet is naturally enriched with 'animal' protein provided by protozoa and rotifer species. At least eight protozoan species were found with the commonest being Frontonia spp. which was found in all the lakes and dominant in some of the lakes. Some protozoan species were restricted to certain lakes, such as Amoeba spp. and Campanella spp. which only occurred in Lake Oloidien. Two rotifer species, Brachionus spp. and Hexarthra spp., were present in all ' lakes except in Lake Natron, where none was recorded. The lakes exhibited very high primary productivity for both planktonic and epipelic measurements. The highest net primary productivities were recorded at Lake Bogoria with 204.6 mg C m-2 hr' for planktonic cyanobacterial and 103.01 mg C m-2 hr' for sedimented Arthrospira. This is the first study to describe the primary productivity of the epipelic community of saline lakes and its contribution to the ecology of the rift valley lakes studied. At the shallow lakes, Lake Elementeita and Lake Natron, it contributed 100% to the primary production. The highest epipelic net primary productivity was recorded at Lake Elementeita with 73 mg C m-2 hr', while negative values of up to -33 mg C m-2 hr' were recorded for the suspended epipelic community at Lake Natron. The epipeJic and wet mud resources contribute greatly to the lesser flamingo diet than earlier thought and more so to the maintenance of the food chains on the saline lakes. The epipelic community is the main primary producer in the shallow lakes such as Natron.