Mass developments of a small sized ecotype of Arthrospira fusiformis in Lake Oloidien, Kenya, a new feeding ground for Lesser Flamingos in East Africa

Abstract

The Lesser Flamingos constantly commute between the soda lakes of East Africa in search of food. Their preferred food, the cyanobacterium Arthrospira fusiformis, usually establishes dense populations in saline–alkaline habitats. However, the algal food resources are not stable and crash unexpectedly from time to time. Hence any site that provides food in suitable quality and quantity makes a valuable contribution to the survival of these nearly endangered birds. This paper reports on the development of a new feeding ground for the Lesser Flamingos; Lake Oloidien, a former bay of the freshwater lake Naivasha. Phytoplankton succession and biomass, salinity and flamingo numbers were analysed over the period 2001–2013. As a result of a progressive increase in salinity to values of between 3 and 6 ppt, Oloidien has since 2006 hosted dense blooms of a small sized ecotype of A. fusiformis. Molecular phylogenetic analyses using the 16S–23S internal transcribed spacer (ITS) and partial sequences of the beta and alpha subunits including intergenic spacer (cpcBA–IGS) of the phycocyanin operon confirmed that a field clone and one isolated strain of Arthrospira from Lake Oloidien was similar to the strains in other soda lakes of Kenya. PCR–based results confirmed the non–toxic character of the isolated Arthrospira strain. The biomass of Arthrospira in the whole lake ranged from 236 to 301 t dry weight in the phase when more than 100,000 flamingos were present (2006–2012). Based on the biomass of Arthrospira present, the carrying capacity of Lake Oloidien was calculated to be 150,000–250,000 Lesser Flamingos. In the phase of low flamingo numbers (2013), the biomass of Arthrospira in the lake rose to a value of 922 t.