Abstract:
The food web of the saline–alkaline lakes
of East Africa is characterised by a unique interaction
between the Lesser Flamingos as consumer birds
and the cyanobacterium Arthrospira fusiformis as the
primary producer. However, this interaction is disturbed
frequently by alterations of the phytoplankton
community. During the period 2001–2012, species of
the cyanobacteria Anabaenopsis and Cyanospira were
observed in four soda lakes of the African Rift Valley
and compared to the entire phytoplankton biomass and
composition. Their morphology was highly variable.
Each species preferred a distinct range of salinity:
C. capsulata 30–40 ppt, C. rippkae 25–35 ppt, A. arnoldii
and A. abijatae 10–30 ppt, and A. elenkinii 0–15
ppt. Occasional dominance of Anabaenopsis and
Cyanospira in the lakes investigated shows that
members of these genera are serious competitors of
A. fusiformis, the main food for Lesser Flamingos.
Furthermore, mass developments of C. capsulata
adversely affected food uptake by the flamingos at
Lake Bogoria because they formed mucilaginous
colonies that clogged the food filter system. From
field samples of the three lakes, uncultured Anabaenopsis
and Cyanospira spp. clones were obtained and
subjected to phylogenetic analyses. The 16S rRNA
gene sequencing data put into doubt the differentiation
of Anabaenopsis and Cyanospira into separate genera
as recently suggested.
