Sudden flamingo deaths in Kenyan Rift Valley lakes

Nadja Straubinger‐Gansberger,Martin Gruber,Steve Omondi Oduor,Michael Schagerl,Linda Lawton,Mary N Kaggwa

doi:10.2981/wlb.00018

Abstract

The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die‐offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross‐checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die‐offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composition or bird diseases played a key role in the observed flamingo die‐offs.

Highlights

The cyanobacterium Arthrospira fusiformis is a well-known dietary supplement because of its high content of essential amino acids and fatty acids, vitamins, minerals and antioxidant functions (Belay et al 1993, Capelli and Cysewski 2010)
We focused our research on the Kenyan soda lakes Bogoria and Nakuru, where A. fusiformis is the main food source for lesser flamingos Phoeniconaias minor (Vareschi 1978)
While some scientists proposed a link between Microcystis and flamingo die-offs (Ndetei and Muhandiki 2005, Stewart et al 2008, Githaiga 2003), others challenged the growth of Microcystis in such alkaline-saline environments (Kotut and Krienitz 2011)

Summary

Introduction

The cyanobacterium Arthrospira fusiformis is a well-known dietary supplement because of its high content of essential amino acids and fatty acids, vitamins, minerals and antioxidant functions (Belay et al 1993, Capelli and Cysewski 2010). Die-offs of lesser flamingos at some East African rift valley lakes have attracted researchers interests for four decades (Table 1). The ultimate causes for the die-offs are still speculative in most cases, because prompt action is needed to collect material As this phenomenon usually occurs in remote areas and carcasses are removed by scavengers within a few days, this is rarely possible. During our weekly sampling intervals from July 2008 to November 2009, we had the opportunity to screen the lake water for cyanotoxins. This approach was based on reports of toxin-producing cyanobacteria in the hot springs around L. Metcalf et al (2013) detected neurotoxic amino acids in flamingo feathers, which were collected during a sudden mass mortality in 2003, so cyanotoxins must not be precluded as a possible explanation for the recent die-offs

Methods

Results

Conclusion