Research on resource transfer across ecosystem boundaries (i.e. allochthonous material; a subsidy) has been recognised since the 1920s and allochthonous inputs have been a part of food web theory since its inception. Nonetheless, only in recent decades have subsidies between ecosystems become a focus of larger scale food web studies.
Measures of subsidies have typically been restricted to studies of either marine or freshwater ecosystems, whereas linkage between saline lakes and their catchments has been largely overlooked. Saline lakes are still perceived as being of less value, in terms of ecosystem goods and services, than other ecosystems.
However, although saline lakes usually contain rather ‘simple’ communities, they are very productive and in addition to which are typically found in arid landscapes where the terrestrial ecosystem is depauperate. Thus, such lakes provide an oasis in terms of food resources which the terrestrial ecosystem can exploit providing there is a vector of transfer.
My aim is to further our knowledge of resource subsidy between saline lakes and their arid catchment and consider such linkage with respect to climate change. I have three main objectives:
- To investigate the relative strength of aquatic subsidy to terrestrial consumers, both spatially and temporally.
- To infer historical conditions using a salinity transfer function applied to the chironomid larval assemblages found in the lake sediment palaeo-records.
- To link the strength of aquatic subsidy to salinity and in turn to climate conditions. These data can then be used to forecast the likely effects of anthropogenic climate change on the strength of subsidy.
The Site: Lake Bogoria
Lake Bogoria is situated in the East African Rift Valley System (EARS), approximately 25 Km north of the equator in Kenya. It is a hyper-saline lake reaching ˜40 ‰ (conductivity › 64 mS cm−1)
It has three basins that have different physical characteristics which may create different chemical and biological characteristics; I will exploit such attributes for a spatial investigation of subsidy. There are also at least two vectors of subsidy: a bi-monthly pulse of emerging chironomids; and a continuous supply of flamingo feathers, which allows me to investigate and compare temporal patterns of subsidy.