Linkage between saline lakes and their catchments under climate change

There is a general perception that saline lakes are of less value than freshwaters yet they are of almost equal volume on a global scale. Climatic effects on saline lakes are disproportionately large because of their typically shallow depth. The extreme chemical conditions of saline lakes often promote specialised communities comprising few species but those that thrive are highly productive. Catchments surrounding saline lakes are typically arid and thus depauperate in terrestrial production but may rely heavily on aquatic subsidies e.g. emergent insects. Thus, climate change impacts on saline lakes via fluctuating volume and salinity may have subsequent, strong effects on the wider catchment. Lake Bogoria is a Kenyan soda lake with a simple aquatic community dominated by one alga Arthrospira and one chironomid Paratendipes (which has monthly emergences), and its three distinct basins have different environmental characteristics resulting in different densities of organisms. Large numbers of birds, particularly flamingo, rely on the former, and other insectivorous bird species, as well as terrestrial invertebrates of conservation value, rely on the latter. We will use Lake Bogoria as a model system to address 3 objectives. 1 To determine what has happened in the past we will take cores from the 3 distinct basins to hindcast past environmental conditions by analysing chironomid assemblage diversity and head capsule densities. Our assumption - changes in lake volume over time will have impacted upon salinity and caused cascade effects on algal and chironomid communities. 2 To assess how aquatic subsidies impact on terrestrial consumers we will measure the 'strength' of subsidy from each basin which typically has a different chironomid density as a measure of linkage between the lake and its catchment, hypothesising that the strength of subsidy will directly reflect larval density. This is essentially a 'space for time' substitution using the different larval densities as a proxy for environmental condition with respect to objective 1. 3 To forecast impacts of predicted climate change on such linkages we will combine the data from objectives 1 & 2 with climate models. Our prediction - lake volume reduction will weaken linkage from the lake to the catchment in the future. This project falls within the remit of NERC science themes in the area of land-surface (terrestrial and freshwater) research. Achieving these three objectives will close a significant gap in our knowledge of the importance of saline lakes with respect to their arid-land catchments.