Interactions between glacier loss, proglacial lake development and downstream river ecosystems

Glaciers cover ~10% of Earth’s surface, but they are losing mass at unprecedented rates worldwide and are expected to disappear in many places by the end of the century. Glacier retreat is already causing major changes in downstream aquatic systems such as increasing water temperatures, reduced flows and altered sediment fluxes (Milner et al., 2017). These changes are driving habitat fragmentation and species redistributions, population extinction threats for fragile cold-adapted species and modifying the ecosystem services that society depends upon. Yet, major gaps still remain in our understanding of how aquatic biodiversity responds to glacier loss (IPCC, 2019) – for example, knowledge is geographically biased, focuses mainly on biological groups such as invertebrates, and we lack a detailed understanding of how covariates such as geology or river morphology influence biodiversity alongside glacier influences.

Cold, turbulent, sediment-laden glacier-fed rivers were historically seen as inhospitable to life but they are now known to host diverse communities of specialised cold-adapted fungi, bacteria, algae and invertebrates that interact in complex food webs. Recently we have demonstrated that, for aquatic invertebrates at least, the processes shaping biodiversity in glacier-fed rivers may be globally consistent after we account for systematic regional effects of latitude (Brown et al., 2018). However, our datasets show clear variance in biodiversity responses for a given level of glacier loss, with the development of proglacial lakes known to be a major modifier of thermal, sediment and flow regimes (Hieber et al., 2001; Maiolini et al., 2006). As glaciers retreat worldwide, large numbers of new mountain lakes are forming, but most research has focused on emerging risks for downstream human populations (e.g. Taylor et al., 2023). Directed studies are needed to understand how ecosystems can be expected to respond to future changes in glacier runoff in river systems with lakes compared to those without. Additionally, most previous glacier river studies have focused on invertebrates with far less understanding of extremely biodiverse groups such as bacteria, fungi and algae (Fell et al., 2017). As a consequence, the roles of these biological groups in mountain biogeochemical cycles, water quality maintenance, and aquatic and riparian food webs are still to be determined.

This project will focus on alpine river systems around the world, merging existing datasets with those collected from targeted campaigns. New field surveys will be developed as part of the PhD to study aquatic biodiversity along space-for-time gradients of glacier retreat, whilst also re-sampling a limited number of sites from previous studies to observe temporal changes directly. These studies are likely to be undertaken in either the Himalayas or the European Alps. A key focus will be on benthic invertebrates as they are the most widely studied group with good taxonomic expertise/existing datasets, but there are also likely to be opportunities to assess algal and microbial (bacteria/fungi) communities as well as river ecosystem functional processes (e.g. Fell et al., 2021). The successful candidate will receive training in the use of dataloggers and water sampling/analysis to monitor river physical and chemical properties, and the use of satellite imagery and GIS software to track changes in glacier extent and lake development. The project offers excellent opportunities for travel, for fieldwork, laboratory placements with overseas collaborators and to present findings at international scientific meetings.

References

Brown et al. 2018. Nature Ecology & Evolution 2, 325-333

Fell et al. 2017. BioScience 67: 897–911

Fell et al. 2021. Nature Climate Change 11: 349–353

Hieber et al. 2001. Archiv für Hydrobiologie 154: 199-223

IPCC. 2019. Special Report on the Ocean and Cryosphere in a Changing Climate

Maiolini et al. 2006. Hydrobiologia 562: 217–229

Milner et al. 2017. Proceedings of the National Academy of Sciences 114, 9770-9778

Taylor et al. 2023. Nature Communications 14: 487