River ecosystem responses to decreasing glacier cover

Climate change poses a considerable threat to the biodiversity of high altitude ecosystems, with Arctic alpine regions across the world already beginning to show clear responses to warming (Milner et al., 2017). Glacier mass-balance studies show consistent decreases over the last century in most regions and it has been suggested that retreat may even be accelerating in many locations.

Continued negative glacier mass-balance will lead to glacier- and snow-melt reductions (Barnett et al., 2005), proportionally greater groundwater contributions (Brown et al., 2006) and changes in proglacial riverscape dynamics (Malard et al., 2006). These hydrological changes will dramatically alter alpine river communities (Brown et al., 2007; Brown & Milner, 2012; Jacobsen et al., 2012).

However, to date most studies have focused on macroinvertebrates, there have been no detailed assessments of responses at higher levels of organisation (i.e. whole food webs; Clitherow et al., 2013; Fell et al., 2017) and we know little about how important ecosystem processes such as primary production or respiration will change. These are major research gaps because the potential for emergent properties in complex systems means it is difficult to predict ecosystem responses, and therefore to accurately inform conservation and management strategies, by simply extrapolating from lower levels of organization (i.e. population responses; Woodward et al., 2010).

The topic is relatively broad and would be focused to suit the expertise and interests of the successful candidate. Example approaches could be to undertake field surveys of how components of food webs (e.g. specific groups such as microbes/algae/macroinvertebrates), their connections via feeding links, and/or functional processes associated with aquatic ecosystems (e.g. nutrient uptake, primary production) are linked to glacier retreat.

The project would identify a continuum of rivers to work on, from those draining highly glacierized basins to those with no glacial influence. By examining rivers fed from different water sources, a major output from this project will be predictions about how river ecosystems can be expected to change in response to future climate change. The student will benefit from access to extensive data that already exists for many locations globally (e.g.

Brown et al., 2018, Fell et al., 2018), for example allowing comparative studies using the same methods. Links to ongoing projects at Leeds or via collaborators would allow the student to conduct a field campaign in either Peru (e.g. https://gtr.ukri.org/projects?ref=NE%2FS013296%2F1), Scandinavia (via the Norwegian Institute for Water Research, NIVA) or the Himalayas (http://gotw.nerc.ac.uk/list_full.asp?pcode=NE%2FP016146%2F1).

Project Goals

This research is anticipated to allow detailed assessments of: (1) macroinvertebrate/algal and/or microbial community composition, (2) stream food web structure (see e.g. Clitherow et al., 2013). A combined approach of descriptive and experimental approaches may be utilised.

The successful applicant will have opportunities to undertake fieldwork to collect their own primary datasets from glacier-fed rivers. This study design will allow comparisons of glacier-fed rivers from different basins and potentially different mountain ranges, and analyses of seasonal dynamics from more intensively monitored rivers.