Climate change is accelerating glacier retreat across mountain regions globally. Reductions in ic... more Climate change is accelerating glacier retreat across mountain regions globally. Reductions in ice melt inputs are rapidly altering the geomorphology, flow regime and physicochemistry of rivers, modifying their habitats and ecological communities. These changes will influence the biodiversity and ecosystem service provision of alpine rivers. The responses of many taxonomic groups remain undescribed, with implications for freshwater networks and their functions not fully assessed. This thesis used chronosequences of sites representative of reducing catchment glacier cover to investigate the response of alpine river ecosystem structure and functioning to glacier retreat. A new literature-derived conceptual model was developed to synthesise the multitrophic responses of taxonomic groups to declining glacier cover and identify research gaps for this study. Focus was then placed upon benthic diatoms, a less studied group which drive primary production in alpine rivers. Observations in th...
Datafiles associated with the publication: Brown et al. (2017) Functional diversity and community... more Datafiles associated with the publication: Brown et al. (2017) Functional diversity and community assembly of river invertebrates show globally consistent responses to decreasing glacier cover. Nature Ecology & Evolution doi:10.1038/s41559-017-0426-x
This is a repository copy of Fungal decomposition of river organic matter accelerated by decreasi... more This is a repository copy of Fungal decomposition of river organic matter accelerated by decreasing glacier cover.
Global change threatens invertebrate biodiversity and its central role in numerous ecosystem func... more Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process...
Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-m... more Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-melt inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. Glacier-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric–cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing glacier cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to glacier retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the pote...
Climate change poses a considerable threat to the biodiversity of high altitude ecosystems worldw... more Climate change poses a considerable threat to the biodiversity of high altitude ecosystems worldwide, including cold-water river systems that are responding rapidly to a shrinking cryosphere. Most recent research has demonstrated the severe vulnerability of river invertebrates to glacier retreat but effects upon other aquatic groups remain poorly quantified. Using new data sets from the European Alps, we show significant responses to declining glacier cover for diatoms, which play a critical functional role as freshwater primary producers. Specifically, diatom α-diversity and density in rivers presently fed by glaciers will increase with future deglaciation, yet β-diversity within and between sites will reduce because declining glacier influence will lower the spatiotemporal variability of glacier cover and its associated habitat heterogeneity. Changes in diatom assemblage composition as glacier cover declined were associated strongly with increasing riverbed stability and water temperature. At the species level, diatoms showed a gradation of responses; for example, Eunotia trinacria, found exclusively at river sites with high (≥52%) catchment glacier cover, may be affected negatively by ice loss. Conversely, seven taxa confined to sites with no glacier cover, including Gomphonema calcareum, stand to benefit. Nineteen (22%) taxa were noted as threatened, endangered, rare or decreasing on the Red List of Algae for Germany, with most at sites ≤26% glacier cover, meaning further ice loss may benefit these diatoms. However, six taxa found only in rivers ≥28% glacier cover may require reclassification of their Red List conservation status, as this habitat is threatened by deglaciation. Our identification of clear links between decreasing glacier cover and river diatom biodiversity suggests there could be significant reorganization of river ecosystems with deglaciation, for example, through alterations to primary production, biogeochemical cycles, and the shifting resource base of alpine freshwater food webs which lack significant allochthonous energy inputs. K E Y W O R D S algae, alps, climate change, diatom, glacier retreat, mountain rivers 1 | INTRODUCTION Pervasive and accelerated glacier retreat in alpine regions worldwide is predicted to intensify throughout the 21st century (Intergovernmental Panel on Climate Change [IPCC], 2014). This diminishing ice cover will ultimately reduce the contribution of ice melt to rivers, subsequently increasing the relative contributions of
Climate change is accelerating glacier retreat across mountain regions globally. Reductions in ic... more Climate change is accelerating glacier retreat across mountain regions globally. Reductions in ice melt inputs are rapidly altering the geomorphology, flow regime and physicochemistry of rivers, modifying their habitats and ecological communities. These changes will influence the biodiversity and ecosystem service provision of alpine rivers. The responses of many taxonomic groups remain undescribed, with implications for freshwater networks and their functions not fully assessed. This thesis used chronosequences of sites representative of reducing catchment glacier cover to investigate the response of alpine river ecosystem structure and functioning to glacier retreat. A new literature-derived conceptual model was developed to synthesise the multitrophic responses of taxonomic groups to declining glacier cover and identify research gaps for this study. Focus was then placed upon benthic diatoms, a less studied group which drive primary production in alpine rivers. Observations in th...
Datafiles associated with the publication: Brown et al. (2017) Functional diversity and community... more Datafiles associated with the publication: Brown et al. (2017) Functional diversity and community assembly of river invertebrates show globally consistent responses to decreasing glacier cover. Nature Ecology & Evolution doi:10.1038/s41559-017-0426-x
This is a repository copy of Fungal decomposition of river organic matter accelerated by decreasi... more This is a repository copy of Fungal decomposition of river organic matter accelerated by decreasing glacier cover.
Global change threatens invertebrate biodiversity and its central role in numerous ecosystem func... more Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process...
Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-m... more Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-melt inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. Glacier-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric–cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing glacier cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to glacier retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the pote...
Climate change poses a considerable threat to the biodiversity of high altitude ecosystems worldw... more Climate change poses a considerable threat to the biodiversity of high altitude ecosystems worldwide, including cold-water river systems that are responding rapidly to a shrinking cryosphere. Most recent research has demonstrated the severe vulnerability of river invertebrates to glacier retreat but effects upon other aquatic groups remain poorly quantified. Using new data sets from the European Alps, we show significant responses to declining glacier cover for diatoms, which play a critical functional role as freshwater primary producers. Specifically, diatom α-diversity and density in rivers presently fed by glaciers will increase with future deglaciation, yet β-diversity within and between sites will reduce because declining glacier influence will lower the spatiotemporal variability of glacier cover and its associated habitat heterogeneity. Changes in diatom assemblage composition as glacier cover declined were associated strongly with increasing riverbed stability and water temperature. At the species level, diatoms showed a gradation of responses; for example, Eunotia trinacria, found exclusively at river sites with high (≥52%) catchment glacier cover, may be affected negatively by ice loss. Conversely, seven taxa confined to sites with no glacier cover, including Gomphonema calcareum, stand to benefit. Nineteen (22%) taxa were noted as threatened, endangered, rare or decreasing on the Red List of Algae for Germany, with most at sites ≤26% glacier cover, meaning further ice loss may benefit these diatoms. However, six taxa found only in rivers ≥28% glacier cover may require reclassification of their Red List conservation status, as this habitat is threatened by deglaciation. Our identification of clear links between decreasing glacier cover and river diatom biodiversity suggests there could be significant reorganization of river ecosystems with deglaciation, for example, through alterations to primary production, biogeochemical cycles, and the shifting resource base of alpine freshwater food webs which lack significant allochthonous energy inputs. K E Y W O R D S algae, alps, climate change, diatom, glacier retreat, mountain rivers 1 | INTRODUCTION Pervasive and accelerated glacier retreat in alpine regions worldwide is predicted to intensify throughout the 21st century (Intergovernmental Panel on Climate Change [IPCC], 2014). This diminishing ice cover will ultimately reduce the contribution of ice melt to rivers, subsequently increasing the relative contributions of
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