Wed, Aug 17, 2022: 9:15 AM-9:30 AM
512A
Background/Question/MethodsGlobal climate change is rewiring food webs across landscapes by altering both abiotic regimes and interactions between organisms. In landscapes influenced by the alpine cryosphere, climate-driven loss of seasonal meltwater signatures may alter stream food webs. Meltwater streams fed by glaciers, icefields, and snow frequently have flow, temperature, and biogeochemical regimes distinct from non-meltwater streams. This physicochemical heterogeneity may support a diversity of freshwater food webs in landscapes where meltwater and non-meltwater streams co-occur. Here, we examine how the structure of food webs supporting Pacific salmon vary between four streams in coastal southeast Alaska: glacier-fed, snow-fed, rain-fed, and one fed by a combination of rain, snow and glacial-melt. We construct quantitative flow food web models using trophic-basis-of-production approach to illuminate the pathways of energy flow that support juvenile salmon.
Results/ConclusionsWe found that secondary macroinvertebrate production was highest in the rain-fed (9.6 g m-2 yr-1) and snowmelt stream (7.1 g m-2 yr-1), intermediate in the combined-signature stream (4.1 g m-2 yr-1) and lowest in the glacier-fed stream (2.9 g m-2 yr-1). The trophic pathways that support fish production varied significantly between stream types with limited overlap between and a greater number of resource flows supporting Coho and Dolly Varden in glacial- and snowmelt streams and substantial overlap in rainwater and combined-signature sites. Although meltwater streams may be less productive overall, they support fish via distinct and diverse pathways that could contribute to population resilience with the region. This may be especially true for mobile consumers that can track different energy flow pathways across these spatially structured food webs. As glacial and snowmelt contributions to surface waters decline, these distinct meltwater food webs are at risk of extirpation, which could negatively impact salmon populations.
Results/ConclusionsWe found that secondary macroinvertebrate production was highest in the rain-fed (9.6 g m-2 yr-1) and snowmelt stream (7.1 g m-2 yr-1), intermediate in the combined-signature stream (4.1 g m-2 yr-1) and lowest in the glacier-fed stream (2.9 g m-2 yr-1). The trophic pathways that support fish production varied significantly between stream types with limited overlap between and a greater number of resource flows supporting Coho and Dolly Varden in glacial- and snowmelt streams and substantial overlap in rainwater and combined-signature sites. Although meltwater streams may be less productive overall, they support fish via distinct and diverse pathways that could contribute to population resilience with the region. This may be especially true for mobile consumers that can track different energy flow pathways across these spatially structured food webs. As glacial and snowmelt contributions to surface waters decline, these distinct meltwater food webs are at risk of extirpation, which could negatively impact salmon populations.