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Streamwater dissolved oxygen (DO) concentrations are driven by interacting physical and biotic parameters. Future DO depletion events in small, coastal salmon streams are therefore likely to be driven by changes in hydrology in addition to atmospheric warming. We measured DO, temperature, discharge and spawning salmon abundance in upstream (reference reach) and downstream salmon bearing reaches of four streams in southeast Alaska to determine how multiple physical and biotic factors interact to control streamwater DO. Stream temperature ranged from 5.1 to 15.8 °C and fell within the optimum range that is considered favorable for salmon physiology. Concentrations of DO ranged from 2.8 to 12.3 mg/L, with concentrations...
The melting cryosphere adds heterogeneity to the abiotic and biotic characteristics of many high latitude and montane rivers. However, climate change threatens the cryosphere's persistence in many regions. While existing research has explored the impacts of cryospheric loss on the diversity and structure of freshwater communities, implications for functional traits of communities, such as production of aquatic invertebrates, remain unresolved. Here, we quantified aquatic invertebrate community structure and secondary production in southeast Alaska (USA) streams that represent a meltwater to non-meltwater gradient, including streams fed primarily by: (1) glacier-melt, (2) snowmelt, (3) rainfall, and (4) a combination...
Categories: Publication; Types: Citation
Abstract (from http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132652): Climate warming is likely to cause both indirect and direct impacts on the biophysical properties of stream ecosystems especially in regions that support societally important fish species such as Pacific salmon. We studied the seasonal variability and interaction between stream temperature and DO in a low-gradient, forested stream and a glacial-fed stream in coastal southeast Alaska to assess how these key physical parameters impact freshwater habitat quality for salmon. We also use multiple regression analysis to evaluate how discharge and air temperature influence the seasonal patterns in stream temperature and DO. Mean daily...
Abstract (from http://link.springer.com/article/10.1007/s10021-014-9777-1): The Coast Mountains of southeast Alaska are currently experiencing some of the highest rates of glacier volume loss on Earth, with unknown implications for proglacial stream biogeochemistry. We analyzed streamwater for δ18O and dissolved organic matter (DOM) biogeochemistry (concentration, δ13C-dissolved organic carbon (DOC), and fluorescence characterization) during the 2012 glacial runoff season from three coastal watersheds in southeast Alaska that ranged in glacier coverage from 0 to 49% and a glacier outflow stream. Our goal was to assess how DOM biogeochemistry may change as receding glaciers are replaced by forests and glaciers contribute...
Abstract: We measured stream temperature continuously during the 2011 summer run-off season (May through October) in nine watersheds of Southeast Alaska that provide spawning habitat for Pacific salmon. The nine watersheds have glacier coverage ranging from 0% to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal glacial meltwater hydrograph. Multiple linear regression models identified mean watershed elevation (related to glacier extent) and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and...
Abstract (from http://pubs.acs.org/doi/full/10.1021/acs.est.5b02685): Dissolved organic carbon (DOC) plays a fundamental role in the biogeochemistry of glacier ecosystems. However, the specific sources of glacier DOC remain unresolved. To assess the origin and nature of glacier DOC, we collected snow from 10 locations along a transect across the Juneau Icefield, Alaska extending from the coast toward the interior. The Δ14C-DOC of snow varied from −743 to −420‰ showing progressive depletion across the Icefield as δ18O of water became more depleted (R2 = 0.56). Older DOC corresponded to lower DOC concentrations in snow ( R2 = 0.31) and a decrease in percent humic-like fluorescence ( R2 = 0.36), indicating an overall...
Pulsed subsidy events create ephemeral fluxes of hyper-abundant resources that can shape annual patterns of consumption and growth for recipient consumers. However, environmental conditions strongly affect local resource availability for much of the year, and can heavily impact consumer foraging and growth patterns prior to pulsed subsidy events. Thus, a consumer's capacity to exploit pulse subsidy resources may be influenced by antecedent environmental conditions, but this has rarely been shown in nature and is unknown in aquatic ecosystems. Here, we sought to understand the importance of hydrologic variation and a salmon pulse subsidy on the foraging and growth patterns of two stream salmonids in a coastal southeast...
Categories: Publication; Types: Citation