Global climate change and potential effects on Pacific salmonids in freshwater ecosystems of southeast Alaska

Abstract

General circulation models predict increases in air temperatures from 1 • C to 5 • C as atmospheric CO 2 continues to rise during the next 100 years. Thermal regimes in freshwater ecosystems will change as air temperatures increase regionally. As air temperatures increase, the distribution and intensity of precipitation will change which will in turn alter freshwater hydrology. Low elevation floodplains and wetlands will flood as continental ice sheets melt, increasing sea-levels. Although anadromous salmonids exist over a wide range of climatic conditions along the Pacific coast, individual stocks have adapted life history strategies-time of emergence, run timing, and residence time in freshwater-that are often unique to regions and watersheds. The response of anadromous salmonids will differ among species depending on their life cycle in freshwater. For pink and chum salmon that migrate to the ocean shortly after they emerge from the gravel, higher temperatures during spawning and incubation may result in earlier entry into the ocean when food resources are low. Shifts in thermal regimes in lakes will change trophic conditions that will affect juvenile sockeye salmon growth and survival. Decreased summer stream flows and higher water temperatures will affect growth and survival of juvenile coho salmon. Rising sea-levels will inundate low elevation spawning areas for pink salmon and floodplain rearing habitats for juvenile coho salmon. Rapid changes in climatic conditions may not extirpate anadromous salmonids in the region, but they will impose greater stress on many stocks that are adapted to present climatic conditions. Survival of sustainable populations will depend on the existing genetic diversity within and among stocks, conservative harvest management, and habitat conservation.

Run-of-River hydropower and salmonids: potential effects and perspective on future research

“…In general, higher temperatures increase metabolic rates and potential for growth up to the thermal optimum, beyond which increases in water temperature are physiologically detrimental to fish and can lead to death (Brett 1995). Below the thermal optimum, increases in growth with temperature are only possible when food or other resources are not limiting (Bryant 2009;Taylor and Walters 2010). If food consumption decreases while water temperatures increase, fish experience higher metabolic costs that may lead to slower growth and later maturation (e.g., Van Poorten and McAdam 2010) or declines in total biomass (Beakes et al 2014).…”

Environment shapes invertebrate assemblage structure differences between volcanic spring-fed and runoff rivers in northern California

“…Regional climate change predictions indicate that runoff rivers in the western USA will experience earlier peak flow periods, prolonged periods of summer/autumn low flow, higher magnitude winter floods, and increases in water temperature (Stewart et al 2004, Bryant 2009, Das et al 2011. These changes may not bode well for lotic ectotherms.…”

“…Coldwater habitat in the western USA and elsewhere is projected to decline significantly with decreasing summer base flows and increasing stream temperatures (Stewart et al 2005, Bryant 2009, Wenger et al 2011. These 2 climate-induced effects may have a negative synergistic effect on coldwater biota as the time between elevated summer water temperature and autumn base flow declines (Arismendi et al 2013).…”

Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

“…Given the strongly seasonal nature of many ecological processes, the attendant variations in fluvial aquatic habitat and delivery of freshwater and dissolved and suspended material to the coastal ocean may have particularly broad importance (e.g., [64,71]). Although an analysis of hydroecological linkages in this region is beyond the scope of this study, such linkages have been highlighted for marine and freshwater species at multiple tropic levels ( [8,23,64]; see also [47]). These relationships are established by the transport and influence (variations in timing and magnitude) of freshwater runoff.…”