Long-term changes in macroinvertebrate communities in streams of Denali National Park, Alaska

• Main Author: Loza Vega, Eva Maria
• Other Authors: Milner, Alexander (Sandy), Ledger, Mark, Matthews, Thomas, other
• Format: Thesis
• Language: English
• Published: 2020
• Subjects: G Geography (General); Pacific; North Atlantic; North Atlantic oscillation; Subarctic; Alaska
• Online Access: http://etheses.bham.ac.uk//id/eprint/10523/7.hassmallThumbnailVersion/Loza-Vega2020PhD.pdf; http://etheses.bham.ac.uk//id/eprint/10523/; http://etheses.bham.ac.uk//id/eprint/10523/7/Loza-Vega2020PhD.pdf

Climate change is a major global issue influencing stream ecosystems that may result in changes in invertebrate communities over the long term. Stream ecosystems in subarctic regions receive water from a number of different water sources, making them vulnerable to extreme weather events and warmer air temperature, both potentially affecting freshwater taxa through changing hydrological regimes. Macroinvertebrates were collected every year in 10 streams in Denali National Park (DNP) from 1994 to 2016, except 1997. In a number of streams some taxa in macroinvertebrate communities varied markedly from year to year in terms of abundance and diversity. Large-scale atmospheric patterns (Pacific Decadal Oscillation, North Atlantic Oscillation, Oceanic Niño Index and Pacific-North America) and local climatic variables (e.g. air temperature, precipitation and snowfall) were assessed to see if they affected the persistence and compositional stability of stream macroinvertebrates communities in a changing climate in DNP, Alaska, over this 22 year study period. PDO, NAO and ONI were found to be the large-scale climatic patterns having a direct effect on spring hydrological seasonal regimes, which in turn influenced the stream communities. These patterns also caused warmer spring air temperature at local scales, and linked to other principal environmental variables, created variations in macroinvertebrate persistence and compositional stability. Three distinctive groups of years were evident in a number of the streams during the study period: (1) pre 2005, (2) 2005 to 2008 and (3) post 2008. Rainfall and associated spring floods were the main variables affecting these distinct groups of macroinvertebrate benthic communities. Some Ephemeropteran taxa (e.g. Baetis and Epeorus) and Plecoptera (Capnia and Doddsia) showed the capacity to recover from these events during spring. Overall, the findings indicate that the benthos communities in the study streams were extremely sensitive to the effects of local climate drivers, which has wider implications for aquatic environments worldwide.