Environmental CascadeMadeline McArthur, University of Alaska-Fairbanks (UAF)
Climate change-induced warming in high-latitude coastal environments is driving shifts in environmental conditions that will likely have significant, community-wide impacts. Ecological communities, including those found in the intertidal, are adapted to and structured by both stable static and fluctuating dynamic environmental variables. However, as glacial cover in these systems recedes due to melting, the resulting increase in sediment-laden freshwater from glaciers, to rivers, to estuaries, will alter a wide array of dynamic variables, including water temperature, salinity, dissolved oxygen, turbidity, photosynthetically active radiation (PAR), and carbonate chemistry. The objective of this project is to understand how high-latitude intertidal community variability and resilience may be shaped by the response of a major ecosystem engineer, the Pacific blue mussel Mytilus trossulus, to the effects of these changing environmental conditions. Mussels create important habitat for other organisms through the interstitial spaces of their byssal threads and dense shell aggregations. They are also prey for many top predators, including sea stars, sea otters, and humans. If conditions become less favorable for mussels, their ability to maintain strong byssal threads that keep them attached to the substrate and also their shell strength may decline, possibly making them and their associated community more susceptible to disturbances. This project is closely aligned with OSRI’s mission, as it seeks to improve our understanding of how climate change-related dynamic environmental variables may decrease the ability of Subarctic mussels, and intertidal communities overall, to recover from disturbances to the environment, such as oil spills. This project will specifically identify baseline conditions including the natural variability and environmental drivers of a foundation species (blue mussels).
To investigate the impacts of both static and glacially-influenced dynamic environmental variables on mussel byssal thread attachment and shell strength, and on intertidal community variability, this study will take place at multiple intertidal sites located within a series of watersheds receiving varying amounts of fresh water and glacial discharge (i.e., a “glacial gradient”). This gradient should drive differences in water temperature, salinity, dissolved oxygen, turbidity, PAR, and carbonate chemistry. Environmental sensor data, mussel byssal thread and shell strength data, intertidal community data (percent cover and biomass), and a variety of statistical analyses will be used to achieve three main objectives, which are to 1) identify if there are trends in dynamic environmental variables along the glacial gradient, 2) determine if weaker byssal threads and shells are associated with sites experiencing more glacial influence, and 3) determine the influence of glacially-influenced dynamic environmental variables, static environmental variables, and mussel byssal thread and shell strength on the seasonal and interannual variation in intertidal community structure. Overall, this project will determine if receding glaciers can drive a cascading impact on high-latitude intertidal communities, where changing environmental conditions decrease mussel attachment and shell strength to an extent that the entire intertidal community’s stability and resilience to disturbance is impacted as well.