Climate-Driven Habitat Changes Restructure Northern Lake Fish Communities

The past several decades have experienced marked climate warming trends, occurring over a range of spatial and temporal scales with far-reaching and complex ecological effects.  Climate warming has been linked to changes in species distributions and timing of life history events, disruptions of food web dynamics, and, most dramatically, species extinctions, but predicting these responses to climate change effects has remained challenging.  Not all organisms will respond to climate changes in the same manner, due to differences in phenologies, physiological limits, and other attributes, and a community-perspective approach is often most effective in capturing the diversity of responses across taxa.  Evaluating communities as a collection of life history strategies can offer a framework for understanding complicated biological responses, and may lend insight into future assemblage changes.  Northern-latitude lakes strongly reflect the effects of warming temperatures and are well suited to detecting biological changes related to climate.  This research used biological and environmental data from an oligotrophic Alaskan lake to relate life history features to shifts in littoral zone fish community composition with climate change.  Since the mid-1960s, beach seining was conducted annually throughout the ice-free season, recording over 50 years of abundance values for all species captured.  These data were analyzed along with environmental measurements, including annual ice free date and water temperature.  Nonmetric multidimensional scaling (NMDS) showed a significant directional shift in the fish community structure across these five decades, indicating species assemblage sensitivity to large scale environmental changes.  Linear models returned significant results for the influence of different climate-related habitat features on community composition, with ice-free date, surface water temperature, and lake water level of the prior year as top predictors.  Preliminary results on life history response show that spring spawning, short-lived species, such as three- and nine-spine sticklebacks, represent a larger component of the community over time.  These results suggest that fish communities respond to changing climate scenarios with shifts in relative abundance of species of different life history strategies, and that examining biological responses to climate change in a context of varied life histories offers a mechanistic way to assess the trajectory of future community changes.  These findings have implications for future conservation concerns and our understanding of the role of ecological interactions in shaping ecosystem responses to disturbances.