Meeting Abstract
8.3 Friday, Jan. 4 Understanding climate change impacts on Delta Smelt KOMOROSKE, LM*; HASENBEIN, M; LINDBERG, J; CONNON, RE; FANGUE, NA; UC Davis; UC Davis; UC Davis; UC Davis; UC Davis lmkomoroske@ucdavis.edu
The delta smelt (Hypomesus transpacificus) is an endemic fish in the San Francisco Bay–Delta and is an important ecological indicator species. Delta smelt have been rapidly declining in the past 30 years due to a variety of physiological and ecological stressors, and climate change is expected to further impact this species by altering regional temperatures and salinities. Some thermal and salinity studies have investigated whole organism tolerance in adults, but little is known about how tolerance thresholds vary across life stages, sublethal stress thresholds, or their mechanistic drivers. We sought to understand climate change impacts on delta smelt by conducting Critical Thermal Maximum (CTmax) and acute thermal exposure-recovery gene expression experiments in all life stages. Similarly, we assessed salinity tolerance and sublethal stress responses by exposing fish to environmentally relevant salinity increases (mimicking tidal cycles). We found that CTmax differed between life stages (15-16°C acclimation, CTmax larval=29.9°C+/- 0.35; adult=26.3°C+/- 1.8). For salinity, percent mortality was similar for all treatments at short time periods (0-6hrs), but increased at high salinity levels over longer time periods (at 48 hours: 18ppt =92% vs. 0ppt=47%), suggesting that while fish may be able to cope with short periods of increased salinity, they may not subsist in the long-term. We also linked these tolerance data to gene expression profiles. Climate change may result in temperature and salinity levels under which delta smelt cannot effectively persist physiologically, causing large-scale habitat reduction or loss. Quantifying tolerance and sublethal stress thresholds helps to understand these physiological limits and better predict habitat suitability for delta smelt under various management plans in the Bay-Delta.
