Meeting Abstract
In the Salish Sea, Low Salinity Events (LSE) characterized by a decrease in salinity and an increase in temperature, are becoming common. They occur during the spring and summer months when Arctic ice melts, Fraser River discharge into the Salish Sea increases, and marine invertebrates including the sand dollar Dendraster excentricus and the sea star Pisaster ochraceus reproduce. During LSEs, temperatures can increase from 12° C to as high as 18° C and salinities can drop from 30 to 21ppt in a few hours around the San Juan Islands. Phytoplankton blooms are often associated with these events. Whether larvae of these species are able to capitalize on an abundance of phytoplankton during LSEs is unknown. This study looked at the effects of high temperatures (18-21° C) and low salinity (20 ppt) on larval feeding for both species. Sixteen, 26, 28, 39 and 41-day old Pisaster and 13, 15, and 17-day old Dendraster larvae were placed into one of three treatments: Control (C), low salinity (LS), or low salinity and high temperature (LSE) for 24 hours. They were then allowed to feed for 30 seconds, 5 minutes, or 10 minutes (depending on species and age) in bowls containing 1000 cells/ml of the alga Isochrysis galbana in either 30 or 20ppt. salinity. Particle capture increased with larval age and was generally higher for Pisaster than Dendraster larvae. Interestingly, Pisaster larvae fed at significantly higher rates after being exposed to a low salinity event for 24 hours than Dendraster larvae. This implies thatPisaster populations might be less affected by increases in low salinity events as their larvae might benefit from algal blooms associated with these events. These species-specific differences in response to LSEs could lead to shifts in community structure of intertidal habitats in the Salish Sea.
