January 1, 2016.
Organisms living in coastal habitats off northern California coast are exposed to low pH and low dissolved oxygen water during strong upwelling events, but the effects of these events on coastal fishes is poorly understood. We examined the effects of short-term (1 to 24 hour) exposures to low pH (pH ~ 7.5) or low dissolved oxygen (DO; 50% O2 saturation) on the swimming performance of juvenile rockfish (Sebastes spp.). Juvenile copper rockfish (Sebastes caurinus) were collected from Trinidad Bay, and, following acclimation to laboratory conditions, were exposed to treatment conditions for intervals of 0 (control), 1, 2, 4, 8, or 24 hours. We measured critical swimming speed (uCrit)—a metric of swimming performance that integrates speed and endurance—by placing each fish into a swimming flume and increasing current speed according to a timed, stepwise sequence until exhaustion. Short-term exposures cause a decline in uCrit, with increasingly strong effect developing from 0-4 hours. Swimming performance remains depressed over longer exposures, but it is possible that recovery from initial handling stress might offset continued declines in swimming performance. Ongoing work is addressing a potential size-dependence in response to exposure, and will examine the effect of simultaneous exposure to low-pH/low-DO water, as these conditions naturally co-occur. Insights from this study address the potential ecological effects of upwelling events, which may have important demographic consequences for these ecologically and economically important species, as well as the potential consequences of increasing frequency, duration, and intensity of upwelling-driven exposures and increasing levels of global ocean acidification predicted under ongoing climate change.
Eric P. Bjorkstedt
National Oceanic and Atmospheric Administration Southwest Fisheries Science Center (NOAA SWFSC)
This project has been made possible with support from Chevron (www.chevron.com) and the California State University STEM Teacher Researcher Program.