By: Darrin Ambat
Hi everyone! My name is Darrin and I am entering my third year as a M.S. student at San Diego State University (SDSU). Throughout my academic career, human-induced environmental change has always interested me, specifically global warming, hypoxia, and ocean acidification (OA) and their effects on marine fishes. Imagine you are a California resident who’s lived in comfortable weather your entire life and then suddenly you’re forced to live in an extreme environment like a hot desert or on another planet where there is little to no oxygen. Hard to imagine that would go well, right? Well that’s kind of the story for some marine organisms like fish who are subject to rapid environmental change. Fish are not only an important economic resource in terms of human consumption, but they also play a critical role in the ecology of marine ecosystems. Thus, my study will provide an innovative solution to examining how human-induced disturbances impact marine ecosystems.
My research focuses on the effects of OA on the reproduction of bluebanded gobies. My primary goal is to develop novel techniques to evaluate how OA affects bluebanded goby reproductive output and behavior under ecologically realistic conditions in both laboratory and field experiments. My project is broken into two parts. Part I uses OA mesocosms to examine bluebanded goby reproduction and behavior under present day (ambient) and future (lowered seawater pH/acidified) conditions in the laboratory. Part II uses benthic chambers to take the mesocosm studies into the field and repeat these experiments incorporating variables not present in the laboratory setting.
Figure 1. Left: Photograph of benthic chamber deployed in Big Fisherman’s Cove, Catalina Island. Right: Benthic chamber containing injected seawater with green fluorescein dye (GFD) indicator added to locate seawater leakage.
The USC Wrigley Institute of Environmental Studies (WIES) is the ideal location for my study due to its proximity to my study site and access to dense populations of bluebanded gobies. I have had the opportunity to conduct research at WIES during previous summers as a research intern and even conducted preliminary thesis research, so I was eager to be back as a Wrigley Fellow. Unfortunately, due to COVID-19 restrictions getting out to the island has been delayed. Without access to the island, conducting field work using benthic chambers must be put on hold for the time being. I now focus my efforts on conducting OA trials in a laboratory setting at the Coastal and Marine Institute Laboratories (CMIL) in San Diego. The system has been fully built and I am now beginning preliminary trials.
Figure 2. Left: Tank arrangement with four Tunnels of Love placed inside each tank to encourage reproduction. Right: Bluebanded gobies in Tunnels of Love and photographs of their eggs. Photo credit: George Jarvis.
Bluebanded gobies are placed in either control tanks kept at ambient conditions or treatment tanks that are acidified by lowering the seawater pH based on future seawater pH projections for the end of the century. Most experimental OA studies have held seawater pH levels constant, which reveal sensitivities and responses of individual species, but may not reflect an organism’s ability to recover from temporary perturbations in realistic coastal zone conditions where pH varies on a daily scale. Thus, this study will address this concern by using a lowered seawater pH that is dynamic relative to ambient conditions, while allowing pH to fluctuate naturally as may occur in ambient conditions due to photosynthesis and respiration by marine organisms. Bluebanded gobies will reproduce on artificial reefs within nesting tubes called Tunnels of Love. Their eggs will then be counted to quantify total reproduction and video recordings will be analyzed to examine adult behavior.
Figure 3. Photograph from diving during preliminary trials in Big Fisherman’s Cove, Catalina Island
Although it’s a bummer to not be on Catalina this summer, I have taken this time to learn many new skills in a laboratory setting. I am also improving my methods to obtain consistent, accurate pH values for all my treatments. With the extra time, I have also been able to double, and triple check my research supplies and methods so when the time comes to head out to Catalina I will be ready to tackle the field season.