Presentation Title

Hatching Success Rates in California Grunion Fertilized and Hatched at Different pH Levels

Start Date

November 2016

End Date

November 2016

Location

HUB 302-#120

Type of Presentation

Poster

Abstract

Ocean acidification is an environmental problem caused by elevated levels of gaseous carbon dioxide from the atmosphere interacting with ocean water. We investigated whether acidification of seawater would negatively affect fertilization and hatching success of the California Grunion (Leuresthes tenuis), a silverside fish that spawns on sandy beaches, with fertilized eggs developing in the sand. We fertilized and hatched grunion embryos at three pH levels: 8.14, the pH of seawater at the site of fish collection, and 7.98 and 7.83, based on predicted declines of 0.15 and 0.30 units in surface water pH by the end of this century. Eggs were fertilized in filtered seawater at one of the three pHs, then placed into sand moistened with seawater of the same pH and incubated at 20oC to develop for up to 28 days. We measured hatching rate by agitating embryos in seawater of the corresponding pH every day at 7-14 days post fertilization (dpf) and every two days at 16-28 dpf. There was no significant effect of pH on either fertilization rates or mean hatching rates between 7 and 14 dpf. It did, however, take longer to reach maximum hatching rate at pH 7.83 and 7.98 compared with 8.14. Our next step is to measure calcified structures (otoliths, pharyngeal teeth, and pectoral girdle) in the hatchlings to test whether reduced pH affects the process of calcification during development.

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Hatching Success Rates in California Grunion Fertilized and Hatched at Different pH Levels

HUB 302-#120

Ocean acidification is an environmental problem caused by elevated levels of gaseous carbon dioxide from the atmosphere interacting with ocean water. We investigated whether acidification of seawater would negatively affect fertilization and hatching success of the California Grunion (Leuresthes tenuis), a silverside fish that spawns on sandy beaches, with fertilized eggs developing in the sand. We fertilized and hatched grunion embryos at three pH levels: 8.14, the pH of seawater at the site of fish collection, and 7.98 and 7.83, based on predicted declines of 0.15 and 0.30 units in surface water pH by the end of this century. Eggs were fertilized in filtered seawater at one of the three pHs, then placed into sand moistened with seawater of the same pH and incubated at 20oC to develop for up to 28 days. We measured hatching rate by agitating embryos in seawater of the corresponding pH every day at 7-14 days post fertilization (dpf) and every two days at 16-28 dpf. There was no significant effect of pH on either fertilization rates or mean hatching rates between 7 and 14 dpf. It did, however, take longer to reach maximum hatching rate at pH 7.83 and 7.98 compared with 8.14. Our next step is to measure calcified structures (otoliths, pharyngeal teeth, and pectoral girdle) in the hatchlings to test whether reduced pH affects the process of calcification during development.