The Effects of Elevated Atmospheric Carbon Dioxide on the Otoliths of Air Incubated Mummichog (Fundlus heteroclitus)

The mummichog (Fundlus heteroclitus) is an estuarine killifish well adapted to variable environmental conditions. This also applies to its eggs, which are frequently exposed to air during low tide after being laid on marsh grasses. With global atmospheric carbon dioxide (CO₂) levels rising, we investigated the effects of higher atmospheric CO₂ on the otoliths of air incubated larval mummichog. To replicate natural mummichog egg air incubation, 2,400 one-day post fertilization eggs were split evenly into 12 containers and placed in an incubator. A randomized selection of 6 egg containers in the incubator was exposed to 390 ppm CO₂ (control concentration) while the other random 6 were exposed to 1000 ppm CO₂ (2100 projected concentration), both at a flow rate of 15 ml/min. The eggs were held between two layers of foam and sprayed twice daily with 35 ppt water at 26˚C. After 14 days, the eggs were hatched out by being fully submerged in water. Otoliths were removed from 10 random fish from each container and imaged with a scanning electron microscope (SEM). The area of each otolith was measured using ImageJ software. No statistical differences in sizes were found between the control and treatment otoliths.