Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg

- With ocean change, we see a decrease in egg size across many marine invertebrates, with the exception of cephalopods.
- Low pH reduces the egg jelly coat size and intracellular pH with implications for impaired function and fertilization.
- Transgenerational effects may reduce the negative impacts of stressors on reproductive output for some species.

In marine invertebrates, the environmental history of the mother can influence fecundity and egg size. Acclimation of females in climate change stressors, increased temperature and low pH, results in a decrease in egg number and size in many taxa, with the exception of cephalopods, where eggs increase in size. With respect to spawned eggs, near future levels of ocean acidification can interfere with the egg's block to polyspermy and intracellular pH. Reduction of the extracellular egg jelly coat seen in low pH conditions has implications for impaired egg function and fertilization. Some fast generation species (e.g. copepods, polychaetes) have shown restoration of female reproductive output after several generations in treatments. It will be important to determine if the changes to egg number and size induced by exposure to climate change stressors are heritable.