Future impacts of ocean acidification on reproduction of exposed marine organisms with consequences at the population level still have to be properly analyzed and understood. For fertilization, eggs of echinoderms are directly released into seawater where the acrosome reaction takes place. Therefore, gametes are directly exposed unprotected to the detrimental conditions of an acidified environment. There is evidence that internal pH levels of cells change within 15-30 min conditioned by the external pH to which the eggs are exposed. Internal pH of the eggs plays an important role in the metabolic functionality of the signaling pathways and enzymatic activations induced by the contact with the sperm. These processes prohibit polyspermy and initiate normal embryonic development. We selected a species of sea urchin from the Arctic (Strongylocentrotus droebachiensis) to study the effect of sea water acidification on fertilization success. First results on fertilization experiments under various pH conditions (180 µatm, 380 µatm, 980 µatm, 1400 µatm and 3000 µatm) at natural temperatures and with two different approaches (with or without pre-incubation of the eggs) will be presented. Dramatic effects on fertilization success and embryonic development were identified under prognostic future pH conditions. We will discuss the vulnerability of the process of fertilization under past, present and future conditions.