The capture of Sveaborg was a major flip for the Russian campaign in Finland, as it removed the threat of a counterattack from the south and west. To Sweden it was a devastating blow as it made the resupply of the battered  Finnish army much more difficult.
The fall of Sveaborg marked a significant turning point in the Russian campaign in Finland, as it neutralized the potential for a southern or western counterattack. For Sweden, it was a calamitous event, rendering the resupply of the Finnish army even more complicated.