He was ashamed of his mark, and did not like showing it. He only showed it after Kaldur insisted. King Sha'ark blamed Topo for being an easy target.
Poseidonis September 6, 19:27UTC-2
Topo's friends knew full well what caused his injuries, and they sought out Ronal and his friends. As the argument grew hotter, Topo moved to the background. For him, it all wasn't necessary. The fight was broken up by Aqualad, and all returned home.
Topo did not join his friends to overturn a purist ambush on Aqualad and his teammates, but did go to the trench. When a mysterious spell weakened all the impure Atlanteans, Topo was affected too. He still had the wits to spout an ink screen to save King Sha'ark from a certain death. When the ink had cleared, the purists were defeated, though Topo was too weakened to continue the fight.
Poseidonis September 7, 07:01UTC-2
After Ronal was fully pardoned for his complicity in the abduction of Queen Mera, Topo successfully persuaded Sha'ark not to eat him.
Powers and abilities
Atlantean attributes: Atlanteans, although human, have through scientific and sorcerous means developed several abilities which allow them to live comfortably under the sea:
Breathe underwater: All Atlanteans are capable of surviving the aquatic atmosphere under the sea. Some accomplish this without the presence of visible gills.
Temperature resilience: Resistant to low temperatures and the effects of freezing, although notably hindered by high temperatures.