Step 1: Read the question.
We must name the type of ecosystem found in the Coringa region.
Step 2: Where Coringa is.
The Coringa Wildlife Sanctuary lies in the Godavari delta near Kakinada in Andhra Pradesh, right where the river meets the sea.
Step 3: What grows there.
In such coastal delta areas, salt tolerant trees with special breathing roots grow in the muddy tidal water. These special forests are called mangroves.
Step 4: Why mangrove fits.
Coringa is famous as one of India's largest mangrove forests. The trees there survive in salty, waterlogged soil.
Step 5: Rule out the others.
Grasslands, desert, and mountain ecosystems do not form in a salty coastal delta. They belong to very different climates and land.
Step 6: Conclude.
The Coringa region has a mangrove ecosystem.
\[ \boxed{\text{Mangrove}} \]