A) Excessive richness of nutrients in a body of water - Eutrophication
This is the process whereby the aquatic habitat get enriched with nutrients as a result of algae bloom which causes a threat to marine habitat.
B) The border between two biomes- Ecotone
Ecotone simply refers to the transition from one biome and another since we cannot decipher the boundary that separates two biomes.
C) Formed by a body of standing or still water -Lentic ecosystems
Any ponds, marshes, lakes or swamps whether small or large that stay still is called a Lentric ecosystems.
D) The beginning and source of the river- Headwaters
Any source where a river start to flow be it a lake, spring, is called a Headwater.
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