Water hyacinth is an aquatic invasive plant originated in Amazon basin. The dense mats of water hyacinth prohibit the penetration of sunlight into water. As a result no photosynthesis in aquatic plant and phytoplankton. That leads lower oxygen level in water.

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Black hole is not quite black but it is shiny a little bit. Black hole radiates energy from its event horizon.

Event horizon is the boundary of black hole.

Environmental pollution is a great problem now a days. There have different types of pollution.

Air pollution
Water pollution
Soil pollution
Thermal pollution
Ultraviolet radiation
Radiation
Sound pollution

Each and every pollution is very harmful for eenviroment.