The coastal areas of the Andaman Sea are characterized by mangrove forests and seagrass meadows. Mangroves cover between more than 600 km2  of the Thai shores of Malay Peninsula whereas seagrass meadows occupy an area of 79 km2 .:25-26 Mangroves are largely responsible for the high productivity of the coastal waters - their roots trap soil and sediment and provide shelter from predators and nursery for fish and small aquatic organisms. Their body protects the shore from the wind and waves, and their detritus are a part of the aquatic food chain. A significant part of the Thai mangrove forests in the Andaman Sea was removed during the extensive brackish water shrimp. Mangroves were also significantly damaged by the 2004 tsunami. They were partly replanted after that, but their area is still gradually decreasing due to human activities.:6-7 Other important sources of nutrients in the Andaman Sea are seagrass and the mud bottoms of lagoons and coastal areas. They also create a habitat or temporal shelter for many burrowing and benthic organisms. Many aquatic species migrate from and to seagrass either daily or at certain stages of their life cycle. The human activities which damage seagrass beds include waste water discharge from coastal industry, shrimp farms and other forms of coastal development, as well as trawling and the use of push nets and dragnets. The 2004 tsunami affected 3.5% of seagrass areas along the Andaman Sea via siltation and sand sedimentation and 1.5% suffered total habitat loss.:7
Question: What causes high productivity?
Answer: Mangroves