How do seagrasses and mangroves increases the health of coral reefs?

The dense root systems of mangrove forests trap sediments flowing down rivers and off the land. This helps stabilizes the coastline and prevents erosion from waves and storms. ... By filtering out sediments, the forests also protect coral reefs and seagrass meadows from being smothered in sediment.

Mangroves and seagrasses stabilize the sediments, slow down the water movements and trap the heavy metals and nutrient rich runoff, thus improving the water quality for corals and fish communities. They also enhance the biomass of coral reef fishes by providing nursery habitats.

if you mean hydrogen and oxygen then water is the product