Question: Explain trophic cascades in oyster reefs. Name some common characteristics that salt marshes, mangroves and seagrass beds share. Why are cord grass, sea grass, and mangroves foundation species? List and describe several ecological services provided by oyster reefs. How are they similar to seagrasses, marshes, mangroves? How does variation in salinity and predation risk affect oyster distributions? What factors affect the distribution of oysters in estuaries? What limits them in low salinity? High salinity? Be Able To Compare All Of The Communities. How Are They Similar? Different? Need Assignment Help?