Seacoasts are the transition zone between land and ocean, and between freshwater coming from streams and rivers and saltwater coming from the sea. Estuaries receive nutrients from land and sea, and are revitalized with each new tide. Estuaries and coastal environments are some of the most productive areas in the world in terms of biomass produced each year. Tropical rain forests may have the highest density of trees, shrubs and other vegetation, and a high standing crop (biomass), but the new production each year does not compare with that of salt marshes (Odum 1959). Estuaries serve as nurseries for fish and shellfish, receiving schools of breeding adults, and later sending juveniles back to the oceans, and yet estuaries are among the places people congregate for living, commerce, and recreation. Wilson and Fischetti (2010) noted that: (1) although the country’s saltwater edges account for only 8% of the nation’s counties, they contain 29% of its population; (2) coastal edges contain 5 of the 10 most populous U.S. counties; and (3) growth in coastal counties outstripping that of noncoastal counties—the coastal population grew from 47 million in 1960 to 87 million in 2008. However, these spaces are filling up!