1998 Year of the Ocean Perspectives on Marine Environmental Quality 



concomitant loss of diversity, as a result of human activities such as channelization, drainage for 

 agricultural purposes, development, and dredging. 



Such a drastic decrease in habitat acreage has had a great impact on marine and terrestrial 

 species dependent upon these ecosystems for spawning, nurseries, and habitat. During some 

 stage in life, 77 percent of all commercial species and 80-90 percent of recreational fish and 

 shellfish catches rely upon wetland areas (NOAA, 1997). Eighty percent of endangered species 

 depend on habitat within 10 vertical feet of sea level (NOAA, 1995). Between 80 and 90 percent 

 of U.S. shorelines are undergoing net long-term erosion; while some of this erosion is due to 

 natural processes, erosion resulting from anthropogenic factors has increased over the past 

 century. The development of tidal flats and barrier islands has eliminated unique and essential 

 habitats for many plants and animal species. 



In addition to physical alterations, water quality impairment and habitat loss can be 

 caused by excess nutrient loading, sedimentation, and increasing levels of pathogens and toxic 

 chemicals. Sediment and nutrient loadings have increased turbidity and light attenuation, thereby 

 killing submerged aquatic vegetation. Only 10 percent of the seagrass beds that existed several 

 decades ago still exist today. In Florida, siltation and nutrient loads have reduced mangrove 

 forests by approximately 24 percent and caused severe damage to coral reef systems (U.S. EPA, 

 1997). Alteration of the natural flow can have significant effects on water quality, health, and 

 distribution of living resources. In the upper Laguna Madre River of the Corpus Christi Bay, 

 changes in freshwater flow in 1996 have increased salinhies from 10-20 ppt"' to 55 ppt (U.S. 

 EPA, 1997). The change in salinity has decreased the total productivity of the oyster population 

 and reduced the economic value of the estuary. 



While the dredging of harbors and shipping channels can cause temporary increases in 

 turbidity, dredging is necessary for port accessibility and navigational safety. Recent years have 

 seen a change in emphasis on dredged material management. Ports lose revenue when vessels 

 change their destination to ports with shipping channels deep enough to accommodate them. It is 

 now recognized that dredged material can also be a resource for enhancing or building wetland 

 habitats, or for other uses such as beach renourishment. Beneficial use of dredged material 

 usually costs more than traditional open water disposal methods. However, with the passage of 

 more consistent cost-sharing formulas between federal and local project sponsors (e.g., the Water 

 Resources Development Act of 1996), it is expected that the amounts of dredged material used to 

 build habitats will continue to increase. 



On a more global scale, climate change as manifested by rises in sea level and changes in 

 storm patterns and storm surges has led to environmental impacts that include: 



• increased erosion 



• increased salinity of estuaries and freshwater aquifers 



• altered tidal ranges in rivers and bays 



25 ppt equals parts per thousand 



E-15 



