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Coastal and Marine Ecosystem

America's Coastlines ImageCoastal wetlands: Coastal wetlands are affected by many stressors, several of which could exacerbate the impacts of climate change. The most common of these are population increase, development pressure, over fishing, pollution, invasive species, and excess nutrient enrichment. The major climate stressors on coastal wetlands include inundation, saltwater intrusion into fresh and brackish marshes, and erosion as a result of sea-level rise and flooding. Coastal wetlands are usually squeezed between advancing seas (climate stressors) and human activities (non-climate stressors). The United States Environmental Protection Agency (U.S.EPA, 2002) estimates that a projected global sea-level rise of 20 inches by 2100 could inundate between 5-60 percent of coastal wetlands. The Mid-Atlantic region could lose about 900 square miles of coastal wetlands ( Anderson, 2002). A risk ranking of lands vulnerable to sea-level rise along the Atlantic Coast is provided below.

 

Text Box: Coastal Vulnerability Index for the US Atlantic Coast: Predicting shoreline retreat and land loss rates as a result of sea-level rise is crucial in assessing biological destruction and preparing coastal zone management strategies. The following table shows a method used to determine a coastal vulnerability index (CVI) as a result of sea-level rise for the US Atlantic Coast. Areas along the coast are assigned a ranking from very low to very high risk, based on the analysis of physical variables that contribute to coastal change. To see the map of the CVI calculated for the US Atlantic Ocean coast, click on http://pubs.usgs.gov/of/of99-593/ Ranking of coastal vulnerability index Very low Low Moderate High Very High Variable 1 2 3 4 5 Geomorphology Rocky, cliffed coasts, Fiords, Fiards Medium cliffs, Indented coasts Low cliffs Glacial drift Alluvial plains Cobble beaches Estuary, Lagoon Barrier beaches Sand Beaches,Salt marsh Mud flats, Deltas Mangrove, Coral reefs Coastal Slope (%) >.2 .2-.07 .07-.04 .04-.025 <.025 Relative sea-level change (mm/yr) <1.8 1.8-2.5 2.5-2.95 2.95-3.16 >3.16 Shoreline Erosion/ Accretion (m/yr) >2.0 Accretion 1.0-2.0 -1.0-+1.0 Stable -1.1 - -2.0 < -2.0 Erosion Mean tide range (m) >6.0 4.1 – 6.0 2.0 – 4.0 1.0 – 1.9 <1.0 Mean waveheight (m) <.55 .55 - .85 .85 – 1.05 1.05 – 1.25 >1.25 Source: http://pubs.usgs.gov/of/of99-593/pages/cvi.html

 

Suspended Sediments

Estuaries and Bays:  Estuaries and bays are vulnerable to climate change as a result of

  • increases in water temperature,
  • modification of fresh water inputs from changes in the frequency and intensity of storms,
  • changes in the frequency and strength of hurricanes, and
  • more frequent and extended drought periods.

Sea-level rise can significantly impact the physical, chemical, and biological stability of estuaries and bays. The Mid-Atlantic Coast is expected to experience a relative sea-level rise of 7.5 inches by 2030, and 26 inches by 2095. This could cause the migration or loss of key species because of reduced wetlands coverage and a reduced amount of suitable shallow water habitat for breeding. Such changes would affect predator-prey relationships and thereby the overall character of the ecosystem. The following table discusses historical changes of this type for waterfowl in the Chesapeake Bay.

Decline of Waterfowl in the Chesapeake Bay

Ocean Margins and Marine Fisheries: Conditions for marine life could be affected by changes in temperature, precipitation, wind currents, salinity, and sea-level rise. Marine life is adapted to existing climate conditions, and if these climate conditions change, it could be difficult for them to adapt to their modified environment. In particular, the survival and growth of marine species, including the food sources for fish, could be disrupted. For example, a rise of about 2 oF in ocean temperatures could affect the mortality of some organisms and their geographic distributions--resulting in pole-ward shifts in the distribution of marine populations. Studies predict that cod, American plaice, haddock, Atlantic halibut, redfish, and yellowtail flounder could shift toward the north from their current southern limits in the Gulf of Maine and off the New England coast (Boesch et al., 2000). Some scientific observations on coastal fisheries are discussed in the box below.

America's Coastlines Image - line0773

Courtesy B. Mundy,
National Marine Fisheries Service

Text Box: Climate impacts on coastal fisheries: § During the 1970s and 1980s, populations in many of the Northeast's commercially important fisheries, including cod, haddock, and yellowtail flounder dropped. Even though, over-fishing could be cited as the major cause, ocean warming played a role in altering the distribution and reproductive process of coastal species. Interactions between temperature and salinity, which can be altered with changes in temperature and precipitation, determine the range that a species can tolerate and successfully inhabit (NAST, 2001). § Similarly, from 1959 to 1989, a fish community species composition shifted in Narragansett Bay, Rhode Island, from a resident cold-water, winter flounder dominant community to a migratory, warmer-water marine community. “Warmer water temperatures appear to have set off a chain of circumstances that began with the loss of the winter flounder population and resulted in increased populations of invertebrates and migrant fishes. During this period, the winter flounder population crashed on two occasions such as during a multi-year warming trend of the winter-spring spawning period. A recovery of the winter flounder populations coincided with two successive cold winters. Moreover, large invertebrates -- such as crabs, squid, lobster (only in the Bay), and mantis shrimp -- moved into the region earlier in the season and in greater numbers. By the third decade of observation, the butterfish, originally a summer migrant species had increased so much that it ranked fourth in abundance in the Narragansett Bay area” (NAST, 2001). Source: http://www.usgcrp.gov/usgcrp/nacc/education/northeast/ne-edu-7.htm

Next: Freshwater Ecosystems