View Data for "Undegraded" View Data for "Moderate" View Data for "Degraded"

What Is This Indicator, and Why Is It Important? This indicator describes the condition of worms, clams, snails, and shrimplike animals in bottom sediments (“benthic communities”) by reporting the percentage of area in which these communities are in “undegraded,” “moderate,” and “degraded” condition. The indicator is calculated by comparing the number and kinds of animals found in a sampling site with those that would be expected in an undisturbed area of similar character (a reference site). The indicator would be reported for estuaries and for ocean areas within 25 miles of the coast. Benthic communities reflect the influence of contaminants, oxygen levels, physical changes in habitat (such as from trawling), and shifts in temperature or salinity. They are a good indicator because contaminants accumulate in bottom sediments and hypoxia (lack of oxygen) is most severe there. Also, these animals live several years, so their response reflects exposure to these stresses over a long period, and they are fairly immobile, so their condition strongly reflects conditions at the site where they were collected (see the depleted oxygen and sediment contamination indicators).

Why Can't This Entire Indicator Be Reported at This Time? Data are not available from estuaries in Alaska or Hawaii. Only limited data are available for ocean waters out to 25 miles.

What Do the Data Show? For the 1999-2000 time period, about three-fourths of the estuary area on the Atlantic and Pacific coasts was “undegraded”. About half the estuary area in the Gulf of Mexico and about one-third of the estuary area in Puerto Rico (not shown in graphs) were “undegraded”. About a quarter of the estuary area in the North and Mid-Atlantic regions and a third of the estuary area in Puerto Rico was “degraded”, whereas in other regions, only about 10-20% was degraded. Changes from 1990-1997 to the 1999-2000 time period, other than those caused by reclassification of Mid-Atlantic data that had been identified as "moderate", were not dramatic. Trends, if any, will become apparent only as additional data are collected in the future.

Discussion “Undegraded” means that the benthic animals found at a site are similar in number and type of species to those expected in an undisturbed site in that region. “Degraded” means that the animals found are quite different from those at a reference site, reflecting one or more negative influences.