Chesapeake Bay sea level rising at twice world average

The sea is rising in the Chesapeake Bay at twice the worldwide average according to a USGS study presented at the Chesapeake Bay Science Meeting on December 9 1998.

USGS scientists also presented studies examining the use of tree swallows as an indicator species for polychlorinated biphenyl (PCB) contamination; the creation of a set of biological criteria for the assessment of the health of wetland and the exposure of waterfowl to heavy metals through the ingestion of polluted sediment.

Tide gauges for the Chesapeake Bay and the mid-Atlantic coast show rates of sea level rise that are twice the worldwide average. USGS scientists do not as yet know what is causing the increase and are conducting research to find out if it is caused by land subsidence, or if it is related to changes to climate and ocean volume.

The USGS is attempting to reconstruct the pattern of relative sea-level change in the Chesapeake region, during the last 6,000 to 8,000 years. This involves the remote sensing and extraction of core samples of marshes and tributary creeks in the Patuxent River basin to provide sedimentary

and biological records of rising sea level.

USGS scientists are also using tree swallows as an indicator species for PCB contamination at small inland sites in the Chesapeake Bay region. Researchers selected tree swallows because they are geographically widespread, are easy to study and are likely to ingest PCBs via their diet of sediment-dwelling insects.

Researchers compared foodstuff, egg and nestling carcass concentrations of PCBs to sediment PCB concentrations in seven locations in the Chesapeake Bay watershed. PCB concentrations found at the study sites so far have not been high enough to cause obvious harm.

Another of the studies presented at the conference explains how USGS scientists created a set of biological criteria, known as an index of biotic integrity (IBI) to assess the health of a particular type of wetland.

This multi-disciplinary study focuses on the creation of an IBI for assessing the condition of restored depressional wetlands located in agricultural areas on the Eastern Shore of Maryland. Depressional wetlands are typically located in upland areas and are one of the most common wetland systems being restored.

The IBI uses community structure and species characteristics to assess the effects of human factors such as methods of wetland creation and surrounding land use on wetland health. This information will be useful to managers planning future restoration projects and to evaluate the biological integrity of existing restored wetlands.

Sediment ingestion accounts for virtually all of the lead ingested by mute swans in the Chesapeake Bay, according to another USGS study. This finding suggests that this approach should be incorporated in ecosystem toxicological risk assessments of waterfowl.

The study was conducted in order to ascertain to what extent waterfowl in the Chesapeake Bay are exposed to heavy metals via ingested sediment as opposed to through the food chain.

Because the exposure route is so simple, the scientists expected to find the exposure to metal by swans directly proportional to the metal concentration in the sediments, making risk assessments simpler and more reliable.

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