From evidence of exotic nutria damage to wetlands to above average sea level rise, the Chesapeake Bay watershed is a complex and compelling scientific challenge. Methods and findings pertaining to these and other issues are presented by USGS scientists in poster sessions at the Chesapeake Bay Federally Supported Science Meeting, Patuxent Wildlife Research Center, Laurel, Md., Dec. 9-10, 1998.
Rising Sea Level in Chesapeake Bay Exceeds World Rates
Tide gauges for the Chesapeake Bay and the Mid-Atlantic coast show rates of sea level rise that are twice the worldwide average. Scientists disagree on the cause of the recent increase. USGS scientists are conducting research to try and address the question of the rate of sea level rise in the Chesapeake Bay and what it means for the environment and society. They are trying to find out if the increase is caused by land subsidence, or if it is related to a changing climate and ocean volume, and whether or not human activities account for some part of the changes. The USGS role in sea-level research is national in scope and ranges from remote sensing and geologic mapping of wetlands to studies of coastal erosion and evidence of older shorelines in the geologic record. In the Chesapeake region, the effort is focused on reconstructing the detailed pattern of relative sea-level change during the last 6,000 to 8,000 years. This has involved a number of activities including remote sensing and extracting core samples of marshes and tributary creeks in the Patuxent River basin to provide sedimentary and biological records of rising sea level. ("Rising Sea Level in Chesapeake Bay," by Curtis E. Larsen, and Martha Herzog, Reston, Va.)
South American Nutria Destroy Marsh Habitat
USGS scientists believe that the habits of nutria, an exotic rodent that has invaded Chesapeake Bay wetlands, are apparently accelerating marsh loss in the bay region. Preliminary findings indicate that overpopulation is the key factor in the nutrias' destructive foraging patterns. Through a collaborative partnership with the state of Maryland and the USFWS (U.S. Fish and Wildlife Service), USGS scientists are investigating the role of nutria in the extensive loss of emergent marsh at the Blackwater National Wildlife Refuge located on the Eastern Shore of Maryland. The experimental study is using large fenced plots (exclosures) to determine whether removal of nutria can stabilize or recover marsh vegetation. Twenty experimental plots were placed in the marsh requiring 1.5 miles of fencing; an additional 38 unfenced control plots also were established. Researchers are monitoring the effects on vegetation through direct fall and spring measurement of selected subplots supplemented by aerial photography of whole plots. ("The Effect of Nutria (Myocastor Coypus) on Marsh Loss in the Lower Eastern Shore of Maryland: Exclosure Study," by Michael Haramis, USGS, Laurel, Md. and Robert Colona, Maryland Department of Natural Resources, Annapolis, Md.)
Radio Tracking of Migrant Game Birds
USGS wildlife research scientists have partnered with the USFWS, the Maryland National-Capital Park and Planning Commission, and the State of Maryland to investigate the ecology and status of the sora rail, an important game bird. Each fall, thousands of soras make a migration stopover in the fresh-tidal marshes of the Chesapeake Bay. The rails favored historic stopover site in the region has been the wild rice marshes bordering the tidal Patuxent River. The principal investigative technique researchers are using to study the sora rail stopover ecology and migration characteristics are large-scale bandings and radio telemetry. The tracking and observational procedures are described in the poster. ("Length of Stay, Survival, Habitat Use, and Migration Characteristics of Fall Migrant Soras on The Patuxent River Marsh As Determined By Radio Telemetry," by Michael Haramis, USGS, Laurel, Md. and Gregory D. Kearns, Maryland National-Capital Park and Planning Commission, Upper Marlboro, Md.)
The Tree Swallow as Sentinel for PCBs in Aquatic Sediments
Tree swallows are being used by USGS scientists as an indicator species for PCB (polychlorinated biphenyl) contamination at small inland sites in the Chesapeake Bay region. USGS researchers selected tree swallows because they are geographically widespread, can be attracted to nestboxes, have limited feeding areas, and are likely to be exposed to PCBs due to a pattern of feeding on aquatic insects whose habitat includes contaminated sediments. Researchers investigated seven locations in the Chesapeake Bay watershed with differing levels of PCB contamination by comparing foodstuff, egg and nestling carcass concentrations of PCBs to sediment PCB concentrations in those areas. Although the tree swallow is proving effective as a sentinel for sediment PCBs that can enter the food chain, PCB concentrations found at the study sites so far have not been high enough to cause obvious harm. ("The Tree Swallow (Tachycineata bicolor) as a Sentinel Species for Sediment Contaminant Presence, Bioavailability and Effect in the Chesapeake Bay Watershed," by Mark J. Melancon, Amy L.Yorks Kutay, Craig S. Hulse, Barnett A. Rattner and David J.Hoffman, USGS, Laurel, Md.)
Measuring the Biological Well Being of Restored Wetlands
This poster explains the process used by USGS scientists for creating a streamlined set of biological criteria, referred to as an index of biotic integrity (IBI), for assessing the health of a particular type of wetland, and to demonstrate how the IBI will be used. This multi-disciplinary study supported by the EPA, National Resources Conservation Service, USFWS, and USGS, and is focused on creating the IBI for evaluating the condition of restored depressional wetlands located in agricultural areas on the Eastern Shore of Maryland. Unlike wetlands adjacent to larger bodies of water, depressional wetlands are typically located in upland areas. These wetlands are one of the most common wetland systems being restored. Although very different in composition and structure from the remnant natural depressional wetlands, which are typically forested or composed of scrub vegetation, the restored wetlands provide a variety of wetland functions that ultimately benefit the Chesapeake Bay. The IBI will use 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. ("Development of an Index of Biotic Integrity for Restored Depressional Wetlands on the Eastern Shore of Maryland," by Amy Deller, USGS, Laurel, Md. and Norman Melvin, NRCS, Wetland Science Institute, Laurel, Md.)
Sediment Ingestion May Be a Key to Waterfowl Risk Assessments
Although assessment of risks to wildlife from toxic metal contamination are generally based on the accumulation of environmental contaminants through food chains, USGS scientists are examing a more direct risk assessment approach that focuses on sediment contamination and not on the movement of metal through the food chain. Recent research suggests that to fully understand the exposure of waterfowl to heavy metals such as lead in the Chesapeake Bay, metal concentration in the sediment and the amount of sediment ingested by waterfowl should be assessed. Because the exposure route is so simple, the exposure to metal by swans should be directly proportional to the metal concentration in the sediments, making risk assessments simpler and more reliable. To begin validating this approach, forty-two mute swans were collected from unpolluted portions of central Chesapeake Bay in spring 1995, and their intestinal tracts and livers were analyzed for 13 metals including copper, lead, and zinc and for an acidic ash characteristic of sediment. Sediment samples also were analyzed for the same metals. The results suggest that comparative evaluation of sediment contamination levels and sediment ingestion accounts for virtually all of the lead ingested by mute swans. This finding suggests that this approach should be incorporated in ecosystem toxicological risk assessments of waterfowl. ("Relation of Lead Exposure to Sediment Ingestion in Mute Swans: A Chesapeake Bay Risk Assessment,"by W. Nelson Beyer, Daniel D. Day, Anna Morton, USGS, Laurel, Md., and Yakov Pachepsky, USDA, Beltsville, Md.)
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