Relationships between watershed Stressors and sediment contamination in Chesapeake Bay estuaries

Three methods for assessing the relationships between estuarine sediment contaminant levels and watershed Stressors for 25 Chesapeake Bay sub-estuaries were compared. A geographic information system (GIS) was used to delineate watersheds for each sub-estuary and analyze land use pattern (area and location of developed, herbaceous and forested land) and point source pollution (annual outflow and contaminant loading) using three landscape analysis methods: (1) a watershed approach using the watershed of the estuary containing the sampling station. (2) a ‘partial watershed’ approach using the area of the watershed within a 10 km radius of the sampling station and (3) a ‘weighted partial watershed’ approach where Stressors within the partial watershed were weighted by the inverse of their linear distance from the sampling station. Nine sediment metals, 16 sediment organics and seven metals loading variables were each reduced to one principal component for statistical analyses. Relationships between the first principal components for sediment metals and organics concentrations and watershed stressor variables were analyzed using rank correlation and stepwise multiple regression techniques. For both metals and organics, the watershed method yieldedR2 values considerably lower than the partial and weighted partial watershed analysis methods. Regression models using Stressor data generated by the weighted partial watershed landscape analysis method explained 76% and 47% of the variation in the first principal component for sediment metals and organics concentrations, respectively. Results suggest that the area of developed land located in the watershed within 10 km of the sediment sampling station is a major contributing factor in the sediment concentrations of both metals and organics.

[1]  P. Pacheco,et al.  Point source methods document , 1993 .

[2]  Michael Elliott,et al.  Managing troubled waters—The role of marine environmental monitoring , 1991 .

[3]  R. O'Neill,et al.  A factor analysis of landscape pattern and structure metrics , 1995, Landscape Ecology.

[4]  T. J. Breen,et al.  Biostatistical Analysis (2nd ed.). , 1986 .

[5]  I. Schlosser,et al.  Water Resources and the Land-Water Interface , 1978, Science.

[6]  Bruce T. Milne,et al.  Effects of changing spatial scale on the analysis of landscape pattern , 1989, Landscape Ecology.

[7]  Fred D. Calder,et al.  Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments , 1995 .

[8]  J. Neter,et al.  Applied linear statistical models : regression, analysis of variance, and experimental designs , 1974 .

[9]  J. Benforado,et al.  Water Quality Functions of Wetlands: Natural and Managed Systems , 1988 .

[10]  Chesapeake Bay Program.  Chesapeake Bay Basin Toxics Loading and Release Inventory , 1999 .

[11]  Gerald J. Niemi,et al.  The cumulative effect of wetlands on stream water quality and quantity. A landscape approach , 1990 .

[12]  Donald E. Weller,et al.  Nutrient flux in a landscape: Effects of coastal land use and terrestrial community mosaic on nutrient transport to coastal waters , 1992 .

[13]  John R. Clark,et al.  Wetland Functions and Values: The State of Our Understanding , 1981 .

[14]  D. Correll,et al.  Nutrient dynamics in an agricultural watershed: Observations on the role of a riparian forest , 1984 .

[15]  Elgene O. Box,et al.  Scale Effects in Landscape Studies , 1987 .

[16]  Michael F. Goodchild,et al.  GIS and hydrologic modeling. , 1993 .

[17]  Gerald J. Niemi,et al.  Wetland effects on lake water quality in the Minneapolis/St. Paul metropolitan area , 1993, Landscape Ecology.

[18]  M. Wehde.  Grid cell size in relation to errors in maps and inventories produced by computerized map processing , 1982 .

[19]  R. Iman,et al.  Rank Transformations as a Bridge between Parametric and Nonparametric Statistics , 1981 .

[20]  J. H. Zar,et al.  Biostatistical Analysis (5th Edition) , 1984 .

[21]  L. F. Marcus,et al.  A survey of multivariate methods for systematics , 1980 .

[22]  K. Lajtha,et al.  Couplings of watersheds and coastal waters: Sources and consequences of nutrient enrichment in Waquoit Bay, Massachusetts , 1992 .

[23]  E. K. Anderson,et al.  Land use and land cover digital data , 1983 .

[24]  S. Ventura,et al.  Large-scale modeling of urban nonpoint source pollution using a geographic information system , 1993 .

[25]  D. Whigham,et al.  Impacts of freshwater wetlands on water quality: A landscape perspective , 1988 .

[26]  Michael J. Wiley,et al.  Empirical relationships between land use/cover and stream water quality in an agricultural watershed , 1988 .

[27]  Derek A. Roff,et al.  DISTRIBUTION-FREE AND ROBUST STATISTICAL METHODS: VIABLE ALTERNATIVES TO PARAMETRIC STATISTICS? , 1993 .

[28]  Michael L. Morrison,et al.  Wildlife-habitat relationships : concepts and applications , 1993 .