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EFFECTS OF SPATIAL EXTENT ON LANDSCAPE STRUCTURE AND SEDIMENT METAL CONCENTRATION RELATIONSHIPS IN SMALL ESTUARINE SYSTEMS OF THE US MID-ATLANTIC COAST
Citation:
HOLLISTER, J. W., P. V. AUGUST, AND J. F. PAUL. EFFECTS OF SPATIAL EXTENT ON LANDSCAPE STRUCTURE AND SEDIMENT METAL CONCENTRATION RELATIONSHIPS IN SMALL ESTUARINE SYSTEMS OF THE US MID-ATLANTIC COAST. LANDSCAPE ECOLOGY. Springer, New York, NY, 23:91-106, (2008).
Impact/Purpose:
This manuscript is one of many AED and EPA contributions to the supplemental issue, largely funded by AED, of the Journal Landscape Eclogy which is dedicated to papers addressing coastal and marine applications of Landscape Ecology. The Article describes the variation in relationships between estuarine sediment metal concentrations when linked to portions of the landscape at various distances from an EMAP sampling station. The primary impact of this article is a better description of the role of scale in understanding the linkages between ecological condition, specifically the condition of estuaries, and the landscape. Furthermore, the article serves to inform current and future work within EPA and ORD on the utility of probabilistic samples, such as those collected by EMAP and NCA, in identifying specific impaired waterbodies (i.e. 305(b) to 303(d)).
Description:
Prior studies exploring the quantitative relationship between landscape structure metrics and the ecological condition of receiving waters have used a variety of sampling units (e.g. a watershed, or a buffer around a sampling station) at a variety of spatial scales to generate landscape metrics resulting in little consensus on which scales best describe land-water relationship. Additionally, the majority of these studies have focused on freshwater systems and it is not clear whether results are transferable to estuarine and marine systems. We examined how sampling unit scale controls the relationship between landscape structure and sediment metal concentrations in small estuarine systems in the Mid-Atlantic region of the United States. We varied the spatial extent of the contributing watersheds used to calculate landscape structure and assessed linear relationships between estuarine sediment metal concentrations and the total area of developed and agricultural lands at each scale. Area of developed lands was consistently related to sediment metals while total agricultural land was not. Developed land had strongest associations with lead and copper; weakest with arsenic and chromium; and moderate associations with cadmium, mercury, and zinc. Local (i.e., less than 15-20 km from a sampling station) land uses have a greater impact than more distant land uses on the amount of toxic metals reaching estuarine sediments.