Effects of Land Use and Land Cover on Freshwater Mussel Populations in the Upper Neuse River Basin, NC: A GIS Approach

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Title: Effects of Land Use and Land Cover on Freshwater Mussel Populations in the Upper Neuse River Basin, NC: A GIS Approach
Author: Andersen, Elizabeth F.
Advisors: Dr. Hugh Devine, Committee Chair
Dr. Jay Levine, Committee Member
Dr. Heather Cheshire, Committee Member
Abstract: Land use practices can adversely affect water quality and freshwater mussel populations. Water quality can become degraded by siltation from development, pesticides and nutrients from agricultural fields, heavy metals and other toxins from urban runoff. The relationship between land use/land cover and freshwater mussel populations was investigated in the upper Neuse River basin in North Carolina. Mussel surveys were conducted from April to August of 2001 in the Eno, Flat, Smith, New Light, and Little River watersheds. Surveys (n=44) were conducted along 300-m transects upstream and downstream of bridges to examine the effect of bridge crossing structures on mussel assemblages. Geographic Information Systems (GIS) hydrological modeling tools were used to delineate upstream catchments of each sample site and to determine drainage areas. GIS was used to quantify land use/land cover within multiple spatial areas: upstream catchment, upstream riparian buffers (100 m and 250 m widths), and local riparian buffers (100 m and 250 m widths) immediate to the sample sites. Other environmental variables included stream slope, road density, water chemistry, and habitat quality assessment scores. No significant differences (p< .05) between mean mussel abundances due to location (upstream or downstream), distance from the bridge, or their interaction were observed in a split plot block design analysis. However, a slight decline in abundance was observed within the first 50 m downstream of the bridge. Future studies in additional subbasins of the Neuse and/or in other river basins could show a significant decline. Detrended Correspondence Analysis (DCA) and Nonmetric Multidimensional Scaling (NMS) ordinations described some of the variation in the mussel community structure (67% and 46% total variation respectfully). Both of the ordinations yielded similar community structures and environmental gradients. Moderate associations (r>.5) were observed between DCA and NMS axis 1 and several environmental factors including drainage area, localized urban regions, and habitat scores. Strophitus undulatus (Creeper) and Pyganodon cataracta (Eastern Floater) were the most strongly associated species with ordination axis 1 and occurred in sites characterized by small drainage areas, small habitat quality assessment scores, and low percentages of urban land cover immediate to the site. A GIS-based proximity analysis examined the relationship between mussel populations and distance to the nearest land cover type (urban, forest, row crop agriculture and non-row crop agriculture). Linear regressions revealed significant relationships (p<.05) between mussel assemblages and non-row crop agriculture (r&#178;, = .11) and urban land uses (r&#178;, = .11), but accounted for only 11% of the total variability in each case. Further investigation is needed to determine the environmental factors that contribute to mussel community structure. The study sampling design selected for highly forested areas. Inclusion of more urbanized regions could yield very different results. The upper Neuse study area was characterized by high mussel abundance and species richness and could be compared to other subbasins in the Neuse or other watershed in future studies. Repeat visitation to the sample sites could also investigate temporal and seasonal variations in mussel populations.
Date: 2002-12-03
Degree: MS
Discipline: Natural Resources
URI: http://www.lib.ncsu.edu/resolver/1840.16/1135

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