Exploring the Impacts of Urbanization on Stream Food Webs: Does Urbanization Affect Periphyton Abundance and Composition?
Periphyton is a key component of stream food webs because the organisms and detritus within the matrix represent important sources of organic matter for higher trophic levels. The abundance and composition of organisms that constitute periphyton is, in part, a function of water quality and light availability. In many locations, water quality is being modified by urbanization in ways that may impact the quantity and quality of periphyton as a food source. For instance, urbanization typically involves reductions in tree cover and proliferation of impervious surfaces that togethermay increase irradiance, nutrient inputs, and water temperatures in streams, conditions that commonly favor growth of filamentous Chlorophytes. Such changes can be important for stream fauna because the community composition also affects the nutritional value and palatability of periphyton. We sampledperiphyton along a gradient of urbanization in 12streams throughout Cobb and Paulding County, GA todetect patterns in standing stock and community structure. We sampled 6 different transects along a reach within each stream and quantified total chlorophyll, biomass, and relative abundance of algaltaxa. Preliminary results indicate that algal abundance was dominated by a diversity of species within theBacillariophyceae, Cyanophyta and Chlorophyta. Comparisons will also be made of the total chlorophyll and biomass among the streams to determine if urbanization affects the quality and quantity of food available along a gradient of urbanization.
1 Kennesaw State University; 2 Kennesaw State University; 3 Kennesaw State University
Univariate and Multivariate Assessment of Habitat Preferences of Stream Fishes
Urbanization alters physical habitat in streams and has been implicated as a factor leading to reduced fish diversity in urban streams. Evaluating the importance of habitat alteration requires an understanding of fishes’ preferred habitats and the appropriate scale of measurement to use in assessing those habitat features. The purpose of this study is to assess two different approaches for quantifying fish habitat preferences to determine which most adequately characterizes habitat use compared to expected patterns determined from the literature. Fish were collected at 12 sites from streams in the lower Etowah River Basin using backpack electroshockers. At each site, the study reach was divided into six sections of equal length and fish from each section were identified and counted. Water depth, water velocity and substrate composition were assessed at six randomly selected points in each of the six sections. Habitat preferences for three species, Lepomis auritus, Percina nigrofasciata and Campostoma oligolepis were estimated using a univariate approach where depth, velocity and substrate were treated separately and a multivariate approach where the three habitat variables were combined into a series of coded categories. The univariate approach produced habitat relationships that corresponded poorly to literature descriptions of the preferred habitat of the three species. In contrast, the multivariate approach produced habitat relationships similar to those found in literature descriptions of the preferred habitat of the species. Our results suggest that fish are responding to interactions among the measured habitat variables and a univariate approach to habitat description has limited utility.
P52 • Lindsay J. Brooks1, Joshua W. Campbell1, Julie W. Murphy2
Bioaccumulation of Total Mercury in Wilson Snipe (Gallinago delicata) From Alabama
Mercury is a persistent toxic heavy metal that can bioaccumulate in organisms causing diseases and other health problems. Higher trophic level birds have been shown to be sensitive to toxins in their environment. Wilson’s snipe (Gallinago delicata) feed primarily on aquatic invertebrates and many of these aquatic ecosystems are prone to mercury bioaccumulation. In this study we measured total mercury (Hg) in the Wilson’s snipe to determine whether this bird species could be used as a biological indicator for mercury bioaccumulation. Total mercury was measured in the feathers and muscle tissue. Mean concentration (ppm) of mercury was 1.33 ppm and 0.0874 ppm in the feathers and muscle tissue respectively. Mercury concentration (ppm) was significantly higher in feathers compared to muscle tissue (P = 0.0002). Our data suggests that the Wilson’s snipe, an aquatic invertebrate predator, does bioaccumulate mercury from their environment and could be a useful biological indicator for mercury.
1 High Point University; 2 Coastal Carolina University
P53 • Somuayiro N. Nwokike, Rebecca L. Tucker, Benjamin C. Webster, Matthew N. Waters, Gretchen K. Bielmyer
The Effects of Water Quality, Habitat and Land Use on the Biodiversity of Stream Macroinvertebrates in South Georgia
Macroinvertebrates are good indicators of stream health for localized aquatic ecosystems. Previous work shows that water quality, habitat and surrounding land use impact macroinvertebrate community structure inhabiting the streams. We sampled macroinvertebrates from four streams of different order and land use located in Lowndes County, South Georgia. The Withlacoochee River is order 4 with forest/ag/urban land use. The Little River is order 3 with forest/ag land use. Sugar Creek is order 2 with urban/forest land use, and One Mile Branch is order 1 with urban land use. Specimens were trapped using kick nets and hand collection techniques; then identified and placed into specific pollution resistant groups to determine stream health. Each stream’s biodiversity and Beck’s Index were later recorded. Despite differences in land use and stream order, these four streams are considered healthy according to Beck’s Index and other stream health indices. It was found that pollution resistant macroinvertebrates were seldom seen; however when they were found, Becks Index for that sample dropped dramatically and the sampling’s overall health had a negative drop. When the biodiversity was high, the stream’s health score was positive as well. Biodiversity showed to have a strong correlation with the stream health. Despite different orders and land use, these streams all contained complex heterogeneous habitats with sufficient substrate for biofilm production. This habitat complexity could provide the mechanism for healthy stream scores.
Dept of Biology, Valdosta State University, Valdosta, GA
P54 • Leanna R. Tacik, Annie Choi, Andreas N. Gregoriou, Carly Martin, Kaitlyn D. Peters, Kenneth Fortino
