Diatom assemblages in a reservoir sediment core track land-use changes in the watershed

Journal of Paleolimnology, Sep 2015

Diatom assemblages in a 144-cm sediment core reliably chronicled watershed changes and modifications of a riverine water-source reservoir in northeastern Ohio (USA) between 1932 and 2005. Non-metric Multidimensional Scaling segregated diatom assemblages into six groups that correspond to known anthropogenic modifications in the watershed and reservoir: zone I (filling, 1932–1936), zone II (high farming activity, 1937–1949), zone III (declining farm activity and increased residential development, 1950–1976), zone IV (implementation of sewage bypass, 1977–1982), reduced development activity caused by economic recession, 1983–1993), zone VI (renewed population growth and construction of a dam extension, 1994–2005). Ten watershed and reservoir environmental variables (percent farmland, population, pH, total alkalinity, total hardness, transparency, surface area, air temperature, export of suspended solids, total phosphorus) were significantly correlated with diatom aggregate distribution in ordination space. Changes in species composition, in concert with watershed and reservoir changes, implicated light, alkalinity, and littoral macrophyte development as the primary drivers of diatom aggregate structure and function. Diatom productivity did not track nutrient loading (TP) and was likely driven by factors other than nutrients. Each zone was defined by a distinct set of environmental variables that differed from all other zones. Thus, diatom aggregate structure likely was determined by a dynamic suite of factors in the watershed and reservoir that had differential effects on diatom aggregate structure through time.

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Diatom assemblages in a reservoir sediment core track land-use changes in the watershed

Diatom assemblages in a reservoir sediment core track land-use changes in the watershed Lauren A. Schroeder . Scott C. Martin . G. Jay Kerns . Colleen E. McLean 0 1 2 3 0 G. J. Kerns Department of Mathematics and Statistics, Youngstown State University , Youngstown, OH 44555 , USA 1 S. C. Martin Department of Civil/Environmental and Chemical Engineering, Youngstown State University , Youngstown, OH 44555 , USA 2 L. A. Schroeder (&) Department of Biological Sciences, Youngstown State University , Youngstown, OH 44555 , USA 3 C. E. McLean Department of Geological and Environmental Science, Youngstown State University , Youngstown, OH 44555 , USA Diatom assemblages in a 144-cm sediment core reliably chronicled watershed changes and modifications of a riverine water-source reservoir in northeastern Ohio (USA) between 1932 and 2005. Non-metric Multidimensional Scaling segregated diatom assemblages into six groups that correspond to known anthropogenic modifications in the watershed and reservoir: zone I (filling, 1932-1936), zone II (high farming activity, 1937-1949), zone III (declining farm activity and increased residential development, 1950-1976), zone IV (implementation of sewage bypass, 1977-1982), reduced development activity caused by economic recession, 1983-1993), zone VI (renewed population growth and construction of a dam extension, 1994-2005). Ten watershed and reservoir environmental variables (percent farmland, population, pH, total alkalinity, total hardness, transparency, surface area, air temperature, export of suspended solids, total phosphorus) were significantly correlated with diatom aggregate distribution in ordination space. Changes in species composition, in concert with watershed and reservoir changes, implicated light, alkalinity, and littoral macrophyte development as the primary drivers of diatom aggregate structure and function. Diatom productivity did not track nutrient loading (TP) and was likely driven by factors other than nutrients. Each zone was defined by a distinct set of environmental variables that differed from all other zones. Thus, diatom aggregate structure likely was determined by a dynamic suite of factors in the watershed and reservoir that had differential effects on diatom aggregate structure through time. Reservoir; Diatom; Watershed quality; Anthropogenic impact; Sediment core - Riverine reservoirs provide many useful services including water for domestic and industrial use (Jørgensen et al. 2005). The value of these services depends on the quality of the impounded water. Initial water quality is determined by site conditions, i.e. geology, climate, hydrology and morphometry. Subsequently, water quality is subject to modification in response to changes in watershed land use. Unlike natural lakes, in which conditions prior to human impacts can serve as a benchmark for determining human impact on water quality (Bennion et al. 2011), reservoirs are usually constructed where watersheds have already been modified by human activities. Thus, reservoirs have no ‘‘pristine condition’’ as a reference for impairment. Reservoirs, from their inception, are subject to anthropogenic stresses. As a consequence, human activities in the watershed either improve or degrade the quality of the reservoir water by alleviating (Anderson et al. 2005) or intensifying stressors, respectively (Ke˛dziora 2003). Stressors external to the watershed may also affect water quality adversely, and include airborne nutrients and pollutants (Woodridge et al. 2014; Larsen 2000) and perhaps climate warming (McGowan et al. 2012). Because the highest standards apply to water used for domestic purposes and recreation, reservoirs constructed to provide these services are the most susceptible to impairment. Initial geological conditions are relatively stable over the lifetime of most riverine reservoirs. Therefore, with the exception of processes like climate warming, the magnitude and rate of degradation depends in large part on watershed use. Understanding the relationship between external stressors and water quality is necessary for effective lake and reservoir management (Battarbee and Bennion 2011). One way to identify these linkages is paleolimnological methods, often using diatom-based transfer functions to reconstruct past water chemistry and correlate such changes with shifts in land use, atmospheric deposition or climate (Smol 1992; Wolfe et al. 2001). Paleolimnological methods are powerful tools that have enhanced our understanding of ecological processes in lacustrine systems (Smol 1992, 2008; Battarbee 1999). There are, however, cases for which paleolimnology alone is inadequate to decipher linkages between watershed alterations and lacustrine ecological processes (Saros 2009). Recently there has been an appeal to integrate neo- and paleolimnological methods to discern relationships between watershed changes and ecological processes, and to use historical chemical data to validate pale (...truncated)


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Lauren A. Schroeder, Scott C. Martin, G. Jay Kerns, Colleen E. McLean. Diatom assemblages in a reservoir sediment core track land-use changes in the watershed, Journal of Paleolimnology, 2016, pp. 17-33, Volume 55, Issue 1, DOI: 10.1007/s10933-015-9860-4