Water quality of small seasonal wetlands in the Piedmont ecoregion, South Carolina, USA: Effects of land use and hydrological connectivity Xubiao Yu a,b , Joanna Hawley-Howard c , Amber L. Pitt d , Jun-Jian Wang b , Robert F. Balddin c , Alex T. Chow b,c,* a School of Chemistry and Chemical Engineering, South China University of Technology, 510640, China b The Belle W. Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC 29440, USA c Department of Forestry and Environmental Conservation, Clemson University, Clemson, SC 29634, USA d Department of Biological & Allied Health Sciences, Bloomsburg University of Pennsylvania, Bloomsburg, PA 17815, USA article info Article history: Received 2 June 2014 Received in revised form 29 December 2014 Accepted 5 January 2015 Available online 13 January 2015 Keywords: Dissolved organic matter Fluorescence Isolated wetlands Nutrients abstract Small, shallow, seasonal wetlands with short hydroperiod (2e4 months) play an important role in the entrapment of organic matter and nutrients and, due to their wide distribution, in determining the water quality of watersheds. In order to explain the temporal, spatial and compositional variation of water quality of seasonal wetlands, we collected water quality data from forty seasonal wetlands in the lower Blue Ridge and upper Piedmont ecoregions of South Carolina, USA during the wet season of February to April 2011. Results indicated that the surficial hydrological connectivity and surrounding land-use were two key factors controlling variation in dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in these seasonal wetlands. In the sites without obvious land use changes (average developed area <0.1%), the DOC (p < 0.001, t-test) and TDN (p < 0.05, t-test) of isolated wetlands were significantly higher than that of connected wetlands. However, this phenomenon can be reversed as a result of land use changes. The connected wetlands in more urbanized areas (average developed area ¼ 12.3%) showed higher concentrations of dissolved organic matter (DOM) (DOC: 11.76 ± 6.09 mg L 1 , TDN: 0.74 ± 0.22 mg L 1 , mean ± standard error) compared to those in isolated wetlands (DOC: 7.20 ± 0.62 mg L 1 , TDN: 0.20 ± 0.08 mg L 1 ). The optical parameters derived from UV and fluorescence also confirmed significant portions of protein-like fractions likely originating from land use changes such as wastewater treatment and livestock pastures. The average of C/N molar ratios of all the wetlands decreased from 77.82 ± 6.72 (mean ± standard error) in February to 15.14 ± 1.58 in April, indicating that the decomposition of organic matter increased with the temperature. Results of this study demonstrate that the water quality of small, sea- sonal wetlands has a direct and close association with the surrounding environment. © 2015 Elsevier Ltd. All rights reserved. * Corresponding author. The Belle W. Baruch Institute of Coastal Ecology and Forest Science, 130 Heriot Road, Georgetown, SC 29440, USA. Tel.: þ1 843 546 1013x232; fax: þ1 843 546 6296. E-mail address: achow@clemson.edu (A.T. Chow). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/watres water research 73 (2015) 98 e108 http://dx.doi.org/10.1016/j.watres.2015.01.007 0043-1354/© 2015 Elsevier Ltd. All rights reserved.