Nutrient water quality in a tropical coastal zone with groundwater discharge, northwest Yucata ´n, Mexico Nancy ArandaCirerol a,c, * , Jorge A. Herrera-Silveira a , Francisco A. Comı ´n b a Departamento de Recursos del Mar, CINVESTAV-IPN Me ´rida, A.P. 73 Cordemex, 97310 Me ´rida, Yucata ´n, Mexico b Instituto Pirenaico de Ecologı ´a, Campus Aula Dei, Av. Montan ˜ ana 1005, A.P. 202, 50080 Zaragoza, Spain c Departament de Ecologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain Received 20 January 2005; accepted 1 February 2006 Available online 26 May 2006 Abstract This work is the beginning of a coastal water quality monitoring program to establish the baseline for the implementation of an integrated coastal management of the Yucata ´n Peninsula tropical ecosystem. Coastal water quality is affected by the increasing economic development. This area has no rivers because of its karst geomorphology, and the coastal freshwater comes from springs or seeps. Coastal water quality was studied in four towns from January to December 2000. Statistically significant differences among water quality variables and processes are discussed. Along with groundwater discharge, domestic and shrimp farming sewage are the main sources of nutrients, predominantly of nitrogen and silica. Salinity dilution is used to estimate the groundwater fraction that influences each area in northwestern Yucata ´n. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: nutrient water quality; groundwater; Yucata ´n; nitrate contamination; eutrophication; nutrients 1. Introduction Environmental problems generated by nutrient enrichment are now a well-established fact, as seen in the Baltic Sea, Black Sea, Adriatic Sea, Gulf of Mexico, Chesapeake Bay, San Francisco Bay, and other places where water quality has been altered by eutrophication (Rabalais, 1999; Cloern, 2001; Moncheva et al., 2001; Wasmund et al., 2001; Dell’Anno et al., 2002; Penna et al., 2004). Nutrient sources are surface discharges from rivers, runoff from agricultural areas, domestic and industrial wastes, atmo- spheric deposition, and groundwater (Rosenberg, 1990; Rossi et al., 1992; Vitousek et al., 1997; Rabalais, 1999; de Jonge et al., 2002). Atmospheric deposition and groundwater, which potentially modify the primary production and dynamics of al- gal blooms, are often overlooked (Valiela et al., 1992; Paerl, 1997; Pryor and Barthelmie, 2000; Burnett et al., 2001, 2003; Whitall et al., 2003). In some coastal areas, groundwater discharges are similar in magnitude to those of rivers, there- fore, extending their influence to a greater spatial scale (Moore, 1996; Burnett et al., 2003; Thorburn et al., 2003), like in Tampa Bay and Florida Bay, where groundwater is an important nitrogen source (Jickells, 1998; Wang et al., 1999; Sutula et al., 2001). Mexico is not an exception, and research on water quality is a priority (Pa ´ez-Osuna et al., 1998; INE, 2000; ArandaCirerol, 2001; Rivera-Arriaga and Villalobos, 2001). The Yucata ´n Pen- insula, located in east Mexico, is a tropical region with no rivers. Groundwater discharges on the coast, as either springs or seepage, due to the highly permeable and porous carbonate karst geology (Logan, 1969; Capurro and Reid, 1972; Han- shaw and Back, 1980; Back and Lesser, 1981; Pope et al., 1991). Continental nutrient sources are important, since waste treatment systems began only 10 years ago and are not yet completely efficient (ArandaCirerol, 2001, 2004); thus, groundwater is contaminated with nitrates (Pacheco and Cab- rera, 1997; Graniel et al., 1999; ArandaCirerol, 2004). Conti- nental nutrient sources come e in order of importance e from * Corresponding author. E-mail address: arandacirerol@gmail.com (N. ArandaCirerol). 0272-7714/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecss.2006.02.015 Estuarine, Coastal and Shelf Science 68 (2006) 445e454 www.elsevier.com/locate/ecss