Long term state of coastal lagoons in Veracruz, Mexico: Effects of land use changes in watersheds on seagrasses habitats Nadia E. Rivera-Guzmán a , Patricia Moreno-Casasola a, * , Silvia E. Ibarra-Obando b , Vinicio J. Sosa a , Jorge Herrera-Silveira c a Functional Ecology Department, Instituto de Ecología, A.C., Carretera Antigua a Coatepec No 351, El Haya, Xalapa, Veracruz C.P. 91070, Mexico b Marine Ecology Department, CICESE, Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860 Ensenada, Baja California, Mexico c Ocean Resources Department, CINVESTAV-IPN, Unidad Mérida Carretera Antigua a Progreso km. 6, C.P. 97310 Mérida, Yucatán, Mexico article info Article history: Available online abstract An increase in population over the last 50 years along the central coast of Veracruz on the Gulf of Mexico has led to a corresponding intensification of agriculture, urbanization, and other economic activities. Most significantly, this has resulted in rapid changes of land use and an increase in the area dedicated to agriculture and livestock. Native coastal wetland vegetation has declined significantly, and coastal la- goons systems are altered as they receive excess nutrients and sediments from agricultural and economic activities. The aim of this study was to evaluate the influence of productive activities on four coastal lagoons and one estuary at the watershed level and to establish reference points or ecological indicators upon which future changes in coastal wetlands may be measured. For this purpose we analyzed the physico-chemical characteristics of the water column, assessed the abundance and biomass of sea- grasses, and determined the historical and current trophic status of these coastal water bodies. Our results indicate that over time the lagoons have remained in a eutrophic state, and only one has become mesotrophic. The biomass of the seagrass Halodule wrightii decreased by 28% from 1991 to 2001 in La Mancha Lagoon. Our results provide a baseline to assess future changes in the water quality of the selected study sites and the seagrasses populations they contain. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The coastal zone represents a unique domain of gradient- dependent ecosystems, climate, geomorphology, human habita- tion, and regimes of highly dynamic physical, chemical, and bio- logical processes. The resource richness and diversity of coastal areas have led to an increase in human population along the coasts and estuaries throughout the world and a concomitant increase in productive activities (Crossland et al., 2005). Coastal degradation has occurred to a greater extent in developing countries due to rapid population growth and disorganized urbanization (Linden, 1990). Human activities involving the physical removal or destruction of habitat are the most obvious forms of ecosystem alteration (Linden, 1990), and estuarine habitats, such as salt marshes, mangrove forests, and seagrass beds (Orth et al., 2006), are among the most affected. Coastal lagoons and estuaries can also be at the receiving end of urban and industrial wastewater discharge, agri- cultural runoff, and seepage into groundwater, all of which promote an increase in nutrients and lead to eutrophication (Aranda Cicerol et al., 2011). This outcome is associated with human settlements, industry, and the use of fertilizers around the lagoons. Seagrasses are considered valuable biological indicators because they have high light requirements and are highly responsive to environ- mental changes, especially those that alter water quality, including nutrient and sediment inputs (Koch, 2001). Eutrophication favors the rapid growth of macro- and microalgae, leading to competition for light and nutrients between algae and seagrasses, eventually causing the disappearance of seagrasses (Dunton, 1990). Short and Wyllie-Echeverria (1996) found that between 1970 and 1982, 50% of the seagrass loss worldwide could be attributed to natural dis- turbances like hurricanes, coastal erosion, grazing, and diseases, and the other 50% was caused by anthropogenic perturbations such as dredging, oil spills, and reductions in water quality. Between 1983 and 1994, about 90 000 ha of seagrass loss was documented mainly in the United States and Australia. Similarly, a reduction of seagrass cover by 58% in shallow beds along the Swedish coast took place between 1980 and 2000 (Baden et al., 2003). * Corresponding author. E-mail address: patricia.moreno@inecol.mx (P. Moreno-Casasola). Contents lists available at ScienceDirect Ocean & Coastal Management journal homepage: www.elsevier.com/locate/ocecoaman 0964-5691/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ocecoaman.2013.10.007 Ocean & Coastal Management 87 (2014) 30e39