Seston dynamics in a saline Mexican lake

Organic and inorganic matter in aquatic ecosystems may occur in both dissolved and particulate form. Seston is the particulate matter present in the water column that is composed of 2 fractions: organic and inorganic matter (MARGALEF 1983, WETZEL 1983). Inorganic matter could be lithogenic (clay and silt), biogenic (silica), andlor originated by chemical precipitation (carbonates) (EFFLER et al. 2002, PENG & EFFLER 2005). The study of seston mass and composition is important to understanding the dynamics of the organic and mineral matter (PUNNING et al. 2003). Previous studies from a wide diversity of geographic regions covering temperate and tropical zones report organic matter as the most abundant fraction of seston, predominantly particulate organic carbon that exhibits seasonal dynamics similar to those of chlorophyll a (CALLIERI 1997, JÃRVINEN et al. 1999, BRZÁKOVÁ et al. 2003, PUNNING et al. 2003); however, the seston of some lakes, such as Lake Maggiore, could be dominated by the inorganic fraction during certain periods (CALLIERI 1997). Although previous studies on warm, monomictic Lake Alchichica relate to dynamic aspects such its hydrodynamics (ALcOCER et al. 2000), nutrient concentration (SÁNCHEZ SILVA 2006), and phytoplankton biomass (SÁNCHEZ REYES 2001), the dynamics ofthe seston concentration, distribution, and composition was unknown. The purpose of this investigation was to analyze the seasonal and vertical variation of seston in Lake Alchichica to better understand the organic and inorganic matter dynamics in tropical, saline lakes.