Redefining the Seasons in the Terminos Lagoon Region of Southeastern Mexico: May Is a Transition Month, Not a Dry Month

The Terminos Lagoon is the largest estuary in Mexico, with numerous important animal and plant interrelationships. Its dominant feature is the largest mangrove surface in Latin America. A Natural Protected Area under Mexican law as well as an internationally recognized Ramsar site, this unique ecosystem is a frequent location for research projects concerning marine, wetlands, and terrestrial ecosystems. Located in the southern Gulf of Mexico and characterized by a tropical climate, the primary characteristic determining the region's meteorological seasons is the annual variation in rainfall. In 1982, an oft-cited article was published that defined the seasons as dry (February-May), wet (June-September), and an overlapping season of nortes'' or winter storms (October-March). Here evidence is presented, on the basis of an analysis of diverse meteorological parameters including 220 station-years of rainfall observations in the region, that May should be considered a transitional month, not part of the dry season. Because sampling and analysis protocols are often based on the definition of meteorological seasons, this result has implications for a wide range of environmental science research in the Terminos Lagoon region.