**1.1 Research guidelines and observational strategy**

 Mexico, as a neighboring country of the USA, and Cuba, shares a vast ocean space in the GoM, bounded by 200 miles known as the EEZ. Under the international Treaty Law of the Sea, coastal countries are held accountable for the preservation and study of biotic and natural resources such as minerals, contained in both its waters as in the marine seabed. Based on this precept, and by the seriousness that represented the spill of fossil hydrocarbons introduced to the marine ecosystem of the GoM, it was imperative to implement a program of systematized oceanographic observations. Such program would contribute to build a dependable database of environmental parameters and thus carry out an assessment of environmental damage in the short term and midterm. Under the rules of international law [12], Mexico is obliged to have reliable information on the sources and the kinds of contaminants to assess the physical damage to coastal and ocean ecosystems in the GoM.

 This chapter presents to the reader a synthesis of the most outstanding features of a 3-year research program of oceanographic observations (MARZEE) on the continental and upper slope off the coasts of the states of Tamaulipas and Veracruz during the period of 2010–2012. Considering the early dispersion forecasts of crude oil leaks originating from the north of the GoM, there was a high risk that the coast of the above states would be impacted by crude oil, preferably in the winter. To anticipate this potential anthropic disturbance, a monitoring program was implemented whose observational strategy included the sampling of 35 abiotic and biotic variables. Water, sediment, and biota from the continental shelf (50–183 m) and upper slope (200–>2000 m) were obtained in the summer of 2010 (M-I), and the winter of 2011 (M-II), and 2012 (M-III).
