**12. Final remarks**

Many are the factors that determine the final destiny of complex oil molecules in the marine ecosystem. Coastal habitats (lagoons, coral; reefs, marsh; and lands, mangroves), open waters, and seabed are vulnerable to oil contaminants due to lasting effects of toxic compounds incorporated in the trophic web or deposited in shallow and deep sediments. Our research revolved around two major premises: (a) the existence of trans-boundary pollutants in the GoM and (b) the high connectivity of oceanographic processes within the GoM. For Mexico, these two concepts are essential in understanding the potential environmental consequences of a massive oil spill in its EEZ and shoreline. The above two conditions facilitate the active transport of contaminants across different sectors of the Gulf. There are no physical barriers or other sort of factors that impede the free passage from the US waters toward Mexico's EEZ and vice versa. Migratory species (trans-boundary species) and planktonic larvae take advantage of the ocean circulation to extend their fundamental niche (growth-reproduction-nutrition) within the Gulf, regardless of international legal boundaries.

During the 3-year monitoring program in Mexico's EEZ in the aftermath of a major oil spill in the northern Gulf of Mexico caused by the Deepwater Horizon event in April of 2010, our research efforts focused on the assessment of crude oil compounds in water, sediments, plankton, and benthos of the NW Gulf. The highconnectivity and the trans-boundary mechanisms that facilitate the dispersion of larvae and pollutants within the GoM were the essential premises in examining the far-field effects of the DWH oil spill in Mexican waters. Therefore, it was doubtful that the DWH harmful effects were confined to a restricted area near the Macondo's wellhead.

The information contained in this chapter is an excellent baseline environmental data from more than 35 hydrographic variables, biogeochemical and biological properties of the benthic and pelagic ecosystems of the continental shelf, and the upper slope of the NW Gulf of Mexico. The analyses and interpretation so far achieved in this first multidisciplinary effort do serve to recognize the significant alterations in the sedimentary quality standards and the risk of harmful effects on benthic organisms, attributable to anthropogenic factors.

The lack of knowledge on the long-term environmental damage compels us to implement innovative research approaches. If we consider the short-term monitoring operations, it is necessary to adjust the network of observation sites and optimize the number of variables focusing on the detection of toxic elements in water, sediment, and the trophic web. In a long-term scenario, it is essential to continue with multidisciplinary monitoring programs involving research vessels and stationary observational buoys.
