**4. The coastal region of the department of Magdalena**

The coastal marine zone of the Department of Magdalena is located between 11°15′33″ N and 73°34′48″ W on the border with the Department of La Guajira and 11°05′42″ N and 74°50′55″W, in Bocas de Ceniza, on the eastern bank of the Magdalena River. There is a great diversity of ecosystems, from sandy beaches, coral reefs, seagrasses, mangroves, rocky coastlines, and sedimentary bottoms, which are considered strategic for the region and the country and provide environmental goods and services that influence the culture. and the economy of the human population of the department, due to its importance in tourism, fishing, and port activities. This region is influenced by the presence of the Sierra Nevada de Santa Marta (SNSM) in which numerous rivers are born and flow into the coastal area of the department and determine the structure of the coast in a series of cliffs and bays.

The outer delta of the Magdalena River is located on the western side of the strip, giving shape to the Ciénaga Grande de Santa Marta (CGSM), the largest

*Mercury in the Colombian Caribbean: The Bay of Cartagena, A Model in Resilience DOI: http://dx.doi.org/10.5772/intechopen.107240*

lagoon-coastal system in the country and in which the Magdalena River and several rivers from the SNSM interact, and the surrounding seawater.

Even though numerous studies on marine pollution have been carried out on this coastal strip, there are few in which Hg content has been measured. Since 2000, the Marine and Coastal Research Institute [10] has been leading the "Diagnosis and Evaluation of the Quality of Marine and Coastal Waters in the Colombian Caribbean and Pacific" program, with the participation of several government entities (CARs: Autonomous and Regional Corporations), only in the period between June and November 2017 and between February and July 2018, determinations of Hg content in sediments were made [11]. The content of Hg in sediments from 18 points along the coastal strip of the department and during the two sampling periods (rainy 2017 and dry 2108) was determined. The contents fluctuated between values lower than the detection limit of the method (<3.0 ngHg g−1 p.s.) up to 496 ngHg g−1 p.s. During the rainy season, the contents were low and in nine of the stations, the presence of Hg was not detected, while in the dry season it could be measured in most of the stations. The highest contents were determined in the Bay of Santa Marta and the highest value corresponding to the station in the north of the bay near the cabotage dock of the port of Santa Marta (205 in the rainy season and 296 ngHg g−1 d.w., in the dry season) and 192 ngHg g−1 p.s. at the south bay station.
