Holistic study of water quality in the littoral of Puerto San Carlos, Baja California Sur, Mexico

Physical, chemical and biological parameters were measured in March and November 2014. These water analyses were carried out at 22 sites on the coast of Puerto San Carlos (Magdalena Bay, Baja California Sur, Mexico), with the objective of assessing water quality and identifying possible sources of water pollution and its status according to Mexican regulations. The study area was divided into three zones according to its main activity: (1) thermoelectric power station, (2) fiscal port harbor and (3) San Carlos estuary, adjacent to the to the town of the same name. The measured physical, chemical and biological parameters were temperature, salinity, dissolved oxygen, chlorophyll-a, nutrients, dissolved trace metals, and coliform bacteria. The results showed poor water quality in the three areas studied, in accordance with NOM-001-SEMARNAT-1996 and the ecological criteria for water quality CE-CCA-001/89, in particular regarding phosphate, ammonium, and silicate (unregulated) concentrations, as well as the presence of Escherichia coli. The three zones are considered sources of anthropogenic contamination whose impact is greater in the warmest month and dead tides, probably due to the entry of water contaminated by anthropogenic waste derivatives. According to the sanitary authorities of the state of Baja California Sur, the certification of water quality in Magdalena Bay has been variable: it was not certified in 2014, whilst in the period 2015-2017 it was re-certified. Although this region is an important touristic and fishing site, it is at risk of contamination due to the lack of a wastewater treatment system in the town and the inadequate disposal of raw sewage from the port.