Environmental study of the role of anthropogenic factors on the possible pollution of coastal marine waters in Dakhla Bay – Morocco

Abstract— The sites used for breeding and the beaches are ranked in descending order of health in 4 categories A, B, C and D according to the estimate of the microbiological quality and evaluation of the chemical contamination (circular 15.08.12 d 'August 2012). After classification, the target areas are subject to regular health surveillance, intended to verify the durability of the characteristics that have based their classification and to detect possible episodes of contamination. This monitoring covers the measurement of microbiological, chemical (heavy metal) and marine biotoxin parameters in bivalve molluscs, as well as phytoplankton pests in seawater.

The Main objective of the present survey is to make a diagnosis of the state of health of the principal beaches of the region of Dakhla Oued Eddahaba bay in years 2015, 2016 and 2017. Our sampling focused on 4 beaches: Foum Lbouir, El Moussafir, Lakeira, and Tourist Area. Bacteriological analyzes were conducted to identify the microorganisms that are indicative of faecal pollution including faecal coliforms, faecal streptococci and Escherichia coli and their enumeration by the filter membrane method on nutrient media Tergitol7 Agar, Litsky, Slanetz & Bartley.

In addition to microbiological monitoring of seawaters, the air temperature was measured "in situ" using a mercury thermometer, the temperature of the water using a pH meter, the tide (high or low) and finally the estimate of the number of bathers.

The Main results obtained made it possible to classify the four beaches in 3 categories according to the Moroccan standard for monitoring bathing water quality NM 03.7.200. The beaches of the Al Moussafir and Tourist PK25 are classified A. The beaches of Foum Lebouir with medium quality waters is classified A or B. Only the beach of Lakheira is very polluted and classified in category C.