Assessing Coliform Bacteria in Seawater and Perna perna (Linnaeus, 1758) Mussels in the Gulf of Annaba (Algeria): Influence of Seasonal Variability and Urban Development

In recent years, there has been an increase in the number and frequency of coliform bacteria in coastal marine environments. It is therefore necessary to estimate the seawater quality that could pose a health risk to people using beaches with polluted bathing waters. Bivalve mollusks, such as mussels, are bio- indicators used to monitor environmental health due to their filter-feeding behavior, which allows them to accumulate contaminants from seawater. In this study, we focused on one mussel species, Perna perna, which is the most dominant species on the Algerian coast. The densities and community composition of coliform bacteria were investigated in samples collected from mussels and seawater in three sampling areas (urban, suburban and rural) in the Gulf of Annaba (northeastern Algeria) over a one-year period in 2017. Culture-based techniques were used to quantify and assess potentially pathogenic bacteria. In addition, measurements were taken of various physico-chemical parameters, including pH, water temperature, salinity, dissolved oxygen and suspended solids. High numbers of coliform bacteria, up to 4,500 MPN per 100 ml in seawater and 300,000 MPN per 100/g in mussels were detected during the summer months, representing an increase of three orders of magnitude compared to winter. Principal component analysis revealed that increased numbers of total coliform bacteria in seawater and mussels were accompanied by increased numbers of fecal indicator bacteria, suggesting that coliform growth is due to fecal contamination. As expected, the highest concentrations of coliform bacteria were observed in samples taken from the urban area, which contains a mixture of wastewater, agricultural and industrial pollutants. Biochemical analyses showed that the bacterial isolates were mainly potentially pathogenic species such as Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. As P. perna mussel is an edible species, the bioaccumulation and persistence of coliform bacteria represent a serious threat to human health, highlighting the necessity to include coliform bacteria in the monitoring of seafood from coastal areas.