Proteolytic Enzyme Activity and Its Relationship with Physicochemical and Microbiological Indicators in Freshwater Ecosystems of Western Cuba

The enzymatic reactions of microbial communities are rapid and adequate to changes in the composition of organic matter and environmental factors; therefore, they can be used as descriptors of biological responses in freshwater systems. The objective of this work was to determine the proteolytic enzymatic activity in the Almendares and San Juan rivers (western Cuba) and their relationship with physicochemical and microbiological indicators. The Almendares River (Havana, Cuba) presented water quality index between very poor and unusable for consumption, which makes impossible for recreational uses. In contrast, the waters of the San Juan River (Artemisa, Cuba) are classified as excellent and good in most of the sampling stations during the study period. The greatest proteolytic activities were detected in the San Juan River compared to the Almendares River, which indicates that in more contaminated ecosystems, the proteolytic enzyme activity decreases compared to another less impacted system. In addition, the annual variation in the proteolytic activity of both rivers was evidenced. In the San Juan River, a correlation was observed among proteolytic activity, the concentration of proteolytic bacteria and the physicochemical indicators of water quality, suggesting that proteolytic activity is related to naturally occurring contaminants. In contrast, in the Almendares River, this relationship was not observed, which suggests that the proteolytic activity is not directly affected by the indicators measured in this study.