Density and diversity of filamentous fungi in the water and sediment of Araçá bay in São Sebastião, São Paulo, Brazil

<div><p>Abstract Araçá Bay, located in the city of São Sebastião, São Paulo, Brazil, is a protected area of substantial complexity. It represents the last remaining mangrove swamp preserve between the cities of Bertioga and Ubatuba on the northern coast of São Paulo State. This mangrove swamp has specific physical and chemical properties, and it shelters a wide variety of life, including fungi. These microorganisms are present in a variety of species with different morphophysiological features, and they have the ability to produce enzymes of biotechnological importance. The goal of this study was to quantify, isolate, and identify filamentous fungi in water and sediment samples from the Araçá Bay mangrove swamp in São Sebastião. Two samplings were performed in the summer and two were performed in the winter. The samples were collected from intertidal zones, and dissolved oxygen (DO), temperature, salinity, and pH were measured in situ. The spread plate technique was used to inoculate the samples collected on plates with a potato dextrose agar (PDA) medium. A total of 208 colonies (68 from water samples and 140 from sediment samples) were isolated, and they were identified based on their morphological characteristics. Filamentous fungus density was higher in the sediment than in the water, and the samplings performed in the winter revealed a higher density than those performed in the summer. Though some of the environmental parameters were not ideal for fungal development, a high quantity of growth was nevertheless observed. When the isolated colonies were analyzed, the greatest diversity and species richness were found in the summer samples. The genera identified in all of the samples were Aspergillus, Penicillium, Cladosporium, and Fusarium. The pathogenic species found from these genera were Aspergillus fumigatus, A. terreus, Penicillium citrinum, and P. chrysogenum. These species are also able to produce enzymes that offer a variety of applications. The fungal community described herein represents the diversity found in this mangrove swamp during the period studied. Many of the fungus species found are pathogenic and may be useful due to their ability to produce specific enzymes applicable in the biotechnological and pharmaceutical industries.</p></div