Screening of Film Forming Microorganisms Influencing the Processes of Bio-fouling in Different Gradient Zones of Vellar Estuary, Tamil Nadu, India
T. Sasidharan *
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
S. Bragadeeswaran
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
S. Kumaresan
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
B. Visnu
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
R. Seetharaman
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
S. Srikavibharathi
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
Mohamed Asarudeen
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
W. V. Celcia Gnana Rathinam
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
P. Sandhiya
Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai- 608502, Cuddalore, Tamil Nadu, India.
*Author to whom correspondence should be addressed.
Abstract
Estuaries are dynamic intertidal ecosystems that support diverse biological communities shaped by salinity gradients and associated physicochemical conditions. This study examined bacterial colonisation and biofilm-forming communities on submerged polyethylene terephthalate (PET) panels deployed in the marine, brackish-water and freshwater zones of the Vellar estuary, south-east coast of India. Total plate count, bacterial diversity and selected physicochemical variables were assessed to understand microbial succession during early biofouling. Bacterial density increased progressively up to the fourth week and then declined, corresponding with the subsequent colonisation of higher-order fouling organisms. The brackish-water zone recorded the highest bacterial density (160 × 10² CFU ml-1), followed by the freshwater zone (125 × 10² CFU ml-1) and the marine zone (118 × 10² CFU ml-1), indicating that intermediate salinity favoured microbial growth and surface colonisation. Bacterial composition varied across salinity gradients. Vibrio spp. dominated in the marine and brackish-water zones, whereas Pseudomonas sp. was dominant in the freshwater zone. Sanger 16S rRNA sequencing identified Vibrio alginolyticus, Vibrio harveyi and Pseudomonas putida as the dominant species in the respective zones. The results indicate that salinity influences bacterial abundance, community composition and biofilm formation on PET surfaces. These findings provide useful baseline information for understanding early biofouling processes in estuarine environments and may support future studies on sustainable antifouling strategies.
Keywords: Estuary, salinity gradients, physicochemical parameters, biofilm and bacterial diversity