Microbial contamination in the coastal waters of the southeast coast of India: A comparison of pre and post COVID-19 lockdown scenario

Anthropogenic activities on the land side cause microbial pollution in coastal waters. The primary culprits in changing coastal water quality are industrial effluents, urban discharges, and agricultural runoff. The current study provides a comparative overview of microbial abundance during the pre (July 2019) and post-lockdown (July 2020) periods. Microbial densities were significantly higher during July 2019. Total heterotrophic bacteria (THB) and E. coli (ECLO) like organisms were about 53 % higher during pre-lockdown, while Fecal coliform (FC) counts were approximately seven times higher than post-lockdown. FC levels surpassed the standard safe limits (100 FC/100 ml) prescribed by Central Pollution Control Board (CPCB) at many locations. Physiochemical variables are significantly high during pre-lockdown. Total suspended matter levels were higher by 40.1 %, Total nitrogen (69.2 %), Total phosphorus (~ 7 times), Biological oxygen demand (45.6 %), and pCO
2
(20.4%). Although nutrients are not limiting (high TN & TP), the phytoplankton biomass (Chl-a) was relatively low in pre-lockdown due to higher TSM restricting light penetration and affecting photosynthetic activities. Significant reductions in microbial contamination during July 2020 corroborated lesser anthropogenic activities associated with the lockdown, demonstrating the positive impact of lockdown on the coastal water quality.