A significant decrease in navigational and industrial activities along the river bank brought down the level of coloured dissolved organic matter (CDOM) and nutrients in theMandoviestuary during the lockdown last year.
A study by Albertina Dias and other scientists of theNational Institute of (NIO), which involved sampling of water in the estuary during May 2020, showed that CDOM was low at two stations between the Mandovi bridge and Ribander as compared to the previous five years Average, from 2014 to 2018.
With restrictions in place during the Covid-19pandemic, operation of pleasure cruises, water transport systems such as barges and shipbuilding activities came to a standstill.
Relieved of anthropogenic stressors, the water quality improved due to penetration of more Light in the water column and aquatic biota in the estuary benefitted from it.
Sunlight facilitates production of phytoplankton, the algae which are fed on byzooplankton, which in turn are consumed by small fishes in the food chain.
But, if the CDOM is too low, it allows penetration of ultra violet light to greater depth and can affect the marine biota adversely. On the other hand, CDOM occurs not only due to anthropogenic factors, but also natural ones, like decay of phytoplankton also releases CDOM into the system.