PANAJI:With COVID-19 imposed lockdown bringing to halt operation of casinos, cruises & other water sports activities, the coloured dissolved organic matter built up reduced drastically in River Mandovi last year.
The CDOM in the Mandovi Estuary was monitored since 2014, wherein high CDOM absorption was observed in the summer (especially in the midstream region) due to anthropogenic activities. In 2020 following the Government of India imposed COVID-19 lockdown (24th March- 8th June), a significant decrease of CDOM by almost 2 folds was observed in the midstream region.
The Mandovi and Zuari are the two main estuaries of Goa and have been exploited in recent years for various anthropogenic activities.
The Sentinel-2 satellite data also showed similar variations of CDOM absorption with low values during 2020. Apart from this, the concentration of dissolved nutrients in 2020 was also low compared to the previous reports.
“There was a complete standstill of anthropogenic activities such as operating pleasure cruises, water transport systems like barges, shipbuilding activities, and commercial establishments following the government-imposed lockdown, which might have reduced the CDOM and nutrients in the estuary,” NIO said in its study
The scientists have said that monitoring the water quality is of utmost necessary for managing the health of the water body. “Water quality can be assessed by its physical, chemical, biological, and microbiological characteristics of water. One of the chemical parameters of importance is the dissolved organic matter in the water (DOM), which is the largest reservoir of organic carbon in the aquatic environment.” they said
According to the NIO study, a fraction of this organic carbon absorbs light and imparts color to the water and hence known as colored dissolved organic matter (CDOM). The origin of CDOM can be either natural or from anthropogenic sources. CDOM absorbs light highly in the UV and blue regions of the solar spectrum and hence can have a positive or negative impact on the ecosystem.
“If a high amount of CDOM is present in the water it will not allow light to penetrate the water column and hence primary production will be hampered. While low levels of CDOM allow penetration of UV light to greater depths affecting the marine biota.” the study explains