#GS3 #Species #Biodiversity #Environment
In 2008, a mangrove ecologist from the University of Calcutta spotted an interesting mangrove plant at the bank of river Hooghly inside Kolkata city. It was quite unusual, as mangroves require a cyclic supply of saline water, and this growth at an upstream zone was remarkable. He then started an investigation on their distribution in the Hooghly estuary, and his recent paper suggests that the mangroves have started moving upstream, growing in less-saline regions.
- After surveying the banks near Kolkata, he was able to spot a few mangroves belonging to Sonneratia. Over the years due to gradual environmental changes and anthropogenic activities, mangroves have started to redistribute. The paper, published in Marine Pollution Bulletin, notes that they have reclaimed even the upper course of the river, which was completely devoid of mangroves before 1995.
- Between Barrackpore and Birlapur, in a non-saline region, about 239 mature trees and numerous saplings of Sonneratia caseolaris (commonly known as mangrove apple) have grown naturally. They were just four to five years old with fruits and flowers, exhibiting luxuriant growth. The team also found the redistribution of several other mangrove associate trees, shrubs and climbers in that region.
- The team emphasised the fact that the construction of Farakka Barrage in 1975 has increased fresh water flow in River Hooghly, thereby causing change in ecology and chemistry of the river.
- They also found high chemical oxygen demand in the river because of increased release of harmful chemicals from multiple point and non-point sources. Studies from China have shown that Sonneratia caseolaris grow well in the presence of high chemical oxygen demand of water. This shows the potential of Sonneratia caseolaris to act as a bio-indicator of regional environmental changes.
- The decline in the mangrove area along with this migration may increase the amplitude of coastal hazards such as storm surges, erosion and flooding.