Kochi: Kerala’s fishing communities have mixed feelings about the monsoon—the rough weather spells off the coast of the Arabian Sea can make it too dangerous for the boats. But the rainy season that runs from June to September also causes the formation of the chaakara—a mudbank that builds up parallel to the shore, creating an area of calm that is rich in nutrients and draws abundant mackerel, prawns and sardine and acts as a natural barrier against sea erosion.
The currents and monsoon winds churn the bottom of the sea, flushing out the silt and nutrient-rich slush to form the muddy pools that at times run several kilometres long, taking on the proportions of a lake.
Easy pickings for fisherfolk who cannot put out to sea, the chaakara has become a part of the state’s folklore, celebrated in song and cinema as a miracle of nature.
But the phenomenon has been on the wane in recent years, says K.K. Balachandran, scientist at the Kochi regional centre of the National Institute of Oceanography, who blames the “weak intensity of their formation and their infrequent recurrences now” on “climate change and land use that has blocked free water flow from the watersheds and lakes to the sea, like in the Vembanad lake in Alappuzha”.
Erratic phenomenon: A fishing boat off the coast of Mararikulam, Alappuzha, in Kerala. Scientists blame climate change and land use for the weak intensity and infrequent recurrence of mudbanks in recent years. AFP
The government now wants to try and recreate the mudbanks using science. It will soon meet scientists of the Geological Survey of India, or GSI, who have floated a plan for the replication of the mud bank formation, along with other experts and environmentalists.
GSI scientists A.C. Dinesh and C. Jayaprakash, who have been studying the composition of the mudbanks for four years, suggest in a research paper that the mudbanks can be created through the seeding of certain minerals in the right proportion.
The GSI study holds great promise and the government proposes to take it forward, said Thomas Isaac, Kerala’s finance minister. The state government also wants to involve the Central Marine Fisheries Research Institute in Kochi, which was among the first to study mud banks back in the 1980s, in the project.
“If there is a consensus, the government can ask GSI to artificially create mud banks on an experimental basis,” Isaac said.
Dinesh and Jayaprakash say the phenomenon is unique to the Kerala coast because of the clay and its constituents. The mud banks are of two types—persistent and non-persistent—with the first kind found mainly off the coast of Alappuzha district.
These are active during the monsoon and sustained throughout the year, albeit with decreasing intensity. The non-persistent ones are formed at several places north of Alappuzha and disappear by the end of the monsoon.
An analysis of the sediment from the mudbanks showed the presence of the mineral zaherite, which has a high aluminium content, and gypsum, a common rock-forming mineral found in the sedimentary environment that spreads to produce massive beds. It has the quality of incorporating other minerals besides trapping bubbles of air and water.
The non-persistent mudbanks revealed the additional presence of gibbsite, which is further facilitated by the presence of gypsum, while the persistent ones indicated the presence of the more active zaherite.
The proposal of the GSI scientists is based on their experiment that involved the addition of 5% gypsum powder to clay sediment collected from non-mudbank areas. That resulted in a 25% volume increase in the sediment, indicating that mudbanks can be created artificially by introducing about 3–5% of a zaherite–gibbsite–gypsum mixture into the near-shore clay sediment, where waves exert maximum pressure below, Jayaprakash said.
Their studies have led them to postulate that a 4% zaherite-gibbsite-gypsum mixture added to 10,000 tonnes of sediment can create a mudbank that’s a kilometre in length, 100 metres in width and a metre in depth. The mixture can be dropped in slurry form into the clay sediment from a vessel or barge.
The scientists point out using concrete would cost more than twice as much and be an eyesore, apart from causing environmental havoc. The scientists assert that artificial mud banks will not have any adverse ecological impact and, on the contrary, contribute to increased marine life owing to the presence of minerals in the clay.
While gibbsite and gypsum are easily available, zaherite-rich rocks in the Eastern Ghats can be mined in limited quantities, the scientists say. The other prerequisites for the formation of mudbanks—strong monsoon waves combined with suitable underwater depth and a gentle slope—are already present off the Kerala coast. If such conditions are available on other coasts, similar artificial mudbanks can be created, they assert.
K.P. Thrivikramji, of Kerala University’s geology department, is sceptical about the GSI plan although he says it’s a “scientifically sound suggestion”.
“But those who suggest this have never come up with even a conceptual or dynamic model at least in a lab,” he said. “We have several instances of creation of artificial reefs by dumping or sinking ships, cars and trucks to the shallow seabed. But the mud bank is a simple or complex suspension of mud in the coastal waters, maintaining physicochemical aspects.”
The suggestions address one key concern—protection of otherwise eroding shores and beaches—but leave out the question of how the area would become rich in the nutrients that draw the fish.
G.Vivekanandan, chief executive officer of the South Indian Federation of Fishermen Societies (SIFFS), says it remains to be seen whether artificially created mudbanks will be able to attract the fish.
Balachandran of the National Institute of Oceanography, who is unsure about the success of artificially creating mudbanks, feels that any such move should be welcomed.
“The artificial creation of such mudbanks is an aspect that has not been looked into seriously and there have not been any scientific experiments in this regard,” he said. He, however, also wants studies into why the phenomenon has been on the wane.