Floating Azolla fern eased metal poisoning in fish during lab tests
Manda PL, Reddy KG, Saravanabhavan P, Sheu JR, Gandhi PR
Phytoremediation
Azolla, the tiny floating fern many pond keepers and rice growers already use as a green fertilizer, may also help fish cope with chromium and lead, though so far it's only been shown in a short lab test.
Researchers tested a river in India and found chromium and lead in the water, the riverbed mud, and the fish living there. In the lab, they exposed freshwater carp (rohu) to these metals for four days and saw stress in their bodies and damage to their gills, liver, and muscle. Adding Azolla, a small floating water fern, brought the stress markers back toward normal and reduced the tissue damage.
Key Findings
Chromium was the main toxic metal in the Ariyankuppam River, at 0.058 ± 0.003 mg per liter in water and 15.616 ± 6.672 mg per kg in sediment; lead was detected in every sample type, including fish tissue.
In rohu (Labeo rohita) exposed for 96 hours to chromium (5 mg/L) and lead (11 mg/L), the antioxidant enzyme catalase rose in gills and fell in muscle (p < 0.05), with altered protein bands and marked gill, liver, and muscle damage.
Treatment with Azolla pinnata restored catalase activity toward control levels, reduced protein pattern changes, and lessened tissue damage in the lab; long-term field trials are still needed.
chevron_right Technical Summary
Chromium and lead pollution was found in the water, mud, and fish of a river in southern India. In a lab test, feeding or exposing carp to a floating fern called Azolla reduced the metal damage to gills, liver, and muscle.
Abstract Preview
Original paper
Environmental assessment of the Ariyankuppam River, India: chromium and lead accumulation in Mugil cephalus and Azolla pinnata-mediated toxicity mitigation in Labeo rohita.
Heavy metals are persistent environmental pollutants that pose long-term risks to aquatic ecosystems and public health because of their non-biodegradable nature. This study was carried out under tw...
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Azolla is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, having a significantly different appearance to other ferns and more resembling some mosses or even duckweeds. Azolla filiculoides is one of two fern species for whic...