Seagrass Ecosystems of India as Bioindicators of Trace Elements

Abstract

AbstractSeagrasses are considered efficient bioindicators of coastal trace element contamination. This chapter provides an overview of the trace element accumulation, tolerance, and biomonitoring capacity of the various seagrass species along the coast of India. A total of 10 (Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn) trace elements are reported in seagrasses, 11 in sediment (As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn) and 9 (Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn) in the water column from India. From the eleven seagrass species studied, 60% of research has focused on Syringodium isoetifolium, Cymodocea serrulata, Cymodocea rotundata, and Halophila ovalis. Seventy-eight percent of seagrass trace element research in India is from the Palk Bay and the Gulf of Mannar (GOM) of Tamil Nadu and 16% from Lakshadweep Islands. Of the ten trace elements, Cd, Cu, Pb, and Zn are the most studied in seagrass; Fe, Mn, Ni, and Pb in sediment; and Cu, Fe, Mg, Ni, and Zn in the water column. The accumulation capacity of various trace elements in seagrass was species-specific. Syringodium isoetifolium has the highest concentration of Cd and Mg at Palk Bay and Lakshadweep Islands, respectively. The concentration of Cu was higher in C. serrulata at GOM. Halodule uninervis and Halophila decipiens have the highest concentration of Co and Cr, Ni, Pb, and Zn from Lakshadweep Islands. The concentration of Fe and Mn was highest in Halophila beccarii and H. ovalis from the coast of Goa and Palk Bay, respectively. Threshold levels (>10 mg L−1) of Cd, Cu, Pb, and Zn were observed for C. serrulata, H. ovalis, H. uninervis, and T. hemprichii, which can affect the Photo System II of these seagrasses and exert cellular stress leading to seagrass loss and die-off. The high concentration of these elements can exert negative impacts on seagrass-associated trophic assemblages and ecosystem functioning. Seagrasses of India can be utilized as bioindicators of coastal trace element contamination, but the associated toxicity and human health risks need further investigation.KeywordsSeagrassTrace metalsCoastal ecosystemsAnthropogenic pollutionBioindicatorsIndia