Seagrass Ecosystems of India as Bioindicators of Trace Elements

Abstract

Seagrasses are considered as efficient bioindicators of coastal trace element contamination. This chapter provides an overview on the trace element accumulation, tolerance and biomonitoring capacity of the various seagrass species distributed along the coast of India. A total of 10 trace elements are reported in seagrasses, 11 in sediment and nine in the water column from India. From the 11 seagrass species studied, 60% of research have focused on Syringodium isoetifolium, Cymodocea serrulata, Cymodocea rotundata and Halophila ovalis. 78% of seagrass trace element research in India is from Palk bay and Gulf of Mannar (GOM), Tamil Nadu and 16% from Lakshadweep Islands. Out of the 10 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. Accumulation capacity of various trace elements in seagrass were species-specific. S. isoetifolium have 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 decipens have the highest concentration of Co, and Cr, Ni, Pb and Zn from Lakshadweep Islands. The highest concentration of Fe and Mn were 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, that can affect the Photo System -II of these seagrasses and exert cellular stress leading to seagrass loss and die-off. 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 needs further investigation.

Trace metal content in sediment cores and seagrass biomass from a tropical southwest Pacific Island

“…On the other hand, our study also showed that seagrasses at the Korotogo site accumulate more Fe in their tissues than those at Nasese. Similar trend were observed in the whole plant tissues of the three seagrass species reported by Mishra et al (2020) where Fe content was the highest element (795-1886 μg g − 1 ) accumulated in H. pinifolia (Table S4). However, Fe content in the present study (7493-26,137 μg g − 1 ) was much higher than reported by Mishra et al (2020); this could be because the uptake of the elements is influenced by their available concentrations in the surrounding sediment.…”

“…Our data shows that Zn was recorded at the highest content in tissues of H. uninervis (52.27 ± 1.76 μg g − 1 ) at Nasese, while the lowest level was recorded in H. pinifolia (22.33 ± 3.22 μg g − 1 ) tissues at Korotogo. The results obtained for Zn in the present study were compared to the results of Mishra et al (2020) for the same three seagrass species where H. pinifolia (35-69.17 μg g − 1 ) had accumulated higher Zn content, while H. ovalis Zn content was within this range (Table S4). Mishra et al (2020) reported that the Cu content of the seagrass (H. ovalis, H. pinifolia and H. uninervis) from India varied from 3.79 to 60.83 μg g − 1 which is comparable to those reported in the three seagrass species in this study (8.7 to 20.5 μg g − 1 ).…”

“…The results obtained for Zn in the present study were compared to the results of Mishra et al (2020) for the same three seagrass species where H. pinifolia (35-69.17 μg g − 1 ) had accumulated higher Zn content, while H. ovalis Zn content was within this range (Table S4). Mishra et al (2020) reported that the Cu content of the seagrass (H. ovalis, H. pinifolia and H. uninervis) from India varied from 3.79 to 60.83 μg g − 1 which is comparable to those reported in the three seagrass species in this study (8.7 to 20.5 μg g − 1 ). Nonetheless, the low Cu and Zn contents of seagrasses reported in this study, from both study sites, suggest moderate trace metal (Table 3) pollution, and such levels may be considered background levels for a tropical coastal locality.…”