Storage and recycling of major and trace element in mangroves

The role of mangroves in sequestering metal and nutrients in sediment has been described in the past, but knowl-edge gaps still exist on storage capacity and recycling fluxes of elements in plant biomass, notably concerning their magnitude in root uptake and loss by litterfall. This study addresses the storage and transport pathways of 16 elements, classified as macro-nutrients (Ca, Mg, Na, K), micro-nutrients (Fe, Mn, Ni, Co, Cu, Cr, Zn, Mo), and potential toxicants (Al, Cd, Sn, Pb) in the world's largest mangroves, the Sundarbans. Elemental concentra-tions in plant organs were generally lower than in the sediment. The stock of macro and micro-nutrients in plant biomass varied from 60 to 2717 and 0.003 to 37.7 Mg ha(-1) respectively, with highest values observed for Na and lowest for Cd. The Avicennia species exhibited the maximal accumulation of all elements. Translocation of major elements to different plant organs increased with increasing their concentrations in the sediment. Ele-mental loss via litterfall indicated that Sundarbans mangrove could act as a source, particularly of Mn, to the Bay of Bengal. Moreover, belowground uptake of the 16 elements showed 2-3 fold higher fluxes than their loss via litterfall. There was a significant retention of some trace elements (notably Mo, Cd, and Sn) in plant biomass, which might allow one to use these mangroves for phytoremediation and restoration purposes. We conclude that mangroves efficiently store and remobilize major and trace elements from the sediments by root uptake and recycle back to sediment surface via litterfall. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the storage and transport pathways of 16 elements in the Sundarbans mangroves, showing that Avicennia species accumulated all elements and some trace elements were significantly retained in plant biomass for potential phytoremediation and restoration purposes. Mangroves efficiently store and remobilize major and trace elements from sediments, with some elements being recycled back to sediment surface via litterfall.