Lake sedimentary biogenic silica from diatoms constitutes a significant global sink for aluminium

Dong Liu,Hongchang Liu,Liangliang Deng,Yaran Song,Dusan Losic,Wenxiao Fan,Junming Zhou,Jieyu Zhou,Hongzhe Song,Qian Tian,Peng Yuan,Haozhe Guo

doi:10.1038/s41467-019-12828-9

Abstract

Diatoms play an important role in marine biogeochemical cycle of aluminum (Al), as dissolved Al is taken up by diatoms to build their siliceous frustules and is involved in the sedimentation of diatomaceous biogenic silica (BSi). The Al incorporation in BSi facilitates decreasing the dissolution of marine BSi and thus substantially influences the biochemical processes driven by diatoms, such as CO2 sequestration. However, the role of lake BSi in the terrestrial biochemical Al cycle has not been explored, though lakes represent the second-largest sink for BSi. By identifying the previously unexplored high Al/Si atomic ratios (up to 0.052) in lake BSi, here we show lake BSi is a large terrestrial Al pool due to its high Al content, and lake sedimentary BSi constitutes a significant global sink for Al, which is on the same magnitude as the Al sink in global oceans.

Highlights

Diatoms play an important role in marine biogeochemical cycle of aluminum (Al), as dissolved Al is taken up by diatoms to build their siliceous frustules and is involved in the sedimentation of diatomaceous biogenic silica (BSi)
Our results demonstrate that the proportion of structural Al in lake BSi is high, which is significantly higher than the maximum Al/Si atomic ratio (~0.008) of marine BSi
The focused ion beam (FIB)–energy-dispersive X-ray spectroscopy (EDS) mapping images of the BSi-C (Fig. 1c) and BSi-N (Fig. 1f) show that Al is homogeneously distributed in the siliceous structure of lake BSi

Summary

Introduction

Diatoms play an important role in marine biogeochemical cycle of aluminum (Al), as dissolved Al is taken up by diatoms to build their siliceous frustules and is involved in the sedimentation of diatomaceous biogenic silica (BSi). The marine BSi subsequently settles, and ~3% of the total marine BSi is eventually preserved in the seafloor (with a burial rate of ~6.30 × 1012 mol year−1)[14] This process exports organic carbon to the deep sea through the marine biological pump and is important for CO2 sequestration[12]. While marine Al cycle in relation to marine BSi has been well studied[19], surprisingly, no reports have considered diatomsdriven Si and Al co-cycles in lakes, even though lakes represent the second-largest sink of BSi after the oceans and the rate of BSi burial in global lakes reaches ~1.30 × 1012 mol year−1 Identifying the level of Al incorporation in the structures of lake BSi, which has not been explored previously, is key for estimating the magnitude of Al burial in relation to BSi in global lakes, as well as for assessing the role of lake BSi in the terrestrial Al cycle

Methods

Results

Conclusion