Abstract
Marine blue holes are precious geological heritages with high scientific research values. Their physical and chemical characteristics are unique because of the steep-walled structure and isolated water column which create isolated ecosystems in geographically restricted areas. The Sansha Yongle Blue Hole (SYBH) is the world’s deepest marine blue hole. Here, we generated the first DNA metabarcoding dataset from SYBH sediment focusing on foraminifera, a group of protists that have colonized various marine environments. We collected sediment samples from SYBH along a depth gradient to characterize the foraminiferal diversity and compared them with the foraminiferal diversity of the costal Jiaozhou Bay (JZB) and the abyssal Northwest Pacific Ocean (NWP). We amplified the SSU rDNA of foraminifera and sequenced them with high-throughput sequencing. The results showed that the foraminiferal assemblages in SYBH were vertically structured in response to the abiotic gradients and diversity was higher than in JZB and NWP. This study illustrates the capacity of foraminifera to colonize hostile environments and shows that blue holes are natural laboratories to explore physiological innovation associated with anoxia.
Highlights
Marine blue holes are subsurface voids that form in carbonate banks during glacial periods when sea water level is low and are submerged during interglacial periods[1]
We collected 12 sediment samples from Sansha Yongle Blue Hole (SYBH), 5 from Jiaozhou Bay (JZB) and 11 from Northwest Pacific Ocean (NWP) using a combination of SCUBA diving, remotely operated vehicle (ROV), box corer and grab sampler between 2016 and 2017 (Fig. 1, Table S1)
The Sansha Yongle Blue Hole had the highest level of foraminiferal diversity from the three locations sampled in our study (Fig. 2) and the community structure was highly divergent from the two other locations (Fig. 4)
Summary
Marine blue holes are subsurface voids that form in carbonate banks during glacial periods when sea water level is low and are submerged during interglacial periods[1]. They open directly into the present marine environment and have steep-walled structure and stratified water bodies which are characterized by oxygen deficit and high levels of H2S in deeper layers[2,3,4] which create an isolated ecosystem. After comparing the three locations, we investigated the vertical variations of foraminiferal assemblages in SYBH and analyzed them in view of the environmental parameters of the water column
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