Depth-Dependent Distribution of Prokaryotes in Sediments of the Manganese Crust on Nazimov Guyots of the Magellan Seamounts

Abstract

Deep ocean polymetallic nodules, rich in cobalt, nickel, and titanium which are commonly used in high-technology and biotechnology applications, are being eyed for green energy transition through deep-sea mining operations. Prokaryotic communities underneath polymetallic nodules could participate in deep-sea biogeochemical cycling, however, are not fully described. To address this gap, we collected sediment cores from Nazimov guyots, where polymetallic nodules exist, to explore the diversity and vertical distribution of prokaryotic communities. Our 16S rRNA amplicon sequencing data, quantitative PCR results and phylogenetic beta diversity indices showed that prokaryotic diversity in the sur cial layers (0-8 cm) was > 4-fold higher compared to deeper horizons (8-26 cm), while heterotrophs dominated in all sediment horizons. Proteobacteria was the most abundant taxon (32-82%) across all sediment depths, followed by Thaumarchaeota (4-37%), Firmicutes (2-18%) and Planctomycetes (1-6%). Depth was the key factor controlling prokaryotic distribution, while heavy metals (e.g., iron, copper, nickel, cobalt, zinc) can also in uence signi cantly the downcore distribution of prokaryotic communities. Analyses of phylogenetic diversity showed that deterministic processes governing prokaryotic assembly in sur cial layers, contrasting with stochastic in uences in deep layers. This was further supported from the detection of a more complex prokaryotic cooccurrence network in the sur cial layer which suggested more diverse prokaryotic communities existed in the surface vs. deeper sediments. This study expands current knowledge on the vertical distribution of benthic prokaryotic diversity in deep sea settings underneath polymetallic nodules, and the results reported might set a baseline for future mining decisions. Sample Collection and Environmental CharacterizationOne sediment core was collected from surface to 26 cm below sea oor (cmbsf) at the Nazimov guyots in Magellan seamount (162.45 °E, 15.18 °N, 5365 m seawater depth) using a four-tube multitube sampler (MC-400, 10×58 cm, Ocean Environmental Sci.&Tech.) during the Dayang 61st-I cruise of P. R. China. Brie y, the sediment core was sliced at 2-cm intervals with a stainless-steel cutter at 13 different sediment intervals (n = 13 samples). A sterile spatula was used to carefully collect sediment from the center of each sediment horizon for DNA extraction to avoid potential contamination. Samples were transferred to sterilized plastic tubes and stored at -80 °C until DNA extraction, and analyses of selected environmental factors like pH, electrical conductivity (EC), available phosphorous (AP), available potassium (AK), available nitrogen (AN), and organic carbon (OC), according to [30,31]. We note that our analyses on AN and AP provide bulk estimations of available N and P in the sediments without further speciation on the contribution of inorganic vs. organic sources. Brie y, samples were air-dried at room temperature in the shade and sieved through a 2-mm screen. The pH an...

Biodiversity and community structures across the Magellan seamounts and abyssal plains in the western Pacific Ocean revealed by environmental DNA metabarcoding analysis

“…This method offers several advantages, including cost-effectiveness, environmental nondestructiveness, the ability to detect a wide range of taxa, and efficiency in surveying large and hard-to-access ecosystems with high sensitivity and statistically meaningful sample sizes (Brandt et al, 2020;Le et al, 2022). Recently, several eDNA metabarcoding studies have utilized sediment samples to reveal prokaryotic, foraminiferal, and fungal communities in the Magellan seamounts, demonstrating their effectiveness and reliability (Luo et al, 2020;Yang et al, 2020;Shi et al, 2021;Sun et al, 2023). Therefore, eDNA metabarcoding holds promise for advancing our understanding of deep-sea ecosystems and guiding conservation efforts in remote and challenging environments by overcoming the limitations of traditional methods.…”

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“…This method offers several advantages, including cost-effectiveness, environmental nondestructiveness, the ability to detect a wide range of taxa, and efficiency in surveying large and hard-to-access ecosystems with high sensitivity and statistically meaningful sample sizes (Brandt et al, 2020;Le et al, 2022). Recently, several eDNA metabarcoding studies have utilized sediment samples to reveal prokaryotic, foraminiferal, and fungal communities in the Magellan seamounts, demonstrating their effectiveness and reliability (Luo et al, 2020;Yang et al, 2020;Shi et al, 2021;Sun et al, 2023). Therefore, eDNA metabarcoding holds promise for advancing our understanding of deep-sea ecosystems and guiding conservation efforts in remote and challenging environments by overcoming the limitations of traditional methods.…”

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“…This method offers several advantages, including cost-effectiveness, environmental nondestructiveness, the ability to detect a wide range of taxa, and efficiency in surveying large and hard-to-access ecosystems with high sensitivity and statistically meaningful sample sizes (Brandt et al, 2020;Le et al, 2022). Recently, several eDNA metabarcoding studies have utilized sediment samples to reveal prokaryotic, foraminiferal, and fungal communities in the Magellan seamounts, demonstrating their effectiveness and reliability (Luo et al, 2020;Yang et al, 2020;Shi et al, 2021;Sun et al, 2023). Therefore, eDNA metabarcoding holds promise for advancing our understanding of deep-sea ecosystems and guiding conservation efforts in remote and challenging environments by overcoming the limitations of traditional methods.…”