New Britain Trench Research Articles

Unveiling the Presence of Short- and Medium-Chain Chlorinated Paraffins in the Hadal Trenches of the Western Pacific Ocean.

This study delves into the unexplored distribution and accumulation of chlorinated paraffins (CPs), pervasive industrial contaminants used as flame retardants and plasticizers, within the hadal trenches, some of Earth's most isolated marine ecosystems. Analysis of sediments from the Mussau (MS) and Mariana trench (MT) reveals notably high total CP concentrations (∑SCCPs + ∑MCCPs) of 10,963 and 14,554 ng g-1 dw, respectively, surpassing those in a reference site in the western Pacific abyssal plain (8533 ng g-1 dw). In contrast, the New Britain Trench (NBT) exhibits the lowest concentrations (2213-5880 ng g-1 dw), where CP distribution correlates with clay content, δ13C and δ15N values, but little with total organic carbon and depth. Additionally, amphipods from these trenches display varying CP levels, with MS amphipods reaching concerning concentrations (8681-16,138 ng g-1 lw), while amphipods in the MT-1 site show the lowest (4414-5010 ng g-1 lw). These bioaccumulation trends appear to be primarily influenced by feeding behaviors (δ13C) and trophic levels (δ15N). Utilizing biota-sediment accumulation factor values and principal component analysis, we discern that CPs in sediment may come from surface-derived particulate organic matters, while those in amphipods may come from the above carrion. Our findings elucidate the profound impacts of the emerging pollutants on the Earth's least explored marine ecosystems.

Community Composition and Functional Characterization of Microorganisms in Surface Sediment of the New Britain Trench.

The deep-sea harbors abundant prokaryotic biomass is a major site of organic carbon remineralization and long-term carbon burial in the ocean. Deep-sea trenches are the deepest part of the ocean, and their special geological and morphological features promoting the accumulation of organic matter and active organic carbon turnover. Despite the expanding reports about the organic matter inputs, limited information is known regarding microbial processes in deep-sea trenches. In this study, we investigated the species composition and metabolic potential in surface sediment of the New Britain Trench (NBT), using a metagenomic approach. The predominant microbial taxa in NBT sediment include Proteobacteria, Acidobacteria, Planctomycetes, Actinobacteria and Chloroflexota. The microbial communities showed highly diverse metabolic potentials. Particularly, genes encoding enzymes for degradation of aromatic compounds, as well as those encoding haloalkane dehalogenase and haloacetate dehalogenase were annotated in the NBT surface sediment, which indicate the potential of microorganisms to degrade different types of refractory organic matter. The functional genes encoding enzymes for dissimilatory nitrate reduction, denitrification, and nitrification were also represented in the NBT metagenome. Overall, the microbial communities show high diversity of heterotrophic lineages and metabolic features, supporting their potential contributions in organic carbon metabolism. Meanwhile, Nitrosopumilus, a dominant genus in the surface sediment of the NBT, is a typical ammonia-oxidizing archaea (AOA), with autotrophic CO2 fixation pathways including the 3-hydroxypropionate/4-hydroxybutylate (3HP/4HB) cycle, the reductive TCA (rTCA) cycle. The results demonstrate that autotrophic metabolic processes also play an important role in the surface sediment, by providing newly synthesized organic matter.

Co-Evolution of Parallel Triple Subduction Systems in the New Guinea Region: A Systematic Numerical Study

A specific configuration of the global subduction system is the parallel triple subduction. The widely accepted example of parallel triple subduction is the New Guinea region, including a northward dip at the New Britain Trench (NBT), a southward dip at the Trobriand Trough (TT), and North Solomon Trench (NST). Questions regarding the parallel triple subduction system remain largely unexplored in terms of factors controlling its initiation, duration, and dynamics. Here, we used two-dimensional numerical models to study the dynamics mechanism of the parallel triple subduction system in the New Guinea region. Four possible regimes were achieved: 1) the double subduction model, which includes the forward subduction jumping model (FSJ) and the subduction polarity reversal model (SPR) and 2) the parallel triple subduction model, which includes the tendency to the forward jumping model (TFSJ) and the tendency to polarity reversal (TSPR). By evaluating the four regimes with actual seismic data, we suggest that the pre-existing rupture and length of ocean–continent transition (OCT) determine the formation of the TT, while the formation of the NBT may be the result of the rheological strength differences between the Solomon Island Arc (SIA) and Solomon Sea Basin (SSB); the initial length of the SSB can regulate the competitive relationship between the TT and NBT, which also determines the present-day inactive state of the TT. A longer SSB makes the TT and NBT initiated independently, while a narrower SSB will allow interaction during subduction initiation of the TT and NBT.

Geochemistry and mineralogy of the sediments in the New Britain shelf-trench continuum, offshore Papua New Guinea: Insights into sediment provenance and burial in hadal trenches

Seven short cores collected along two transects from the shelf to trench bottom in the New Britain Trench (NBT) area, Papua New Guinea (PNG), were studied to illuminate the provenance and burial of sediments across the shelf-trench continuum. Here, we present geochemical data, including major, minor and rare earth elements, bulk and clay mineralogy, grain size, and Sr–Nd isotopes. The results indicate that sediments in the NBT area were mainly derived from intermediate volcanogenic materials of the surrounding islands with the contribution of volcanogenic materials up to 90%. Volcanogenic materials from Rabaul Volcano had a significant influence on the western NBT (Transect 1), whereas the eastern NBT (Transect 2) was more strongly affected by the Tabar-Lihir-Tanga-Feni (TLTF) volcanic chain. In addition, pollen and spores analyses showed a decreasing trend in their concentrations in the order of the landward site, the trench axis site, and the abyssal site on the Transect 1 and the dominance of Cyperaceae in the herb fraction at the trench axis site NBT01. This observation, accompanied by the significant differences in the major and minor elements as well as Sr–Nd isotopes between upper 4 cm sediments and those below at NBT01, suggests that the upper 4 cm sediments were probably sourced from river sediments. Together with low chemical index of alteration (CIA) values, we suggest that terrigenous riverine materials are rapidly transported and buried at the trench axis. Our findings highlight the important role of hadal trenches in trapping terrigenous materials and have implication for understanding the fate of terrigenous materials in the deep ocean.

Revealing the Viral Community in the Hadal Sediment of the New Britain Trench.

Marine viruses are widely distributed and influence matter and energy transformation in ecosystems by modulating hosts’ metabolism. The hadal trenches represent the deepest marine habitat on Earth, for which the viral communities and related biogeochemical functions are least explored and poorly understood. Here, using the sediment samples (8720 m below sea level) collected from the New Britain Trench (NBT), we investigated the viral community, diversity, and genetic potentials in the hadal sediment habitat for the first time by deep shotgun metagenomic sequencing. We found the NBT sediment viral community was dominated by Siphoviridae, Myoviridae, Podoviridae, Mimiviridae, and Phycodnaviridae, which belong to the dsDNA viruses. However, the large majority of them remained uncharacterized. We found the hadal sediment virome had some common components by comparing the hadal sediment viruses with those of hadal aquatic habitats and those of bathypelagic and terrestrial habitats. It was also distinctive in community structure and had many novel viral clusters not associated with the other habitual virome included in our analyses. Further phylogenetic analysis on its Caudovirales showed novel diversities, including new clades specially evolved in the hadal sediment habitat. Annotation of the NBT sediment viruses indicated the viruses might influence microbial hydrocarbon biodegradation and carbon and sulfur cycling via metabolic augmentation through auxiliary metabolic genes (AMGs). Our study filled in the knowledge gaps on the virome of the hadal sediment habitats and provided insight into the evolution and the potential metabolic functions of the hadal sediment virome.

Population structure, activity potential and ecotype partitioning of Pseudoalteromonas along the vertical water column of the New Britain Trench.

Microbial degradation of organic matter along the vertical profile of the water column is a major process driving the carbon cycle in the ocean. Pseudoalteromonas has been identified as a dominant genus in pelagic marine environments worldwide, playing important roles in the remineralization of organic carbon. However, the current understanding of Pseudoalteromonas was mainly based on shallow water populations or cultivated species. This study analyzed for the first time the structure, activity potential and ecotypes differentiation of Pseudoalteromonas in the water column of the New Britain Trench (NBT) down to 6000m. Analysis on diversities of the 16S rRNA gene and their transcripts showed that Pseudoalteromonas was greatly enriched in deep-sea waters and showed high activity potentials. The deep-sea Pseudoalteromonas were significantly different from their shallow-water counterparts, suggesting an obvious ecotype division along with the vertical profile. Phylogenetic analysis on the 16S rRNA gene and hsp60 gene of 219 Pseudoalteromonas strains isolated from different depths further showed that the vertical ecotype division could even occur at the strain level, which might be a result of long-term adaptation to environmental conditions at different depths. The discovered depth-specific strains provide valuable models for further studies on adaptation, evolution and functions of the deep-sea Pseudoalteromonas.

SCRIPTING CARTOGRAPHIC METHODS OF GMT FOR MAPPING THE NEW BRITAIN AND SAN CRISTOBAL TRENCHES, SOLOMON SEA, PAPUA NEW GUINEA

The study present a case study of the Generic Mapping Tools (GMT) applied for cartographic modelling, mapping and comparative analysis of the deep-sea trenches located in southwest Pacific Ocean: the New Britain Trench (NBT) and the San Cristobal Trench (SCT). The aim was to evaluate their geomorphic variation using scripting cartographic approach of GMT. The data was processed using a sequence of the GMT modules with the main module 'grdtrack' used to visualize cross-section profiles along the trenches for their geomorphological modelling. The main grid used for topographic mapping is the SRTM DEM with 15-arc second resolution. The statistical analysis shown variability in depths of both trenches by samples in two transects. The cartographic analysis demonstrated following results. The SCT is generally deeper reaching -9,000 m, while the median for the NBT less then 7,000 m. The gradient slope of SCT is more symmetric with accurate 'V' form. In a cross-section graph, the NBT landward slope is markedly asymmetric U-shaped form and has a crescent form in the east. The NBT slope dips westwards with 35° eastward, and 41° westward, while the SCT slope has 33° oceanwards and 33,69° landwards. The difference between the geomorphology of the trenches is explained by the effects of the geotectonic evolution and actual sedimentary processes affected their formation and sculptured their structure. The marine free-air gravity anomaly illustrated density anomalies at the bathymetry in the region of NBT and SCT with range <-60.0 mGal. The geoid values are 56-66 mGal. The study contributed to the submarine geomorphic mapping and presents technical application of the cartographic functionality of GMT used for geomorphological modelling.

Transitions in microbial communities along two sediment cores collected from the landward walls of the New Britain trench

The landward wall of the New Britain Trench (NBT) is an active continental margin. Unlike passive margins, it lacks a continental rise and the abyssal plain, and has a steep continental slope ending in an oceanic trench. Although the trench systems are receiving more and more attentions, our understanding of the microbiology of the NBT and its trench walls is limited. In this study, we collected a 70 cm gravity core (4524 m depth) and a 30 cm box core (4130 m depth) from the western and eastern landward walls of the NBT, respectively. Diversity and composition of microbial communities were investigated at high resolution in 2 cm depth intervals. In two cores, obvious vertical transitions from the aerobic to anaerobic but distinct dominant anaerobic microbes were observed. In the eastern trench wall, anaerobic fermenters, such as Anaerolineales and Alphaproteobacteria, were dominant, but the western contained abundant Dehalococcoidia, and Gammaproteobacteria, such as Alteromonadales and Oceanospirillales. Combined with the results of higher bacteria abundance and probable shallower aerobic active zone in the eastern core, such patterns of species composition might be related with richer input of labile allochthonous terrestrial organic matter by mass wasting processes in the steeper eastern wall. Our analysis also revealed highly diversified Dehalococcoidia including some new phylotypes, extending the current understandings on Dehalococcoidia diversity. This study fills the gap of benthic microbial study in the NBT, and highlights the need of multi-point sampling in trench studies for the great geographical variations along the trench wall.

Intact Ether Lipids in Trench Sediments Related to Archaeal Community and Environmental Conditions in the Deepest Ocean

AbstractArchaea play an important role in marine biogeochemical cycle; however, their phylogenetic distribution and lipid composition in the hadal zone (6–11 km water depth) are poorly known. Here, we analyzed archaeal membrane lipids and 16S rRNA gene sequences in sediments from Mariana Trench (MT), Massau Trench (MS), and New Britain Trench (NBT), varying from 1,560 to 10,840 m depth. Forty‐two intact polar lipids (IPLs) were identified, including glycerol dialkyl glycerol tetraethers (GDGTs), OH‐GDGTs, glycerol dialkyl diethers (GDDs), and archaeol (AR) with polar headgroups of monohexose (1G), dihexose (2G), trihexose (3G), and hexose‐phosphohexose (HPH). Compositional and spatial distribution patterns of archaeal lipids suggest benthic Thaumarchaeota as a major source for IPLs, consistent with the predominance of Thaumarchaeota genes (>80%). The redundancy analysis (RDA) based on lipid and 16S rRNA data separates samples into three groups: extremely deep water (MT), significant terrestrial influence (NBT 1, 4, and 6), and predominant marine influence (MS, NBT 2, 3, 7, and 10). 1G‐GDDs and 1G‐AR positively correlate with water depth, likely reflecting the adaptation of benthic archaea to elevated hydrostatic pressure or variation of archaeal community in trench sediments. Bathyarchaeota are more abundant in sediments receiving terrestrial input; this pattern was attributed to their capability of utilizing terrestrial organic matter as an energy source. Our study highlights important environmental influences (e.g., pressure and organic matter quality and quantity) on benthic archaeal community and archaeal IPL compositions, which should be considered when IPLs and core lipids are applied as chemotaxonomic markers and paleo‐proxies.

DNA stable-isotope probing reveals potential key players for microbial decomposition and degradation of diatom-derived marine particulate matter.

Microbially mediated decomposition of particulate organic carbon (POC) is a central component of the oceanic carbon cycle, controlling the flux of organic carbon from the surface ocean to the deep ocean. Yet, the specific microbial taxa responsible for POC decomposition and degradation in the deep ocean are still unknown. To target the active microbial lineages involved in these processes, 13C‐labeled particulate organic matter (POM) was used as a substrate to incubate particle‐attached (PAM) and free‐living microbial (FLM) assemblages from the epi‐ and bathypelagic zones of the New Britain Trench (NBT). By combining DNA stable‐isotope probing and Illumina Miseq high‐throughput sequencing of bacterial 16S rRNA gene, we identified 14 active bacterial taxonomic groups that implicated in the decomposition of 13C‐labeled POM at low and high pressures under the temperature of 15°C. Our results show that both PAM and FLM were able to decompose POC and assimilate the released DOC. However, similar bacterial taxa in both the PAM and FLM assemblages were involved in POC decomposition and DOC degradation, suggesting the decoupling between microbial lifestyles and ecological functions. Microbial decomposition of POC and degradation of DOC were accomplished primarily by particle‐attached bacteria at atmospheric pressure and by free‐living bacteria at high pressures. Overall, the POC degradation rates were higher at atmospheric pressure (0.1 MPa) than at high pressures (20 and 40 MPa) under 15°C. Our results provide direct evidence linking the specific particle‐attached and free‐living bacterial lineages to decomposition and degradation of diatomic detritus at low and high pressures and identified the potential mediators of POC fluxes in the epi‐ and bathypelagic zones.

Efficient sequestration of terrigenous organic carbon in the New Britain Trench

The fate of terrigenous organic carbon (OCterr) in the ocean remains an enigma for four decades. Hadal trenches, the deepest ocean realm (6–11 km deep), were recently proposed to be OC depocenters, but whether and how much OCterr was sequestrated there remain elusive. Here we conducted comprehensive analyses for four sediment cores from the New Britain Trench (NBT) close to Papua New Guinea to assess source, translocation and burial of OC. The bulk and molecular radiocarbon data suggest that the NBT landward slope and axis sediments mainly receive young and biogenic rather than petrogenic OC. The three-endmember mixing model based on Δ14C, δ13C and OC contents reveals that sediments of the NBT axis (8225 m) comprise relatively high OC contents (0.66 ± 0.08%), of which biogenic OCterr accounts for 62 ± 10%. The high proportion of biogenic OCterr was attributed to the selective translocation of OCterr-enriched coarse particles and rapid delivery of sediments supported by unique V-shape feature of the trench. In contrast, the sediment OC at the oceanward slope is primarily of a marine origin, suggesting that OCterr was efficiently trapped in the trench bottom. It is estimated that the burial rate is 2.75 ± 0.32 g C m−2 yr−1 for OC and 1.69 ± 0.41 g C m−2 yr−1 for OCterr in the NBT. Given a fact that many trenches are close to the landmasses, we propose that the hadal trenches may contribute significantly to the burial of OCterr in the ocean.

Depth-Resolved Distribution of Particle-Attached and Free-Living Bacterial Communities in the Water Column of the New Britain Trench.

Particle-attached (PA) and free-living (FL) microorganisms play significant but different roles in mineralization of organic matter (OM) in the ocean. Currently, little is known about PA and FL microbial communities in bathyal and abyssal pelagic waters, and understanding of their diversity and distribution in the water column and their interactions with environmental factors in the trench area is limited. We investigated for the first time the variations of abundance and diversities of the PA and FL bacterial communities in the epi-, bathy-, and abyssopelagic zones of the New Britain Trench (NBT). The PA communities showed decreasing species richness but increasing relative abundance with depth, suggesting the increasing ecological significance of the PA bacteria in the deep ocean. The abundance and diversity of PA and FL bacterial communities in the NBT water column appeared to be shaped by different sets of environment factors, which might be related to different micro-niches of the two communities. Analysis on species distribution suggested that the differences between PA and FL bacteria communities mainly resulted from the different relative abundance of the “shared taxa” in the two types of communities. These findings provide valuable information for understanding the relative ecological roles of the PA and FL bacterial communities and their interactions with environmental factors in different pelagic zones along the vertical profile of the NBT water column.

Tectonic and magmatic evolution of the Bismarck Sea, Papua New Guinea; review and new synthesis

The Bismarck Sea, located north of Papua New Guinea and just south of the equator, formed during the final stages of a long, complex geological development of the Melanesian Borderland, which resulted from Cenozoic convergence between the Australian and Pacific-Caroline Plates and the opening of back-arc basins. The sea, which straddles two oppositely facing trenches, the inactive Manus trench and the active New Britain trench, covers two basins, the New Guinea Basin to the west and the Manus Basin to the east. These basins are separated by the shallow Willaumez-Manus Rise, trending roughly from WNW to ESE. The origin of these major structural units and their relationship with the present-day zone of major seismicity along the Bismarck Sea Seismic Lineation remains unclear. A detailed examination of geophysical and geochemical data, combined with geologic and geodetic information from surrounding regions, attests that the Bismarck Sea went through some rather unusual events of back-arc development beginning in the middle Pliocene. Around 3.5 Ma, the northern tip of New Guinea came into contact with the Finisterre-Huon Range. The event triggered a back-arc opening that eventually divided the Bismarck seafloor into North and South Bismarck Plates. The rapid opening also caused an upwelling of anomalously hot upper mantle beneath the Bismarck Sea. A large volcanic outflow during this period may have contributed to the formation of the rise west of Manus Island. Both the North and South Bismarck Plates interacted with surrounding plates, and small and large changes may have occurred throughout their history. A sudden shift in local plate motion, perhaps caused by locking such as plate collision, may have caused the overlying lithosphere to decouple from the mantle upwelling. The Willaumez-Manus Rise was probably created under such circumstances when a large volume of rising magma leaked out along a strike-slip plate boundary linking the spreading centers in the New Guinea and Manus basins. An alternative view is that the Willaumez-Manus Rise represents a magmatically robust segment of a single spreading axis that linked the two basins. The further docking of Finisterre-Huon Range with the New Guinea Highlands allowed the South Bismarck Plate to open faster toward the east in the Manus Basin and eventually to jump to the present-day Bismarck Sea Seismic Lineation. The Willaumez Transform was initiated by this more recent plate-boundary reorganization. Seafloor spreading commenced in the Manus Spreading Center <0.78 Ma, and the overall pattern suggests that rifting in the Bismarck Sea is propagating eastwards in the Southeastern Rift and westwards in the Western Spreading Ridges. One feature that distinguishes the Bismarck Sea from most other recently opened back-arc spreading systems in the western Pacific, except for the northern North Fiji and Lau basins, is the anomalously large distance (more than 400 km) between the arc and the spreading axis. This reflects the complex, combined geodynamic processes in this region, i.e., arc-continent collision, mantle upwelling, and rapid back-arc opening specific to this region. Central Bismarck Sea lavas are also unusual as they contain chemical components characteristic of the lower mantle. This may reflect proximity to the Melanesian Borderland, long a site of major subduction, and therefore of upper mantle enrichment by subduction-derived components, compared to other spreading systems.