Southwest Pacific Ocean Research Articles

Identifying Black Corals and Octocorals From Deep-Sea Imagery for Ecological Assessments: Trade-Offs Between Morphology and Taxonomy

An increased reliance on imagery as the source of biodiversity data from the deep sea has stimulated many recent advances in image annotation and data management. The form of image-derived data is determined by the way faunal units are classified and should align with the needs of the ecological study to which it is applied. Some applications may require only low-resolution biodiversity data, which is easier and cheaper to generate, whereas others will require well-resolved biodiversity measures, which require a larger investment in annotation methods. We assessed these trade-offs using a dataset of 5 939 images and physical collections of black and octocorals taken during surveys from a seamount area in the southwest Pacific Ocean. Coral diversity was greatly underestimated in images: only 55 black and octocoral ‘phototaxa’ (best-possible identifications) were consistently distinguishable out of a known 210 species in the region (26%). Patterns of assemblage composition were compared between the phototaxa and a standardized Australian classification scheme (“CATAMI”) that uses morphotypes to classify taxa. Results were similar in many respects, but the identities of dominant, and detection of rare but locally abundant, coral entities were achieved only when annotation was at phototaxon resolution, and when faunal densities were recorded. A case study of data from 4 seamounts compared three additional classification schemes. Only the two with highest resolution – phototaxon and a combined phototaxon-morphological scheme – were able to distinguish black and octocoral communities on unimpacted vs. impacted seamounts. We conclude that image annotation schemes need to be fit-for-purpose. Morphological schemes such as CATAMI may perform well and are most easily standardized for cross-study data sharing, but high resolution (and more costly) annotation schemes are likely necessary for some ecological and management-based applications including biodiversity inventory, change detection (monitoring) – and to develop automated annotation using machine learning.

Nation-wide hierarchical and spatially-explicit framework to characterize seagrass meadows in New-Caledonia, and its potential application to the Indo-Pacific

Despite their ecological role and multiple contributions to human societies, the distribution of Indo-Pacific seagrasses remains poorly known in many places. Herein, we outline a hierarchical spatially-explicit assessment framework to derive nation-wide synoptic knowledge of the distribution of seagrass species and communities. We applied the framework to New Caledonia (southwest Pacific Ocean) and its 36,200 km2 of reefs and lagoons. The framework is primarily field-based but can leverage various habitat maps derived from remote sensing. Field data collection can be stratified by map products and retrospectively contribute to developing new seagrass distribution maps. Airborne and satellite remote sensing alone do not allow for the spatial generalisation of the finest attributes (species distribution and types of seagrass beds), but staged stratified field sampling provides synoptic views of these attributes. Using three examples, we discuss how the hierarchical and spatial information generated from this framework's application can inform conservation and management objectives.

Hydrothermal trace metal release and microbial metabolism in the northeastern Lau Basin of the South Pacific Ocean

Abstract. Bioactive trace metals are critical micronutrients for marine microorganisms due to their role in mediating biological redox reactions, and complex biogeochemical processes control their distributions. Hydrothermal vents may represent an important source of metals to microorganisms, especially those inhabiting low-iron waters, such as in the southwest Pacific Ocean. Previous measurements of primordial 3He indicate a significant hydrothermal source originating in the northeastern (NE) Lau Basin, with the plume advecting into the southwest Pacific Ocean at 1500–2000 m depth (Lupton et al., 2004). Studies investigating the long-range transport of trace metals associated with such dispersing plumes are rare, and the biogeochemical impacts on local microbial physiology have not yet been described. Here we quantified dissolved metals and assessed microbial metaproteomes across a transect spanning the tropical and equatorial Pacific with a focus on the hydrothermally active NE Lau Basin and report elevated iron and manganese concentrations across 441 km of the southwest Pacific. The most intense signal was detected near the Mangatolo Triple Junction (MTJ) and Northeast Lau Spreading Center (NELSC), in close proximity to the previously reported 3He signature. Protein content in distal-plume-influenced seawater, which was high in metals, was overall similar to background locations, though key prokaryotic proteins involved in metal and organic uptake, protein degradation, and chemoautotrophy were abundant compared to deep waters outside of the distal plume. Our results demonstrate that trace metals derived from the NE Lau Basin are transported over appreciable distances into the southwest Pacific Ocean and that bioactive chemical resources released from submarine vent systems are utilized by surrounding deep-sea microbes, influencing both their physiology and their contributions to ocean biogeochemical cycling.

New free-living nematode species and records (Chromadorea: Plectida and Desmodorida) from the edge and axis of Kermadec Trench, Southwest Pacific Ocean.

One new nematode species is described and two new species records are provided from the edge (6,080 m depth) and axis (7,132 m) of Kermadec Trench, Southwest Pacific. Leptolaimus hadalis sp. nov. is characterised by medium body 587–741 μm long, labial region not offset from body contour, inconspicuous labial sensilla, amphid located 12–19 μm from anterior end, female without supplements, male with four tubular precloacal supplements (alveolar supplements absent), tubular supplements almost straight with dentate tip, arcuate spicules and weakly cuticularized dorsal gubernacular apophyses strongly bent distally. In a previously published ecological survey of Kermadec Trench, L. hadalis sp. nov. was the most abundant species in a core obtained at 8,079 m water depth and third most abundant species in a core obtained at 7,132 m, while only one individual was found at 6,096 m depth, and none at 9,175 m depth (Leduc & Rowden, 2018). Alaimella aff. cincta and Desmodora aff. pilosa are recorded for the first time from the Southwest Pacific region. Prior to the present study, Alaimella had only been recorded from coastal locations and from the Weddell sea to a depth of 2,000 m. The record of Desmodora aff. pilosa at 6,080 m depth is the deepest record of a Desmodora species to date, although unidentified Desmodora specimens have been found as deep as 6,300 m in the South Sandwich Trench. The morphology of the Kermadec Trench Alaimella aff. cincta and Desmodora aff. pilosa specimens bear a strong resemblance to their respective type populations from the Northern Hemisphere, but further morphological and molecular data are required to ascertain whether they in fact represent distinct species.

The Bouraké semi-enclosed lagoon (New Caledonia) – a natural laboratory to study the lifelong adaptation of a coral reef ecosystem to extreme environmental conditions

Abstract. According to current experimental evidence, coral reefs could disappear within the century if CO2 emissions remain unabated. However, recent discoveries of diverse and high cover reefs that already live under extreme conditions suggest that some corals might thrive well under hot, high-pCO2, and deoxygenated seawater. Volcanic CO2 vents, semi-enclosed lagoons, and mangrove estuaries are unique study sites where one or more ecologically relevant parameters for life in the oceans are close to or even worse than currently projected for the year 2100. Although they do not perfectly mimic future conditions, these natural laboratories offer unique opportunities to explore the mechanisms that reef species could use to keep pace with climate change. To achieve this, it is essential to characterize their environment as a whole and accurately consider all possible environmental factors that may differ from what is expected in the future, possibly altering the ecosystem response. This study focuses on the semi-enclosed lagoon of Bouraké (New Caledonia, southwest Pacific Ocean) where a healthy reef ecosystem thrives in warm, acidified, and deoxygenated water. We used a multi-scale approach to characterize the main physical-chemical parameters and mapped the benthic community composition (i.e., corals, sponges, and macroalgae). The data revealed that most physical and chemical parameters are regulated by the tide, strongly fluctuate three to four times a day, and are entirely predictable. The seawater pH and dissolved oxygen decrease during falling tide and reach extreme low values at low tide (7.2 pHT and 1.9 mg O2 L−1 at Bouraké vs. 7.9 pHT and 5.5 mg O2 L−1 at reference reefs). Dissolved oxygen, temperature, and pH fluctuate according to the tide by up to 4.91 mg O2 L−1, 6.50 ∘C, and 0.69 pHT units on a single day. Furthermore, the concentration of most of the chemical parameters was 1 to 5 times higher at the Bouraké lagoon, particularly for organic and inorganic carbon and nitrogen but also for some nutrients, notably silicates. Surprisingly, despite extreme environmental conditions and altered seawater chemical composition measured at Bouraké, our results reveal a diverse and high cover community of macroalgae, sponges, and corals accounting for 28, 11, and 66 species, respectively. Both environmental variability and nutrient imbalance might contribute to their survival under such extreme environmental conditions. We describe the natural dynamics of the Bouraké ecosystem and its relevance as a natural laboratory to investigate the benthic organism's adaptive responses to multiple extreme environmental conditions.

First report of Kudoa thunni and Kudoa musculoliquefaciens affecting the quality of commercially harvested yellowfin tuna and broadbill swordfish in Eastern Australia.

Recent anecdotal reports from seafood processors in eastern Australia have described an increased occurrence of post-mortem myoliquefaction ('jellymeat') in broadbill swordfish Xiphias gladius, and macroscopic cysts throughout the musculature of yellowfin tuna Thunnus albacares. A genus of parasitic cnidarians, Kudoa (Myxosporea, Multivalvulida), species of which are known to occur in economically important wild-caught fish species globally, can cause similar quality-deterioration issues. However, Kudoa sp.epizootiology within commercially harvested, high-value fish caught within Australia is poorly understood, despite the parasite's economic importance. To determine the causative agent responsible for the observed quality deterioration in swordfish and yellowfin tuna, muscle-tissue samples from seafood processors in Mooloolaba, Australia, collected from October 2019-February 2020, were examined for parasitic infection. Kudoid myxospores were identified from both hosts and were subquadrate in shape, with four equal-sized polar capsules. The SSU rDNA sequences from both fish shared > 99% identity to Kudoa species. Kudoa musculoliquefaciens was isolated from 87.1% of swordfish sampled, suggesting that it is a widespread parasite in swordfish from the southwest Pacific Ocean. This study provides the first molecular and morphological characterisation of Kudoa thunni in yellowfin tuna and K. musculoliquefaciens in swordfish harvested from the waters of eastern Australia, expanding the geographical distribution of K. thunni and K. musculoliquefaciens to include the Coral and Tasman Seas. We demonstrate that not all infected swordfish progress to jellymeat, show the usefulness of molecular tools for reliably identifying infection by Kudoa spp., and add to the overall knowledge of kudoid epizootiology in wild-caught fish.

Litinium gludi sp. nov. (Nematoda, Oxystominidae) from Kermadec Trench, Southwest Pacific Ocean

Recent work on the taxonomy of nematodes in Southwest Pacific Ocean trenches has led to the discovery of taxa which so far appear to be restricted to the oceans’ deepest environments. Here, Litinium gludi sp. nov. is described based on specimens obtained from a deep basin within the Kermadec Trench at 9540 m water depth. The new species differs from other species of the genus in having a conico-cylindrical tail, papillose labial sensilla, and heart- or leaf-shaped amphideal fovea. Both SSU and LSU phylogenetic analyses provide strong support for the placement of the new species within a clade containing both Thalassoalaimus and Litinum, and within Oxystomininae, which is consistent with the structure of the female reproductive system with only one posterior ovary in this subfamily. Our molecular analyses also indicate that the new species is most closely related to Thalassoalaimus despite lacking a caudal capsule, the main trait characterizing the latter genus, and despite being most morphologically similar to Litinium, particularly in the unusual shape of the amphideal fovea. However, given the changing definitions of the closely-related genera Thalassoalaimus and Litinium in recent years, available GenBank sequences may have been misidentified, which makes the interpretation of molecular phylogenetic analyses problematic. Given the current morphological definitions of Litinium and Thalassoalaimus, we choose to place the new species within Litinium, despite the apparently contradictory findings of molecular phylogenetic analyses. The placement of Cricohalalaimus in a clade with Thalassoalaimus and Litinium in both SSU and LSU analyses indicates that this genus should be placed within the Oxystomininae and not the Halalaiminae as in the current classification. This new proposed grouping is consistent with variation in the structure of the female reproductive system, a feature which appears more taxonomically informative than amphid shape for subfamily-level classification.

Calcareous nannoplankton response to early Eocene warmth, Southwest Pacific Ocean

Episodes of pronounced climatic warming in the early Eocene (56–48 Ma) provide insights into how biological systems might respond to future climate changes. Eocene climate reconstructions for the Southwest (SW) Pacific have proved challenging due to some disparities between geochemical proxy-based estimates for sea temperatures and estimates derived from climate models. Changes in marine phytoplankton populations through the early Eocene provide a means to evaluate model and proxy-based approaches and also reveal how climatic changes affected the ocean ecosystem. This study documents early to middle Eocene calcareous nannofossil assemblages from legacy Deep Sea Drilling Project (DSDP) sites in the SW Pacific. We integrate nannofossil assemblage changes with foraminiferal-based stable isotopes and other microfossil data to provide updated age models for DSDP Sites 207 (Lord Howe Rise) and 277 (Campbell Plateau), and to infer past environmental change through the early to mid-Eocene in the SW Pacific. Although these sites record a short hiatus in the earliest Eocene, deposition resumed by ~54 Ma, prior to the onset of the Early Eocene Climate Optimum (EECO). Both sites show an increase in warm-water taxa from the onset of the EECO until approximately 50.5 Ma. Abundance of warm-water taxa was higher (~23%) at the EECO onset at the more northerly Site 207 and increased only slightly to ~27%, whereas at Site 277 warm-water taxa comprised only ~3% at the EECO onset but increased to ~31% by 50.5 Ma. Cool-water taxa at both sites were present in very sparse numbers (<3%) through much of the EECO and only began to increase in abundance after 50 Ma, concomitant with a decrease in warm-water taxa. These results are similar to other mid-latitude sites in the SW Pacific and Indian Ocean, including mid-Waipara River (Canterbury Basin, New Zealand) and ODP Site 762 (Exmouth Plateau), and indicate assemblages during the EECO are best described as warm temperate. Benthic δ18O records from both sites show good agreement with nannofossil trends and, despite the possibility of recrystallization at Site 277, sea surface temperatures (SSTs) indicated by planktic foraminifera also imply warm temperate conditions. This suggests that a warm proto-East Australian Current extended to at least 55°S during the EECO, displacing the proto-Tasman Front southward, which migrated northward after termination of the EECO possibly due to expansion of a proto-Ross Sea Gyre.

Meta-analysis of the response of marine phytoplankton to nutrient addition and seawater warming

As an indispensable part of the marine ecosystem, phytoplankton are important prey for zooplankton and various marine animals with important commercial value. The influence of seawater warming and eutrophication on phytoplankton communities is well known, but few studies have explained the effects of the interaction between temperature and nutrients on marine phytoplankton. Through meta-analysis and meta-regression, the phytoplankton responses to the effects of nutrient addition and seawater warming were evaluated in this study. Nitrogen (N) addition led to an increase in phytoplankton biomass, while phosphorus (P) had no significant effect on phytoplankton biomass. However, this result may be biased by the uneven distribution of the research area. N limitation is widespread in the areas where these collected studies were conducted, including many parts of North and South Atlantic and West Pacific Oceans. The key limiting nutrient in other areas lacking corresponding experiments, however, remain unclear. The effect of seawater warming was not significant, which indicates the uncertainty about the effect of temperature on phytoplankton. The results of ANOVA show that nutrient addition and seawater warming had similar effects in various marine habitats (coastal regions, estuaries and open seas), while salinity could have caused the difference in the N effects among the three habitats. Furthermore, our results showed that the impact of temperature depends on nutrient conditions, especially N status, which has rarely been considered before. This result demonstrated the importance of evaluating nutrient limitation patterns when studying climate warming. The impact of rising temperatures may need to be reevaluated because N limitation is common.

The mitochondrial genome of hydrothermal vent barnacle Eochionelasmus coreana (Cirripedia: Thoracica) from the Indian Ocean

Balanomorph Eochionelasmus species are hydrothermal vent endemic barnacles. In the genus Eochionelasmus, three species are known to date and they distribute at three different vent fields in Pacific and Indian Oceans, E. ohtai in the Southwest Pacific Ocean, E. paquensis in the East Pacific Ocean, and E. coreana in the Indian Ocean. Therefore, Eochionelasmus species are considered to be a meaningful model taxon to elucidate the evolutionary history of vent organism in relation to geotectonic events. Here, we characterized the partial mitogenome of a newly described vent barnacle Eochionelasmus coreana Chan et al., 2020 from the Solitaire vent field in the Indian Ocean. The length of mitogenome was 16,804 bp with 64.0% AT content. Its gene content and organization was identical to those of E. ohtai. There was one significant part in the mitogenome of E. coreana, which was a long intergenic region over 2 kb found between tRNAPro and tRNAThr. The phylogenetic tree suggested the monophyly of E. ohtai and E. coreana with high supporting values. In the future, additional mitogenome analysis of the last Eochionelasmus species, E. paquensis, could expand our understanding about the speciation and global distribution of Eochionelasmus species.

Fe and S-isotope compositions of hydrothermal deposits from Kings Triple Junction, Lau Basin, southwest Pacific Ocean

We analyzed iron and sulfur isotopic compositions of polymetallic sulfides from an extinct hydrothermal mound near the Kings Triple Junction of the northern Lau basin belonging to a back-arc basin for understanding the origin and mineral zoning processes in this study. Sulfides from the hydrothermal mound's pedestal slab consisting of chalcopyrite and pyrite show enrichment of heavy S-isotope (δ34SV-CDT = +8.3 to +9.6‰). Sphalerite-dominated chimney on the mound's slope also has variable δ34S values between +5.5 and + 8.3‰ from central orifice to outer wall. These isotopic ratios indicate the substantial contribution of heavy isotope rich sulfate-S in seawater circulating within the mound. Low Δ33S values in these sulfides also indicate that the sulfate reduction is of thermal origin, with minimal or no role for microbes. Circulating seawater induced changes in fluid composition and post-depositional zone refinement of certain minerals can explain the variation in δ34S in different layers within the chimney and pedestal slab. The Fe-isotopic compositions (δ56FeIRMM-014) show a range from −1.1 to −0.3‰ in the pedestal slab while they vary between −1.7 and − 0.6‰ at different parts of the peripheral chimney section. We explain such changes are mostly due to redox processes and mineral zoning development during these sulfide deposit formation. The tree-like FeMn oxide growth structures in the vicinity of the hydrothermal mound having a thin birnessite top layer and amorphous iron oxide bottom part show distinct δ56Fe values of −3.0 and − 0.8‰, respectively.

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 &lt;-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.

An Austral radiolarian biozonation for the Paleogene

ABSTRACT: We have integrated southern mid- and high-latitude (Austral) radiolarian biozonations with the well-established low-latitude (Tropical) biozonation using new biostratigraphic and magnetostratigraphic constraints on radiolarian bioevents in the Southwest (SW) Pacific, Southeast (SE) Indian and Northwest (NW) Atlantic Oceans. Our primary study sites include Mead Stream, New Zealand, and DSDP Sites 277 and 207 (SW Pacific; 45-54 degrees South at 50 Ma), ODP Site 752 and IODP Site U1514 (SE Indian; 50 degrees South at 50 Ma), and IODP Site U1403 (NW Atlantic; 30 degrees North at 50 Ma). The Austral and Tropical zonal schemes have been calibrated to GPTS2020. We introduce new zonal codes to rectify current confusion surrounding use of "RP" zones. Austral zones are codified as "RPA" zones and Tropical zones are codified as "RPT". Our study finds that radiolarian datums are generally isochronous within the mid-latitude SW Pacific and SE Indian Oceans from Paleocene to middle Eocene and are also isochronous in the high-latitude Southern Ocean (&gt;60 degrees South paleolatitude) over the late middle Eocene to Oligocene interval of overlap. Older radiolarian assemblages are not known from the Southern Ocean. Early to middle Paleocene radiolarian assemblages in the SE Indian Ocean (zones RPA2-RPA5) differ from coeval SW Pacific assemblages by lacking significant numbers of Cretaceous survivors. The reasons for this difference are uncertain. Although the late Paleocene to Eocene radiolarian assemblages in the SW Pacific and SE Indian Ocean lack many low-latitude index species, the timing of Indian Ocean bioevents agrees better with low-latitude biozonations than the SW Pacific, suggesting a stronger connection with low-latitude watermasses. Assemblages from NW Atlantic IODP Site U1403 include numerous low-latitude index species and can be correlated with zones RPT6-RPT13. Many of the species transitions in biostratigraphically important Eocene lineages, however, occur later than in lower latitudes.

New and known Halichoanolaimus de Man, 1886 species (Nematoda: Selachinematidae) from New Zealand’s continental margin

The Selachinematidae is a globally distributed family of predatory nematodes found from shallow waters to the abyssal plain. Here, three new species of Halichoanolaimus de Man, 1886 (H. ossilagulus sp. nov., H. funestus sp. nov. and H. pumilus sp. nov.) and one known species (H. ovalis Ditlevsen, 1921) are described from the New Zealand continental margin, thus bringing the total number of selachinematid species recorded from the New Zealand region to 14 and the total number of species of Halichoanolaimus to 26. The range of H. ovalis is extended from the Southern Ocean to the Southwest Pacific Ocean (latitude 42° S to 53° S); the depth range of this species, which was originally described from the littoral zone, is also extended to 1061 m depth. Dorsosublateral rows of pore complexes and pseudocoelomocytes, features that have either rarely or not been recorded previously in the genus, were observed in all four species described here. The taxonomic significance of these features remains to be ascertained for the family and will require observations of other species of Halichoanolaimus and selachinematid genera. Pseudocoelomocytes and pore complexes may have an excretory function, thus aiding to process the waste products of digestion in selachinematid taxa with a blind intestine.

Muricauda maritima sp. nov., Muricauda aequoris sp. nov. and Muricauda oceanensis sp. nov., three marine bacteria isolated from seawater.

Three Gram-stain-negative, non-motile, rod-shaped strains, designated 72T, NH166T and 40DY170T, were isolated from seawater samples of the West Pacific Ocean, South China Sea and West Pacific Ocean, respectively. The 16S rRNA gene sequence similarity results revealed that strains 72Tand NH166T were most closely related to Muricauda antarctica Ar-22T, Muricauda taeanensis JCM 17757T, Muricauda beolgyonensis KCTC 23501T, Muricauda lutimaris KCTC 22173T and Muricauda hadalis MT-229T with 97.2-98.0% sequence similarity. 16S rRNA gene sequence analysis also indicated that strain 40DY170T was most closely related to Muricauda ruestringensis DSM 13258T, Muricauda aquimarina JCM 11811T, Muricauda lutimaris KCTC 22173T and Muricauda oceani 501str8T with 97.6-98.1% sequence similarity. The 16S rRNA gene sequence similarity values among strains 72T, NH166T and 40DY170T were 96.5-99.2%. Phylogenetic analyses indicated that three new isolates represented three novel species by forming two distinctive lineages within the genus Muricauda. The DNA G+C contents of strain 72T, NH166T and 40DY170T were 43.4, 43.4 and 42.4 mol%, respectively. The average nucleotide identity and in silico DNA-DNA hybridization values between strains 72T, NH166T, 40DY170T and the reference strains were 76.5-93.5% and 19.2-53.5%, respectively. The sole respiratory quinone in all strains was menaquinone-6. Their major fatty acids were iso-C17:0 3-OH, iso-C15:0 and iso-C15 : 1 G. The major polar lipids of strains 72T and NH166T were phosphatidylethanolamine, one unidentified aminolipid and two unidentified lipids. The major polar lipids of strain 40DY170T were phosphatidylglycerol, one unidentified phospholipid, one unidentified aminolipid and two unidentified lipids. On the basis of their distinct taxonomic characteristics, the three isolates represent three novel species of the genus Muricauda, for which the names Muricauda maritima sp. nov. (type strain 72T=KCTC 62229T=MCCC 1K03350T), Muricauda aequoris sp. nov. (NH166T=KCTC 62228T=MCCC 1K03449T) and Muricauda oceanensis sp. nov. (40DY170T=KCTC 72200T=MCCC 1K03569T) are proposed.

Two New Species of Pseudojuloides from Western Australia and Southern Japan, with a Redescription of Pseudojuloides elongatus (Teleostei: Labridae)

The anti-equatorial labrid Pseudojuloides elongatus has a wide but disjunct distribution across the Western Pacific and Eastern Indian Oceans, with populations occurring in Western Australia, southern Japan, and the southwest Pacific Ocean. Principal component analysis of morphological characters and coalescent-based species-tree estimates of mitochondrial and nuclear DNA markers suggest that these populations are under incipient stages of divergence. The three allopatric populations differ strongly in coloration patterns of both sexes, particularly in terminal males, suggestive of reproductive isolation. We redescribe Pseudojuloides elongatus on the basis of nine paratypes and two additional specimens from eastern Australia and Norfolk Island, and describe two new species, Pseudojuloides crux, new species, from Western Australia, and P. paradiseus, new species, from southern Japan. The complex is distinguished from other members of the genus in sharing the following combination of characters: body elongate; dorsal-fin rays IX,12; pectoral-fin rays 12; no median predorsal scales; and usually 27 lateral-line scales. We briefly comment on anti-equatorial biogeographical patterns and Pseudojuloides argyreogaster from the Western Indian Ocean.

Reconstructing the impact of nickel mining activities on sediment supply to the rivers and the lagoon of South Pacific Islands: Lessons learnt from the Thio early mining site (New Caledonia)

Opencast mining has exacerbated land degradation in New Caledonia, a French archipelago located in the south-west Pacific Ocean. Developed since the 1880s, mining has become the major economic activity in some catchments, which strongly disrupted sediment dynamics. Reconstructing the temporal changes of sediment source contributions is essential to understand the driving factors of soil erosion in response to i) the occurrence of cyclones, ii) the changes in mining practices during the last several decades, and iii) other soil degradation processes such as extensive soil erosion induced by fires, overgrazing and trampling of invasive species, and landslides. Accordingly, a multi-parameter analysis including gamma spectrometry, color and X-ray fluorescence measurements was conducted on a sediment core collected in a deltaic floodplain at the outlet of one of the first areas exploited for nickel mining, the Thio River catchment (397-km2). One geochemical tracer (i.e. K) has been used to quantify changes in sediment sources in the successive sediment layers deposited since the beginning of mining activity. The results showed that the contribution of mining tributaries largely dominated, with a mean contribution of 74% (SD 13%) of material sampled in the sediment core. This contribution notably increased after the mechanization of mining activities (i.e. from 1950s; increase of 18%). The occurrence of Cyclone Alison in 1975 triggered the progressive transfer of mining waste accumulated on the foothills over 25 years into the river system. This tipping point could be identified in the sediment sequence, which demonstrates that over the last 41 years (i.e. 1975–2016), a ~84-cm deep sediment deposit has accumulated in the alluvial floodplain of the Thio River catchment (mean annual deposition rate of 2 cm yr−1). Currently, the progressive release and downstream transfer of this mining waste is still ongoing ~45 years after Cyclone Alison. Although environmental legislation was introduced in 1975, mining tributary contributions to sediment still dominate (80%, SD 5%). Overall, this multi-proxy approach to examining the cumulative effects of mining activities on downstream sediment dynamics could be implemented in other mining catchments of New Caledonia and around the world to compare the respective mining source contributions to sediment and their evolution throughout time in these contrasted areas.

Surface-circulation change in the southwest Pacific Ocean across the Middle Eocene Climatic Optimum: inferences from dinoflagellate cysts and biomarker paleothermometry

Abstract. Global climate cooled from the early Eocene hothouse (∼52–50 Ma) to the latest Eocene (∼34 Ma). At the same time, the tectonic evolution of the Southern Ocean was characterized by the opening and deepening of circum-Antarctic gateways, which affected both surface- and deep-ocean circulation. The Tasmanian Gateway played a key role in regulating ocean throughflow between Australia and Antarctica. Southern Ocean surface currents through and around the Tasmanian Gateway have left recognizable tracers in the spatiotemporal distribution of plankton fossils, including organic-walled dinoflagellate cysts. This spatiotemporal distribution depends on both the physicochemical properties of the water masses and the path of surface-ocean currents. The extent to which climate and tectonics have influenced the distribution and composition of surface currents and thus fossil assemblages has, however, remained unclear. In particular, the contribution of climate change to oceanographic changes, superimposed on long-term and gradual changes induced by tectonics, is still poorly understood. To disentangle the effects of tectonism and climate in the southwest Pacific Ocean, we target a climatic deviation from the long-term Eocene cooling trend: the Middle Eocene Climatic Optimum (MECO; ∼40 Ma). This 500 kyr phase of global warming was unrelated to regional tectonism, and thus provides a test case to investigate the ocean's physicochemical response to climate change alone. We reconstruct changes in surface-water circulation and temperature in and around the Tasmanian Gateway during the MECO through new palynological and organic geochemical records from the central Tasmanian Gateway (Ocean Drilling Program Site 1170), the Otway Basin (southeastern Australia), and the Hampden Beach section (New Zealand). Our results confirm that dinocyst communities track specific surface-ocean currents, yet the variability within the communities can be driven by superimposed temperature change. Together with published results from the east of the Tasmanian Gateway, our new results suggest a shift in surface-ocean circulation during the peak of MECO warmth. Simultaneous with high sea-surface temperatures in the Tasmanian Gateway area, pollen assemblages indicate warm temperate rainforests with paratropical elements along the southeastern margin of Australia. Finally, based on new age constraints, we suggest that a regional southeast Australian transgression might have been coincident with the MECO.

LIPI COREMAP-CTI Nusa Manggala oceanographic survey, I: oceanic mesozooplankton community from epipelagic zones of North-Eastern part of the Indonesian waters -adjacent to the Southwest Pacific Ocean

During the Indonesia LIPI COREMAP CTI oceanographic survey of RV. Baruna Jaya VIII, at the end of 2018 to the outermost small Islands of the north-eastern part of Indonesia, the mesozooplanktonic community were studied for their structure and distribution along the epipelagic zone of the waters influenced by the movement of the southwest Pacific Oceans water masses. This study aimed at exploring the oceanographic condition of the trophic level of the water’s masses during the end of the dry season in Indonesia. A total of 42 taxonomic groups of mesozooplankton were identified, including general fish larvae and eggs. Calanoida and cyclopoid Copepoda dominated (up to 69%) the structure of all survey points. The composition slightly varied across the survey sites, with the abundance of all groups ranged from 24 to 167 ind. per m3. While the main current follows a pattern of the southwest Pacific Ocean, the planktonic community might highlight the condition of the Ocean.

Trans-Pacific genetic differentiation in the deep-water stalked barnacle Scalpellum stearnsii (Cirripedia: Thoracica: Scalpellidae)

Recent advancements in deep-sea expeditions have made possible to sample adequate quantities of deep-sea organisms over wide geographical ranges for population genetic studies. Scalpellum stearnsii is a common stalked barnacle that occurs in the mesobenthic environment (>200 m depth) throughout the West Pacific Ocean and covers several major deep-sea basins. The present study examined the diversity and genetic differentiation of S. stearnsii populations from the East China Sea, West Philippine Basin, Sulu Sea, and Caroline Trenches. Molecular analyses based on partial sequences of the mitochondrial gene COI and nuclear gene H3 revealed four distinct clades of S. stearnsii—SS, CF1, CF2, and CF3—with distinct species-level pairwise divergences among the clades. SS (representing S. stearnsii, based on morphological comparison with holotype) is mainly present in the East China Sea and the Philippine Basin, CF1 is present in the East China Sea, CF2 is present in the Sulu Sea, and CF3 is exclusively present in the Caroline Trench (Southwest Pacific Ocean). Deep genetic differentiation between the northern (SS and CF1) and southern clades (CF2 and CF3) was estimated to have occurred around 33 million years ago, and the eastward-flowing Equatorial Undercurrent (100–200 m) and oxygen minimum zone (300–400 m) are the putative barriers to gene flow. The timing is concordant with reported diversification events in both shallow- and deep-water organisms during the Oligocene and Miocene periods. This cross-ocean, -taxon, and -habitat divergence time suggests speciation driven by global-scale events. Recent size expansion likely occurred in all the four clades and subsequent populations, predating the Last Glacial Maximum (LGM). The persistence of mesobenthic deep-sea barnacles through the temperature fluctuation at the LGM can be a common pattern.