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Standardised taxonomic field guide used to develop (please cite as): Simon-Lledó, et al. (2023). Carbonate compensation depth drives abyssal biogeography in the northeast Pacific. Nature Ecology & Evolution; doi:10.1038/s41559-023-02122-9 The APSMA image-based catalogue This code-based abyssal megafauna (invertebrates > 1 cm) catalogue was developed by morphological and taxonomical alignment of specimens encountered in seabed imagery collected in 28 seabed locations across the Clarion Clipperton Fracture Zone, in the NE Pacific basin (see Simon-Lledó et al. 2023, for further details). This work was conducted during a range of scientific workshops held between 2016 and 2021, in collaboration with taxonomic experts (see acknowledgements section) and by reference to existing literature (e.g. where available, links to studies describing collected specimens are provided in taxon descriptions). The catalogue follows the Horton et al. 2021 open nomenclature (e.g. 10.3389/fmars.2021.620702) to report the taxonomic resolution reached in the identification of each classified metazoan morphotype. Each morphotype was assigned a unique 7 character identification code (i.e. “XXX_nnn”). All taxa identified were deemed as sufficiently different morphologically by taxonomic experts to be confidently considered separate species. Note the catalogue is periodically revised, as new photographed and collected specimens get examined, and hence some taxonomic identifications may vary in subsequent versions of this guide. The latest version of the APSMA catalogue is available as label tree for image/video annotation on BIIGLE (biigle.de; please contact the authors for more detail).

A comprehensive understanding of the deep-sea environment and mining’s likely impacts is necessary to assess whether and under what conditions deep-seabed mining operations comply with the International Seabed Authority’s obligations to prevent ‘serious harm’ and ensure the ‘effective protection of the marine environment from harmful effects’ in accordance with the United Nations Convention on the Law of the Sea. A synthesis of the peer-reviewed literature and consultations with deep-seabed mining stakeholders revealed that, despite an increase in deep-sea research, there are few categories of publicly available scientific knowledge comprehensive enough to enable evidence-based decision-making regarding environmental management, including whether to proceed with mining in regions where exploration contracts have been granted by the International Seabed Authority. Further information on deep-sea environmental baselines and mining impacts is critical for this emerging industry. Closing the scientific gaps related to deep-seabed mining is a monumental task that is essential to fulfilling the overarching obligation to prevent serious harm and ensure effective protection, and will require clear direction, substantial resources, and robust coordination and collaboration. Based on the information gathered, we propose a potential high-level road map of activities that could stimulate a much-needed discussion on the steps that should be taken to close key scientific gaps before any exploitation is considered. These steps include the definition of environmental goals and objectives, the establishment of an international research agenda to generate new deep-sea environmental, biological, and ecological information, and the synthesis of data that already exist.

A new species of chionelasmatid sessile vent barnacle, Eochionelasmus coreana sp. nov., is described and illustrated on the basis of specimens collected from the Solitaire hydrothermal vent field in the Central Indian Ridge of the Indian Ocean. This new species is morphologically very similar to E. ohtai, the type species of the genus Eochionelasmus. However, it differs from E. ohtai in its distribution, the status of the notch on the maxillule, and the positions of rl1 and cl1 on whorls of the imbricating plates. In addition, a molecular phylogenetic tree indicated that the chionelasmatid Eochionelasmus was closely related to the waikalasmatid Waikalasma with high supporting values rather than the other chionelasmatid Chionelasmus. The new species is not only the first record of a sessile vent barnacle from outside of the Pacific Ocean, but is also the first sessile barnacle 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 Pacifi...

Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone. The extent of impact by midwater discharge plumes from deep-sea nodule mining will be influenced by the quantity of plume sediment, ocean turbulence and acceptable environmental thresholds, according to numerical modelling and direct experiments

Since deep-sea hydrothermal vents have been targeted for mining mineral resources, concerns about the potential impacts of mining on vent ecosystems have gradually increased. The vent alvinocaridid shrimp is one of the dominant endemic vent organisms. We collected an experimental species, Nautilocaris saintlaurentae, from the Tonga Arc in the Southwest Pacific Ocean, and firstly determined the sequences of seven housekeeping genes (HKGs) and three stress-related genes in this study. The stability of the HKGs was evaluated and the expression levels of targeted genes were measured in different body parts, the cephalothorax, abdomen, and whole body, to provide information on which parts of nonmodel species can be used for ecotoxicological studies. Based on geNorm platform, multiple combinations of HKGs were tested. The stability of the HKG expression in each body part indicated that the cephalothorax can be used alone and also demonstrated that using at least three HKGs provides suitable interpretations for mRNA real-time quantitative PCR arrays in N. saintlaurentae. Although analysis of specific body part subdivisions was not carried out, our results suggested that anatomical characteristics should be considered when investigating biological functions at a molecular level. Finally, this study revealed upregulation of stress-responsive genes in the cephalothorax of N. saintlaurentae with environmental changes.

Understanding the fate of terrestrial plant waxes from source to sink is critical for improving paleoclimate interpretations from sedimentary plant waxes. However, there is limited knowledge about the controls on plant wax integration and transport in large catchments with multiple biomes and climates. To address this lack of understanding, we investigated the vegetation and climatic controls on plant wax integration and transport from the Mississippi River Basin (MRB), the largest river in the U.S., to the Gulf of Mexico (GOM). We first estimated the geographic distribution of n-alkane carbon (δ13Calk) and hydrogen (δ2Halk) isotopic compositions (i.e. isoscapes) in the MRB using plant isotope fractionation calibrations from North America and similar climate regions for the pre-industrial. We utilized two different vegetation maps (i.e. biome map and %C4 map) and two plant isotope fractionation estimation approaches, and discussed advantages and disadvantages of each method. Then, we developed mixing models weighting the isotope values by biological and climatic parameters (i.e. vegetation area, n-alkane concentration by chain lengths, net primary productivity (NPP), and runoff) and their combinations to test the sensitivity of basin-integrated plant wax isotopic compositions to these variables. Our approach does not factor in soil stocks of plant wax nor degradation in transit, as future work will need to constrain these factors for the MRB for the period of interest. Vegetation area weighting alone predicted relatively high C4 plant contributions to the pool of waxes exported from the basin. When n-alkane concentration in leaves, NPP, or runoff was considered, the contribution of forest-derived plant waxes increased. Sensitivity of plant wax isotopic compositions to productivity and transport efficiency varied among models and chain lengths. For example, n-C29 alkanes were sensitive to plant wax contribution increases from forests whereas n-C33 alkanes were more sensitive to increases in C4 grassland productivity. The plant wax concentration and NPP were combined as an estimate for total wax productivity, and a combination of this total wax productivity and runoff were used to simulate both production and transport. These multi-parameter models estimated the highest plant wax contribution from C3 forests because these areas were calculated to have the highest productivity and greatest runoff. Despite large differences in δ13Calk and δ2Halk values across the MRB, variation in the predicted δ13C and δ2H of exported n-alkanes is small across all models. This small range is consistent with a calculated predominance of plant wax export from wet and tree-dominated biomes and suggests that drier and C4 grass-dominated biomes may be under-represented in the sedimentary plant wax record.

Macrofauna are an abundant and diverse component of abyssal benthic communities and are likely to be heavily impacted by polymetallic nodule mining in the Clarion-Clipperton Zone (CCZ). In 2012, the International Seabed Authority (ISA) used available benthic biodiversity data and environmental proxies to establish nine no-mining areas, called Areas of Particular Environmental Interest (APEIs) in the CCZ. The APEIs were intended as a representative system of protected areas to safeguard biodiversity and ecosystem function across the region from mining impacts. Since 2012, a number of research programs have collected additional ecological baseline data from the CCZ. We assemble and analyze macrofaunal biodiversity data sets from eight studies, focusing on three dominant taxa (Polychaeta, Tanaidacea, and Isopoda), and encompassing 477 box-core samples to address the following questions: (1) How do macrofaunal abundance, biodiversity, and community structure vary across the CCZ, and what are the potential ecological drivers? (2) How representative are APEIs of the nearest contractor areas? (3) How broadly do macrofaunal species range across the CCZ region? and (4) What scientific gaps hinder our understanding of macrofaunal biodiversity and biogeography in the CCZ? Our analyses led us to hypothesize that sampling efficiencies vary across macrofaunal data sets from the CCZ, making quantitative comparisons between studies challenging. Nonetheless, we found that macrofaunal abundance and diversity varied substantially across the CCZ, likely due in part to variations in particulate organic carbon (POC) flux and nodule abundance. Most macrofaunal species were collected only as singletons or doubletons, with additional species still accumulating rapidly at all sites, and with most collected species appearing to be new to science. Thus, macrofaunal diversity remains poorly sampled and described across the CCZ, especially within APEIs, where a total of nine box cores have been taken across three APEIs. Some common macrofaunal species ranged over 600–3000 km, while other locally abundant species were collected across ≤ 200 km. The vast majority of macrofaunal species are rare, have been collected only at single sites, and may have restricted ranges. Major impediments to understanding baseline conditions of macrofaunal biodiversity across the CCZ include: (1) limited taxonomic description and/or barcoding of the diverse macrofauna, (2) inadequate sampling in most of the CCZ, especially within APEIs, and (3) lack of consistent sampling protocols and efficiencies.

Fatty acids (FAs) are the main components of lipids in corals. We examined FA profiles from five symbiotic coral species belonging to five different genera (Acropora, Pavona, Turbinaria, Favites and Platygyra) and four different families (Acroporidae, Agariciidae, Dendrophyllidae, Faviidae). We separated symbionts from coral host tissue to investigate the interaction of FA between symbionts and host tissue. After separation, we used FA profiles, in particular specific FAs (e.g. 16:0, 18:0, 18:3n-3, 20:5n-3, 22:6n-3) and their ratios (EPA:DHA, PUFA:SFA) as biomarkers to examine chemotaxonomic indication and trophic level (autotrophy vs. heterotrophy) of each coral species. Gas chromatography-mass spectrometry (GC-MS) was performed to identify and quantify FA. For quantification, the dry weight of total lipids was used to normalize FA concentration (μg mg-1). We found that 1) FA profiles and their abundance in coral host tissue and symbionts are distinct (with the exception of autotrophic species) 2) our five different coral species are defined by species-specific FA profiles, 3) certain FAs are useful biomarkers to determine relative trophic strategies (i.e. autotrophy and/or heterotrophy, 4) the application of FA ratios to define trophic level requires caution in research application and data interpretation. Considering the limitations of FA ratios determined herein, we suggest it to be more appropriate if these FA ratios were only applied to examine response to environmental change within species. Going forward, our study provides important FA baseline data that builds the foundation to future investigations on impacts of environmental changes on nutrition and metabolism in symbiotic corals.

The hitherto suborder Verrucomorpha contains asymmetrical barnacles of two groups: the true Verrucomorpha (Eoverruca + Verrucidae) and the Neoverrucidae. Here, we determined the mitochondrial genome (mitogenome) of Altiverruca navicula, a true Verrucomorpha species. The mitogenome was 15,976 base pairs in length and had the typical pancrustacean gene arrangement. Its protein-coding genes were very similar to those of other thoracican species in terms of length, AT content, and start and stop codons. In phylogenetic trees constructed with 13 protein-coding genes, A. navicula was positioned at an ancestral node of sessile barnacles, consistent with the findings of previous studies.

Imbricaverruca and Neoverruca are two genera of hydrothermal vent asymmetrical barnacles in Neoverrucidae, but found in vents of the Southwest Pacific and Northwest Pacific Oceans, respectively. Imbricaverruca has a flattened operculum and the shell base with multiple whorls of imbricating plates, while Neoverruca has an inclined operculum and the shell base with fewer developed imbricating plates. It has been hypothesized that Imbricaverruca has apomorphic shell characters in Neoverrucidae. Although the monophyletic relationship of the vent barnacle members in the superfamily Neolepadoidea were confirmed based on molecular phylogeny, the relationships between Neobrachylepadidae and Neoverrucidae, and between Neoverruca and Imbricaverruca have not been determined because there are no molecular data on Imbricaverruca. In this study, we sequenced three nuclear (18S rDNA, 28S rDNA, histone 3) and one mitochondrial (CO1) genes of I. yamaguchii from the Southwest Pacific. Our phylogenetic results showed that Neobrahchylepadidae is the sister taxon to Neoverrucidae (Imbricaverruca + Neoverruca), and Imbricaverruca and Neoverruca are monophyletic sister taxa each other, which not supporting the previous hypothesis that Neoverruca is sister to the clade containing Neobrahchylepadidae and Neolepadidae. These implied that the differences in shell forms between Neoverruca and Imbricaverruca are a result of independent divergent evolution in different deep-sea basins.

The family Eolepadidae is the only stalked barnacle in hydrothermal vent regions. Here, we determined the mitogenome of the eolepadid Vulcanolepas fijiensis. The mitogenome was 17,374 bp long, with 76.6% AT content. Its protein-coding gene organization was identical to that of the deep-sea scalpellid Arcoscalpellum epeeum. On the mitogenomic tree, two scalpellomorphan families (Eolepadidae and Scalpellidae) were monophyletic while the other scalpellomorphan family Pollicipedidae did not form the monophyletic group with them. Further mitogenomic analysis of undetermined taxa in hydrothermal vents is required to deepen our understanding of their phylogenetic relationships.

Host–symbiont relationships in hydrothermal vent ecosystems, supported by chemoautotrophic bacteria as primary producers, have been extensively studied. However, the process by which densely populated co‐occurring invertebrate hosts form symbiotic relationships with bacterial symbionts remains unclear. Here, we analyzed gill‐associated symbiotic bacteria (gill symbionts) of five co‐occurring hosts, three mollusks (“Bathymodiolus” manusensis, B. brevior, and Alviniconcha strummeri) and two crustaceans (Rimicaris variabilis and Austinograea alayseae), collected together at a single vent site in the Tonga Arc. We observed both different compositions of gill symbionts and the presence of unshared operational taxonomic units (OTUs). In addition, the total number of OTUs was greater for crustacean hosts than for mollusks. The phylogenetic relationship trees of gill symbionts suggest that γ‐proteobacterial gill symbionts have coevolved with their hosts toward reinforcement of host specificity, while campylobacterial Sulfurovum species found across various hosts and habitats are opportunistic associates. Our results confirm that gill symbiont communities differ among co‐occurring vent invertebrates and indicate that hosts are closely related with their gill symbiont communities. Considering the given resources available at a single site, differentiation of gill symbionts seems to be a useful strategy for obtaining nutrition and energy while avoiding competition among both hosts and gill symbionts., This study is the first comparison of gill symbiont communities of co‐occurring invertebrates living at a single hydrothermal vent site. We observed both different compositions of gill symbionts and the presence of unshared operational taxonomic units, as well as the representative sulfur‐oxidizing γ‐proteobacterial species which is suggested to have coevolved with their hosts toward reinforcing host specificity. Considering the given resources at a single site, differentiation of gill symbionts is a useful strategy for obtaining nutrition and energy while avoiding competition among both hosts and gill symbionts.

Euphausia pacifica (E. pacifica) is an important food source for fish and other organisms in marine ecosystems. We analyzed the carbon- and nitrogen-stable isotope ratios in potential diet sources to determine the feeding characteristics of E. pacifica in the Yellow Sea Cold Water Mass (YSCWM), a habitat for oversummering. E. pacifica was collected in the spring and summer from the central and coastal parts of the Yellow Sea from 2012 to 2014, and potential prey were collected in summer 2014. Although the δ13C values of E. pacifica differed significantly in spring each year, they narrowed to a specific range in summer. The δ15N values were always 2‰ higher in summer than in spring, suggesting that the diet of E. pacifica inhabiting the YSCWM was limited. In coastal stations, the contribution of any major food source calculated using an isotope mixing model was not more than 20%, suggesting that E. pacifica is omnivorous. However, at two stations in the YSCWM, 2.0–5.0-mm and > 5-mm plankton contributed 42 and 22% of their diet on average, respectively. These results indicate that E. pacifica inhabiting waters affected by cold water feeds on relatively large zooplankton such as the copepods Calanus sinicus. Therefore, the YSCWM likely plays a role in the trophic shift of E. pacifica during the summer.

We examined the biogenic and lithogenic particle composition and radiocarbon content of sinking particulate organic carbon to investigate sediment resuspension and its contribution to sinking particles on the deep abyssal plain of the Eastern Tropical Pacific Ocean. Samples were collected using sediment traps from August 2011 to July 2012 at depths of 4500 and 4950 m (50 m above the seafloor); above and within the benthic nepheloid layer (BNL), respectively. Biogenic particles derived from export production were the major source of sinking particles and their flux showed a unimodal temporal distribution, with larger values between February and April. At a depth of 4500 m, the lithogenic material flux was slightly greater than, or similar to, the flux of atmospheric dust deposition. In comparison, lithogenic material and excess Mn consistently showed a greater contribution to resuspended particles at 4950 m. The lithogenic material flux was proportional to the biogenic flux. These observations imply that resuspended particles exist at a background concentration in the BNL throughout the year, and are scavenged by sinking biogenic particles, especially during the high flux period.

The spatial distributions of δ13C, δ15N, and n-alkanes were investigated to determine the source and transportation of allochthonous organic matter from the mouth of the Seomjin River to the southern inner shelf break of Korea. Total organic carbon (%) ranged from 0.3% to 1.6% (average = 0.80%, n = 81), and the C/N ratio varied from 2.4 to 12.4 (average = 6.76, n = 81). The δ13C values ranged from −25.86 to −20.26‰ (average = −21.47‰, n = 81), and δ15N values ranged from 4.37‰ to 8.57‰ (average = 6.72‰, n = 81). The contribution of the terrestrial fraction of organic matter to the total ranged from 4.4% to 97.7% (average = 24.4%, n = 81), suggesting higher amounts around the catchment area and lower amounts in the offshore area. The concentration of total n-alkanes (nC25 − nC35) was higher at the boundary between the outer bay and inner shelf break (BOBIS). Average chain length and the carbon preference index both indicated that major leaf wax n-alkanes accounted for the observed distribution of terrestrial organic matter, and were dominant in the inner shelf break (around BOBIS) and outer shelf break. Based on the spatial distribution of the total n-alkanes and the sum of nC27, nC29, and nC31, the terrestrial organic matter distribution was considered to be controlled by local oceanographic conditions, especially at the center of the BOBIS. In addition to enabling the distribution and source of terrestrial organic matter to be identified, the n-alkanes indicated that minor anthropogenic allochthonous organic materials were superimposed on the total organic materials in the central part of Yeosu Bay and the catchment area. The n-alkane indices revealed weathered petroleum contamination, with contamination levels being relatively low at the present time.

This study reports the first finding of tropical blacklip pearl (BLP) oyster, Pinctada margaritifera, in Korean waters. One BLP oyster was found and sampled from Beom-seom islet (33°13′N, 126°33′E) in the southern coast of Jeju Island, Korea in February, 2011. The taxonomic status of the specimen was confirmed by nucleotide sequences of the mitochondrial gene cytochrome oxidase I and 28S ribosomal DNA. Oxygen isotopic analysis (δ18Osh) and histology were used to determine the specimen’s age and reproductive stage, which were 3.5 years and ripe male, respectively. This BLP oyster most likely originated in an area in the subtropics or tropics, such as the Okinawa archipelagic or Micronesian regions. We suggest that intensive monitoring surveys are necessary for confirming the northward expansion of BLP oyster in Korean waters in the near future.

The effect of iron (Fe) fertilization on biological productivity and community structure in the equatorial Pacific, a region with high nutrient and low chlorophyll concentrations, has been debated for many years. Here we present lipid biomarker and geochemical proxy records in a sediment core from the central equatorial Pacific spanning from 1100 to 600 ka to investigate the response of marine phytoplankton communities to eolian Fe supply and to assess links to environmental fluctuations during the Pleistocene. We found a strong link between change in eolian Fe input and phytoplankton community structure. Our data demonstrate that an increase in eolian Fe supply across the 800 ka boundary resulted in a shift in the major primary producer from coccolithophores (alkenones) to diatoms (epi-brassicasterol) and dinoflagellates (dinosterol) at the study site. This strong link between changes in eolian Fe supply and the community structure of plankton during 800–600 ka may have been associated with a change in atmospheric and ocean conditions due to southward migration of the Intertropical Convergence Zone (ITCZ). The lipid biomarker results show that such a high supply of eolian Fe might have led to a change in the dominant phytoplankton group. However, the opal record, which is often used as a primary productivity indicator, was not consistent with the biomarker results. Therefore, the results indicate that multi-proxy approaches should be used in paleoenvironmental studies because different proxies can reveal different aspects of environmental conditions, thus contributing to a better understanding of paleoceanographic conditions.

Although the response unit of living organisms to environmental changes is at the individual level, most experiments on the adaptation responses of ciliates have been conducted in batches, comprising multiple-individuals, due to their microscopic size. However, here, we confirmed that individuals undergo different division cycles in monocultures of Euplotes crassus. They also exhibited transcript variations of 4.63-fold in SSU and of 22.78- fold in Hsp70. Additionally, in salt-stressed E. crassus individuals, SSU transcripts of individuals varied by 6.92-fold at 27 psu, 8.69- fold at 32 psu, and 2.51-fold at 37 psu. However, the maximum difference in Hsp70 was only 4.23-fold under all conditions. These results suggest there may be different biological rhythms even in siblings derived from the same parent. It can also be inferred that various environmental factors have different effects on different E. crassus individuals. Therefore, to elucidate relationships between organism adaptations and environmental changes, studies at the individual level should be conducted with multi-individual approaches.

The family Provannidae is endemic to chemosynthetic environments in the deep-sea. Here, we report the complete mitogenome of a provannid vent snail Alviniconcha boucheti from the North Fiji Basin f...

A new species of eolepadid stalked barnacle, Vulcanolepas fijiensis sp. nov., was collected from a hydrothermal vent in the North Fiji Basin, Southwestern Pacific Ocean, at a depth of 1988 m. Based on morphological characteristics, this new species was distinguished from its relatives, V. osheai Buckeridge, 2000, V. parensis Southward, 2005, V. scotiaensis Buckeridge, Linse & Jackson, 2013, and V. buckeridgei Chan & Chang, 2018. Based on morphological characteristics, Vulcanolepas species are divided mainly into two groups by the size of the first mandibular tooth; the first group has a large mandibular first tooth (V. parensis, V. scotiaensis, and V. fijiensis sp. nov., the second a small mandibular first tooth (V. osheai and V. buckeridgei). The new species can be easily distinguished from V. parensis and V. scotiaensis by the length ratio of antenniform segments to robust segments of the rami of cirrus I. Vulcanolepas fijiensis sp. nov. also differs from V. parensis by the length ratio of the penis and cirrus VI (1/10 vs 1/4), and the extension the carinal apex to the tergum (extended vs not extended). Additionally, the sequence divergence of the cytochrome c oxidase 1 gene between V. fijiensis sp. nov. and the other neolepadid species (except V. parensis from its original locations) ranged from 4.2% to 14.0%. In a neighbor-joining tree, V. fijiensis sp. nov. formed an independent branch. These results infer that V. fijiensis sp. nov. is a new species, distinct from the other known neolepadids.

Studies of sinking particles associated with hydrothermal vent fluids may help us to quantify mass transformation processes between hydrothermal vent plumes and deposits. Such studies may also help us understand how various types of hydrothermal systems influence particle flux and composition. However, the nature of particle precipitation out of hydrothermal vent plumes in the volcanic arcs of convergent plate boundaries has not been well studied, nor have the characteristics of such particles been compared with the characteristics of sinking particles at divergent boundaries. We examined sinking particles collected by sediment traps for about 10 days at two sites, each within 200 m of identified hydrothermal vents in the south Tonga arc of the southwestern Pacific. The total mass flux was several-fold higher than in the non-hydrothermal southwest tropical Pacific. The contribution of non-biogenic materials was dominant (over 72%) and the contribution of metals such as Fe, Mn, Cu, and Zn was very high compared to their average levels in the upper continental crust. The particle flux and composition indicate that hydrothermal authigenic particles are the dominant source of the collected sinking particles. Overall, our elemental ratios are similar to observations of particles at the divergent plate boundary in the East Pacific Rise (EPR). Thus, the nature of the hydrothermal particles collected in the south Tonga arc is probably not drastically different from particles in the EPR region. However, we observed consistent differences between the two sites within the Tonga arc, in terms of the contribution of non-biogenic material, the radiocarbon content of sinking particulate organic carbon, the ratios of iron to other metals (e.g. Cu/Fe and Zn/Fe), and plume maturity indices (e.g. S/Fe). This heterogeneity within the Tonga arc is likely caused by differences in physical environment such as water depth, phase separation due to subcritical boiling and associated sub-seafloor precipitation.

Little is known regarding how harmful algal bloom species respond to different temperatures in terms of fatty acid production. This study examined the effects of temperature on the growth rates, cell volumes, and fatty acid concentrations and compositions of four harmful algal bloom species (HABs), Akashiwo sanguinea, Alexandrium tamarense, Chattonella ovata, and Prorocentrum minimum. The HABs species were cultured at 15, 20, 25, and 30°C in a nutrient-enriched medium. Three of the species maintained optimal growth rates over a wide range of temperatures, but A. tamarense did not. The cell volumes of each species showed little change over the temperature range. The total fatty acid concentrations in A. sanguinea, A. tamarense and C. ovata decreased as the temperature increased, but P. minimum showed no trend in this respect. Polyunsaturated fatty acids (PUFAs), the key biochemical components that maintain cell membrane fluidity and which are associated with toxicity, decreased in both concentration and proportion of total fatty acids as temperature increased, except in A. sanguinea, in which the proportion of PUFAs to the total fatty acids increased. These reductions in PUFA concentration and proportion could reduce cell membrane fluidity and toxicity in HABs; however, enhanced growth and/or ruptured cells, which are considered more toxic than intact cells, could compensate for the reduced per-cell toxicity. This phenomenon might impact on the marine ecosystem and aquaculture industry.

To track the diet of minke whale (Balaenoptera acutorostrata) in the East Sea (Japan Sea), a conjoint analysis of fatty acids and C and N stable isotopes was performed on blubber and skin from the whale and its potential prey. The total lipid content in the blubber of minke whales ranged from 37.9% to 82.7% of wet mass (mean ± SD, 63.1 ± 17.2%), with triacylglycerols being the dominant lipids (96.9%–99.2% of total lipids). The lipid and fatty acid (FA) contents were systematically stratified throughout the depth of the blubber layers; contents of the dominant monounsaturated FAs (MUFAs), including 18:1ω9 and 16:1ω7, increased from the innermost layer to the outermost layer, whereas contents of saturated FAs (SFAs) and polyunsaturated FAs (PUFAs) were higher in the innermost layer than in the outermost layer. This stratification is related to the different physiological roles of the blubber layers; e.g., thermoregulation, streaming, and buoyancy. A comparison of the FA compositions of the innermost layer of minke whales with those of potential prey indicates that FA compositions in the whales are similar to those of Pacific herring. In addition, stable isotope ratios (δ13C and δ15N) suggest that minke whale and Pacific herring have the same or similar diets. Therefore, the diets of minke whale from the East Sea (Japan Sea) could be inferred from information on the diet of the Pacific herring, although FA compositions and stable isotope ratios for Pacific herring would not exactly reflect the whale’s diet. Although the very limited number of samples was used in this study, our preliminary findings are very promising to help understand the feeding ecology of minke whales in the East Sea (Japan Sea).

To understand the diet of chaetognaths, the gut content and fatty acid trophic makers (FATMs) of Sagitta crassa and S. nagae, which are the most predominant species of chaetognath in the Yellow Sea, were analyzed. Gut contents of the two species examined by microscopic analysis revealed that copepods are the major components of the diet (> 70% of gut contents) and there was no significant changes in the gut contents of two species collected in spring and summer season. Although 16:0, 20:5(n-3) (Eicosapentaenoic acid) and 22:6(n-3) (Docosahexanoic acid), which are known as phytoplankton FA markers, were the most dominant among the fatty acids in both chaetognath species, the detection of copepod FA markers, 20:1(n-9) (Gadoleic acid) and 22:1(n-11) (Cetoleic acid), provided evidence that their food sources include copepods. These results suggest that S. crassa and S. nagae are carnivores and mainly feed on copepods in the Yellow Sea.

Corals reefs and communities support a wide range of flora and fauna. The complete richness and abundance of faunal communities in either coral reefs or communities is not fully understood. This is especially true for high-latitude coral communities. In this work, we carried out an analysis of an Alveopora japonica associated mollusk assemblage, in Jeju Island, Korea. A. japonica is one of the major coral species present in high abundance (88–155 colonies m-2), with a high recruitment rate (7.8 juvenile corals m-2 yr-1) in Jeju Island, and may serve as a habitat for other benthic organisms. In 2012, a total number of 579 A. japonica colonies with sizes ranging between 15.1-346.7 cm2 in the surface area were collected from a 1m× 10m quadrat installed at a depth of 10 m at Keumneung, on the northwest coast of Jeju Island. Numerous benthic invertebrates were found to be associated with A. japonica colonies. Twenty-seven bivalves and gastropods were identified, including a boring mytilid, Lithophaga curta, and an arcid, Barbatia stearnsi. A zonalgeographical examination of the distribution ranges of these mollusks revealed a majority of warmer water species. Our observations also showed that A. japonica may be providing a habitat to grazing gastropod, Turbo cornutus, and encrusting Spondylidae and Chamidae bivalves. A. japonica forms a coral carpet with a distinct assemblage of bivalves. It is thought that the presence of these mollusks species in the coral indicates its use as a nursery for juvenile species, a ready food supply of organic detritus, and a refuge from predators.

A new species of callianassid ghost shrimp,Paraglypturus tonganussp. nov., is described and illustrated on the basis of five specimens that were collected from sediments in a vent field of the Tonga Arc, south-western Pacific Ocean. This new species is morphologically very similar toP. calderusTürkay & Sakai, 1995, the type species of the genusParaglypturusTürkay & Sakai, 1995. It differs fromP. calderusmainly in the absence (vs. presence inP. calderus) of an anterolateral row of setal pores on the carapace; the endopod of the second maxilliped, with a dactylus bearing stiff and thick serrate setae at the apex (vs. without inP. calderus); a yellow circular structure located on the ventral surface on the uropodal endopod (vs. on the dorsal surface on the uropodal exopod inP. calderus); and the articulation structure of the first pleopod in males (uniarticulate inP. tonganusvs. biarticulate inP. calderus). The new species is the first record of a ghost shrimp from a vent field of the Tonga Arc, and also the second reported species of the genusParaglypturus.

The Amundsen Sea is characterized by a continental shelf, long-term sea ice, and many coastal polynyas with high biological productivity. Euphausia superba and Euphausia crystallorophias , which are dominant Antarctic krill, are major prey for most predators, such as fishes, birds, and marine mammals. An understanding of the feeding ecology of krill may provide the information for the structure and function of the Amundsen Sea ecosystem. Thus, we applied two biochemical approaches (fatty acids and stable isotopes) to determine the trophodynamics of adult krill in the Amundsen Sea. There were no significant differences in lipid contents between the two species, but the dominant storage lipids were different. Triacylglycerol (TAG) was dominant in E. superba , but wax esters (WE) were dominant in E. crystallorophias due to their different living strategies. Furthermore, the lipid content of E. crystallorophias displayed a spatial variation, being highest on the glacial edge. It was difficult to understand the feeding strategy and food source using only the fatty acid compositions of krill and in situ particulate organic matter. However, we found that specific FA ratios (18:1ω9/18:1ω7 and PUFA/SFA) and the nitrogen isotope ratio (δ 15 N) provide more insight into the feeding ecology of krill, such as feeding strategy and trophic position. These ratios suggest that E. crystallorophias consistently showed a higher degree of carnivorous feeding than E. superba in the Amundsen Sea during the austral summer. In conclusion, adult E. superba might more directly obtain their energy from in situ primary producers in the open sea, but, in the Amundsen Sea Polynya, adult E. crystallorophias seems to obtain their energy mainly through the microbial loop (microzooplankton). If so, E. crystallolophias would be a key player not only to transfer the energy from microbes to higher trophic levels but also to control the carbon and nitrogen cycle in the Amundsen Sea Polynya.

The family Eolepadidae is the only stalked barnacle in hydrothermal vent regions. Here, we determined the mitogenome of the eolepadid Vulcanolepas fijiensis. The mitogenome was 17,374 bp long, with...

Microalgae hold promise as producers of sustainable biomass for the production of biofuels and other biomaterials. However, the selection of strains with efficient and robust production of desirable resources remains challenging. In this study, we isolated a green microalga from Korea and analyzed its morphological, molecular, and biochemical characteristics. Microscopic and phylogenetic analyses demonstrated that the isolate could be classified into the genus Chlamydomonas, and we designated the isolate Chlamydomonas s p. K IOST -1. Compositions of protein, lipid, and carbohydrate in the microalgal cells were estimated to be 58.8 ± 0.2%, 22.7 ± 1.2%, and 18.5 ± 1.0%, respectively. Similar to other microalgae belonging to Chlorophyceae, the dominant amino acid and monosaccharide in Chlamydomonas sp. KIOST-1 were glutamic acid and glucose. On the other hand, the proportions of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids clearly differed from other species in the genus Chlamydomonas, and monounsaturated fatty acids accounted for a large portion (41.3%) of the total fatty acids in the isolate. Based on these results, Chlamydomonas sp. KIOST-1 has advantageous characteristics for biomass production.

A unicellular red microalga was isolated from environmental freshwater in Korea, and its morphological, molecular, and biochemical properties were characterized. Morphological analysis revealed that the isolate was a unicellular biflagellated green microalga that formed a non-motile, thick-walled palmelloid or red aplanospore. To determine the taxonomical position of the isolate, its 18S rRNA and rbcL genes were sequenced and phylogenetic analysis was performed. We found that the isolate was clustered together with other related Haematococcus strains showing differences in the rbcL gene. Therefore, the isolated microalga was classified into the genus Haematococcus, and finally designated Haematococcus sp. KORDI03. The microalga could be cultivated in various culture media under a broad range of pH and temperature conditions. Compositions of the microalgal cellular components were analyzed, and its protein, carbohydrate, and lipid compositions were estimated to be 21.1 ± 0.2%, 48.8 ± 1.8%, and 22.2 ± 0.9%, respectively. In addition, D-glucose and D-mannose were the dominant monosaccharides in the isolate, and its amino acids were composed mainly of aspartic acid, glutamic acid, alanine, and leucine. Moreover, several polyunsaturated fatty acids accounted for about 80% of the total fatty acids in Haematococcus sp. KORDI03, and the astaxanthin content in the red aplanospores was estimated to be 1.8% of the dry cell weight. To the best of our knowledge, this is the first report of an Haematococcus sp. isolated from Korea, which may be used for bioresource production in the microalgal industry.

Non-monophyletic Poecilasmatids are deep-water epibiotic barnacles and are classified as five-capitular-plate members of the Lepadiformes. Here, we offer the first characterization of the mitogenome of a Poecilasmatid barnacle (Glyptelasma annandalei). The mitogenome was 16,107 bp long, with 72.3% AT content. Its gene arrangement was identical to that of the lepadids Lepas anserifera and L. australis, except for the location of the tRNASer gene. On the mitogenomic tree, two Lepadiformes families (Poecilasmatidae and Lepadidae) were monophyletic, which concurs with the findings of previous studies. Further mitogenomic analysis of undetermined Lepadiformes taxa is required to deepen our understanding of their phylogeny and evolution.