Integrated chronostratigraphy of Magellan Seamount KC-7 in the western Pacific Ocean for Late Neogene paleoceanographic studies

Zischke, M. T., Griffiths, S. P., Tibbetts, I. R., and Lester, R. J. G. 2013. Stock identification of wahoo (Acanthocybium solandri) in the Pacific and Indian Oceans using morphometrics and parasites. – ICES Journal of Marine Science, 70:164–172. The wahoo (Acanthocybium solandri) is an increasingly important by-product species of tropical pelagic fisheries worldwide. However, specific management of the species is currently hindered by a dearth of information on basic biology and stock structure. This study examined the stock structure of wahoo using morphometric characters and parasite fauna from fish collected in three regions of the western Pacific, and one region in each of the eastern Pacific and eastern Indian Oceans. Similar morphometric measurements and parasite abundance of wahoo collected off eastern Australia suggest they may form part of a single phenotypic stock in the western Pacific Ocean. Morphometric measurements and parasite fauna were significantly different among wahoo from the western Pacific and eastern Pacific Oceans, suggesting multiple discrete phenotypic stocks despite genetic homogeneity. Assessing fish from a range of regions throughout the Pacific Ocean may help discriminate stock boundaries in this region. Future research using complementary techniques, such as otolith microchemistry and genetic microsatellites, may improve our understanding of the global stock structure of wahoo to suitably inform regional fishery management organizations.

Association between Antarctic Sea ice, Pacific SST and the Indian summer monsoon: An observational study

We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.

Spatial and temporal differences in the reproductive traits of skipjack tuna Katsuwonus pelamis between the subtropical and temperate western Pacific Ocean

AimTo quantify taxon diversity, biogeographic distributions and patterns of community assembly in xeniid octocorals using molecular operational taxonomic units (MOTUs).LocationRed Sea, Indian and western Pacific Oceans.TaxonXeniidae, a family of reef‐dwelling octocorals (Anthozoa, Octocorallia).MethodsXeniids collected at 13 locations were sequenced at three barcode loci, and assigned to MOTUs defined by minimum genetic distance thresholds. Taxon richness (number of MOTUs) and endemicity (per cent of MOTUs found at a single location) were quantified. Patterns of β‐diversity (species turnover) and phylogenetic β‐diversity (lineage turnover) among geographical regions were visualized using hierarchical clustering, non‐metric multidimensional scaling (NMDS) plots and distance‐decay relationships. Community assembly was investigated by comparing the mean pairwise distance (MPD) and mean nearest taxon distance (MNTD) separating species in each assemblage to values generated for null communities.ResultsA genetic distance threshold of 0.3% discriminated 67 MOTUs, with taxon richness ranging from 2–18 MOTUs per site. Out of the 67 MOTUs, 48 (72%) were found at only a single location, and only two spanned both the western Indian and Pacific Oceans. Species turnover among sites was high, but phylogenetic β‐diversity was lower than β‐diversity and differed significantly from null models of community assembly at only two sites. β‐diversity and phylogenetic β‐diversity both increased significantly with geographic distance, and sites clustered into three distinct biogeographic regions (Red Sea and western Indian Ocean; Western Australia; western Pacific Ocean and Great Barrier Reef, Australia). All five major clades of xeniids were represented in each region.Main conclusionsA genetic approach to biodiversity estimation suggests that most xeniid taxa are regional endemics whose geographic distribution is likely governed by dispersal limitation. This conclusion contrasts with published records of certain morphospecies occurrences, which imply that they have broad geographic ranges. So far, the distribution of xeniid biodiversity mirrors that of scleractinian corals, with species richness highest in the Coral Triangle, but endemicity peaking in peripheral areas.

Sea surface temperature (SST) variations associated with the atmospheric intraseasonal oscillation in the tropical Indian and western Pacific Oceans, are examined using a one-dimensional mixed layer model. Surface fluxes associated with 10 well-defined intraseasonal events from the period 1986‐93 are used to force the model. Surface winds from the European Centre for Medium-Range Weather Forecasts daily analyses and SST from the mixed layer model are used to compute latent and sensible heat fluxes and wind stress with the TOGA COARE bulk flux algorithm. Surface freshwater flux is estimated from the Microwave Sounding Unit precipitation data. Net shortwave radiation is estimated, via regression analysis, from outgoing longwave radiation. An idealized diurnal cycle of shortwave radiation is also imposed. The intraseasonal SST variation from the model, when forced by the surface fluxes estimated from gridded analyses, agrees well with the SST observed at a mooring during the COARE. The model was then integrated for the 10 well-defined intraseasonal events at grid points from 758 to 1758 Ea t 58S, which spans the warm pool of the equatorial Indian and western Pacific Oceans. The one-dimensional model is able to simulate the amplitude of the observed intraseasonal SST variation throughout this domain. Variations of shortwave radiation and latent heat flux are equally important for driving the SST variations in the western Pacific, while latent heat flux variations are less important in the Indian Ocean. The phasing of the intraseasonal variation of precipitation relative to wind stress results in little impact of the freshwater flux variation on the intraseasonally varying mixed layer. The diurnal cycle of shortwave radiation is found to significantly increase the intraseasonal amplitude of SST over that produced by daily mean insolation.

Understanding genetic diversity and population structure is essential for effective fisheries management. This study examined the population genetic structure, diversity, and demography of the red big eye Priacanthus macracanthus, a commercially crucial species in the western Pacific and eastern Indian Oceans, by using mitochondrial DNA cytochrome b (cytb) gene sequences (1,141 bp). A total of 206 samples were collected from 9 locations, and 101 haplotypes were obtained. Analysis revealed that (1) all haplotypes clustered into two sympatric haplogroups; (2) although the genetic distance between these haplogroups was small, nucleotide substitution patterns indicated distinct evolutionary histories; (3) migration and haplogroup distribution patterns suggested that the two haplogroups may have originated from different sources, eastern Indian Ocean and the western Pacific Ocean; and (4) recent population declines and low nucleotide diversity indicated a need for targeted management strategies. These findings provide valuable insights that can guide fisheries management and future research on the conservation of P. macracanthus populations.

Many species of Halymenia from the Indo-Pacific have been described in the past decade, but their phylogenetic relationships are not well discussed. In this study, we inferred these relationships for the available species of Halymenia with an emphasis on the foliose species from the western Pacific Ocean and Western Australia based on rbcL and nuclear-encoded LSU rDNA sequence analyses. Our analyses show that most foliose Halymenia from the Indo-Pacific are clustered in a natural assemblage that also includes a new species (Halymenia taiwanensis sp. nov.) found in northern Taiwan, as well as the monospecific genus Austroepiphloea (single species A. bullosa) from Western Australia. The architecture of carpogonial branch (composed of a two-celled carpogonial branch and two orders of ampullar filaments, and a basal, nutritive cellular cluster) and auxiliary cell ampullae in Halymenia taiwanensis is similar to that found in the generitype H. floresii. We therefore propose the new combination Halymenia bullosa comb. nov. (basionym Schizymenia. bullosa), a species closely related to H. taiwanensis both genetically and morphologically. However, H. taiwanensis can be separated from H. bullosa by its thinner blades and surface bladelets, and by lacking a long cartilaginous stipe. Based on the rbcL phylogeny, most foliose Halymenia are seemingly more range-restricted than previously thought, except for a few species that are shown to have a wide distribution in the Western Pacific and Indian Oceans. In addition, H. dilatata, a species widely recorded in the Western Pacific Ocean, may include cryptic species and requires further investigation.

Abundance and diversity of antibiotic resistance genes and bacterial communities in the western Pacific and Southern Oceans

We assess the effects of the North Atlantic Ocean Sea Surface Temperature (NASST) on North East Asian (NEA) surface temperature. We use a set of sensitivity experiments, performed with MetUM-GOML2, an atmospheric general circulation model coupled to a multi-level ocean mixed layer model, to mimic warming and cooling over the North Atlantic Ocean. Results show that a warming of the NASST is associated with a significant warming over NEA. Two mechanisms are pointed out to explain the NASST—North East Asia surface temperature relationship. First, the warming of the NASST is associated with a modulation of the northern hemisphere circulation, due to the propagation of a Rossby wave (i.e. the circumglobal teleconnection). The change in the atmosphere circulation is associated with advections of heat from the Pacific Ocean to NEA and with an increase in net surface shortwave radiation over NEA, both acting to increase NEA surface temperature. Second, the warming of the NASST is associated with a cooling (warming) over the eastern (western) Pacific Ocean, which modulates the circulation over the western Pacific Ocean and NEA. Additional simulations, in which Pacific Ocean sea surface temperatures are kept constant, show that the modulation of the circumglobal teleconnection is key to explaining impacts of the NASST on NEA surface temperature.

Sulfur hexafluoride in the marine atmosphere and surface seawater of the Western Pacific and Eastern Indian Ocean

Seasonal to interannual variations of the net surface heating (FNET) and its relationship to sea surface temperature tendency (dTs/dt) in the tropical eastern Indian and western Pacific Oceans are studied for the period October 1997–September 2000. The surface heat fluxes are derived from the Special Sensor Microwave Imager and Japanese Geostationary Meteorological Satellite radiance measurements. It is found that the magnitude of solar heating is larger than that of evaporative cooling, but the spatial variation of the latter is significantly larger than the former. As a result, the spatial patterns of the seasonal and interannual variability of FNET are dominated by the variability of evaporative cooling. Seasonal variations of FNET and dTs/dt are significantly correlated, except for the equatorial western Pacific. The high correlation is augmented by the high negative correlation between solar heating and evaporative cooling. The change of FNET between the 1997/98 El Niño and 1998/99 La Niña is significantly larger in the tropical eastern Indian Ocean than that in the tropical western Pacific. For the former region, reduced evaporative cooling arising from weakened winds during El Niño is generally associated with enhanced solar heating due to reduced cloudiness, leading to enhanced interannual variability of FNET. For the latter region, reduced evaporative cooling due to weakened winds is generally associated with reduced solar heating arising from increased cloudiness, and vice versa. Consequently, the interannual variability of FNET is reduced. The correlation between interannual variations of FNET and dTs/dt is weak in the tropical western Pacific and eastern Indian Oceans, indicating the importance of ocean dynamics in affecting the interannual SST variation.

Five polymorphic microsatellite loci were examined in 1391 yellowfin tuna (Thunnusalbacares) from eight regions of the western (Coral Sea, eastern Australia, Fiji, Indonesia, Philippines and Solomon Islands) and eastern (California and Mexico ) Pacific Ocean. Across all samples, numbers of alleles per locus ranged from 7 to 30 (mean: 17.0), and observed heterozygosities per locus ranged from 0.223 to 0.955 (mean: 0.593). Temporal collections were available for three areas: no significant temporal heterogeneity was observed for the Coral Sea (1991/1992 and 1995/1996 collections) or eastern Australia (1994/1995, 1995/1996, 1996/1997 and 1997/1998), but there was slight but significant heterogeneity at one locus (cmrTa-161) between the two Philippines collections (1994/1995 and 1996/1997). Genotypes generally showed a good fit to Hardy–Weinberg expectations within populations; only cmrTa-208 in the pooled Coral Sea population gave a significant deviation after Bonferroni correction for 40 tests, with a small but significant excess of homozygotes. Four loci showed no evidence of population differentiation following contingency Chi-squared and FST analyses. The fifth locus, cmrTa-161, showed small but significant differentiation (FST=0.002, P<0.001). This heterogeneity was largely a result of the Philippines 1994/1995 and Fiji collections; there was no correlation with geographic distance. The average FST across all five loci was very low (FST=0.002), but it was significant (P<0.001). It is unclear whether this low but significant differentiation reflects noise in the dataset, perhaps arising from experimental error, or real population differentiation. The finding of very limited population heterogeneity accords with most of the earlier allozyme and mitochondrial DNA studies of yellowfin tuna in the Pacific Ocean.

Hadley Cells are thermally driven cell in the tropics. On its occurrence, these cells are strongly influenced by the sea surface temperature (SST) distribution across the tropical ocean or the Pacific Ocean as the investigated location in this study. The SST shifting in the Pacific Ocean is mainly due to the ENSO. An opposite SST polarity between the western and eastern Pacific Ocean are captured during ENSO events. This means that ENSO could trigger an anomalous regional Hadley Cells that behave oppositely between Indonesia or the western Pacific and the eastern Pacific. This study examines the strength of the regional Hadley Cells related to the ENSO event across the Indonesian region and the Pacific Ocean. A significant correlation between the Hadley Cells and ENSO as the tropical climate variability in the Pacific Oceans are found. The strength of the Hadley Cells associated with ENSO event is examined by using the zonally average vertical velocity across the Pacific Ocean. During La Nina, the regional Hadley Cells over Indonesia or the western Pacific strengthened, whereas the regional cells over the eastern Pacific weakened. In contrast, during El Nino where the warm pool shifted to the eastern Pacific, the regional cell in the eastern Pacific strengthened, while the cell over the western Pacific weakened. These anomalous conditions clearly show that the meridional temperature gradient is strongly affecting the regional Hadley Cells strength. The stronger the meridional temperature gradient, the stronger the regional Hadley Cells.

Western Pacific is the water mass intersection from both the Northern Pacific and Southern Pacific ocean. The Western Pacific ocean is warm pool area which formed by several warm surface currents. As a warm pool area and also the water mass intersection, western Pacific ocean becomes an interesting study area. The object of this study is to describe the temperature vertical distribution by mooring buoy and temporally in transitional season II (September – November 2014) and west monsoon (December 2014 – February 2015) in Western Pacific. Vertical temperature and wind speed data that was used in this study was recorded by INA-TRITON mooring instrument and obtained from Laboratory of Marine Survey, BPPT. Supporting data of this study was wind vector data from ECMWF to observe the relation between temperature distribution and monsoon. The quantitative approach was used in this study by processing temperature and wind data from INA-TRITON and interpreted graphically. In the area of study, it was found that in transitional season II the range of sea surface temperature to 500-meter depth was about 8.29 – 29.90 °C while in west monsoon was 8.12 - 29.45 °C. According to the research result, the sea SST of western Pacific ocean was related to monsoonal change with SST and wind speed correlation coefficient was 0.78. While the deep layer temperature was affected by water mass flow which passes through the western Pacific Ocean.