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Introduction. In the equatorial Pacific Ocean, the El Nino-Southern Oscillation substantially affects atmospheric and oceanic conditions on interannual time scales. The central and eastern equatorial Pacific fluctuates between anomalously warm [...]

Abstract--We examined the stomach contents of 3 vertically migrating myctophid fish species from the eastern tropical Pacific (ETP) Ocean and used a classification tree to examine the influence of spatial, [...]

Abstract--Jumbo squid (Dosidicus gigas) and purpleback squid (Sthenoteuthis oualaniensis) (Teuthida: Ommastrephidae) are thought to spawn in the eastern tropical Pacific. We used 10 years of plankton tow and oceanographic data [...]

We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Nino--Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical mode[ simulations of orbital forcing into a La Nina--like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Nino--like (warm) conditions, in apparent agreement with the theoretical 'ocean dynamical thermostat' response of ENSO to exogenous radiative forcing. 10.1126/science.1194887

SUMMARY The seafloor within Canada's Exclusive Economic Zone in the northeastern Pacific Ocean features examples of three kinds of volcanic activity: mid-ocean ridge, near-ridge seamount, and intraplate seamount volcanism. Volcanism [...]

Domes of the Sumisu volcanic complex (western Pacific), having summits at ocean depths of 1100, 600, 245, and 95 m, are mantled with compositionally identical rhyolitic pumice that has similar vesicularity, but that varies systematically in distribution, size, and surface texture--suggesting that facies and morphology can serve as useful indicators of eruption depth. At depths >500 m, the pumice formed a thick carapace on dense rhyolite and disintegrated by quench fracture and mechanical failure into a jumble of giant (meters to tens of meters) polyhedral blocks with smooth curviplanar surfaces that display a single quenched margin. Vesiculation was arrested on eruption in seawater in all but the interior of the thickest carapace. At doi: 10.1130/G30500.1

Decadal-scale climate variations over the Pacific Ocean and its surroundings are strongly related to the so-called Pacific decadal oscillation (PDO) which is coherent with wintertime climate over North America and Asian monsoon, and have important impacts on marine ecosystems and fisheries. In a near-term climate prediction covering the period up to 2030, we require knowledge of the future state of internal variations in the climate system such as the PDO as well as the global warming signal. We perform sets of ensemble hindcast and forecast experiments using a coupled atmosphere-ocean climate model to examine the predictability of internal variations on decadal timescales, in addition to the response to external forcing due to changes in concentrations of greenhouse gases and aerosols, volcanic activity, and solar cycle variations. Our results highlight that an initialization of the upper-ocean state using historical observations is effective for successful hindcasts of the PDO and has a great impact on future predictions. Ensemble hindcasts for the 20th century demonstrate a predictive skill in the upper-ocean temperature over almost a decade, particularly around the Kuroshio-Oyashio extension (KOE) and subtropical oceanic frontal regions where the PDO signals are observed strongest. A negative tendency of the predicted PDO phase in the coming decade will enhance the rising trend in surface air-temperature (SAT) over east Asia and over the KOE region, and suppress it along the west coasts of North and South America and over the equatorial Pacific. This suppression will contribute to a slowing down of the global-mean SAT rise. doi/10.1073/pnas.0906531107

We compare two intraplate, Pliocene-Pleistocene volcanic fields in different tectonic settings--the central Basin and Range and the northwest Pacific Ocean. Both fields are characterized by widely scattered, small-volume, alkali basaltic volcanoes; within the fields, each volcano apparently originates from a separate, volatile-enriched parental melt from the upper mantle. There is no evidence at either field for locally anomalous heat flow or ongoing introduction of new fluids into the upper mantle such as might occur above a subducting slab. We conclude that the volcanic fields reflect deformation-driven collection of already existing partial melts in a heterogeneous upper mantle. Deformation-driven melt collection may be an important mechanism for other diffuse intraplate volcanic fields, and this is consistent with a tectonically controlled, low-flux end member for intraplate fields where magmatism is a passive response to regional deformation. Differences in the degree of fractionation and contamination between the two fields are inferred to be related to flexure-induced vertical variations in the orientation of principal stresses in the northwest Pacific Ocean, which cause stalling of ascending dikes in the lithosphere. doi: 10.1130/G30427.1

Seawater C[O.sub.2] system dynamics were assessed from eastern Pacific reef sites in Panama over 5 consecutive years (2003-2008) and twice in the Galapagos Islands (2003 and 2009). The seawater C[O.sub.2] system was highly variable in time and space, but was explained by physical forcing from meteorological (seasonal rainfall) and oceanographic (upwelling, tides) processes interacting with diurnal reef metabolism. Galapagos coral reef communities are naturally exposed to the highest ambient partial pressure of C[O.sub.2] (pC[O.sub.2]) and lowest aragonite saturation ([[OMEGA].sub.arag]) values documented for any coral reef environment to date. During upwelling in the Galapagos, mean pC[O.sub.2] and mean [[OMEGA].sub.arag] at five different sites ranged from 53.1 to 73.5 Pa and 2.27 to 2.86, respectively. Values of pC[O.sub.2] and [[OMEGA].sub.arag] ranged from 21.0 to 48.7 Pa and 2.47 to 4.18, respectively, on the Saboga Reef in the seasonally upwelling Gulf of Panama, with the highest pC[O.sub.2] and lowest [[OMEGA].sub.arag] values occurring during upwelling. The Uva Reef, in the nonupwelling Gulf of Chiriqui of Pacific Panama, had mean [[OMEGA].sub.arag] values that were always significantly greater than those at the Saboga Reef. Diurnal changes in the seawater C[O.sub.2] system from reef metabolism on the Uva Reef were magnified at low tide and highly significant differences were measured over depths as shallow as 15 m because of the shallow thermocline that is pervasive throughout the eastern Pacific. These naturally high-C[O.sub.2] reefs persist near the [[OMEGA].sub.arag] distributional threshold for coral reefs and are thus expected to be the first and most affected by ocean acidification.

Explosive eruptions from subaerial arc volcanoes can have significant environmental impact because of the discharge of ash and volatiles directly into the atmosphere and oceans. The link between climate cooling and voluminous volcanic eruptions has remained speculative due to a lack of supporting evidence. A compilation of 2814 K-Ar and [sup.40]Ar/[sup.39]Ar age determinations from four circum-Pacific arcs indicates that periods of high volcanic output (i.e., flare-ups) have been episodic and, in some cases, synchronous. Peak periods and subsequent lulls in arc magmatism over the past 50 m.y. have occurred coeval with major fluctuations in global climate, including the Eocene-Oligocene transition, one of the most prominent global climate reorganizations in the Cenozoic. Hundreds of intermediate to silicic eruptions occurred during an extremely vigorous period of circum-Pacific volcanism beginning in the late Eocene, which likely led to the production of sulfur aerosols in the stratosphere and fertilization of surface waters of the Pacific Ocean. We provide a mechanism that may have been partly responsible for the climatic preconditioning that must have preceded and ultimately promoted Antarctic ice sheet growth ~34 m.y. ago.

The paleoceanographic history of the Pacific Ocean during the mid-Cretaceous is poorly constrained due to the loss of much of the contemporaneous Pacific seafloor to subduction and difficulties in recovering chert-rich sediments by ocean drilling. Pelagic sediments that were originally deposited in the Pacific Ocean but that have been subsequently accreted during subduction potentially provide an alternative paleoceanographic archive. This study presents micropaleontological and carbon-isotope data from the Calera Limestone, part of the classic Franciscan Complex exposed in Permanente Quarry, central California, USA. In the three stratigraphic sections studied, pelagic limestones with low organic-carbon contents are the dominant lithology. However, two stratigraphic intervals are recognized that contain organic carbon, and these date to the early Aptian and late Albian--early Cenomanian. These time intervals correspond to two mid-Cretaceous oceanic anoxic events (OAEs): early Aptian OAE1a (equivalent to the 'Selli level') and late Albian OAE1d (equivalent to the 'Breistroffer event'). It is well established that both of these events were associated with significant carbon-isotope excursions, which are also shown to exist in the Calera Limestone. The record of OAE1a from the Calera Limestone complements ocean drilling records by providing further evidence for variability in the sedimentary and stratigraphic record of this event. The carbon-isotope data from the late Albian--early Cenomanian provide the first detailed chemobiostratigraphic record of this period for the Pacific Ocean, confirming that environmental change occurred at this time in the Pacific, possibly related to OAE1d. Keywords: Cretaceous, oceanic anoxic events, carbon isotopes, Calera Limestone, paleoceanography.

We use geochemical data from a sediment core in the shallow-silled and intermittently dysoxic Kau Bay in Halmahera (Indonesia, lat 1[degrees]N, long 127.5[degrees]E) to reconstruct century-scale climate variability within the Western Pacific Warm Pool over the past ~3500 yr. Downcore variations in bulk sedimentary [[delta].sup.15]N appear to reflect century-scale variability in basin ventilation, attributed to changes in oceanographic conditions related to century-scale fluctuations in El Nino Southern Oscillation (ENSO). We infer an increase in century-scale El Nino activity beginning ca. 1700 yr B.P. with peaks in El Nino activity ca. 1500 yr B.P., 1150 yr B.P., and ca. 700 yr B.P. The Kau Bay results suggest that there was diminished ENSO amplitude or frequency, or a departure from El Nino--like conditions during the Medieval Warm Period, and distinctive, but steadily decreasing, El Nino activity during and after the Little Ice Age. Keywords: climate, El Nino Southern Oscillation, Western Pacific Warm Pool, Indonesia.

[1] We present a novel explanation for absolute trench-normal motions of slabs surrounding the Pacific. Rapid subduction-zone retreat on the eastern side of the Pacific and slow advance in the west can result from the large-scale asymmetric plate configuration. We use simple fluid dynamics to explain the mechanical background of this hypothesis, and we use the results of a simple finite difference scheme to estimate the effect on trench motion velocities. The hypothesis is based on two key assumptions. First, we follow the concept of platescale horizontal counterflow in the asthenosphere driven by accretion of asthenosphere into lithosphere and by plate motion. Second, we assume that horizontally wide slabs without large slab windows drift passively in the mantle flow field and do not retreat as a result of flow around the slab. If the asthenosphere transfers flow-related horizontal shear stress into deeper levels of the mantle, an asymmetry in the plate configuration leads to different net pressure forces on the two slabs and thus affects the retreat behavior. In an ocean with an asymmetric ridge position, the slab of the smaller plate should retreat faster than the slab of the large plate, which may even advance. Also, the domain of a slower moving plate should collapse faster than the domain of the faster plate. Our model explains the counterintuitive negative correlation between slab age and retreat velocity observed in the Pacific. It also accords with the topographic asymmetry of the ridge flanks along the Pacific rise. Citation: Nagel, T. J., W. B. F. Ryan, A. Malinverno, and W. R. Buck (2008), Pacific trench motions controlled by the asymmetric plate configuration, Tectonics, 2 7, TC3005, doi:10.1029/2007TC002183.

Research capable of differentiating resource-related community-level change from random ecological drift in natural systems has been limited. Evidence for nonrandom, resource-driven change is presented here for an epibenthic megafauna community in the abyssal northeast Pacific Ocean from 1989 to 2004. The sinking particulate organic carbon food supply is linked not only to species-specific abundances, but also to species composition and equitability. Shifts in rank abundance distributions (RADs) and evenness, from more to less equitable, correlated to increased food supply during La Nina phases of the El Nino Southern Oscillation. The results suggest that each taxon exhibited a differential response to a sufficiently low dimension resource, which led to changes in community composition and equitability. Thus the shifts were not likely due to random ecological drift. Although the community can undergo population-level variations of one or more orders of magnitude, and the shape of the RADs was variable, the organization retained a significant consistency, providing evidence of limits for such changes. The growing evidence for limited resource-driven changes in RADs and evenness further emphasizes the potential importance of temporally variable disequilibria in understanding why communities have certain basic attributes. Key words: California Current Ecosystem (CCE); climate; deep sea; echinoderm; holothuroid; Long-Term Ecological Research (LTER); megafauna; niche hierarchy; ophiuroid; pelagic-benthic coupling; rank abundance; relative abundance.

The Cretaceous has long been recognized as a time when greenhouse conditions were fueled by elevated atmospheric C[O.sub.2] and accompanied by perturbations of the global carbon cycle described as oceanic anoxic events (OAEs). Yet, the magnitude and frequency of temperature change during this interval of warm and equable climate are poorly constrained. Here we present a high-resolution record of sea-surface temperatures (SSTs) reconstructed using the [TEX.sub.86] paleothermometer for a sequence of early Aptian organic-rich sediments deposited during the first Cretaceous OAE (OAE1a) at Shatsky Rise in the tropical Pacific. SSTs range from ~30 to ~36[degrees]C and include two prominent cooling episodes of ~4 [degrees]C. The cooler temperatures reflect significant temperature instability in the tropics likely triggered by changes in carbon cycling induced by enhanced burial of organic matter. SST instability recorded during the early Aptian in the Pacific is comparable to that reported for the late AIbian-early Cenomanian in the Atlantic, suggesting that such climate perturbations may have recurred during the Cretaceous with concomitant consequences for biota and the marine environment. Keywords: [TEX.sub.86] index, oceanic anoxic events, Cretaceous sediments, carbon isotopes.

The Ross Sea region of the East Antarctic plate provides evidence for intraplate tectonic activity in Cenozoic times. Still unresolved arc the cause, timing and kinematics of this intraplate tectonism. By integrating and discussing the different (kinematic and temporal) signals of Cenozoic tectonism, intraplate dextral shearing is recognized as the main tectonic regime controlling the structural architecture of the Ross Sea region from the Mid-Eocene (c. 40-50 Ma) onward. We speculate that propagation and persistence of this tectonic regime through time constitutes a feasible seismogenetic framework to explain past and current tectonism in the Ross Sea region.

Export of pelagic carbonate tests from surface waters and their deposition at the seafloor plays a significant role in the C[O.sub.2] cycle and ability of the oceans to absorb atmospheric C[O.sub.2]. Sediment [sup.230]Th and [sup.3]He measurements have been interpreted as evidence that significant lateral advection of pelagic material occurs in the water column, leading to marked spatial variations in deposition rates and, in particular, to significant focusing of deposits on the Pacific equator. We report spatially continuous stratigraphy from two 1000 km seismic lines that show evidence of depositional anomalies near the equator. Accumulation rates were apparently enhanced locally by a factor of two, similar to the proposed modern sediment-focusing factors, but the anomalies are surprisingly patchy over the 20 m.y. period analyzed--they are not confined to an equatorial region, and they are not necessarily found on adjacent seismic profiles. These intermediate-scale anomalies are >~100 km across and represent areas of seafloor that received more deposits for one period, less in following periods, and vice versa. Variogram analysis was used to determine how the spatial scales of deposition changed over the Neogene. The period when the spatial scale of depositional variability was largest correlates with hiatuses in drill cores, a correlation that we interpret as caused by enhanced and spatially heterogeneous carbonate dissolution at that time. The study suggests that seismic stratigraphy has the potential to reveal spatial patterns related to unsteady bottom-water flow and chemistry. Keywords: pelagic carbonate seismic stratigraphy, sediment focusing, pelagic carbonate dissolution, Pacific Ocean circulation, variogram analysis.

Measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial Pacific deep-sea cores suggest that during peak glacial time the radiocarbon age of water at 2-kilometers depth was no greater than that of today. These results make unlikely suggestions that a slowdown in deep-ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon-14 ([sup.14]C) to carbon in the atmosphere and surface ocean during glacial time. Comparison of 14C ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean [sup.14]C to C ratio difference was not substantially different from today's., Hughen et al. (1) present a strong case that during the last glacial maximum (LGM) (i.e., 22,000 to 16,000 calendar years ago) the [sup.14]C to C ratio in the atmosphere [...]

ABSTRACT The non native Mediterranean mussel Mytilus galloprovincialis is broadly established in the northeast Pacific. Until recently, the coast north of Humboldt Bay, California, USA, was not considered a major [...]

Invertebrate communities inhabiting deep-sea hydrothermal vents undergo substantial succession on time scales of months. Manipulative field experiments assessed the relative roles of environmental state and biotic interactions in determining temporal succession along a spatial gradient in vent fluid flux at three vent sites near 9[degrees]50' N on the East Pacific Rise (2500 m water depth). Species colonization patterns on cubic basalt blocks (10 cm on a side) deployed by the submersible Alvin revealed both positive (facilitation) and negative (inhibition) biological interactions, in the context of established succession theory. Over a series of four cruises from 1994 to 1998, blocks were exposed to colonists for consecutive and continuous intervals in short-term (5 + 8 = 13 mo) and longer-term (8 + 29 = 37 mo) experiments. Colonists grouped into a mobile functional group were less abundant in the continuous interval (13 mo) than in the synchronous pooled-consecutive intervals (5 + 8 mo) of the short-term experiment, indicating that early colonists inhibited subsequent recruitment. Colonists grouped into a sessile functional group exhibited the opposite pattern, indicating facilitation. Similar trends, though not statistically significant, were observed in the longer-term experiment. The character of species interactions varied along a gradient in hydrothermal fluid flux (and inferred productivity), with inhibitory interactions more prominent in zones with high temperatures, productivity, and faunal densities, and facilitative interactions appearing where temperatures, productivity, and densities were low. Analyses of primary succession on introduced basalt blocks suggest that biological interactions during early vent community development strongly modify initial patterns of settlement, even in the absence of sustained temporal change in the vent fluid flux. Key words: deep sea; facilitation; hydrothermal vent; inhibition; Lepetodrilus; limpet; Ophryotrocha; polychaete; productivity gradient; succession; tubeworm; vestimentiferan.

Few studies have examined the partitioning of organic matter in upwelling systems, despite the fact that these systems play a key role in carbon and nitrogen budgets in the ocean. We examined the production and partitioning of phytoplankton-derived organic matter in deck incubations off Oregon during the upwelling season. During exponential growth of the phytoplankton, [greater than or equal to] 78% of total accumulated organic matter was in particulate (POM) form. This suggests that dissolved organic matter (DOM) is a small fraction of primary production during the exponential growth of coastal phytoplankton blooms. After nitrate depletion, carbon-rich (C : N [greater than or equal to] 16) DOM accumulated in incubations dominated by the diatom Chaetoceros sp., accounting for 38% ([+ or -] 8.5%) of accumulated total organic carbon (TOC) and 24% ([+ or -] 8%) of accumulated total organic nitrogen (TON). However, in a bloom dominated by the diatom Leptocylindrus rninimus, a relatively smaller amount of DOM accumulated, accounting for only 15% of accumulated TOC and 7% of accumulated TON. On the basis of measured concentrations of nitrate and accumulated TOC, ~70%-157% more carbon was fixed than would be predicted by Redfield stoichiometry (referred to as 'excess carbon fixation'), with 20%-69% of the excess carbon fixation occurring after nitrate depletion. The accumulation of carbon-rich DOM and excess carbon fixation suggests that nitrate assimilation (i.e., new production) might not equate to net production of POM in coastal upwelling systems.

Whereas ENSO's interannual impact on the global climate and the carbon cycle is well established (1-3), the role of the tropical Pacific in long-time-scale climate change remains controversial (4, 5). [...], Much uncertainty surrounds the interactions between the El Nino-Southern Oscillation (ENSO) and long-term global change. Past periods of extreme global warmth, exemplified by the Eocene (55 to 35 million years ago), provide a good testing ground for theories for this interaction. Here, we compare Eocene coup[ed climate model simulations with annually resolved variability records preserved in lake sediments. The simulations show Pacific deep-ocean and high-latitude surface warming of ~ 10°C but little change in the tropical thermocline structure, atmosphere-ocean dynamics, and ENSO, in agreement with proxies. This result contrasts with theories linking past and future 'hothouse' climates with a shift toward a permanent El Nino-like state.

Abundance and life-cycle features of the mesopelagic hyperiid amphipod Primno abyssalis (formerly P. macropa) in the Oyashio region, western subarctic Pacific, were investigated using samples collected between July 1996 and July 1998. P. abyssalis was collected throughout the entire survey period, with abundance peaks occurring in spring to autumn. While all maturity stages of males and females were observed throughout the study period, the peak reproduction season was in summer. Instar analysis based on the segment number of the pleopod rami indicated that hatched juveniles molted 10 times before becoming adult males and 13 times before becoming adult females. Judging from the dry and ash-free dry weights of each instar, males and females continued to feed throughout the final instar stage. Based on cohort analysis of seasonal samples and laboratory observations on molting frequencies, growth in body length of P. abyssalis was linear with time, and estimated generation lengths were 2.3-3.8 years for females and 1.4-1.9 years for males. Brood size of females ranged from 66 to 337 and increased with increasing female body length. Lifetime fecundity, calculated as the sum of six successive broods, was 1,004. Compared with P. abyssalis in the southern Sea of Japan, those in the Oyashio region have a larger number of adult instars (six versus five for females, three 3 vs one for males), a lower growth rate (0.014 mm [day.sup.-1] vs 0.021 mm [day.sup.-1]), and mature earlier (instar 13 vs instar 15 for females; instar 10 vs instar 11 for males). These characteristics are considered to be advantageous life-history traits to counteract higher niche competition within the mesopelagic community and higher predation pressure by mesopelagic fishes in the Oyashio region than in the Sea of Japan.

The nucleotide sequence of part (624 bp) of a mitochondrial gene for cytochrome oxidase I was determined for 46 escarpiid vestimentiferans collected from seven sites in the western Pacific and 49 individual specimens of Arcovestia ivanovi from two sites in the Manus Basin. Phylogenetic analysis, based on the newly obtained and previously reported sequences, indicated that escarpiids in the western Pacific can be divided into two tentative species, as we proposed in a previous report. While members of the first tentative species have been collected exclusively from a seep area at a depth of 300 m off the coast of central Japan, the members of the second species inhabit some sites at depths greater than 1,100 m, namely, seep areas in Japanese and Papua-New Guinean waters as well as hydrothermal vent fields in the Okinawa Trough and the Manus Basin. We detected no genetic structure among populations of the second tentative species. The first tentative species was more closely related to a species in the eastern Pacific, Escarpia spicata, and to a species in the Gulf of Mexico, Escarpia laminata, than to the second tentative species in the western Pacific. Sequences obtained from all arcovestiids were identical with the exception of those from three individuals, each of which included a single synonymous nucleotide substitution relative to the dominant haplo-type, and no genetic differences were detected between specimens from the two sites in the Manus Basin.

Data from the Western Pacific Environment Study on CO(2) Ocean Sequestration for Mitigation of Climate Change (WEST-COSMIC) are presented for copepod communities of the Pacific Ocean. Biomass and abundance were highest in the surface layer and lowest at increased depths. A power regression model best describes decreases in abundance, while an exponential regression model best describes decreases in biomass.

A cloud-resolving model coupled to an ocean model with high vertical resolution is used to investigate air-sea interactions in 10-day long simulations. Modeled fields showed good agreement with two different convective regimes during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Research Experiment (TOGA COARE) Intensive Observing Period. The model simulates the formation of precipitation-produced, stable freshwater lenses at the top of the ocean mixed layer, with a variety of horizontal dimensions and lifetimes. The simulated fresh anomalies show realistic features, such as a positive correlation between salinity and temperature, the development of a surface jet in the direction of the wind, and, as a consequence, downwelling (upwelling) on its downwind (upwind) edge. The dataset generated by the coupled model is used to evaluate the contribution from several factors (ocean currents, gustiness, and correlations between wind speed and air temperature, wind speed and water vapor mixing ratio, and wind speed and SST) to the surface heat fluxes. Gustiness was shown to be a major contribution to the simulated surface heat fluxes, especially when convection is active. In a multiday average, the contributions from the other effects (currents and wind speed-air temperature, wind speed-water vapor mixing ratio, and wind speed-SST correlations) are small; however, they cannot be neglected under certain circumstances.

Planktonic foraminifera in the southwest Pacific Ocean suggest the sea surface temperature was warmer during the Pleistocene than the Holocene. Change was relatively rapid, suggesting global-scale mechanisms.

Research indicates that metabolic regulation in the mollusk Cephalopoda is influenced by either food deprivation or handling stress. Habitat depth was found to affect anaerobic metabolic potential, decreasing with greater depth, while oxygen concentration affected oxygen consumption.

Incipient speciation and restricted gene flow have been studied in disjunct Sea of Cortez and Pacific Ocean populations of a reef fish species, opaleye, or Girella nigricans. Individual fish were in three clades, one in the Sea of Cortez, a Pacific one south of Punta Eugenia, and a Pacific one north of Punta Eugenia.

Genetic differences between crown-of-thorns starfish, Acanthaster planci, populations have been studied in the Pacific and Indian Oceans. Allozyme data are reported and compared with published Western Australia, Great Barrier Reef and Coral Sea data from 39 populations to give a complete description of the genetic structure of A. planci to compare with those from Linckia laevigata and to test the color morphs of A. planci to see whether they are genetically different.

We describe a model for episodic, open-ocean triple-junction migration based on observations of actual triple-junction evolutions. Migration progresses by repeated episodes of rift propagation, microplate formation, and microplate accretion to an adjacent, larger plate. These episodes may be highly variable in space and time depending on triple-junction geometry, velocity triangle, and other factors affecting local thermal and rheological conditions. Resulting tectonic features may include an abandoned transform fault, straight and potentially curving pseudofaults, sheared and potentially rotated abyssal-hill fabric, and a paleomicroplate with no associated failed rift. This model, developed mainly from the evolution of the Pacific-Antarctic-Nazca triple junction, may be relevant for other types of triple junctions such as the Bouvet and Azores triple junctions and ridge-ridge-ridge triple junctions in the Indian and Pacific Oceans. Episodic migration is found to occur even when the triple junction is kinematically stable. This model highlights the difference between predicted kinematic stability of triple junctions and observations of their true tectonic history.

Hurricanes result in considerable damage in the United States. Previous work has shown that Atlantic hurricane landfalls in the United States have a strong relationship with the El Nino-Southern Oscillation phenomena. This paper compares the historical record of La Nina and El Nino events defined by eastern Pacific sea surface temperature with a dataset of hurricane losses normalized to 1997 values. A significant relationship is found between the ENSO cycle and U.S. hurricane losses, with La Nina years exhibiting much more damage. Used appropriately, this relationship is of potential value to decision makers who are able to manage risk based on probabilistic information.

Black tiger prawn, Penaeus monodon, population structure is discussed based on study of western Pacific and western Indian Ocean populations. F-statistics and molecular phylogeny of alleles indicated very strong differentiation between populations of the two areas. It appears that there has been a biogeographic break between the Indo-West Pacific and the Indo-Australian Archipelago.

A new study examines the wing morphology of nine species of seabird in the tropical Pacific to investigate the theory that wing morphology reflects ecological differences in searching for and catching prey. It is shown that foraging differences among species correlated with predicted differences in wing morphology.

Research on two clades of Scylla serrata indicates a vicariant separation of the species may have occurred prior to S. serrata's radiation throughout the Indo-West Pacific Ocean region, which supports the recent colonization theory, recently defined as 1 mil years before the present.

A study was conducted on the guyots in the north Pacific Ocean which was made of drowned Cretaceous shallow-water carbonates. Strontium- and carbon-isotope stratigraphy was used in examining the limestones. Results showed that dating of the guyots indicate many events in the development of these carbonate platforms. The study also established that shallow-water systems submerged sequentially in a manner in which plate-tectonic movement shifted into low latitudes south of the Equator.

An investigation of the iron (Fe) perturbations needed to stimulate diatom production requires an assessment of the lowest Fe concentration whereby uptake still allows maximum cellular growth rates and of what Fe flux to surface waters is then required to sustain high diatom productivity once the concentration threshold is exceeded. Research in this area has concluded that climate forcing has definitely had an impact on productivity in the eastern equatorial Pacific. Furthermore, equatorial sediment records give an insight into these impacts. However, some element of this cycling may have been fuelled by localized tectonic processes in the Papua New Guinea island-arc area.

We consider two hypotheses for the origin of a linear trough extending [approximately] 800 km eastward from the intersection of the Louisville seamount chain with the Tonga-Kermadec trench. An extinct spreading center origin is suggested by the trough's eastward termination at a depth discontinuity that resembles a fracture zone. The morphology of the trough, however, is inconsistent with the morphology of other extinct spreading centers, and these two features do not appear to be connected to a larger paleo-plate boundary on their eastern end. We consider an alternative hypothesis in which the trough may be a recent rift in the Pacific plate. Coupling between a large subducting seamount and the overriding Australian plate may serve as a mechanism to focus stresses and nucleate a rift in the subducting Pacific plate. In this model, the seamount would act as a rigid indenter producing tangential extension in the subducting plate about the region where it is coupled to the overriding plate. Impeded subduction is suggested by a prominent seismicity gap around the subducting seamount. The graben morphology of the trough is also consistent with an extensional origin. If hotspot volcanism can produce obstructions and local weaknesses conducive to plate coupling, stress localization, and nucleation of fractures, it may provide a mechanism for subduction-induced plate reorganizations.

Line transect sampling assumes that animal detectability decreases as the distance from the transect increases but adjustment for environmental variables can affect the analysis. An analysis strategy is illustrated and discussed that takes account of variables and which uses ordinary least squares regression analysis and a standard estimator of effective area. The approach is applied to a survey of cheloniid sea turtles in the eastern Pacific Ocean.