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Zinc (Zn) is an essential micronutrient for most eukaryotic phytoplankton. Zn uptake by phytoplankton within the euphotic zone results in nutrient-like dissolved Zn (dZn) profiles with a large dynamic range. The combination of key biochemical uses for Zn and large vertical gradients in dZn implies the potential for rapid rates of Zn removal from the surface ocean. However, due to the ease of contamination at sea, direct measurements of dZn uptake within natural environments have not been previously made. To investigate the demand for dZn and for dissolved cadmium (dCd; a closely related nutrient-like element) within Southern Ocean phytoplankton communities, we conducted 67Zn and 110Cd tracer uptake experiments within the Amundsen Sea, Ross Sea, and Terra Nova Bay of the Southern Ocean. We observed a high magnitude of Zn uptake (ρ Zn > 100 pmol dZn L−1 d−1) into the particulate phase that was consistent with ambient depleted dZn surface concentrations. High biomass and low partial pressure of carbon dioxide in seawater (seawater pCO2) appeared to contribute to ρ Zn, which also led to increases in ρ Cd likely through the upregulation of shared transport systems. These high ρ Zn measurements further imply that only short timescales are needed to deplete the large winter dZn inventory down to the observed surface levels in this important carbon-capturing region. Overall, the high magnitude of Zn uptake into the particulate fraction suggests that even in the Zn-rich waters of the Southern Ocean, high Zn uptake rates can lead to Zn depletion and potential Zn scarcity. [ABSTRACT FROM AUTHOR]

We report measurements of near monthly Δ14C and δ18O during selected decades from an east equatorial Pacific coral that grew during the past four centuries. We find that El Niño events occurred regularly during the late 1700s. During the early 1800s, El Niño events occurred less often, and La Niña conditions prevailed, which were accompanied by unprecedented, low cool season Δ14C values and high cool season δ18O values. These results indicate that shallow overturning water (e.g., Central Mode Water) from the North Pacific was likely an important source of water to the Galapagos area during the early 1800s.

Species that are strong interactors play disproportionately important roles in the dynamics of natural ecosystems. It has been proposed that their presence is necessary for positively shaping the structure and functioning of ecosystems. We evaluated this hypothesis using the case of the world's largest parrotfish (Bolbometopon muricatum), a globally imperiled species. We used direct observation, animal tracking, and computer simulations to examine the diverse routes through which B. muricatum affects the diversity, dispersal, relative abundance, and survival of the corals that comprise the foundation of reef ecosystems. Our results suggest that this species can influence reef building corals in both positive and negative ways. Field observation and simulation outputs indicated that B. muricatum reduced the abundance of macroalgae that can outcompete corals, but they also feed directly on corals, decreasing coral abundance, diversity, and colony size. B. muricatum appeared to facilitate coral advancement by mechanically dispersing coral fragments and opening up bare space for coral settlement, but they also damaged adult corals and remobilized a large volume of potentially stressful carbonate sediment. The impacts this species has on reefs appears to be regulated in part by its abundance-the effects of B. muricatum were more intense in simulation scenarios populated with high densities of these fish. Observations conducted in regions with high and low predator (e.g., sharks) abundance generated results that are consistent with the hypothesis that these predators of B. muricatum may play a role in governing their abundance; thus, predation may modulate the intensity of the effects they have on reef dynamics. Overall our results illustrate that functionally unique and threatened species may not have universally positive impacts on ecosystems and that it may be necessary for environmental managers to consider the diverse effects of such species and the forces that mediate the strength of their influence.

AbstractDuring the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin with periodic ice advances beyond Last Glacial Maximum position. A change in sand provenance is indicative of a more stable Mertz Glacier system during the Late Pleistocene. East Antarctic Ice Sheet (EAIS) dynamics were evaluated through the analysis of marine diamictons from Integrated Ocean Drilling Program (IODP) site U1358 on the Adélie Land continental shelf. The warmer than present conditions of the early Pliocene coupled with the site's proximity to the landward sloping Wilkes Subglacial Basin provided the rationale for the investigations at this site. Based on visual core descriptions, particle size distributions, and major and trace element ratios, we interpret the origin of lower Pliocene strata by intermittent glaciomarine sedimentation with open-marine conditions and extensive glacial advances to the outer shelf. Heavy mineral analyses show that sand-sized detritus in the lower Pliocene strata was sourced from local intermediate to high-grade metamorphic rocks near Mertz Glacier. In contrast, Pleistocene diamictons exhibit a larger contribution from a prehnite-pumpellyite greenschist facies suggesting supply via iceberg rafting from northern Victoria Land. From this sedimentological evidence, we postulate a shift from a dynamic EAIS margin in the early Pliocene to possible stabilization in the Pleistocene.

Stable isotopic and trace element records from corals collected within the West Pacific Warm Pool (WPWP) are well suited to examine interannual to decadal climate variability associated with the El Niño-Southern Oscillation (ENSO) phenomenon. The most commonly used climate recorder in corals is δ18O (δ18OCRL), a parameter subject to multiple regional and local environmental influences. Location-specific calibration of δ18OCRL is a necessary first step for developing long-term paleoceanographic reconstructions. Here we present four new coral δ18O stratigraphies from the Republic of Palau (7.5°N 134.5°E), and compare our records with instrumental measurements for the period 1950–2008. We also compare our results with a previously published coral record from Palau. We employ a new sea surface salinity (SSS) product and validate its utility for coral-based paleoclimate calibrations. We not only examine differences among the records but also identify strong and regionally coherent environmental signals. We find that SSS variability is the dominant influence on δ18OCRL in Palau, while sea surface temperature (SST) is of secondary importance. Our results show that time-averaging multiple δ18OCRL records into a single composite series produce greater correlations with instrumental data and indices than individual stratigraphies alone. Our results are consistent with observations of a strengthening of the hydrological cycle in the WPWP region over the past 50 years, though the magnitudes of long term linear trends differ among the different Palau δ18OCRL records. Interannual and interdecadal variabilities between the Palau δ18OCRL records are more consistent than the long term linear trends. Monthly Palauan δ18OCRL anomalies capture strong El Niño events with high fidelity over the calibration period. This study provides constraints for future paleoenvironmental investigations in Palau using longer coral records.

Remote areas harbor some of the world's most undisturbed ecosystems. Major conservation gains can be made by effectively protecting nature in these remote zones. Conducting conservation work in remote settings presents both unique challenges and promising opportunities. We discuss how five commonly used approaches for conservation (buy and protect conservation; conservation motivated by the intrinsic values of nature; ecosystem service based conservation; ecotourism driven conservation; and conservation enabled by community planning) can be optimally applied to protect ecosystems in these special settings. In this discussion we draw examples from two model remote sites: Palmyra and Tabuaeran Atolls. Spatial analyses conducted using population density as a proxy for remoteness indicate that many existing recognized protected areas already include remote regions, but that the vast majority of the overall remote zones on the planet are not yet formally protected. Initiating discussions that directly consider both the roadblocks and opportunities for conservation in remote areas will help increase our odds of successfully protecting biodiversity in these unique and strategically important contexts. © 2013 Elsevier Ltd.

We analyzed radiocarbon in annual coral bands from the Galápagos Islands in the tropical east Pacific to understand natural variability of past ocean circulation associated with climate change. Variability was observed on El Niño timescales (3–7 years) as well as at decadal and multi-decadal periods. Low radiocarbon levels persisted for ten years during the early 1600s and for sixteen years during the early 1800s, both coincident with periods of high volcanic aerosol loading in the atmosphere from massive eruptions. Intensification of tropical circulation at this time may be linked to climatically-controlled changes in the structure of the tropical thermocline that is responsible for delivering cool, upwelled waters to the tropical east Pacific.