Investigating marine bio-calcification mechanisms in a changing ocean with in vivo and high-resolution ex vivo Raman spectroscopy.

Ocean acidification poses a serious threat to marine calcifying organisms, yet experimental and field studies have found highly diverse responses among species and environments. Our understanding of the underlying drivers of differential responses to ocean acidification is currently limited by difficulties in directly observing and quantifying the mechanisms of bio-calcification. Here, we present Raman spectroscopy techniques for characterizing the skeletal mineralogy and calcifying fluid chemistry of marine calcifying organisms such as corals, coralline algae, foraminifera, and fish (carbonate otoliths). First, our in vivo Raman technique is the ideal tool for investigating non-classical mineralization pathways. This includes calcification by amorphous particle attachment, which has recently been controversially suggested as a mechanism by which corals resist the negative effects of ocean acidification. Second, high-resolution ex vivo Raman mapping reveals complex banding structures in the mineralogy of marine calcifiers, and provides a tool to quantify calcification responses to environmental variability on various timescales from days to years. We describe the new insights into marine bio-calcification that our techniques have already uncovered, and we consider the wide range of questions regarding calcifier responses to global change that can now be proposed and addressed with these new Raman spectroscopy tools.

pH homeostasis during coral calcification in a free ocean CO2 enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef.

Geochemical analyses (δ(11)B and Sr/Ca) are reported for the coral Porites cylindrica grown within a free ocean carbon enrichment (FOCE) experiment, conducted on the Heron Island reef flat (Great Barrier Reef) for a 6-mo period from June to early December 2010. The FOCE experiment was designed to simulate the effects of CO2-driven acidification predicted to occur by the end of this century (scenario RCP4.5) while simultaneously maintaining the exposure of corals to natural variations in their environment under in situ conditions. Analyses of skeletal growth (measured from extension rates and skeletal density) showed no systematic differences between low-pH FOCE treatments (ΔpH = ∼-0.05 to -0.25 units below ambient) and present day controls (ΔpH = 0) for calcification rates or the pH of the calcifying fluid (pHcf); the latter was derived from boron isotopic compositions (δ(11)B) of the coral skeleton. Furthermore, individual nubbins exhibited near constant δ(11)B compositions along their primary apical growth axes (±0.02 pHcf units) regardless of the season or treatment. Thus, under the highly dynamic conditions of the Heron Island reef flat, P. cylindrica up-regulated the pH of its calcifying fluid (pHcf ∼8.4-8.6), with each nubbin having near-constant pHcf values independent of the large natural seasonal fluctuations of the reef flat waters (pH ∼7.7 to ∼8.3) or the superimposed FOCE treatments. This newly discovered phenomenon of pH homeostasis during calcification indicates that coral living in highly dynamic environments exert strong physiological controls on the carbonate chemistry of their calcifying fluid, implying a high degree of resilience to ocean acidification within the investigated ranges.

Rapid, high-precision measurements of boron isotopic compositions in marine carbonates.

RATIONALE: The isotopic composition and elemental abundance of boron (B) in marine carbonates provide a powerful tool for tracking changes in seawater pH and carbonate chemistry. Progress in this field has, however, been hampered by the volatile nature of B, its persistent memory, and other uncertainties associated with conventional chemical extraction and mass spectrometric measurements. Here we show that for marine carbonates, these limitations can be overcome by using a simplified, low-blank, chemical extraction technique combined with robust multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) methods. METHODS: Samples are dissolved in dilute HNO3 and loaded first onto on a cation-exchange column with the major cations (Ca, Mg, Sr, Na) being quantitatively retained while the B fraction is carried in the eluent. The eluent is then passed directly through an anion column ensuring that any residual anions, such as SO4(2-), are removed. Isotopic measurements of (11)B/(10)B ratios are undertaken by matching both the B concentration and the isotopic compositions of the samples with the bracketing standard, thereby minimising corrections for cross-contamination. RESULTS: The veracity of the MC-ICPMS procedure is demonstrated using a gravimetrically prepared laboratory standard, UWA24.7, relative to the international reference standard NIST SRM 951 (δ(11)B = 0‰). This gives values consistent with gravimetry (δ(11)B = 24.7 ± 0.3‰ 2sd) for solutions ranging in concentration from 50 to 500 ppb, equivalent to ~2-10 mg size coral samples. The overall integrity of the method for carbonate analysis is demonstrated by measurements of the international carbonate standard JCp-1 (δ(11)B = 24.3 ± 0.34‰ 2sd). CONCLUSIONS: A streamlined, integrated approach is described here that enables rapid, accurate, high-precision measurements of boron isotopic compositions and elemental abundances in commonly analysed biogenic carbonates, such as corals, bivalves, and large benthic forams. The overall simplicity of this robust approach should greatly facilitate the wider application of boron isotope geochemistry, especially to marine carbonates.

Whale fall chemosymbiotic communities in a southwest Australian submarine canyon fill a distributional gap.

A whale fall community of chemosymbiotic invertebrates living on cetacean bones has been identified off southwestern Australia during a Remotely Operated Vehicle (ROV) survey at bathyal depths within the Bremer Marine Park, which is part of important marine mammal areas (IMMA) of the Albany Canyon Region. Cetacean bones on the seafloor of the Hood Canyon, consisted of isolated skulls of three species of beaked whales (family Ziphiidae): Mesoplodon cf. layardii, M. grayi, and M. hectori, a few vertebrae, and lower jaws. One of the beaked whale skulls (Mesoplodon cf. layardii) was sampled and found to be intensely colonised by hundreds of specimens of a bathymodilinae mussel ("Adipicola" s.l.). Live polychaetes (Phyllochaetopterus?), skeneimorph gastropods, and amphipods (Seba, Leptamphopus) colonised the skull bone, which represent a later stage (sulfophilic) of carcass decomposition. The reducing sediment below the skull was inhabited by lucinid (Lucinoma) and vesicomyid (Calyptogena) chemosymbiotic bivalves. Additionally, the sediment thanatocoenosis comprised shells of various other chemosymbiotic bivalves, such as Acharax, thyasirids, lucinids, vesicomyids, and limpets, representing the complex ecological turnover phases through time in this whale fall chemosynthetic habitat. With one exception, all bones recovered were colonized by bathymodiolin mussels. This is the first documented case of a chemosynthetic community and associated chemosymbiotic fauna relating to beaked whales, and the first fully documented record of a whale fall community within the Australian Southern Ocean region.

First assessment of anthropogenic impacts in submarine canyon systems off southwestern Australia.

We assessed the anthropogenic impacts on southwestern Australian submarine canyons by quantifying macro-litter discovered during Remotely Operated Vehicle surveys. The study area encompasses the Bremer canyon systems and Perth Canyon. The categories of macro-litter identified by our study are plastic, metal, aluminium, glass, fabric, mixed, derelict fishing gear, and unclassified. The anthropogenic impacts in the canyons explored is minimal, especially in the Bremer canyon systems, whereas Perth Canyon has comparatively more macro-litter, presumably due to intense maritime traffic and nearby urban development. On a global scale, however, the environmental status of southwestern Australian canyons is relatively pristine. This analysis provides a baseline for the monitoring and enduring stewardship of these habitats where lush and diverse biota, including deep-sea corals, thrive.

Coral calcification in a changing World and the interactive dynamics of pH and DIC upregulation.

Coral calcification is dependent on the mutualistic partnership between endosymbiotic zooxanthellae and the coral host. Here, using newly developed geochemical proxies (δ11B and B/Ca), we show that Porites corals from natural reef environments exhibit a close (r2 ∼0.9) antithetic relationship between dissolved inorganic carbon (DIC) and pH of the corals' calcifying fluid (cf). The highest DICcf (∼ × 3.2 seawater) is found during summer, consistent with thermal/light enhancement of metabolically (zooxanthellae) derived carbon, while the highest pHcf (∼8.5) occurs in winter during periods of low DICcf (∼ × 2 seawater). These opposing changes in DICcf and pHcf are shown to maintain oversaturated but stable levels of carbonate saturation (Ωcf ∼ × 5 seawater), the key parameter controlling coral calcification. These findings are in marked contrast to artificial experiments and show that pHcf upregulation occurs largely independent of changes in seawater carbonate chemistry, and hence ocean acidification, but is highly vulnerable to thermally induced stress from global warming.

Comparison of dermal absorption of zinc from different sunscreen formulations and differing UV exposure based on stable isotope tracing.

In a pilot study to determine if zinc (Zn) from zinc oxide nanoparticles in sunscreen can penetrate human skin in vivo, nanoparticles (~30nm) of a stable isotope (52% (68)Zn enrichment) were incorporated into an essentially phytochemical-based formulation and applied to the backs of 3 human subjects twice daily for 5 days during the Southern Hemisphere winter. Blood and urine were collected prior to application and at regular intervals and up to 50 days. As observed in a larger outdoor trial following this pilot study but with a different formulation and with UV exposure: values of (68)Zn in blood continued to increase beyond the 5 day application phase with the highest measurement at 14 days after the first application; variable amounts of the (68)Zn tracer were observed in urine; and the amounts of extra Zn added to blood were small and indicate very low levels of absorption (minimal estimate <0.01% of the applied dose) through the skin. Reasons for differences in absorption detected in the stable isotope trials and previous investigations include: the sensitivity of the stable isotope method; the duration of the investigations; the number of applications of sunscreen formulation; in vitro methods with excised skin; lack of measurement of blood and urine; no skin flexing; and lack of UV exposure.

Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin.

Metal oxide nanoparticles are commonly used in personal-care formulations as protective agents against exposure to ultraviolet radiation. Although previous research has concluded that nanoparticles do not penetrate healthy skin, it remains contentious whether this conclusion holds under normal conditions of sunscreen use. Humans (n = 20) were exposed to sunscreens containing zinc oxide (ZnO) particles to determine if Zn from the particles was absorbed through skin over five consecutive days under outdoor conditions. Two sunscreens were tested-"nano sunscreen" containing 19-nm nanoparticles and "bulk sunscreen" containing > 100-nm particles. Venous blood and urine samples were collected 8 days before exposure, twice daily during the trial, and 6 days post-exposure. As the first application in nanotechnology studies, stable isotope tracing was used where the ZnO, enriched to > 99% with the stable isotope (68)Zn, allowed dermally absorbed zinc to be distinguished from naturally occurring zinc. The overwhelming majority of applied (68)Zn was not absorbed, although blood and urine samples from all subjects exhibited small increases in levels of tracer (68)Zn. The amount of tracer detected in blood after the 5-day application period was ∼1/1000 th that of total Zn in the blood compartment. Tracer levels in blood continued to increase beyond the 5-day application phase in contrast to those in urine. Levels of (68)Zn in blood and urine from females receiving the nano sunscreen appeared to be higher than males receiving the same treatment and higher than all subjects receiving the bulk sunscreen. It is not known whether (68)Zn has been absorbed as ZnO particles or soluble Zn or both.

Did cooling oceans trigger Ordovician biodiversification? Evidence from conodont thermometry.

The Ordovician Period, long considered a supergreenhouse state, saw one of the greatest radiations of life in Earth's history. Previous temperature estimates of up to approximately 70 degrees C have spawned controversial speculation that the oxygen isotopic composition of seawater must have evolved over geological time. We present a very different global climate record determined by ion microprobe oxygen isotope analyses of Early Ordovician-Silurian conodonts. This record shows a steady cooling trend through the Early Ordovician reaching modern equatorial temperatures that were sustained throughout the Middle and Late Ordovician. This favorable climate regime implies not only that the oxygen isotopic composition of Ordovician seawater was similar to that of today, but also that climate played an overarching role in promoting the unprecedented increases in biodiversity that characterized this period.