Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological ...pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth's climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES‐era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth's climate history.
Key Points
Distributions, drivers, and depositional archives described for iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver
Cadmium, barium, nickel, and chromium isotopes offer the most promise as paleoproductivity tracers, but key uncertainties remain
Future priorities include quantification of “missing” flux terms, constraining circulation influences, and identifying sedimentary archives
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Annual density banding provided growth characteristics for 245 similar-sized, massive colonies of
Porites from similar locations on 29 reefs from across the length and breadth of the Great Barrier ...Reef (GBR), Australia. Values obtained were density, extension rate, and calcification rate. Tissue thickness, the depth to which skeletons were occupied by tissue at the time of collection, was also measured. Extension rate, calcification rate, and tissue thickness were significantly greater at the top of colonies than at the sides. Extension rate and calcification rate decreased from north to south along the GBR (latitudinal range of ∼9°) and were significantly and directly related to annual average sea surface temperature (SST; range ∼25–27°C). For each 1°C rise in SST, average annual calcification increased by 0.39 g cm
−2 year
−1 and average annual extension increased by 3.1 mm year
−1 (c.f. average values of 1.63 g cm
−2 year
−1 and 12.9 mm year
−1, respectively). Density was inversely correlated with extension rate and increased with distance offshore. Data for massive
Porites colonies from the GBR were extended though 20° of latitude and an average annual SST range of 23–29°C using published data for the Hawaiian Archipelago (Grigg, R.W., 1981. Coral reef development at high latitudes in Hawaii. Proc. 4th Int. Coral Reef Symp., Manila, Vol. 1, pp. 687–693; Grigg, R.W., 1997. Paleoceanography of coral reefs in the Hawaiian-Emperor Chain — revisited. Coral Reefs 16, S33–S38) and Phuket, Thailand (Scoffin. T.P., Tudhope. A.W., Brown. B.E., Chansang. H., Cheeney. R.F., 1992. Patterns and possible environmental controls of skeletogenesis of
Porites lutea, South Thailand. Coral Reefs 11, 1–11). The response of calcification rate to temperature remained linear. Variation in annual average SST accounted for 84% of the variance. For each 1°C rise in SST, average annual calcification increased by 0.33 g cm
−2 year
−1 and average annual extension increased by 3.1 mm year
−1 (c.f. average values of 1.50 g cm
−2 year
−1 and 11.6 mm year
−1, respectively). The sensitivity of calcification rate in
Porites to SST, combined with observed 20th Century increases in SSTs, suggests that calcification rates may have already significantly increased along the GBR in response to global climate change.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after ...the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder': the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.
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We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy ...community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and
90
%
credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5–
20
deg
2
requires at least three detectors of sensitivity within a factor of
∼
2
of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The occurrence and intensity of luminescent lines was assessed by eye in slices from 232 similar-sized colonies of massive Porites from 30 reefs on the Great Barrier Reef (GBR), Australia. The reefs ...varied in location from coastal to 176 km from the mainland. Luminescent lines in corals of the GBR record periods when corals are exposed to river plumes and other mainland runoff. Reefs could be divided into three groups: those that never recorded runoff, those that recorded runoff but not every year, and those that recorded runoff every year. The average intensity of the luminescent lines was significantly inversely related to the percentage distance of a reef across the shelf and to the average water depth between a reef and the mainland. Annual variations in luminescence intensity were also significantly correlated with instrumental measurements of annual river flow and modelled salinities. These results suggest that luminescent lines in massive corals are a highly robust proxy record of mainland influence on reefs along the length of the GBR.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Annual variations in skeletal density were measured by gamma densitometry in 35 cores removed from large
Porites colonies growing at sites throughout the Great Barrier Reef (GBR). Density variations ...along each core provided data for average annual density and annual extension. These were used to estimate average annual calcification. Records ranged from 49 to 507 years in length. The period common to all colonies was 1934–1982. Annual growth data were averaged over periods of at least 5 years to avoid problems associated with dating of records and with measurement techniques. This also made some allowance for distortion of environmental information during coral growth and for intrusion into the environmental signal of information associated with skeletal architecture. The period common to the 10 longest cores was 1746–1982. Instrumental records of sea surface temperature (SST) are available for the GBR back to 1906. Annual calcification, averaged across these 10 cores, was significantly related to SST. Thus, average annual calcification for these 10 colonies provides a proxy for SST variations on the GBR back to the 18th century. Interpretation of evidence of a recent decline in calcification of
Porites of the GBR is tempered by (1) evidence of similar declines and recoveries over the past several centuries and (2) evidence that coral calcification on the GBR has been above the long-term average for most of this century and the recent decline may be a return to more normal conditions.
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Orally active Hsp90 inhibitors are of interest as potential chemotherapeutic agents. Recently, fully synthetic 8-benzyladenines and 8-sulfanyladenines such as 4 were disclosed as Hsp90 inhibitors, ...but these compounds are not water soluble and consequently have unacceptably low oral bioavailabilities. We now report that water-solubility can be achieved by inserting an amino functionality in the N(9) side chain. This results in compounds that are potent, soluble in aqueous media, and orally bioavailable. In an HER-2 degradation assay, the highest potency was achieved with the neopentylamine 42 (HER-2 IC50 = 90 nM). In a murine tumor xenograft model (using the gastric cancer cell line N87), the H3PO4 salts of the amines 38, 39, and 42 induced tumor growth inhibition when administered orally at 200 mg/kg/day. The amines 38, 39, and 42 are the first Hsp90 inhibitors shown to inhibit tumor growth upon oral dosage.
Heat shock protein 90 (Hsp90) is a molecular chaperone protein implicated in stabilizing the conformation and maintaining the function of many cell-signaling proteins. Many oncogenic proteins are ...more dependent on Hsp90 in maintaining their conformation, stability, and maturation than their normal counterparts. Furthermore, recent data show that Hsp90 exists in an activated form in malignant cells but in a latent inactive form in normal tissues, suggesting that inhibitors selective for the activated form could provide a high therapeutic index. Hence, Hsp90 is emerging as an exciting new target for the treatment of cancer. We now report on a novel series of 2-amino-6-halopurine Hsp90 inhibitors exemplified by 2-amino-6-chloro-9-(4-iodo-3,5-dimethylpyridin-2-ylmethyl)purine (30). These highly potent inhibitors (IC50 of 30 = 0.009 μM in a HER-2 degradation assay) also display excellent antiproliferative activity against various tumor cell lines (IC50 of 30 = 0.03 μM in MCF7 cells). Moreover, this class of inhibitors shows higher affinity for the activated form of Hsp90 compared to our earlier 8-sulfanylpurine Hsp90 inhibitor series. When administered orally to mice, these compounds exhibited potent tumor growth inhibition (>80%) in an N87 xenograft model, similar to that observed with 17-allylamino-17-desmethoxygeldanamycin (17-AAG), which is a compound currently in phase I/II clinical trials.
The construction in 1988 of an open-cut gold mine and ore-processing facility at Misima Island, Papua New Guinea, resulted in disturbance of the adjacent fringing coral reef, mostly because of large ...increases in sedimentation. This provided an opportunity to examine whether growth characteristics of the major reef-building coral, Porites, changed in response to this sudden and sustained increase in sedimentation. Annual variation in skeletal density was measured in 93 colonies variously affected by sedimentation. The colonies provided data for average annual density, annual extension and annual calcification covering the periods 5 y before and 5 y after mining operations began. The average depth of skeleton occupied by issue (tissue layer thickness) was also measured for most colonies. There was high mortality of Porites in regions strongly affected by increased sedimentation. In colonies that survived, density, extension and calcification tended to be less (in some case significantly) in the period after mining operations began compared with pre-construction levels. However, these decreases were not linked with proximity to the mine site and probably reflect a regional-scale response of Porites growth to some other environmental change. This suggests that periods of high sedimentation may not be recorded by the growth characteristics of massive Porites. Average growth characteristics of surviving Porites from Misima Island were similar to those from inshore reefs of the northern Great Barrier Reef (GBR). Tissue layer thickness in Porites from the control areas at Misima Island were also similar to colonies from the northern inshore GBR reefs. However, tissue layer thickness significantly decreased with increased proximity to the mine site at Misima Island.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
10.
Measurement of luminescence in coral skeletons Barnes, D.J.; Taylor, R.B.; Lough, J.M.
Journal of experimental marine biology and ecology,
10/2003, Volume:
295, Issue:
1
Journal Article
Peer reviewed
Luminescent lines in skeletons of the massive coral
Porites record periods when seawater was significantly diluted by land runoff. Records developed from such lines would be useful in a wide range of ...areas, including climatology, oceanography, civil engineering, agriculture, water resources and reef management. To realise this enormous potential, we built an instrument for routine, reliable recovery of luminescence information from coral skeletons. Skeletal slices were laid on a table that moved in 0.25 mm steps. The coral skeleton was illuminated with ultra-violet light (UV) at 390 nm and luminescent emissions at 490 nm were recorded. Light at 490 nm was then shone on the same 2 mm diameter point on the skeleton and the reflection of 490 nm light was recorded. Luminescent emissions from a point were then standardised by the reflectivity of that same point.
Slices cut from three corals that grew at an inshore reef had many strong luminescent lines. Measurements of luminescence in these colonies were nearly identical, both for multiple tracks across one slice and for tracks across slices from the different corals. There was a clear link with discharge from a nearby river. Slices cut from two corals that grew at a reef 56 km offshore had occasional, weak luminescent lines that were also linked with river discharge. Tracks across these slices were similar but the weak luminescence due to river discharge was partially obscured by weak luminescence associated with the annual density banding pattern that characterises massive coral skeletons. The technique recovered excellent information about skeletal luminescence. However, there is a need to gain better understanding of the link between seawater dilution and luminescence and to develop procedures for data processing before the technique can be used to construct useful proxy environmental records.
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