Sr/Ca

Variations in ratios of strontium-to-calcium (Sr/Ca) for two Porites sp. coral specimens collected from Wai (PW) and Loa Ya (PLY) islands, part of Chang islands, Gulf of Thailand, were determined. Inductively coupled plasma optimal emission spectrometry (ICP-OES) was used to analyze this ratio, which demonstrates annual cycles and the data is assumed to reflect the sea surface temperature (SST). Comparing the ratios with SST data, following Sr/Ca–SST relationships were determined PW: Sr/Ca (mmol/mol) = 11.56–0.070×SST, PLY: Sr/Ca (mmol/mol) = 11.89–0.081×SST. Our correlations are different from those previously reported; a discrepancy that may involve differences in analytical methods employed and abnormally low sea surface salinity (SSS) (<30 psu) in the Gulf of Thailand.

The extent of incorporation of Mn 2 + into calcite is inversely related to the rate of precipitation in laboratory experiments at Earth's surface, aqueous conditions. Values of k Mn, the partition coefficient of Mn 2+ into calcite, decreased from 18 to ~ 1 as the rate of precipitation, Rppt, was increased over almost four orders of magnitude. The correlation coefficient between the log of the precipitation rate and the log of the partition coefficient is-0.88, which is statistically significant at the 99.9% confidence level. The least squares regression takes the form log k Mn =-0.284 log Rppt + 0.976. These findings substantiate the rate dependence reported by Lorens and extend the range of the value of k Mn well below the minimum of 5.4 previously established by Michard. ESR (electron spin resonance) analysis of the precipitates provides direct evidence that Mn ~ substituted for Ca 2 ÷ in trigonal lattice sites of our synthetic calcites. Thus Mn 2 ÷ was incorporated in these calcites by the formation of a dilute solid solution of MnCO3 in CaCO~. Such alternative mechanisms of coprecipitation as occlusion, surface adsorption, or trace phase formation played no detectable role in these experiments. The exact mechanism by which the rate of precipitation controls the value of the partition coefficient during the formation of a solid solution remains elusive.

Strontium, magnesium, oxygen, and carbon isotope profiles of the carbonate fraction of Hole 600C sediments support the lithologic and petrographic observations of extensive CaCO3 dissolution and recrystallization in the Pliocene basal section. Convective fluid flow through the sediments during the first 1 to 1.5 m.y. of the sedimentary history of these sediments may explain these observations.

Interstitial water studies from sites drilled during a transect of the Walvis Ridge indicate that concentration increases in calcium and decreases in magnesium toward and into the basement. These trends can be understood principally in terms of reactions taking place in Layer 2 of the oceanic crust. At Site 525, however, some removal of magnesium occurs within the sediment column. Concentration maxima of dissolved strontium clearly indicate that carbonate recrystallization occurs throughout the carbonate sediments, and studies of the Sr/Ca ratio in carbonates indicate that in chalks and limestones recrystallization is essentially complete. Predictions of dissolved strontium maxima generally fail; this can be understood as removal of strontium in basal sediments and/or basalts.

Interstitial waters were collected at only two sites during Leg 82, Sites 558 and 563. Only very small changes in dissolved calcium and magnesium occur, presumably resulting from reactions in the underlying basement basalts. Dissolved strontium profiles indicate maxima, which can be understood in terms of carbonate recrystallization processes. Data on Sr/Ca in carbonates cannot be used to estimate the extent of recrystallization that has occurred in these sediments.

Chemical markers in otoliths have been used to assess the stock structure of many marine fishes, but these natural markers have yet to be widely evaluated in the spines of sturgeon fishes in the Caspian Sea, which has six endangered sturgeon species. We used inductively coupled plasma mass spectrometry to quantify B,

Studies of interstitial water carried out during Deep Sea Drilling Project Leg 78A (Sites 541, 542, and 543) have revealed that alteration of volcanic material dispersed in the sediments is largely responsible for increased concentrations of dissolved calcium and decreased concentrations of dissolved magnesium and potassium. This conclusion is supported by studies of the 87 Sr/ 86 Sr ratio of dissolved strontium, as well as by studies of the oxygen isotopic composition of interstitial waters. At Site 543 a large part of the δ 18 θ decrease in the interstitial waters must result from diffusive exchange with underlying basement rocks. Data from studies of interstitial water do not indicate upward advection of fluids at Sites 541 and 542.

Interstitial water studies on sediments recovered during Leg 34 have revealed no significant changes in the chemical composition with depth, except for dissolved silica and manganese. Although the sediments are characterized by important contributions of active ridge-derived material, basaltic components seem negligible. Postdepositional chemical reactions (if any) must occur in such a fashion that no imprint on the chemical composition of the interstitial waters occurs, or at such slow rates that any such changes in composition are annihilated by diffusional exchange processes.

Interstitial waters from several sites drilled during Leg 58 have been analyzed for major constituents. Data for Sites 442, 443, and 444 in Shikoku Basin indicate that only small changes occur in the chemical composition. We did not note any influence on the interstitial water chemistry resulting from reactions taking place in the underlying basalts. Site 445 data indicate that reactions must occur in the sediment column, leading to decreases in dissolved magnesium and increases in dissolved calcium. In addition, a source of dissolved calcium appears in the underlying basalts. At Site 446, changes appear in dissolved-calcium and-magnesium concentrations, resulting mainly from alteration reactions in the basalts. Dissolved potassium has its main sink in deeper-lying sediments or basalts. Changes in dissolved strontium at Sites 445 and 446 can be explained in terms of carbonate recrystallization. At all sites, changes in dissolved manganese and lithium appear to be related to the presence of biogenic silica in the sediments.

Interstitial water samples from Sites 834 through 839, drilled during Ocean Drilling Program Leg 135 in the backarc Lau basin (Southwestern Pacific), have been analyzed for major elements, manganese, copper, strontium, barium, vanadium, and 87 Sr/ 6 Sr isotopic composition values. The concentration-depth profiles of the major chemical components show almost straight concentration gradients at all sites, and seem to reflect slight alteration of volcanic material. However, in the lower part of the sedimentary cover, where volcanogenic material is abundant and where diagenetic minerals occur, systematic decreases in calcium, strontium, manganese, copper, and vanadium concentrations are observed. A downwelling flow of bottom seawater, which affected the diagenetic chemical signature of the interstitial water, is probably responsible for the recorded chemical features. This hypothesis is supported by strontium isotope data obtained from interstitial water samples at Site 835. It is also in accordance with data from heat flow and physical properties.

Two zooxanthellate, scleractinian species present in the equatorial eastern Pacific, Psammocora stellata and Psammocora profundacella, were examined in terms of their reproductive biology and ecology at four study sites, non-upwelling (Caño Island, Costa Rica, and Uva Island, Panamá), upwelling (Gulf of Panamá, Panamá), and seasonally varying thermal environments (Galápagos Islands). Both species were gonochoric broadcast spawners lacking zooxanthellae in mature ova. Mature gametes and spawned gonads are present around full moon; however, no spawning was observed naturally or in outdoor aquaria. Mature gametes occurred in P. stellata at Caño Island for nearly 6 months, and year round at Uva Island, both non-upwelling sites. Reproductively active colonies occurred mostly in the warmer months in the Gulf of Panamá and Galápagos Islands. In the Galápagos Islands, where collecting effort was greatest for P. profundacella, mature gametes were also most prevalent during the warm season. Annual fecundity was high in both species, 1.3-1.8 9 10 4 ova cm-2 year-1 in P. stellata and 1.2-2.0 9 10 4 ova cm-2 year-1 in P. profundacella. Compared to other eastern Pacific corals, P. stellata was relatively resistant to ENSO-related bleaching and mortality, especially populations inhabiting deep (12-20 m) coral communities. Rapid recovery and persistence of Psammocora spp. can be attributed to several factors: (a) relative resistance to bleaching, (b) deep refuge populations, (c) broadcast spawning, (d) protracted seasonal reproduction, (e) high fecundity, and (f) asexual propagation.

laminite, tidal-flat unit locally interrupts the marine limestone sequence at the western (more offshore) end of the Grand Canyon. The 250-500 m Cambrian sequence appears to consist of more than 30 laterally persistent sedimentation cycles that are grouped into 5 grand cycles. The basal Tapeats Sandstone and the clastic and carbonate tidal flats are not cyclic.

downhole decrease in i8O, Mg2 + and K', an increase in Cat+ and a low *'Sris6Sr ratio of 0.7067 in the pore fluids of DSDP site 323 were caused principally by the alteration of volcanic material. These chemical and isotopic patterns were produced by the alteration, in order of decreasing importance of: a 60-m thick basal layer of volcanic ash; the underlying basalts; and igneous components in the 640-m thick upper sequence composed largely of terrigenous material. A significant portion of the alteration of the ash in the basal sequence must have occurred before the deposition of the upper sediments. perhaps under the influence of advecting solutions. The rest of the alteration occurred during the deposition of the thick upper sediments. Mass balance considerations and the low 6'*0 values of most of the alteration products suggest that much of the later alteration occurred progressively over the last 13 Myr. The principal alteration products were smectite, potassium feldspar, clinoptilolite and calcite

downhole decrease in i8O, Mg2 + and K', an increase in Cat+ and a low *'Sris6Sr ratio of 0.7067 in the pore fluids of DSDP site 323 were caused principally by the alteration of volcanic material. These chemical and isotopic patterns were produced by the alteration, in order of decreasing importance of: a 60-m thick basal layer of volcanic ash; the underlying basalts; and igneous components in the 640-m thick upper sequence composed largely of terrigenous material. A significant portion of the alteration of the ash in the basal sequence must have occurred before the deposition of the upper sediments. perhaps under the influence of advecting solutions. The rest of the alteration occurred during the deposition of the thick upper sediments. Mass balance considerations and the low 6'*0 values of most of the alteration products suggest that much of the later alteration occurred progressively over the last 13 Myr. The principal alteration products were smectite, potassium feldspar, clinoptilolite and calcite

Strontium concentrations and 87 Sr/ 86 Sr values were measured on pore-water and sedimentary carbonate samples from sediments recovered at Sites 1049-1053 on the Blake Spur during Ocean Drilling Program Leg 171B. These sites form a 40-km-long depth transect extending along the crest of the Blake Spur from near the upper edge of the Blake Escarpment (a steep cliff composed of Mesozoic carbonates) westward toward the interior of the Blake-Bahama Platform. Although these sites were selected for paleoceanographic purposes, they also form a hydrologic transect across the upper eastern flank of the Blake-Bahama Platform. Here, we use pore-water strontium concentrations and isotopes as a proxy to define patterns of fluid movement through the flanks of this platform. Pore-water strontium concentration increases with depth at all sites implying that strontium has been added during sediment burial and diagenesis. The isotopic values decrease from seawater-like values in the shallow samples (~0.70913) to values as low as 0.707342 in one of the deepest samples (~625 meters below seafloor). The change in porewater strontium isotopic values is independent of the strontium isotopic compositions predicted from the host sediment age and measured on bulk carbonate in some samples. In most cases the difference between predicted sediment strontium isotopic composition and measured value is less than ±2 σ about the mean of the measured strontium value. Both the increase in concentration and the decrease in the strontium isotope values with increasing depth indicate that strontium was expelled from older carbonates. The strontium concentration and iso

Velocity behaviour in chalks is determined by a combination of their depositional conditions and subsequent diagenesis. Based on rock physics data from three drill sites on the Ontong Java Plateau, a strategy for velocity modelling is proposed where geological information is imposed via pore structure models. The Reuss and time-average relations define upper and lower bounds of the velocity data and the self-consistent approximation was applied to find direct links between velocity and changes in microstructure. The latter approach provides an estimate of the dynamic changes of the pore structure as a result of diagenesis in chalks. Depositional pore-models of chalks were determined from environmental conditions and can be defined from textural information. Mechanical compaction and cementation decrease porosity as a function of depth, but may increase the velocity by different rates as the pore structure changes differently. Discrimination between sediment stiffness and pore structure stiffness enables us to justify low velocity for indurated sediments and high velocity for soft sediments. Our results indicate the relevance of the pore structure to velocity interpretation because some variations in velocity data may result from pore structure differences rather than changes in fluid or porosity.

Fossilized foraminiferal tests are widely used as proxies to constrain paleoenvironments, including past sea surface and bottom water temperatures and the chemical composition of ancient seawater. However, relatively little is known about the extent to which calcareous foraminiferal tests exchange with seawater prior to burial. In this study, we used a 45 Ca radiotracer approach to quantify the extent and rate of foraminiferal calcite-fluid exchange over a three-month period. Modern foraminiferal tests exhibited faster exchange with a 45 Ca-spiked solution (2.6•10 −4 to 2.0•10 −5 mol/m 2 /d) than fossil foraminiferal tests (7.6•10 −5 to 5.3•10 −6 mol/m 2 /d) from ODP Site 807. The impact of dissolved Si on the exchange rate of modern foraminifera was minimal (2.6•10 −4 to 9.2•10 −6 mol/m 2 /d). Unlike foraminiferal calcite, inorganic calcite exchanged at remarkably slow rates (6.6•10 −6 to 5.9•10 −7 mol/m 2 /d) suggesting that biogenic calcite is more reactive than inorganic calcite. Increased Ca 2+ , Mg 2+ , and Sr 2+ concentrations in fluids from parallel tracer-free reactors indicated preferential dissolution of tests, though there was no overt change in test morphology during experiments (as imaged by scanning electron microscopy and micro-CT scanning). Time-dependent box model simulations of 45 Ca, as well as aqueous elemental chemistry, support the hypothesis that calcite-fluid exchange occurred via dissolution-reprecipitation of foraminiferal tests that was induced by intra-test chemical heterogeneity. The short-term exchange reactions investigated in this study are comparable to the reactions that can occur in the seawater column and at the sediment-seawater interface. This work suggests that dissolution-reprecipitation in such settings has the potential to overprint the chemistry of foraminiferal tests without overt physical alteration, which can lead to a potential bias in paleoenvironmental reconstructions. Model-based estimates suggest a maximum of 2-3 • C alteration of Mg/Ca-based temperatures over experimental time scales. Model efforts also suggest that the diagenetic trajectories in Mg/Ca-δ 18 O space, for instance, are impacted by the partition coefficient of Mg in calcite (λ Mg) as well as by the mechanism of alteration. This is demonstrated for (i) the ratio of exchange to dissolution and (ii) the relative rate of high-Mg-calcite to low-Mg-calcite reaction. We have illustrated that the mechanism of alteration, in addition to waterrock ratios, determine diagenetic trajectories. Finally, surface reaction has implications for our ability to constrain fractionation factors in experimental and natural systems. The experimental observations suggest that exchange between tests and solution is nominal over ∼100 days. Experiments aimed at deducing fractionation factors rely on the equilibration of bulk solid and fluid, since these are the readily analyzed reservoirs. We quantify the fraction of carbonate (>5%) that must react so that surface reaction does not impact the interpretation of Ca isotopic fractionation factors, and discuss the implications for more "fluid-dominated" elements such as Mg and O.

The potential use of elemental fingerprinting of five hard parts (otolith, scale, dorsal spine, eye lens and vertebral bone) for stock discrimination of Rutilus kutum from the Caspian Sea was investigated, for the first time. The specimens were sampled from three sampling sites in the Southern Caspian Sea in March 2016. Twenty specimens (total length: 32.6-37.9 mm; age: 3-4 yrs) were collected from each site. Concentrations of elements

Two zooxanthellate, scleractinian species present in the equatorial eastern Pacific, Psammocora stellata and Psammocora profundacella, were examined in terms of their reproductive biology and ecology at four study sites, non-upwelling (Caño Island, Costa Rica, and Uva Island, Panamá), upwelling (Gulf of Panamá, Panamá), and seasonally varying thermal environments (Galápagos Islands). Both species were gonochoric broadcast spawners lacking zooxanthellae in mature ova. Mature gametes and spawned gonads are present around full moon; however, no spawning was observed naturally or in outdoor aquaria. Mature gametes occurred in P. stellata at Caño Island for nearly 6 months, and year round at Uva Island, both non-upwelling sites. Reproductively active colonies occurred mostly in the warmer months in the Gulf of Panamá and Galápagos Islands. In the Galápagos Islands, where collecting effort was greatest for P. profundacella, mature gametes were also most prevalent during the warm season. Annual fecundity was high in both species, 1.3-1.8 9 10 4 ova cm-2 year-1 in P. stellata and 1.2-2.0 9 10 4 ova cm-2 year-1 in P. profundacella. Compared to other eastern Pacific corals, P. stellata was relatively resistant to ENSO-related bleaching and mortality, especially populations inhabiting deep (12-20 m) coral communities. Rapid recovery and persistence of Psammocora spp. can be attributed to several factors: (a) relative resistance to bleaching, (b) deep refuge populations, (c) broadcast spawning, (d) protracted seasonal reproduction, (e) high fecundity, and (f) asexual propagation.

People around the world depend on the resources provided by the ocean to support life. But globalscale damage to the coral reefs, a large and integral part of the ocean environment that supports a variety of sea life, is a frightening scenario that may unfold in the coming years.

Since 1982, coral reefs worldwide have been subjected to an increased frequency of the phenomenon known as coral bleaching. Bleaching involves the dramatic loss of pigmented, single-celled endosymbiotic algae that live within the gastrodermal cells of a coral host that depends on this relationship for survival. Prior to the 1980s, and as early as the 1920s when coral reef research intensified, localized bleaching events were reported and attributed to factors such as extremely low tides, hurricane damage, torrential rainstorms, fresh water runoff near reefs, or toxic algal blooms [Glynn, 1993]. However, these early occur rences have recently been overshadowed by geographically larger and more frequent bleach ing events whose impact has expanded to regional and global proportions.

Interstitial water samples from Sites 834 through 839, drilled during Ocean Drilling Program Leg 135 in the backarc Lau basin (Southwestern Pacific), have been analyzed for major elements, manganese, copper, strontium, barium, vanadium, and 87Sr/86Sr isotopic composition values. The concentration-depth profiles of the major chemical components show almost straight concentration gradients at all sites, and seem to reflect slight alteration of volcanic material. However, in the lower part of the sedimentary cover, where volcanogenic material is abundant and where diagenetic minerals occur, systematic decreases in calcium, strontium, manganese, copper, and vanadium concentrations are observed. A downwelling flow of bottom seawater, which affected the diagenetic chemical signature of the interstitial water, is probably responsible for the recorded chemical features. This hypothesis is supported by strontium isotope data obtained from interstitial water samples at Site 835. It is also in...

Since 1982, coral reefs worldwide have been subjected to an increased frequency of the phenomenon known as coral bleaching. Bleaching involves the dramatic loss of pigmented, single-celled endosymbiotic algae that live within the gastrodermal cells of a coral host that depends on this relationship for survival. Prior to the 1980s, and as early as the 1920s when coral reef research intensified, localized bleaching events were reported and attributed to factors such as extremely low tides, hurricane damage, torrential rainstorms, fresh water runoff near reefs, or toxic algal blooms [Glynn, 1993]. However, these early occur rences have recently been overshadowed by geographically larger and more frequent bleach ing events whose impact has expanded to regional and global proportions.

Interstitial water samples from Sites 834 through 839, drilled during Ocean Drilling Program Leg 135 in the backarc Lau basin (Southwestern Pacific), have been analyzed for major elements, manganese, copper, strontium, barium, vanadium, and 87Sr/ 6Sr isotopic composition values. The concentration-depth profiles of the major chemical components show almost straight concentration gradients at all sites, and seem to reflect slight alteration of volcanic material. However, in the lower part of the sedimentary cover, where volcanogenic material is abundant and where diagenetic minerals occur, systematic decreases in calcium, strontium, manganese, copper, and vanadium concentrations are observed. A downwelling flow of bottom seawater, which affected the diagenetic chemical signature of the interstitial water, is probably responsible for the recorded chemical features. This hypothesis is supported by strontium isotope data obtained from interstitial water samples at Site 835. It is also in...

Sr/Ca ratios recorded in the aragonite skeleton of massive coral colonies are commonly used to reconstruct seasonal-to centennial-scale variability in sea surface temperature (SST). While the Sr/Ca paleothermometer is robust in individual colonies, Sr/Ca-SST relationships between colonies vary, leading to questions regarding the utility of the proxy. We present biweekly-resolution calibrations of Sr/Ca from five Porites spp. corals to satellite SST across 10°of latitude in the Red Sea to evaluate the Sr/Ca proxy across both spatial and temporal scales. SST is significantly correlated with coral Sr/Ca at each site, accounting for 69-84% of Sr/Ca variability (P ≪ 0.01). Intercolony variability in Sr/Ca-SST sensitivities reveals a latitudinal trend, where calibration slopes become shallower with increasing mean annual temperature. Mean annual temperature is strongly correlated with the biweekly-resolution calibration slopes across five Red Sea sites (r 2 = 0.88, P = 0.05), while also correlating significantly to Sr/Ca-SST slopes for 33 Porites corals from across the entire Indo-Pacific region (r 2 = 0.26, P < 0.01). Although interannual summer, winter, and mean annual calibrations for individual Red Sea colonies are inconsistently robust, combined multicoral calibrations are significant at summer (r 2 = 0.53, P ≪ 0.01), winter (r 2 = 0.62, P ≪ 0.01), and mean annual time scales (r 2 = 0.79, P ≪ 0.01). Our multicoral, multisite study indicates that the Sr/Ca paleothermometer is accurate across both temporal and spatial scales in the Red Sea and also potentially explains for the first time variability in Sr/Ca-SST calibration slopes across the Indo-Pacific region. Our study provides strong evidence supporting the robustness of the coral Sr/Ca proxy for examining seasonal to multicentury variability in global climate phenomena.

The 87Sr/SrSr ratios of formation waters from the chalk of the Ekofisk oilfield were measured using a new technique: extracting salt residues from the interstices of core samples. In the Danian Ekofisk 87 86 13 Formation, the chalk matrix itself has Sr/ Sr and ~ C values characteristic of Danian seawater, even 18 though 60 data indicate the~resence of varying quantities of diagenetic carbonate cement. In the Ekofisk Formation, porewater o'Sr/86Sr values are very constant (range: 0.70786-0.70810). The formation water probably contains locally derived Sr from carbonate, plus a small contribution from nonca 87 86 rbonate minerals with higher Sr/ Sr. In the under!ying Tor Formation, chalk samples containing a 87 8o mixture of primary chalk and later cement, have Sr/ Sr values that rise with depth to a maximum of 0.70865, much higher than contemporaneous seawater. Porewater 87Sr/86Sr values increase even more dramatically with depth to a maximum of 0.70988. Both cement and waters have been influenced by Sr with a high S7Sr/86Sr probably derived from underlying sedimentary rocks. Comparison with waters brought to the surface together with produced oil indicates that the depthwise increase in s7 Sr? ~6 Sr reflects an increase in salinity from-50,000 to-140,000 mg/l total solute content. This suggests that Zechstein evaporites may be the source of the radiogenic Sr in the Tor Formation. The difference in isotope composition between carbonates and waters in the Ekofisk and Tor Formations indicates that their hydrochemical systems have evolved differently during diagenesis. This is due to the barrier effect of the Ekofisk Tight Zone, a hardground at the base of the Ekofisk Formation which effectively splits the reservoir vertically into two. This study thus provides a new way of determining the positions of permeability barriers in oil reservoirs. Also demonstrated for the first time is the existence of vertical variations in salinity of water in oil. Such variations could have important implications for the calibration of resistivity logs and calculation of the amount of oil in place.

Two zooxanthellate, scleractinian species present in the equatorial eastern Pacific, Psammocora stellata and Psammocora profundacella, were examined in terms of their reproductive biology and ecology at four study sites, non-upwelling (Caño Island, Costa Rica, and Uva Island, Panamá), upwelling (Gulf of Panamá, Panamá), and seasonally varying thermal environments (Galápagos Islands). Both species were gonochoric broadcast spawners lacking zooxanthellae in mature ova. Mature gametes and spawned gonads are present around full moon; however, no spawning was observed naturally or in outdoor aquaria. Mature gametes occurred in P. stellata at Caño Island for nearly 6 months, and year round at Uva Island, both non-upwelling sites. Reproductively active colonies occurred mostly in the warmer months in the Gulf of Panamá and Galápagos Islands. In the Galápagos Islands, where collecting effort was greatest for P. profundacella, mature gametes were also most prevalent during the warm season. Annual fecundity was high in both species, 1.3-1.8 9 10 4 ova cm-2 year-1 in P. stellata and 1.2-2.0 9 10 4 ova cm-2 year-1 in P. profundacella. Compared to other eastern Pacific corals, P. stellata was relatively resistant to ENSO-related bleaching and mortality, especially populations inhabiting deep (12-20 m) coral communities. Rapid recovery and persistence of Psammocora spp. can be attributed to several factors: (a) relative resistance to bleaching, (b) deep refuge populations, (c) broadcast spawning, (d) protracted seasonal reproduction, (e) high fecundity, and (f) asexual propagation.

Geochemical proxy-based reconstructions widely utilize the trace elemental and isotopic compositions of marine biogenic carbonates to interpret past climatic and oceanographic conditions. However, such proxy-based reconstructions are often challenged by marine diagenesis as carbonates are highly susceptible to diagenetic alteration, especially to partial dissolution and calcite recrystallization. Thus, quantifying diagenetic effects is a prerequisite for the development of any carbonate-based geochemical proxy. Among the metal isotopes, Mg isotopic composition (δ 26 Mg) of foraminiferal carbonates is a promising proxy to reconstruct secular seawater δ 26 Mg variability, which is useful in understanding long-term changes in the Mg geochemical cycle. However, Mg in marine carbonates is particularly susceptible to diagenetic alterations due to its low abundance in carbonates compared to pore fluids. Hence, the development of δ 26 Mg of marine carbonates as a proxy demands a thorough understanding of the isotopic systematics of Mg in marine sedimentary systems, which to date has not been accomplished. The primary goal of this dissertation is to quantify the effect of diagenesis on metal isotopes, in particular, the δ 26 Mg of marine carbonates from various depositional settings. Multiple marine sites are investigated to evaluate the effect of advection, diffusion, and lithological variation within the sedimentary column on the extent of calcite diagenesis. The first two chapters are focused on comparing the extent of diagenetic alteration among various marine sites and quantifying the impact of such diagenetic reactions on carbonate-based proxies. In the first study, the effect of diagenetic recrystallization on bulk carbonate δ 26 Mg is quantified from an open marine site (ODP Site 1171, Hole A), which is influenced by upward advection. Trace elemental (e.g., Mg/Ca and Sr/Ca) and isotopic compositions (δ 26 Mg and 87 Sr/ 86 Sr) of pore fluids and bulk carbonates are analyzed from Hole 1171A using an ICP-AES and a Neptune Plus MC-ICP-MS, respectively. A systematic decrease in bulk carbonate δ 26 Mg (-4 to 0.40 •10-4 mol/m 2 /d). The increase in [Ca 2+ ], [Mg 2+ ], and [Sr 2+ ] in the fluid of a set of parallel non-tracer experiments indicates that dissolution-precipitation is the dominant mechanism of the atom exchange in foraminiferal calcite. Interestingly, in the presence of aqueous silica in some of the reactors the exchange rate of modern foraminifera decreases (3.70•10-4 to 0.13•10-4 mol/m 2 /d). This observation indicates that the presence of dissolved silica in the system can inhibit calcitefluid exchange, which enhances the preservation of foraminiferal tests and minimizes the extent of alteration of foraminiferal proxies. vi

Las temperaturas superficiales del océano se incrementan significativamente en la zona del Pacífico este durante los eventos El Niño-Oscilación del Sur (ENSO). Este incremento en las temperaturas afecta negativamente a dos comunidades coralinas de la parte sur del Golfo de California. Durante el evento ENSO de 1997-1998, las comunidades bentónicas sésiles estuvieron expuestas a anomalías térmicas de hasta 3.0 °C. El análisis de los cambios en la cobertura de coral vivo en el área durante 1996 (condición pre-ENSO), 1997, 1998 y 1999, indican que aproximadamente el 30% de los corales padeció blanqueamiento. Este evento de blanqueamiento de coral estuvo acompañado de severas mortalidades de hasta 60%. El blanqueamiento de coral fue más intenso en las regiones localizadas más al norte de la zona en estudio, que en las zonas al sur, las cuales comúnmente están expuestas a temperaturas superiores. Los corales localizados en las partes someras experimentaron una mayor incidencia de blanqueamiento que aquéllos localizados en aguas profundas. Los análisis fisiológicos indican que esta distribución vertical responde a diferencias en la temperatura y no a diferencias en la iluminación. Junto con el blanqueamiento y la mortalidad de coral, detectamos variaciones en las densidades poblacionales y en la distribución de tallas de algunos invertebrados asociados al coral. El análisis de las variaciones anuales en riqueza específica de las algas asociadas a los mantos de rodolitos, permiten trazar una línea de base para estudios futuros sobre los impactos del ENSO en estos ecosistemas.

In order to investigate the incorporation of Sr, Mg, and U into coral skeletons and its temperature dependency, we performed a culture experiment in which specimens of the branching coral (Porites cylindrica) were grown for 1 month at three seawater temperatures (22, 26, and 30°C). The results of this study showed that the linear extension rate of P. cylindrica has little effect on the skeletal Sr/Ca, Mg/Ca, and U/Ca ratios. The following temperature equations were derived: Sr/Ca (mmol/ mol) = 10.214(±0.229) À 0.0642(±0.00897) Â T (°C) (r 2 = 0.59, p < 0.05); Mg/Ca (mmol/mol) = 1.973(±0.302) + 0.1002 (±0.0118) Â T (°C) (r 2 = 0.67, p < 0.05); and U/Ca (lmol/mol) = 1.488(±0.0484) À 0.0212(±0.00189) Â T (°C) (r 2 = 0.78, p < 0.05). We calculated the distribution coefficient (D) of Sr, Mg, and U relative to seawater temperature and compared the results with previous data from massive Porites corals. The seawater temperature proxies based on D calibrations of P. cylindrica established in this study are generally similar to those for massive Porites corals, despite a difference in the slope of D U calibration. The calibration sensitivity of D Sr , D Mg , and D U to seawater temperature change during the experiment was 0.64%/°C, 1.93%/°C, and 1.97%/°C, respectively. These results suggest that the skeletal Sr/Ca ratio (and possibly the Mg/Ca and/or U/Ca ratio) of the branching coral P. cylindrica can be used as a potential paleothermometer.

Through the Deep Sea Drilling Project samples of interstitial solutions of deeply buried marine sediments throughout the World Ocean have been obtained and analyxed. The studies have shown that in all but the most slowly deposited sediments pore fluids exhibit changes in composition upon burial. These changes can be grouped into a few consistent patterns that facilitate identification of the diagenetic reactions oocurring in the sediments. Pelagic clays and slowly deposited (< 1 cm/l@ yr) biogenio sediments are the only types that exhibit little evidence of reaction in the pore waters. In most biogenic sediments ma water undergoes considerable alteration. In sediments deposited at rates up to a few cm/loB yr the changes chiefly involve gains of Gas+ and Srs+ and losses of Mg*+ which balance the Cae+ enrichment. The Ca-Mg substitution may often reach 30 mM/kg while Srs+ may be enriched E-fold over sea water. These changes reflect recrystallisation of biogenio oalaite and the substitution of Mg" for Cast during this reaction. The Ca-Mg. carbonate formed is most likely a dolomitic phase. A related but more complex pattern is found in carbonate sediments deposited at somewhat greater rates. Ca"-r-and S#+ enrichment is again characteristic, but Msp+ losses exceed Caw gains with the excess being balanoed by SO,s-losses The data indioate that the reactions are similar to those noted above, except that the Caa+ released is not kept in solution but is precipitated by the HCOs-produced in SO,ereduction. In both these types of pore waters Nat is usually conservative, but K+ depletions are frequent. In several partly consolidated sediment sections approaching igneous basement contact, very marked interstitial oalcium enrichment has been found (to 6.6 g/kg). These phenomena are marked by pronounced depletion in Na +, Si and CO,, and slight enhancement in Cl-. The changes are attributed to exchange of Na+ for Ca*+ in silicate minerals forming from submarine weathering of igneous rocks such ae basalts. Water is also consumed in these reactions, accounting for minor increases in total interstitial salinity. Terrigenous, organ&rich sediments deposited rapidly along continental margins also exhibit significant evidences of alteration. Microbial reactions involving organic matter lead to oomplete removal of SO,*-, strong HCO,enrichment, formation of NHa, and methane synthesis from H, and CO, once SO,* is eliminated. K+ and often Na+ (slightly) are depleted in the interstitial waters. Gas+ depletion may occur owing to precipitation of CaCO,. In most cases interstitial Cl-remains relatively constant, but increases are noted over evaporitic strata, and decreases in interstitial Cl-are observed in some sediments adjacent to continents. THE CO?\IPOSITION of interstitial solutions of sediments reflects reactions between solids of the sediment, as well as sedimentrsolute interactions. Since the ratio of dissolved component to solid component for most constituents of the sediments is very small, reactions undetectable in the solids often have a large and readily * Woods Hole Oceanographic Institution Contribution Number 3359. Publication

The 2015-2016 E1 Niño Southern Oscillation event was one of the extreme climate events which elevated the sea surface temperature (SST) of tropical oceans, which in turn increased the level of thermal stress on corals. Coral bleaching event is mainly caused due to high positive SST anomaly, i.e., when SST exceeds its normal summer maxima. Corals in the Gulf of Kachchh region of Gujarat earlier experienced coral bleaching events during 1988, 2010 and 2014. For this study, SST was derived from NOAA OISST data set which is available daily at 0.25° global grids from 1982 to present. The climatologically warmest month for the Gulf of Kachchh region is June when the maximum monthly mean temperature is 29.31°C, as observed from NOAA OISST. The present study focuses on monitoring daily SST anomalies during summer 2016 for the Gulf of Kachchh reefs and field observations on early responses of coral bleaching from Laku Point reef, a site known for high coral diversity. It was found that in su...

report, burial and growth rates of nodules from a single location are required. Nevertheless, the promising first results have a number of implications for theories of nodule formation: 1) The process that keeps nodules at the sea floor (that is, that determine B) is independent of nodule size for D > Do.

The Mg and Sr isotopic compositions (δ 26 Mg and 87 Sr/ 86 Sr) of pore fluids and bulk carbonates from Ocean Drilling Project Site 1171 (South Tasman Rise; 2148.2 m water depth) are reported, in order to evaluate the potential of diagenesis to alter carbonate-based geochemical proxies in an open marine system. Given the trace amounts of Mg in marine carbonates relative to coexisting pore fluids, diagenesis can alter carbonate δ 26 Mg, a promising proxy for seawater δ 26 Mg that may help elucidate long-term changes in the global Mg cycle. Constraints on the effect of diagenetic recrystallization on carbonate δ 26 Mg are therefore critical for accurate proxy interpretations. This study provides context for assessing the fidelity of geochemical proxyreconstructions using the primary components (i.e., foraminiferal tests and nannofossils) of bulk carbonate sediments. We find that pore fluid δ 26 Mg values (on the DSM3 scale) at Site 1171 increase systematically with depth (from-0.72‰ to-0.39‰ in the upper ~260 m), while the δ 26 Mg of bulk carbonates decrease systematically with depth (from-2.23‰ to-5.00‰ in the upper ~260 m). This variability is ascribed primarily to carbonate recrystallization, with a small proportion of the variability due to down-hole changes in nannofossil and foraminiferal species composition. The inferred effect of diagenesis on bulk carbonate δ 26 Mg correlates with downcore changes in Mg/Ca, Sr/Ca, Na/Ca, and 87 Sr/ 86 Sr. A depositional reactive-transport model is employed to validate the hypothesis that calcite recrystallization in this system can generate sizeable shifts in carbonate δ 26 Mg. Model fits to the data suggest a fractionation factor and a partition coefficient that are consistent with previous work, assuming calcite recrystallization rates of ≤7%/Ma constrained by Sr geochemistry. In addition, either partial dissolution or a distinctly different previous diagenetic regime must be invoked in order to explain aspects of the elemental chemistry and 87 Sr/ 86 Sr of relatively deep sediments from Holes A and C. This study indicates that the dynamics of a given sedimentary system can significantly alter bulk carbonate geochemistry, and presents a framework for considering the potential impact of such alteration on picked archives such as foraminiferal tests and nannofossils. Ultimately, this study contributes to the development of δ 26 Mg as a proxy for seawater δ 26 Mg by quantifying the susceptibility of carbonate δ 26 Mg to diagenetic alteration, particularly in sediments in open marine systems. This study suggests that because of the sensitivity of carbonate δ 26 Mg to diagenetic recrystallization, it can, in certain systems, be used to quantify the impact of diagenesis on carbonate-based geochemical proxies.

Like Mary Wollstonecraft’s The Wrongs of Woman, Mary Hays’s The Victim of Prejudice (1799) and Amelia Opie’s Father and Daughter (1801) are experimental fictions that require the reader’s identification with a sexualized heroine marked as transgressive and persecuted by society. Indeed, as I suggest in the first chapter, Wollstonecraft’s Wrongs of Woman models the rebellious and outspoken Romantic heroine I am delineating. In many ways, Maria Venables represents an extreme of the type; she leaves her husband, takes a lover, and presents her case for divorce to a court of law. Her suit fails, but it is a noble failure. Furthermore, as Tilottama Rajan has taught us to recognize, Wollstonecraft’s unfinished narrative invites its readers to “complete the text by unfolding a truth it does not yet contain” (“Wollstonecraft and Godwin” 223). As I note in the Coda to Chapter 1, The Wrongs of Woman was published with six different endings, all drawn from the author’s working notes, most of w...

Detailed studies of carbonate mineralogy and geochemistry using samples recovered by deep-sea drilling in the northern Bahamas document shallow-burial (<250 mbsf) diagenetic trends that occur in two stages. Stage 1 diagenesis (0-10 meters below the seafloor, mbsf) results in rapid, extensive calcitization and local dolomitization in marine-derived pore fluids. Stable oxygen isotopes are quickly enriched, while carbon values are depleted. Aragonite undergoes dissolution and high-magnesian calcite exsolves to low-magnesian calcite. Below 10 to at least 185 mbsf, stage 2 diagenesis continues to alter primary components, leading to ooze-chalk and chalk-limestone transformations and low amounts of dolomite, while rates and amplitudes of change are considerably less than in stage 1. Oxygen-and carbon-isotope ratios indicate that diagenesis still occurs in marine-derived pore fluids. Overall, shallow-burial diagenesis of periplatform carbonates proceeds much more readily than diagenesis of deepsea pelagic ooze. This is because of higher diagenetic potential related to the influx of metastable shallow-water-derived components in a deep-marine realm. Subsurface calcitization and lithification of periplatform sediments occurs rapidly with depth in regions of moderate accumulation rates (20-60 m/m.y.; north of Little Bahama Bank). This is a result of an interpreted greater rate of diagenetic alteration with burial, and in deep (3000 m) water is related to seawater saturation levels relative to carbonate mineralogy. Calcitization and local dolomitization may occur at or near the sediment/ water interface during formation of disconformities. In contrast, metastable aragonite and high-magnesian calcite are present in significant amounts at depth in regions with high accumulation rates (>90 m/m.y., Exuma Sound), despite lithification that produces chalk and limestone. The presence of metastable components in porous limestones in Exuma Sound underscores the current high diagenetic potential for these rocks and the development of reservoir potential in periplatform deep-water limestones at shallow sub-bottom depths.

Interstitial water samples from Sites 834 through 839, drilled during Ocean Drilling Program Leg 135 in the backarc Lau basin (Southwestern Pacific), have been analyzed for major elements, manganese, copper, strontium, barium, vanadium, and 87 Sr/ 6 Sr isotopic composition values. The concentration-depth profiles of the major chemical components show almost straight concentration gradients at all sites, and seem to reflect slight alteration of volcanic material. However, in the lower part of the sedimentary cover, where volcanogenic material is abundant and where diagenetic minerals occur, systematic decreases in calcium, strontium, manganese, copper, and vanadium concentrations are observed. A downwelling flow of bottom seawater, which affected the diagenetic chemical signature of the interstitial water, is probably responsible for the recorded chemical features. This hypothesis is supported by strontium isotope data obtained from interstitial water samples at Site 835. It is also in accordance with data from heat flow and physical properties.

Two zooxanthellate, scleractinian species present in the equatorial eastern Pacific, Psammocora stellata and Psammocora profundacella, were examined in terms of their reproductive biology and ecology at four study sites, non-upwelling (Can ˜o Island, Costa Rica, and Uva Island, Panama ´), upwelling (Gulf of Panama ´, Panama ´), and seasonally varying thermal environments (Gala ´pagos Islands). Both species were gonochoric broadcast spawners lacking zooxanthellae in mature ova. Mature gametes and spawned gonads are present around full moon; however, no spawning was observed naturally or in outdoor aquaria. Mature gametes occurred in P. stellata at Can ˜o Island for nearly 6 months, and year round at Uva Island, both non-upwelling sites. Reproductively active colonies occurred mostly in the warmer months in the Gulf of Panama ´and Gala ´pagos Islands. In the Gala ´pagos Islands, where collecting effort was greatest for P. profundacella, mature gametes were also most prevalent during the warm season. Annual fecundity was high in both species, 1.3-1.8 9 10 4 ova cm -2 year -1 in P. stellata and 1.2-2.0 9 10 4 ova cm -2 year -1 in P. profundacella. Compared to other eastern Pacific corals, P. stellata was relatively resistant to ENSO-related bleaching and mortality, especially populations inhabiting deep (12-20 m) coral communities. Rapid recovery and persistence of Psammocora spp. can be attributed to several factors: (a) relative resistance to bleaching, (b) deep refuge populations, (c) broadcast spawning, (d) protracted seasonal reproduction, (e) high fecundity, and (f) asexual propagation. Communicated by J. P. Grassle.

Basaltic breccias cored at Hole 373A contain four generations of internally resedimented interclast limestone and four generations of void-filling calcite cement. Two of the limestone generations are pelagic carbonate oozes that infiltrated from the sea floor into voids. The other two generations of limestone apparently originated as diagenetic sediment which was precipitated and deposited within breccia interstices. Superimposed upon this complex pattern of resedimentation and cementation were repeated episodes of brecciation and fracturing. Oxygen and carbon isotopic compositions indicate that cementation of the breccias and lithification of the carbonate sediments occurred at low temperatures characteristic of deep bottom waters. Much if not all of this sea-floor carbonate diagenesis may be related to low temperature, submarine alteration of basalt. Ferruginous dolomites which lie stratigraphically above the basalts likewise formed at low temperatures, probably also as a conseque...

World demand for rare-earth elements and the metal yttrium-which are crucial for novel electronic equipment and green-energy technologies-is increasing rapidly 1-3. Several types of seafloor sediment harbour high concentrations of these elements 4-7. However, seafloor sediments have not been regarded as a rare-earth element and yttrium resource, because data on the spatial distribution of these deposits are insufficient. Here, we report measurements of the elemental composition of over 2,000 seafloor sediments, sampled at depth intervals of around one metre, at 78 sites that cover a large part of the Pacific Ocean. We show that deep-sea mud contains high concentrations of rare-earth elements and yttrium at numerous sites throughout the eastern South and central North Pacific. We estimate that an area of just one square kilometre, surrounding one of the sampling sites, could provide one-fifth of the current annual world consumption of these elements. Uptake of rare-earth elements and yttrium by mineral phases such as hydrothermal iron-oxyhydroxides and phillipsite seems to be responsible for their high concentration. We show that rare-earth elements and yttrium are readily recovered from the mud by simple acid leaching, and suggest that deep-sea mud constitutes a highly promising huge resource for these elements. At present, 97% of the world's production of rare-earth elements and yttrium (REY) is accounted for by China, although China has only one-third of global reserves and the Commonwealth of Independent States, the United States, and Australia together have another one-third of reserves 1. China's dominance pertains to heavy rare-earth elements (HREE; conventionally Gd to Lu, but Eu is included here), which are especially important materials for high-technology products including electric automobiles and flatscreen televisions 8. HREE reserves are almost all in ion-absorptiontype ore deposits in southern China, whereas light REE (LREE) can be obtained from carbonatite/alkaline igneous complexes in other countries 1-3. We report here the great potential of deep-sea REY-rich mud in the Pacific Ocean as a new mineral resource for REY, especially HREE, because the mud commonly has a higher HREE/LREE ratio than the southern China ion-absorption-type deposits, as described below. We studied drill core samples from 51 sites obtained by the Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) and piston core samples from 27 sites obtained by the Ocean Research Institute, the University of Tokyo (Supplementary Table S1), which cover a major portion of the Pacific Ocean (Fig. 1). Many of the DSDP/ODP holes penetrated a depth greater than 50 m below seafloor (mbsf), whereas most of the University of Tokyo piston

Advances in our knowledge of eastern tropical Pacific (ETP) coral reef biogeography and ecology during the past two decades are briefly reviewed. Fifteen ETP subregions are recognized, including mainland and island localities from the Gulf of California (Mexico) to Rapa Nui (Easter Island, Chile). Updated species lists reveal a mean increase of 4.2 new species records per locality or an overall increase of 19.2 % in species richness during the past decade. The largest increases occurred in tropical mainland Mexico, and in equatorial Costa Rica and Colombia, due mainly to continuing surveys of these under-studied areas. Newly discovered coral communities are also now known from the southern Nicaraguan coastline. To date 47 zooxanthellate scleractinian species have been recorded in the ETP, of which 33 also occur in the central/south Pacific, and 8 are presumed to be ETP endemics. Usually no more than 20-25 zooxanthellate coral species are present at any given locality, with the principal reef-building genera being Pocillopora, Porites, Pavona, and Gardineroseris. This compares with 62-163 species at four of the nearest central/south Pacific localities. Hydrocorals in the genus Millepora also occur in the ETP and are reviewed in the context of their global distributions. Coral community associates engaged in corallivory, bioerosion, and competition for space are noted for several localities. Reef framework construction in the ETP typically occurs at shallow depths (2-8 m) in sheltered habitats or at greater depths (10-30 m) in more exposed areas such as oceanic island settings with high water column light penetration. Generally, eastern Pacific reefs do not reach sea level with the development of drying reef flats, and instead experience brief periods of exposure during extreme low tides or drops in sea level during La Niña events. High rates of mortality during El Niño disturbances have occurred in many ETP equatorial areas, especially in Panama and the Galápagos Islands during the 1980s and 1990s. Remarkably, however, no loss of resident, zooxanthellate scleractinian species has occurred at these sites, and many ETP coral reefs have demonstrated significant recovery from these disturbances during the past two decades.

One of the fundamental hypotheses in aquatic ecology deals with the recognition of fish stocks. The present study tested the spatial dynamics of starry sturgeon stocks across environmental gradients by spatial variability in strontium to calcium in the pectoral fin spine. Forty samples of starry sturgeon were collected from the north and south of the Caspian Sea. A quantitative method was used to examine stocks using digested pectoral fin spine, reflecting habitat characters of fish. Parts of pectoral fin spines from adult starry sturgeon were separated and analyzed using Inductively Coupled Plasma- Mass Spectrometry (ICP-MS). Comparisons of Sr/Ca ratios in digested spines of the fish from north and south of the Caspian Sea demonstrated that Sr/Ca varied in the region and this significance was reflected in the spine as well. Our results for starry sturgeon support the use of spine Sr/Ca as a proxy for ambient levels throughout their life-history, confident interpretation of life history from spine Sr/Ca chronologies, however likely require matching time series of ambient Sr/Ca in the water bodies of interest.

I DSDP Sites 5011504 e 505 sono situati al f i a ~c o meridionale del Costa Rica Rift. I sedimenti delle due località sono simili per composizione, spessore ed ambiente deposizionale ma differiscono profondamente nel grado di diagenesi subita. Ai Sites 5011 504 i sedimenti inconsolidati della parte superiore passano verso i 144 m a chalk e quindi a calcari e selci al di sotto dei 227 m. Nessuna litificazione importante è invece presente al Site 505. La composizione isotopica dell'ossigeno dell'acqua interstiziale e dei carbonati delle due località è molto differente. I1 6018 dei fluidi dei Sites 5011504 rivela un nde~letion trend)) molto marcato mentre i valori isotopici del Site 505 sono prossimi a SMOW. I1 6018 dei carbonati delle due località sono molto simili con l'eccezione dei campioni più profondi. A 230 m il 6018 dei carbonati del Site 501 presenta valori fino a 27% (SMOW). Tale differenza isotopica sembra correlata alla ricristallizzazione dei carbonati. La diminuzione del 60'' dei carbonati nel Site 501 è accompagnata da un aumento del 6018 dei fluidi interstiziali nei Sites 5011504. I1 60" dei fluidi interstiziali decresce fino a 230 m dove si ha un'inversione di tendenza. Tale inversione suggerisce che le variazioni osservate nei due 6018 siano interdipendenti.

Advances in our knowledge of eastern tropical Pacific (ETP) coral reef biogeography and ecology during the past two decades are briefly reviewed. Fifteen ETP subregions are recognized, including mainland and island localities from the Gulf of California (Mexico) to Rapa Nui (Easter Island, Chile). Updated species lists reveal a mean increase of 4.2 new species records per locality or an overall increase of 19.2 % in species richness during the past decade. The largest increases occurred in tropical mainland Mexico, and in equatorial Costa Rica and Colombia, due mainly to continuing surveys of these under-studied areas. Newly discovered coral communities are also now known from the southern Nicaraguan coastline. To date 47 zooxanthellate scleractinian species have been recorded in the ETP, of which 33 also occur in the central/south Pacific, and 8 are presumed to be ETP endemics. Usually no more than 20-25 zooxanthellate coral species are present at any given locality, with the principal reef-building genera being Pocillopora, Porites, Pavona, and Gardineroseris. This compares with 62-163 species at four of the nearest central/south Pacific localities. Hydrocorals in the genus Millepora also occur in the ETP and are reviewed in the context of their global distributions. Coral community associates engaged in corallivory, bioerosion, and competition for space are noted for several localities. Reef framework construction in the ETP typically occurs at shallow depths (2-8 m) in sheltered habitats or at greater depths (10-30 m) in more exposed areas such as oceanic island settings with high water column light penetration. Generally, eastern Pacific reefs do not reach sea level with the development of drying reef flats, and instead experience brief periods of exposure during extreme low tides or drops in sea level during La Niña events. High rates of mortality during El Niño disturbances have occurred in many ETP equatorial areas, especially in Panama and the Galápagos Islands during the 1980s and 1990s. Remarkably, however, no loss of resident, zooxanthellate scleractinian species has occurred at these sites, and many ETP coral reefs have demonstrated significant recovery from these disturbances during the past two decades.

Since 1982, coral reefs worldwide have been subjected to an increased frequency of the phenomenon known as coral bleaching. Bleaching involves the dramatic loss of pigmented, single-celled endosymbiotic algae that live within the gastrodermal cells of a coral host that depends on this relationship for survival. Prior to the 1980s, and as early as the 1920s when coral reef research intensified, localized bleaching events were reported and attributed to factors such as extremely low tides, hurricane damage, torrential rainstorms, fresh water runoff near reefs, or toxic algal blooms [Glynn, 1993]. However, these early occur rences have recently been overshadowed by geographically larger and more frequent bleach ing events whose impact has expanded to regional and global proportions.

The Mexican Central Pacific is located in a zone of oceanographic transition between two biogeographic provinces with particular conditions that affect the associated fauna. The objective of this study was to evaluate the variation of hermatypic coral assemblages in this region and to determine their relationship with the heterogeneity of the benthonic habitat and spatial variables. A total of 156 transects were carried out at 41 sites in the years 2010 and 2011. The sampling effort returned 96.7% of the coral richness expected for the area, with a total of 15 species recorded. The results showed that richness, diversity and cover of corals varied only at the site and state scales. However, the composition and coverage of all coral species, as well as the benthonic habitat structure, differed significantly across the study scales (i.e. sites, zones and states). Canonical redundancy analysis showed that variation in the richness, diversity and assemblages of corals was explained by t...

57 Fe Mössbauer spectra of 15 oceanic sediment samples collected from Site 612 (Deep Sea Drilling Project Leg 95) were recorded. These spectra showed that most of the iron in the sediments was present as high-spin, paramagnetic Fe 2+ and Fe 3 +. The ferrous iron was mainly distributed in terrigenous clays and biogenic carbonates. The variation of the Mössbauer parameters for Fe 2+ with sub-bottom depth suggests that the main Fe 2+-bearing component changed with geologic time. The amount of iron in each iron-bearing phase as estimated from the corresponding peak areas in the spectra also changed with depth. These variations in the Mössbauer parameters and peak areas are correlated with lithologic changes in the sediment column.