Growth Bands Research Articles

Growth, population dynamics, and reproductive output model of the non‐zooxanthellate temperate solitary coral Caryophyllia inornata (Scleractinia, Caryophylliidae)

AbstractCoral age can be strictly related to size, but processes like fragmentation, fusion, and partial colony mortality can decouple this relationship. When these phenomena are negligible, such as in solitary corals, age‐based growth and population dynamics models can be used. In this study, the population size, structure, and growth rates of the temperate solitary coral Caryophyllia inornata were assessed at Elba Island (north‐western Mediterranean Sea). Growth rate of this species decreased exponentially with age. The two growth curves estimated by field measurements and by growth band analysis provided homogeneous relationships between size and age. The decreasing number of individuals with age indicated a steady state population, with a turnover time of 4 yr and a maximum life span of 22 yr. Maximum biomass yield and most reproductive output was by individuals of 8–15 yr age classes. The life strategy was characterized by high fecundity, continuous embryo production, high larval output, and high larval mortality.

Distribution Pattern, Age, and Growth of Blue Sharks in the South Atlantic Ocean

AbstractThe distribution pattern and the age and growth of Blue Sharks Prionace glauca were described based on 44,092 and 785 specimens, respectively, that were collected by scientific observers onboard Taiwanese longline fleets in the South Atlantic Ocean between December 2004 and December 2013. Size segregation was found, and the mean length of Blue Sharks was significantly larger in the equatorial–tropical area (0–15°S) than in the subtropical–temperate area (south of 15°S) during all seasons. Males predominated in both areas and during all seasons; the exceptions were seasons 2 (April–June) and 3 (July–September) in the equatorial–tropical area and season 2 in the subtropical–temperate area. The sex ratio increased with shark size in the equatorial–tropical area but decreased with size in the subtropical–temperate area. Growth band pairs (including translucent and opaque bands) were counted on images photographed from X‐ray films of vertebrae from the caudal peduncle region. The centrum edge analysis indicated that a growth band pair was formed on the vertebral centrum once per year. Corrected Akaike's information criterion values indicated that the von Bertalanffy growth function (VBGF) provided the best fit to the observed TL‐at‐age data. The likelihood ratio test indicated that the VBGF equations were not significantly different between the sexes. For both sexes combined, VBGF parameters were estimated as follows: asymptotic length was 352.1 cm TL, the Brody growth coefficient was 0.13/year, and the theoretical age at zero length was –1.31 years. Age at first maturity was estimated as 6.5 years for males and 6.7 years for females; theoretical longevity was estimated to be at least 21.4 years.

Carbon nanotubes and core–shell rubber nanoparticles modified structural epoxy adhesives

In this study, multi-walled carbon nanotubes (MWCNTs) and core–shell rubber (CSR) nanoparticles were dispersed in an epoxy adhesive to produce conductive and tough structural adhesives. The thermo-mechanical properties, electrical conductivity, fracture toughness and lap shear strength of MWCNT–CSR–epoxy structural adhesives were studied. The addition of both MWCNTs and CSR nanoparticles into the epoxy adhesive increased the fracture energy significantly, from 397 J/m2 for the unmodified adhesive, to 2615 J/m2, for an adhesive modified with 10 wt% CSR nanoparticles and 0.3 wt% MWCNTs. The toughening mechanisms of the CSR nanoparticles were identified as cavitation of the rubber particles followed by plastic void growth and shear band yielding. The toughening enhancement of the MWCNTs was mainly attributed to the crack bridging, MWCNT break and crack path deflection. The addition of CSR nanoparticles into neat epoxy was found to affect the failure mode of the lap shear joints, from brittle, interfacial failure, to a ductile, cohesive failure. A moderate increase in the strength of the lap shear joint was also noted. The subsequent addition of MWCNTs further affected the failure mode of the lap shear joints. A mixture of interfacial and cohesive failure was observed for each joint configuration. The lap shear strength was observed to have increased significantly, by 39%, due to the addition of 0.5 wt% MWCNTs. The observed increase in lap shear strength with the addition of MWCNTs was attributed to the crack deflection caused by the MWCNTs.

Skeletal microstructure of uintacrinoid crinoids and inferences about their mode of life

Uintacrinoids (Uintacrinoidea) are among the most bizarre of all the crinoids. These stratigraphically important Late Cretaceous crinoids are characterized by an atypical large stalkless globular cup without cirriferous centrodorsal and extremely long arms. Owing to this unusual morphology, the mode of life of these crinoids has confused palaeontologists for more than a century. While uintacrinoids have been commonly regarded as pelagic forms, either swimming actively or floating passively by means of a putative buoyancy mechanism, some recent authors have favoured a benthic mode of life. However, evidence supporting a benthic lifestyle hypothesis is still limited. Here we describe the stereom microstructure of Marsupites and Uintacrinus. In Marsupites, thecal plates are typically comprised of coarse to medium, clearly structural, galleried stereom, which alternates with zones of fine and deeply penetrating galleried stereom oriented perpendicular to the plate margins. The latter stereom type corresponds to the external ribbed ornament of the theca, and is indicative of collagenous sutural fibers for binding adjacent plates. In Uintacrinus, thecal plates are almost entirely composed of fine galleried stereom diagnostic for collagenous sutural fibers. In both taxa, a perforate stereom layer, that is known to increase plate strengthening and resistance to abrasion in some Recent echinoderms, is developed most externally, and also produces a characteristic interior growth banding pattern. No skeletal adaptations for maintaining buoyancy, such as skeletal lightening and hollow architecture, that are known to occur in nektonic and pseudoplanktonic crinoids, are observed. Instead, the stereom organization in uintacrinoids closely resembles those observed in Recent benthic crinoids. Our findings thus strongly support a benthic mode of life of uintacrinoids. Their widespread distribution within a short time interval can be best explained by having a very long-term planktonic larval stage as previously hypothesized by some authors.

The transfer of bomb radiocarbon and anthropogenic lead to the deep North Atlantic Ocean observed from a deep sea coral

Deep-ocean, ΔC14, Pb concentrations, and Pb isotopes were reconstructed from a deep-sea coral Enallopsammia rostrata from 1410 m depth off of Bermuda. Our high-resolution time series is created from closely spaced radial cross sections, with samples taken from the center of concentric coral growth bands that we show to be the oldest portion of the section. Prebomb radiocarbon ages from the coral demonstrate that the vertical growth rate of the coral is linear, and the age of the coral is estimated to be 560–630 yr old based on the growth rate. Using this age model to reconstruct ΔC14 in deep seawater, we first detect bomb radiocarbon at the coral growth site around 1980, and show that ΔC14 increased from −80±1‰ (average 1930–1979) to a plateau at −39±3‰ (1999–2001). Pb/Ca of the coral ranges between 1.1–4.5 nmol/mol during the 16th and 17th centuries, and Pb isotope ratios (206Pb/207Pb = 1.21, 208Pb/207Pb = 2.495) in this period agree with pre-anthropogenic values found in the pelagic sediments of the North Atlantic Ocean basin. Coral Pb/Ca is slightly elevated to 6.2±0.9 nmol/mol between the 1740s and the 1850s and then increases to 25.1±0.2 nmol/mol in the 1990s. The increase in coral Pb/Ca is accompanied by a decrease in coral 206Pb/207Pb and 208Pb/207Pb, indicating that the increase was caused by the infiltration of anthropogenic Pb to the coral growth site. Comparing our data to the surface coral ΔC14 and Pb records from Bermuda reveals a time scale of tracer transport from the surface ocean to the coral growth site. Some characteristic features, e.g., the bomb-derived ΔC14 increase, appear in the deep ocean approximately 25 yr later than the surface, but the overall increase of ΔC14 and Pb in the deep ocean is smaller and slower than the surface, showing the importance of mixing during the transport of these tracers.

Age determination and growth rate of Mactra chinensis (Bivalvia: Mactridae) by external rings and chondrophore growth bands

Age, growth and mortality of Mactra chinensis were investigated during the period from October 2012 to September 2013 in Busan, South Korea. The monthly variation of the marginal index (MI) of the shell and chondrophore showed that the ring of this species was formed once a year during July. We estimated the age of M. chinensis by reading the external rings on the shell and the growth bands of the chondrophore to compare growth parameters between the two growth characters. The age of this species ranged from 0 to 8 years (shell-based age reading) and from 0 to 10 years (chondrophore-based age reading). Based on external rings and growth bands of chondrophore for the same period, the von Bertalanffy growth functions were expressed by the equation, Lt = 101.53[1-exp {-0.15(t + 0.75)}] and Lt = 90.03[1-exp {-0.20(t + 0.50)}], respectively. The likelihood test showed that there was a significant difference in L∞ (P < 0.001), K (P < 0.001), to (P < 0.001) estimated from non-linear regression between the two growth characters.

Cementum structure in Beluga whale teeth.

Cementum is an important tooth tissue to which the periodontal ligaments attach and consists primarily of carbonated apatite mineral and collagen. In optical microscopy of cementum thin sections, light/dark bands are formed annually, and age at death is determined by counting these bands. We employ synchrotron X-ray diffraction and X-ray fluorescence mapping to show the bands in Beluga whale cementum result from differences in mineral content and not from differences in collagen orientation as was concluded by others. Variation in Zn fluorescent intensity was found to be very sensitive indicator of changing biomineralization and suggest that Zn plays an important role this process.

Re-evaluation of using rhodolith growth patterns for paleoenvironmental reconstruction: An example from the Gulf of Panama

Rhodoliths are a proxy data source for understanding environment and climate variation in tropical to arctic oceans. A clear understanding of growth pattern and rate is required to interpret time-series proxy data. Variability in growth on multiple-axes of a single rhodolith has not been extensively studied. This investigation compares algal band counting and dating methods found in the literature, and has implications for detecting biases in branch selection for growth and geochemical analyses. Panamanian rhodoliths (Lithothamnion sp.) were collected at the Archipelago de Las Perlas, Gulf of Panama (GOP). Alizarin Red S (ARS) stain was used to study growth rates and banding patterns for 10 branched samples randomly selected for microcosm experiments over a 172-day period. DNA analysis was used to help determine the dominant species present in the sample group and reduce the possibility of inter-sample variation. Samples were overturned every 2weeks for a multi-axial growth test and were grown under ambient seawater conditions except for the addition of LED lighting. Growth post-ARS staining was measured along the long (A), intermediate (B), and short (C) axes. Bisected branches show banding correlated with growth rate while banding was highly variable within an individual and between individuals. Average growth band widths in both the pre- and post-ARS stained growth were approximately the same, suggesting that non-environmental factors, such as overturning or biological influences, can cause the formation of growth increments. Differences in growth pattern and rate suggest that careful inspection of growth formation is needed before pursuing rhodolith-based time series proxy research.

SPINICAUDATANS FROM THE UPPER JURASSIC OF ARGENTINA AND THEIR PALEOENVIRONMENTS

Fil: Monferran, Mateo Daniel. Universidad Nacional del Nordeste; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Centro de Ecologia Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecologia Aplicada del Litoral; Argentina

Assessing multi-site δ18O-climate calibrations of the coralline alga Clathromorphum across the high-latitude Northern Hemisphere

An increased number of climate proxy records and more refined interpretation of proxy data are crucial to improve projections of future climate at high latitudes, where internal feedbacks amplify warming and established high-resolution climate archives are especially sparse. Encrusting coralline algae are being developed as a mid- to high-latitude marine climate archive. These long-lived algae form a solid high-Mg calcite skeleton with annual growth bands similar to those of trees and tropical corals. The oxygen isotope ratio of the algal skeleton (δ18Oalg) records local environmental and climatic factors, notably sea surface temperature and seawater δ18O.Here we assess the δ18Oalg–climate relationship in diverse environments across the algal habitat range utilizing two species of coralline algae from the genus Clathromorphum. Clathromorphum is widely distributed from the cold-temperate North Atlantic and Pacific to the Arctic Ocean and has recently yielded numerous climate reconstructions of up to 650years in length. In this study, we calibrate δ18Oalg of four specimens to gridded temperature and salinity data, the latter a proxy for seawater δ18O. These specimens were collected from a variety of algal growth environments across the high-latitude Northern Hemisphere: two specimens from the Aleutian Archipelago, one from the Canadian Arctic, and one from the Gulf of Maine. Low winter temperatures and insolation restrict the months when algae record local climate in the δ18O of their skeletons; we therefore determine these response seasons by correlating monthly temperature and salinity anomalies with annual δ18Oalg anomalies at each site. We then average gridded data over months that correlate significantly (95% confidence interval) for regression with δ18Oalg. While the timing and nature of the climate signal vary across sites, we find significant relationships between δ18Oalg and either temperature or salinity averaged over the response season at three sites. Variation in local climatology among the four sites provides a physical explanation for calibration differences, compounded by uncertainties stemming from the proxy chronology, biological variability, temporal coverage, and sparse historical climate data. This work takes an essential step toward reconstructing high-latitude marine climate patterns with coralline algal δ18O and developing algae proxy system models.

Low Florida coral calcification rates in the Plio-Pleistocene

Abstract. In geological outcrops and drill cores from reef frameworks, the skeletons of scleractinian corals are usually leached and more or less completely transformed into sparry calcite because the highly porous skeletons formed of metastable aragonite (CaCO3) undergo rapid diagenetic alteration. Upon alteration, ghost structures of the distinct annual growth bands often allow for reconstructions of annual extension ( = growth) rates, but information on skeletal density needed for reconstructions of calcification rates is invariably lost. This report presents the bulk density, extension rates and calcification rates of fossil reef corals which underwent minor diagenetic alteration only. The corals derive from unlithified shallow water carbonates of the Florida platform (south-eastern USA), which formed during four interglacial sea level highstands dated approximately 3.2, 2.9, 1.8, and 1.2 Ma in the mid-Pliocene to early Pleistocene. With regard to the preservation, the coral skeletons display smooth growth surfaces with minor volumes of marine aragonite cement within intra-skeletal porosity. Within the skeletal structures, voids are commonly present along centres of calcification which lack secondary cements. Mean extension rates were 0.44 ± 0.19 cm yr−1 (range 0.16 to 0.86 cm yr−1), mean bulk density was 0.96 ± 0.36 g cm−3 (range 0.55 to 1.83 g cm−3) and calcification rates ranged from 0.18 to 0.82 g cm−2 yr−1 (mean 0.38 ± 0.16 g cm−2 yr−1), values which are 50 % of modern shallow-water reef corals. To understand the possible mechanisms behind these low calcification rates, we compared the fossil calcification rates with those of modern zooxanthellate corals (z corals) from the Western Atlantic (WA) and Indo-Pacific calibrated against sea surface temperature (SST). In the fossil data, we found a widely analogous relationship with SST in z corals from the WA, i.e. density increases and extension rate decreases with increasing SST, but over a significantly larger temperature window during the Plio-Pleistocene. With regard to the environment of coral growth, stable isotope proxy data from the fossil corals and the overall structure of the ancient shallow marine communities are consistent with a well-mixed, open marine environment similar to the present-day Florida Reef Tract, but variably affected by intermittent upwelling. Upwelling along the platform may explain low rates of reef coral calcification and inorganic cementation, but is too localised to account also for low extension rates of Pliocene z corals throughout the tropical WA region. Low aragonite saturation on a more global scale in response to rapid glacial–interglacial CO2 cyclicity is also a potential factor, but Plio-Pleistocene atmospheric pCO2 is generally believed to have been broadly similar to the present day. Heat stress related to globally high interglacial SST only episodically moderated by intermittent upwelling affecting the Florida platform seems to be another likely reason for low calcification rates. From these observations we suggest some present coral reef systems to be endangered from future ocean warming.

Estimates of life history parameters of the oceanic whitetip shark, Carcharhinus longimanus, in the Western North Pacific Ocean

ABSTRACTThe age, growth and reproduction of the oceanic whitetip shark, Carcharhinus longimanus, in the western North Pacific Ocean were estimated based on 188 specimens (89 females and 99 males) collected before the prohibition of retaining on board for commercial use by the Western and Central Pacific Fisheries Commission (from November 2002 to January 2006) at the Nanfanao fish market in north-eastern Taiwan. The relationship between body weight (W) and total length (TL) for both sexes combined was estimated as follows: (n = 188, P < 0.01). The relationship between TL and the pre-caudal vertebral centrum radius (R) for sexes-combined data was described using the following equation: TL = 29.98 + 20.99R (n = 112, P < 0.05). The opaque bands in pre-caudal vertebrae are formed once annually between June and September based on a marginal increment ratio analysis. The maximum number of growth band pairs was 12 for both sexes in this study. The two-parameter von Bertalanffy growth function best fits the length-at-age data, and the growth parameters (sexes combined) were estimated as follows: asymptotic length (L∞) = 309.4 cm TL and growth coefficient (k) = 0.085/yr with the size at birth set as 64 cm TL (n = 112, P < 0.01). The litter size was 10–11, and the size at birth was at least 64 cm TL. The sizes at first and 50% maturity were 190 cm and 193.4 ± 0.97 cm TL for females and 172 cm and 194.4 ± 6.57 cm TL for males. These corresponded to 8.5 yr and 8.8 yr for females and 6.8 yr and 8.9 yr for males.

Exploring the oxygen and carbon isotopic composition of the Mediterranean red coral (Corallium rubrum) for seawater temperature reconstruction

Here we provide first evidence that the stable oxygen and carbon isotopic composition (δ18O, δ13C) of the high-magnesium calcite skeleton red coral Corallium rubrum can be used as a reliable seawater temperature proxy. This is based upon the analyses of living colonies of C. rubrum from different depths and localities in the Western Mediterranean Sea. The assessment of the growth rates has been established through the analysis of growth band patterns. The δ18O and δ13C compositions show large variability with a significant difference between the branches and the bases of the colonies. In both coral portions, the δ18O and δ13C values are highly correlated and show well-defined linear trends. Following the “lines technique” approach developed by Smith et al. (2000) for scleractinian aragonitic deep-water corals, our data have been combined with published values for the deep-sea gorgonian corals Isididae and Coralliidae from Kimball et al. (2014) and Hill et al. (2011) resulting in the following δ18O temperature equation:T°C=−5.05±0.24×δ18Ointercept+14.26±0.43R2=0.962pvalue<0.0001The error associated with this equation is ±0.5°C at the mean temperature of the data set, ±0.7°C for corals living in 2°C water and ±1°C for coral living in warmer water (17°C).The highly significant δ18Ointercept vs. temperature relationship combined with the “lines technique” method can be reliably applied to the calcitic skeleton to obtain calcification temperature estimates in the past, although this approach requires the knowledge of the past δ18O and δ13C composition of seawater and it is labor and time intensive.

Strontium mineralization of shark vertebrae.

Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands.

Validation of annulus formation and growth estimation of South Atlantic swordfish

Swordfish (Xiphias gladius) is heavily exploited in the Atlantic Ocean by several European fleets and age and growth studies are essential for the accomplishment of the stock assessments carried out by ICCAT. The present study aims to validate the periodicity of growth increments on swordfish fin spines and provide first estimates of the growth parameters of South Atlantic swordfish. A total of 502 (231 males and 271 females) spine samples were collected from swordfish specimens onboard commercial longline vessels, from 2006 to 2009. Estimated ages ranged between 0 and 12 years, with age groups 3 and 4 dominating the samples. Marginal increment analysis suggested that growth bands were deposited annually in mid-spring. Fitted standard von Bertalanffy growth parameters (sexes combined) were L∞ = 317.133, k = 0.085 and t0 = −2.488. Minor, but insignificant, growth differences were observed between sexes.

Optical and X-Ray Topographic Studies of Dislocations, Growth-Sector Boundaries, and Stacking Faults in Synthetic Diamonds

The characterization of growth features and defects in various high-pressure high-temperature (HPHT) synthetic diamonds has been achieved with optical and X-ray topographic techniques. For the X-ray studies, both characteristic and synchrotron radiation were used. The defects include dislocations, stacking faults, growth banding, growth sector boundaries, and metal inclusions. The directions of the Burgers vectors of many dislocations (edge, screw, and mixed 30°, 60°, and 73.2°), and the fault vectors of stacking faults, were determined as &lt;110&gt; and 1/3 &lt;111&gt; respectively. Some dislocations were generated at metallic inclusions; and some dislocations split with the formation of stacking faults.

Carbon and Oxygen Isotope Records from Tridacna derasa Shells: Toward Establishing a Reliable Proxy for Sea Surface Environments.

We report the carbon (δ13C) and oxygen (δ18O) isotope records of three modern Tridacna derasa shells from Ishigaki-jima, southwestern Japan. The high-resolution δ13C profiles of samples from the inner shell layer on cross-sections fall within similar narrow ranges and display no regular variations or trends, such as an ontogenetic trend or abrupt short-term drops likely to be related to reproductive activity. This suggests that the calcification site of this species is not likely affected by photosynthetic CO2 uptake or CO2 incorporation during respiration. The δ18O profiles show distinct seasonal cycles. The intraspecific variability in the δ18O values is small in parts of the shell precipitated in the adult stage, but is not negligible in the juvenile and senescent stages. The differences in the monthly and seasonally resolved δ18O values among shells are less than 0.51‰ and 0.76‰, respectively. The shell δ18O values are nearly identical or close to the δ18O values for aragonite precipitated in oxygen isotope equilibrium with ambient seawater (δ18OEA). The largest differences between the shell δ18O and δ18OEA values calculated from the monthly and seasonally resolved data correspond to an overestimate of the seawater temperature by as much as 1.7°C and 2.3°C, respectively. However, these differences are smaller in the adult stage (<0.25‰) than in the other stages. This small difference allows an accurate reconstruction of the seawater temperature with an error of <1.1°C. Consequently, we recommend that multiple shell records be obtained because of the non-negligible intraspecific variations in their δ18O values. Growth banding, composed of alternating narrow white bands and wide light-grey bands, is discernible on cross-sections of the inner shell layer. The δ18Oshell data indicate that they were formed in winter and the other seasons, respectively.

Growth mechanisms and band bending in Cu and Pt on Ge(001) investigated by LEED and photoelectron spectroscopy

We investigate band bending effects occurring at the interface between atomically clean Ge(001) and molecular beam epitaxy (MBE) deposited copper and platinum. Low energy electron diffraction (LEED) confirmed the crystallinity of the surface, evidenced the formation of (2×1) and (1×2) reconstructions, and revealed that it is strongly affected with metal deposition. X-ray photoelectron spectroscopy (XPS) data let us assume a Stranski–Krastanov growth mechanism and confirmed that the observed band bending is associated to an ohmic contact in both cases. For the platinum contact, the high values of the apparent inelastic mean free path (IMFP) derived from the evolution of the XPS intensities indicate a prevalence of mixture of Pt with Ge nearby the interface. Pt deposited on Ge(001) does not behave like a Schottky contact, as one may have expected due to the higher work function of platinum. The observed effect is similar to the case where interfacial Pt had a lower work function by 2.25/1.96eV than that of metallic Pt. We propose a model to explain this fact by the effective mass variation or to the conduction band broadening due to the strong intermixing of platinum with germanium under the surface.

Sex-associated variations in coral skeletal oxygen and carbon isotopic composition of &amp;lt;i&amp;gt;Porites panamensis&amp;lt;/i&amp;gt; in the southern Gulf of California

Abstract. Coral δ18O variations are used as a proxy for changes in sea surface temperature (SST) and seawater isotope composition. Skeletal δ13C of coral is frequently used as a proxy for solar radiation because most of its variability is controlled by an interrelationship between three processes: photosynthesis, respiration, and feeding. Coral growth rate is known to influence the δ18O and δ13C isotope record to a lesser extent than environmental variables. Recent published data show differences in growth parameters between female and male coral in the gonochoric brooding coral Porites panamensis; thus, skeletal δ18O and δ13C are hypothesized to be different in each sex. To test this, this study describes changes in the skeletal δ18O and δ13C record of four female and six male Porites panamensis coral collected in Bahía de La Paz, Mexico, whose growth bands spanned 12 years. The isotopic data were compared to SST, precipitation, photosynthetically active radiation (PAR), chlorophyll a, and skeletal growth parameters. Porites panamensis is a known gonochoric brooder whose growth parameters are different in females and males. Splitting the data by sexes explained 81 and 93 % of the differences of δ18O, and of δ13C, respectively, in the isotope record between colonies. Both isotope records were different between sexes. δ18O was higher in female colonies than in male colonies, with a 0.31 ‰ difference; δ13C was lower in female colonies, with a 0.28 ‰ difference. A difference in the skeletal δ18O could introduce an error in SST estimates of ≈ 1.0 to ≈ 2.6 °C. The δ18O records showed a seasonal pattern that corresponded to SST, with low correlation coefficients (−0.45, −0.32), and gentle slopes (0.09, 0.10 ‰ °C−1) of the δ18O–SST relation. Seasonal variation in coral δ18O represents only 52.37 and 35.66 % of the SST cycle; 29.72 and 38.53 % can be attributed to δ18O variability in seawater. δ13C data did not correlate with any of the environmental variables; therefore, variations in skeletal δ13C appear to be driven mainly by metabolic effects. Our results support the hypothesis of a sex-associated difference in skeletal δ18O and δ13C signal, and suggest that environmental conditions and coral growth parameters affect skeletal isotopic signals differently in each sex. Although these findings relate to one gonochoric brooding species, they may have some implications for the more commonly used gonochoric spawning species such as Porites lutea and Porites lobata.

Oxygen Isotope Variability within Nautilus Shell Growth Bands.

Nautilus is often used as an analogue for the ecology and behavior of extinct externally shelled cephalopods. Nautilus shell grows quickly, has internal growth banding, and is widely believed to precipitate aragonite in oxygen isotope equilibrium with seawater. Pieces of shell from a wild-caught Nautilus macromphalus from New Caledonia and from a Nautilus belauensis reared in an aquarium were cast in epoxy, polished, and then imaged. Growth bands were visible in the outer prismatic layer of both shells. The thicknesses of the bands are consistent with previously reported daily growth rates measured in aquarium reared individuals. In situ analysis of oxygen isotope ratios using secondary ion mass spectrometry (SIMS) with 10 μm beam-spot size reveals inter- and intra-band δ18O variation. In the wild-caught sample, a traverse crosscutting 45 growth bands yielded δ18O values ranging 2.5‰, from +0.9 to -1.6 ‰ (VPDB), a range that is larger than that observed in many serial sampling of entire shells by conventional methods. The maximum range within a single band (~32 μm) was 1.5‰, and 27 out of 41 bands had a range larger than instrumental precision (±2 SD = 0.6‰). The results from the wild individual suggest depth migration is recorded by the shell, but are not consistent with a simple sinusoidal, diurnal depth change pattern. To create the observed range of δ18O, however, this Nautilus must have traversed a temperature gradient of at least ~12°C, corresponding to approximately 400 m depth change. Isotopic variation was also measured in the aquarium-reared sample, but the pattern within and between bands likely reflects evaporative enrichment arising from a weekly cycle of refill and replacement of the aquarium water. Overall, this work suggests that depth migration behavior in ancient nektonic mollusks could be elucidated by SIMS analysis across individual growth bands.