Movement,connectivity and population structure of the intertidal fish Lipophrys pholis as revealed by otolith oxygen and carbon stable isotopes

The shanny Lipophrys pholis is an intertidal fish commonly found in Portuguese coastal waters. Spawning takes place from early autumn to mid spring, after which demersal eggs hatch and larvae disperse along the coast. Two to three months later, young juveniles return to the tide pools to settle. However, information on fish movement, habitat connectivity and population structure is scarce for this species. One hundred and twenty early juveniles (16–35?mm) were collected in April 2014 from six rocky beaches along the western and south Portuguese coasts (Agudela, Cabo do Mundo, Boa Nova, Peniche, Sines and Olhos de Água). δ¹⁸O and δ¹³C were determined by isotope-ratio mass spectrometry. Data were analysed to determine whether isotopic signatures could be used to assess the degree of separation between individuals collected from different locations. Mean δ¹³C and δ¹⁸O values ranged from ?0.02‰ to 1.14‰ and ?7.77‰ to ?6.62‰, respectively. Both seawater temperature and salinity caused differences in otolith δ¹⁸O among the four main sampling areas. The variation among areas in δ¹³C was most likely related to slight differences in the diet, growth and metabolism of fish. The distinct isotopic signatures, at least for the northern and central areas, suggested low levels of connectivity across large spatial scales during the juvenile stage. Furthermore, similar isotopic signatures within the same area indicated some degree of larval oceanic retention at short spatial scales. This study suggests that stable isotope records in otoliths could provide information about the home residency, movements and habitat connectivity of intertidal fishes.     

Stable isotope analyses in otoliths of silver carp: a pilot study in identification of natal sources and stock differences

Silver carp, Hypophthalmichthys molitrix, is one of the four major fishes in China for fishing and aquaculture. The Yangtze River and associated waterbodies are important home to silver carp. In this study, we collected 135 otoliths of juvenile silver carp from the two rivers and the Poyang Lake, and analyzed for stable oxygen and carbon isotope ratios (δ¹⁸O and δ¹³C). The isotopic data and correlation of δ¹⁸O versus δ¹³C showed a clear separation and significant differences (p?<?0.001 for both δ¹³C and δ¹⁸O) between otoliths from the Ganjiang River and the Yangtze River at δ¹⁸O values around ?10‰. The Poyang Lake samples were overlapped with those of the Ganjiang River, but distinctly different from the Yangtze River samples. These isotopic signatures agree well with the previous genetic investigation results that there are marked distinctions between one population in the Ganjiang River and the other in the Yangtze River, and the Poyang Lake population belongs to the Ganjiang River rather than to the Yangtze River. Thus we concluded that stable isotope analyses of otoliths can be effectively used to study natal sources and stock differences of silver carp.     

Statistical analysis on otolith data of anadromous fishes

Stable oxygen and carbon isotope (δ¹⁸O and δ¹³C) analyses of otoliths are becoming increasingly common in fisheries science and management. However, little is known about the statistical properties of isotopic data and few attempts have been made to explore appropriate statistical methods that could be used for otolith data analysis. In this paper, we present a pilot study on δ¹⁸O and δ¹³C data from otoliths of two anadromous fish species, Atlantic salmon (Salmo salar) and Pacific sockeye salmon (Oncorhynchus nerka). The results indicated that the salmon otolith data were not normally distributed, so that linear discriminant function analysis and commonly-used statistical tests such as ANOVA and the t-test may not be appropriate. Using non-parametric k-sample nearest neighbor discriminant analysis, we were able to discriminate with high accuracy among five hatcheries for Atlantic salmon and the origins of wild and hatchery sockeye salmon. Analyses also indicated that the sample sizes required to estimate δ¹⁸O and δ¹³C means based on the different sources of variability (between group or within group) and precision levels (≤ ±5.0 %) were not large. These results and conclusions not only address the statistical considerations of isotopic data from otoliths, but also have practical importance for fisheries management as well.     

Aerial decay influence on the stable oxygen and carbon isotope ratios in tree ring cellulose

Sub-fossil wood is often affected by the decaying process that introduces uncertainties in the measurement of oxygen and carbon stable isotope composition in cellulose. Although the cellulose stable isotopes are widely used as climatic proxies, our understanding of processes controlling their behavior is very limited. We present here a comparative study of stable oxygen and carbon isotope ratios in tree ring cellulose in decayed and non-decayed wood samples of Swiss stone pine (Pinus cembra) trees. The intra-ring stable isotope variability (around the circumference of a single ring) was between 0.1 and 0.5‰ for δ¹⁸O values and between 0.5 and 1.6‰ for δ¹³C values for both decayed and non-decayed wood. Observed intra-tree δ¹⁸O variability is less than that reported in the literature (0.5–1.5‰), however, for δ¹³C it is larger than the reported values (0.7–1.2‰). The inter-tree variability for non-decayed wood ranges between 1.1 and 2.3‰ for δ¹⁸O values, and between 2 and 4.7‰ for δ¹³C values. The inter-tree differences for δ¹⁸O values are similar to those reported in the literature (1–2‰ for oxygen and 1–3‰ for carbon) but are larger for δ¹³C values. We have found that the differences for δ¹⁸O and δ¹³C values between decayed and non-decayed wood are smaller than the variation among different trees from the same site, suggesting that the decayed wood can be used for isotopic paleoclimate research.     

Elemental chemistry of left and right sagittal otoliths in a marine fish Hippoglossus stenolepis displaying cranial asymmetry

The hypothesis was tested that the sagittae of age 2 year Pacific halibut Hippoglossus stenolepis are interchangeable, by analysing whole‐otolith preparations for element‐to‐calcium ratios of 10 trace metals (⁷Li, ²⁵Mg, ⁵⁵Mn, ⁵⁶Fe, ⁶⁰Ni, ⁶³Cu, ⁶⁶Zn, ⁸⁸Sr, ¹³⁸Ba and ²⁰⁸Pb) and carbon and oxygen stable isotope ratios (δ¹³C and δ¹⁸O). After detrending for significant (α= 0·05) relationships between elemental concentration and otolith mass, significant (paired t‐tests, P < 0·01) asymmetry was detected in δ¹³C and δ¹⁸O, and ⁸⁸Sr:⁴⁸Ca. Right (smaller) sagittae exhibited higher δ¹³C and δ¹⁸O, and lower ⁸⁸Sr:⁴⁸Ca, than left sagittae. Significant (α= 0·05) left–right differences were not detected in the remained trace metals. Given that sagittae are the same size at hatch and diverge as H. stenolepis age, the larger otolith is presumably biased towards later‐accreted carbonate. Estuarine‐reared flatfish probably exhibit more pronounced dissimilarities than observed here, given greater environmental variability in such habitats relative to coastal halibut nurseries, and the importance of salinity and temperature in regulating elemental uptake.     

Spatial subdivision among assemblages of Spanish mackerel, Scomberomorus commerson (Pisces: Scombridae) across northern Australia: implications for fisheries management

Aim This study investigated the use of stable δ¹³C and δ¹⁸O isotopes in the sagittal otolith carbonate of narrow‐barred Spanish mackerel, Scomberomorus commerson, as indicators of population structure across Australia. Location Samples were collected from 25 locations extending from the lower west coast of Western Australia (30°), across northern Australian waters, and to the east coast of Australia (18°) covering a coastline length of approximately 9500 km, including samples from Indonesia. Methods The stable δ¹³C and δ¹⁸O isotopes in the sagittal otolith carbonate of S. commerson were analysed using standard mass spectrometric techniques. The isotope ratios across northern Australian subregions were subjected to an agglomerative hierarchical cluster analysis to define subregions. Isotope ratios within each of the subregions were compared to assess population structure across Australia. Results Cluster analysis separated samples into four subregions: central Western Australia, north Western Australia, northern Australia and the Gulf of Carpentaria and eastern Australia. Isotope signatures for fish from a number of sampling sites from across Australia and Indonesia were significantly different, indicating population separation. No significant differences were found in otolith isotope ratios between sampling times (no temporal variation). Main conclusions Significant differences in the isotopic signatures of S. commerson demonstrate that there is unlikely to be any substantial movement of fish among these spatially discrete adult assemblages. The lack of temporal variation among otolith isotope ratios indicates that S. commerson populations do not undergo longshore spatial shifts in distribution during their life history. The temporal persistence of spatially explicit stable isotopic signatures indicates that, at these spatial scales, the population units sampled comprise functionally distinct management units or separate ‘stocks’ for many of the purposes of fisheries management. The spatial subdivision evident among populations of S. commerson across northern and western Australia indicates that it may be advantageous to consider S. commerson population dynamics and fisheries management from a metapopulation perspective (at least at the regional level).     

Segregation of SE Pacific and SW Atlantic southern blue whiting stocks: integrating evidence from complementary otolith microchemistry and parasite assemblage approaches

Southern blue whiting Micromesistius australis support one of the largest industrial fisheries in South America. Two main spawning/nursery grounds are known: one in the SW Atlantic Ocean (SWA), southwest from the Falkland (Malvinas) Islands; and other in the SE Pacific Ocean (SEP), south from the Taitao Peninsula. Juveniles originating from both grounds are believed to mix during migration and/or in feeding areas in the Scotia Sea. Previous efforts to distinguish stocks in this area have yielded contradictory results between genetics and otolith microchemical analyses. In the present work we revisited the null hypothesis of a single stock occurring in the broader SWA-SEP region by comparing and integrating results from different approaches: trace metals (Ca, Sr, Ba, Mg, Mn) and stable isotopes (δ¹³C, δ¹⁸O) in otolith cores, and parasite assemblage compositions in adults from SWA and SEP spawning grounds. We found significant differences in Sr:Ca, δ¹³C and δ¹⁸O mean ratios between spawning grounds. The best trace element discriminant model classified 83% of the samples. Each stable isotope discriminated >90% of the samples, while combining them into a bivariate discriminant model led to 100% classification success. Higher δ¹⁸O levels in the SWA samples agreed with lower mean temperature and higher ambient δ¹⁸O levels in that area. Parasite assemblage compositions also showed significant differences between grounds regarding the prevalence of Chondracanthus, Contracaecum, Hepatoxylon and Grillotia and the abundance of Diclidophora, Anisakis, Contracaecum, Hysterothylacium and Hepatoxylon. Parasite-based discriminant models supported 90–100% correct assignment of samples to capture location. Although preliminary due to limited sampling coverage, our results support the existence of at least two ecologically distinct sub-populations of southern blue whiting in South America. The joint use of otolith microchemistry and parasitological techniques showed to be a promising way to test hypotheses concerning ecological stocks in marine fishes.     

Stable carbon isotope ratio of tree leaves, boles and fine litter in a tropical forest in Rondônia, Brazil

Leaves of 208 trees were collected for isotopic analysis together with wood from 36 tree boles and 18 samples of fine litter from a terra-firme forest located at Samuel Ecological Reserve, Rondônia State, in the southwestern Amazon region. The range of δ¹³C values in leaves was from ?28 to ?36‰, with an average (±1 SD) of ?32.1?±?1.5‰, which was more negative than the δ¹³C values of bole samples (?28.4?±?2.0‰) and fine litter (?28.7?±?2.0‰). These values are within the range found for tropical and subtropical forests. Pooling the δ¹³C values for leaf samples from trees of the same height gave averages which were positively correlated with plant height at a highly significant level, with a slope of 0.06 and an intercept of ?33.3‰ and a correlation coefficient r ²=0.70 (P<0.001).     

Kangaroo tooth enamel oxygen and carbon isotope variation on a latitudinal transect in southern Australia: implications for palaeoenvironmental reconstruction

Tooth enamel apatite carbonate carbon and oxygen isotope ratios of modern kangaroos (Macropus spp.) collected on a 900-km latitudinal transect spanning a C₃–C₄ transition zone were analysed to create a reference set for palaeoenvironmental reconstruction in southern Australia. The carbon isotope composition of enamel carbonate reflects the proportional intake of C₃ and C₄ vegetation, and its oxygen isotope composition reflects that of ingested water. Tooth enamel forms incrementally, recording dietary and environmental changes during mineralisation. Analyses show only weak correlations between climate records and latitudinal changes in δ¹³C and δ¹⁸O. No species achieved the δ¹³C values (~?1.0 ‰) expected for 100 % C₄ grazing diets; kangaroos at low latitudes that are classified as feeding primarily on C₄ grasses (grazers) have δ¹³C of up to ?3.5 ‰. In these areas, δ¹³C below ?12 ‰ suggests a 100 % C₃ grass and/or leafy plant (browse) diet while animals from higher latitude have lower δ¹³C. Animals from semi-arid areas have δ¹⁸O of 34–40 ‰, while grazers from temperate areas have lower values (~28–30 ‰). Three patterns with implications for palaeoenvironmental reconstruction emerge: (1) all species in semi-arid areas regularly browse to supplement limited grass resources; (2) all species within an environmental zone have similar carbon and oxygen isotope compositions, meaning data from different kangaroo species can be pooled for palaeoenvironmental investigations; (3) relatively small regional environmental differences can be distinguished when δ¹³C and δ¹⁸O data are used together. These data demonstrate that diet–isotope and climate–isotope relationships should be evaluated in modern ecosystems before application to the regional fossil record.     

Stable carbon and oxygen isotopes in human tooth enamel: Identifying breastfeeding and weaning in prehistory. Am. J. Phys. Anthropol. 106: 1–18.

ERRATUM: Wright LE and Schwarcz HP (1998) Stable Carbon and Oxygen Isotopes in Human Tooth Enamel: Identifying Breastfeeding and Weaning in Prehistory. Am. J. Phys. Anthropol. 106: 1–18. Isotopic ratios were incorrectly printed as percentages (%) rather than units permil (‰). Wherever “breast feeding” and “breast fed” occur, the words should be combined into “breastfeeding” and “breastfed” respectively. The correct information on isotopic ratios is the following: p. 1, Abstract: all % signs should be “‰”; p. 2, column two, last line: “… δ¹³C values¹, have been …”; p. 2, Footnote 1 should read: “Isotope ratios of carbon and oxygen are expressed in δ notation as follows, δ = [(R_sample/R_standard) − 1] × 1000, where R = ¹³C/¹²C for δ¹³C, and R = ¹⁸O/¹⁶O for δ¹⁸O, and are in units permil, ‰.”; p. 3, column two: all % signs should be “‰”, except for the 23rd line from the bottom, which reads: “… provided 95% of water intake by all infants …”; p. 5: all % signs should be “‰”; p. 6, column one: 8th and 9th line from bottom should be “… mean deviations were 0.029‰ for δ¹³C and 0.024‰ for δ¹⁸O …”; p. 6, column one: 2nd line from bottom should be “… only 0.208‰ for δ¹³C and only 0.091‰ for δ¹⁸O …”; p. 6, column two: top line: “… of 0.5‰ in δ¹³C and 0.2‰ in δ¹⁸O …”; p. 8, 9 and 10: all % signs should be “‰”; p. 11, column two: 7th line from top: “… the lipids are 4-6‰ lighter …”; p. 12, 13 and 14: all % signs should be “‰.”     

基于稳定同位素技术的增殖放流牙鲆群体鉴别

牙鲆是我国黄渤海重要的增殖放流鱼类,野生群体和放流群体的鉴别是评估牙鲆增殖效果的前提.为了研究稳定同位素技术在增殖放流牙鲆群体鉴别中的应用,本研究以秦皇岛近海增殖放流区捕捞牙鲆幼鱼为对象,先使用项目组前期开发的形态学和分子标记相结合的方法区分野生群体和放流群体,再分别测定肌肉碳、氮稳定同位素值和耳石(全耳石和耳石核心区...     

Stable isotopic (δ13C and δ18O) signatures of biogenic calcretes marking discontinuity surfaces: a case study from Upper Cretaceous carbonates of central Dalmatia and eastern Istria,Croatia

Biogenic calcretes associated with a regional Cretaceous to Paleogene subaerial unconformity and an intraformational composite (polygenic) surface in Upper Cretaceous intra-platform peritidal successions in central Dalmatia and eastern Istria, Croatia (Adriatic-Dinaridic Carbonate Platform), were analyzed for their δ¹³C and δ¹⁸O signatures in order to provide insight into the conditions of subaerial exposure and calcrete development. The distinctly negative δ¹³C signatures of biogenic calcretes marking the regional subaerial unconformity differ considerably from the δ¹³C values of the host marine limestones. This indicates carbon isotope exchange of primary marine CaCO₃ with CO₂ released by root and rhizomicrobial respiration and subsequent precipitation of pedogenic calcrete. The range of δ¹³C (from ?13.1 to ?8.2 ‰ Vienna PeeDee Belemnite standard, VPDB) and δ¹⁸O (from ?10.1 to ?6.1 ‰ VPDB) values of calcretes are similar to those reported from calcretes elsewhere, and the δ¹³C values of biogenic calcretes with typical Microcodium aggregates (?13.1 to ?12.3 ‰ VPDB) at the ?ibenik locality are very close to, or at the lower limit of, values for soil carbonates formed in isotopic equilibrium with soil CO₂. These values are expected for authigenic pedogenic carbonates formed under the influence of C₃ plant communities, without influence from heavier carbon from pre-existing carbonate and lack of input of atmospheric CO₂. Such low δ¹³C values support the interpretation of Microcodium aggregates as being precipitated under a direct biological control within the soil, although the relationship between formation mechanisms and stable isotope signatures of Microcodium needs further investigation. The δ¹³C values (?4.4 to ?3.6 ‰ VPDB) of rhizogenic calcretes formed inside firmground Thalassinoides burrows of the composite surface at the ?ibenik locality are more negative than the δ¹³C values of the host marine limestones, which confirms that the composite surface went through a phase of meteoric pedo(dia)genesis. However, the overall δ¹³C values of calcretes are less negative than expected, which might reflect contamination from associated primary marine carbonate. This study represents the first detailed stable isotope investigation of calcretes from carbonate successions of the External Dinarides, and the results may be applied to discontinuities present in other shallow-water carbonate rock successions.     

INVESTIGATING TROPHIC RELATIONSHIPS OF PINNIPEDS IN ALASKA AND WASHINGTON USING STABLE ISOTOPE RATIOS OF NITROGEN AND CARBON

We measured stable-nitrogen (δ¹⁵N) and stable-carbon (δ¹³C) isotope ratios in muscle and hair from 7 northern fur seals (Callorhinus ursinus) from the Pribilof Islands, Alaska, and 27 Steller sea lions (Eumetopias jubatus), and 14 harbor seals (Phoca vitulina) from the Gulf of Alaska and coast of Washington State, in order to contrast dietary information derived from isotopic vs. available conventional dietary studies. Stable-nitrogen-isotope analysis of muscle revealed that harbor seals were enriched over sea lions (mean δ¹⁵N = 18.6‰vs. 17.5‰) which were in turn enriched over northern fur seals (mean δ¹⁵N = 16.6‰). Trophic segregation among these species likely results primarily from differential reliance on herring (Clupea harengus), Atka mackerel (Pleurogrammus monopterygius), and large vs. small walleye pollock (Theregra chalcogramma). According to their δ¹⁵N values, adult male Steller sea lions showed a higher trophic position than adult females (mean δ¹⁵N: 18.0‰vs. 17.2‰), whereas adult female northern fur seals were trophically higher than juvenile male fur seals (mean δ¹⁵N: 16.5‰vs. 15.0‰). Each of these observed differences likely resulted from differential reliance on squid or differences in the size range of pollock consumed. Three northern fur seal pups showed higher δ¹⁵N enrichment over adults (mean 17.7‰vs. 15.8‰) due to their reliance on their mother's milk. Stable-carbon isotope measurements of hair revealed a cline toward more negative values with latitude. Segregation in hair δ¹³C between Steller sea lions and harbor seals off the coast of Washington (mean δ¹³C: ?13.6‰vs.?15.0‰) reflected the greater association of harbor seals with freshwater input from the Columbia River. Our study demonstrates the utility of the stable isotope approach to augment conventional dietary analyses of pinnipeds and other marine mammals.     

Identification of nitrogen sources and transformations within karst springs using isotope tracers of nitrogen

Isotope analyses of nitrate and algae were used to gain better understanding of sources of nitrate to Florida’s karst springs and processes affecting nitrate in the Floridan aquifer at multiple scales. In wet years, δ¹⁵N and δ¹⁸O of nitrate ranged from +3 to +9‰ in headwater springs in north Florida, indicating nitrification of soil ammonium as the dominant source. With below normal rainfall, the δ¹⁵N and δ¹⁸O of nitrate were higher in almost all springs (reaching +20.2 and +15.3‰, respectively) and were negatively correlated with dissolved oxygen. In springs with values of δ¹⁵N-NO₃ and δ¹⁸O-NO₃ greater than +10‰, nitrate concentrations declined 40–50% in dry years and variations in the δ¹⁵N and δ¹⁸O of nitrate were consistent with the effects of denitrification. Modeling of the aquifer as a closed system yielded in situ fractionation caused by denitrification of 9 and 18‰ for Δ¹⁸O and Δ¹⁵N, respectively. We observed no strong evidence for local sources of nitrate along spring runs; concentrations declined downstream (0.42–3.3?μmol-NO₃ L^?1 per km) and the isotopic dynamics of algae and nitrate indicated a closed system. Correlation between the δ¹⁵N composition of nitrate and algae was observed at regional and spring-run scales, but the relationship was complicated by varying isotopic fractionation factors associated with nitrate uptake (Δ ranged from 2 to 13‰). Our study demonstrates that nitrate inputs to Florida’s springs are derived predominantly from non-point sources and that denitrification is detectable in aquifer waters with relatively long residence time (i.e., matrix flow).     

Stock structure of Grey Mackerel, Scomberomorus semifasciatus (Pisces: Scombridae) across northern Australia, based on otolith stable isotope chemistry

The stable isotopes of δ¹⁸O and δ¹³C in sagittal otolith carbonates were used to determine the stock structure of Grey Mackerel, Scomberomorus semifasciatus. Otoliths were collected from Grey Mackerel at ten locations representing much of their distributional and fisheries range across northern Australia from 2005 to 2007. Across this broad range (～ 6500 km), fish from four broad locations—Western Australia (S1), Northern Territory and Gulf of Carpentaria (S2, S3, S4, S5, S6, S7), Queensland east coast mid and north sites (S8, S9) and Queensland east coast south site (S10)—had stable isotope values that were significantly different indicating stock separation. Otolith stable isotopes differed more between locations than among years within a location, indicating temporal stability across years. The spatial separation of these populations indicates a complex stock structure across northern Australia. Stocks of S. semifasciatus appear to be associated with large coastal embayments. These results indicate that optimal fisheries management may require a review of the current spatial arrangements, particularly in relation to the evidence of shared stocks in the Gulf of Carpentaria. Furthermore, as the population of S. semifasciatus in Western Australia exhibited high spatial separation from those at all the other locations examined, further research activities should focus on investigating additional locations within Western Australia for an enhanced determination of stock delineation.     

Past climate changes and ecophysiological responses recorded in the isotope ratios of saguaro cactus spines

The stable isotope composition of spines produced serially from the apex of columnar cacti has the potential to be used as a record of changes in climate and physiology. To investigate this potential, we measured the δ¹⁸O, δ¹³C and F¹⁴C values of spines from a long-lived columnar cactus, saguaro (Carnegiea gigantea). To determine plant age, we collected spines at 11 different heights along one rib from the stem apex (3.77 m height) to the base of a naturally occurring saguaro. Fractions of modern carbon (F¹⁴C) ranged from 0.9679 to 1.5537, which is consistent with ages between 1950 and 2004. We observed a very strong positive correlation (r = 0.997) between the F¹⁴C age of spines and the age of spines determined from direct and repeated height measurements taken on this individual over the past 37 years. A series of 96 spines collected from this individual had δ¹⁸O values ranging from 38‰ to 50‰ [Vienna standard mean ocean water (VSMOW)] and δ¹³C values from ?11.5‰ to ?8.5‰ [Vienna Peedee belemnite (VPDB)]. The δ¹⁸O and δ¹³C values of spines were positively correlated (r = 0.45, P < 0.0001) and showed near-annual oscillations over the ～15-year record. This pattern suggests that seasonal periods of reduced evaporative demand or greater precipitation input may correspond to increased daytime CO₂ uptake. The lowest δ¹⁸O and δ¹³C values of spines observed occurred during the 1983 and 1993 El Niño years, suggesting that the stable isotope composition recorded in spine tissue may serve as a proxy for these climate events. We compared empirical models and data from potted experimental cacti to validate these observations and test our hypotheses. The isotopic records presented here are the first ever reported from a chronosequence of cactus spines and demonstrate that tissues of columnar cacti, and potentially other long-lived succulents, may contain a record of past physiological and climatic variation.     

Non-climatic variations in the oxygen isotopic compositions of plants

The ¹⁸O content of leaf water strongly influences the ¹⁸O contents of atmospheric CO₂ and O₂. The ¹⁸O signatures of these atmospheric gases, in turn, emerge as important indicators of large-scale gas exchange processes. Better understanding of the factors that influence the isotopic composition of leaf water is still required, however, for the quantitative utilization of these tracers. The ¹⁸O enrichment of leaf water relative to local meteoric water, is known to reflect climatic conditions. Less is known about the extent variations in the ¹⁸O content of leaf water are influenced by nonclimatic, species-specific characteristics. In a collection of 90 plant species from all continents grown under the same climatic conditions in the Jerusalem Botanical Garden we observed variations of about 9‰ in the δ¹⁸O values of stem water, δ_s, and of about 14‰ in the mid-day δ¹⁸O enrichment of bulk leaf water, δ_LW–δ_s. Differences between δ¹⁸O values predicted by a conventional evaporation model, δ_M, and δ_LW ranged between – 3.3‰ and + 11.8‰. The δ¹⁸O values of water in the chloroplasts (δ_ch) in leaves of 10 selected plants were estimated from on-line CO₂ discrimination measurements. Although much uncertainty is still involved in these estimates, the results indicated that δ_ch can significantly deviate from δ_M in species with high leaf peclet number. The δ¹⁸O values of bulk leaf water significantly correlated with δ¹⁸O values of leaf cellulose (directly) and with instantaneous water use efficiency (A/E, inversely). Differences in isotopic characteristics among conventionally defined vegetation types were not significant, except for conifers that significantly differed from shrubs in δ¹⁸O and δ¹³C values of cellulose and in their peclet numbers, and from deciduous woodland species in their δ¹⁸O and δ¹³C values of cellulose. The results indicated that predictions of the δ¹⁸O values of leaf water (δ_LW, δ_M and δ_ch) could be improved by considering plant species-specific characteristics.     

Microsampling of Fish Otoliths: A Comparison Between DM 2800 and Dremel in Stable Isotope Analysis

This paper describes and compares two microsampling methods, DM 2800 and Dremel, which were used in taking aragonite samples from otolith zones of cod, Gadus morhua, for stable isotope analysis. There were no significant differences between the two sampling methods both in carbon and oxygen isotope ratios (¹³C/¹²C, ¹⁸O/¹⁶O) and in annual and seasonal otolith zones. The possible finite effect with Dremel could be minimized or negligible by selecting otoliths of younger fishes. Thus, Dremel may be accepted as a convenient microsampling method in stable isotope analysis of otoliths.     

Stable isotopic composition of otoliths from tagged Pacific halibut, Hippoglossus stenolepis

Data from tagging studies and stable isotope ratio analyses (¹⁸O and ¹³C) in otoliths of tagged Pacific halibut, Hippoglossus stenolepis, provided unique information about halibut distribution and area migration. The ¹⁸O values of otoliths of individual halibut tagged in the Bering Sea and the Gulf of Alaska ranged from –0.5 to +1.0 VPDB (Vienna Peedee belemnite) in the first few years, but gradually increased to 2.0–2.5 VPDB when these tagged fish were recaptured as adults in waters off British Columbia. Similar isotopic variations were found in ¹³C. Comparison of isotopic composition from the age-1 halibut (i.e., aragonite samples taken from the first annulus of otoliths) and the adult (ages 8) indicated that the ocean conditions between the Bering Sea and the northeast Pacific were markedly different over the tagging period, but the area boundaries between the Gulf of Alaska and British Columbia were not clear. We concluded that stable isotopic records in otoliths of tagged Pacific halibut were informative and particularly useful for details of subsequent movement of halibut between release and recovery.     

The oxygen isotope composition of planktonic foraminifera from the Guaymas Basin,Gulf of California: Seasonal,annual, and interspecies variability

Sediment trap samples collected over a seven-year period (February 1991–October 1997) from Guaymas Basin in the Gulf of California were used to study the oxygen isotope composition of five species of planktonic foraminifera, Globigerinoides ruber (white), Globigerina bulloides, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia menardii. The δ¹⁸O data were analyzed for temporal and interspecies variability and were compared to local hydrography to evaluate the use of each species in reconstructing past oceanographic applications. The two surface dwelling species, G. ruber and G. bulloides displayed the lowest δ¹⁸O values (～ 0.0 to ? 5.0‰), while δ¹⁸O values for the thermocline dwelling N. dutertrei, P. obliquiloculata, and G. menardii were higher (～ 0.0 to ? 2.0‰). The δ¹⁸O of G. ruber most accurately records measured sea surface temperatures (SSTs) throughout the year. G. bulloides δ¹⁸O tracks SSTs during the winter–spring upwelling period but for the remainder of the year records slightly colder, subsurface temperatures. The difference between the δ¹⁸O of the surface dwelling species, G. ruber and G. bulloides, and that of the thermocline dwelling species, N. dutertrei, P. obliquiloculata, and G. menardii, was used to estimate the surface to thermocline temperature gradient. During the winter these δ¹⁸O differences are small (～ 0.50‰) reflecting a well-mixed water column. These interspecies δ¹⁸O differences increase during the summer (～ 1.90‰) in response to the strong thermal stratification that exists at this time of year.