δ13C Patterns Research Articles

Seasons of the ringed seal: pelagic open-water hyperphagy, benthic feeding over winter and spring fasting during molt

Context The ringed seal (Phoca hispida), a small phocid seal with a circumpolar Arctic distribution and a strong association with sea ice, occurs at the southern limit of its range in Hudson and James Bays: an area that experiences complete ice cover in winter and complete open water in summer. Because of the high seasonal variability in environmental conditions, it is expected that ringed seals experience seasonal changes in diet and foraging habitat, which will be reflected in body condition and biomarkers of stable isotopes and fatty acids. Aims The purpose of the present study was to investigate intra-annual variation in the feeding habits and body condition of the ringed seal. Methods Tissue samples and morphological measurements from south-eastern Hudson Bay ringed seals were obtained every month during the Inuit subsistence hunt from November 2009 to May 2011 (n = 192). Muscle samples were used for δ15N and δ13C stable isotope analysis, blubber was used for analysis of fatty acid composition, bodyweight and sculp weight were used to estimate percentage blubber, and lower right canines were used to determine age. Key results Fatty acid composition, δ15N, and δ13C varied significantly by season, suggesting seasonal changes in foraging habitat and diet. Variation in percentage blubber indicated that poorest body condition occurs following the molting and fasting period, followed by a gradual increase from late summer through fall, with the highest body condition occurring in time for freeze-up in December. Key conclusions Patterns of δ13C indicate pelagic feeding during the open-water season (August–December) when fat and energy stores are replenished, increased benthic foraging during the period of ice cover (January–May), followed by a period of fasting during the spring molt (June–July). Fatty acid composition suggested seasonal changes in diet that could include increased importance of pelagic fish in the fall during the period of positive energy balance. Implications The first continuous collection of ringed seal tissue samples provided a comprehensive seasonal pattern of biomarker composition, which is baseline data that have important applications for short-term management and ecology studies as well as long-term conservation and monitoring programs.

Nitrogen and carbon isotope variability in the green-algal lichen Xanthoria parietina and their implications on mycobiont-photobiont interactions.

Stable isotope patterns in lichens are known to vary largely, but effects of substrate on carbon and nitrogen stable isotope signatures of lichens were previously not investigated systematically. N and C contents and stable isotope (δ15N, δ13C) patterns have been measured in 92 lichen specimens of Xanthoria parietina from southern Bavaria growing on different substrates (bark and stone). Photobiont and mycobiont were isolated from selected populations and isotopically analyzed. Molecular investigations of the internal transcribed spacer of the nuclear ribosomal DNA (ITS nrDNA) region have been conducted on a subset of the specimens of X. parietina. Phylogenetic analysis showed no correlation between the symbionts X. parietina and Trebouxia decolorans and the substrate, isotope composition, or geographic origin. Instead specimens grown on organic substrate significantly differ in isotope values from those on minerogenic substrate. This study documents that the lichens growing on bark use additional or different N sources than the lichens growing on stone. δ15N variation of X. parietina apparently is controlled predominantly by the mass fraction of the mycobiont and its nitrogen isotope composition. In contrast with mycobionts, photobionts of X. parietina are much more 15N-depleted and show less isotopic variability than mycobionts, probably indicating a mycobiont-independent nitrogen acquisition by uptake of atmospheric ammonia.

Oxygen and carbon isotope patterns archived in shells of the aquatic gastropod Radix: Hydrologic and climatic signals across the Tibetan Plateau in sub-monthly resolution

The Tibetan Plateau (TP), including its surrounding mountain ranges, represents the largest store of ice outside the polar regions. It hosts numerous lakes as well as the head waters of major Asian rivers, on which billions of people depend, and it is particularly sensitive to climate change. The moisture transport to the TP is controlled by the Indian and Pacific monsoon and the Westerlies. Understanding the evolution of the interaction of these circulation systems requires studies on climate archives in different spatial and temporal contexts. The objective of this study is to learn more about the interannual variability of precipitation patterns across the TP and how different hydrologic systems react to different climatic factors.Aragonite shells of the aquatic gastropod Radix, which is widely distributed in the region, may represent suitable archives for inferring hydrologic and climatic signals in particularly high resolution. Therefore, sclerochronological studies of δ18O and δ13C ratios in Radix shells from seven lakes were conducted, each representing a different hydrologic and climatic setting, on a transect from the Pamirs across the TP.The shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east. δ18O values of shells from lakes on the eastern and central TP (Donggi Cona, Yamdrok Yumco, Tarab Co) mirror monsoon signals, indicated by more negative values and higher variabilities compared to the more western lakes (Karakul, Bangong/Nyak, Manasarovar). In Yadang Co, located on the central southern TP, the monsoon rains did not reach the lake in the sampling year, although it is located in a region which is usually affected by monsoon circulation. The δ18O values are used to differentiate the annual hydrological cycle into ice cover period, melt water period, precipitation period and evaporation period. δ13C compositions in the shells particularly depend on specific habitats, which vary in biological productivity and in carbon sources. δ18O and δ13C patterns show a positive covariance in shells originating from large closed basins. The results show that Radix shells mirror general climatic differences between the seven lake regions. These differences reflect both regional and local climate signals in sub-seasonal resolution, without noticeable dependence on the particular lake system.

Relationships between altitudinal gradient and plant carbon isotope composition of grassland communities on the Qinghai-Tibet Plateau, China

Foliar and root carbon isotope composition (δ13C) of grassland communities on the Qinghai-Tibet Plateau, China, was obtained by the biomass weighting method and direct measurement. We investigated the characteristics and altitudinal patterns of foliar and root δ13C and determined which environmental factors influenced foliar δ13C most. Foliar δ13C of alpine steppe was significantly higher than that of alpine meadow and temperate steppe. For alpine meadow, root δ13C was significantly higher than of foliar δ13C. Foliar δ13C increased with altitude at an average rate of 0.60‰ km−1 for the whole grassland ecosystem. This rate was lower than that at species level. However, there were no significant relationships between root δ13C and altitude. Atmospheric pressure was a more important factor than temperature and precipitation in its influence on the altitudinal pattern of foliar δ13C at the community level.

Diet-dependent δ13C and δ15N fractionation among sea urchin Lytechinus variegatus tissues: implications for food web models

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 462:175-190 (2012) - DOI: https://doi.org/10.3354/meps09786 Diet-dependent δ13C and δ15N fractionation among sea urchin Lytechinus variegatus tissues: implications for food web models Patricia Prado1,2,*, Ruth H. Carmichael3,4, Stephen A. Watts5, Just Cebrian3,4, Kenneth L. Heck Jr.3,4 1Institut de Recerca i Tecnología Agroalimentàries (IRTA), Aquatic Ecosystems, Ctra Poble Nou km 5.5, 43540 Sant Carles de la Ràpita, Tarragona, Spain 2Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA 3Dauphin Island Sea Lab, 101 Bienville Boulevard, Dauphin Island, Alabama 36528, USA 4Department of Marine Sciences, University of South Alabama, LSCB 25, Mobile, Alabama 36688, USA 5Department of Biology, University of Alabama at Birmingham, University Station, Birmingham, Alabama 35294-1170, USA *Email: patricia.prado@irta.cat ABSTRACT: Consumer-diet discrimination factors (Δ15N and Δ13C) are often applied without corroboration from laboratory experiments. Deviations in Δ15N and Δ13C that may occur from different diet types were quantified by raising 120 sea urchins Lytechinus variegatus in laboratory tanks on 3 different diets: seagrass Thalassia testudinum, red foliose macroalgae (Grauteloupia sp. and Palmaria palmata) and a mixed diet specifically formulated for L. variegatus. Patterns of δ13C and δ15N and resulting fractionation factors were then determined in muscle, gonad, gut, test organic matrix and whole individuals. Tissue δ13C values showed a strong positive association with δ13C of diets and estimates of absorption efficiency (R2 = 0.81). The seagrass diet consistently resulted in negative Δ13C values in all tissues (from −0.86‰ in muscle to −1.63‰ in gonad) and whole individuals (−1.19‰), whereas macroalgal and formulated diets showed positive values (0.11 and 0.19‰, respectively). Only individuals on the formulated diet clearly reached isotopic equilibrium for δ13C, suggesting that other lower quality diets may have resulted in more continuous reallocation of internal resources. δ15N values increased as the nitrogen content of these diets decreased (3.18, 1.21 and 0.82‰ for seagrass, macroalgae and formulated diets, respectively). Overall differences in the biochemical composition of diets and a robust relationship between δ13C and δ15N signatures suggest that protein quantity and quality could be central in driving isotope fractionation. The influence of macrophyte material type in the diet can be stronger than that of trophic level for both δ13C and δ15N, so further compound-specific isotope analyses are necessary to determine reliable values of Δ13C and Δ15N for ecological applications. KEY WORDS: Seagrass · Macroalgae · Omnivory · Diet quality · Absorption efficiency Full text in pdf format PreviousNextCite this article as: Prado P, Carmichael RH, Watts SA, Cebrian J, Heck KL Jr (2012) Diet-dependent δ13C and δ15N fractionation among sea urchin Lytechinus variegatus tissues: implications for food web models. Mar Ecol Prog Ser 462:175-190. https://doi.org/10.3354/meps09786 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 462. Online publication date: August 21, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Tracking large‐scale latitudinal patterns of δ13C and δ15N along the E Pacific using epi‐mesopelagic squid as indicators

Because consumers integrate components of their habitat through diet over time and space, stable isotope ratios from animal tissues can track spatial variation in baseline values across marine systems. To understand large‐scale geographic patterns in the eastern Pacific ocean, muscle δ13C and δ15N from epi‐mesopelagic squid (n = 404) were collected from 39° S to 53° N and analyzed in relation to hemisphere, latitude, geographic area and current systems. Geographic patterns were controlled for effects of secondary factors such as squid size, species (Dosidicus gigas and Sthenoteuthis oualaniensis), tissue and year of collection. Joint latitudinal variation of δ13C and δ15N was also described for the first time. Both δ13C and δ15N, as well as the standardized difference between them, had distinct patterns by latitude. δ13C was the highest at 22°S and decreased north and south of that latitude, with lower values at mid‐northern latitudes than near the equator. δ15N had the lowest values near the equator and gradually increased towards mid‐latitudes. The standardized difference between δ13C and δ15N was highest (C was higher relative to N) near the equator and declined to mid‐latitudes. Overall, the δ13C and δ15N geographic patterns agreed with previous studies for δ15N from surface NO3−, but not for δ13C in plankton, POM and squid. We suggest that the biochemical processes for carbon and nitrogen are spatially more variable than what has previously been reported because squid isotope ratios varied also among current systems and geographic areas. These geographic patterns in δ13C and δ15N, indicated by consumers such as cephalopods, could improve our understanding about the interaction between the carbon and nitrogen cycle and the heterogeneity in biochemical cycling processes in marine systems.

Authigenic carbonates from active methane seeps offshore southwest Africa

The southwest African continental margin is well known for occurrences of active methane-rich fluid seeps associated with seafloor pockmarks at water depths ranging broadly from the shelf to the deep basins, as well as with high gas flares in the water column, gas hydrate accumulations, diagenetic carbonate crusts and highly diverse benthic faunal communities. During the M76/3a expedition of R/V METEOR in 2008, gravity cores recovered abundant authigenic carbonate concretions from three known pockmark sites—Hydrate Hole, Worm Hole, the Regab pockmark—and two sites newly discovered during that cruise, the so-called Deep Hole and Baboon Cluster. The carbonate concretions were commonly associated with seep-benthic macrofauna and occurred within sediments bearing shallow gas hydrates. This study presents selected results from a comprehensive analysis of the mineralogy and isotope geochemistry of diagenetic carbonates sampled at these five pockmark sites. The oxygen isotope stratigraphy obtained from three cores of 2–5 m length indicates a maximum age of about 60,000–80,000 years for these sediments. The authigenic carbonates comprise mostly magnesian calcite and aragonite, associated occasionally with dolomite. Their very low carbon isotopic compositions (–61.0 < δ13C ‰ V-PDB < –40.1) suggest anaerobic oxidation of methane (AOM) as the main process controlling carbonate precipitation. The oxygen isotopic signatures (+2.4 < δ18O ‰ V-PDB < +6.2) lie within the range in equilibrium under present-day/interglacial to glacial conditions of bottom seawater; alternatively, the most positive δ18O values might reflect the contribution of 18O-rich water from gas hydrate decomposition. The frequent occurrence of diagenetic gypsum crystals suggests that reduced sulphur (hydrogen sulphide, pyrite) from sub-seafloor sediments has been oxidized by oxygenated bottom water. The acidity released during this process can potentially induce the dissolution of carbonate, thereby providing enough Ca2+ ions for pore solutions to reach gypsum saturation; this is thought to be promoted by the bio-irrigation and burrowing activity of benthic fauna. The δ18O–δ13C patterns identified in the authigenic carbonates are interpreted to reflect variations in the rate of AOM during the last glacial–interglacial cycle, in turn controlled by variably strong methane fluxes through the pockmarks. These results complement the conclusions of Kasten et al. in this special issue, based on authigenic barite trends at the Hydrate Hole and Worm Hole pockmarks which were interpreted to reflect spatiotemporal variations in AOM related to subsurface gas hydrate formation–decomposition.

A short overview on linking annual tree ring carbon isotopes to historical changes in atmospheric environment

Tree rings are datable archives of environmental changes such as atmospheric pollution as tree annual growth rings store information on the growth conditions in the year of specific ring formation. Particularly, the C isotope ratio (13C/12C, expressed as δ13C) is susceptible to atmospheric CO2 and other pollutants (SO2, NOx, O3, and acid rain). Because current increases in atmospheric CO2 concentration are due to 13C-depleted CO2 emission from soil organic carbon decomposition and fossil fuel combustion, annual rings of trees grown without other pollutants may show a decreasing δ13C pattern since the industrial revolution. Meanwhile, trees exposed to atmospheric pollution (e.g. in metropolitan or industrial areas) may show increases in δ13C during the exposure period as atmospheric pollutants tend to decrease C isotope discrimination via reduced stomatal conductance or enhanced carboxylation particularly at low levels of pollutants, leading to less negative δ13C. However, as tree ring δ13C is susceptible to several other factors that affect gas exchange, supplementary data on atmospheric pollution, climate, and soil resources should be taken into consideration for more reliable interpretation of δ13C in relation to atmospheric environment changes.

Niche flexibility and trout–galaxiid co-occurrence in a hydrologically diverse riverine landscape

Non-native trout (Oncorhynchus mykiss, Salmo trutta) invasions have been implicated in the decline of native galaxiid fishes throughout temperate Southern Hemisphere freshwaters. As many Galaxias fishes are endangered, knowledge of factors facilitating localised co-occurrence of native and introduced species is needed for both conservation and management. While recent research demonstrates a role for flow-related mediation of trout effects on galaxiids, the mechanism(s) underlying such phenomena remain unclear. Accordingly, we assessed the interplay between environmental conditions and trophic niches for both species across a gradient of co-occurrence and hydrology. In particular, we quantified the trophic position (TP), energy sourcing patterns, and niche breadth based on the abundance of naturally occurring stable isotopes (15N and 13C) within muscle tissues for trout and galaxiids in replicate food webs from streams varying widely in size and disturbance regime. We found that both species held similar trophic positions, but TP varied considerably across individuals and sites due to combined effects of body size and hydrological disturbance. Further, patterns in δ13C revealed an effect of disturbance on the relative reliance by fish on a key prey taxon, and a ca. 1 ‰ shift in δ13C by galaxiids in the presence of trout. Lastly, isotope-based measures of niche width, which were positively correlated with coarse dietary measures of niche width, were similar, albeit variable, for all groups. Galaxiid niche width co-varied negatively with relative trout abundance, whereas that for trout did so with stream size. Altogether, our findings demonstrate that both the presence of trout and environmental conditions act in concert to influence where galaxiids are positioned within stream food webs. Perhaps more importantly, they suggest that flexible niches may enable galaxiids to persist in the presence of a species that might otherwise cause their local extinction.

Density fractionation and 13C reveal changes in soil carbon following woody encroachment in a desert ecosystem

Woody encroachment has dramatically changed land cover patterns in arid and semiarid systems (drylands) worldwide over the past 150 years. This change is known to influence bulk soil carbon (C) pools, but the implications for dynamics and stability of these pools are not well understood. Working in a Chihuahuan Desert C4 grassland encroached by C3 creosote bush (Larrea tridentata), we used two density fractionation techniques (2 and 7 pool density fractionations) and isotopic analysis to quantify changes in C pools and dynamics among vegetation microsites typical of an encroachment scenario (remnant intact grassland, shrub subcanopies, and in shrub intercanopy spaces within a shrub-encroached area). The C concentration of bulk soils varied with microsite, with almost twice the C in shrub subcanopies as in intercanopy spaces or remnant grasslands. Estimated SOC accumulation rates from Larrea encroachment (4.79 g C m−2 year−1 under canopies and 1.75 g C m−2 year−1 when intercanopy losses were taken into account) were lower than reported for higher productivity Prosopis systems, but still represent a potentially large regional C sink. The composition of soil C varied among microsites, with the shrub subcanopy C composed of proportionally more light fraction C (<1.85 g cm−3) and C that was soluble in sodium polytungstate. Grassland soils contained very little carbonate C compared to shrub subcanopies or shrub intercanopy spaces. Stable isotope analyses indicate that inputs from C3 shrubs were incorporated into all density fractions, even in heavy fractions in which shrub inputs did not change overall C concentration. The seven density fractionation yielded unexpected δ13C patterns, where the two heaviest fractions were strongly depleted in 13C, indicating strong fractionation following organic matter inputs. These results suggest that the utility of isotope mixing models for determining input sources may be limited in systems with similar fractionation patterns. We propose a five pool model for dryland soil C that includes a relatively dynamic light fraction, aggregate and heavy fractions that are stable in size but that reflect dynamic inputs and outputs, a potentially large and seasonally dynamic pool of soluble C, and a large pool of carbonate C. Combined, these results suggest that dryland soil C pools may be more dynamic than previously recognized.

Seasonal increase of methane in sediment decreases δ13C of larval chironomids in a eutrophic shallow lake

Recent studies have shown that larval chironomids assimilate 13C-depleted carbon derived from biogenic methane by feeding on methane-oxidizing bacteria (MOB). The dietary contribution of MOB is known to be maximized in the autumn overturn period or winter in eutrophic dimictic lakes due to the increase of MOB biomass following the supply of oxygenated water, but in polymictic lakes, such seasonal variability has not been revealed. We investigated the seasonal patterns of larval δ13C and methane concentrations in the sediment of a eutrophic polymictic lake, Izunuma, Japan. Larval δ13C decreased in late summer and autumn. Methane concentrations above a 6 cm depth peaked in late summer or autumn, while those in the 10–11- and 20–21-cm layers peaked in October. Negative correlations between methane concentrations in the 5–6/10–11-cm layers and larval δ13C were found. This suggests that an increase in the supply of methane stimulated the activity of MOB in a polymictic lake, where water above the lake bottom rarely became anoxic because of frequent overturn, thus increasing the dietary contribution of MOB to larval chironomids.

Spatial variation of soil δ13C and its relation to carbon input and soil texture in a subtropical lowland woodland

Spatial patterns of soil δ13C were quantified in a subtropical C3 woodland in the Rio Grande Plains of southern Texas, USA that developed during the past 100 yrs on a lowland site that was once C4 grassland. A 50 × 30 m plot and two transects were established, and soil cores (0–15 cm, n = 207) were collected, spatially referenced, and analyzed for δ13C, soil organic carbon (SOC), and soil particle size distribution. Cross-variogram analysis indicated that SOC remaining from the past C4 grassland community co-varied with soil texture over a distance of 23.7 m. In contrast, newer SOC derived from C3 woody plants was spatially correlated with root biomass within a range of 7.1 m. Although mesquite trees initiate grassland-to-woodland succession and create well-defined islands of soil modification in adjoining upland areas at this site, direct gradient and proximity analyses accounting for the number, size, and distance of mesquite plants in the vicinity of soil sample points failed to reveal any relationship between mesquite tree abundance and soil properties. Variogram analysis further indicated soil δ13C, texture and organic carbon content were spatially autocorrelated over distances (ranges = 15.6, 16.2 and 18.7 m, respectively) far greater than that of individual tree canopy diameters in these lowland communities. Cross-variogram analysis also revealed that δ13C – SOC and δ13C-texture relationships were spatially structured at distances much greater than that of mesquite canopies (range = 17.6 and 16.5 m, respectively). These results suggest fundamental differences in the functional nature and consequences of shrub encroachment between upland and lowland landscapes and challenge us to identify the earth system processes and ecosystem structures that are driving carbon cycling at these contrasting scales. Improvements in our understanding how controls over soil carbon cycling change with spatial scale will enhance our ability to design vegetation and soil sampling schemes; and to more effectively use soil δ13C as a tool to infer vegetation and soil organic carbon dynamics in ecosystems where C3–C4 transitions and changes in structure and function are occurring.

A model‐data comparison of δ13C in the glacial Atlantic Ocean

We compare a compilation of 220 sediment core δ13C data from the glacial Atlantic Ocean with three‐dimensional ocean circulation simulations including a marine carbon cycle model. The carbon cycle model employs circulation fields which were derived from previous climate simulations. All sediment data have been thoroughly quality controlled, focusing on epibenthic foraminiferal species (such as Cibicidoides wuellerstorfi or Planulina ariminensis) to improve the comparability of model and sediment core carbon isotopes. The model captures the general δ13C pattern indicated by present‐day water column data and Late Holocene sediment cores but underestimates intermediate and deep water values in the South Atlantic. The best agreement with glacial reconstructions is obtained for a model scenario with an altered freshwater balance in the Southern Ocean that mimics enhanced northward sea ice export and melting away from the zone of sea ice production. This results in a shoaled and weakened North Atlantic Deep Water flow and intensified Antarctic Bottom Water export, hence confirming previous reconstructions from paleoproxy records. Moreover, the modeled abyssal ocean is very cold and very saline, which is in line with other proxy data evidence.

Tracking Collembola feeding strategies by the natural 13C signal of fatty acids in an arable soil with different fertilizer regimes

Abstract Compound specific stable isotope analysis (13C/12C ratio of fatty acids) was used to assess the allocation of plant carbon in soil microbiota, and to identify the trophic links to microbial grazers in an arable field with long-term mineral and organic fertilizer amendments. The feeding strategy of two dominant Collembola species, epedaphic Isotoma viridis and euedaphic Willemia anophthalma was determined. The investigation was conducted following a shift to amaranth, a C4 plant, after 27 years of continuous C3 crop rotation. The influence of new C4 plant carbon was observed in microbial phospholipids (PLFAs) with higher δ13C recorded in C4 amaranth than in C3 clover soils. The strongest enrichment occurred in the fungal PLFA 18:2ω6,9c and bacterial PLFA 18:1ω9t with 11.2‰ and 6.6‰, respectively. However, other bacterial PLFAs showed no isotopic change, suggesting that the microbial community simultaneously utilized “new” and “old” plant carbon. The δ13C of Collembola fatty acids displayed species specific lipid pattern, which was affected by crop type, but not fertilizer amendments. Isotopic separation of Collembola lipids from amaranth and clover plots was more distinct in I. viridis than W. anophthalma. With up to 18‰, the enrichment in Collembola lipids was stronger than in microbial PLFAs, pointing to a distinct incorporation of carbon resources originating from the actual plant residues. The δ13C pattern in I. viridis indicated trophic links with bacteria, saprotrophic fungi and plant tissues, while saprotrophic fungi and plant tissues were accountable for the patterns observed in W. anophthalma.

Stable carbon and nitrogen isotope composition of co-existing herbivorous zooplankton species in an oligo-dystrophic lake (Shirakoma-ike, Japan)

We studied carbon and nitrogen stable isotopes in particulate organic material and zooplankton in an oligotrophic humic lake, Lake Shirakoma-ike (Japan). The phytoplankton density was low and the zooplankton community was dominated by two species: a cladoceran (Daphnia longispina) and a copepod (Acanthodiaptomus pacificus). Though the two species have similar body size and shared same phytoplankton food sources of low diversity, they showed significant differences in isotope compositions; δ13C of D. longispina ranged from −30.9 to −28.2‰ and δ13C of A. pacificus ranged from −37.0 to −33.4‰, and δ15N of D. longispina and A. pacificus varied from 0.9 to 1.5‰ and −1.6 to −0.2‰, respectively. This implies that they rely on different food sources and food quality. δ13C of total particulate organic matter (POM) was always higher than zooplankton with the range of −29.3‰ to −26.2‰, but the δ15N of POM was between the two species, ranging from −2.8 to 1.7‰. The patterns of δ13C and δ15N suggest that A. pacificus might feed more on autochthonous organic matter compared with D. longispina. The differences in isotopic composition among co-existing herbivorous zooplankton species may be useful tools in investigating distinct energy pathways in unproductive lakes.

Stable Nitrogen and Carbon Isotopes May Not Be Good Indicators of Altitudinal Distributions of Montane Passerines

Abstract We examined δ15N and δ13C values of feathers from nine species, belonging to three feeding guilds (herbivores, omnivores, and insectivores), of wild passerines at eight sites along an altitudinal gradient (339–2,876 m asl) within Taroko National Park, Taiwan. We examined: (1) if altitudinal patterns in feather δ15N and δ13C are consistent with previously published values for plants and soils, (2) if feather δ15N and δ13C differ among sites, and (3) if there are year-to-year and/or month-to-month fluctuations in feather δ15N and δ13C of the same birds. We found no simple relationship between feather isotope values and altitude. Feather δ15N values decreased significantly with increasing altitude for insectivores, but not for herbivores and omnivores. Feather δ13C values increased significantly with increasing altitude for herbivores and omnivores, but not for insectivores. Altitudinal trends in feather δ15N and δ13C values exhibit even more inconsistent patterns when data were analyzed by species;...

Chapter 28 Late Cryogenian (Vendian) glaciogenic deposits in the Marnya Formation, Oselok Group, in the foothills of the East Sayan Range, southwestern Siberian Craton

Abstract The glaciogenic deposits of the Ulyakha Member (Mb.) referred to as Ulyakha diamictite (tillite), and the associated Late Cryogenian (Early Vendian) glaciofluvial deposits, are the lower strata of the Marnya Formation (Fm.) of the Oselok Group (Gr.) in the southwestern Siberian craton, which rest erosionally over the Cryogenian (Late Riphean) Karagassy Group. The Oselok Group deposits fill the Peri-Sayan foredeep and their stratigraphic equivalents immediately overlie the basement of the Siberian Platform. The glaciogenic deposits, including diamictite, breccia, boulder conglomerate and sandstone, had multistage sedimentation, were widespread, and underlie a cap dolomite of the lower Ozerki Mb. The Late Cryogenian (Early Vendian) age of the Ulyakha Mb. is defined by traces of shallow-marine soft-bodied animals in the middle part of the Ozerki Mb., and by findings of Ediacaran-like Metazoa in the overlying Bolshaya Aisa Mb. of the Marnya Fm. Deposition of the Ulyakha tillites and associated rocks has been correlated with the Late Cryogenian (Marinoan) glaciation based on the δ 13 C patterns in carbonate deposits in the Marnya and Uda formations and their stratigraphic position much below the Pre-Manykai and Zhuya δ 13 C negative signatures, which have been equated to the Wonoka anomaly.

Seasonal dynamics in the stable carbon isotope composition (δ13C) from non‐leafy branch, trunk and coarse root CO2 efflux of adult deciduous (Fagus sylvatica) and evergreen (Picea abies) trees

Respiration is a substantial driver of carbon (C) flux in forest ecosystems and stable C isotopes provide an excellent tool for its investigation. We studied seasonal dynamics in δ¹³C of CO₂ efflux (δ¹³C(E)) from non-leafy branches, upper and lower trunks and coarse roots of adult trees, comparing deciduous Fagus sylvatica (European beech) with evergreen Picea abies (Norway spruce). In both species, we observed strong and similar seasonal dynamics in the δ¹³C(E) of above-ground plant components, whereas δ¹³C(E) of coarse roots was rather stable. During summer, δ¹³C(E) of trunks was about -28.2‰ (Beech) and -26.8‰ (Spruce). During winter dormancy, δ¹³C(E) increased by 5.6-9.1‰. The observed dynamics are likely related to a switch from growth to starch accumulation during fall and remobilization of starch, low TCA cycle activity and accumulation of malate by PEPc during winter. The seasonal δ¹³C(E) pattern of branches of Beech and upper trunks of Spruce was less variable, probably because these organs were additionally supplied by winter photosynthesis. In view of our results and pervious studies, we conclude that the pronounced increases in δ¹³C(E) of trunks during the winter results from interrupted access to recent photosynthates.

Evidence for discrete subpopulations of sea perch (Helicolenus ercoides) across four fjords in Fiordland, New Zealand

In coastal populations of invertebrates and fishes, the distribution of discrete subpopulations is influenced by adult and larval dispersal, as well as by the effects of habitat heterogeneity on site fidelity or connectivity. Here, we examine evidence for spatial structure of sea perch, Helicolenus percoides, populations among four fjords in the Fiordland region of southwestern New Zealand. We examine patterns in adult morphology, length-at-age, δ13C and δ15N of muscle tissue, and trace elemental composition of whole otoliths as proxies for population isolation among the four inner fjord regions. A multivariate analysis of morphometrics reveals significant differences among populations from each of the four sites, suggesting existence of four distinct subpopulations. These patterns are consistent with observed differences in δ13C and δ15N, and length-at-age estimates among the four subpopulations. Differences in whole otolith concentrations of Sr, Ba, Mg and Li, and high classification scores based on the whole otolith elemental fingerprint are also consistent with significant subdivision among areas. Patterns across all four markers are consistent with discrete subpopulation structure of adult sea perch among the four study sites. These data indicate that the newly implemented network of marine protected areas in Fiordland is likely to contain discrete populations of sea perch.

Stable isotopic records of bleaching and endolithic algae blooms in the skeleton of the boulder forming coral Montastraea faveolata

Within boulder forming corals, fixation of dissolved inorganic carbon is performed by symbiotic dinoflagellates within the coral tissue and, to a lesser extent, endolithic algae within the coral skeleton. Endolithic algae produce distinctive green bands in the coral skeleton, and their origin may be related to periods of coral bleaching due to complete loss of dinoflagellate symbionts or “paling” in which symbiont populations are patchily reduced in coral tissue. Stable carbon isotopes were analyzed in coral skeletons across a known bleaching event and 12 blooms of endolithic algae to determine whether either of these types of changes in photosynthesis had a clear isotopic signature. Stable carbon isotopes tended to be enriched in the coral skeleton during the initiation of endolith blooms, consistent with enhanced photosynthesis by endoliths. In contrast, there were no consistent δ13C patterns directly associated with bleaching, suggesting that there is no unique isotopic signature of bleaching. On the other hand, isotopic values after bleaching were lighter 92% of the time when compared to the bleaching interval. This marked drop in skeletal δ13C may reflect increased kinetic fractionation and slow symbiont recolonization for several years after bleaching.