The oxygen and carbon isotope distribution in the Mediterranean water masses

The oxygen and carbon stable isotope compositions of the present-day Mediterranean waters have been measured in order to evaluate their variability, which is related to the specific climatic and hydrological conditions within the basin. The experimental equation between the δ¹⁸O value and the salinity of water, based on 300 measurements on surface, intermediate, and deep waters sampled during the VICOMED 2 and 3 cruises in the western, central and eastern Mediterranean, has a slope of 0.27, a value which is significantly lower than the slope of 0.45, as defined in the northeast Atlantic Ocean. This difference in the δ¹⁸O–salinity relationship, which occurs immediately in the Alboran basin, is basically a characteristic of the climatic regime of the Mediterranean, i.e., of an excess evaporation over fresh water input. The largest variations of these two parameters, δ¹⁸O of water and δ¹³C of ∑CO₂, are observed in the surface waters, mostly in the western Mediterranean. This evolution mirrors the progressive eastward restriction, which separates the less-evaporated and more-productive western basins from the more-evaporated and less-productive eastern basins. The intermediate waters constitute a homogeneous layer. However, their δ¹⁸O values decrease eastward by 0.35‰ at maximum, due to progressive dilution by mixing with overlying and underlying water masses; their δ¹³C values decrease also eastward by 0.35‰ at maximum, due to an increasing input of nutrients issued from the regeneration of sinking organic particles. The deep waters have similar δ¹⁸O values but slightly higher δ¹³C values (often by less than 0.1‰) than the overlying intermediate waters, indicating generally well ventilated conditions due to active winter convection.     

Spatiotemporal variations of the δ18O–salinity relation in the northern Indian Ocean

A new data set of oxygen isotopic composition (δ¹⁸O) and salinity (S) of surface and sub-surface waters of the northern Indian Ocean, collected during the period 1987–2009, is presented. While the results are consistent with positive P?E (excess of precipitation over evaporation) over the Bay of Bengal and negative P?E over the eastern Arabian Sea, a significant spatiotemporal variability in the slope (also intercept) of the δ¹⁸O–S relation is observed in the Bay; the temporal variability is difficult to discern in the Arabian Sea. The slope and intercept are positively and negatively correlated, respectively, with the annual rainfall over India, a rough measure of river runoff. Both the slope and intercept appear to be sensitive to rainfall; the slope (intercept) is higher (lower) during years of stronger monsoon. The observed variability in the δ¹⁸O–S relation implies that caution needs to be exercised in paleosalinity estimations, especially from the Bay of Bengal, based on δ¹⁸O of marine organisms.     

Carbon cycle and sea-water palaeotemperature evolution at the Middle–Late Jurassic transition,eastern Paris Basin (France)

A very high-resolution carbon and oxygen stable isotope analysis (bulk-carbonate) of a biostratigraphically well-constrained Callovian–Oxfordian series is provided here for the first time. The homogeneity of the clayey series and the weak diagenetic alteration allow the isotopic signal variations to be considered as primary in origin. A prominent and brief negative excursion in the δ¹³C curve (−2‰), occurring at the start of the Middle Callovian (Jason Zone – Obductum Subzone) and correlated regionally, suggests a possible methane release. The increasing δ¹³C values thereafter up to the Early Oxfordian, concomitant with a warming episode, highlight the burial of carbon in organic-rich layers which, in return, may have triggered a decrease in atmospheric pCO₂. At higher frequencies, observed fluctuations of the δ¹³C and δ¹⁸O values are orbitally driven (405-kyr and 100-kyr eccentricity cycles) and may correspond to the salinity and temperature variability recorded in sea water. The δ¹⁸O isotopic measurements from well-preserved diagenetically screened belemnites and bivalves along the series, compared to available data from Tethyan domains, agree with the scenario of a global cooling at the Middle-Late Jurassic transition. The well-dated δ¹⁸O isotopic curve suggests that the onset of this cooling event occurred at the end of the Coronatum Zone (Middle Callovian).     

High resolution oxygen isotope and grayscale records of a medieval fossil giant clam (Tridacna gigas) in the South China Sea：physiological and paleoclimatic implications

Mollusks are well known for their detailed recording of paleoenvironmental and paleoclimatic changes in their carbonate shells. In this study, we constructed 18-year blue color intensity and oxygen isotope profiles of a 14 C dated(AD 990±40) fossil giant clam, Tridacna gigas, from Shidao Island, South China Sea. The δ18O profile of the T. gigas specimen displayed regular annual cycles and was probably controlled by seasonal variations of the climatic parameters. The blue color intensity profile showed good agreement with the δ18O series, and both had 18 clear annual cycles in accordance with the 18 visually identified annual growth bands. The annual shell growth rate determined from the blue color intensity and oxygen isotope profiles indicated that the annual shell increment of the Tridacna specimen was stable after the onset of sexual maturity. Spectral analysis of the δ18O and blue color intensity time series suggested that the El Nio–Southern Oscillation(ENSO) period observed in the instrumental temperature and precipitation records of the South China Sea during the past 50 years also existed in medieval times. Our results showed that fossil giant clams could provide a good archive of historical intra-seasonal to decadal climate variations.     

The impact of organic fluids on the carbon isotopic compositions of carbonate-rich reservoirs: Case study of the Lucaogou Formation in the Jimusaer Sag,Junggar Basin,NW China

The processes involved in the interaction between organic fluids and carbonates, and the resulting effect on reservoir quality during the evolution and maturation of organic matter remain unclear despite the fact that these processes influence the carbon and oxygen isotopic compositions of carbonates. Here, we provide new insights into these processes using data obtained from a detailed analysis of a mixed dolomitic–clastic and organic-rich sedimentary sequence within the middle Permian Lucaogou Formation in the Junggar Basin of NW China. The techniques used during this study include drillcore observations, thin section petrography, scanning electron microscopy (SEM) and electron probe microanalysis, and carbon and oxygen isotope analyses. Oil grades and total organic carbon (TOC) contents represent the amount of oil charging and the abundance of organic fluids within a reservoir, respectively, and both negatively correlate with the whole-rock δ¹³C and δ¹⁸O of the carbonates in the study area, indicating that organic fluids have affected the reservoir rocks. Secondary carbonates, including sparry calcite and dolomite overgrowths and cements, are common within the Lucaogou Formation. Well-developed sparry calcite is present within dark mudstone whereas the other two forms of secondary carbonates are present within the dolomite-rich reservoir rocks in this formation. Comparing thin section petrology with δ¹³C compositions suggests that the carbon isotopic composition of matrix carbonates varies little over small distances within a given horizon but varies significantly with stratigraphic height as a result of the development of secondary carbonates. The net change in whole-rock δ¹³C as a result of these secondary carbonates ranges from 1.8‰ to 4.6‰, with the secondary carbonates having calculated δ¹³C compositions from −18.6‰ to −8.5‰ that are indicative of an organic origin. The positive correlation between the concentration of Fe within matrix and secondary carbonates within one of the samples suggests that the diagenetic system within the Lucaogou Formation was relatively closed. The correlation between δ¹³C and δ¹⁸O in carbonates is commonly thought to be strengthened by the influence of meteoric water as well as organic fluids. However, good initial correlation between δ¹³C and δ¹⁸O of whole rock carbonates within the Lucaogou Formation (resulted from the evaporitic sedimentary environment) was reduced by organic fluids to some extent. Consequently, the δ¹³C–δ¹⁸O covariations within these sediments are not always reliable indicators of diagenetic alteration by organic fluids or meteoric water.The characteristics and δ¹³C compositions of the sparry calcite within the formation is indicative of a genetic relationship with organic acids as a result of the addition of organic CO₂ to the reservoir. Further analysis suggests that both carbonate and feldspar were dissolved by interaction with organic CO₂. However, dissolved carbonate reprecipitated as secondary carbonates, meaning that the interaction between organic fluids and dolomites did not directly improve reservoir quality, although this process did enhance the dissolution of feldspar and increase porosity. This indicates that the δ¹³C and δ¹⁸O of secondary carbonates and their influence on whole-rock carbonate isotopic values can be used to geochemically identify the effect of organic fluids on closed carbonate-rich reservoir systems.     

Seasonality and growth patterns using isotope sclerochronology in shells of the Pliocene scallop Chesapecten madisonius

Growth lines and variation in oxygen and carbon isotope ratios (δ¹⁸O and δ¹³C) in shells of the Pliocene scallop Chesapecten madisonius preserve seasonal chronologies of biological and environmental change. This study evaluated whether (1) prominent growth lines were formed annually, and (2) growth rates estimated using isotope sclerochronology were comparable to rates estimated using visual inspection (measuring the width between external growth lines). We compared both techniques for estimating growth rates and age on three late to mid-Pliocene C. madisonius shells. The first approach located prominent growth lines on the δ¹⁸O time series, and differentiated between annual and non-annual (disturbance) growth lines. The second approach assumed all prominent lines were annual. This comparison showed that visual inspection underestimated growth rates and overestimated age. Seasonal timing of annual growth line formation using isotope sclerochronology provided unexpected results. Because this region fell within the warm-temperate paleobiogeographic province, we predicted annual lines formed during summers (most negative δ¹⁸O values). Instead, annual growth lines coincided with the most positive δ¹⁸O values (winter), typical of bivalves from cold-temperate regions. Moreover, shells recorded seasonal temperatures ranging from 3.2–20.8°C, a range lower than the thermal regime defined for warm-temperate environments (8–25°C). Possibly, the Sea Slope Gyre, which mixed eddies and cold filaments of the Labrador Current and warm waters of the Gulf Stream, penetrated the warm-temperate environment in this region. Alternatively, warm-water fauna from the zoogeographic Carolinian subprovince migrated northward and endured by virtue of warm summer temperatures. Regardless of the explanation, our findings provide a glimpse of mid-latitude seasonal temperature range for a warm climate episode during the mid-Pliocene.     

Age verification,growth and life history of rubyfish Plagiogeneion rubiginosum

Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (¹⁴C) and stable isotope (δ¹⁸O and δ¹³C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core ¹⁴C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the ¹⁴C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ¹⁸O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ¹³C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns.     

Dynamics and sources of suspended particulate organic matter in the Marennes-Oléron oyster farming bay: Insights from stable isotopes and microalgae ecology

The aim of this study was to distinguish between sources of the complex variety of Marennes-Oléron Bay suspended particulate organic matter (SPOM) contributing to the tropho-dynamics of the Marennes-Oléron oyster farming bay. Basic biomarkers (Chl a, C/N and POC/Chl a ratios), carbon and nitrogen stable isotopes from SPOM were analyzed and the microalgae community was characterized. The sampling strategy was bimonthly from March 2002 to December 2003; samples were taken from an intertidal mudflat. Four main sources contributed to the SPOM pool: terrigenous input from rivers, neritic phytoplankton, resuspended microphytobenthos and periodic inputs from intertidal Zostera noltii meadows. Seasonal fluctuations were observed in both years of the study period: (1) SPOM collected in the spring of 2002 (δ¹³C = −25‰ to −23‰) was mainly composed of fresh estuarine inputs; (2) SPOM from the summer and fall of 2002 and 2003 was predominantly neritic phytoplankton (δ¹³C = − 22‰ to −19‰); (3) SPOM from the winter of 2002, spring of 2003 and winter of 2003 (δ¹³C = −21 to −23‰) was composed of a mixture of decayed terrigenous river inputs and pelagic phytoplankton, which was predominantly resuspended microphytobenthos. In the summer of 2003—the warmest summer on record in southern France and Europe—SPOM was particularly enriched for ¹³C, with δ¹³C values ranging from −14‰ to −12‰. Pulses in δ¹³C values, indicative of ¹³C-enriched decaying materials, extended into the fall. These were attributed to benthic intertidal inputs, including both resuspended microphytobenthos and Z. noltii detritus. Changes in SPOM sources in Marennes-Oléron Bay may lead to differences in the quality of the trophic environment available for reared oysters.     

Isotope parameters (δD, δ<Superscript>18</Superscript>O) and sources of freshwater input to Kara Sea

The isotope characteristics (δD, δ¹⁸О) of Kara Sea water were studied for quantitative estimation of freshwater runoff at stations located along transect from Yamal Peninsula to Blagopoluchiya Bay (Novaya Zemlya). Freshwater samples were studied for glaciers (Rose, Serp i Molot) and for Yenisei and Ob estuaries. As a whole, δD and δ¹⁸O are higher in glaciers than in river waters. isotope composition of estuarial water from Ob River is δD =–131.4 and δ18O =–17.6‰. Estuarial waters of Yenisei River are characterized by compositions close to those of Ob River (–134.4 and–17.7‰), as well as by isotopically “heavier” compositions (–120.7 and–15.8‰). Waters from studied section of Kara Sea can be product of mixing of freshwater (δD =–119.4, δ¹⁸O =–15.5) and seawater (S = 34.9, δD = +1.56, δ¹⁸O = +0.25) with a composition close to that of Barents Sea water. isotope parameters of water vary significantly with salinity in surface layer, and Kara Sea waters are desalinated along entire studied transect due to river runoff. concentration of freshwater is 5–10% in main part of water column, and <5% at a depth of >100 m. maximum contribution of freshwater (>65%) was recorded in surface layer of central part of sea.     

Hydrographical characteristics and oxygen isotopic signatures of water in a coastal environment (Mangalore) along the southeastern Arabian Sea

Coastal marine environments are important links between the continents and the open ocean. The coast off Mangalore forms part of the upwelling zone along the southeastern Arabian Sea. The temperature, salinity, density, dissolved oxygen and stable oxygen isotope ratio (δ¹⁸O) of surface waters as well as those of bottom waters off coastal Mangalore were studied every month from October 2010 to May 2011. The coastal waters were stratified in October and November due to precipitation and runoff. The region was characterised by upwelled bottom waters in October, whereas the region exhibited a temperature inversion in November. The surface and bottom waters presented almost uniform properties from December until April. The coastal waters were observed to be most dense in January and May. Comparatively cold and poorly oxygenated bottom waters during the May sampling indicated the onset of upwelling along the region. δ¹⁸O of the coastal waters successfully documented the observed variations in the hydrographical characteristics of the Mangalore coast during the monthly sampling period. We also noted that the monthly variability in the properties of the coastal waters of Mangalore was related to the hydrographical characteristics of the adjacent open ocean inferred from satellite-derived surface winds, sea surface height anomaly data and sea surface temperatures.     

The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen

We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate δ¹⁵N and δ¹⁸O in the ocean interior. The δ¹⁸O of nitrate is our focus because it has been explored less in previous work. Denitrification raises the δ¹⁵N and δ¹⁸O of mean ocean nitrate by equal amounts above their input values for N₂ fixation (for δ¹⁵N) and nitrification (for δ¹⁸O), generating parallel gradients in the δ¹⁵N and δ¹⁸O of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the δ¹⁵N and δ¹⁸O of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The δ¹⁵N of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in δ¹⁸O due to denitrification or nitrate assimilation with nitrate having the δ¹⁸O of nitrification. This lowers the δ¹⁸O of mean ocean nitrate and weakens nitrate δ¹⁸O gradients in the interior relative to those in δ¹⁵N. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both δ¹⁸O and δ¹⁵N within the ocean interior and a mean ocean nitrate δ¹⁸O that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the δ¹⁵N and δ¹⁸O of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone.     

Seawater temperature records from stable isotopic profiles in the shell of Modiolus modiolus

The hypothesis that the sea urchin disease, which devastated populations along the Atlantic coast of Nova Scotia in 1980–83, is temperature related requires a record of bottom seawater temperatures over this period. A time series of δ¹⁸O values from two Modiolus shells, collected in a cove in Nova Scotia, were used to reconstruct bottom water temperatures and as an independent method to age the mussels. A fine scale of resolution was achieved, with up to 15 discrete samples per year of shell deposition. Records from two shells showed similar trends. The δ¹⁸O values of the shells clearly tracked seasonal temperatures. They suggested that bottom seawater temperatures were not unusually warm at this site in 1980, the year in which the sea urchin disease was first noticed. Ages of mussels determined from the oxygen isotope record were consistent with those estimated from annual growth lines on the shells.     

Trophic ecology of a resident Yellow-legged Gull (Larus michahellis) population in the Bay of Biscay

Stable isotopes analyses (SIAs) are an efficient tool to obtain a general insight into the diet of generalist consumers, such as the Yellow-legged Gull (Larus michahellis). Here we analysed δ¹³C, δ¹⁵N and δ³⁴S values in feathers of chicks and adults, and used Bayesian triple-isotope mixing models to reconstruct the diet of a Yellow-legged Gull population breeding in the southeastern Bay of Biscay. Questions to test were (1) whether adults and chicks rely on different feeding resources during breeding period; (2) whether there is a seasonal foraging effect involving a higher proportion of refuse food in winter compared to summer, and (3) the magnitude of the annual variation in diet. Prey consumption differed between colonies, among years, and also varied slightly between seasons, and this was mainly due to a differential use of prey of marine origin. However, diet did not differ between age classes. These results suggest a relatively monotonous diet with only slight variations from year to year, seasonally and at a local geographic scale.     

Reconstructing estuarine conditions: oyster shells as recorders of environmental change, Southwest Florida

Live-collected shells of the oyster, Crassostrea virginica, contain geochemical records of modern temperature and salinity, so records of prehistoric conditions may be obtained from subfossil shells. Restoration of channelized watersheds in Florida is receiving much attention, and plans for targeted watersheds require information about estuarine conditions before channelization. Lack of historical records necessitates alternative methods to understand pre-disturbance conditions. A ¹⁴C-calibrated, amino-acid geochronology based on racemization of glutamic acid yielded ages ranging from 190–1220 AD and from 1270–1860 AD for subfossil oysters from Blackwater River (near-natural watershed) and for Faka-Union Bay (channelized watershed), respectively. δ¹⁸O and δ¹³C values of subfossil shells from Blackwater River indicate salinity and summer temperatures similar to present. Winter temperatures recorded in shells from 190, 590, 720, and 1050 AD appear 1–5 °C colder than present winter temperatures, whereas the shell from 1220 AD records winter temperatures similar to modern winter temperatures. These temperature shifts may indicate change in climate or natural seasonal variation of winter temperature from year to year. Subfossils from Faka-Union Bay may reflect a complicated hydrology, which cannot be evaluated by isotopic compositions alone and demonstrates the need for development of independent elemental proxies for temperature and salinity. Decreases in δ¹³C from subfossil to modern shells may in part result from CO₂ added to the atmosphere from fossil fuel burning (the Suess effect). Subfossil δ¹³C that is >1‰ more positive than modern shells suggest a change in the dominant carbon sources from terrestrial C₄ or aquatic plants to C₃ plants (mangroves).     

Importance of seagrass as a carbon source for heterotrophic bacteria in a subtropical estuary (Florida Bay)

A stable carbon isotope approach was taken to identify potential organic matter sources incorporated into biomass by the heterotrophic bacterial community of Florida Bay, a subtropical estuary with a recent history of seagrass loss and phytoplankton blooms. To gain a more complete understanding of bacterial carbon cycling in seagrass estuaries, this study focused on the importance of seagrass-derived organic matter to pelagic, seagrass epiphytic, and sediment surface bacteria. Particulate organic matter (POM), seagrass epiphytic, seagrass (Thalassia testudinum) leaf, and sediment surface samples were collected from four Florida Bay locations with historically different organic matter inputs, macrophyte densities, and primary productivities. Bulk (observed and those reported previously) and compound-specific bacterial fatty acid δ¹³C values were used to determine important carbon sources to the estuary and benthic and pelagic heterotrophic bacteria. The δ¹³C values of T. testudinum green leaves with epiphytes removed ranged from −9.9 to −6.9‰. Thalassia testudinum δ¹³C values were significant more enriched in ¹³C than POM, epiphytic, and sediment samples, which ranged from −16.4 to −13.5, −16.2 to −9.6, and −16.7 to −11.0‰, respectively. Bacterial fatty acid δ¹³C values (measured for br14:0, 15:0, i15:0, a15:0, br17:0, and 17:0) ranged from −25.5 to −8.2‰. Assuming a −3‰ carbon source fractionation from fatty acid to whole bacteria, pelagic, epiphytic, and sediment bacterial δ¹³C values were generally more depleted in ¹³C than T. testudinum δ¹³C values, more enriched in ¹³C than reported δ¹³C values for mangroves, and similar to reported δ¹³C values for algae. IsoSource mixing model results indicated that organic matter derived from T. testudinum was incorporated by both benthic and pelagic bacterial communities, where 13–67% of bacterial δ¹³C values could arise from consumption of seagrass-derived organic matter. The IsoSource model, however, failed to discriminate clearly the fraction of algal (0–86%) and mangrove (0–42%) organic matter incorporated by bacterial communities. These results indicate that pelagic, epiphytic, and sediment surface bacteria consumed organic matter from a variety of sources. Bacterial communities incorporated consistently seagrass-derived organic matter, the dominant macrophyte in Florida Bay, but seagrass δ¹³C values alone could not account fully for bacterial δ¹³C values.     

Seasonal oxygen and carbon isotope variability in euthecosomatous pteropods from the Sargasso Sea

We examine seasonal variations in the stable carbon and oxygen isotopic composition of individual shells of the pteropods Limacina inflata and Styliola subula, collected from Oceanic Flux Program sediment traps (at 500 m depth) near Bermuda in the western Sargasso Sea. Calcification depths estimated from L. inflata δ¹⁸O vary between 200 and 650 m in late winter and spring, and between 50 and 250 m in late summer and fall. S. subula shows similar seasonal variability with calcification depths between 250 and 600 m in late winter and spring and 50–400 m in late summer and fall. These results suggest that both species calcify across a greater range of depths than indicated by previous geochemical studies. Furthermore, the data indicate that these species change their calcification depth in conjunction with changes in thermal stratification of the water column. Pteropod shell δ¹³C values vary inversely with δ¹³C_DIC but show a positive correlation with seawater [CO₃²⁻] and temperature after depth differences in δ¹³C_DIC are accounted for. We hypothesize that either the influence of temperature on metabolic CO₂ incorporation during shell growth and/or the influence of ambient [CO₃²⁻] on shell geochemistry can explain these relationships. Taken together, the individual shell δ¹⁸O and δ¹³C data suggest that shell calcification, and by inference the life cycle, of these pteropods is several months or less. Individual pteropod shell analyses have potential for contributing to our understanding of the environmental parameters that play a role in seasonal calcification depth shifts, as well as to our knowledge of past upper ocean thermal structure.     

Host‐dependent differences in resource use associated with Anilocra spp. parasitism in two coral reef fishes,as revealed by stable carbon and nitrogen isotope analyses

The role of parasites in trophic ecology is poorly understood in marine ecosystems. Stable isotope analyses (SIA) have been widely used in studies of trophic ecology, but have rarely been applied to study the role of parasites. Considering that some parasites are associated with altered host foraging patterns, SIA can help elucidate whether parasitism influences host trophic interactions. French grunt (Haemulon flavolineatum), an abundant Caribbean coral reef fish, contributes greatly to trophic connectivity. They typically depart the reef at dusk, feed overnight in seagrass beds, and return to the reef at dawn. The large parasitic isopod Anilocra haemuli commonly infects French grunt, and infected fish are less likely to complete their diel migration, and are in poorer condition than uninfected conspecifics. Brown chromis (Chromis multilineata) are diurnally feeding planktivores and infection by Anilocra chromis does not influence host condition. To determine if Anilocra infection influences host diet and foraging locality, we conducted stable carbon and nitrogen isotope analyses on scale, muscle, heart and gill tissues of infected and uninfected French grunt and brown chromis. We determined that all French grunt had δ¹³C values representative of seagrass habitats, but infected French grunt were significantly enriched in ¹³C and ¹⁵N compared to uninfected conspecifics. This suggests that compared to uninfected conspecifics, infected French grunt forage in seagrass, but on isotopically enriched prey, and/or are in poorer condition, which can elevate δ¹³C and δ¹⁵N values. For brown chromis, infection did not significantly influence any δ¹³C and δ¹⁵N values; hence they all foraged in the same environment and on similar prey. This is the first study to use SIA to examine differences in resource use by Caribbean coral reef fishes associated with parasitism and to evaluate how closely related parasites might have host‐dependent effects on host trophic ecology.     

Ecosystem service values of sediment generation and entrapment by marginal coral reefs at Sodwana Bay,South Africa

Coral reefs provide a multitude of goods and services, some of which are difficult to value due to their intangible nature and the absence of markets to ascribe their relative worth. The coral reefs of Sodwana Bay on the northeast coast of South Africa provide several ecological goods and services, of which only two are considered here: namely, sediment generation and sediment entrapment. Both are deemed essential to the functioning of the Sodwana Bay economy. The replacement-cost method was used to estimate the annual financial cost of sediment provided to the study area if it were replaced by dredging. Sediment generation by the coral reefs was valued at R2.6–R4.8 million, and sediment entrapment valued at R71.8–R84.6 million, totalling between R74.4 million and R89.4 million (≈$5.6–$6.7 million, at R13.38/US$1) per year.     

Sublittoral seaweed communities on natural and artificial substrata in a high-latitude coral community in South Africa

Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system.     

A new TOC,Rock-Eval,and carbon isotope record of Lower Jurassic source rocks from the Slyne Basin,offshore Ireland

This paper presents an integrated assessment of total organic carbon, Rock-Eval pyrolysis, carbonate δ¹³C and δ¹⁸O, and total organic carbon δ¹³C record of Upper Sinemurian–Aalenian age from the Slyne Basin (well 18/25-1), offshore Ireland. Total organic carbon (up to 5.2 wt%) and Rock-Eval pyrolysis data highlights the Portree Shale Formation Equivalent (Lower–?Middle Toarcian) as a mature (T_max ∼440 °C) source rock dominated by type II kerogens. This interval is more than 90 m thick.In a previously unexplored paleogeographical domain regarding stable carbon isotopes, the δ¹³C record shows positive values during the Upper Sinemurian, a negative trend followed by a minor positive trend during the uppermost Sinemurian–Lower Pliensbachian, a negative trend during the lowermost Lower Toarcian, and then the return to more positive δ¹³C values. Despite the biostratigraphic uncertainty, the coarse resolution of the dataset, and the complex assessment of diagenetic effects, we suggest that the δ¹³C record of the studied well records the Raricostatum Zone positive CIE, the Sinemurian-Pliensbachian Boundary Event, and the negative CIE associated with the T-OAE. The T-OAE positive CIE is not clearly defined in the obtained dataset. The slight post T-OAE negative CIE recovery to more positive values and the continuation of a relatively high organic content is coeval with a regional organic matter preservation interval observed in several Northern-European locations.These new datasets and their interpretation add to the understanding of the paleoenvironmental dynamics during the Early–?Middle Jurassic in the Northern European domain and opens new possibilities for hydrocarbon exploration in Ireland's offshore.