Combination Of Stable Isotopes Research Articles

Feeding ecology of Limnoperna fortunei in southern China: insights from stable isotopes and fatty-acid biomarkers

ABSTRACTLimnoperna fortunei (L. fortunei) is one of the most abundant freshwater bivalves in southeast Asia, with wide-ranging direct and indirect impacts on ecosystems. To estimate material flows in the habitats of L. fortunei, a combination of stable-isotope and fatty-acid analyses were applied to assess the feeding spectrum of L. fortunei in southern China. Using the isotope-mixing model, the contribution proportions to the diet of L. fortunei were estimated as 19.8%–28.2% for plankton, 57.6%–65.2% for particulate organic matter (POM) and 10.2%–21.1% for sediment organic matter. We conclude that POM is the principal food source of L. fortunei. The δ13C enrichment of fixed carbon from POM to L. fortunei was 0.67%–2.41%. Based on the fatty acid data, it was estimated that L. fortunei consumed or selectively accumulated Chlorophyceae, Cryptophyceae, Dinophyceae, bacteria and terrestrial organic matter. The feeding spectrum of L. fortunei is similar to that of Dreissena polymorpha. We suggest that L. fortunei is able to differentiate suitable food items using chemical cues and the surface properties of particles.

Zinc Homeostasis and isotopic fractionation in plants: a review

Recent advances in mass spectrometry have demonstrated that higher plants discriminate stable Zn isotopes during uptake and translocation depending on environmental conditions and physiological status of the plant. Stable Zn isotopes have emerged as a promising tool to characterize the plants response to inadequate Zn supply. The aim of this review is to build a comprehensive model linking Zn homeostasis and Zn isotopic fractionation in plants and advance our current view of Zn homeostasis and interaction with other micronutrients. The distribution of stable Zn isotopes in plants and the most likely causes of fractionation are reviewed, and the interactions with micronutrients Fe, Cu, and Ni are discussed. The main sources of Zn fractionation in plants are i) adsorption, ii) low- and high-affinity transport phenomena, iii) speciation, iv) compartmentalization, and v) diffusion. We propose a model for Zn fractionation during uptake and radial transport in the roots, root-to-shoot transport, and remobilization. Future work should concentrate on better understanding the molecular mechanisms underlying the fractionations as this will be the key to future development of this novel isotope system. A combination of stable isotopes and speciation analyses might prove a powerful tool for plant nutrition and homeostasis studies.

Spatial subsidies in spider diets vary with shoreline structure: Complementary evidence from molecular diet analysis and stable isotopes.

Inflow of matter and organisms may strongly affect the local density and diversity of organisms. This effect is particularly evident on shores where organisms with aquatic larval stages enter the terrestrial food web. The identities of such trophic links are not easily estimated as spiders, a dominant group of shoreline predator, have external digestion. We compared trophic links and the prey diversity of spiders on different shore types along the Baltic Sea: on open shores and on shores with a reed belt bordering the water. A priori, we hypothesized that the physical structure of the shoreline reduces the flow between ecosystem and the subsidies across the sea–land interface. To circumvent the lack of morphologically detectable remains of spider prey, we used a combination of stable isotope and molecular gut content analyses. The two tools used for diet analysis revealed complementary information on spider diets. The stable isotope analysis indicated that spiders on open shores had a marine signal of carbon isotopes, while spiders on reedy shores had a terrestrial signal. The molecular analysis revealed a diverse array of dipteran and lepidopteran prey, where spiders on open and reedy shores shared a similar diet with a comparable proportion of chironomids, the larvae of which live in the marine system. Comparing the methods suggests that differences in isotope composition of the two spider groups occurred because of differences in the chironomid diets: as larvae, chironomids of reedy shores likely fed on terrestrial detritus and acquired a terrestrial isotope signature, while chironomids of open shores utilized an algal diet and acquired a marine isotope signature. Our results illustrate how different methods of diet reconstruction may shed light on complementary aspects of nutrient transfer. Overall, they reveal that reed belts can reduce connectivity between habitats, but also function as a source of food for predators.

Colonisation of Remote Oceania: New dates for the Bapot‐1 site in the Mariana Islands

ABSTRACTThe colonisation of the Mariana Islands in Western Micronesia is likely to represent a long‐distance ocean dispersal of more than 2000 km, and establishing the date of human arrival in the archipelago is important for modelling Neolithic expansion in Island South‐East Asia and the Pacific. In 2010, Clark et al. published a paper discussing a number of radiocarbon dates from the Bapot‐1 site on Saipan Island, but a disparity between charcoal and marine shell (Anadara sp.) results prevented the calculation of a definitive age for the site and left open the possibility that Bapot‐1 was first settled as early as 3500 calBP. Here, we present new research using a combination of stable isotope (δ13C and δ18O) and 14C information to demonstrate that A. antiquata from the lowest layers of Bapot‐1 is affected by hardwaters. These new results indicate human arrival at Bapot‐1 occurred around 3200–3080 calBP (1250–1130 BC). We recommend a similar isotopic evaluation for other sites in the Marianas that are dated by marine shell.

Joint interpretation of enantiomer and stable isotope fractionation for chiral pesticides degradation

Chiral pesticides are important contaminants affecting the health and functioning of aquatic systems. The combination of stable isotope and enantiomer analysis techniques has been recently proposed to better characterize the fate of these contaminants in natural and engineered settings. We introduce a modeling approach with the aim of unifying and integrating the interpretation of isotopic and enantiomeric fractionation. The model is based on the definition of enantiomer-specific isotopologues and jointly predicts the evolution of concentration, enantiomer fractionation, as well as changes in stable isotope ratios of different elements. The method allows evaluating different transformation pathways and was applied to investigate enzymatic degradation of dichlorprop (DCPP), enzymatic degradation of mecoprop methyl ester (MCPPM), and microbial degradation of α-hexachlorocyclohexane (α-HCH) by different bacterial strains and under different redox conditions. The model accurately reproduces the isotopic and enantiomeric data observed in previous experimental studies and precisely captures the dual-dimensional trends characterizing different reaction pathways. Furthermore, the model allows testing possible combinations of enantiomer analysis (EA), compound specific isotope analysis (CSIA), and enantiomer specific isotope analysis (ESIA) to identify and assess isotope and enantiomer selective reaction mechanisms.

Combined Stable Isotopes and Multi-element Analysis to Research the Difference Between Organic and Conventional Chicken

The objective of this study was to investigate the difference of chicken from organic and conventional systems. Chicken samples from three farms (Beijing conventional farm, Beijing organic farm, and Jilin organic farm) of each type were measured for contents of protein and fat, stable carbon and nitrogen isotope ratios, and concentrations of 12 mineral elements (Na, Mg, K, Ca, V, Fe, Co, Ni, Cu, Rb, Ba, and Pb). As a result, the chicken of two organic groups (Beijing organic and Jilin organic) yielded more protein than the Beijing conventional group. The nitrogen and carbon stable isotope ratios of de-fatted chicken from organic groups were higher than those of conventional ones. Mineral elements in de-fatted chicken samples showed significant differences (p < 0.05) except for Mg. The analysis data of stable isotope ratios and multi-elements were subjected to principal component analysis (PCA). The organic and conventional groups can be clearly classified through PCA. The combination of stable isotopes and multi-elements can further classify the geographical origin of chicken. The research work brought about a discovery of the difference between the organic and conventional chicken.

Reversing diet-induced metabolic dysregulation by diet switching leads to altered hepatic de novo lipogenesis and glycerolipid synthesis.

In humans, low-energy diets rapidly reduce hepatic fat and improve/normalise glycemic control. Due to difficulties in obtaining human liver, little is known about changes to the lipid species and pathway fluxes that occur under these conditions. Using a combination of stable isotope, and targeted metabolomic approaches we investigated the acute (7–9 days) hepatic effects of switching high-fat high-sucrose diet (HFD) fed obese mice back to a chow diet. Upon the switch, energy intake was reduced, resulting in reductions of fat mass and hepatic triacyl- and diacylglycerol. However, these parameters were still elevated compared to chow fed mice, thus representing an intermediate phenotype. Nonetheless, glucose intolerance and hyperinsulinemia were completely normalized. The diet reversal resulted in marked reductions in hepatic de novo lipogenesis when compared to the chow and HFD groups. Compared with HFD, glycerolipid synthesis was reduced in the reversal animals, however it remained elevated above that of chow controls, indicating that despite experiencing a net loss in lipid stores, the liver was still actively esterifying available fatty acids at rates higher than that in chow control mice. This effect likely promotes the re-esterification of excess free fatty acids released from the breakdown of adipose depots during the weight loss period.

Trophic interactions of common elasmobranchs in deep-sea communities of the Gulf of Mexico revealed through stable isotope and stomach content analysis

Deep-water sharks are abundant and widely distributed in the northern and eastern Gulf of Mexico. As mid- and upper-level consumers that can range widely, sharks likely are important components of deep-sea communities and their trophic interactions may serve as system-wide baselines that could be used to monitor the overall health of these communities. We investigated the trophic interactions of deep-sea sharks using a combination of stable isotope (δ13C and δ15N) and stomach content analyses. Two hundred thirty-two muscle samples were collected from elasmobranchs captured off the bottom at depths between 200 and 1100m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Although we detected some spatial, temporal, and interspecific variation in apparent trophic positions based on stable isotopes, there was considerable isotopic overlap among species, between locations, and through time. Overall δ15N values in the NGS region were higher than in the WFS. The δ15N values also increased between April 2011 and 2012 in the NGS, but not the WFS, within Squalus cf. mitsukurii. We found that stable isotope values of S. cf. mitsukurii, the most commonly captured elasmobranch, varied between sample regions, through time, and also with sex and size. Stomach content analysis (n=105) suggested relatively similar diets at the level of broad taxonomic categories of prey among the taxa with sufficient sample sizes. We did not detect a relationship between body size and relative trophic levels inferred from δ15N, but patterns within several species suggest increasing trophic levels with increasing size. Both δ13C and δ15N values suggest a substantial degree of overlap among most deep-water shark species. This study provides the first characterization of the trophic interactions of deep-sea sharks in the Gulf of Mexico and establishes system baselines for future investigations.

A study of the interrelation between surface water and groundwater using isotopes and chlorofluorocarbons in Sanjiang plain, Northeast China

Surface water and groundwater are the main water resources used for drinking and production. Assess- ments of the relationship between surface water and groundwater provide information for water resource man- agement in Sanjiang plain, Northeast China. The surface water (river, lake, and wetland) and groundwater were sampled and analyzed for stable isotopic (dD, d 18 O) composition, tritium, and chlorofluorocarbons concentra- tions. The local meteoric water line is dD = 7.3d 18 O-6.7. The tritium (T) and chlorofluorocarbon (CFC) contents in groundwater were analyzed to determine the groundwater ages. Most groundwater were modern water with the ages \50 years. The groundwaters in mountain area and near rivers were younger than in the central plain. The oxygen isotope (d 18 O) was used to quantify the relationship between surface water and groundwater. The Songhua, Heilongjiang, and Wusuli rivers were gaining rivers, but the shallow groundwater recharged from rivers at the confluence area of rivers. At the confluence of Songhua and Heilongjiang rivers, 88 % of the shallow groundwater recharged from Songhua river. The combination of stable isotopes, tritium, and CFCs was an effectively method to study the groundwater ages and interrelation between sur- face water and groundwater. Practically, the farmlands near the river and under foot of the mountain could be culti- vated, but the farmlands in the central plain should be controlled.

Incorporation of Exotic Spartina alterniflora into Diet of Deposit-Feeding Snails in the Yangtze River Estuary Salt Marsh: Stable Isotope and Fatty Acid Analyses

The response of deposit-feeding animals to plant invasions is still unclear, because their food sources are often difficult to identify. We examined the effect of the exotic plant species, Spartina alterniflora, on the food source composition of two dominant snail species, Assiminea latericea and Cerithidea largillierti, in the Yangtze River estuary salt marsh using a combination of stable isotope and fatty acid analyses. We collected the snails and their potential food materials (sediment organic matter, particulate organic matter, and plant material) in S. alterniflora and native plant Phragmites australis marshes and then determined the composition of food sources of snails based on fatty acid markers and stable isotope composition. Our results indicated that A. latericea and C. largillierti are deposit feeders grazing on sedimentary particles originating from diatoms, bacteria, and vascular plants. Invasive S. alterniflora did not result in a change in the relative contribution of microalgae, bacteria, and vascular plants to the food source of the snails. Spartina alterniflora was confirmed to be assimilated by both snail species. The higher assimilation of S. alterniflora by A. latericea compared with C. largillierti is probably related to the greater ability of A. latericea to assimilate plant materials from detritus, as evidenced by fatty acid composition. Overall, S. alterniflora can be incorporated into the food web of the estuarine salt marsh by the dominant snail species with generalist-feeding habits.

Characterization of Flow Dynamics and Vulnerability in a Coastal Aquifer System

Traditional aquifer vulnerability techniques primarily rely on spatial property data for a region and are limited by their ability to directly or indirectly assess flow and transport processes occurring from the surface to depth within an aquifer system. The main objective of this study was to investigate groundwater vulnerability in terms of aquifer interconnectivity and flow dynamics. A combination of stable isotopes, groundwater age-dating (radiocarbon), and geomorphic/geogenic spatial analyses was applied to a regional, highly developed coastal aquifer to explain the presence of nitrate at depth. The average δ(13) C value (-17.3 ± 2‰ VPDB, n = 27) is characteristic of groundwater originating from locally infiltrated precipitation through extensively cultivated soils. The average δ(18) O and δD values (-4.0 ± 0.1‰ VSMOW, n = 27; δD: -19.3 ± 1‰ VSMOW, n = 27, respectively) are similar to precipitation water derived from maritime sources feeding the region's surface water and groundwater. Stable and radioactive isotopes reveal significant mixing between shallow and deep aquifers due to high velocities, hydraulic connection, and input of local recharge water to depths. Groundwater overdevelopment enhances deeper and faster modern water downward flux, amplifying aquifer vulnerability. Therefore, aquifer vulnerability is a variable, dependent on the type and degree of stress conditions experienced by a groundwater system as well as the geospatial properties at the near surface.

Methane Carbon Supports Aquatic Food Webs to the Fish Level

Large amounts of the greenhouse gas methane (CH4) are produced by anaerobic mineralization of organic matter in lakes. In spite of extensive freshwater CH4 emissions, most of the CH4 is typically oxidized by methane oxidizing bacteria (MOB) before it can reach the lake surface and be emitted to the atmosphere. In turn, it has been shown that the CH4-derived biomass of MOB can provide the energy and carbon for zooplankton and macroinvertebrates. In this study, we demonstrate the presence of specific fatty acids synthesized by MOB in fish tissues having low carbon stable isotope ratios. Fish species, zooplankton, macroinvertebrates and the water hyacinth Eichhornia crassipes were collected from a shallow lake in Brazil and analyzed for fatty acids (FA) and carbon stable isotope ratios (δ13C). The fatty acids 16∶1ω8c, 16∶1ω8t, 16∶1ω6c, 16∶1ω5t, 18∶1ω8c and 18∶1ω8t were used as signature for MOB. The δ13C ratios varied from −27.7‰ to −42.0‰ and the contribution of MOB FA ranged from 0.05% to 0.84% of total FA. Organisms with higher total content of MOB FAs presented lower δ13C values (i.e. they were more depleted in 13C), while organisms with lower content of MOB signature FAs showed higher δ13C values. An UPGMA cluster analysis was carried out to distinguish grouping of organisms in relation to their MOB FA contents. This combination of stable isotope and fatty acid tracers provides new evidence that assimilation of methane-derived carbon can be an important carbon source for the whole aquatic food web, up to the fish level.

Intensive nitrogen loss over the Omani Shelf due to anammox coupled with dissimilatory nitrite reduction to ammonium

A combination of stable isotopes ((15)N) and molecular ecological approaches was used to investigate the vertical distribution and mechanisms of biological N(2) production along a transect from the Omani coast to the central-northeastern (NE) Arabian Sea. The Arabian Sea harbors the thickest oxygen minimum zone (OMZ) in the world's oceans, and is considered to be a major site of oceanic nitrogen (N) loss. Short (<48 h) anoxic incubations with (15)N-labeled substrates and functional gene expression analyses showed that the anammox process was highly active, whereas denitrification was hardly detectable in the OMZ over the Omani shelf at least at the time of our sampling. Anammox was coupled with dissimilatory nitrite reduction to ammonium (DNRA), resulting in the production of double-(15)N-labeled N(2) from (15)NO(2)(-), a signal often taken as the lone evidence for denitrification in the past. Although the central-NE Arabian Sea has conventionally been regarded as the primary N-loss region, low potential N-loss rates at sporadic depths were detected at best. N-loss activities in this region likely experience high spatiotemporal variabilities as linked to the availability of organic matter. Our finding of greater N-loss associated with the more productive Omani upwelling region is consistent with results from other major OMZs. The close reliance of anammox on DNRA also highlights the need to take into account the effects of coupling N-transformations on oceanic N-loss and subsequent N-balance estimates.

Is European catfish a threat to eels in southern France?

Abstract European eel (Anguilla anguilla) is recognized as a critically endangered species in the northern hemisphere. Threats such as overfishing or pollution are well known as risks for eel populations. However, much less is known about the impact of introduced fish on European eels. In particular, introduced large‐bodied predators could become new predators to eels. The potential impact of European catfish (Silurus glanis L) on an eel population in the Camargue, southern France was studied using a combination of stable isotope and gut content analyses. Only large‐bodied catfish (&gt;500 mm) can consume numerous fish prey. However, catfish mostly consumed crayfish (Procambarus clarkii), these prey items being found in 79% of the guts of the largest individuals. Eel was absent from the dissected catfish guts. A mixing model based on Bayesian inference revealed that catfish diet included only 5% (0–8.5%) of marine sources (both eel and mullet). While local economic interests prompted ecological studies to assess whether catfish exerted a new and strong predatory pressure on eel, this study found that European catfish behaved as an opportunistic omnivore, and as such was not a direct threat as a predator on eel populations in the Camargue. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Activity, abundance and diversity of nitrifying archaea and bacteria in the central California Current

A combination of stable isotope and molecular biological approaches was used to determine the activity, abundance and diversity of nitrifying organisms in the central California Current. Using (15)NH(4)(+) incubations, nitrification was detectable in the upper water column down to 500 m; maximal rates were observed just below the euphotic zone. Crenarchaeal and betaproteobacterial ammonia monooxygenase subunit A genes (amoA), and 16S ribosomal RNA (rRNA) genes of Marine Group I Crenarchaeota and a putative nitrite-oxidizing genus, Nitrospina, were quantified using quantitative PCR. Crenarchaeal amoA abundance ranged from three to six genes ml(-1) in oligotrophic surface waters to > 8.7 x 10(4) genes ml(-1) just below the core of the California Current at 200 m depth. Bacterial amoA abundance was lower than archaeal amoA and ranged from below detection levels to 400 genes ml(-1). Nitrification rates were not directly correlated to bacterial or archaeal amoA abundance. Archaeal amoA and Marine Group I crenarchaeal 16S rRNA gene abundances were correlated with Nitrospina 16S rRNA gene abundance at all stations, indicating that similar factors may control the distribution of these two groups. Putatively shallow water-associated archaeal amoA types ('Cluster A') decreased in relative abundance with depth, while a deep water-associated amoA type ('Cluster B') increased with depth. Although some Cluster B amoA sequences were found in surface waters, expressed amoA gene sequences were predominantly from Cluster A. Cluster B amoA transcripts were detected between 100 and 500 m depths, suggesting an active role in ammonia oxidation in the mesopelagic. Expression of marine Nitrosospira-like bacterial amoA genes was detected throughout the euphotic zone down to 200 m. Natural abundance stable isotope ratios (delta(15)N and delta(18)O) in nitrate (NO(3)(-)) and nitrous oxide (N(2)O) were used to evaluate the importance of nitrification over longer time scales. Using an isotope mass balance model, we calculate that nitrification could produce between 0.45 and 2.93 micromol m(-2) day(-1) N(2)O in the central California Current, or approximately 1.5-4 times the local N(2)O flux from deep water.

Isotopes and geochemistry in a managed aquifer recharge scheme: a case study of fresh water injection at the Damascus University Campus, Syria

AbstractA combination of stable isotopes (18O and 2H) and hydrochemistry has been applied to investigate storage processes in relation to aquifer storage and recovery (ASR) of the shallow alluvial Quaternary aquifer in Damascus basin. The stored water, entirely taken from the Figeh springs during flood periods, was injected in a single well having a brackish groundwater. Water samples were collected from four observation wells drilled in the Damascus University Campus (DUC) site during a 3‐year period (2006–2008). The injectant water, which deviates in its chemical and isotopic signatures from that of the ambient groundwater, shows that the stored water plume remains within close proximity to the injection well (IW) (&lt;≈ 100 m). Thus, only two wells (W13 and W14) located at a distance less than 80 m from the injection point were affected by this injection. The observation wells located at longer distances from the IW (≈145 m and ≈ 600 m for wells W15 and WHz, respectively) were completely unaffected by the injection. Although most of the chemical and isotopic parameters usefully reflected the mixing process that occurs between the injectant water and ambient groundwater, the stable isotope (18O) and chloride (Cl−) were the most sensitive parameters that quickly reflect this signature. Using a simple mass balance, the calculated proportion of injectant water reaching the well W13 was in the range of 50–90%. This proportion was even lower (30–55%) in the case of well W14. Although the drought event prevailing during this study did not much help to inject further amounts of water, higher than the injected volume (0·2416 M m3) and also not favourable to better evaluate the fate and subsurface hydrological processes, these findings offer encouragement to continue the ASR activities, as an alternative way for better management of water resources in this basin facing intensive problems. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The contribution of groundwater discharge to the overall water budget of two typical Boreal lakes in Alberta/Canada estimated from a radon mass balance

Abstract. Radon-222, a naturally-occurring radioisotope with a half-life of 3.8 days, was used to estimate groundwater discharge to small lakes in wetland-dominated basins in the vicinity of Fort McMurray, Canada. This region is under significant water development pressure including both oil sands mining and in situ extraction. Field investigations were carried out in March and July 2008 to measure radon-222 distributions in the water column of two lakes as a tracer of groundwater discharge. Radon concentrations in these lakes ranged from 0.5 to 72 Bq/m3, while radon concentrations in groundwaters ranged between 2000 and 8000 Bq/m3. A radon mass balance, used in comparison with stable isotope mass balance, suggested that the two lakes under investigation had quite different proportions of annual groundwater inflow (from 0.5% to about 14% of the total annual water inflow). Lower discharge rates were attributed to a larger drainage area/lake area ratio which promotes greater surface connectivity. Interannual variability in groundwater proportions is expected despite an implied seasonal constancy in groundwater discharge rates. Our results demonstrate that a combination of stable isotope and radon mass balance approaches provides information on flowpath partitioning that is useful for evaluating surface-groundwater connectivity and acid sensitivity of individual water bodies of interest in the Alberta Oil Sands Region.

A brackish water aquatic foodweb: trophic levels and salinity gradients in the Schlei fjord, Northern Germany, in Viking and medieval times

This study serves for the definition of baseline isotopic signatures of vertebrates living in the Schlei fjord, a brackish water inlet in the north German plain, where the salinity decreases from its mouth at the Baltic Sea towards the inland locations. The Viking trade centre Haithabu and its immediate successor, the town of Schleswig, are located at opposite banks of the Schlei and constitute a settlement continuum from the 9th until the 13th century. This development not only includes a relocation of the settlement site, but also a change in economy and social structure, and witnesses the metamorphosis from an international trading locality to the rise and decline of a prototypical medieval town with town charter. In this paper, stable isotope ratios of bone collagen and bone structural carbonate of 141 vertebrate bone finds mainly of fish, birds, and sea mammals from both sites are reported to provide the baseline food web in this brackish water environment, which is the prerequisite for our ongoing studies aiming at the reconstruction of human subsistence strategies as well as the geographic origin of humans, animals, food stuffs, and raw materials in order to complete the historical picture of emerging medieval towns in a complex palaeoecosystem. In particular, we are able to show how a combination of stable isotopes from bone collagen and carbonate is capable of defining the salinity gradients in the aquatic environment.

Allochthonous brown algae are the primary food source for consumers in a temperate, coastal environment

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 376:33-44 (2009) - DOI: https://doi.org/10.3354/meps07810 Allochthonous brown algae are the primary food source for consumers in a temperate, coastal environment Karen R. Crawley1,4,*, Glenn A. Hyndes1, Mathew A. Vanderklift1,2, Andrew T. Revill3, Peter D. Nichols3 1Centre for Marine Ecosystems Research, School of Natural Sciences, Edith Cowan University, Joondalup, Western Australia 6027, Australia 2CSIRO Marine and Atmospheric Research, Floreat, Western Australia 6014, Australia 3CSIRO Marine and Atmospheric Research, Hobart, Tasmania 7001, Australia 4Present address: Oceanica, PO Box 3172, Broadway, Nedlands, Western Australia 6009, Australia *Email: karen.crawley@oceanica.com.au ABSTRACT: In several parts of the world, detached seagrass and macroalgae accumulate in the surf zone where in situ primary production can be low. This allochthonous resource is therefore likely to be important to consumers, but the various components of the resource likely play different roles in the food webs. We traced sources of production for the abundant amphipod Allorchestes compressa and 2 key predatory fishes in the surf zone of southwestern Australia using multiple stable isotopes (δ13C, δ15N and δ34S) and fatty acids. Seagrasses had higher δ13C than macroalgae, while δ13C of red and brown macroalgae were similar. Mixing models based on δ13C were ambiguous and indicated that brown algae and seagrasses were both feasible carbon sources for A. compressa. δ15N varied little between seagrasses and macroalgae, while δ15N of amphipods was higher and δ15N of fish higher again. δ34S was not useful in distinguishing between macrophytes or trophic levels. The fatty acid composition of brown and red algae and seagrasses were distinct. The composition of essential fatty acids (i.e. fatty acids that the consumer must obtain through its diet) of A. compressa was most similar to that of brown algae. The combination of stable isotope and fatty acid analyses indicates that, although brown algae comprises a lower proportion of wrack biomass than seagrass (17 to 28% vs. 52 to 58%), brown algae, particularly the kelp Ecklonia radiata, contributes disproportionately to the surf-zone food web in southwestern Australia. KEY WORDS: Wrack · Stable isotopes · Fatty acids · Spatial subsidy · Surf zone Full text in pdf format PreviousNextCite this article as: Crawley KR, Hyndes GA, Vanderklift MA, Revill AT, Nichols PD (2009) Allochthonous brown algae are the primary food source for consumers in a temperate, coastal environment. Mar Ecol Prog Ser 376:33-44. https://doi.org/10.3354/meps07810 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 376. Online publication date: February 11, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Feeding ecology of the grooved tiger shrimp Penaeus semisulcatus De Haan (Decapoda: Penaeidae) in inshore waters of Qatar, Arabian Gulf

The feeding ecology of the green tiger shrimp Penaeus semisulcatus was studied in inshore fishing grounds off Doha, Qatar, using a combination of stable isotope (δ13C and δ15N) analysis and gut contents examination. Samples of post-larvae, juvenile and adult shrimp and other organisms were collected from intertidal and subtidal zones during the spawning season (January–June). Shrimp collected from shallow water seagrass beds were mostly post-larvae and juveniles and were significantly smaller than the older juveniles and adults caught in deeper macroalgal beds. Gut content examination indicated that post-larvae and juvenile shrimp in seagrass beds fed mainly on benthos such as Foraminifera, polychaetes, benthic diatoms and small benthic crustaceans (amphipods, isopods and ostracoda), whereas larger shrimp in the macroalgal beds fed mainly on bivalve molluscs and to a lesser extent polychaetes. In shrimp from both seagrass and algal beds, unidentifiable detritus was also present in the gut (18, 32%). δ13C values for shrimp muscle tissue ranged from −9.5 ± 0.26 to −12.7 ± 0.05‰, and δ15N values increased with increasing shrimp size, ranging from 4.1 ± 0.03 to 7.7 ± 0.11‰. Both δ15N values and δ13C values for shrimp tissue were consistent with the dietary sources indicated by gut contents and the δ13C and δ15N values for primary producers and prey species. The combination of gut content and stable isotope data demonstrates that seagrass beds are important habitats for post-larvae and juvenile P. semisulcatus, while the transition to deeper water habitats in older shrimp involves a change in diet and source of carbon and nitrogen that is reflected in shrimp tissue stable isotope ratios. The results of the study confirm the linkage between sensitive shallow water habitats and the key life stages of an important commercially-exploited species and indicate the need for suitable assessment of the potential indirect impacts of coastal developments involving dredging and land reclamation.