bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotopic evidence for chemosynthesis‐based nutrition of macrobenthos: The lightness of being at Pacific methane seeps
Authors: Levin Lisa A. , Michener Robert H.
Published: June 2010

The importance of chemosynthetic nutritional pathways was examined for macrofaunal invertebrates (≫300 µm) from methane seeps in the Gulf of Alaska (4,413–4,443 m), on the Oregon margin (590 m), and on the northern California slope [Eel River margin] (520 m) by use of natural abundance stable isotopic data. Seep macrofauna exhibited lighter Δ13C and Δ15N values than those in nonseep sediments, but isotopic signatures varied among seep sites. Macrofaunal isotopic signatures indicated chemosynthetically fixed carbon sources with a significant contribution from methane‐derived carbon (MDC) in macrofauna from sediments of pogonophoran fields (average Δ13C, 246.44‰, 32%–51% MDC) and Calyptogena phaseoliformis beds (average Δ13C, 240.89‰, 12%–40% MDC) in the Gulf of Alaska and in microbial mat sediments on the Oregon margin (average Δ13C, 243.80‰, 20%–44% MDC). Lesser influence of MDC was noted in macrofauna from sediments of Calyptogena pacifica beds on the Oregon (average Δ13C, 233.38‰, 0%–27% MDC) and California ( Δ13C, 225.10‰, 0%‐22% MDC) margins and from California microbial mat sediments ( Δ13C, 222.23‰, 0%–5% MDC). Although most macrofauna appeared to be heterotrophic, light Δ15N and Δ13C values together provided evidence for chemoautotrophic symbioses in selected taxa. Carbon isotopic signatures were consistent with consumption of methane‐oxidizing archaea by some dorvilleid polychaetes (Δ13C, 290.62‰ and 273.80‰) and with grazing on filamentous sulfur bacteria by gastropods and polychaetes from the Oregon and California seeps. The importance of chemosynthetic trophic pathways varies regionally and among microhabitats, taxonomic groups, and feeding guilds.
Testing for toxic effects of prey on zooplankton using sole versus mixed diets
Authors: Colin Sean P. , Dam Hans G.
Published: June 2010

Negative effects of prey species on consumers could be due to deterrence, nutritional insufficiency, or toxicity of the prey. These effects can be discerned in experiments in which the suspect prey is offered to the consumers in a food mixture containing another prey item that is not toxic and in which the ingestion rates on the prey and the grazers’ responses (e.g., egg production) are measured. We used this framework to determine whether several algae that have been reported to have harmful effects on grazers (Prorocentrum minimum, low‐and high‐toxin Alexandrium sp., Heterosigma carterae, Thalassiosira rotula, and Phaeodactylum tricornutum) are toxic to females of the calanoid copepod Acartia tonsa. Ingestion, egg production, and egg‐hatching rates were measured for A. tonsa offered sole diets of the suspect alga and mixed diets containing the suspect alga and a control alga (the green flagellate Tetraselmis sp.) at an ecologically relevant concentration (250 µg C L-1) and duration (3 d). With the exception of the Alexandrium strain with the high‐toxin content (16.3 pgSaxitoxin [pgSTX] equivalents cell21), none of the diets studied can be considered toxic. The high‐toxin Alexandrium reduced A. tonsa’s total ingestion rate, and thus egg production, as the proportion of Alexandrium increased in the diet. A. tonsa exhibited significantly reduced ingestion and egg production rates when feeding on sole food diets of H. carterae and P. tricornutum relative to the mixed food diets. However, a comparison of ingestion rates among the diet mixtures revealed that H. carterae and P. tricornutum acted as feeding deterrents when provided as sole foods. These results stress the importance of using mixed food diets when examining putative toxic effects of preys on consumers.
Palatability of marine macro‐holoplankton: Nematocysts, nutritional quality, and chemistry as defenses against consumers
Authors: Bullard Stephan G. , Hay Mark E.
Published: June 2010

Chemical defenses against consumers have been hypothesized to be common among marine macro‐holoplankton, but few studies have assessed macro‐holoplankton susceptibility to predators or the traits affecting palatability. We used generalist fishes to determine the palatability of fresh tissues, freeze‐dried homogenates, and chemical extracts from 19 species of macro‐holoplankton. Fishes rejected fresh tissues of all the cnidarians, ctenophores, and cyanobacteria we examined but consumed salp and chaetognath tissues. In contrast, fishes consumed homogenates and chemical extracts of all macro‐holoplankton except for the cyanobacterium Trichodesmium sp. We examined nematocysts and low nutritional quality as mechanisms causing rejection of fresh tissues. Once nematocysts were deactivated, fishes consumed cnidarian tentacles, indicating that nematocysts served as defenses. The nutritional quality of macro‐holoplankton varied almost 500‐fold among species and was strongly bimodal, with most macroholoplankton species having ≪0.7 mg soluble protein ml-1 or ≫7 mg ml-1. In laboratory assays, there was a significant positive relationship between the nutritional quality of artificial foods and their acceptability to fishes. In field assays, reef fishes avoided experimental foods that had a protein content similar to low‐quality macroholoplankton but fed rapidly on higher quality foods. Furthermore, macro‐holoplankton that were high in protein content possessed defensive traits that low‐protein species lacked. Although fresh tissues of most macro‐holoplankton were rejected by generalist fishes, we found evidence of chemical defense only in a cyanobacterium. Thus, chemical defenses were rare among macro‐holoplankton, and rejection for ≫90% of the species we assessed was due to nematocysts or low nutritional quality.
Preservation of amino acids from in situ‐produced bacterial cell wall peptidoglycans in northeastern Atlantic continental margin sediments
Authors: Grutters Mark , van Raaphorst Wim , Epping Eric , Helder Willem , de Leeuw Jan W. , Glavin Daniel P. , Bada Jeffrey
Published: June 2010

In this study we present the results of total hydrolysable amino acids (THAA) and amino acid D/L‐enantiomers in northeastern Atlantic continental margin sediments. There is increasing evidence that intrinsically labile amino acids are present in old marine sediments as part of a refractory network of peptide‐like material. We used amino acid enantiomers to identify the contribution of amino acids from bacterial cell walls to THAA in organic matter ranging from relatively young to 18,000 yr old. The ratio of D/L‐amino acids increased with depth in the sediment mixed layer. Application of a transport‐racemization‐degradation model excludes a significant production of D‐amino acids by racemization and implies in situ bacterial production as the main source. Amino acids associated with a refractory pool of bacterial cell walls could account for approximately one third of the THAA deeper in the sediments. We propose that in situ bacterial production and the primary flux of labile organic matter from the water column result in a small but highly reactive pool of amino acids in the surface mixed sediment only, whereas amino acids associated with refractory cell walls persist in marine sediments.
A comment on the use of flushing time, residence time, and age as transport time scales
Authors: Monsen Nancy E. , Cloern James E. , Lucas Lisa V. , Monismith Stephen G.
Published: June 2010

Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real‐world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non‐steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.
Inhibition of growth and photosynthesis of the dinoflagellate Peridinium gatunense by Microcystis sp. (cyanobacteria): A novel allelopathic mechanism
Authors: Sukenik Assaf , Eshkol Rachel , Livne Alexander , Hadas Ora , Rom Meir , Tchernov Dani , Vardi Assaf , Kaplan Aaron
Published: June 2010

We describe a novel allelopathic interaction whereby the cyanobacterium Microcystis sp. inhibits photosynthesis in the freshwater dinoflagellate Peridinium gatunense by abolishing its internal carbonic anhydrase activity. Our analysis indicated a positive correlation between the winter presence of Microcystis and the timing of the annual spring bloom of Peridinium in Lake Kinneret (Sea of Galilee, Israel). Microcystis severely inhibited the growth of Peridinium in mixed laboratory cultures. This was attributed to the excretion of allelopathic substances rather than to successful competition for nutrients. Microcystis‐free spent medium (MFSM) inhibited steady‐state photosynthesis of Peridinium, as indicated by the reduced rate of oxygen evolution and by a suppressed fluorescence signal. Boosting the inorganic carbon concentration to 25 mmol L−1, i.e., 10‐fold higher than essential to saturate photosynthesis in the absence of MFSM, partially restored the photosynthetic capacity. MFSM‐treated Peridinium cells accumulated a larger internal inorganic carbon pool concomitantly with reduced accumulation of photosynthetic products. The MFSM slowed the hydration rate of CO2 (assessed from the rate of 18O exchange between 13C18O2 and water), indicating that the activity of an internal carbonic anhydrase was severely depressed. Although the nature of the active component in the MFSM that inhibits CA activity has yet to be identified, the ecological consequences of its excretion to the water body are emerging as a potent allelopathic substance that may control the development of phytoplankton competitors. We propose that its allelopathic activity could control the fate and succession of the P. gatunense bloom in Lake Kinneret.
Microbial glucose uptake and growth along a horizontal nutrient gradient in the North Pacific
Authors: Skoog Annelie , Whitehead Kenia , Sperling Frank , Junge Karen
Published: June 2010

The quantitative role of carbon‐rich compounds for bacterial carbon demand can vary with nutrient availability. This study is the first to investigate the effect of nutrient concentrations on bacterial uptake of a carbon‐rich compound (glucose) along a naturally occurring nutrient gradient. Seawater was collected from varying depths at six stations across the nutrient gradient between the nutrient‐poor North Pacific gyre and the nutrient‐rich sub‐ Arctic gyre. Ambient concentrations of free glucose, glucose uptake, bacterial production, and nutrient concentrations were determined across the gradient. Incubations were carried out to determine the effect of nutrient additions on glucose uptake and bacterial production. Samples from the northern, nutrient‐rich end of the transect had high glucose uptake rates and high bacterial production in surface waters. The northern stations also showed rapid turnover of the glucose pool. At the southern stations, glucose uptake rates, bacterial growth rates, and fractional glucose turnover were lower. At these stations, glucose uptake increased when inorganic nutrients and amino acids were added. The variations in glucose uptake indicate that microbial uptake of nitrogen‐ and phosphorus‐poor organic material depends on the availability of nitrogen and phosphorus from other sources.
The magnitude of spring bacterial production in the North Atlantic Ocean
Authors: Ducklow H. W.. , Kirchman D. L. , Anderson T. R.
Published: June 2010

Dissolved organic carbon (DOC), a major reservoir in the ocean carbon cycle, is produced by a profusion of plankton sources and processes but is consumed mainly by bacterioplankton. Thus bacterial metabolism regulates the entry of DOC into the longer scale global carbon cycle. Bacterial production (BP) is the routinely measured quantity for evaluating the roles of bacteria in carbon cycling. However BP cannot be measured directly and instead is estimated from related metabolic processes requiring the use of poorly constrained conversion factors. BP, and thus the total carbon utilization, are potentially uncertain by a factor of two or more. In the North Atlantic Bloom Experiment (NABE), BP was estimated to be about 30% of the simultaneous particulate primary production (PP), with some daily estimates exceeding 50%. Here we reassess these estimates, synthesizing knowledge and understanding of plankton dynamics gained since the 1989 NABE study. Daily BP derived from six different conversion factors averaged 20% of PP but ranged from 3 to 68%. The coupling of BP to PP was not consistent with either short‐term cycling of labile DOC (hours) nor with much longer term cycling of semilabile DOC (seasons). Trophodynamic processes, including release of DOC from phytoplankton, by themselves could have maintained BP at about 15% of PP. Use of decomposing POC or previously accumulated semilabile DOC could each have supported some additional increment of BP for brief periods. Both reconsideration of observations and model results indicated that higher estimates of BP exceeding 20% of PP could not be supported without extraordinary and prolonged inputs of allochthonous carbon. Recent assertions of high BP in the tropics and other oceanic regimes should be considered carefully, especially if external subsidies are not obvious.
Utilization of marine sedimentary dissolved organic nitrogen by native anaerobic bacteria
Authors: Guldberg Lise Bonne , Finster Kai , Jørgensen Niels O. G. , Middelboe Mathias , Lomstein Bente Aa.
Published: June 2010

Bioavailability and chemical composition of dissolved organic nitrogen (DON) in marine pore water were followed and related to bacterial activity in a 14–d anoxic decomposition experiment. For the experiment 0.2–µm filtered pore water from a coastal marine sediment was inoculated with native sediment bacteria. The initial composition of DON was characterized by a high contribution of dissolved free amino acids (DFAA), dissolved combined amino acids (DCAA), and urea, which together accounted for 82% of the DON pool. During the experiment, 54% of the DON was used by bacteria, indicating that DON was readily available to bacterial degradation. The consumption of DFAA and DCAA accounted for more than half of the DON consumed. The unidentified DON pool accounted for 33% of the net DON consumption, and the unidentified DON pool was fully depleted by the end of the experiment. Systematic changes in the amino acid composition occurred with time of incubation, as demonstrated by use of a principal component analysis based on the mole percent contribution of amino acids. The results indicated that amino acids of both the DFAA and the DCAA pools were useful indicators of the diagenetic state of DON. The present study presents the first direct evidence of short‐term (within 14 d) changes in DFAA and DCAA of the DON pool. These changes were similar to decompositional changes in the molecular composition of amino acids observed in traditional studies of bulk sediment diagenesis.
Effects of ultraviolet‐B radiation and vertical mixing on nitrogen uptake by a natural planktonic community shifting from nitrate to silicic acid deficiency
Authors: Fouilland Eric , Gosselin Michel , Mostajir Behzad , Levasseur Maurice , Chanut Jean-Pierre , Demers Serge , de Mora Stephen
Published: June 2010

We investigated the combined effects of mixing regimes and ultraviolet‐B radiation (UVBR: 280–320 nm) on the uptake of nitrate, ammonium, and urea by an estuarine phytoplankton community during a 10‐d mesocosm experiment in July 1997. The experiment was conducted in eight mesocosms (1,500 liters each) subjected to varying conditions of UVBR and mixing: (1) natural UVBR and fast mixing, (2) enhanced UVBR and fast mixing, (3) natural UVBR and slow mixing, and (4) enhanced UVBR and slow mixing. The study was carried out during a typical midsummer period of low nutrient concentrations. Throughout the experiment, the phytoplankton community was dominated by a mixed community composed mainly of centric diatoms, cyanobacteria, and prymnesiophytes, with larger algal cells (>5 µm) representing >70% of the total chlorophyll a biomass. The phytoplankton nutrient status changed over the experiment. Algal cells were nitrate‐deficient until the occurrence of a nitrification event on day 7, and then became silicic acid‐deficient. Mesocosms with different mixing rates showed significant differences in ambient nutrient concentrations, nitrogen uptake rates, and phytoplankton species composition. In general, no significant difference was detected between the N transport rates from samples incubated close to the surface and close to the bottom of the mesocosms, and no difference was detected between the UVBR treatments on all the other studied biological and chemical variables measured during the experiment. It is only under the slow mixing regime that the enhanced UVBR treatments significantly depress both the transport and the chlorophyll a—specific transport rates of dissolved organic nitrogen (urea). The UVBR effects observed only in the slow mixing regime could be a consequence of an inherent difference in the uptake capacity of the different communities under the two mixing regimes. Both nutrient conditions and mixing regime influenced the natural phytoplankton physiology and composition toward a community more sensitive to UVBR enhancement under a slower mixing regime.
Diatom—chemistry relationships in Yellowstone Lake (Wyoming) sediments: Implications for climatic and aquatic processes research
Authors: Interlandi Sebastian J. , Kilham Susan S. , Theriot Edward C.
Published: June 2010

We analyzed sediment elemental composition (C, N, P, and Si) and planktonic diatom fossils from the top 32 cm of a short core (55 cm) from Yellowstone Lake (Wyoming), tracking deposition from about 1650 to 1998. Associations between fossil communities and sediment chemistry were measured by rank‐order correlation to gauge decadal scale relationships between lake chemistry and phytoplankton community composition. Strong associations were found between the abundance of individual diatom species and the chemical composition of sediments, suggesting that sediment chemistry can directly track the elemental composition of seston. Among three fossil measures (relative frustule abundance, relative biovolume, and absolute biovolume), associations between sediment chemistry and relative biovolume were strongest. We then compared measures and trends in sediment elemental composition to in‐lake seston chemistry to assess transport processes that alter sediment composition relative to source material. On the basis of elemental stoichiometry, sediments were enriched in P and depleted in C and N compared with seston. Trends of increasing C and N accumulation along with decreasing Si accumulation were consistent with patterns of increasing productivity, increasing lake N levels, and decreasing dominance of diatoms, respectively. A sharp increase in sediment C:N ratio, with a decrease in diatom absolute biovolume and absolute C and N levels, was associated with a prolonged drought in the 1930s. These trends suggest alteration of ecosystem properties by a combination of climatic variation and increasing N availability, adding complexity to larger goals of climatic reconstruction by diatom—nutrient chemistry—climate transfer functions in large lakes of the region.
Coupled nitrification‐denitrification in autotrophic and heterotrophic estuarine sediments: On the influence of benthic microalgae
Authors: Nils Risgaard-Petersen
Published: June 2010

Field data obtained from 18 European estuaries using the isotope pairing technique were analyzed for trends in relationship between activity of benthic microalgae and coupled nitrification‐denitrification. Kruskal‐Wallis tests and analyses of covariance performed on the field dataset showed strong statistical evidence for the hypothesis that sediments colonized by microalgae whose activity exceeds community respiration display lower rates of coupled nitrification‐denitrification than do heterotrophic sediments. In fully heterotrophic sediments, 90% of the measurements fell within the range 0–92 µmol N m−2 h−1 with a median of 20.3 µmol N m−2 h−1. In highly autotrophic sediments, 90% of the measurements fell within the range 0‐34 µmol N m−2 h−1, and the median was 4.2 µmol N m−2 h−1. The hypothesis was tested experimentally using 15N and microsensor (NO3−) techniques in prepared microcosms with and without algal activity. The results of the experimental studies were consistent with the hypothesis derived from the field data analysis. For the 15N study, coupled nitrification‐denitrification in alga‐colonized sediments was between 4 and 51% of the activity in sediments without algae activity, depending on the N load. For the microsensor study, there was no indication of net NO3− production in alga‐colonized sediments before addition of NH4−. In contrast, NO3− accumulated in the oxic zone of a similar alga‐free sediment. The experiments furthermore showed that compared to heterotrophic sediment, the presence of active microalgae might reduce the population of nitrifying bacteria capable of having an active metabolism. These bacterial populations could display diurnal variations in activity correlated with the diurnal variations in O2 penetration depth, however. The results showed that induction of nitrogen limitation of the nitrifying bacteria population is a major controlling mechanism of coupled nitrification‐denitrification in alga‐colonized sediments.
The effect of the sinking spring diatom bloom on digestive processes of the cold‐water protobranch Yoldia hyperborea
Authors: Stead1 Robert A. , Thompson Raymond J.
Published: June 2010

Periodic sampling from April 1997 to December 1998 of a population of the deposit‐feeding protobranch Yoldia hyperborea from the deep depositional zone (250 m) of Conception Bay, Newfoundland, indicated that this species was exposed to subzero temperatures (−/0.63°C) throughout the year. However, the standing stock of phytoplankton in the photic zone showed strong seasonal fluctuations with primary peaks always occurring in April (4.26 and 5.09 µg L−1 chlorophyll a in 1997 and 1998, respectively). In addition, sediment chlorophyll a started to increase (from a low of ~6 ng mg−1 dry weight of sediment) as the sinking of a smaller, secondary bloom, reached the bottom in the first 2 months of 1997 and 1998, although higher concentrations were reached by mid‐April and May 1997 (21.32 ng mg−1 sediment) and remained relatively high until February 1998. An increase of digestive cell height and protein content occurred as soon as sinking organic material from the spring bloom reached the benthic zone, suggesting storage of metabolic energy during spring and summer. Sharp increases in digestive enzyme activity occurred primarily in early spring of each year, coinciding with the timing of the primary spring bloom fallout, suggesting activation of the formerly depressed digestive system after a prolonged period of low food availability (i.e., late summer to autumn). Results suggest that Y. hyperborea strongly depends on the input of fresh algal material despite the high availability of organic matter in the sediment.
Beyond bulk properties: Responses of coastal summer plankton communities to nutrient enrichment in the northern Baltic Sea
Authors: Lignell Risto , Seppälä Jukka , Kuuppo Pirjo , Tamminen Timo , Andersen Tom , Gismervik Ingrid
Published: June 2010

Enclosure experiments with all combinations of NH4 and PO4 treatments were carried out in the northern Baltic coastal zone during the post‐spring bloom growth season. Empirical models were used to identify the important 3‐d treatment effects on the state and process variables governing the main plankton compartments. Moreover, dilution experiments revealed the main nutrient sources for algal growth (external pools, intracellular stores, remineralization) and estimated phytoplankton growth and feeding loss rates. Maximal (nutrient‐replete) algal community growth rates were 0.1‐0.7 d‐1. Small (2‐10 µm) algae grew fast (0.5‐1.5 d‐1), whereas the abundant trichal blue‐green algae grew very slowly. Ciliates showed a clear increase in units with positive algal response at minimum grazing estimates of 0.05‐0.3 d‐1. Initial inorganic N: P ratios were consistently low (<4, wt/wt), and internal stores and remineralization were the most important nutrient sources for algae. During P‐replete early summer, phytoplankton showed N limitation of biomass, rather than growth rate, in all (<2, 2‐10, >10 µm) size fractions. During the mineral N‐ and P‐deplete late summer bloom of trichal blue‐green algae, the positive P responses of chlorophyll a‐normalized 14CO2 fixation and growth rates indicated physiological P deficiency of the whole algal assemblage, but only a combined N and P addition evoked an increase in algal biomass. In early summer, low inorganic N: P ratios reflected N limitation, as commonly found in estuaries, but later, the indicative value of this ratio evaporated, evidently because of gaseous N2 fixation by blue‐green algae.
Chemical defense in the microplankton I: Feeding and growth rates of heterotrophic protists on the DMS‐producing phytoplankter Emiliania huxleyi
Authors: Strom Suzanne , Wolfe Gordon , Holmes Jan , Stecher Hilmar , Shimeneck Carolyn , Sarah Lambert
Published: June 2010

In this study, the hypothesis that Emiliania huxleyi, a cosmopolitan, bloom‐forming coccolithophorid, produces chemical defenses against protist grazers was tested using four axenic strains of the alga. The putative chemical defense involves the cleavage of dimethylsulfoniopropionate (DMSP) by the enzyme DMSP lyase to yield dimethylsulfide (DMS) and acrylate. Out of six tested protist grazer species, five (including ciliates and heterotrophic dinoflagellates) showed lower feeding rates on E. huxleyi strains with high DMPS lyase activity than on low‐lyase strains. Reductions in population growth rate were consistent with feeding reductions. These results suggest that high levels of DMSP lyase activity somehow promote reduced palatability, although covariation of E. huxleyi protein and carbohydrate content with DMSP lyase activity meant that prey “nutritional quality” could not be ruled out as a contributing factor. Additional experiments with the heterotrophic dinoflagellate Amphidinium longum demonstrated that (1) individuals need not ingest E. huxleyi cells to receive the “don't eat me” cue and (2) exposure to high‐lyase E. huxleyi cells confers no harmful consequences in terms of the ability to feed and grow on alternate phytoplankton prey. Thus, factors promoting reduced grazing on high‐lyase E. huxleyi are hypothesized to constitute signals rather than acute toxins. Furthermore, although cell surface carbohydrates (as assayed by lectin binding) showed few differences among strains, results of feeding studies indicate that the deterrent signal resides on the cell surface or in the near‐cell dissolved phase. Behavior responses to such cues might play an important role in the outcome of encounters between protist grazers and their prey, with profound consequences for planktonic community structure.
Phylogeographical patterning in Daphnia ambigua: Regional divergence and intercontinental cohesion
Authors: Hebert Paul D. N. , Witt Jonathan D. S. , Adamowicz Sarah J.
Published: June 2010

Daphnia ambigua, one of the most broadly distributed members of its genus, occurs in Europe as well as in North and South America. This investigation examines diversity in two mitochondrial genes, COI and 12S rDNA, to ascertain the geographical distribution of variation in this species. The results establish that North American D. ambigua are separable into four phylogroups with an average of 4% mtDNA sequence divergence. One of these groups is dominant, occupying Mexico and the central United States, whereas the other groups are restricted to the Atlantic or Pacific coasts. Their distributional centroids coincide with refugial areas identified in prior studies, reinforcing evidence that the Appalachian and West Coast ranges have been important in the isolation of zooplankton lineages. Gene exchange, mediated by migratory birds whose flyways are structured by these mountains, is likely instrumental in maintaining north‐south cohesion within each phylogroup. European populations of D. ambigua are closely allied to those from the eastern United States, a result concordant with their presumed recent introduction from North America. By contrast, South American populations last shared an ancestor with North American lineages approximately 2 million yr ago. The phylogeographic information now available suggests that topographic barriers generate predictable patterns of population divergence in zooplankton species and that allopatric speciation has played an important role in their diversification.
Trophic relationships among Southern Ocean copepods and krill: Some uses and limitations of a stable isotope approach
Authors: Schmidt Katrin , Atkinson Angus , Stübing Dorothea , McClelland James W. , Montoya Joseph P. , Voss Maren
Published: June 2010

The use of stable isotopes to study food webs has increased rapidly, but there are still some uncertainties in their application. We examined the δ15N and δ13C values of Antarctic euphausiids and copepods from the Polar Front, Lazarev Sea, and Marguerite Bay against their foodweb baseline of particulate organic matter (POM). Interpretations of trophic level were helped by comparison with other approaches and by calibration experiments with Euphausia superba fed known diets. Results for well‐known mesozooplankters (e.g., Calanoides acutus and Metridia gerlachei) were internally consistent and corresponded to those derived from independent methods. This gave confidence in the isotope approach for copepods and probably larval euphausiids. Among the dominant yet poorly known species, it suggested mainly herbivory for Rhincalanus gigas but omnivory for Calanus simillimus and furcilia larvae of Thysanoessa spp. and Euphausia frigida. The δ15N values of adult copepods were up to 3‰ higher than those of early copepodites, pointing to ontogenetic shifts in diet. In the Lazarev Sea in autumn, the isotopic signals of E. superba larvae suggested pelagic, mainly herbivorous, feeding rather than feeding within the ice. In contrast to the mesozooplankton, some anomalous results for postlarval krill species indicated problems with this method for micronekton. The experiments showed that postlarval E. superba did not equilibriate with a new diet within 30 d. We suggest that the slower turnover of these larger species, partly in combination with their ability to migrate, has confounded trophic effects with those of a temporally/spatially changing food‐web baseline. Interpretations of food sources of micronekton could be helped by analyzing their molts or fecal pellets, which responded faster to a new diet.
Light in shallow waters: A brief research review
Authors: Ackleson Steven G.
Published: June 2010

Until recently, optical processes in shallow water, where a large portion of solar photons penetrate to the ocean floor, has received little attention outside of a relatively small number of modeling and remote sensing investigations. In the open ocean, scales of variability in relation to optical attenuation length often permit the treatment of the inwater light field as a one‐dimensional, depth‐dependent problem. In shallow waters hosting productive benthic ecosystems, such as coral reefs or seagrasses, the in‐water light field is often three‐dimensional in character. In the past decade, quantitative investigations of benthic optical properties and the resulting shallow‐water light field have been conducted, fueled by a variety of new sensors designed specifically to address the shallow water problem. Recent publications, as well as the papers contained in this volume, illustrate the rich diversity and interdisciplinary nature of shallow‐water optical problems and highlight important issues that should attract closer attention in the future.
Effects of optically shallow bottoms on upwelling radiances: Bidirectional reflectance distribution function effects
Authors: Mobley Curtis D. , Zhang Hao , Voss Kenneth J.
Published: June 2010

Radiative transfer simulations were carried out for a variety of measured and modeled benthic bidirectional reflectance distribution functions (BRDFs), incident lighting conditions, bottom depths, and water inherent optical properties. These simulations quantify the errors that occur in predictions of above‐surface remote‐sensing reflectances and in‐water upwelling radiances if non‐Lambertian ocean bottoms are replaced by Lambertian bottoms having the same irradiance reflectance. We found that when computing water‐leaving radiances, non‐Lambertian BRDFs can be replaced by a Lambertian BRDF having the same irradiance reflectance, with errors seldom greater than 10% and often much less, for considerations of above‐surface ocean‐color remote sensing by Ocean Portable Hyperspectral Imager for Low‐Light Spectroscopy (Ocean PHILLS) or similar systems using near‐nadir viewing directions. The crucial measurement to make in characterizing the reflectance properties of a benthic surface for such applications is the spectral irradiance reflectance.
The influence of bottom morphology on reflectance: Theory and two‐dimensional geometry model
Authors: Zaneveld J. Ronald V. , Boss Emmanuel
Published: June 2010

The reflectance of the bottom is of importance when interpreting optical data in shallow water. Closure studies of radiative transfer, interpretation of laser line scanner data, lidar, and remote sensing in shallow waters require understanding of the bottom reflectance. In the Coastal Benthic Optical Properties experiment (CoBOP), extensive measurements of the material reflectance (reflectance very close to the bottom) were made. Far field reflectance will be needed in carrying out closure of the radiative transfer model and observed radiometric and inherent optical properties. The far field reflectance is the bottom reflectance that includes the effect of bottom morphology (such as sand ripples) as well as the material reflectance. We present here a first‐order analytical model to derive the relationship between the material and far field reflectances. We show that the effective reflectance of the bottom is proportional to the average cosine of the bottom slope. Using a simple two‐dimensional geometry without scattering and absorption, we show that errors in ignoring the bottom morphology can lead to overestimations of the far field reflectance on the order of 30%.
Changes in the fluorescence of the Caribbean coral Montastraea faveolata during heat‐induced bleaching
Authors: Zawada1 David G. , Jaffe Jules S.
Published: June 2010

In order to evaluate the response of commonly occurring green and orange fluorescent host‐based pigments, a thermal stress experiment was performed on specimens of the Caribbean coral Montastraea faveolata. Seven paired samples were collected from a small oceanic reef near Lee Stocking Island in the Bahamas. Seven of the fourteen corals were subjected to elevated temperatures for 28 d, followed by a recovery period lasting 53 d. Throughout the experiment, high‐resolution (~400 µm pixel−1) multispectral images of induced fluorescence were recorded at wavelengths corresponding to the green and orange host pigments, plus chlorophyll. These images revealed that the fluorescence of both host pigments was concentrated at polyp centers and declined by 70–90% in regions between polyps. Chlorophyll fluorescence, however, was distributed almost uniformly across the entire coral surface, but with decreases of 10–30% around polyp centers. A normalized difference ratio between the green and orange pigments (GO ratio) was developed to facilitate comparison with chlorophyll fluorescence as a bleaching indicator. Analysis showed a high correspondence between a sustained GO ratio of less than zero and the death of corals. Finally, this ratio was resistant to contamination from other sources of chlorophyll fluorescence, such as filamentous
Optical remote sensing of benthic habitats and bathymetry in coastal environments at Lee Stocking Island, Bahamas: A comparative spectral classification approach
Authors: Louchard Eric M. , Reid, R. Pamela , Stephens F. Carol , Davis, Curtiss O. , Leathers Robert A. , T. Valerie Downes
Published: June 2010

Remote sensing is a valuable tool for rapid identification of benthic features in coastal environments. Past applications have been limited, however, by multispectral models that are typically difficult to apply when bottom types are heterogeneous and complex. We attempt to overcome these limitations by using a spectral library of remote sensing reflectance (Rrs), generated through radiative transfer computations, to classify image pixels according to bottom type and water depth. Rrs spectra were calculated for water depths ranging from 0.5 to 20 m at 0.5− to 1.0−m depth intervals using measured reflectance spectra from sediment, seagrass, and pavement bottom types and inherent optical properties of the water. To verify the library, computed upwelling radiance and downwelling irradiance spectra were compared to field measurements obtained with a hyperspectral tethered spectral radiometer buoy (TSRB). Comparisons between simulated spectra and TSRB data showed close matches in signal shape and magnitude. The library classification method was tested on hyperspectral data collected using a portable hyperspectral imager for low light spectroscopy (PHILLS) airborne sensor near Lee Stocking Island, Bahamas. Two hyperspectral images were classified using a minimum‐distance method. Comparisons with ground truth data indicate that library classification can be successful at identifying bottom type and water depth information from hyperspectral imagery. With the addition of diverse sediments types and different species of corals, seagrass, and algae, spectral libraries will have the potential to serve as valuable tools for identifying characteristic wavelengths that can be incorporated into bottom classification and bathymetry algorithms.
Emission location dependent ozone depletion potentials for very short-lived halogenated species
Authors: Pisso I. , Haynes P. H. , Law K. S.
Published: June 2010

Abstract. We present trajectory-based estimates of Ozone Depletion Potentials (ODPs) for very short-lived halogenated source gases as a function of surface emission location. The ODPs are determined by the fraction of source gas and its degradation products which reach the stratosphere, depending primarily on tropospheric transport and chemistry, and the effect of the resulting reactive halogen in the stratosphere, which is determined by stratospheric transport and chemistry, in particular by stratospheric residence time. Reflecting the different timescales and physico-chemical processes in the troposphere and stratosphere, the estimates are based on calculation of separate ensembles of trajectories for the troposphere and stratosphere. A methodology is described by which information from the two ensembles can be combined to give the ODPs. The ODP estimates for a species with a 20 d lifetime, representing a compound like n-propyl bromide, are presented as an example. The estimated ODPs show strong geographical and season variation, particularly within the tropics. The values of the ODPs are sensitive to the inclusion of a convective parametrization in the trajectory calculations, but the relative spatial and seasonal variation is not. The results imply that ODPs are largest for emissions from South and South-East Asia during Northern Hemisphere summer and from the Western Pacific during Northern Hemisphere winter. Large ODPs are also estimated for emissions throughout the tropics with also non-negligible values extending into northern mid-latitudes particularly in the summer. These first estimates, which include some simplifying assumptions, show larger ODP values than previous studies, particularly over Southern Asia, suggesting that emissions of short-lived halogen source gases in certain geographical regions could have a significant impact on stratospheric ozone depletion.
Landslide damage assessment using the Support Analysis Framework (SAF): the 2009 landsliding event in Calabria (Italy)
Authors: Petrucci O. , Pasqua A. A. , Gullà G.
Published: June 2010

Abstract. In this paper, a simplified methodological approach is used to assess damage indices related to landslide phenomena that occurred in Calabria (Italy) between November 2008 and January 2009. This approach, which was designed for and applied to single landslides, uses the Support Analysis Framework (SAF), a procedure containing the elements that can be damaged by a landslide grouped in categories. In this paper, we test wide-ranging use of the SAF on a number of landslides, assessing landslide damage on a municipal scale to get a final estimate of the amount of damage caused by all of the landslides that occurred in a selected municipality. Data regarding the damage caused by landslides were gathered from the press. Daily newspapers were systematically collected and elaborated to assess direct, indirect and intangible damage caused during the abovementioned period by a rainfall-triggered landsliding event. In the paper, regional- and provincial-scale results are described, and the methodological approach is briefly described. The application of the proposed methodological approach to the 2009 landsliding event shows that the results can be used to summarise landslide damage from a complex event in order to better plan an intervention strategy at a regional, provincial or municipal scale. The availability of newspaper data during the event and the speed of the proposed approach allow for rapid location of the damaged sectors during the event, which will continuously upgrade the regional damage framework. This can all be done almost in "real time". For regional agencies, this framework can be a starting point to both manage the emergency and to acquire and interpret data giving a more detailed damage distribution so that a response can be organised. Moreover, based on the damage assessment, a characterisation of the landsliding event can also be carried out and used to describe the damage scenario occurring after each type of event.
Numerical study of a banded precipitation event over Italy
Authors: Malguzzi P. , Fantini M. , Buzzi A.
Published: June 2010

Abstract. Satellite images of 30 October 2008 show the development over north-central Italy of rainbands and multiple waves during a strong south-westerly wind episode associated with a deepening synoptic trough and cold front passage. The event was studied by means of the ISAC model chain constituted of the hydrostatic model BOLAM and the nested non-hydrostatic model MOLOCH at 1.1 km resolution. Diagnostics of model output was performed to reveal the physical origin of the dynamical features and precipitation field as simulated. Based on our results we propose a theoretical framework in which symmetric instability underlies some of the observed precipitation patterns.
Cyclic peptides as potential therapeutic agents for skin disorders
Authors: Namjoshi Sarika , Benson Heather A. E.
Published: June 2010

There is an increasing understanding of the role of peptides in normal skin function and skin disease. With this knowledge, there is significant interest in the application of peptides as therapeutics in skin disease or as cosmeceuticals to enhance skin appearance. In particular, antimicrobial peptides and those involved in inflammatory processes provide options for the development of new therapeutic directions in chronic skin conditions such as psoriasis and dermatitis. To exploit their potential, it is essential that these peptides are delivered to their site of action in active form and in sufficient quantity to provide the desired effect. Many polymers permeate the skin poorly and are vulnerable to enzymatic degradation. Synthesis of cyclic peptide derivatives can substantially alter the physicochemical characteristics of the peptide with the potential to improve its skin permeation. In addition, cyclization can stabilize the peptide structure and thereby increase its stability. This review describes the role of cyclic peptides in the skin, examples of current cyclic peptide therapeutic products, and the potential for cyclic peptides as dermatological therapeutics and cosmeceuticals. © 2010 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 94: 673–680, 2010.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
ChemInform Abstract: Electrochemical‐Hydrothermal Synthesis and Structure Determination of a Novel Layered Mixed‐Valence Oxide: BaV7O16×nH2O.
Authors: WANG X. , LIU L. , BONTCHEV R. , JACOBSON A. J.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: [P8Se18]6‐: A New Oligomeric Selenophosphate Anion with P4+ and P3+ Centers and Pyramidal [PSe3] Fragments.
Authors: CHONDROUDIS K. , KANATZIDIS M. G.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: The Binary Silicides Eu5Si3 and Yb3Si5 — Synthesis, Crystal Structure, and Chemical Bonding.
Authors: POETTGEN R. , HOFFMANN R.‐D. , KUSSMANN D.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Crystal and Electronic Structure of the Tetrahedral V4 Cluster Compounds GeV4Q8 (Q: S, Se).
Authors: JOHRENDT D.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Diaquacobalt Tetracyanonickelate Tetrahydrate.
Authors: NIU T. , CRISCI G. , LU J. , JACOBSON A. J.
Published: June 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.