Temporal shift in contribution of terrestrial organic matter to consumer production in a grassland river

1. We used stable isotopes to study the temporal (early summer versus autumn) pattern of use of terrestrial and aquatic sources of organic carbon by consumers in two bedrock‐confined reaches of a grassland river in New Zealand.
2. The major sources of organic carbon available to primary consumers were expected to be terrestrial leaf‐litter and biofilm from the stream channel. These putative carbon sources showed no significant change in mean δ¹³C between summer and autumn. Leaf litter (mean δ¹³C13C compared to biofilm (mean δ¹³C>?19.92).
3. In contrast to leaf litter and biofilm, the δ¹³C of consumers changed over time, being enriched in ¹³C in the autumn compared with early summer. Both the magnitude (>5‰ in some cases) and rapidity of this shift (< 3 months) was surprising.
4. A two‐source mixing model indicated that, during early summer, terrestrial carbon comprised> 50% of tissue carbon for 15 of the 17 taxa of aquatic consumers analysed. During autumn, terrestrial carbon comprised> 50% of the tissue carbon of only five of 25 taxa. Because the mean δ¹³C of putative food sources was consistent over time, the shift in δ¹³C values for consumers is attributed to a change in relative amounts of terrestrial and aquatic carbon available for consumption.
5. Because seston consists of a mixture of many particles of diverse origin, it may provide an integrated measure of catchment‐wide sources of organic matter entering a stream channel. Like the tissues of most consumers, mean δ¹³C values for seston showed a significant shift toward ¹³C enrichment. This indicated that the relative availability of terrestrial carbon decreased from summer to autumn.
6. The actual quantity of carbon contributed to the stream food‐web by this potential terrestrial–aquatic link is unknown. Although terrestrial carbon may comprise a high proportion of the tissue carbon of consumers prior to summer, the majority of secondary production (and carbon sequestration) probably occurs during early summer as a consequence of rising temperature and high quality food in the form of biofilm.     

The contribution of primary production to organic carbon content in Lake Onego

The influence of primary production (PP) on the dynamics of organic carbon in Lake Onego was analyzed. The daily, seasonal, and annual contribution of PP to the content of organic matter (OM) is assessed. It is shown that the contribution of the PP to the increase in the carbon content in the ecosystem is inconsiderable, while the allochthonous OM included in cycling by the bacterial link plays an important role.     

Halimeda biomass,growth rates and sediment generation on reefs in the central great barrier reef province

The average biomass ofHalimeda per m² of solid substratum increased progressively on a series of reefs situated at increasing distances from the shore in the central Great Barrier Reef. There was none on a reef close inshore, increasing to nearly 500 g m^?2 total biomass (?90% calcium carbonate) on an oceanic atoll system in the Coral Sea. The biomass measured contained 13 species ofHalimeda but was dominated by only two species,H. copiosa andH. opuntia, except on the atoll whereH. minima was dominant. Three sand-dwelling species were also present but did not occur anywhere in substantial quantities. Growth rates of the dominant species were measured bv tagging individual branch tips. A mean value of 0.16 segments d^?1 was recorded but 41% of the branch tips did not grow any new segments whilst only 1% grew more than one per day. The number of branch tips per unit biomass was very constant and has been used in conjunction with growth rates and biomass to calculate productivity rates, and thence sedimentation, in the lagoon of one of the reefs. Biomass doubling time of 15 d and production of 6.9 g dry wt m^?2 d^?1 are considerably higher than previously reported values forHalimeda vegetation and there was little seasonal change detected over a whole year. Those values indicate annual accretion of 184.9 g m^?2 year^?1 ofHalimeda segment debris over the entire lagoon floor (5.9 km²) of Davies Reef, equivalent to 0.13 mm year^?1 due toHalimeda alone, or 1 m every 1,892 years when other contributions to that sediment are taken into account.     

Community metabolism of a coral reef exposed to naturally varying dissolved inorganic nutrient loads

Daily community rates of calcification, photosynthesis and respiration were measured on a coral reef located in the Northern Red Sea, Gulf of Eilat, Israel between March 2000 and March 2002. This reef is exposed to seasonally varying levels of inorganic nutrient loading due to mixing and stratification of the adjacent open sea water column. Net production measurements were positively and linearly correlated with open sea nutrient levels, and the community photosynthesis to respiration ratio varied between 0.9 and 1.7 accordingly. Community calcification varied between 30 ± 20 and 60 ± 20 mmol C m⁻² day⁻¹ during summer and winter, respectively. Under increased nutrient loading the relation between community calcification and aragonite saturation state is suppressed by 30% on average. Both of these findings demonstrate the deleterious effects of nutrient loading on coral reefs.     

Distribution of dissolved organic carbon and nitrogen in a coral reef

Dissolved organic matter (DOM) concentrations in a fringing coral reef were measured for both carbon and nitrogen with the analytical technique of high-temperature catalytic oxidation. Because of high precision of the analytical system, not only the concentrations of dissolved organic carbon and nitrogen (DOC and DON, respectively) but the C:N ratio was also determined from the distribution of DOC and DON concentrations. The observed concentrations of DOC and DON ranged 57–76 and 3.8–5.6 μmol l⁻¹, respectively. The C:N ratios of the DOM that was produced on the reef flat were very similar between seagrass- and coral-dominated areas; the C:N ratio was 10 on average. The C:N ratio of DOM was significantly higher than that of particulate organic matter (POM) that was produced on the reef flat. Production rates of DOC were measured on the reef flat during stagnant periods and accounted for 3–7% of the net primary production, depending on the sampling site. The production rate of DON was estimated to be 10–30% of the net uptake of dissolved inorganic N in the reef community. Considering that the DOM and POM concentrations were not correlated with each other, a major source of the reef-derived DOM may be the benthic community and not POM such as phytoplankton. It was concluded that a widely distributed benthic community in the coral reef released C-rich DOM to the overlying seawater, conserving N in the community.     

Growth rate,ultrastructure and sediment contribution of Halimeda incrassata and Halimeda monile,Nonsuch and Falmouth Bays,Antigua, W.I.

Halimeda incrassata and Halimeda monile, the two dominant rhipsalian Halimeda, were evaluated behind a bank barrier reef, in a fringing reef lagoon and in an open lagoon. Growth was calculated in number of segments, weight of segments and turnover rate. More than 1800 plants were stained with Alizarin Red-S dye, yielding average number of segments/plant/day and g CaCO₃/m²/year for each of the above areas of 2.17/114, 1.43/65.7 and 1.6/56.9, respectively. Average weight CaCO₃/segment was 4 mg. SEM revealed ultrastructure of short and long unoriented aragonite crystals forming in new segments within 24 h and an effective holdfast system with filaments partially coated with carbonate fragments. Greatest growth occurred within thin to medium density grass beds. In Nonsuch Bay sediment production from these two species alone was 0.057 mm/year or 1 1/2 orders of magnitude less than estimates of the total production from all Halimeda species (1.01 mm/year) over the past 6745 years.     

Augmented coral reef monitoring using a stationary reef monitoring system

Coral reef monitoring is a reliable tool to assess the effect of climate change as corals are sensitive to increases in water temperatures between 30 °C and 35 °C resulting in bleaching - a whitening process when the corals lose their color and the reefs begin to die. Existing satellite-based monitoring products facilitate coral bleaching monitoring over large spatial scales, but their use in predicting local scale stress that influences the bleaching severity across reefs is limited. In this paper, we describe a Stationary Reef Monitoring System (SRMS) that monitors the time evolution of coral reefs through the photography of nearby coral clusters. Simultaneously, the SRMS measures and records environmental parameters such as temperature, solar irradiance (PAR), and salinity in the waters surrounding the coral colonies. When deployed in the sea, the SRMS detected a 0.1–0.4 °C variability in temperature between the in situ and satellite datasets. The SRMS uses color photography along with quantitative data on environmental parameters to monitor the health of corals and eliminates the need for physical/visual verification of coral health by a diver. By this approach, one can determine the stress thresholds of corals and identify the vulnerable and resilient reefs so as to prioritize conservation efforts.     

Influence of inorganic phosphate and organic buffers on cephalosporin production by Streptomyces clavuligerus

A high concentration of potassium phosphate (75–100 mM) stabilized pH and supported extensive growth of Streptomyces clavuligerus in a chemically defined medium; such a concentration also inhibited cephalosporin production. Although Tris buffer was found to have detrimental effects on growth and antibiotic production, 3-(N-morpholino)-propane sulfonate (MOPS) or 2-(N-morpholino)-ethane sulfonate (MES) buffer provided a nontoxic buffering system. In the presence of MOPS buffer, cephalosporin production was optimal at 25 mM phosphate, whereas higher concentrations of phosphate progressively inhibited antibiotic production up to 85% without modifying the pH pattern. MOPS buffer can be used to conduct fermentations at a relatively constant pH value in shake flasks.List of Non-Common Abbreviations MOPS 3-(N-morpholino)propane sulfonic acid - MES 2-(N-morpholino)ethane sulfonic acid     

Effect of organic and inorganic selenium sources in sow diets on colostrum production and piglet response to a poor sanitary environment after weaning

The objectives of this study were to determine the effect of the chemical form of selenium (Se) fed to sows (1) on production and immune quality of colostrum and (2) on piglet response to a deterioration of sanitary conditions after weaning. Twenty-two pregnant sows were assigned to receive a diet supplemented with 0.3 ppm Se from either sodium selenite (inorganic Se) or Se-enriched yeast (organic Se as Sel-Plex®; Alltech Inc., Nicholasville, KY, USA). Dietary treatments were applied during the last month of pregnancy and lactation. Blood samples were collected on sows before dietary treatment, on the day of weaning and 6 weeks later, and on three to five piglets within litters at birth, at weaning and 6 weeks post weaning. Whole blood was analysed for Se concentration. Colostrum samples were collected at 0, 3, 6 and 24 h post partum and milk samples on days 14 and 27 of lactation. Colostrum and milk were analysed for Se and immunoglobulin G (IgG) concentrations. At weaning, 40 pairs of littermate piglets were moved to rooms where sanitary conditions were good or purposely deteriorated. Piglets were reared individually and fed ad libitum. After 15 days, piglets and feed refusals were weighed and a blood sample was collected to measure plasma haptoglobin concentration. When sows were fed organic Se, Se concentrations were increased by 33% in colostrum (P < 0.05), 89% in milk (P < 0.001) and by 28% in whole blood of piglets at weaning (P < 0.001). Colostrum production during the 24 h after the onset of farrowing and IgG concentrations in colostrum and milk did not significantly differ between the two groups of sows. Weaned piglets reared in good sanitary conditions grew faster (P < 0.001) than piglets housed in poor conditions. Sanitary conditions did not influence mean plasma haptoglobin concentrations of piglets (P > 0.1). The source of Se fed to the dams did not influence piglet performance or haptoglobin concentrations after weaning. These findings confirm that, compared with inorganic Se, organic Se fed to the dam is better transferred to colostrum and milk, and consequently to piglets. They indicate that the Se source influences neither colostrum production nor IgG concentrations in colostrum, and that the higher Se contents of piglets does not limit the reduction of growth performance when weaning occurs in experimentally deteriorated sanitary conditions.     

Local auxin production: a small contribution to a big field

Auxin is a plant growth regulator involved in diverse fundamental developmental responses. Much is now known about auxin transport, via influx and efflux carriers, and about auxin perception and its role in gene regulation. Many developmental processes are dependent on peaks of auxin concentration and, to date, attention has been directed at the role of polar auxin transport in generating and maintaining auxin gradients. However, surprisingly little attention has focussed on the role and significance of auxin biosynthesis, which should be expected to contribute to active auxin pools. Recent reports on the function of the YUCCA flavin monooxygenases and a tryptophan aminotransferase in Arabidopsis have caused us to look again at the importance of local biosynthesis in developmental processes. Many alternative and redundant pathways of auxin synthesis exist in many plants and it is emerging that they may function in response to environmental cues.     

Current rectification in a tropical coral reef system

Acoustic Doppler current profiles (ADCP) and conductivity-temperature-depth (CTD) profiles were recorded in the Veracruz Reef System (VRS) to elucidate the effect of topography on current circulation and zooplankton distribution. Measurements showed the baroclinic behavior of the tropical coral reef system with vertical temperature and salinity gradients of 0.4°C m⁻¹ and 0.5 psu m⁻¹, respectively. Under sustained southerly wind conditions, a cyclonic eddy generated by subtidal and tidal current rectification was observed between the two groups of coral colonies studied. Current rectification was attributed to the shallowness of the coral colonies and to a small cape close to Anton Lizardo Village. The cyclonic eddy, with low surface temperature, produced an increment in the vertically integrated acoustic scattering volume (biovolume), suggesting that this is a high-productivity area.     

Phytoplankton and its contribution to primary productivity in two coral reef areas of French Polynesia

A study of phytoplankton productivity and related parameters was carried out in two fringing and barrier reef systems around Moorea island (Tiahura lagoon) and Tahiti (Vairao lagoon), Society Islands, during July–August 1974.In Tiahura lagoon, which is the narrower and the shallower, phytoplankton standing crop and production are extremely low; photosynthetic assimilation, as measured in situ by the ¹⁴C method, ranges from 4 to 27 mg C m^?2 day^?1, presumably less than in the impoverished open ocean, but it is surprisingly high at a station just outside the barrier reef (645 mg C m^?2 day^?1) as the result of some island mass effect. As compared to the latter station, the lagoon shows a ten-times increase in particle content and glucose uptake, and a higher percentage of decomposition products of plant pigments. These data support the concept that, in such environments where benthic primary producers prevail, phytoplankton may have lost its ‘usual’ rôle in the aquatic food web.Vairao lagoon, a deeper and wider one, subjected to a greater extent to land fertilization, is more productive (103–420 mg C m^?2 day^?1). Considering this difference, as well as the considerable range of phytoplankton production in coral reef areas of the world, the need for a trophic classification of such ecosystems is emphasized.     

The contribution of the male to ovine embryogenesis in an in vitro embryo production system

The differences in the embryo production potential of four rams used in a commercial embryo transfer program were examined in both in vivo and in vitro embryo production systems. Processing frozen-thawed spermatozoa through Percoll density gradients prior to in vitro insemination eliminated differences in the estimates of sperm viability between the four rams, and yet, differences in embryo production persisted throughout the in vitro culture period. However, there was no effect of ejaculate within ram on embryo production rates. In addition, the timing of the onset of the differences between the rams at each stage of in vitro embryo development were revealed. Ram 2 differed from ram 4 in the proportion of fertilized oocytes at 17 h post-insemination (pi) and by 52 h, ram 3 differed from ram 4 in the proportion of cleaved embryos, and the observed differences between ram 1 and ram 2 in their blastocyst production were initiated prior to activation of the embryonic genome. Once differences in embryo development rates were detected among the four rams, they persisted throughout the in vitro culture period. The reduced in vitro fertilization (IVF) rates from ram 2 compared with the other rams was paralleled in vivo by the significantly lower proportion of embryos recovered from ewes mated to ram 2, and this was further exacerbated by a significantly lower embryo survival rate after transfer. However, the subtle differences observed in the timing of the contribution of each sire to embryo development during in vitro culture were not able to be detected in vivo. However, the higher proportions of transferable quality blastocysts obtained from ewes mated to ram 4 did not result in increased embryo survival throughout the remainder of gestation. Therefore, in this study, the blastocyst production potential for a particular sire, either in vitro or in vivo, does not necessarily reflect the potential for the production of live offspring.     

Enzymatic production of linalool esters in organic and solvent-free system

This work investigated the influence of temperature, enzyme concentration, substrates molar ratio, in the absence and presence of organic solvent, at two molar ratios of the substrates on the enzymatic production of linalil esters using the immobilized lipase Novozym 435 as catalyst, different acids and linalool and Ho-Sho essential oil as substrates. The best reaction conversion was obtained at the highest temperature (70 °C), for both solvent free (3.81%) and with solvent addition (2.25%), for a solvent to substrates molar ratio of 2:1, enzyme concentration of 5 wt% and acid to alcohol molar ratio of 1:1. The reaction kinetics revealed that Ho-Sho essential oil afforded the greatest conversions when compared with pure linalool. Higher linalil esters production were achieved after 10 h reaction (5.58%) in 2:1 solvent to substrates molar ratio, with enzyme concentration of 5 wt%, at 70 °C and anhydride to alcohol molar ratio of 1:1 using Ho-Sho essential oil as substrate.     

Cycling of organic and inorganic sulphur in a chestnut oak forest

Summary Sulfur (S) cycling in a chestnut oak forest on Walker Branch Watershed, Tennessee, was dominated by geochemical processes involving sulfate. Even though available SO ₄ ^2- was present far in excess of forest nutritional requirements, the ecosystem as a whole accumulated 60% of incoming SO₄–S. Most (90%) of this accumulation occurred by SO ₄ ^2- adsorption in sesquioxide-rich subsurface soils, with a relatively minor amount accumulating and cycling as SO ₄ ^2- within vegetative components. Organic sulfates are thought to constitute a large proportion of total S in surface soils, also, and to provide a pool of readily mineralized available S within the ecosystem.Research sponsored by Division of Biomedical and Environmental Research, U.S. Department of Energy, under contract W-7405-eng-26 with Union Carbide Corporation. Soil ester sulfate work sponsored by contract RP-1813-1 with the Electric Power Research Institute. Publication No. 1990, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830     

Conversion of oxyhemoglobin to methemoglobin by organic and inorganic reductants

Human oxyhemoglobin is converted to methemoglobin by a wide array of organic and inorganic reductants. Depending upon the concentration and nature of the reductant, varying amounts of deoxyhemoglobin are produced. The general overall sequence is: FeO2 leads to (1) FeIII leads to (2) FeII. The intermediacy of methemoglobin can be demonstrated by direct spectral observation and by cyanide trapping. For organic reductants, the second-order rate constants for (1) vary from greater than 300 (phenylhydroxylamine) to 1.4 X 10(-4) M-1 s-1 (malononitrile). Generally the rates parallel the ease of hydrogen abstraction by iron-bound oxygen from the substrate, and simply hydrocarbons are reactive. Rates for these processes have been ascertained with recrystallized protein, lysed cells, and intact human erythrocytes. At room temperature oxyhemoglobin quantitatively converts benzaldehyde to benzoic acid and hydroquinone to benzoquinone. Rates for inorganic species (process 1) range from greater than 7 X 10(3) (chromous ion) to 0.015 M-1 s-1 (ferrocyanide). Ferrous ion rapidly deoxygenates oxyhemoglobin by direct attack on the oxy complex but methemoglobin is not an intermediate with this reagent. Taken together the results support the theoretical prediction that reductants should oxidize oxyhemoglobin, and they demonstrate at least some degree of radical character to the oxy complex.     

Coral reef encruster communities and carbonate production in cryptic and exposed coral reef habitats along a gradient of terrestrial disturbance

Encrusting calcareous organisms such as bryozoans, crustose coralline algae (CCA), foraminiferans, and serpulid worms are integral components of tropical framework-building reefs. They can contribute calcium carbonate to the reef framework, stabilise the substrate, and promote larval recruitment of other framework-building species (e.g. coral recruits). The percentage cover of encrusting organisms and their rates of carbonate production (g m⁻² year⁻¹) were assessed at four sites within a coastal embayment, along a gradient of riverine influence (high-low). As the orientation and type of substrate is thought to influence recruitment of encrusting organisms, organisms recruiting to both natural (the underside of platy corals) and experimental substrates were assessed. The effect of substrate exposure under different levels of riverine influence was assessed by orientating experimental substrates to mimic cryptic and exposed reef habitats (downwards-facing vs upwards-facing tiles) at each site. Cryptic experimental tiles supported similar encruster assemblages to those recruiting to the underneath (cryptic side) of platy corals, suggesting that tiles can be used as an experimental substrate to assess encruster recruitment in reef systems. Encruster cover, in particular CCA, and carbonate production was significantly higher at low-impact (clear water), high wave energy sites when compared to highly riverine impacted (turbid water), low wave energy sites. Cryptically orientated substrates supported a greater diversity of encrusting organisms, in particular serpulid worms and bryozoans. The inverse relationships observed between riverine inputs and encrusters (total encruster cover and carbonate production) have implications for both the current and future rates and styles of reefal framework production.     

Effects of sunlight on the production of dissolved organic and inorganic nutrients from resuspended sediments

A series of laboratory-based and field experiments was conducted to address the effects of sunlight-exposed resuspended sediments on dissolved nutrient fluxes in two different water bodies. In suspensions of tidal creek sediments in 0.2 μm-filtered creek water, measurable increases in dissolved nutrients occurred after only 2 h of exposure to simulated sunlight. During a 6-h irradiation, nutrient release rates for total dissolved nitrogen (TDN) and phosphate were 2.2 ± 0.5 (standard error; S.E.) μmol g^?1 h^?1 and 0.09 ± 0.005 μmol g^?1 h^?1 (S.E.), compared to no significant changes in dark controls. The majority of nitrogen was released as dissolved organic nitrogen (87% on average) with lesser amounts of ammonium (13%). Continental shelf sediments resuspended in unfiltered seawater also released phosphate and TDN when exposed to sunlight, suggesting that this process can occur in a variety of marine and estuarine environments. The source material for inorganic nutrients appears to be associated with sediments rather than dissolved organic matter, as no significant changes in nutrient concentrations occurred in experiments with 0.2 μm-filtered creek water or seawater alone. Results suggest that photoproduction of dissolved nutrients from resuspended sediments could be an episodically significant and previously unrecognized source of dissolved organic and inorganic nutrients to coastal ecosystems. This process may be especially important for continental margins where episodic resuspension events occur, as well as in regions experiencing high riverine sediment fluxes resulting from erosion associated with deforestation and desertification.     

Growth and H2 production by Synechococcus spp. using organic/inorganic electron donors

Growth with simultaneous photoproduction of H₂ was obtained on various organic and inorganic compounds using axenic cultures of the oxygenic phototrophic bacteria Synechococcus sp. OU 103 and S. cedrorum. Highest H₂ production occurred with resting cells of S. cedrorum on malate (11.8 mmol H₂/vessel), whereas Synechococcus sp. OU 103 preferred sulphide (10.3 mmol H₂/vessel) as electron donor.The authors are with the Microbial Biotechnology Lab. Department of botany, Osmania University, Hyderabad 500 007, India.     

Hydrologic flowpaths influence inorganic and organic nutrient leaching in a forest soil

Hydrologic pathways through soil affect element leaching by determining the relative importance of biogeochemical processes such as sorption and decomposition. We used stable hydrogen isotopes of water (δD) to examine the influence of flowpaths on soil solution chemistry in a mature spruce–hemlock forest in coastal Oregon, USA. Soil solutions (50 cm depth, n = 13) were collected monthly for 1 year and analyzed for δD, major ions and dissolved organic carbon (DOC) and nitrogen (DON). We propose that the variability of δD can be used as an index of flowpath length and contact time. Throughfall variability in δD was much greater than soil solution variability, illustrating that soil solution integrates the variation in inputs. Lysimeters with greater variation in δD presumably have a greater proportion of flow through rapid flowpaths such as macropores. The variation in soil solution δD for individual lysimeters explained up to 53% of the variation in soil solution chemistry, and suggests that flowpaths influence leaching of some constituents. Soil solutions from lysimeters with greater δD variation had higher DOC and DON (r ² = 0.51 and 0.37, respectively), perhaps because transport via macropores reduces interaction of DOM with the soil matrix. In contrast, nitrate concentrations were highest in lysimeters with a small variation in δD, where long contact time and low DOC concentrations may yield higher net nitrification. Our results demonstrate the utility of stable isotopes to link flowpaths and soil solution chemistry, and illustrate how the spatial complexity of soils can influence ecosystem-level nutrient losses.