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1.
《Biomass》1988,15(4):249-257
An experiment was conducted in the growth chamber to quantify the biomass production, N removal and N2 fixation from a synthetic medium by Chlamydomonas reinhardtii and Anabaena flos-aquae. Nitrogen was supplied at a concentration of 100 mg liter−1 of NO3−−15N and NH4+−15 (3·5 atom %), respectively. After 21 days Chlamydomonas reinhardtii removed an average of 83·8 and 78·7 mg N liter−1 as NO3− and NH4+, respectively. Averages of 0·89 and 0·71 g liter−1 (first batch), 1·63 and 0·95 g liter− (second batch) algal biomass were collected from NO3− and NH4+ media, respectively. Uptake rates of 0·11 mg 15N g−1 algae day−1 from NO3− medium and 0·10 mg 15N g−1 algae day−1 from NH4+ medium were calculated. Algal cells grown in NO3− and NH4+ medium contained 71 and 65 g N kg−1 (first batch), 39 and 58 g N kg−1 (second batch), respectively. Anabaena flos-aquae produced averages of 0·58 and 0·46 g liter−1 (first batch), 0·55 and 0·48 g liter−1 (second batch) after 14 days of growth from NO3− and NH4+ media, respectively. Blue-green algal biomass contained higher N (81–98 g kg−1) than green algae. Isotope dilution method for determining N2 fixation indicated that 55% and 77% of total N of blue-green algae grown in NO3− and NH4+ media, respectively, was derived from the atmosphere. 相似文献
2.
《Harmful algae》2011
The uptake rates of different nitrogen (N) forms (NO3−, urea, and the amino acids glycine and glutamic acid) by N-deficient, laboratory-grown cells of the mixotrophic haptophyte, Prymnesium parvum, were measured and the preference by the cells for the different forms determined. Cellular N uptake rates (ρcell, fmol N cell−1 h−1) were measured using 15N-labeled N substrates. P. parvum showed high preference for the tested amino acids, in particular glutamic acid, over urea and NO3− under the culture nutrient conditions. However, extrapolating these rates to Baltic Seawater summer conditions, P. parvum would be expected to show higher uptake rates of NO3− and the amino acids relative to urea because of the difference in average concentrations of these substrates. A high uptake rate of glutamic acid at low substrate concentrations suggests that this substrate is likely used through extracellular enzymes. Nitrate, urea and glycine, on the other hand, showed a non-saturating uptake over the tested substrate concentration (1–40 μM-N for NO3− and urea, 0.5–10 μM-N for glycine), indicating slower membrane-transport rates for these substrates. 相似文献
3.
《Harmful algae》2014
The West Florida Shelf (WFS) encompasses a range of environments from inshore estuarine to offshore oligotrophic waters, which are frequently the site of large and persistent blooms of the toxic dinoflagellate, Karenia brevis. The goals of this study were to characterize the nitrogen (N) nutrition of plankton across the range of environmental conditions on the WFS, to quantify the percentage of the plankton N demand met through in situ N regeneration, and to determine whether planktonic N nutrition changes when high concentrations of Karenia are present. In the fall of 2007, 2008, and 2009 we measured ambient nutrient concentrations and used stable isotope techniques to measure rates of primary production and uptake rates of inorganic N (ammonium, NH4+, and nitrate, NO3−), and organic N and carbon (C; urea and amino acids, AA) in estuarine, coastal, and offshore waters, as well as coastal sites with Karenia blooms present. In parallel, we also measured rates of in situ N regeneration – NH4+ regeneration, nitrification, and photoproduction of NH4+, nitrite and AA. Based on microscope observations, ancillary measurements, and previous monitoring history, Karenia blooms sampled represented three bloom stages – initiation in 2008, maintenance in 2007, and late maintenance/stationary phase in 2009. Nutrient concentrations were highest at estuarine sampling sites and lowest at offshore sites. Uptake of NH4+ and NO3− provided the largest contribution to N nutrition at all sites. At the non-Karenia sites, in situ rates of NH4+ regeneration and nitrification were generally sufficient to supply these substrates equal to the rates at which they were taken up. At Karenia sites, NO3− was the most important N substrate during the initiation phase, while NH4+ was the most important N form used during bloom maintenance and stationary phases. Rates of NH4+ regeneration were high but insufficient (85 ± 36% of uptake) to support the measured NH4+ uptake at all the Karenia sites although nitrification rates far exceeded uptake rates of NO3−. Taken together our results support the “no smoking gun” nutrient hypothesis that there is no single nutrient source or strategy that can explain Karenia's frequent dominance in the waters where it occurs. Consistent with other papers in this volume, our results indicate that Karenia can utilize an array of inorganic and organic N forms from a number of N sources. 相似文献
4.
《Biomass》1987,12(1):17-26
In 1983, a study was conducted to evaluate three weed species for their biomass yield potential on a fallowed tomato land with various nitrogen (N) rates and sources. Dogfennel (Eupatorium capillifolium (Lam.)Small), sida (Sida rhombifolia L.), and pigweed (Amaranthus hybridus L.), were grown with three N rates: residual, 1x and 2x (1x = 56 kg ha−1 N) and with two N sources: NH4NO3 and isobutylidene diurea (IBDU). Sida produced the greatest fresh and dry biomass yields and percentage dry matter, 43·3, 23·3 Mg ha−1 and 54·1%, respectively. Yields of the three crops increased with increasing N rates and were higher with NH4NO3 than with IBDU. Overall, sida at the 2x N rate with NH4NO3 had the highest fresh, 73·8 Mg ha−1, and dry biomass, 37·9 Mg ha−1, yield. Lowest residual soil total soluble salt concentration, 170 ppm, was found after pigweed, in plots which did not receive additional N. Additional N application increased residual soil total soluble salts after each of the three weeds. Thus, additional N, in NH4NO3 form, was necessary for high yields in a fallowed vegetable land, but the additional fertilizer also increased soil total soluble salts, regardless of the plant species. 相似文献
5.
Uptake of NO3− by nonnodulated soybean plants (Glycine max L. Merr. cv Ransom) growing in flowing hydroponic culture at 22 and 14°C root temperatures was measured daily during a 31-day growth period. Ion chromatography was used to determine removal of NO3− from solution during each 24-hour period. At both root-zone temperatures, rate of NO3− uptake per plant oscillated with a periodicity of 3 to 5 days. The rate of NO3− uptake per plant was consistently lower at 14°C than 22°C. The lower rate of NO3− uptake at 14°C during the initial 5 to 10 days was caused by reduced uptake rates per gram root dry weight, but with time uptake rates per gram root became equal at 14 and 22°C. Thereafter, the continued reduction in rate of NO3− uptake per plant at 14°C was attributable to slower root growth. 相似文献
6.
Measurements of net photosynthesis (PS, O2 evolution), dark respiration (R, O2 consumption), and light and dark carbon fixation (14C) were conducted on whole blades, isolated blade discs, sporophylls, apical scimitars and representative portions of stipe and holdfast of the giant kelp Macrocystis pyrifera L.C. Ag. On a dry weight basis, highest net PS rates were observed in apical scimitar segments and whole blades (3.81 and 3.07 mgC · g dry wt?1· h?1, respectively), followed by sporophylls (1.42 mgC·g dry wt?1· h?1) and stipe segments (0.15 mgC·g dry wt?1· h?1). No PS capacity was observed in holdfast material. Respiration rates showed similar ranking ranging from 1.22 mgC·g dry wt?1·h?1 for apical scimitar to 0.18–0.22 mgC·g dry wt?1· h?1 for holdfast material. Considerable within blade variability in both PS and R was also found. Steepest PS and R gradients on both an areal and weight basis were found within immature blades followed by senescent and mature blade material. Highest net PS rates were associated with the blade tips ranging from 3.08 (mature blades) to 10.3 mgC·dry wt?1·h?1 (immature blades). Highest rates of R generally occurred towards the basal portions of blades and ranged from 1.03–1.80 mgC·g dry wt?1·h?1 for immature blades. The variability within and between blades was high, with coefficients of variation approaching 50%. The observed patterns can be related to the decreasing proportionment of photosynthetic tissue and increasing proportionment of structural tissue as occurs from the blade tip to the blade base. Rates of light carbon fixation (LCF) revealed longitudinal profiles similar to oxygen measurements for the different blade types, with the absolute rates being slightly lower. Patterns of dark carbon fixation (DCF) were less easily interpreted. Highest rates of DCF (0.04–0.06 mgC·g dry wt?1·h?1) occurred at the basal portions of immature and senescent blades. Longitudinal profiles of total chlorophyll (a + c) on both an areal and weight basis were very similar to the profiles of PS. Normalized to chlorophyll a, PS displayed an unusual longitudinal profile in immature tissue; however, such profiles for mature and senescent tissues were similar to those for PS on an areal basis. It was demonstrated that it is difficult, if not impossible, to select single tissue discs that are representative of whole blades. The metabolic longitudinal profiles reveal a characteristic developmental pattern; the previous working definitions of immature, mature, and senescent blades, based on morphology and frond position thus have a physiological basis. 相似文献
7.
Yukio Agatsuma Hikaru Endo Shigeki Yoshida Chikara Ikemori Yoshio Takeuchi Hiroaki Fujishima Kazuhiko Nakajima Mitsuhiro Sano Nobuyuki Kanezaki Hisaeki Imai Naoki Yamamoto Hiroki Kanahama Takashi Matsubara Satoshi Takahashi Tatsuhiko Isogai Kazuya Taniguchi 《Journal of applied phycology》2014,26(4):1845-1852
Apart from certain studies on Macrocystis pyrifera (Linnaeus) C. Agardh, very few in situ experimental studies on production have been carried out to verify that “bottom–up effects” (relating to nutrient supply) are more important than “top–down” effects (relating to herbivory) in temperate kelp forests. The effects of nutrient supply on recruitment and production of hatchery-raised gametophytes of Saccharina japonica, cultivated on a rope, and wild Saccharina religiosa, cultivated on a rope and on new concrete reefs placed at the sea bottom, were examined at an experimental site with artificial nutrient addition continuously from October 2008 to May 2009 and compared to kelp that was cultivated from October 2008 to May 2009 without nutrient supply, at a natural site in Tomari (Sea of Japan, southwestern Hokkaido, Japan). At both sites, sea urchins were removed for exclusion of top–down effect. At the natural site, no hatchery-raised S. japonica and wild S. religiosa grew on the rope. No wild S. religiosa grew on the porous-concrete reefs and rocks. At the nutrient-enhanced site, S. japonica and S. religiosa grew rapidly on the rope, at rates of 47.7 and 33.3 plants/10 cm length rope, respectively. S. religiosa grew on the concrete reefs at a concentration of 9.7 plants/0.3 m2. At the nutrient-enhanced site, the concentrations of NH4-N, NO3-N, NO2-N, and PO4-P ranged from 35.2–173.2, 2.1–10.9, 0.3–1.5, and 0.8–2.6 μmol L?1, respectively, being markedly higher than those at the natural site, where these nutrient concentrations were almost equal to the averages off Tomari. These results indicate that the production of Saccharina kelp is restricted by bottom–up effects (at a low nutrient concentration) in the Sea of Japan, southwestern Hokkaido. Nutrient supply would be essential for growth enhancement of Saccharina kelp production in a marine environment around Japan where, in recent times, water temperatures have increased by ca. 0.5 °C and nutrient concentrations have decreased. 相似文献
8.
Laminaria longicrucis De la Pylaie took up exogenous nitrate under both summer and winter conditions. During July and August no NO3- was detected in the ambient water or in algal tissues although it was present in both in February. Discs (2.3 cm diam.) of thin blade tissue were incubated with NO3- at four temperatures, with and without illumination. Similar values Jor NO3- uptake were found for both summer and winter collected plants when measured in light at 0 C. An apparent K of 4–6 μM was recorded for both types of plants; the Vmax ranged from 7 to 10 μmol h-1 g-1 dry wt measured in ca. 1800 μW cm-2 of cool-white fluorescent light. Uptake rates at 5 C were 66%, and at 0 C 30% of those for controls run at 15 C. The alga scavenged NO3- from solutions <0.5 μM. Ammonia did not inhibit NO3- uptake. Antibiotic pretreatment reduced NO3- uptake by a maximum of 12%. Nitrite uptake was inhibited in proportion to the concentration of NO3- in the medium. 相似文献
9.
《Harmful algae》2015
The nitrogen (N) uptake kinetic parameters for Microcystis field assemblages collected from the San Francisco Bay Delta (Delta) in 2012 and non-toxic and toxic laboratory culture strains of M. aeruginosa were assessed. The 15N tracer technique was used to investigate uptake of ammonium (NH4+), nitrate (NO3−), urea and glutamic acid over short-term incubations (0.5–1 h), and to study inhibition of NO3−, NH4+ and urea uptake by NH4+, NO3− and NH4+, respectively. This study demonstrates that Delta Microcystis can utilize different forms of inorganic and organic N, with the greatest capacity for NH4+ uptake and the least for glutamic acid uptake, although N uptake did not always follow the classic Michaelis–Menten hyperbolic relationship at substrate concentrations up to 67 μmol N L−1. Current ambient N concentrations in the Delta may be at sub-saturating levels for N uptake, indicating that if N loading (especially NH4+) were to increase, Delta Microcystis assemblages have the potential for increased N uptake rates. Delta Microcystis had the highest specific affinity, α, for NH4+ and the lowest for NO3−. In culture, N uptake by non-toxic and toxic M. aeruginosa strains was much higher than from the field, but followed similar N utilization trends to those in the field. Neither strain showed severe inhibition of NO3− uptake by NH4+ or inhibition of NH4+ uptake on NO3−, but both strains showed some inhibition of urea uptake by NH4+. 相似文献
10.
CO2 flux in alpine wetland ecosystem on the Qinghai-Tibetan Plateau, China 总被引:3,自引:0,他引:3
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Using the CO2 flux data measured by the eddy covariance method in the northeast of Qinghai-Tibetan Plateau in 2005, we analyzed the carbon flux dynamics in relation to meteorological and biotic factors. The results showed that the alpine wetland ecosystem was the carbon source, and it emitted 316.02 gCO2 · m−2 to atmosphere in 2005 with 230.16 gCO2 · m−2 absorbed in the growing season from May to September and 546.18 gCO2 · m−2 released in the non-growing season from January to April and from October to December. The maximum of the averaged daily CO2 uptake rates and release rates was (0.45 ± 0.0012) mgCO2 · m−2 · s−1 (Mean ± SE) in July and (0.22 ± 0.0090) mgCO2 · m−2 · s−1 in August, respectively. The averaged diurnal variation showed a single-peaked pattern in the growing season, but exhibited very small fluctuation in the non-growing season. Net ecosystem exchange (NEE) and gross primary production (GPP) were all correlated with some meteorological factors, and they showed a negatively linear correlation with aboveground biomass, while a positive correlation existed between the ecosystem respiration (Res) and those factors. 相似文献
11.
《Harmful algae》2017
Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the 15N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH4+), nitrate (NO3−) and N-urea, from the estimation of kinetic and inhibition parameters. In the range of 0 to 10 μmol N L−1, kinetic curves showed a clear preference pattern following the ranking NH4+ > NO3− > N-urea, where the preferential uptake of NH4+ relative to NO3− was accentuated by an inhibitory effect of NH4+ concentration on NO3− uptake capabilities. Conversely, under high nutrient concentrations, the preference for NH4+ relative to NO3− was largely reduced, probably because of the existence of a low-affinity high capacity inducible NO3− uptake system. Ability to take up nutrients in darkness could not be defined as a competitive advantage for O. cf. ovata. Species competitiveness can also be defined from nutrient uptake kinetic parameters. A strong affinity for NH4+ was observed for O. cf. ovata cells that may partly explain the success of this toxic species during the summer season in the Bay of Villefranche-sur-mer (France). 相似文献
12.
Factors correlating with deterioration of giant kelp Macrocystis pyrifera (Laminariales, Heterokontophyta) in an aquarium setting 总被引:1,自引:0,他引:1
Survival of the giant kelp, Macrocystis pyrifera (Linnaeus) C. Agardh, in its natural habitat is governed by abiotic and biotic factors such as temperature, light, nutrients, current velocity, and predators. Factors affecting the survival of the alga in an aquarium setting, however, have not been investigated. The National Museum of Marine Biology and Aquarium (NMMBA), in subtropical Taiwan, is the only aquarium in the world that displays giant kelp that does not have naturally occurring specimens in nearby waters. Giant kelp displayed in aquaria often deteriorates within a 3-month period, yet the cause of this mortality is unknown. We investigated abiotic and biotic parameters affecting survival of giant kelp in aquaria over a 3-month period. The results indicated that temperature, salinity, pH, light, and nutrient concentrations did not affect giant kelp survival. However, the massive proliferation of epiphytic diatoms on kelp blades (from 7?×?102 cells cm?2 initially to 3?×?104 cells cm?2 after 1 month) was identified as being the most likely candidate affecting survival of giant kelp in an aquarium setting. Potential factors that may stimulate epiphyte proliferation include lack of epiphytic algae control via predation, high nutrient concentrations, a weak current, and a generally stable environment. 相似文献
13.
Abiotic influences on bicarbonate use in the giant kelp,Macrocystis pyrifera,in the Monterey Bay
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In the Monterey Bay region of central California, the giant kelp Macrocystis pyrifera experiences broad fluctuations in wave forces, temperature, light availability, nutrient availability, and seawater carbonate chemistry, all of which may impact their productivity. In particular, current velocities and light intensity may strongly regulate the supply and demand of inorganic carbon (Ci) as substrates for photosynthesis. Macrocystis pyrifera can acquire and utilize both CO2 and bicarbonate (HCO3?) as Ci substrates for photosynthesis and growth. Given the variability in carbon delivery (due to current velocities and varying [DIC]) and demand (in the form of saturating irradiance), we hypothesized that the proportion of CO2 and bicarbonate utilized is not constant for M. pyrifera, but a variable function of their fluctuating environment. We further hypothesized that populations acclimated to different wave exposure and irradiance habitats would display different patterns of bicarbonate uptake. To test these hypotheses, we carried out oxygen evolution trials in the laboratory to measure the proportion of bicarbonate utilized by M. pyrifera via external CA under an orthogonal cross of velocity, irradiance, and acclimation treatments. Our Monterey Bay populations of M. pyrifera exhibited proportionally higher external bicarbonate utilization in high irradiance and high flow velocity conditions than in sub‐saturating irradiance or low flow velocity conditions. However, there was no significant difference in proportional bicarbonate use between deep blades and canopy blades, nor between individuals from wave‐exposed versus wave‐protected sites. This study contributes a new field‐oriented perspective on the abiotic controls of carbon utilization physiology in macroalgae. 相似文献
14.
We quantified the effects of initial macroalgal tissue nitrogen (N) status (depleted and enriched) and varying pulses of nitrate (NO3?) concentration on uptake and storage of nitrogen in Ulva intestinalis L. and Ulva expansa (Setch.) Setch. et N. L. Gardner using mesocosms modeling shallow coastal estuaries in Mediterranean climates. Uptake of NO3? (μmol · g dry weight [dwt]?1 · h?1) was measured as loss from the water after 1, 2, 4, 8, 12, and 24 h and storage as total tissue nitrogen (% dwt) and nitrate (ppm). Both species of algae exhibited a high affinity for NO3? across all N pulses and initial tissue contents. There was greater NO3? removal from the water for depleted than enriched algae across all time intervals. In the low‐N‐pulse treatment, U. intestinalis and U. expansa removed all measurable NO3? within 8 and 12 h, respectively, and in the medium and high treatments, removal was high and then decreased over time. Maximum mean uptake rates of nitrate were greater for U. expansa (~300 μmol · g dwt?1 · h?1) than U. intestinalis (~100 μmol · g dwt?1 · h?1); however, uptake rates were highly variable over time. Overall, U. expansa uptake rates were double those of U. intestinalis. Maximum tissue NO3? for U. expansa was >1,000 ppm, five times that of U. intestinalis, suggesting that U. expansa has a greater storage capacity in this cellular pool. These results showed that opportunistic green algae with differing tissue nutrient histories were able to efficiently remove nitrate from the water across a wide range of N pulses; thus, both are highly adapted to proliferate in estuarine environments with pulsed nutrient supplies. 相似文献
15.
Ammonium and nitrate uptake rates in the macroalgae Ulva fenestrata (Postels and Ruprecht) (Chlorophyta) and Gracilaria pacifica (Abbott) (Rhodophyta) were determined by 15N accumulation in algal tissue and by disappearance of nutrient from the medium in long‐term (4–13 days) incubations. Nitrogen‐rich algae (total nitrogen> 4% dry weight [dw]) were used to detect isotope dilution by release of inorganic unlabeled N from algal thalli. Uptake of NH4 + was similar for the two macroalgae, and the highest rates were observed on the first day of incubation (45 μmol N·g dw ? 1·h ? 1 in U. fenestrata and 32 μmol N·g dw ? 1·h ? 1 in G. pacifica). A significant isotope dilution (from 10 to 7.9 atom % enrichment) occurred in U. fenestrata cultures during the first day, corresponding to a NH4 + release rate of 11 μmol N·g dw ? 1·h ? 1. Little isotope dilution occurred in the other algal cultures. Concurrently to net NH4 + uptake, we observed a transient free amino acid (FAA) release on the first day in both macroalgal cultures. The uptake rates estimated by NH4 + disappearance and 15N incorporation in algal tissue compare well (82% agreement, defined as the percentage ratio of the lower to the higher rate) at high NH4 + concentrations, provided that isotope dilution is taken into account. On average, 96% of added 15NH4 + was recovered from the medium and algal tissue at the end of the incubation. Negligible uptake of NO3 ? was observed during the first 2–3 days in both macroalgae. The lag of uptake may have resulted from the need for either some N deprivation (use of NO3 ? pools) or physiological/metabolic changes required before the uptake of NO3 ? . During the subsequent days, NO3 ? uptake rates were similar for the two macroalgae but much lower than NH4 + uptake rates (1.97–3.19 μmol N·g dw ? 1·h ? 1). Very little isotope dilution and FAA release were observed. The agreement between rates calculated with the two different methods averaged 91% in U. fenestrata and 95% in G. pacifica. Recovery of added 15NO3 ? was virtually complete (99%). These tracer incubations show that isotope dilution can be significant in NH4 + uptake experiments conducted with N‐rich macroalgae and that determination of 15N atom % enrichment of the dissolved NH4 + is recommended to avoid poor isotope recovery and underestimation of uptake rates. 相似文献
16.
Xiao Fan Dong Xu Yitao Wang Xiaowen Zhang Shaona Cao Shanli Mou Naihao Ye 《Journal of applied phycology》2014,26(1):537-544
The green-tide macroalga, Ulva prolifera, was tested in the laboratory to determine its nutrient uptake and photosynthesis under different conditions. In the nutrient concentration experiments U. prolifera showed a saturated uptake for nitrate but an escalating uptake in the tested range for phosphorus. Both N/P and NO3 ?/NH4 + ratios influenced nutrient uptake significantly (p?<?0.05) while the PSII quantum yield [Y(II)] (p?>?0.05) remained unaffected. The maximum N uptake rate (33.9?±?0.8 μmol g?1 DW h?1) and P uptake rate (11.1?±?4.7) was detected at N/P ratios of 7.5 and 2.2, respectively. U. prolifera preferred NH4 +-N to NO3 ?-N when the NO3 ?-N/NH4 +-N ratio was less than 2.2 (p?<?0.05). But between ratios of 2.2 and 12.9, the uptake of NO3 ?-N surpassed that of NH4 +-N. In the temperature experiments, the highest N uptake rate and [Y(II)] were observed at 20 °C, while the lowest rates were detected at 5 °C. P uptake rates were correlated with increasing temperature. 相似文献
17.
Uptake rates of nitrate and phosphate were measured for four species and one variety of Porphyra from Long Island Sound (USA) at two temperatures and two nutrient medium concentrations at increasing intervals over a 24- or 48-h period. Maximum uptake rates found were: V30 μM0-1 h=73.8 μmol NO3 g−1 DW h−1 and V3 μM0-1 h=16.7 μmol PO4 g−1 DW h−1, in the two thinnest Porphyra. We found that the nitrate uptake rates were significantly greater at 30 μM than 3 μM NO3 concentration, and that the uptake rates decreased with time of exposure. Temperature (5, 15, and 25 °C) did not have as strong an effect on nitrate uptake rates as did nutrient concentration. Q10 values and uptake rates at four different nitrate concentrations indicated that nutrient uptake at 5 °C was initially an active process. After 24 h, the processes involved appeared passive as Q10 values were between 1.0 and 1.3 and nitrate uptake curves were linear. Nitrate uptake rates correlated positively with the surface area/volume (SA/V) ratio. No coherent trends were found for uptake of phosphate, except that the uptake rates were significantly higher in 30 μM NO3 medium as opposed to 3 μM NO3. We did not find any significant difference in uptake rate and pattern between the summer species Porphyra purpurea (Roth.) C. Agardh, the eurythermic Porphyra suborbiculata Kjellm., the winter species Porphyra rosengurttii J. Coll and J. Cox, and the two varieties of Porphyra leucosticta Thur. Le Jol. (both winter species). 相似文献
18.
Kiara Franke Lisa C. Matthes Angelika Graiff Ulf Karsten Inka Bartsch 《Journal of phycology》2023,59(3):518-537
Coastal kelp forests produce substantial marine carbon due to high annual net primary production (NPP) rates, but upscaling of NPP estimates over time and space remains difficult. We investigated the impact of variable underwater photosynthetically active radiation (PAR) and photosynthetic parameters on photosynthetic oxygen production of Laminaria hyperborea, the dominant NE-Atlantic kelp species, throughout summer 2014. Collection depth of kelp had no effect on chlorophyll a content, pointing to a high photoacclimation potential of L. hyperborea towards incident light. However, chlorophyll a and photosynthesis versus irradiance parameters differed significantly along the blade gradient when normalized to fresh mass, potentially introducing large uncertainties in NPP upscaling to whole thalli. Therefore, we recommend a normalization to kelp tissue area, which is stable over the blade gradient. Continuous PAR measurements revealed a highly variable underwater light climate at our study site (Helgoland, North Sea) in summer 2014, reflected by PAR attenuation coefficients (Kd) between 0.28 and 0.87 m−1. Our data highlight the importance of continuous underwater light measurements or representative average values using a weighted Kd to account for large PAR variability in NPP calculations. Strong winds in August increased turbidity, resulting in a negative carbon balance at depths >3–4 m over several weeks, considerably impacting kelp productivity. Estimated daily summer NPP over all four depths was 1.48 ± 0.97 g C · m−2 seafloor · d−1 for the Helgolandic kelp forest, which is in the range of other kelp forests along European coastlines. 相似文献
19.
Wildfire Effects on Soil Gross Nitrogen Transformation Rates in Coniferous Forests of Central Idaho, USA 总被引:2,自引:0,他引:2
Forest fires often result in a series of biogeochemical processes that increase soil nitrate (NO3 ?) concentrations for several years; however, the dynamic nature of inorganic nitrogen (N) cycling in the plant–microbe–soil complex makes it challenging to determine the direct causes of increased soil NO3 ?. We measured gross inorganic N transformation rates in mineral soils 2 years after wildfires in three central Idaho coniferous forests to determine the causes of the elevated soil NO3 ?. We also measured key factors that could affect the soil N processes, including temperature during soil incubation in situ, soil water content, pH and carbon (C) availability. We found no significant differences (P = 0.461) in gross nitrification rates between burned and control soils. However, microbial NO3 ? uptake rates were significantly lower (P = 0.078) in burned than control soils. The reduced consumption of NO3 ? caused slightly elevated NO3 ? concentrations in the burned soils. C availability was positively correlated with microbial NO3 ? uptake rates. Despite reduced microbial NO3 ? uptake capacity in the burned soils, soil microbes were a strong enough N sink to maintain low soil NO3 ? concentrations 2 years post fire. Soil NH4 + concentrations between the treatments were not significantly different (P = 0.673). However, gross NH4 + production and microbial uptake rates in burned soils were significantly lower (P = 0.028 and 0.035, respectively) than in the controls, and these rates were positively correlated with C availability. Our results imply that C availability is an important factor regulating soil N cycling of coniferous forests in the region. 相似文献
20.
B.I. Van Tussenbroek 《欧洲藻类学杂志》2013,48(3):161-165
Fluctuations in plant and frond characteristics are described for Macrocystis pyrifera (L.) C. Agardh (Laminariales, Phaeophyta) forming a fringing zone in the Falkland Islands. Giant kelp plants were sampled along a transect in the austral autumn (May 1986) and late spring (December 1986) which, according to previous frond weight analysis, were the times when extremes in population parameters were expected. Plant density and holdfast wet weights were similar for both seasons, but plants had more fronds and the fronds weighed more in spring than in autumn. Consequently, in autumn the frond biomass (1·1 wet kg m?2) and productivity (34·1 wet g m?2 d?1) were lower than in spring, when a biomass of 5·0 wet kg m?2 and a productivity of 72·4 wet g m?2 d?1 were recorded. Production of new fronds and loss of old fronds were determined at monthly intervals between April 1986 and March 1987. New frond production rates followed fluctuations in the quantity of light and varied between 0·08 and 0·48 fronds per plant per day. Frond loss rates did not show a seasonal pattern and fluctuated between 0·05 and 0·42 fronds per plant per day. It is suggested that the Falkland Islands Macrocystis population is more stable than most other giant kelp beds at high latitudes, because of the absence of winter storms. 相似文献