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11.
Marjolijn J. A. Christianen Fee O. H. Smulders Jan Arie Vonk Leontine E. Becking Tjeerd J. Bouma Sabine M. Engel Rebecca K. James Mabel I. Nava Jaco C. de Smit Jurjan P. van der Zee Per J. Palsbøll Elisabeth S. Bakker 《Global Change Biology》2023,29(1):215-230
Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well-recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing-induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality. 相似文献
12.
Gerald Platteau Guido Stroehlein James Van Alstine Masayoshi Nagaya 《Biotechnology and bioengineering》2023,120(10):2907-2916
Prepacked chromatography columns and cassette filtration units offer many advantages in bioprocessing. These include reduced labor costs and processing times, ease of storage, and enhanced process flexibility. Rectangular formats are particularly attractive as they can be easily stacked and multiplexed together for continuous processing. Cylindrical chromatography beds have dominated bioprocessing even though their bed support and pressure-flow performance vary with bed dimensions. This work presents the performance of novel, rhombohedral chromatography devices with internally supported beds. They are compatible with existing chromatography workstations and can be packed with any standard commercial resin. The devices offer pressure-flow characteristics independent of container-volume, simple multiplexing, and separation performance comparable to cylindrical columns. Their bi-planar, internal bed support allows mechanically less-rigid resins to be used at up to four times higher maximal linear velocities, and productivities approaching 200 g/L/h for affinity resins, compared to the 20 g/L/h typical of many column-based devices. Three 5 L devices should allow processing of up to 3 kg of monoclonal antibody per hour. 相似文献
13.
14.
Effect of Planting Unit Size and Sediment Stabilization on Seagrass Transplants in Western Australia 总被引:2,自引:0,他引:2
Abstract The effect of increasing planting unit size and stabilizing sediment was examined for two seagrass planting methods at Carnac Island, Western Australia in 1993. The staple method (sprigs) was used to transplant Amphibolis griffithii (J. M. Black) den Hartog and the plug method was used to transplant A. griffithii and Posidonia sinuosa Cambridge and Kuo. Transplant size was varied by increasing the number of rhizomes incorporated into a staple and increasing the diameter of plugs. Planting units were transplanted into bare sand, back into the original donor seagrass bed, or into a meadow of Heterozostera tasmanica, which is an important colonizing species. Sprigs of A. griffithii were extracted from a monospecific meadow; tied into bundles of 1, 2, 5, and 10 rhizomes; and planted into unvegetated areas. Half the units were surrounded by plastic mesh and the remainder were unmeshed. All treatments were lost within 99 days after transplanting, and although larger bundles survived better than smaller ones, no significant differences could be attributed to the effects of mesh or sprig size. Plugs of P. sinuosa and A. griffithii were extracted from monospecific meadows using polyvinyl chloride pipe of three diameters, 5, 10, and 15 cm, and planted into unvegetated areas nearby. Half the units were surrounded by plastic mesh and the remainder were unmeshed. Posidonia sinuosa plugs were also placed within a meadow of H. tasmanica (Martens ex Aschers.) den Hartog. Only 60% of A. griffithii plug sizes survived 350 days after transplanting back into the donor bed; however, survival of transplants at unvegetated areas varied considerably, and analysis of variance indicated a significant two‐way interaction between treatment and plug size. Transplants survived better when meshed (90% survived) and survival improved with increasing plug size. Posidonia sinuosa transplants survived poorly (no plugs survived beyond 220 days in bare or meshed treatments) regardless of size. Survival of 10‐ and 15‐cm plugs was markedly better than the 5‐cm plugs in vegetated areas, including the H. tasmanica meadow. The use of large seagrass plugs may be appropriate for transplantation in high‐energy wave environments. 相似文献
15.
16.
Purification of monoclonal antibodies from whole hybridoma fermentation broth by fluidized bed adsorption 总被引:6,自引:0,他引:6
To achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose-based matrix (Stream-line-SP), and a self-derivatized material based on controlled-pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose-based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. (c) 1995 John Wiley & Sons, Inc. 相似文献
17.
The impact of air perfusion on the endothelial function of the rat mesenteric arterial bed (MAB; perfused with Krebs' bicarbonate plus indomethacin) was compared to that of the NO synthase inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME). Air shifted the dose-response curve for the alpha-adrenoceptor agonist, norepinephrine (NE) to the left (ED50%: 2.9 ± 0.7 to 0.9 ± 0.7 μg, P < 0.05); maximal vasoconstriction did not change. L-NAME produced a similar increase in midrange sensitivity (ED50% 1.4 ± 0.7 μg, P < 0.05) and a 20% increase in maximum (152 ± 6 to 183 ± 7 mmHg, P < 0.05). Electromechanical stimulation with potassium chloride (KCL) was not modified by reserpine. Neither air nor L-NAME modified midrange sensitivity to KCL. L-NAME produced a 17% increase in maximum (91 ± 4 to 107 ± 5 mmHg, P < 0.05); reserpine abolished the latter effect. Air and L-NAME diminished endothelium-dependent vasodilation elicited by carbachol. Air did not modify endothelium-dependent vasodilation elicited by sodium nitroprusside; this response was potentiated by L-NAME. In summary, air and L-NAME produced similar effects on receptor-dependent activation of the endothelial L-arginine nitric oxide (NO) pathway. Potentiation by L-NAME of the maximal electromechanical response suggests the existence of a tone-dependent NO system. Abolition of the latter response by reserpine suggests that this system is of sympathetic origin. 相似文献
18.
In this paper we describe a fast and mild method based on the use of a unique cation exchanger and buffers containing ethylene glycol and salt for the purification of the myelin basic protein (MBP; MW 18.5 kDa). MBP thus purified hydrolyses catalytically p-nitrophenyl acetate. This esterase activity facilitates not only the purification of MBP but also indicates that probably it is in its native state, i.e. there is a good chance that the purified molecules are structurally and chemically identical. This is a prerequisite to obtain crystals appropriate for x-ray diffraction and other studies.Abbreviations used MBP
myelin basic protein
- MW
molecular weight
- kDa
kilo Dalton
- octyl-POE
n-octylpolydisperse oligooxyethylene
- CHAPS
3-3-cholamidopropyl dimethylammonio-1-propane-sulfonate
- CTAB
cetyltrimethylammonium bromide
- SDS
sodium dodecyl sulfate
- SDS-PAGE
polyacrylamide gel electrophoresis in the presence of SDS
- G 3707
heptaoxyethylene lauryl ether
- TWEEN-20
polyoxyethylenesorbitan-monolaurat
- EDTA
ethylenediaminetetraacetic acid
- HEPES
N-(2-hydroxyethyl)-piperazine-N-(2-ethanesulfonic acid) 相似文献
19.
M. T. O. Barreto E. P. Melo J. L. Moreira M. J. T. Carrondo 《Journal of industrial microbiology & biotechnology》1991,7(1):63-69
Summary The production of a flocculent strain ofLactobacillus plantarum was performed in a high cell density reactor: a fluidized bed reactor (FBR) with a settler and an external cell recirculation. Two variables were assessed, the recirculation rate (R) and the dilution rate (D). The effect of the latter is much more important than the effect of the former in ensuring a quick start up in the flocculation process. The cell volumetric productivities obtained with this system increase directly with dilution rate and recirculation rate. The values of cell volumetric productivities obtained are considerably higher than those obtained in continuous stirred tank reactors (CSTR) and much higher than in batch reactors. 相似文献
20.
Results of semi-quantitative observations and quantitative sampling of seagrasses at coastal and offshore sites along the
western Arabian Gulf are presented. Overall seagrass cover (all species together) shows significant positive correlation with
latitude, but not with salinity, temperature or depth. The same pattern is shown by Halodule uninervis (Forsk.) Aschers., the dominant species. Mean seagrass biomass ranged from 53–235 g m-2 (dry weight). These values are comparable with biomass estimates from regions in which environmental conditions are generally
less extreme than in the Gulf. Seagrass biomass is significantly negatively correlated with depth and sediment grain size.
No significant correlation is apparent between seagrass biomass and factors such as season, salinity, or concentrations of
nutrients and heavy metals measured. It is pointed out that any correlations observed are not necessarily taken to imply causality. 相似文献