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HANS JORGEN HANSEN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1972,5(1):39-45
Two species of the foraminiferal genus Turrilina Andreae, 1844, occurring in the Tertiary beds of Denmark and Holland, can be distinguished by their wall structure only. In consequence it is recommended that the wall structure as a systematic character may in this and similar cases be of specific value only. 相似文献
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Bacterial production in the carbon flow of a central European stream, the Breitenbach 总被引:1,自引:0,他引:1
JÜRGEN MARXSEN 《Freshwater Biology》2006,51(10):1838-1861
1. Over the last 30 years, many investigations have been performed on the dynamics of bacteria and organic matter in the Breitenbach, a first‐order stream in central Germany. The data now available allow a synthesis of the role of bacteria in the carbon budget, as an example of the general importance of bacteria in stream ecosystems. 2. Comparing measured and estimated inputs and outputs to the ecosystem, the organic matter budget of the Breitenbach is fairly balanced: 1.84 kg C m?2 year?1 (sum of inputs) versus 1.88 kg C m?2 year?1 (sum of outputs). No major missing link remains. 3. The basis of the food web in the Breitenbach is mainly allochthonous organic matter (dissolved and particulate 1.02 and 0.42 kg C m?2 year?1, respectively). Autochthonous gross primary production is 0.4 kg C m?2 year?1. Most of the organic matter leaves the stream via transport to the River Fulda (dissolved and particulate 0.74 and 0.34 kg C m?2 year?1, respectively), the rest by respiration (0.80 kg C m?2 year?1 or 43% of total outputs). 4. Bacteria constitute an important part (36%) of heterotrophic biomass (average: 0.004 kg m?2 bacterial C of 0.011 kg m?2 total heterotrophic C). Bacteria also account for the major fraction (71%) of heterotrophic production: 0.20 of 0.28 kg C m?2 year?1 total heterotrophic production. Bacterial production in the Breitenbach is similar in magnitude to the estimate of photoautotrophic net primary production: both approximately 0.20 kg C m?2 year?1. 5. Protozoa, the main consumers of bacteria in the Breitenbach, consume approximately one‐third of bacterial production (0.07 kg C m?2 year?1). Small metazoa (meiofauna, <0.5 mm) play a lesser role in the consumption of bacteria, consuming <0.01 kg bacterial C m?2 year?1. Larger metazoa (macrofauna, >0.5 mm) consume approximately 10% of bacterial production. Although this is a considerable amount of the carbon resources needed by the macrofauna (0.02 kg C m?2 year?1 of bacterial production versus 0.06 kg C m?2 year?1 macrofauna production plus respiration), the carbon demand of the macrofaunal community is met to a larger extent by particulate organic matter than by bacteria. 6. Bacteria are the main decomposers in the Breitenbach. They account for 78% of heterotrophic respiration (0.47 of 0.60 kg C m?2 year?1) and 59% of total respiration (0.47 of 0.80 kg C m?2 year?1). 相似文献
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1. We examined selected aspects of the nutritional ecology of larval Ptychoptera paludosa and their role in nutrient cycling in the Breitenbach, a first-order stream in Hesse, Germany.
2. Food preference experiments demonstrated significant preference for sediments with a high organic matter content and live bacteria.
3. pH was circumneutral in all sections of the gut.
4. Enzymatic activity (β-glucosidase and amino-peptidase) in different parts of the gut was measured using 4-methylumbelliferyl-β- D -glucopyranoside (MUF-Glc) and leucine-4-methylcoumarinyl-7-amide (Leu-MCA). β-glucosidase activity was highest in the hindgut.
5. The mean larval gut passage time was between 7 and 8 h.
6. The egestion rate of last instar larvae was about 0.35 mg dry weight (DW) faeces per larva h–1 and about 1.25 mg ash-free dry weight (AFDW) faeces per mg larval AFDW day–1 .
7. Larval faeces contained at least 4–18 times more organic matter than the average in the sediments in which they were feeding, that is, larvae fed selectively, extracting organic matter from sediments.
8. P. paludosa larvae are important in the dynamics of detritus in slow-flowing reaches of the Breitenbach. They gather organic material from the sediment to a depth of 3 cm, and release it as faeces onto the sediment surface. A total of 770 g DW faeces m–2 yr–1 , comprising about 16% organic matter, was produced by the Ptychoptera population. 相似文献
2. Food preference experiments demonstrated significant preference for sediments with a high organic matter content and live bacteria.
3. pH was circumneutral in all sections of the gut.
4. Enzymatic activity (β-glucosidase and amino-peptidase) in different parts of the gut was measured using 4-methylumbelliferyl-β- D -glucopyranoside (MUF-Glc) and leucine-4-methylcoumarinyl-7-amide (Leu-MCA). β-glucosidase activity was highest in the hindgut.
5. The mean larval gut passage time was between 7 and 8 h.
6. The egestion rate of last instar larvae was about 0.35 mg dry weight (DW) faeces per larva h
7. Larval faeces contained at least 4–18 times more organic matter than the average in the sediments in which they were feeding, that is, larvae fed selectively, extracting organic matter from sediments.
8. P. paludosa larvae are important in the dynamics of detritus in slow-flowing reaches of the Breitenbach. They gather organic material from the sediment to a depth of 3 cm, and release it as faeces onto the sediment surface. A total of 770 g DW faeces m
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Inhibitory effects of high molecular weight dissolved organic matter upon metabolic processes in biofilms from contrasting rivers and streams 总被引:8,自引:0,他引:8
CHRISTOPHER FREEMAN MAURICE A. LOCK JÜRGEN MARXSEN SUSAN E. JONES 《Freshwater Biology》1990,24(1):159-166
SUMMARY. 1. The effect of removal of organic manor >1000 apparent molecular weight (AMW) upon biofilm processes was determined in three contrasting streams in West Germany and three contrasting rivers in the U.K. This process removed 66–85% of the dissolved organic matter supply.
2. Elevations in extra cellular enzyme activity (β-glucosidase, phosphatase and esterase), metabolic heat-output, bacterial density and poly-beta-hydroxy alkanoate (PHA) content (a prokaryote storage product) were noted throughout the study in response to the removal of organic matter. This suggests that there are inhibitory substances present in the dissolved organic matter pool >1000 AMW. Evidence is presented to suggest that phenolics play a role in this inhibition.
3. Decreases in metabolic heat output, β-glucosidase activity and PHA content were noted at four sites in response to the removal of >1000 AMW material.
4. The divergent responses of the six river/stream biofilms are indicative of radically differing metabolic/catabolic processes, on a spatial and/or temporal basis, to a major organic supply perturbation. 相似文献
2. Elevations in extra cellular enzyme activity (β-glucosidase, phosphatase and esterase), metabolic heat-output, bacterial density and poly-beta-hydroxy alkanoate (PHA) content (a prokaryote storage product) were noted throughout the study in response to the removal of organic matter. This suggests that there are inhibitory substances present in the dissolved organic matter pool >1000 AMW. Evidence is presented to suggest that phenolics play a role in this inhibition.
3. Decreases in metabolic heat output, β-glucosidase activity and PHA content were noted at four sites in response to the removal of >1000 AMW material.
4. The divergent responses of the six river/stream biofilms are indicative of radically differing metabolic/catabolic processes, on a spatial and/or temporal basis, to a major organic supply perturbation. 相似文献
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Immobilization and mineralization of dissolved free amino acids by stream-bed biofilms 总被引:3,自引:0,他引:3
1. Radiolabelled (14C) amino acids were used to investigate the influence of sediment size as well as dissolved free amino acid (DFAA) concentration and composition on immobilization and mineralization of DFAAs by biofilms from a first-order stream. 2. Over time (240 min), biofilms on stony substrata immobilized a DFAA mixture more effectively than those on sandy substrata, however proportional mineralization of immobilized DFAAs was higher for sandy substrata (36 v 20%). 3. Using stony substrata, the DFAA mixture was immobilized more rapidly than glycine alone at ‘near-natural’ amino acid concentrations (c. 37 μgl?1), as well as enriched concentrations (1 and 100 mg 1-?1). Instantaneous rates of glycine immobilization and mineralization were not saturated at glycine enrichments of up to 980 mgl?1. 4. With both the amino acid mixture and glycine alone, proportional mineralization of the immobilized amino acids increased on enrichment to Img 1-?1 (DFAA mixture: from 25 to 37%; glycine alone: from 50 to 54%), but then fell on further enrichment to 100mgl?1 (DFAA mixture: 11%; glycine alone: 7%). 5. Results are discussed in terms of the potential trophic utility of immobilized DFAAs as well as the apparent roles of biotic and abiotic immobilization mechanisms. Immobilization and mineralization responses to variables investigated in this study give an insight into potential variability of carbon immobilization and retention in stream-bed sediments. This is fundamental to an understanding of how DOC may become available to higher trophic levels. 相似文献
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