Community metabolism and phosphorus dynamics in a seasonally closed South African estuary
- Liptrot, Mark Robert Michael
- Authors: Liptrot, Mark Robert Michael
- Date: 1978
- Subjects: Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5810 , http://hdl.handle.net/10962/d1006966 , Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Description: The effects of seawater inflows and macrophyte beds on community metabolism and phosphorus dynamics in the seasonally-closed Swartvlei estuary were investigated. Metabolic rates were determined by diurnal oxygen curve analysis. Gross primary production ranged from 0,7 to 14,9 g 0₂ m⁻² day⁻¹, and respiration from 0,9 to 25,2 g 0₂ m⁻² day⁻¹. The highest production rates were recorded inside the dense beds of Zostera capens is Setchell (x- = 7,8 g 0₂ m⁻² day⁻¹ ). Metabolism was positively correlated to submersed macrophyte cover, and decreased upstream of the mouth region. No seasonal variation in gross production could be detected, and mouth closure had no detectable effect on metabolic rates. Growth of the green alga Enteromorpha sp. in winter, and the effect of decay of this alga on dissolved oxygen, total inorganic carbon and total dissolved phosphorus in the water column is discussed. High day-time respiration values, measured in a darkened polythene enclosure, indicate that photorespiration occurs in Zostera. Apparently the annual amount of oxygen respired throughout the estuary exceeded that produced by 2 7100 tonnes, i.e. the estuary was heterotrophic. This is discussed in relation to the effectiveness of the diurnal curve method as a way of measuring metabolic rates, and to the possibility of organic matter input via river inflows. There is a net gain of up to 17,4 kg of particulate phosphorus over mean tides. Diurnal phosphorus studies indicate that Zostera releases phosphate into the water column in the light. Enteromorpha takes up phosphate in the morning, which it appears to release over the rest of the day. The cycling of phosphorus between seawater, sediments, macrophytes and the water column is discussed.
- Full Text:
- Date Issued: 1978
- Authors: Liptrot, Mark Robert Michael
- Date: 1978
- Subjects: Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5810 , http://hdl.handle.net/10962/d1006966 , Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Description: The effects of seawater inflows and macrophyte beds on community metabolism and phosphorus dynamics in the seasonally-closed Swartvlei estuary were investigated. Metabolic rates were determined by diurnal oxygen curve analysis. Gross primary production ranged from 0,7 to 14,9 g 0₂ m⁻² day⁻¹, and respiration from 0,9 to 25,2 g 0₂ m⁻² day⁻¹. The highest production rates were recorded inside the dense beds of Zostera capens is Setchell (x- = 7,8 g 0₂ m⁻² day⁻¹ ). Metabolism was positively correlated to submersed macrophyte cover, and decreased upstream of the mouth region. No seasonal variation in gross production could be detected, and mouth closure had no detectable effect on metabolic rates. Growth of the green alga Enteromorpha sp. in winter, and the effect of decay of this alga on dissolved oxygen, total inorganic carbon and total dissolved phosphorus in the water column is discussed. High day-time respiration values, measured in a darkened polythene enclosure, indicate that photorespiration occurs in Zostera. Apparently the annual amount of oxygen respired throughout the estuary exceeded that produced by 2 7100 tonnes, i.e. the estuary was heterotrophic. This is discussed in relation to the effectiveness of the diurnal curve method as a way of measuring metabolic rates, and to the possibility of organic matter input via river inflows. There is a net gain of up to 17,4 kg of particulate phosphorus over mean tides. Diurnal phosphorus studies indicate that Zostera releases phosphate into the water column in the light. Enteromorpha takes up phosphate in the morning, which it appears to release over the rest of the day. The cycling of phosphorus between seawater, sediments, macrophytes and the water column is discussed.
- Full Text:
- Date Issued: 1978
Heterotrophic carbon dioxide fixation by Euglena
- Authors: Peak, Jennifer Grace
- Date: 1978
- Subjects: Euglena
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5824 , http://hdl.handle.net/10962/d1007650
- Description: Heterotrophic (dark, non-photosynthetic) carbon dioxide fixation was measured in the phytoflagellate Euglena gracilis. Variation in heterotrophic carbon dioxide fixation depends on the phase of batch growth and the mode of nutrition. A sharp increase in heterotrophic carbon dioxide fixation occurs during the mid- to late-logarithmic growth periods in Euglena growing photoautotrophically (with carbon dioxide as carbon source, light as energy source) and heterotrophically (in the dark with glucose as sole carbon and energy source). Cells growing heterotrophically with acetate or ethanol as sole carbon source do not increase their heterotrophic carbon dioxide fixation during the growth cycle. Addition of acetate to cultures of Euglena causes a reduction in dark carbon dioxide fixation. The results are consistent with the hypothesis that heterotrophic carbon dioxide fixation in Euglena functions in anaplerotic replenishment of the tricarboxylic acid cycle. The regulation of these changes in heterotrophic carbon dioxide fixation was shown to be controlled by exogenous ammonium in a complex fashion. Ammonium stimulates heterotrophic carbon dioxide fixation after a period of ammonium deprivation. The kinetics of the regulatory effects of the ammonium ion on dark carbon dioxide fixation are presented. A survey into the activities of carboxylating enzymes from both autotrophically and heterotrophically grown Euglena was conducted. The heterotrophic cultures were supplied with either glucose or acetate as substrate. PEP carboxykinase (E.C.4.1.1.38) and (E.C.4.1.1.49) could not be detected in any of the cultures tested. A trace amount of PEP carboxykinase (E.C.4.1.1.32) is present in the acetate grown cells only and a trace amount of pyruvate carboxylase (E.C.6.4.1.1.) is present in the glucose grown cells only. Malate enzyme (E.C.1.1.1.40), PEP carboxylase (E.C.4.1.1.31) and acetylcoenzyme A carboxylase (E.C.6.4.1.2) are present in all cells tested. Ammonium stimulation causes a small increase in specific activity of all the enzymes except acetyl-CoA carboxylase. The largest increase occurs in PEP carboxylase, but the increase is not sufficient to account for observed increases in whole cell dark carbon dioxide fixation after ammonium stimulation. Two isoenzymes of PEP carboxylase were purified from each other from both ammonium stimulated and non-stimulated cells. There are no significant differences between elution profiles of isoenzymes from ammonium stimulated and control cells. There are no significant differences between elution profiles of isoenzymes from autotrophic and heterotrophic cells. The kinetics of the regulation of the two isoenzymes by malate, citrate, succinate and 3-phosphoglycerate are presented. The products of heterotrophic carbon dioxide fixation by ammonium stimulated and control cells were identified and measured by chromatography. Ammonium stimulates the biosynthesis of glutamine, glycine, serine and alanine.
- Full Text:
- Date Issued: 1978
- Authors: Peak, Jennifer Grace
- Date: 1978
- Subjects: Euglena
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5824 , http://hdl.handle.net/10962/d1007650
- Description: Heterotrophic (dark, non-photosynthetic) carbon dioxide fixation was measured in the phytoflagellate Euglena gracilis. Variation in heterotrophic carbon dioxide fixation depends on the phase of batch growth and the mode of nutrition. A sharp increase in heterotrophic carbon dioxide fixation occurs during the mid- to late-logarithmic growth periods in Euglena growing photoautotrophically (with carbon dioxide as carbon source, light as energy source) and heterotrophically (in the dark with glucose as sole carbon and energy source). Cells growing heterotrophically with acetate or ethanol as sole carbon source do not increase their heterotrophic carbon dioxide fixation during the growth cycle. Addition of acetate to cultures of Euglena causes a reduction in dark carbon dioxide fixation. The results are consistent with the hypothesis that heterotrophic carbon dioxide fixation in Euglena functions in anaplerotic replenishment of the tricarboxylic acid cycle. The regulation of these changes in heterotrophic carbon dioxide fixation was shown to be controlled by exogenous ammonium in a complex fashion. Ammonium stimulates heterotrophic carbon dioxide fixation after a period of ammonium deprivation. The kinetics of the regulatory effects of the ammonium ion on dark carbon dioxide fixation are presented. A survey into the activities of carboxylating enzymes from both autotrophically and heterotrophically grown Euglena was conducted. The heterotrophic cultures were supplied with either glucose or acetate as substrate. PEP carboxykinase (E.C.4.1.1.38) and (E.C.4.1.1.49) could not be detected in any of the cultures tested. A trace amount of PEP carboxykinase (E.C.4.1.1.32) is present in the acetate grown cells only and a trace amount of pyruvate carboxylase (E.C.6.4.1.1.) is present in the glucose grown cells only. Malate enzyme (E.C.1.1.1.40), PEP carboxylase (E.C.4.1.1.31) and acetylcoenzyme A carboxylase (E.C.6.4.1.2) are present in all cells tested. Ammonium stimulation causes a small increase in specific activity of all the enzymes except acetyl-CoA carboxylase. The largest increase occurs in PEP carboxylase, but the increase is not sufficient to account for observed increases in whole cell dark carbon dioxide fixation after ammonium stimulation. Two isoenzymes of PEP carboxylase were purified from each other from both ammonium stimulated and non-stimulated cells. There are no significant differences between elution profiles of isoenzymes from ammonium stimulated and control cells. There are no significant differences between elution profiles of isoenzymes from autotrophic and heterotrophic cells. The kinetics of the regulation of the two isoenzymes by malate, citrate, succinate and 3-phosphoglycerate are presented. The products of heterotrophic carbon dioxide fixation by ammonium stimulated and control cells were identified and measured by chromatography. Ammonium stimulates the biosynthesis of glutamine, glycine, serine and alanine.
- Full Text:
- Date Issued: 1978
The anatomy of the triassic theropod Syntarsus rhodesiensis (Saurischia : Podokesauridae) and a consideration of its biology
- Authors: Raath, M A
- Date: 1978
- Subjects: Reptiles, Fossil Dinosaurs Paleontology -- Triassic , Dinosaurs , Fossils , Reptiles , Palaeontology , Triassic period
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5601 , http://hdl.handle.net/10962/d1002051
- Description: The osteology of the Upper Triassic podokesaurid Syntarsus rhodesiensis is described, based on a series of 30+ individuals representing all skeletal elements, recovered since the description of the holotype (Raath, 1969). A brief account of the geology of the finds is given, with an attempt at a reconstruction of the palaaoenvironment. The excellence of preservation of the bones has permitted an attempt at the restoration of soft tissues including the brain, cranial nerves, main cranial blood vessels and the musculature of the jaws, neck and limbs. Histological sections of limb bones have shown that the compact bone was highly vascular, and this, together with the structure of the brain, palaeoenvironmental considerations, social behaviour and group structure, leads to the conclusion that Syntarsus was an endothermic homeotherm inhabiting a hot arid region at the end of the Triassic, with a social organisation into "flocks" in which females predominated numerically. Clear evidence of sexual dimorphism is presented. Syntarsus is reconstructed as a bipedal, saltatorial predator which differs in subtle, but probably generically significant, characteristics from the closely related North American genus, Coelophysis. Its anatomy characterises it as a medium-sized agile animal with a highly kinetic skull; incipiently opposable pollex in the raptorial manus; highly cursorial hindlimb; and with features in the dentition and hallux which suggest a grooming function. It is concluded that the Triassic coelurosaurian stock provided an advanced and well adapted base from which the successful coelurosaur radiation into the later Mesozoic sprang, and that this stock was physiologically pre-adapted for the emergence of the avian (and possibly the pterosaur) lineages in the Jurassic
- Full Text:
- Date Issued: 1978
- Authors: Raath, M A
- Date: 1978
- Subjects: Reptiles, Fossil Dinosaurs Paleontology -- Triassic , Dinosaurs , Fossils , Reptiles , Palaeontology , Triassic period
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5601 , http://hdl.handle.net/10962/d1002051
- Description: The osteology of the Upper Triassic podokesaurid Syntarsus rhodesiensis is described, based on a series of 30+ individuals representing all skeletal elements, recovered since the description of the holotype (Raath, 1969). A brief account of the geology of the finds is given, with an attempt at a reconstruction of the palaaoenvironment. The excellence of preservation of the bones has permitted an attempt at the restoration of soft tissues including the brain, cranial nerves, main cranial blood vessels and the musculature of the jaws, neck and limbs. Histological sections of limb bones have shown that the compact bone was highly vascular, and this, together with the structure of the brain, palaeoenvironmental considerations, social behaviour and group structure, leads to the conclusion that Syntarsus was an endothermic homeotherm inhabiting a hot arid region at the end of the Triassic, with a social organisation into "flocks" in which females predominated numerically. Clear evidence of sexual dimorphism is presented. Syntarsus is reconstructed as a bipedal, saltatorial predator which differs in subtle, but probably generically significant, characteristics from the closely related North American genus, Coelophysis. Its anatomy characterises it as a medium-sized agile animal with a highly kinetic skull; incipiently opposable pollex in the raptorial manus; highly cursorial hindlimb; and with features in the dentition and hallux which suggest a grooming function. It is concluded that the Triassic coelurosaurian stock provided an advanced and well adapted base from which the successful coelurosaur radiation into the later Mesozoic sprang, and that this stock was physiologically pre-adapted for the emergence of the avian (and possibly the pterosaur) lineages in the Jurassic
- Full Text:
- Date Issued: 1978
The endocoprid dung beetles of southern Africa (Coleoptera: Scarabaeidae)
- Davis, Adrian L V (Adrian Louis Victor)
- Authors: Davis, Adrian L V (Adrian Louis Victor)
- Date: 1978
- Subjects: Dung beetles -- Ecology , Dung beetles -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5845 , http://hdl.handle.net/10962/d1011030 , Dung beetles -- Ecology , Dung beetles -- Africa, Southern
- Description: The biology and ecology of the endocoprid dung beetles of the Aethiopian zoogeographic region has been studied in the field and laboratory. Work has centred mainly on Oniticellus planatus and O. formoaus although infomation has also been supplied on O. egregius, O. pictus and Tragiscus dimidiatus. The taxonomy of Onticellus (s.str.) and Tragiscus has been discussed with the recommendation that O. planattus and O. pseudaplanatus be synonymised. It has been suggested that endocoprid distribution is chiefly controlled by temperature, rainfall and the density of suitable large dung masses. On the basis of distribution it has been suggested that the taxonomic status of the subspecies of O. pictus should be reviewed. Endocoprids (genus Oniticellus (s.str.) are found throughout the warmer regions of Africa and Asia. Tragiscus is found only in Africa. Methods are described for monitoring endocoprids in the field, for distinguishing freshly emerged from older specimens, and for breeding endocoprids under laboratory conditions. It has been shown that endocoprids breed within or just beneath large dung masses unlike most other members of the Scarabaeinae which actively bury dung and construct the their broods at depth in the soil. It has been shown that there is a restriction of breeding sites available to endocoprids due to the removal of dung by the Scarabaeinae beetles and the limited space available within dung pads. This has resulted in low endocoprid population numbers, a disadvantage, which has been countered by highly specialised but opportunistic breeding habits. The requirements of dung plasticity have limited the time available for breeding activity by most endocoprids (excluding O. egresius) so that both the reproductive system and the reproductive behaviour (cf. O. planatus) are geared to rapid egg and brood production. Large numbers of follicles are able to be produced over a short period. In the probable absence of feeding, this has possibly been allowed by the involvement of a well developed fat body. The broods are tended by the parent female during larval development and the follicles are gradually resorbed, probably to prevent starvation. Ovarian recovery is rapid once feeding recommences. Behavioural mechanisms have developed which boost the number of broods constructed and the rapidity with which they are produced. The duration of endocoprid colonisation and the timing of arrival at dung is shown to be related to the rate of pad desiccation which is chiefly controlled by temperature and degree of dung removal by other dung beetles. Precipitation may also play a part. Predation by vertebrates and other insects has been noted and a number of mechanisms are described which are probably protective. Two insect parasitoids of O. formosus larvae have been recorded. The potential use of endocoprids in the Australian dung and fly control project has been discussed and it is recommended that their introduction be considered of low priority. It is suggested that the endocoprids evolved from Euoniticellus type ancestors and that their behaviour complex nidification developed in response to harsh environmental factors, chiefly the danger of desiccation and competition for dung with other dung beetles. From a consideration of brood and brood chamber construction it is suggested that O. egresius is a relatively unspecialised endocoprid which may retain dry season aestivation and has not evolved much further than its probable Euoniticellus type ancestor. The broods are coated in clay and abandoned soon after construction. Greater specialisation is shown by O. planatus and O. formosus which exhibit brooding behaviour, increasing longevity, more specialised brood protection, increased potential fecundity and continuous activity throughout the year. O. formosus shows greater specialisation in brood production than O. planatus. Greatest specialisation is found in T. dimidiatus which exhibits a precise brooding period and low egg production. Brood construction is of a similar degree of specialisation to that of O. formosus. Activity is also continuous throughout the year. The comparative biology of the five southern African endocoprids is summarised in Table 35. Summary, p. 129-131.
- Full Text:
- Date Issued: 1978
- Authors: Davis, Adrian L V (Adrian Louis Victor)
- Date: 1978
- Subjects: Dung beetles -- Ecology , Dung beetles -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5845 , http://hdl.handle.net/10962/d1011030 , Dung beetles -- Ecology , Dung beetles -- Africa, Southern
- Description: The biology and ecology of the endocoprid dung beetles of the Aethiopian zoogeographic region has been studied in the field and laboratory. Work has centred mainly on Oniticellus planatus and O. formoaus although infomation has also been supplied on O. egregius, O. pictus and Tragiscus dimidiatus. The taxonomy of Onticellus (s.str.) and Tragiscus has been discussed with the recommendation that O. planattus and O. pseudaplanatus be synonymised. It has been suggested that endocoprid distribution is chiefly controlled by temperature, rainfall and the density of suitable large dung masses. On the basis of distribution it has been suggested that the taxonomic status of the subspecies of O. pictus should be reviewed. Endocoprids (genus Oniticellus (s.str.) are found throughout the warmer regions of Africa and Asia. Tragiscus is found only in Africa. Methods are described for monitoring endocoprids in the field, for distinguishing freshly emerged from older specimens, and for breeding endocoprids under laboratory conditions. It has been shown that endocoprids breed within or just beneath large dung masses unlike most other members of the Scarabaeinae which actively bury dung and construct the their broods at depth in the soil. It has been shown that there is a restriction of breeding sites available to endocoprids due to the removal of dung by the Scarabaeinae beetles and the limited space available within dung pads. This has resulted in low endocoprid population numbers, a disadvantage, which has been countered by highly specialised but opportunistic breeding habits. The requirements of dung plasticity have limited the time available for breeding activity by most endocoprids (excluding O. egresius) so that both the reproductive system and the reproductive behaviour (cf. O. planatus) are geared to rapid egg and brood production. Large numbers of follicles are able to be produced over a short period. In the probable absence of feeding, this has possibly been allowed by the involvement of a well developed fat body. The broods are tended by the parent female during larval development and the follicles are gradually resorbed, probably to prevent starvation. Ovarian recovery is rapid once feeding recommences. Behavioural mechanisms have developed which boost the number of broods constructed and the rapidity with which they are produced. The duration of endocoprid colonisation and the timing of arrival at dung is shown to be related to the rate of pad desiccation which is chiefly controlled by temperature and degree of dung removal by other dung beetles. Precipitation may also play a part. Predation by vertebrates and other insects has been noted and a number of mechanisms are described which are probably protective. Two insect parasitoids of O. formosus larvae have been recorded. The potential use of endocoprids in the Australian dung and fly control project has been discussed and it is recommended that their introduction be considered of low priority. It is suggested that the endocoprids evolved from Euoniticellus type ancestors and that their behaviour complex nidification developed in response to harsh environmental factors, chiefly the danger of desiccation and competition for dung with other dung beetles. From a consideration of brood and brood chamber construction it is suggested that O. egresius is a relatively unspecialised endocoprid which may retain dry season aestivation and has not evolved much further than its probable Euoniticellus type ancestor. The broods are coated in clay and abandoned soon after construction. Greater specialisation is shown by O. planatus and O. formosus which exhibit brooding behaviour, increasing longevity, more specialised brood protection, increased potential fecundity and continuous activity throughout the year. O. formosus shows greater specialisation in brood production than O. planatus. Greatest specialisation is found in T. dimidiatus which exhibits a precise brooding period and low egg production. Brood construction is of a similar degree of specialisation to that of O. formosus. Activity is also continuous throughout the year. The comparative biology of the five southern African endocoprids is summarised in Table 35. Summary, p. 129-131.
- Full Text:
- Date Issued: 1978
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