title: Nitrogenase activity associated with codium species from New Zealand marine habitats

authors: Dormgoole, F. I.

subjects: biology

abstract: Nitrogenase activity, measured as acetylene reduction, was recorded at rates up to 1028 nmol.h \g * dry weight for Codium adhaerens (Cabr.) Ag. var. convolutum Dellow and Codium fragile (Sur.) Hariot subsp. tomentosoides (Van Goor) Silva collected from New Zealand habitats. In both species the ability to reduce acetylene is invariably associated with the presence of a heterocystous blue-green alga, Calothrix sp., epiphytic or embedded in the Codium thallus. A highly significant (P < 0.001) correlation between heterocyst frequency and nitrogenase activity was found. Nitrogenase and net photosynthesis of the Codium-Calothrix system have different steady-state responses to light intensity, and the kinetics of the two processes also differ in that nitrogenase is slow to respond to illumination or darkening. Glucose additions to Codium did not significantly increase nitrogenase activity. Nitrogenase is relatively insensitive to oxygen tension over the range 0-1.0 atm (0-1.033 kgf.cnT2) and still occurs at 1.5 atm (1.55 kgf.cm"2); this condition is unique in all nitrogenase systems thus far reported. Collectively these facts suggest that Calothrix is the agent primarily responsible for nitrogenase activity in these Codium species.

text: Nitrogenase activity associated with codium species from New Zealand marine habitats Nitrogenase activity, measured as acetylene reduction, was recorded at rates up to 1028 nmol.h \g * dry weight for Codium adhaerens (Cabr.) Ag. var. convolutum Dellow and Codium fragile (Sur.) Hariot subsp. tomentosoides (Van Goor) Silva collected from New Zealand habitats. In both species the ability to reduce acetylene is invariably associated with the presence of a heterocystous blue-green alga, Calothrix sp., epiphytic or embedded in the Codium thallus. A highly significant (P < 0.001) correlation between heterocyst frequency and nitrogenase activity was found. Nitrogenase and net photosynthesis of the Codium-Calothrix system have different steady-state responses to light intensity, and the kinetics of the two processes also differ in that nitrogenase is slow to respond to illumination or darkening. Glucose additions to Codium did not significantly increase nitrogenase activity. Nitrogenase is relatively insensitive to oxygen tension over the range 0-1.0 atm (0-1.033 kgf.cnT2) and still occurs at 1.5 atm (1.55 kgf.cm"2); this condition is unique in all nitrogenase systems thus far reported. Collectively these facts suggest that Calothrix is the agent primarily responsible for nitrogenase activity in these Codium species.

year: 1978

title: Export participation, employee benefits, and firm performance: The evidence from Vietnam’s manufacturing SMEs

authors: Vu, Van Huong

abstract: Vietnam has seen a significant rise in the number of SMEs since introducing the Enterprise Law in 2000. Non-state SMEs are playing a key role in economic growth, creating jobs, and reducing poverty. However, these non-state SMEs   participate only modestly in export activity despite the high export performance of the economy. What are the factors impeding export participation? And how does the role of export performance affect employee benefits (e.g. higher wages) and firm performance? This thesis is the first study to provide empirical evidence for answering these research questions.

Chapter 3 investigates the causal relationship between export participation and productivity by examining two popular hypotheses, self-selection and learning by exporting. Using a balanced panel dataset from 2005-2009 for Vietnamese private manufacturing SMEs, the results show strong statistical evidence for the self-selection of more productive firms into the export market. The alternative hypothesis, learning by exporting, is shown to be invalid by employing a fixed-effect panel data estimation and a fixed-effect instrumental variable regression. This study also reveals that export participation has no impact on technical efficiency, technical progress, and scale change.  

Chapter 4 explores the role of export participation in increasing employee benefits in terms of wages and employment quality.  First, based on a unique, matched firm-worker panel dataset between 2007 and 2009, the study shows that export participation has a positive impact on wages when taking into account only firm characteristics. However, the exporter wage premium falls and dissipates when both firm and worker characteristics are controlled for. In addition, the    effect decreases further and becomes less significant when controlling for time-invariant, unobservable factors by a spell fixed-effect estimation.   Second, using a firm level balanced panel dataset in the same period, the results show that there is a positive linkage between export participation and the share of casual workers. However, the effect of export participation on wages and employment quality varies greatly across sectors. 

Chapter 5 investigates linkages between export participation, firm survival and profitability in Vietnam. Using an unbalanced panel dataset from 2005 to 2009, the study shows no difference in survival probability between exporters and non-exporters. However, the probability of a firm’s survival is greater for those who engage continuously in export but is lower for firms which have ceased export activity, as indicated by their export status at different stages. Using ordinary least squares (OLS) to consider the relationship between firm profitability and export activity, the results indicate that export status is not related to firm profit growth. However, a quantile regression approach shows that export participation is positively related to profitability for firms with high profit growth but negatively related for those firms with low profit growth. This might suggest that the productivity advantages of exporters with low profit growth are absorbed by costs relating to trading activities in overseas markets.

This thesis may have several potential policy implications. First, export promotion policies may not be effective if they are not accompanied by strategies to help SMEs become more productive. In addition, policies encouraging and supporting exports should focus not only on the number of employment created but also on the quality of employment, especially for low-technology industries. Finally, export-promoting policies (e.g. improvement in firms’ innovative activities) coupled with policies maintaining firms’ positions in export markets could be helpful since these measures in turn may help firms improve their survival probability and profit growth. However, the policy issues are very complicated and these suggestions should therefore be considered an initial foundation for further study.

text: Export participation, employee benefits, and firm performance: The evidence from Vietnam’s manufacturing SMEs Vietnam has seen a significant rise in the number of SMEs since introducing the Enterprise Law in 2000. Non-state SMEs are playing a key role in economic growth, creating jobs, and reducing poverty. However, these non-state SMEs   participate only modestly in export activity despite the high export performance of the economy. What are the factors impeding export participation? And how does the role of export performance affect employee benefits (e.g. higher wages) and firm performance? This thesis is the first study to provide empirical evidence for answering these research questions.

Chapter 3 investigates the causal relationship between export participation and productivity by examining two popular hypotheses, self-selection and learning by exporting. Using a balanced panel dataset from 2005-2009 for Vietnamese private manufacturing SMEs, the results show strong statistical evidence for the self-selection of more productive firms into the export market. The alternative hypothesis, learning by exporting, is shown to be invalid by employing a fixed-effect panel data estimation and a fixed-effect instrumental variable regression. This study also reveals that export participation has no impact on technical efficiency, technical progress, and scale change.  

Chapter 4 explores the role of export participation in increasing employee benefits in terms of wages and employment quality.  First, based on a unique, matched firm-worker panel dataset between 2007 and 2009, the study shows that export participation has a positive impact on wages when taking into account only firm characteristics. However, the exporter wage premium falls and dissipates when both firm and worker characteristics are controlled for. In addition, the    effect decreases further and becomes less significant when controlling for time-invariant, unobservable factors by a spell fixed-effect estimation.   Second, using a firm level balanced panel dataset in the same period, the results show that there is a positive linkage between export participation and the share of casual workers. However, the effect of export participation on wages and employment quality varies greatly across sectors. 

Chapter 5 investigates linkages between export participation, firm survival and profitability in Vietnam. Using an unbalanced panel dataset from 2005 to 2009, the study shows no difference in survival probability between exporters and non-exporters. However, the probability of a firm’s survival is greater for those who engage continuously in export but is lower for firms which have ceased export activity, as indicated by their export status at different stages. Using ordinary least squares (OLS) to consider the relationship between firm profitability and export activity, the results indicate that export status is not related to firm profit growth. However, a quantile regression approach shows that export participation is positively related to profitability for firms with high profit growth but negatively related for those firms with low profit growth. This might suggest that the productivity advantages of exporters with low profit growth are absorbed by costs relating to trading activities in overseas markets.

This thesis may have several potential policy implications. First, export promotion policies may not be effective if they are not accompanied by strategies to help SMEs become more productive. In addition, policies encouraging and supporting exports should focus not only on the number of employment created but also on the quality of employment, especially for low-technology industries. Finally, export-promoting policies (e.g. improvement in firms’ innovative activities) coupled with policies maintaining firms’ positions in export markets could be helpful since these measures in turn may help firms improve their survival probability and profit growth. However, the policy issues are very complicated and these suggestions should therefore be considered an initial foundation for further study.

year: 2014

title: Microplastics in the marine environment: Sediment contaminant and bioaccumulation rates in bivalves within the Bay of Plenty

authors: Lewis, Anita

subjects: Microplastic

abstract: Microplastic pollution is recognised as a significant anthropogenic issue in coastal ecosystems around the world. The accumulation of microplastics in coastal environments causes both direct and indirect effects on these already vulnerable ecosystems. Limited information was available of the scale of microplastic pollution across New Zealand, including the Bay of Plenty. To enable a greater understanding of microplastic accumulation in sediment and bioaccumulation in bivalves sampling  within the Bay of Plenty area was conducted.
The presence of  microplastic particles was investigated from sediment and shellfish samples collected across the Bay of Plenty, from Waihī Beach in the West, to Ōpōtiki in the East. Three species of shellfish were collected that differed in their functional feeding modes (filter feeder vs deposit feeder): tuangi (cockle: Austrovenus stuchburyi), hanikura (wedge shell: Macomona liliana), and tuatua (surf clam: Paphies subtriangulata). Microplastic particles from sediment and bivalves were separated from the sediment and shellfish samples in the laboratory and identified using visual light stereomicroscopy. Microplastic particles were identified and quantified into three categories: fragments, fibres, and films. 
Significant numbers of fibres, as well as some fragments and films were found to be present in the sediment throughout all sampling locations. The highest density of microplastic particles in sediment (up to 11,087.9 per m²) were observed at sites that were closed to municipal sewage outfalls and populated areas, and the lowest densities were observed at Matakana Island (63 particles per m²). Sites in Ōhiwa Harbour showed an average of 504.6 particles per m² at the high tide zone and 477.6 particles per m² at the intertidal zone in the sediment. Ohiwa Harbour showed similar levels of microplastic accumulation in sediment compared to Tauranga Harbour. However, higher levels of microplastic particles were found in the sediment at open coast sites.
All shellfish sampled had at least one microplastic particle found in their tissues. The highest number of microplastics in shellfish were found in the wedge shell (23 particles), with the least from the cockles (1). Statistical analysis reveal that the deep burrowing deposit feeder (Macomona liliana) demonstrated an elevated amount of microplastic particles ingested relative to the shallow burrowing suspension feeding cockle (Austrovenus stutchburyi). A notable amount of microplastic particles were also found at all sampling locations for the culturally important tuatua (Paphies subtriangulata). However, comparing all three bivalve species, the deposit feeding M. liliana, ingested higher amounts than both the A. stutchburyi and P. subtriangulata, which could be related to their different functional feeding modes in the marine environment. This research provides baseline information to assess the extent of microplastic pollution in sediments and the potential for bioaccumulation in bivalve species with differentiated feeding modes and functional roles in the marine environment. 
The problem with microplastics is a global emerging contaminant. Preventing the problem of plastic wastes in New Zealand will require change across all aspects of society, along with policy regulations to mitigate the issue of microplastic pollution.

text: Microplastics in the marine environment: Sediment contaminant and bioaccumulation rates in bivalves within the Bay of Plenty Microplastic pollution is recognised as a significant anthropogenic issue in coastal ecosystems around the world. The accumulation of microplastics in coastal environments causes both direct and indirect effects on these already vulnerable ecosystems. Limited information was available of the scale of microplastic pollution across New Zealand, including the Bay of Plenty. To enable a greater understanding of microplastic accumulation in sediment and bioaccumulation in bivalves sampling  within the Bay of Plenty area was conducted.
The presence of  microplastic particles was investigated from sediment and shellfish samples collected across the Bay of Plenty, from Waihī Beach in the West, to Ōpōtiki in the East. Three species of shellfish were collected that differed in their functional feeding modes (filter feeder vs deposit feeder): tuangi (cockle: Austrovenus stuchburyi), hanikura (wedge shell: Macomona liliana), and tuatua (surf clam: Paphies subtriangulata). Microplastic particles from sediment and bivalves were separated from the sediment and shellfish samples in the laboratory and identified using visual light stereomicroscopy. Microplastic particles were identified and quantified into three categories: fragments, fibres, and films. 
Significant numbers of fibres, as well as some fragments and films were found to be present in the sediment throughout all sampling locations. The highest density of microplastic particles in sediment (up to 11,087.9 per m²) were observed at sites that were closed to municipal sewage outfalls and populated areas, and the lowest densities were observed at Matakana Island (63 particles per m²). Sites in Ōhiwa Harbour showed an average of 504.6 particles per m² at the high tide zone and 477.6 particles per m² at the intertidal zone in the sediment. Ohiwa Harbour showed similar levels of microplastic accumulation in sediment compared to Tauranga Harbour. However, higher levels of microplastic particles were found in the sediment at open coast sites.
All shellfish sampled had at least one microplastic particle found in their tissues. The highest number of microplastics in shellfish were found in the wedge shell (23 particles), with the least from the cockles (1). Statistical analysis reveal that the deep burrowing deposit feeder (Macomona liliana) demonstrated an elevated amount of microplastic particles ingested relative to the shallow burrowing suspension feeding cockle (Austrovenus stutchburyi). A notable amount of microplastic particles were also found at all sampling locations for the culturally important tuatua (Paphies subtriangulata). However, comparing all three bivalve species, the deposit feeding M. liliana, ingested higher amounts than both the A. stutchburyi and P. subtriangulata, which could be related to their different functional feeding modes in the marine environment. This research provides baseline information to assess the extent of microplastic pollution in sediments and the potential for bioaccumulation in bivalve species with differentiated feeding modes and functional roles in the marine environment. 
The problem with microplastics is a global emerging contaminant. Preventing the problem of plastic wastes in New Zealand will require change across all aspects of society, along with policy regulations to mitigate the issue of microplastic pollution.

year: 2021