title: The temperature optima of enzymes: a new perspective on an old phenomenon

authors: Daniel, Roy M.

subjects: temperature optima

abstract: Careful analysis of the dependence of enzyme activity on assay temperature has revealed that some enzymes might have real temperature optima in which the decrease in catalytic rate at temperatures above the optimum is not primarily a result of irreversible thermal inactivation. The ‘equilibrium model’ has been formulated to describe genuine temperature optima, and to suggest a simple experimental method by which to distinguish these cases from those in which enzyme instability is the major determinant of temperature optima.

text: The temperature optima of enzymes: a new perspective on an old phenomenon Careful analysis of the dependence of enzyme activity on assay temperature has revealed that some enzymes might have real temperature optima in which the decrease in catalytic rate at temperatures above the optimum is not primarily a result of irreversible thermal inactivation. The ‘equilibrium model’ has been formulated to describe genuine temperature optima, and to suggest a simple experimental method by which to distinguish these cases from those in which enzyme instability is the major determinant of temperature optima.

year: 2001-04

title: Is fish food from aquarium suppliers a vector for non-native zooplankton to New Zealand?

authors: Mahaarachchige, Buddhika Udayangani Perera

subjects: Artemia

abstract: There have been a number of recent records of non-native zooplankton invasions in New Zealand, but the transport vectors leading to their introduction are not well understood.  Commercially available fish foods containing zooplankton are widely used in home aquariums and the aquaculture industry. These foods are either imported to, or cultured within, New Zealand, and sold as freeze-dried, sun-dried or frozen adults, as capsulated or decapsulated cysts, or as live individuals. In this study, fish food containing Daphnia O.F. Müller, 1785  (Cladocera), Artemia (brine shrimp) and Brachionus (rotifers) were bought from a variety of commercial suppliers within the North Island, New Zealand, which were cultured and manufactured domestically or internationally. Live Daphnia samples were identified morphologically and were found to contain a variety of both native and non-native Daphnia species, as well as copepods, ostracods, rotifers and other non-Daphnia cladoceran species. Freeze-dried and sun-dried diapausing eggs of Daphnia and the rotifer Brachionus were incubated in artificial pond water, Aachener Daphnien Medium (ADaM) and filtered pond water, but hatching of these were unsuccessful. In contrast, Artemia bought as both capsulated and decapsulated cysts were successfully hatched in water with a salinity of 25 ppt and temperatures of 20 °C. The resulting Artemia populations were either parthenogenic or sexual, varying by manufacturer. Frozen whole adult Artemia were found to carry eggs but could not be hatched. Due to the risk of misidentifications from morphological identification, a 658-bp fragment from the 5ʹ region of the COI gene was amplified from tissue samples. The phylogenetic tree constructed from the COI gene sequences identified distinct clades corresponding to four species: A. franciscana, A. parthenogenetica (both hatched from eggs as viable populations), A. sinica, and A. salina (both identified in food, but not viable). The BLAST analysis indicated that the capsulated  cysts from USA and German manufacturers contained Artemia franciscana, while the Chinese supply contained A. parthenogenetica. Decapsulated cysts from a Chinese manufacturer hatched into A. parthenogenetica. While A. franciscana can be legally imported into New Zealand, A. parthenogenetica is not listed in the Import Health Standard for ‘Fish food and fish bait’ under the Biosecurity Act 1993. The morphological identifications matched the BLAST analysis data for Daphnia. Non-native Daphnia pulex was recorded from live samples from Te Aroha, Hamilton and Wellington (LID5). An Auckland sample and another Wellington sample comprised of native D. carinata s.l. Overall, commercially available fish food from aquarium suppliers can act as a vector for non-native zooplankton to New Zealand.

text: Is fish food from aquarium suppliers a vector for non-native zooplankton to New Zealand? There have been a number of recent records of non-native zooplankton invasions in New Zealand, but the transport vectors leading to their introduction are not well understood.  Commercially available fish foods containing zooplankton are widely used in home aquariums and the aquaculture industry. These foods are either imported to, or cultured within, New Zealand, and sold as freeze-dried, sun-dried or frozen adults, as capsulated or decapsulated cysts, or as live individuals. In this study, fish food containing Daphnia O.F. Müller, 1785  (Cladocera), Artemia (brine shrimp) and Brachionus (rotifers) were bought from a variety of commercial suppliers within the North Island, New Zealand, which were cultured and manufactured domestically or internationally. Live Daphnia samples were identified morphologically and were found to contain a variety of both native and non-native Daphnia species, as well as copepods, ostracods, rotifers and other non-Daphnia cladoceran species. Freeze-dried and sun-dried diapausing eggs of Daphnia and the rotifer Brachionus were incubated in artificial pond water, Aachener Daphnien Medium (ADaM) and filtered pond water, but hatching of these were unsuccessful. In contrast, Artemia bought as both capsulated and decapsulated cysts were successfully hatched in water with a salinity of 25 ppt and temperatures of 20 °C. The resulting Artemia populations were either parthenogenic or sexual, varying by manufacturer. Frozen whole adult Artemia were found to carry eggs but could not be hatched. Due to the risk of misidentifications from morphological identification, a 658-bp fragment from the 5ʹ region of the COI gene was amplified from tissue samples. The phylogenetic tree constructed from the COI gene sequences identified distinct clades corresponding to four species: A. franciscana, A. parthenogenetica (both hatched from eggs as viable populations), A. sinica, and A. salina (both identified in food, but not viable). The BLAST analysis indicated that the capsulated  cysts from USA and German manufacturers contained Artemia franciscana, while the Chinese supply contained A. parthenogenetica. Decapsulated cysts from a Chinese manufacturer hatched into A. parthenogenetica. While A. franciscana can be legally imported into New Zealand, A. parthenogenetica is not listed in the Import Health Standard for ‘Fish food and fish bait’ under the Biosecurity Act 1993. The morphological identifications matched the BLAST analysis data for Daphnia. Non-native Daphnia pulex was recorded from live samples from Te Aroha, Hamilton and Wellington (LID5). An Auckland sample and another Wellington sample comprised of native D. carinata s.l. Overall, commercially available fish food from aquarium suppliers can act as a vector for non-native zooplankton to New Zealand.

year: 2025

title: The use of functionalised biochar to enhance phosphorus removal in woodchip bioreactors. The integration of mātauranga Māori to enhance the cultural aspects of woodchip bioreactors.

authors: Taoho, Brandon

subjects: Woodchip bioreactor

abstract: Nutrient pollution, resulting from excessive releases of nitrogen (N) and phosphorus (P) into waterways, poses a significant threat to aquatic ecosystems worldwide. Elevated nutrient levels can result in eutrophication, which can have detrimental effects on the health of waterbodies and their biota. Woodchip bioreactors are effective, edge-of-field technologies that can help mitigate nutrient pollution by lowering nutrient concentrations in agricultural drainage systems known to carry leached N and P into waterways. However, one limitation to their design is their ineffectiveness at removing P. The inclusion of functionalised biochar is one potential solution to enhance P removal in woodchip bioreactors. There is a growing need to mitigate nutrient pollution in New Zealand that does not depend on a western-centric perspective only. Integration of mātauranga Māori and western science into the design and operations of a woodchip bioreactor is one approach to incorporate both knowledge systems to the goal of mitigating nutrient pollution. In this dissertation, a column experiment was used to compare the P removal efficiencies of two treatments of functionalised biochar, and one treatment of woodchips when subjected to stream water spiked with P. Subsequently, a single phosphate extraction was done to determine the phosphate absorption capacities of each treatment. The results showed that the two functionalised biochar treatments had the highest efficacy in reducing P concentrations in the P-spiked stream water compared to the woodchip-only treatment. Both treatments also showed higher P absorption, evidenced from the Fe-P/Feox ratio, within the phosphate extraction experiment. A wānanga was organised at Matahuru Marae, Lake Waikare, to share mātauranga Māori on how to culturally enhance woodchip bioreactors from a Te Ao Māori perspective. Participants recommended that native woodchips be incorporated into woodchip bioreactors because of their inherent association to the land and people. Overall, the results implied that functionalised biochar is an effective solution to enhance P removal in woodchip bioreactors due to their biophysical properties to absorb and retain P. Secondly, incorporating native woodchips into woodchip bioreactors systems potentially offers a sustainable and culturally respected alternative to conventional wood chips, aligning with Māori values and tikanga

text: The use of functionalised biochar to enhance phosphorus removal in woodchip bioreactors. The integration of mātauranga Māori to enhance the cultural aspects of woodchip bioreactors. Nutrient pollution, resulting from excessive releases of nitrogen (N) and phosphorus (P) into waterways, poses a significant threat to aquatic ecosystems worldwide. Elevated nutrient levels can result in eutrophication, which can have detrimental effects on the health of waterbodies and their biota. Woodchip bioreactors are effective, edge-of-field technologies that can help mitigate nutrient pollution by lowering nutrient concentrations in agricultural drainage systems known to carry leached N and P into waterways. However, one limitation to their design is their ineffectiveness at removing P. The inclusion of functionalised biochar is one potential solution to enhance P removal in woodchip bioreactors. There is a growing need to mitigate nutrient pollution in New Zealand that does not depend on a western-centric perspective only. Integration of mātauranga Māori and western science into the design and operations of a woodchip bioreactor is one approach to incorporate both knowledge systems to the goal of mitigating nutrient pollution. In this dissertation, a column experiment was used to compare the P removal efficiencies of two treatments of functionalised biochar, and one treatment of woodchips when subjected to stream water spiked with P. Subsequently, a single phosphate extraction was done to determine the phosphate absorption capacities of each treatment. The results showed that the two functionalised biochar treatments had the highest efficacy in reducing P concentrations in the P-spiked stream water compared to the woodchip-only treatment. Both treatments also showed higher P absorption, evidenced from the Fe-P/Feox ratio, within the phosphate extraction experiment. A wānanga was organised at Matahuru Marae, Lake Waikare, to share mātauranga Māori on how to culturally enhance woodchip bioreactors from a Te Ao Māori perspective. Participants recommended that native woodchips be incorporated into woodchip bioreactors because of their inherent association to the land and people. Overall, the results implied that functionalised biochar is an effective solution to enhance P removal in woodchip bioreactors due to their biophysical properties to absorb and retain P. Secondly, incorporating native woodchips into woodchip bioreactors systems potentially offers a sustainable and culturally respected alternative to conventional wood chips, aligning with Māori values and tikanga

year: 2023