title: The role of the deposit feeding bivalve Macomona liliana in a simple biophysical model for predicting estuarine ecosystem tipping points

authors: Thomson, Taylor Scott

subjects: Macomona liliana

abstract: Estuaries are highly productive, coastal marine environments that provide vital ecosystem functions supporting human health. Throughout history, many major settlements have been established adjacent to estuaries, so to take advantage of the resources they provide. After centuries of exploitation and heavy pollution, the health of estuaries have experienced a notable decline. The need for effective management strategies has arisen, but their efficacy continues to be questioned due to the dynamic and unpredictable nature of these environments. Non-linear processes, such as regime shifts, make long-term predictions of ecosystem health a point of concern. To combat this issue in New Zealand, ecosystem interaction networks (EINs) have been used to predict the future health of estuaries using long-term statistical modelling. Unfortunately, these models fail to capture the coupling interactions between biotic and abiotic variables that occur in such a volatile environment. Therefore, we have created a simple model design that replicates the dynamic ecosystem interactions found within the benthic environments of New Zealand estuaries, with a specific focus on the behaviour of the keystone bivalve species Macomona liliana. A multitude of biophysical dynamical models currently exist in this field (e.g. Delft3D and DELWAQ); however none with the ability to replicate the exchange of nutrients between the sediment and benthic layer caused by M. liliana pumping behaviour. Consequently, this makes our model the first of its kind. Our model design simulates the variation of three dynamic variables (biomass, nutrients, detritus) corresponding to the interactions of M. liliana and microphytobenthos (MPB) at a representative site of New Zealand sandy bottom estuaries (Tuapiro Point, Tauranga Harbour). Extensive testing was conducted to ensure that, at the baseline level, the model’s output was consistent with field sampling data seen within the literature. Once completed, the model was tested against external forcing factors that are likely to occur within New Zealand estuaries – turbidity, sedimentation, and external nutrient loading. We found that our system is light limited, with M. liliana and MPB biomasses both declining with increasing turbidity. MPB populations fluctuate significantly following a sediment mud content increase, which we believe demonstrates a reaction to an ecological tipping point being surpassed. Furthermore, we found that a significant influx of external nutrient loading is required to initiate a MPB bloom, which the system cannot maintain despite nutrient levels remaining high. Our model’s results are in agreement with estuarine responses seen in the past, with our design exceeding the guidelines surrounding the efficacy in predicting ecosystem tipping points. Therefore, due to its unique ability to demonstrate the interactions within coupled systems and its broad applicability globally, we believe our model can become a central component of future estuarine management strategies. Recommendations are made for future improvements to the model design, increasing both its range of simulated ecological processes and the validity of its predictions.

text: The role of the deposit feeding bivalve Macomona liliana in a simple biophysical model for predicting estuarine ecosystem tipping points Estuaries are highly productive, coastal marine environments that provide vital ecosystem functions supporting human health. Throughout history, many major settlements have been established adjacent to estuaries, so to take advantage of the resources they provide. After centuries of exploitation and heavy pollution, the health of estuaries have experienced a notable decline. The need for effective management strategies has arisen, but their efficacy continues to be questioned due to the dynamic and unpredictable nature of these environments. Non-linear processes, such as regime shifts, make long-term predictions of ecosystem health a point of concern. To combat this issue in New Zealand, ecosystem interaction networks (EINs) have been used to predict the future health of estuaries using long-term statistical modelling. Unfortunately, these models fail to capture the coupling interactions between biotic and abiotic variables that occur in such a volatile environment. Therefore, we have created a simple model design that replicates the dynamic ecosystem interactions found within the benthic environments of New Zealand estuaries, with a specific focus on the behaviour of the keystone bivalve species Macomona liliana. A multitude of biophysical dynamical models currently exist in this field (e.g. Delft3D and DELWAQ); however none with the ability to replicate the exchange of nutrients between the sediment and benthic layer caused by M. liliana pumping behaviour. Consequently, this makes our model the first of its kind. Our model design simulates the variation of three dynamic variables (biomass, nutrients, detritus) corresponding to the interactions of M. liliana and microphytobenthos (MPB) at a representative site of New Zealand sandy bottom estuaries (Tuapiro Point, Tauranga Harbour). Extensive testing was conducted to ensure that, at the baseline level, the model’s output was consistent with field sampling data seen within the literature. Once completed, the model was tested against external forcing factors that are likely to occur within New Zealand estuaries – turbidity, sedimentation, and external nutrient loading. We found that our system is light limited, with M. liliana and MPB biomasses both declining with increasing turbidity. MPB populations fluctuate significantly following a sediment mud content increase, which we believe demonstrates a reaction to an ecological tipping point being surpassed. Furthermore, we found that a significant influx of external nutrient loading is required to initiate a MPB bloom, which the system cannot maintain despite nutrient levels remaining high. Our model’s results are in agreement with estuarine responses seen in the past, with our design exceeding the guidelines surrounding the efficacy in predicting ecosystem tipping points. Therefore, due to its unique ability to demonstrate the interactions within coupled systems and its broad applicability globally, we believe our model can become a central component of future estuarine management strategies. Recommendations are made for future improvements to the model design, increasing both its range of simulated ecological processes and the validity of its predictions.

year: 2022

title: Cyclorheniated Azabutadienes and Their Reactions with Unsaturated Molecules

authors: Asamizu, Toshie

subjects: Cyclometalated azabutadiene

abstract: This thesis reports the studies on the reaction of 1-azabutadienes with PhCH2Re(CO)5 to prepare the cyclometallated azabutadiene tetracarbonyl compounds.

Three 1-azabutadienes with different reactivity on the N and C-1 carbons were prepared and their reactions with PhCH2Re(CO)5 were investigated.

All the reactions gave a mixture of the cyclorheniated azabutadienes and the isomers of the substituted derivatives formed by substitution by a second azabutadiene.

The substituted derivatives as the mixture were always the main products of the reactions and were obtained in good-to-excellent yield even under modified conditions intended to optimise the yield of the cyclorheniated azabutadienes. The yield could not be improved beyond 30 %. Isomerisation of the azabutadiene about the N=C bond provided very rare cis-azabutadiene metal complexes. NMR studies on the mixture of the two isomers and suggested that the product ratio depended on the molar ratio of PhCH2Re(CO)5 in the reaction mixtures.

The reactions gave the Re analogues of the products obtained in the corresponding Mn reactions.

All the compounds were characterised spectroscopically as well as by microanalysis and examples of all three types were structurally determined by X-ray crystallography. 

The reactions of the substituted derivative as the mixture of the two isomers with unsaturated molecules including phenyl acetylene, p-methoxyphenyl isocyanide, and phenyl isocyanate and methyl acrylate were investigated.

text: Cyclorheniated Azabutadienes and Their Reactions with Unsaturated Molecules This thesis reports the studies on the reaction of 1-azabutadienes with PhCH2Re(CO)5 to prepare the cyclometallated azabutadiene tetracarbonyl compounds.

Three 1-azabutadienes with different reactivity on the N and C-1 carbons were prepared and their reactions with PhCH2Re(CO)5 were investigated.

All the reactions gave a mixture of the cyclorheniated azabutadienes and the isomers of the substituted derivatives formed by substitution by a second azabutadiene.

The substituted derivatives as the mixture were always the main products of the reactions and were obtained in good-to-excellent yield even under modified conditions intended to optimise the yield of the cyclorheniated azabutadienes. The yield could not be improved beyond 30 %. Isomerisation of the azabutadiene about the N=C bond provided very rare cis-azabutadiene metal complexes. NMR studies on the mixture of the two isomers and suggested that the product ratio depended on the molar ratio of PhCH2Re(CO)5 in the reaction mixtures.

The reactions gave the Re analogues of the products obtained in the corresponding Mn reactions.

All the compounds were characterised spectroscopically as well as by microanalysis and examples of all three types were structurally determined by X-ray crystallography. 

The reactions of the substituted derivative as the mixture of the two isomers with unsaturated molecules including phenyl acetylene, p-methoxyphenyl isocyanide, and phenyl isocyanate and methyl acrylate were investigated.

year: 2009

title: Planning and governance under the LGA: Lessons from the RMA experience.

authors: Borrie, Nancy

subjects: New Zealand

abstract: The purpose of this report is to identify ways in which experiences gained from the
RMA as a devolved and co-operative planning mandate can enable local and central
government and other stakeholders to more effectively implement the LGA. The
report is based on findings from the FRST-funded research programme on Planning
under Co-operative Mandates (PUCM). We argue in this report that the experiences gained from the RMA can inform
effective implementation of the LGA in three important respects: Preparation and implementation of LTCCPs; The community consultation process for formulating community outcomes;
and Māori participation in planning and governance.

text: Planning and governance under the LGA: Lessons from the RMA experience. The purpose of this report is to identify ways in which experiences gained from the
RMA as a devolved and co-operative planning mandate can enable local and central
government and other stakeholders to more effectively implement the LGA. The
report is based on findings from the FRST-funded research programme on Planning
under Co-operative Mandates (PUCM). We argue in this report that the experiences gained from the RMA can inform
effective implementation of the LGA in three important respects: Preparation and implementation of LTCCPs; The community consultation process for formulating community outcomes;
and Māori participation in planning and governance.

year: 2004-06-01