title: Gracilaria transtasmanica: a potential novel target species for the bioremediation of nutrient enriched estuaries

authors: Ross, Bethany Grace

subjects: Macroalgae

abstract: Estuaries are increasingly becoming eutrophic due to anthropogenically induced nutrient enrichment. Presently, 24% of global anthropogenically derived nutrients released into coastal catchments are delivered directly into coastal waters such as estuaries. Thirty five percent of New Zealand’s estuaries are susceptible to eutrophication and some are already severely degraded. In-situ macroalgal bioremediation – the cultivation of live macroalgae directly in nutrient-enriched waters for the primary purpose of nutrient assimilation – could help prevent and reduce estuarine eutrophication.

The indigenous red macroalga Gracilaria transtasmanica has been identified as a potential target species for bioremediation in New Zealand estuaries. Samples of G. transtasmanica were collected from estuaries in the Bay of Plenty region of New Zealand, and were isolated, formally identified and scaled up into stock cultures. Controlled experiments were then used to assess the bioremediation potential of this species in winter and summer conditions under ambient and extreme nutrient and sediment levels. Biomass productivity, photosynthetic health, and N removal were assessed to quantify performance. Biomass productivity and total N removed were 45 and 50% higher respectively in summer compared to winter. Biomass productivity ranged from 0.4 – 4.3 g DW m² in summer and 0.6 – 1.8 g DW m² in winter, and total N removed ranged from 6.0 – 30.7 mg N in summer and 6.1 – 9.1 mg N in winter. In contrast, standardised N removal rates were higher in winter (37.8 mg g DW biomass growth⁻¹ ± 0.6 S.E.) compared to summer (22.3 mg g DW biomass growth⁻¹ ± 1.2 S.E.), suggesting that the biomass was storing N and therefore that N uptake was independent of productivity under sub-optimal growing conditions. Productivity was significantly affected by sediment treatment, however this effect differed seasonally, with higher productivity in the high

sediment treatments in summer, and lower productivity in the high sediment treatments in winter. These results demonstrate that G. transtasmanica can assimilate nutrients under a range of environmental conditions that are representative of both local background and high levels of suspended sediment and nutrient concentrations, and therefore is a viable target species for the bioremediation of nutrient enriched estuaries.In addition to nutrient uptake and productivity, target species for in-situ estuarine bioremediation need to maintain productivity under a range of challenging abiotic conditions. In chapter three of this thesis, a series of independent experiments assessed the tolerance of G. transtasmanica to ambient and extreme levels of salinity, exposure, and light limitation that are likely to be experienced in an estuary. Photosynthetic functioning and growth were used to quantify the tolerance range of G. transtasmanica in each experiment. Specific Growth Rate (SGR) was significantly affected by salinity, exposure, and light limitation. Gracilaria transtasmanica was able to grow in salinities ranging from 5 to 35 ppt, but growth rates decreased with decreasing salinity. Exposure periods of up to 9 hours were tolerated, but growth rates were decreased as exposure period increased. Gracilaria transtasmanica was able to maintain growth with a loss of up to 75% of ambient light and was also able to tolerate short periods of no light. Measurements of optimal quantum yields showed photosynthetic function was unaffected by salinity, exposure, or light limitation. 

These results demonstrate the high tolerance and adaptability of G. transtasmanica to a broad range of challenging abiotic estuarine conditions. In combination, these findings demonstrate that Gracilaria transtasmanica is well suited to estuarine conditions. However, selection of habitats with optimal conditions for growth will maximise productivity. Moreover, as nutrient uptake appears to be independent of growth under challenging conditions, low productivity may not result in reduced bioremediation capability. These characteristics make G. transtasmanica an ideal species for in-situ bioremediation in New Zealand estuaries. Additionally, G. transtasmanica biomass is suitable for use in a range of bioproducts. Therefore, there is potential for a bioremediation based circular economy approach with the use of harvested G. transtasmanica biomass following bioremediation. In-situ trials are required to verifying the findings reported here and enable optimisation of both bioremediation efficiency and biomass productivity.

text: Gracilaria transtasmanica: a potential novel target species for the bioremediation of nutrient enriched estuaries Estuaries are increasingly becoming eutrophic due to anthropogenically induced nutrient enrichment. Presently, 24% of global anthropogenically derived nutrients released into coastal catchments are delivered directly into coastal waters such as estuaries. Thirty five percent of New Zealand’s estuaries are susceptible to eutrophication and some are already severely degraded. In-situ macroalgal bioremediation – the cultivation of live macroalgae directly in nutrient-enriched waters for the primary purpose of nutrient assimilation – could help prevent and reduce estuarine eutrophication.

The indigenous red macroalga Gracilaria transtasmanica has been identified as a potential target species for bioremediation in New Zealand estuaries. Samples of G. transtasmanica were collected from estuaries in the Bay of Plenty region of New Zealand, and were isolated, formally identified and scaled up into stock cultures. Controlled experiments were then used to assess the bioremediation potential of this species in winter and summer conditions under ambient and extreme nutrient and sediment levels. Biomass productivity, photosynthetic health, and N removal were assessed to quantify performance. Biomass productivity and total N removed were 45 and 50% higher respectively in summer compared to winter. Biomass productivity ranged from 0.4 – 4.3 g DW m² in summer and 0.6 – 1.8 g DW m² in winter, and total N removed ranged from 6.0 – 30.7 mg N in summer and 6.1 – 9.1 mg N in winter. In contrast, standardised N removal rates were higher in winter (37.8 mg g DW biomass growth⁻¹ ± 0.6 S.E.) compared to summer (22.3 mg g DW biomass growth⁻¹ ± 1.2 S.E.), suggesting that the biomass was storing N and therefore that N uptake was independent of productivity under sub-optimal growing conditions. Productivity was significantly affected by sediment treatment, however this effect differed seasonally, with higher productivity in the high

sediment treatments in summer, and lower productivity in the high sediment treatments in winter. These results demonstrate that G. transtasmanica can assimilate nutrients under a range of environmental conditions that are representative of both local background and high levels of suspended sediment and nutrient concentrations, and therefore is a viable target species for the bioremediation of nutrient enriched estuaries.In addition to nutrient uptake and productivity, target species for in-situ estuarine bioremediation need to maintain productivity under a range of challenging abiotic conditions. In chapter three of this thesis, a series of independent experiments assessed the tolerance of G. transtasmanica to ambient and extreme levels of salinity, exposure, and light limitation that are likely to be experienced in an estuary. Photosynthetic functioning and growth were used to quantify the tolerance range of G. transtasmanica in each experiment. Specific Growth Rate (SGR) was significantly affected by salinity, exposure, and light limitation. Gracilaria transtasmanica was able to grow in salinities ranging from 5 to 35 ppt, but growth rates decreased with decreasing salinity. Exposure periods of up to 9 hours were tolerated, but growth rates were decreased as exposure period increased. Gracilaria transtasmanica was able to maintain growth with a loss of up to 75% of ambient light and was also able to tolerate short periods of no light. Measurements of optimal quantum yields showed photosynthetic function was unaffected by salinity, exposure, or light limitation. 

These results demonstrate the high tolerance and adaptability of G. transtasmanica to a broad range of challenging abiotic estuarine conditions. In combination, these findings demonstrate that Gracilaria transtasmanica is well suited to estuarine conditions. However, selection of habitats with optimal conditions for growth will maximise productivity. Moreover, as nutrient uptake appears to be independent of growth under challenging conditions, low productivity may not result in reduced bioremediation capability. These characteristics make G. transtasmanica an ideal species for in-situ bioremediation in New Zealand estuaries. Additionally, G. transtasmanica biomass is suitable for use in a range of bioproducts. Therefore, there is potential for a bioremediation based circular economy approach with the use of harvested G. transtasmanica biomass following bioremediation. In-situ trials are required to verifying the findings reported here and enable optimisation of both bioremediation efficiency and biomass productivity.

year: 2022

title: Sediment dynamics surrounding a flood tidal delta adjacent to reclamation and a dredged turning basin

authors: Longdill, Peter C.

subjects: tidal inlet

abstract: Field measurements of tidal current velocities are used to infer sediment transport characteristics in the lower section of a large, tidally dominated estuarine system at Whangarei Harbour, New Zealand. Recent (2002) developments at the harbour entrance included a 32.6 ha intertidal reclamation and a 31.8 ha dredged turning basin. Residual distance vectors indicate that the postdevelopment, large-scale pattern of sediment transport dynamics remains consistent. Minor, localised modification of transport potentials has been observed immediately adjacent to the developments, however. These modifications include a slight realignment of current flows near the reclamation wall and some leakage from a previously identified transport loop near the dredged basin. The potential for scour is identified along the eastern margin of the dredged basin, which could act to remove material moving downslope into the basin from its western edge. These data are consistent with numerical model results that predicted minimal consequences resulting from the developments. Lower harbour sediment dynamics are consistent with established patterns for tide-dominated inlets, with separation of the channel into areas of ebb and flood dominance, and typical transport patterns over the flood tidal delta. Broad-scale inlet geomorphology has been maintained, which is consistent with other dredged tidedominated inlets.

text: Sediment dynamics surrounding a flood tidal delta adjacent to reclamation and a dredged turning basin Field measurements of tidal current velocities are used to infer sediment transport characteristics in the lower section of a large, tidally dominated estuarine system at Whangarei Harbour, New Zealand. Recent (2002) developments at the harbour entrance included a 32.6 ha intertidal reclamation and a 31.8 ha dredged turning basin. Residual distance vectors indicate that the postdevelopment, large-scale pattern of sediment transport dynamics remains consistent. Minor, localised modification of transport potentials has been observed immediately adjacent to the developments, however. These modifications include a slight realignment of current flows near the reclamation wall and some leakage from a previously identified transport loop near the dredged basin. The potential for scour is identified along the eastern margin of the dredged basin, which could act to remove material moving downslope into the basin from its western edge. These data are consistent with numerical model results that predicted minimal consequences resulting from the developments. Lower harbour sediment dynamics are consistent with established patterns for tide-dominated inlets, with separation of the channel into areas of ebb and flood dominance, and typical transport patterns over the flood tidal delta. Broad-scale inlet geomorphology has been maintained, which is consistent with other dredged tidedominated inlets.

year: 2007

title: The Environmental Justice Implications of the Planning Policy and Practice of Flood Risk Management in New Zealand

authors: Martynoga, Charlotte

subjects: environmental justce

abstract: Following an international trend, the flood defence approach historically applied in New Zealand has been superseded by a shift to flood risk management, an approach that aligns with the notion of ‘living with risk’ and devolves responsibility to risk-takers at the local level. Citizens are required to assume responsibility for assessing and minimising their own exposure, increasing their resilience and adapting to periodic flooding events. Inevitably, specific communities respond differently to flooding as their capabilities to understand, identify and manage flood risk varies. Environmental justice is the framework of inquiry within which issues of power, representation and participation in planning for flood risk management are examined to consider the injustices that are experienced by communities ‘living with risk’. 

Quantitative and qualitative methods are used to investigate the extent planning is complicit in delivering flood risk management processes that can create environmentally unjust outcomes. Flood hazard maps overlaid with contextual demographic data identify who is living in at risk spaces in three case-study communities. Primary data was collected through semi-structured interviews with local government representatives and iwi, and a questionnaire to local residents was followed by interviews. 

The analysis demonstrates how the environmental justice components of distributive justice, procedural justice, justice as recognition and a capabilities approach to justice are tied together in the political and social processes of managing floods. Procedural justice is based on participatory parity so ensuring all members of the affected community are treated fairly in the deliberative and discursive decision-making is essential. Evidence revealed a community’s limited access to extensive flood risk information, unequal power sharing in decision-making and community participation, and restricted ability for disadvantaged groups to access legal processes. Distributive justice demands the use of multi-criteria analysis, rather than cost-benefit analysis, in prioritising and directing flood risk management to vulnerable communities. Using direct benefit rating to fund flood mitigation works heightens existing inequalities within communities and demands consideration of social difference in flood risk vulnerabilities. To ensure justice as recognition, local and indigenous knowledge needs to be valued and included in decision-making processes. Whilst working party arrangements are not inclusive they empower communities to be actively involved, promote trust and ownership of their local place and flood risk project. Recognition of identities and cultural practices is crucial for self-determination and minimises the marginalisation of voices. Planners need to examine social aspects of how people perceive, adapt and cope with flood risk, alongside place-based vulnerability. Policy, in embracing a capabilities approach to justice, would focus on the functionings people actually achieve rather than the opportunities. This calls for removing aggregations to look at the capabilities of individuals and communities to manage and respond to their flood risk. Judgements on planning initiatives need to be based on whether distributional outcomes enhance the capabilities of the relatively disadvantaged, thereby improving the resilience capacity of a community to manage flood risk. 

This study bridges a research gap in drawing together flood risk management, planning and environmental justice; advancing understanding of the environmental injustices within flood risk management in New Zealand.

text: The Environmental Justice Implications of the Planning Policy and Practice of Flood Risk Management in New Zealand Following an international trend, the flood defence approach historically applied in New Zealand has been superseded by a shift to flood risk management, an approach that aligns with the notion of ‘living with risk’ and devolves responsibility to risk-takers at the local level. Citizens are required to assume responsibility for assessing and minimising their own exposure, increasing their resilience and adapting to periodic flooding events. Inevitably, specific communities respond differently to flooding as their capabilities to understand, identify and manage flood risk varies. Environmental justice is the framework of inquiry within which issues of power, representation and participation in planning for flood risk management are examined to consider the injustices that are experienced by communities ‘living with risk’. 

Quantitative and qualitative methods are used to investigate the extent planning is complicit in delivering flood risk management processes that can create environmentally unjust outcomes. Flood hazard maps overlaid with contextual demographic data identify who is living in at risk spaces in three case-study communities. Primary data was collected through semi-structured interviews with local government representatives and iwi, and a questionnaire to local residents was followed by interviews. 

The analysis demonstrates how the environmental justice components of distributive justice, procedural justice, justice as recognition and a capabilities approach to justice are tied together in the political and social processes of managing floods. Procedural justice is based on participatory parity so ensuring all members of the affected community are treated fairly in the deliberative and discursive decision-making is essential. Evidence revealed a community’s limited access to extensive flood risk information, unequal power sharing in decision-making and community participation, and restricted ability for disadvantaged groups to access legal processes. Distributive justice demands the use of multi-criteria analysis, rather than cost-benefit analysis, in prioritising and directing flood risk management to vulnerable communities. Using direct benefit rating to fund flood mitigation works heightens existing inequalities within communities and demands consideration of social difference in flood risk vulnerabilities. To ensure justice as recognition, local and indigenous knowledge needs to be valued and included in decision-making processes. Whilst working party arrangements are not inclusive they empower communities to be actively involved, promote trust and ownership of their local place and flood risk project. Recognition of identities and cultural practices is crucial for self-determination and minimises the marginalisation of voices. Planners need to examine social aspects of how people perceive, adapt and cope with flood risk, alongside place-based vulnerability. Policy, in embracing a capabilities approach to justice, would focus on the functionings people actually achieve rather than the opportunities. This calls for removing aggregations to look at the capabilities of individuals and communities to manage and respond to their flood risk. Judgements on planning initiatives need to be based on whether distributional outcomes enhance the capabilities of the relatively disadvantaged, thereby improving the resilience capacity of a community to manage flood risk. 

This study bridges a research gap in drawing together flood risk management, planning and environmental justice; advancing understanding of the environmental injustices within flood risk management in New Zealand.

year: 2018