title: Microplastics in freshwaters: Comparing effects of particle properties and an invertebrate consumer on microbial communities and ecosystem functions

authors: Kong, ZH

subjects: Chironomid larvae

abstract: The effects of microplastic (MP) accumulation in freshwaters on organisms and ecosystem functions are poorly understood, as are the roles of MP particle properties in regulating these effects. In freshwater microcosms, we quantified variation in microbial communities and ecosystem functions and compared effects of MP concentration (0, 1000, 50000 particles/kgsediment), shape (sphere, fragment, fibre), and polymer (polyethylene, polyethylene terephthalate, polypropylene, polystyrene) with those of a model invertebrate consumer (Chironomus riparius). We detected multiple effects of specific MP properties, especially associated with MP fragments and fibres, and the polymer polypropylene. These effects included increases in microbial abundance, consumer biomass and ecosystem respiration, as well as decreases in microbial enzyme activity and water chlorophyll-a. MP presence was also associated with increased relative abundance of microbial taxa reported to degrade plastics. However, consumer presence mostly had stronger effects (effect sizes ranging from ± 11 −313 %) than MP exposure (effect sizes ranging from ± 1–89 %) on microbial communities and ecosystem functions. Furthermore, several MP effects were only detected when chironomid consumers were absent. Overall, our findings suggest that MP effects on microbes and ecosystem functions are often relatively small and variable, depending on particle properties and consumer presence. Nevertheless, the number of MP effects detected highlights the need for further investigations of interactions between MPs and other environmental drivers, to more thoroughly assess the risks of MP pollution for freshwater ecosystems.

text: Microplastics in freshwaters: Comparing effects of particle properties and an invertebrate consumer on microbial communities and ecosystem functions The effects of microplastic (MP) accumulation in freshwaters on organisms and ecosystem functions are poorly understood, as are the roles of MP particle properties in regulating these effects. In freshwater microcosms, we quantified variation in microbial communities and ecosystem functions and compared effects of MP concentration (0, 1000, 50000 particles/kgsediment), shape (sphere, fragment, fibre), and polymer (polyethylene, polyethylene terephthalate, polypropylene, polystyrene) with those of a model invertebrate consumer (Chironomus riparius). We detected multiple effects of specific MP properties, especially associated with MP fragments and fibres, and the polymer polypropylene. These effects included increases in microbial abundance, consumer biomass and ecosystem respiration, as well as decreases in microbial enzyme activity and water chlorophyll-a. MP presence was also associated with increased relative abundance of microbial taxa reported to degrade plastics. However, consumer presence mostly had stronger effects (effect sizes ranging from ± 11 −313 %) than MP exposure (effect sizes ranging from ± 1–89 %) on microbial communities and ecosystem functions. Furthermore, several MP effects were only detected when chironomid consumers were absent. Overall, our findings suggest that MP effects on microbes and ecosystem functions are often relatively small and variable, depending on particle properties and consumer presence. Nevertheless, the number of MP effects detected highlights the need for further investigations of interactions between MPs and other environmental drivers, to more thoroughly assess the risks of MP pollution for freshwater ecosystems.

year: 2025

title: Nowcasting and predicting data revisions using panel survey data

authors: Matheson, Troy D.

subjects: nowcasting

abstract: The qualitative responses that firms give to business survey questions regarding changes in their own output provide a real-time signal of official output changes. The most commonly used method to produce an aggregate quantitative indicator from business survey responses - the net balance or diffusion index - has changed little in 40 years. This paper investigates whether an improved real-time signal of official output data changes can be derived from a recently advanced method on the aggregation of survey data from panel responses. We find, in a New Zealand application, that exploiting the panel dimension to qualitative survey data gives a better in-sample signal about official data than traditional methods. Out-of-sample, it is less clear that it matters how survey data are quantified, with simpler and more parsimonious methods hard to improve. It is clear, nevertheless, that survey data, exploited in some form, help to explain revisions to official data.

text: Nowcasting and predicting data revisions using panel survey data The qualitative responses that firms give to business survey questions regarding changes in their own output provide a real-time signal of official output changes. The most commonly used method to produce an aggregate quantitative indicator from business survey responses - the net balance or diffusion index - has changed little in 40 years. This paper investigates whether an improved real-time signal of official output data changes can be derived from a recently advanced method on the aggregation of survey data from panel responses. We find, in a New Zealand application, that exploiting the panel dimension to qualitative survey data gives a better in-sample signal about official data than traditional methods. Out-of-sample, it is less clear that it matters how survey data are quantified, with simpler and more parsimonious methods hard to improve. It is clear, nevertheless, that survey data, exploited in some form, help to explain revisions to official data.

year: 2009

title: Pātangaroa: Co-developing management strategies for a starfish outbreak in Ōhiwa Harbour

authors: Ranapia, Megan

subjects: marine management

abstract: The management of marine environments often prioritises scientific information to address complex marine social-ecological issues. However, there is a wealth of learning to be gained from Indigenous people who have generated place-based intergenerational understandings and cultural ethics and practices. Consequently, Indigenous knowledge alongside science can offer better insights, holistic understanding, sustainable management strategies and greater sources of evidence. This research is located in Aotearoa New Zealand and engages in mātauranga Māori (Māori knowledge) alongside marine ecology as an appropriate method for contemporary marine research and management. The thesis study focused on Ōhiwa Harbour, aiming to co-develop a starfish management action plan (SMAP) with local iwi (tribe) Ngāti Awa and other affiliated iwi, district councils and regional council to address the overabundant starfish (species: Coscinasterias muricata and Patiriella regularis). By engaging in transdisciplinary research and collaborative decision-making, this study sought to bridge the gap between Indigenous knowledge and mainstream science, offering lessons for inclusive marine management practices.

To achieve this, I developed and prescribed a co-developed framework actively promoting a mixed-methods approach, inclusive of kaupapa Māori research methodologies, tikanga, participatory design, applied mātauranga ā iwi, quantitative marine scientific field methods and experimental study design. Through the collaborative process, I identified areas of appropriate research aims and methods. This included co-developing a novel starfish trapping methodology sensitive to local ecology and cultural values and an experimental starfish removal study to assist decision-makers in implementing an efficient and effective starfish removal regime as an approach to management.

Results from the field studies showed the efficacy of starfish traps is dependent on environmental conditions, physical characteristics and soaking time (the length of time the trap is left in the water). A soaking time of 48 h maintained the highest starfish catch per unit effort (CPUE) while minimising time to re-bait and reset traps. Observations also indicated an open trap design had less bycatch than a semi-enclosed box trap and could withstand the tidal currents for a longer period. The findings found that bait type did not impact on CPUE. In the starfish removal study, the combined effort of diver removals and trapping produced higher daily catch rates than the single treatments (i.e., diver removals only or trapping only), therefore was themost efficient removal method. The empirical information gathered from the field studies was then used to inform the SMAP and was accepted unanimously at the highest local/regional co-management level. Furthermore, through the findings I identified future research opportunities that would further close gaps in our knowledge around the best management approaches for a starfish outbreak. These included investigation into the predation impacts of P. regularis on mussel recruitment, identification of alternative restoration sites less susceptible to starfish predation pressures and investigation of potential drivers of the starfish outbreak.

Overall, the acceptance of the SMAP by local iwi/hapū and government authorities underscores the success of the collaborative approach. The collaborative process not only addresses the immediate concerns of starfish infestation but contributed to the broader goal of supporting kaitiakitanga (active guardianship) responsibilities and promoting Indigenous perspectives in marine management. This thesis demonstrates and recommends a new approach to starfish management in coastal marine areas using both marine science and mātauranga Māori understandings, practices and ethics, furthermore, it demonstrates the commitment to the inclusion of multiple knowledge systems and involvement of communities.

text: Pātangaroa: Co-developing management strategies for a starfish outbreak in Ōhiwa Harbour The management of marine environments often prioritises scientific information to address complex marine social-ecological issues. However, there is a wealth of learning to be gained from Indigenous people who have generated place-based intergenerational understandings and cultural ethics and practices. Consequently, Indigenous knowledge alongside science can offer better insights, holistic understanding, sustainable management strategies and greater sources of evidence. This research is located in Aotearoa New Zealand and engages in mātauranga Māori (Māori knowledge) alongside marine ecology as an appropriate method for contemporary marine research and management. The thesis study focused on Ōhiwa Harbour, aiming to co-develop a starfish management action plan (SMAP) with local iwi (tribe) Ngāti Awa and other affiliated iwi, district councils and regional council to address the overabundant starfish (species: Coscinasterias muricata and Patiriella regularis). By engaging in transdisciplinary research and collaborative decision-making, this study sought to bridge the gap between Indigenous knowledge and mainstream science, offering lessons for inclusive marine management practices.

To achieve this, I developed and prescribed a co-developed framework actively promoting a mixed-methods approach, inclusive of kaupapa Māori research methodologies, tikanga, participatory design, applied mātauranga ā iwi, quantitative marine scientific field methods and experimental study design. Through the collaborative process, I identified areas of appropriate research aims and methods. This included co-developing a novel starfish trapping methodology sensitive to local ecology and cultural values and an experimental starfish removal study to assist decision-makers in implementing an efficient and effective starfish removal regime as an approach to management.

Results from the field studies showed the efficacy of starfish traps is dependent on environmental conditions, physical characteristics and soaking time (the length of time the trap is left in the water). A soaking time of 48 h maintained the highest starfish catch per unit effort (CPUE) while minimising time to re-bait and reset traps. Observations also indicated an open trap design had less bycatch than a semi-enclosed box trap and could withstand the tidal currents for a longer period. The findings found that bait type did not impact on CPUE. In the starfish removal study, the combined effort of diver removals and trapping produced higher daily catch rates than the single treatments (i.e., diver removals only or trapping only), therefore was themost efficient removal method. The empirical information gathered from the field studies was then used to inform the SMAP and was accepted unanimously at the highest local/regional co-management level. Furthermore, through the findings I identified future research opportunities that would further close gaps in our knowledge around the best management approaches for a starfish outbreak. These included investigation into the predation impacts of P. regularis on mussel recruitment, identification of alternative restoration sites less susceptible to starfish predation pressures and investigation of potential drivers of the starfish outbreak.

Overall, the acceptance of the SMAP by local iwi/hapū and government authorities underscores the success of the collaborative approach. The collaborative process not only addresses the immediate concerns of starfish infestation but contributed to the broader goal of supporting kaitiakitanga (active guardianship) responsibilities and promoting Indigenous perspectives in marine management. This thesis demonstrates and recommends a new approach to starfish management in coastal marine areas using both marine science and mātauranga Māori understandings, practices and ethics, furthermore, it demonstrates the commitment to the inclusion of multiple knowledge systems and involvement of communities.

year: 2025-05