title: He Piko, He Repo: Environmental DNA as a biomonitoring tool for wetland restoration

authors: Bird, Starsha

subjects: colonisation

abstract: Wetlands are biodiversity hotspots, harbouring distinctive species while providing numerous ecosystem services. Unfortunately, throughout human civilisation, they have been systematically degraded, resulting in a dramatic global loss in wetland extent, the establishment of invasive species and the extinction of many natives and, in Aotearoa New Zealand, impediment of the special connection Māori share with their repo (wetlands). Monitoring wetland biodiversity to take appropriate restorative action and minimise further degradation is imperative, particularly in the face of climate change. Environmental DNA (eDNA; genetic material released by organisms into the environment) is an increasingly popular non-invasive biomonitoring method that provides information about the presence or potential absence of species inhabiting a given ecosystem, but has yet to be optimised for wetland environments. My thesis aimed to address the consequences of colonisation on the relationship between Māori and their wetlands, and to explore the value eDNA holds for wetland biomonitoring. The first analysis (Chapter 2) delved into the past (post-European settlement; 1840s), the present (2023), and the future (2073) of Opuatia Wetland (Waikato, Aotearoa New Zealand) through a series of interviews with three individuals who whakapapa to (are connected with) Opuatia Wetland and its surroundings. I found that Opuatia Wetland once flourished with native biodiversity, and kai (food) was readily available. However, land confiscation by European settlers marked the downfall of this once productive and connected catchment such that it is presently in a fairly degraded state, dominated by exotic species, with Māori feeling disconnected from their whenua (land). Considering the future, the interviewees envisioned a revived abundance of native species and desire for restoration efforts to be facilitated by both mātauranga Māori (Māori knowledge) and science. The second analysis (Chapter 3) examined a publicly available eDNA database to retrieve data from 26 wetland sites across Aotearoa New Zealand to understand taxonomic diversity patterns. Here, I showed that DNA sequence composition varied across the motu (country), illustrating that varying environmental conditions among wetland types influences biodiversity. Notably, most sites were dominated by >50% exotic species. These findings highlight the value of publicly shared data for generating new insights, and the need for resource allocations to tackle the persistence of exotic species in wetland ecosystems. The third analysis (Chapter 4) focused on analysing biodiversity dynamics at a single wetland and tested various eDNA sampling techniques. I sampled four spatially distant sites across Opuatia Wetland at three time points during an austral spring and simultaneously obtained data from conventional taxonomic surveys, tested three different filter sizes, and assessed DNA degradation rates using foreign DNA. I found significant differences in biodiversity across time and space, and when using different eDNA collection filters. Foreign DNA persisted for up to one week post-release within a 10 m radius, and combining conventional and eDNA methods provided a more comprehensive overview of biodiversity patterns. These findings collectively showcased key changes in biodiversity, even over short spatial and temporal scales, and identified parameters to consider for wetland biodiversity monitoring and associated data interpretation. It is only a matter of time until the impacts of climate change and invasive species take firmer hold of Aotearoa New Zealand's distinctive and fragile environment. Undoubtedly, eDNA can be part of the solution to mitigate these challenges, owing to its versatility across ecosystem types, capacity to extend to various substrates, and accessibility for researchers and citizen scientists alike. As eDNA methods continue to improve and become integrated into ongoing biomonitoring schemes, building equitable and empowering relationships between Māori and researchers/government bodies will best ensure that Aotearoa New Zealand repo and other environments are maintained and conserved for future generations.

text: He Piko, He Repo: Environmental DNA as a biomonitoring tool for wetland restoration Wetlands are biodiversity hotspots, harbouring distinctive species while providing numerous ecosystem services. Unfortunately, throughout human civilisation, they have been systematically degraded, resulting in a dramatic global loss in wetland extent, the establishment of invasive species and the extinction of many natives and, in Aotearoa New Zealand, impediment of the special connection Māori share with their repo (wetlands). Monitoring wetland biodiversity to take appropriate restorative action and minimise further degradation is imperative, particularly in the face of climate change. Environmental DNA (eDNA; genetic material released by organisms into the environment) is an increasingly popular non-invasive biomonitoring method that provides information about the presence or potential absence of species inhabiting a given ecosystem, but has yet to be optimised for wetland environments. My thesis aimed to address the consequences of colonisation on the relationship between Māori and their wetlands, and to explore the value eDNA holds for wetland biomonitoring. The first analysis (Chapter 2) delved into the past (post-European settlement; 1840s), the present (2023), and the future (2073) of Opuatia Wetland (Waikato, Aotearoa New Zealand) through a series of interviews with three individuals who whakapapa to (are connected with) Opuatia Wetland and its surroundings. I found that Opuatia Wetland once flourished with native biodiversity, and kai (food) was readily available. However, land confiscation by European settlers marked the downfall of this once productive and connected catchment such that it is presently in a fairly degraded state, dominated by exotic species, with Māori feeling disconnected from their whenua (land). Considering the future, the interviewees envisioned a revived abundance of native species and desire for restoration efforts to be facilitated by both mātauranga Māori (Māori knowledge) and science. The second analysis (Chapter 3) examined a publicly available eDNA database to retrieve data from 26 wetland sites across Aotearoa New Zealand to understand taxonomic diversity patterns. Here, I showed that DNA sequence composition varied across the motu (country), illustrating that varying environmental conditions among wetland types influences biodiversity. Notably, most sites were dominated by >50% exotic species. These findings highlight the value of publicly shared data for generating new insights, and the need for resource allocations to tackle the persistence of exotic species in wetland ecosystems. The third analysis (Chapter 4) focused on analysing biodiversity dynamics at a single wetland and tested various eDNA sampling techniques. I sampled four spatially distant sites across Opuatia Wetland at three time points during an austral spring and simultaneously obtained data from conventional taxonomic surveys, tested three different filter sizes, and assessed DNA degradation rates using foreign DNA. I found significant differences in biodiversity across time and space, and when using different eDNA collection filters. Foreign DNA persisted for up to one week post-release within a 10 m radius, and combining conventional and eDNA methods provided a more comprehensive overview of biodiversity patterns. These findings collectively showcased key changes in biodiversity, even over short spatial and temporal scales, and identified parameters to consider for wetland biodiversity monitoring and associated data interpretation. It is only a matter of time until the impacts of climate change and invasive species take firmer hold of Aotearoa New Zealand's distinctive and fragile environment. Undoubtedly, eDNA can be part of the solution to mitigate these challenges, owing to its versatility across ecosystem types, capacity to extend to various substrates, and accessibility for researchers and citizen scientists alike. As eDNA methods continue to improve and become integrated into ongoing biomonitoring schemes, building equitable and empowering relationships between Māori and researchers/government bodies will best ensure that Aotearoa New Zealand repo and other environments are maintained and conserved for future generations.

year: 2023

title: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013

authors: Hicks, Brendan J.

abstract: The aim of this survey was to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura). In the current study we present the findings from the seventh year of sampling (2013) in view of previous surveys using boat electrofishing in the Ohau Channel. 
We used the University of Waikato's 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 1,025 fish (20.3 kg) from 11 sites comprising 2,817 lineal m and 11,484 m² in area on 27 November 2013. Common bully were the most abundant fish species (57% of the catch) followed by common smelt (36% of the catch).
Goldfish had their highest biomasses in the lower channel, especially at site 10 near Lake Rotoiti (up to 7.25 g m⁻²). Catch per unit effort (CPUE) for common bullies exceeded smelt CPUE at all sites except site 1, reflecting their greater densities. CPUE for rainbow trout was variable between the sites, and greatest at site 3. 
The abundance of common bullies in 2013 reversed the apparent trend of reducing abundance since these surveys started in 2007. The cause of fluctuating bully abundance is not known, and was not accounted for by water clarity expressed as black disc distance (BDD) or water conductivity. Poor water clarity can reduce the efficiency of electrofishing, but BDD was greater in 2012 than in 2011 when common bully densities were lower. In 2013, the apparent decline in smelt abundance was also reversed, but the relatively inefficient sampling resulting from boat electrofishing for these two species should be considered. 
The increased goldfish biomass in 2011-2013 arose because of targeted fishing in the excavated side branch, which clearly offers good habitat for goldfish. Removal of goldfish in the previous years may have reduced the density in the excavated side channel (site 11) compared to previous years. In 2013, a shortfin eel was caught, following the first shortfin eel encountered in the Ohau Channel in 2012.

text: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013 The aim of this survey was to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura). In the current study we present the findings from the seventh year of sampling (2013) in view of previous surveys using boat electrofishing in the Ohau Channel. 
We used the University of Waikato's 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 1,025 fish (20.3 kg) from 11 sites comprising 2,817 lineal m and 11,484 m² in area on 27 November 2013. Common bully were the most abundant fish species (57% of the catch) followed by common smelt (36% of the catch).
Goldfish had their highest biomasses in the lower channel, especially at site 10 near Lake Rotoiti (up to 7.25 g m⁻²). Catch per unit effort (CPUE) for common bullies exceeded smelt CPUE at all sites except site 1, reflecting their greater densities. CPUE for rainbow trout was variable between the sites, and greatest at site 3. 
The abundance of common bullies in 2013 reversed the apparent trend of reducing abundance since these surveys started in 2007. The cause of fluctuating bully abundance is not known, and was not accounted for by water clarity expressed as black disc distance (BDD) or water conductivity. Poor water clarity can reduce the efficiency of electrofishing, but BDD was greater in 2012 than in 2011 when common bully densities were lower. In 2013, the apparent decline in smelt abundance was also reversed, but the relatively inefficient sampling resulting from boat electrofishing for these two species should be considered. 
The increased goldfish biomass in 2011-2013 arose because of targeted fishing in the excavated side branch, which clearly offers good habitat for goldfish. Removal of goldfish in the previous years may have reduced the density in the excavated side channel (site 11) compared to previous years. In 2013, a shortfin eel was caught, following the first shortfin eel encountered in the Ohau Channel in 2012.

year: 2014

title: High-resolution radiocarbon chronologies and synchronization of records

authors: Hajdas, Irka

abstract: It is now accepted that the precise dating of certain periods is complicated by extreme variability of atmospheric ¹⁴C content shown at times in the ¹⁴C calibration curve. This complication arises from variations in atmospheric ¹⁴C content and is known as wiggles in the calibration curve. Radiocarbon age ‘plateaus’, are caused by a decrease in the atmospheric ¹⁴C concentration and appear as a slowing down of the ¹⁴C clock such as occurred during the Younger Dryas (YD) chronozone. In effect, similar ¹⁴C ages apply across a range of up to 500 calendar years. The opposite is observed when atmospheric ¹⁴C levels increase so that the ¹⁴C clock appears to speed up. In such cases, which include the beginning of the YD and Pre-Boreal intervals, the true age of a sample, taking dating errors into account, may spread across a comparatively wide ¹⁴C age range

text: High-resolution radiocarbon chronologies and synchronization of records It is now accepted that the precise dating of certain periods is complicated by extreme variability of atmospheric ¹⁴C content shown at times in the ¹⁴C calibration curve. This complication arises from variations in atmospheric ¹⁴C content and is known as wiggles in the calibration curve. Radiocarbon age ‘plateaus’, are caused by a decrease in the atmospheric ¹⁴C concentration and appear as a slowing down of the ¹⁴C clock such as occurred during the Younger Dryas (YD) chronozone. In effect, similar ¹⁴C ages apply across a range of up to 500 calendar years. The opposite is observed when atmospheric ¹⁴C levels increase so that the ¹⁴C clock appears to speed up. In such cases, which include the beginning of the YD and Pre-Boreal intervals, the true age of a sample, taking dating errors into account, may spread across a comparatively wide ¹⁴C age range

year: 2006