title: Small-scale spatial patterns of Austrovenus stutchburyi in natural and translocated beds

authors: Ross, Frank

subjects: Ecosystem functioning

abstract: Ecosystems are patterned and patchy as a result of spatial and temporal variation in the abundance and distribution of essential resources, as well as due to geological and ecological processes. Large-scale patterns are usually formed by abiotic stressors while small-scale patterns are a result of biotic factors such as inter- and intra-specific interactions. Many suspension feeding bivalves have been reported to form both small and large-scale spatial patterns in soft-sediment environments, in a response to boost resilience from environmental stressors and increase facilitation. However, small-scale spatial patterns of infaunal suspension feeding bivalves are currently not as well studiedfor, despite playing important roles in ecosystem functioning e.g. eutrophication control, resuspend buried nutrients and modify habitats through increased bed roughness. This thesis set out to recognize small-scale spatial patterns of Austrovenus stutchburyi and whether patterns differed with density or environmental properties in Tauranga Harbour. A field survey was used to distinguish small-scale spatial patterns of 
Austrovenus stutchburyi in nine established Austrovenus stutchburyi beds. At each site 
a 4 m² plot was established in a ‘low’, ‘medium’ and ‘high’ density section of Austrovenus stutchburyi aggregates, with core samples taken at 0.5 m intervals within the plots. Austrovenus stutchburyi were then transplanted at low, medium and high densities in 4 m² plots into an area of low ambient densities to observe any spatial pattern formation and environmental effects with density. Austrovenus stutchburyi did not exhibit spatial patterns no different from random in natural beds and was not dependent on density or environmental variables. This was indicated by most of the plots accepting the null hypothesis of Moran’s I which indicates a random distribution. Following the same sampling design as the field survey a translocation experiment was performed to distinguish any small-scale spatial patterns of Austrovenus stutchburyi in a low ambient density environment. Transplanted Austrovenus stutchburyi beds exhibited clustering in high density treatments, indicated by a positive Moran’s I value in all three high density plots (0.335 – 0.420). Both low and medium plots exhibited random patterns, accepting the null hypothesis of Moran’s I. Transplanted Austrovenus stutchburyi beds significantly improved chlorophyll a content with increasing density treatments as chlorophyll a increased by almost a factor of two between ambient and high plots from 11.3 µg g⁻¹ dw to 20.4 µg g⁻¹ dw. However, only a small increase in organic matter content was observed and no modifications were seen towards sediment grain size properties. The results from this study can enrich the knowledge of the currently understudied small-scale patterns of infaunal suspension feeding bivalves including acting as a baseline for future hypotheses and sampling schemes. There is also potential for the high-density translocated plots to act as nursery grounds for reseeded juvenile Austrovenus stutchburyi due to the modified environment becoming nutrient-rich further improving conservation and restoration of estuarine habitats.

text: Small-scale spatial patterns of Austrovenus stutchburyi in natural and translocated beds Ecosystems are patterned and patchy as a result of spatial and temporal variation in the abundance and distribution of essential resources, as well as due to geological and ecological processes. Large-scale patterns are usually formed by abiotic stressors while small-scale patterns are a result of biotic factors such as inter- and intra-specific interactions. Many suspension feeding bivalves have been reported to form both small and large-scale spatial patterns in soft-sediment environments, in a response to boost resilience from environmental stressors and increase facilitation. However, small-scale spatial patterns of infaunal suspension feeding bivalves are currently not as well studiedfor, despite playing important roles in ecosystem functioning e.g. eutrophication control, resuspend buried nutrients and modify habitats through increased bed roughness. This thesis set out to recognize small-scale spatial patterns of Austrovenus stutchburyi and whether patterns differed with density or environmental properties in Tauranga Harbour. A field survey was used to distinguish small-scale spatial patterns of 
Austrovenus stutchburyi in nine established Austrovenus stutchburyi beds. At each site 
a 4 m² plot was established in a ‘low’, ‘medium’ and ‘high’ density section of Austrovenus stutchburyi aggregates, with core samples taken at 0.5 m intervals within the plots. Austrovenus stutchburyi were then transplanted at low, medium and high densities in 4 m² plots into an area of low ambient densities to observe any spatial pattern formation and environmental effects with density. Austrovenus stutchburyi did not exhibit spatial patterns no different from random in natural beds and was not dependent on density or environmental variables. This was indicated by most of the plots accepting the null hypothesis of Moran’s I which indicates a random distribution. Following the same sampling design as the field survey a translocation experiment was performed to distinguish any small-scale spatial patterns of Austrovenus stutchburyi in a low ambient density environment. Transplanted Austrovenus stutchburyi beds exhibited clustering in high density treatments, indicated by a positive Moran’s I value in all three high density plots (0.335 – 0.420). Both low and medium plots exhibited random patterns, accepting the null hypothesis of Moran’s I. Transplanted Austrovenus stutchburyi beds significantly improved chlorophyll a content with increasing density treatments as chlorophyll a increased by almost a factor of two between ambient and high plots from 11.3 µg g⁻¹ dw to 20.4 µg g⁻¹ dw. However, only a small increase in organic matter content was observed and no modifications were seen towards sediment grain size properties. The results from this study can enrich the knowledge of the currently understudied small-scale patterns of infaunal suspension feeding bivalves including acting as a baseline for future hypotheses and sampling schemes. There is also potential for the high-density translocated plots to act as nursery grounds for reseeded juvenile Austrovenus stutchburyi due to the modified environment becoming nutrient-rich further improving conservation and restoration of estuarine habitats.

year: 2020

title: Chaos and irregularity in karst percolation

authors: Mariethoz, Gregoire

subjects: Australia

abstract: This paper focuses on analyzing chaos in cave percolation water drip rates, which has implications for flow routing in fractured media and on the use of speleothems for paleoclimate reconstructions. It has been shown that the physics of dripping faucets involve a set of non-linear equations leading to chaotic drip rate, meaning that, for a given drip rate, the interval between individual drops can vary greatly. It can be expected that drip waters supplying stalagmites show similar properties, and consequently the dependency between water flux and stalagmite growth rate or geochemistry could be more complicated than usually assumed. We used high-frequency monitoring of two contrasting drips in a cave in Australia, and identified chaos in cave drip rate. Our findings also indicate that the occurrence of chaos can give insights into flow routing in fractured media.

text: Chaos and irregularity in karst percolation This paper focuses on analyzing chaos in cave percolation water drip rates, which has implications for flow routing in fractured media and on the use of speleothems for paleoclimate reconstructions. It has been shown that the physics of dripping faucets involve a set of non-linear equations leading to chaotic drip rate, meaning that, for a given drip rate, the interval between individual drops can vary greatly. It can be expected that drip waters supplying stalagmites show similar properties, and consequently the dependency between water flux and stalagmite growth rate or geochemistry could be more complicated than usually assumed. We used high-frequency monitoring of two contrasting drips in a cave in Australia, and identified chaos in cave drip rate. Our findings also indicate that the occurrence of chaos can give insights into flow routing in fractured media.

year: 2012

title: Iwi case study report- Tarawera river: Tuwharetoa ki Kawerau, Te Arawa and Ngati Awa

authors: Dodd, Materoa

subjects: Iwi land rights

abstract: There is a deep sense of injustice and creeping despair that the cultural life of the Tarawera River has been destroyed. Cultural lore has been reduced to a perspective of the dominant cultures’ rule of law. The plea for the cultural voice of the Tarawera River to be heard echoes throughout this research, yet the silence of the response is deafening. This research informs on the cultural story of the Tarawera River, it examines the ways in which the relationship between Te Arawa, Tūwharetoa Ki Kawerau and Ngāti Awa and the Tarawera River changed since the discharge of effluent from pulp and paper mills into the river began nearly half a century ago. The research reported on here involves action research approached and informed by Māori epistemologies and what has come to be known as ‘kaupapa Māori research’, an approach that privileges indigenous values, attitudes and practices.

text: Iwi case study report- Tarawera river: Tuwharetoa ki Kawerau, Te Arawa and Ngati Awa There is a deep sense of injustice and creeping despair that the cultural life of the Tarawera River has been destroyed. Cultural lore has been reduced to a perspective of the dominant cultures’ rule of law. The plea for the cultural voice of the Tarawera River to be heard echoes throughout this research, yet the silence of the response is deafening. This research informs on the cultural story of the Tarawera River, it examines the ways in which the relationship between Te Arawa, Tūwharetoa Ki Kawerau and Ngāti Awa and the Tarawera River changed since the discharge of effluent from pulp and paper mills into the river began nearly half a century ago. The research reported on here involves action research approached and informed by Māori epistemologies and what has come to be known as ‘kaupapa Māori research’, an approach that privileges indigenous values, attitudes and practices.

year: 2002-02