title: The ecological consequences of stream sedimentation for freshwater macroinvertebrates in the Te Awanui/Tauranga Harbour catchment

authors: Lea, Brooklyn

subjects: freshwater ecology

abstract: Sedimentation is a significant stressor in streams and rivers globally. The natural sediment regime 
paradigm posits that human activities have greatly altered the natural transport of sediment in river 
networks and that land-uses leading to increased bank erosion and surface runoff have resulted in 
large quantities of fine sediment being deposited in streams and rivers. In New Zealand, land 
conversion from native forest to pastoral agriculture has dramatically increased riverine sediment 
loads, making deposited fine sediment (DFS) a major stressor that negatively impacts stream 
ecosystem health. Consequently, DFS is an important attribute managed under the National Policy 
Statement for Freshwater Management 2020. However, uncertainties remain in how best to 
monitor the effects of DFS, and what impacts different land-use types have on stream ecosystems 
in addition to the adverse influence of sedimentation.  
In my study, I surveyed 24 stream sites allocated evenly to three land-use types (native forest, 
pastoral agriculture, and horticulture, e.g. kiwifruit orchards) in the Tauranga Harbour basin. I 
measured habitat attributes, including DFS, and sampled stream macroinvertebrate communities 
at each site. Using macroinvertebrate data, I calculated and compared taxonomic and trait-based 
metrics as indicators of ecosystem health across land-use types. I used a variety of metrics, 
including the Macroinvertebrate Community Index (MCI) and its quantitative equivalent, the 
QMCI, the Average Score Per Metric (ASPM) index, and community-weighted mean trait 
abundances, including facets of functional diversity to assess impacts on stream health.  
I found that human land uses negatively influenced stream health, indicated by greatly reduced 
MCI, QMCI, and ASPM scores. Although DFS explained most of the negative influences on 
macroinvertebrate communities in pastoral and horticultural streams, there were differences 
between native forest and horticultural streams not accounted for by DFS that contributed to 
declines in ecosystem health. I also found that sediment-specific macroinvertebrate metrics 
(sediment ‘decreasers’) were the best indicators of DFS impacts on stream health. Contrary to my 
predictions, I did not find that functional diversity was strongly reduced by land use or DFS, 
although several key traits responded to these stressors. Notably, life history trait modalities 
involving the number of reproductive cycles per year and oviposition site responded strongly to 
DFS and land use, indicating potential mechanisms contributing towards the impacts of these 
stressors on macroinvertebrate communities.  
ii 
My study points to the need to continuously manage the deposition of fine sediment in streams to 
help mitigate the adverse effects of human land use. Future research should further explore the 
role that fine sediment and other stressors associated with human land uses play in the degradation 
of streams ecosystems in the Tauranga Harbour basin. Quantifying land use and land cover 
(LULC) attributes using geospatial tools will help further explore the relationship between 
catchment properties and macroinvertebrate responses. Additionally, issues regarding trait 
syndromes, trade-offs, and database inconsistencies must be addressed to better understand the 
mechanistic links between specific macroinvertebrate traits and fine sediment.

text: The ecological consequences of stream sedimentation for freshwater macroinvertebrates in the Te Awanui/Tauranga Harbour catchment Sedimentation is a significant stressor in streams and rivers globally. The natural sediment regime 
paradigm posits that human activities have greatly altered the natural transport of sediment in river 
networks and that land-uses leading to increased bank erosion and surface runoff have resulted in 
large quantities of fine sediment being deposited in streams and rivers. In New Zealand, land 
conversion from native forest to pastoral agriculture has dramatically increased riverine sediment 
loads, making deposited fine sediment (DFS) a major stressor that negatively impacts stream 
ecosystem health. Consequently, DFS is an important attribute managed under the National Policy 
Statement for Freshwater Management 2020. However, uncertainties remain in how best to 
monitor the effects of DFS, and what impacts different land-use types have on stream ecosystems 
in addition to the adverse influence of sedimentation.  
In my study, I surveyed 24 stream sites allocated evenly to three land-use types (native forest, 
pastoral agriculture, and horticulture, e.g. kiwifruit orchards) in the Tauranga Harbour basin. I 
measured habitat attributes, including DFS, and sampled stream macroinvertebrate communities 
at each site. Using macroinvertebrate data, I calculated and compared taxonomic and trait-based 
metrics as indicators of ecosystem health across land-use types. I used a variety of metrics, 
including the Macroinvertebrate Community Index (MCI) and its quantitative equivalent, the 
QMCI, the Average Score Per Metric (ASPM) index, and community-weighted mean trait 
abundances, including facets of functional diversity to assess impacts on stream health.  
I found that human land uses negatively influenced stream health, indicated by greatly reduced 
MCI, QMCI, and ASPM scores. Although DFS explained most of the negative influences on 
macroinvertebrate communities in pastoral and horticultural streams, there were differences 
between native forest and horticultural streams not accounted for by DFS that contributed to 
declines in ecosystem health. I also found that sediment-specific macroinvertebrate metrics 
(sediment ‘decreasers’) were the best indicators of DFS impacts on stream health. Contrary to my 
predictions, I did not find that functional diversity was strongly reduced by land use or DFS, 
although several key traits responded to these stressors. Notably, life history trait modalities 
involving the number of reproductive cycles per year and oviposition site responded strongly to 
DFS and land use, indicating potential mechanisms contributing towards the impacts of these 
stressors on macroinvertebrate communities.  
ii 
My study points to the need to continuously manage the deposition of fine sediment in streams to 
help mitigate the adverse effects of human land use. Future research should further explore the 
role that fine sediment and other stressors associated with human land uses play in the degradation 
of streams ecosystems in the Tauranga Harbour basin. Quantifying land use and land cover 
(LULC) attributes using geospatial tools will help further explore the relationship between 
catchment properties and macroinvertebrate responses. Additionally, issues regarding trait 
syndromes, trade-offs, and database inconsistencies must be addressed to better understand the 
mechanistic links between specific macroinvertebrate traits and fine sediment.

year: 2024

title: Comparing static Gantt and mosaic charts for visualization of task schedules

authors: Luz, Saturnino

subjects: computer science

abstract: A mosaic chart has been proposed for representation of events on a timeline. While early studies demonstrated the effectiveness of mosaics in supporting visualization of multimedia records on a meeting browser, the usability of mosaics as a static timeline visualization has not been studied in more general settings. This paper investigates the use of the mosaic charts for visualization of project schedules. A user study was conducted to compare a building project schedule encoded alternatively as a mosaic or as a Gantt chart. Although the study focused on static graphs, for which the Gantt technique is usually very effective, results showed that the users were as fast and accurate at answering the questions using the mosaic representation as they were using Gantt charts. The analysis and experiment indicated algorithmic, space-filling and interpretation limitations of the mosaic technique. We suggest possible design improvements to overcome some of these limitations.

text: Comparing static Gantt and mosaic charts for visualization of task schedules A mosaic chart has been proposed for representation of events on a timeline. While early studies demonstrated the effectiveness of mosaics in supporting visualization of multimedia records on a meeting browser, the usability of mosaics as a static timeline visualization has not been studied in more general settings. This paper investigates the use of the mosaic charts for visualization of project schedules. A user study was conducted to compare a building project schedule encoded alternatively as a mosaic or as a Gantt chart. Although the study focused on static graphs, for which the Gantt technique is usually very effective, results showed that the users were as fast and accurate at answering the questions using the mosaic representation as they were using Gantt charts. The analysis and experiment indicated algorithmic, space-filling and interpretation limitations of the mosaic technique. We suggest possible design improvements to overcome some of these limitations.

year: 2011

title: Māori Goddesses in Literature Part 1: pre 1880 - 1900

authors: Yates-Smith, Aroha

subjects: Atua wāhine

abstract: Many contemporary Māori are familiar with atua wāhine, Māori goddesses, through accounts that have been passed on to them by word of mouth. Few, however, have had an opportunity to consult accounts of atua wāhine that date from the early period of Māori-Pākehā contact. Those who wish to do so may have considerable difficulty in sifting through all of the written materials for the information they seek. For this reason, this paper provides a review of the literature pertaining to atua wāhine from pre-1880 to 1900, together with a commentary on the sources to which reference is made. A review of literature on atua wāhine which appeared after 1900 will appear in the second volume of this journal.

text: Māori Goddesses in Literature Part 1: pre 1880 - 1900 Many contemporary Māori are familiar with atua wāhine, Māori goddesses, through accounts that have been passed on to them by word of mouth. Few, however, have had an opportunity to consult accounts of atua wāhine that date from the early period of Māori-Pākehā contact. Those who wish to do so may have considerable difficulty in sifting through all of the written materials for the information they seek. For this reason, this paper provides a review of the literature pertaining to atua wāhine from pre-1880 to 1900, together with a commentary on the sources to which reference is made. A review of literature on atua wāhine which appeared after 1900 will appear in the second volume of this journal.

year: 2000-10