title: Detecting anthropogenic impacts on estuarine benthic communities

authors: Clark, Dana

subjects: Macroinvertebrates

abstract: Our estuaries, and the benefits that we derive from them, are threatened by the cumulative effects of interacting stressors. Separating the impacts of anthropogenic stressors from natural variability in the marine environment is extremely difficult. This is particularly true for estuaries, due to their inherent complexity and the prevalence of difficult-to-manage diffuse stressors. Successful management and protection of these valuable ecosystems requires innovative monitoring approaches that can reliably detect anthropogenic stressor impacts. In this thesis, I examined approaches for detecting the effects of three diffuse land-derived stressors (sedimentation, nutrient loading, and heavy metal contamination) on estuarine benthic communities.

Using Gradient Forest analysis, I explored the relative importance of environmental factors, operating across multiple spatio-temporal scales, in influencing patterns of compositional turnover in estuarine benthic macroinvertebrate communities across New Zealand. Both land-derived stressors (sediment mud content and total sediment nitrogen and phosphorus content) and natural environmental variables (sea surface temperature, Southern Oscillation Index, and wind-wave exposure) were important predictors of compositional turnover, reflecting a matrix of processes interacting across space and time. Generalized linear models were used to link these turnover values to measures of benthic macroinvertebrate diversity, which are commonly used as indicators of ecological health. Based on compositional turnover, I could disentangle the negative effects of land-derived stressors from natural environmental variability. Critical stressor levels associated with high rates of compositional turnover were identified, providing a useful contribution to the current knowledge on land-derived stressor effects.

Once I had determined that anthropogenic impacts could be disentangled from natural variability, I developed indicators (Benthic Health Models; BHMs) to assess estuary health in response to two dominant coastal stressors (sedimentation and heavy metal contamination). Benthic macroinvertebrate community data were used in separate canonical analyses of principal coordinates to create multivariate models of community responses to these stressors. Both models performed well (R² = 0.81, 0.71), and were unaffected by regional and estuarine typology differences. They offer a sensitive and standardised approach to assessing estuarine health that allows separation of the two stressors.

I also examined the potential for emerging molecular approaches to inform estuary health assessment. Recent advances in environmental genomics allow characterization of less visible forms of benthic biodiversity, offering a more holistic view of the ecosystem and potentially providing early warning signals of disturbance. A manipulative nutrient enrichment experiment was conducted in two estuaries and environmental DNA (eDNA) metabarcoding was used to examine the response of eukaryotic (18S rRNA), diatom only (rbcL) and bacterial (16S rRNA) communities. Multivariate analyses demonstrated differential changes in examined communities between sites, suggesting a context dependent response to nutrient enrichment. These patterns aligned with changes in morphologically identified macroinvertebrate communities, confirming concordance between eDNA-based and current monitoring approaches. This work represents a first step towards the development of molecular estuary monitoring tools, which could transform current approaches to ecosystem health assessment.

This thesis demonstrates that the detection of anthropogenic impacts on estuarine benthic communities requires an understanding of the response of communities to stressors and how this response is modified by natural environmental processes operating at different spatio-temporal scales. My research contributes to the management and protection of estuaries by improving knowledge on the processes generating broad scale patterns in benthic macroinvertebrate communities, developing indicators that can be used to assess estuary health and demonstrating the potential of eDNA metabarcoding as a new tool for estuary health assessment.

text: Detecting anthropogenic impacts on estuarine benthic communities Our estuaries, and the benefits that we derive from them, are threatened by the cumulative effects of interacting stressors. Separating the impacts of anthropogenic stressors from natural variability in the marine environment is extremely difficult. This is particularly true for estuaries, due to their inherent complexity and the prevalence of difficult-to-manage diffuse stressors. Successful management and protection of these valuable ecosystems requires innovative monitoring approaches that can reliably detect anthropogenic stressor impacts. In this thesis, I examined approaches for detecting the effects of three diffuse land-derived stressors (sedimentation, nutrient loading, and heavy metal contamination) on estuarine benthic communities.

Using Gradient Forest analysis, I explored the relative importance of environmental factors, operating across multiple spatio-temporal scales, in influencing patterns of compositional turnover in estuarine benthic macroinvertebrate communities across New Zealand. Both land-derived stressors (sediment mud content and total sediment nitrogen and phosphorus content) and natural environmental variables (sea surface temperature, Southern Oscillation Index, and wind-wave exposure) were important predictors of compositional turnover, reflecting a matrix of processes interacting across space and time. Generalized linear models were used to link these turnover values to measures of benthic macroinvertebrate diversity, which are commonly used as indicators of ecological health. Based on compositional turnover, I could disentangle the negative effects of land-derived stressors from natural environmental variability. Critical stressor levels associated with high rates of compositional turnover were identified, providing a useful contribution to the current knowledge on land-derived stressor effects.

Once I had determined that anthropogenic impacts could be disentangled from natural variability, I developed indicators (Benthic Health Models; BHMs) to assess estuary health in response to two dominant coastal stressors (sedimentation and heavy metal contamination). Benthic macroinvertebrate community data were used in separate canonical analyses of principal coordinates to create multivariate models of community responses to these stressors. Both models performed well (R² = 0.81, 0.71), and were unaffected by regional and estuarine typology differences. They offer a sensitive and standardised approach to assessing estuarine health that allows separation of the two stressors.

I also examined the potential for emerging molecular approaches to inform estuary health assessment. Recent advances in environmental genomics allow characterization of less visible forms of benthic biodiversity, offering a more holistic view of the ecosystem and potentially providing early warning signals of disturbance. A manipulative nutrient enrichment experiment was conducted in two estuaries and environmental DNA (eDNA) metabarcoding was used to examine the response of eukaryotic (18S rRNA), diatom only (rbcL) and bacterial (16S rRNA) communities. Multivariate analyses demonstrated differential changes in examined communities between sites, suggesting a context dependent response to nutrient enrichment. These patterns aligned with changes in morphologically identified macroinvertebrate communities, confirming concordance between eDNA-based and current monitoring approaches. This work represents a first step towards the development of molecular estuary monitoring tools, which could transform current approaches to ecosystem health assessment.

This thesis demonstrates that the detection of anthropogenic impacts on estuarine benthic communities requires an understanding of the response of communities to stressors and how this response is modified by natural environmental processes operating at different spatio-temporal scales. My research contributes to the management and protection of estuaries by improving knowledge on the processes generating broad scale patterns in benthic macroinvertebrate communities, developing indicators that can be used to assess estuary health and demonstrating the potential of eDNA metabarcoding as a new tool for estuary health assessment.

year: 2021

title: Short Intermolecular Phosphorus…Phosphorus Distances in the Crystal Structures of Bis{Bis(Perfluoroaryl)Phosphino}Methanes

authors: Saunders, Graham C.

subjects: Bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}methane

abstract: The crystal structure of bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}-methane 2 determined by single crystal X-ray diffraction comprises pairs of molecules related by an inversion center and possessing short P•••P distances. The molecular structure and the structure of the pairs are similar to those in the crystal structure of bis{bis(pentafluorophenyl)-phosphino}methane, although the packing is different. Comparison with the structures of bis(diphenylphosphino)methane and bis{bis(pentafluorophenyl)phosphine}difluoromethane suggests that intramolecular C–H•••F–C interactions are the most important factor in determining the presence of the short P•••P distances in the crystal structures of bis(diarylphosphino)methanes.

text: Short Intermolecular Phosphorus…Phosphorus Distances in the Crystal Structures of Bis{Bis(Perfluoroaryl)Phosphino}Methanes The crystal structure of bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}-methane 2 determined by single crystal X-ray diffraction comprises pairs of molecules related by an inversion center and possessing short P•••P distances. The molecular structure and the structure of the pairs are similar to those in the crystal structure of bis{bis(pentafluorophenyl)-phosphino}methane, although the packing is different. Comparison with the structures of bis(diphenylphosphino)methane and bis{bis(pentafluorophenyl)phosphine}difluoromethane suggests that intramolecular C–H•••F–C interactions are the most important factor in determining the presence of the short P•••P distances in the crystal structures of bis(diarylphosphino)methanes.

year: 2013

title: Spat survival of Paphies ventricosa (Toheroa) in an aquaculture setting

authors: Chew, Martyn Andrew

abstract: The toheroa (Papris ventracosta) is a large intertidal surf cam endemic to New Zealand. This species has a long history with the people of New Zealand in both cultural and economic sense. Exploitation and environmental change have greatly diminished the wild stocks of these animals making a sustainable fishery no longer feasible. Aquaculture has been widely discussed as a potentially profitable option for this species due to its large size, esteemed taste and its social and cultural significance. Aquaculture of toheroa could generate many benefits for the people of the toheroa beaches, as aquaculture has done in other regions of New Zealand. However, the suitability of toheroa for aquaculture is largely unknown, with many questions needing to be answered before that can become a reality. The purpose of this research is to gain a better understanding of the environmental conditions which will support the successful cultivation of wild caught toheroa spat in recirculating aquaculture systems (RAS). This is done by answering questions around knowledge gaps in the biology of the animal. Three experiments were conducted on aspects of the animal’s environment and biology. The first experiment sought to identify the presence of microphytobenthos’s within the wild population beds of the toheroa. As evidence suggests from research conducted on other species, microphytobenthos is an essential part of the animal’s ecosystem which might be a necessary component of a successful spat rearing operation. The experiment showed elevated chlorophyll levels (a proxy for microphytobenthos) within toheroa beds relative to other areas of the beach. The second experiment compared survival and growth rates in sediment vs. non-sediment holding systems. The results of this study indicated the benefits of housing spat in sediments, as demonstrated by differences in measured growth and mortality. A third experiment sought to test for size dependent mortality rates within the RAS. Somewhat surprisingly, it was found that smaller toheroa (0-10mm) performed better within a system compared to larger ones (20-30). Larger toheroa tended to eject themselves from the sediment constantly, an act which may have compromised their growth and survivorship. The result of these experiments answered questions and raise many more.  Potentially through understanding these questions we can create tools which industry and conservation can use. This research show that successful toheroa spat can be successfully integrated into an aquaculture system. With mortality settling the animals feeding and showing healthy condition. However, the next stage would be to optimize this. Toheroa aquaculture being in its infancy requires a wide variety of research before considered feasible. However, results and observations made from this research can help in identifying and specializing future research objectives.

text: Spat survival of Paphies ventricosa (Toheroa) in an aquaculture setting The toheroa (Papris ventracosta) is a large intertidal surf cam endemic to New Zealand. This species has a long history with the people of New Zealand in both cultural and economic sense. Exploitation and environmental change have greatly diminished the wild stocks of these animals making a sustainable fishery no longer feasible. Aquaculture has been widely discussed as a potentially profitable option for this species due to its large size, esteemed taste and its social and cultural significance. Aquaculture of toheroa could generate many benefits for the people of the toheroa beaches, as aquaculture has done in other regions of New Zealand. However, the suitability of toheroa for aquaculture is largely unknown, with many questions needing to be answered before that can become a reality. The purpose of this research is to gain a better understanding of the environmental conditions which will support the successful cultivation of wild caught toheroa spat in recirculating aquaculture systems (RAS). This is done by answering questions around knowledge gaps in the biology of the animal. Three experiments were conducted on aspects of the animal’s environment and biology. The first experiment sought to identify the presence of microphytobenthos’s within the wild population beds of the toheroa. As evidence suggests from research conducted on other species, microphytobenthos is an essential part of the animal’s ecosystem which might be a necessary component of a successful spat rearing operation. The experiment showed elevated chlorophyll levels (a proxy for microphytobenthos) within toheroa beds relative to other areas of the beach. The second experiment compared survival and growth rates in sediment vs. non-sediment holding systems. The results of this study indicated the benefits of housing spat in sediments, as demonstrated by differences in measured growth and mortality. A third experiment sought to test for size dependent mortality rates within the RAS. Somewhat surprisingly, it was found that smaller toheroa (0-10mm) performed better within a system compared to larger ones (20-30). Larger toheroa tended to eject themselves from the sediment constantly, an act which may have compromised their growth and survivorship. The result of these experiments answered questions and raise many more.  Potentially through understanding these questions we can create tools which industry and conservation can use. This research show that successful toheroa spat can be successfully integrated into an aquaculture system. With mortality settling the animals feeding and showing healthy condition. However, the next stage would be to optimize this. Toheroa aquaculture being in its infancy requires a wide variety of research before considered feasible. However, results and observations made from this research can help in identifying and specializing future research objectives.

year: 2022