title: Isolation, Structural Determination and Acute Toxicity of Pinnatoxins E, F and G

authors: Selwood, Andrew I.

subjects: Pinnatoxin

abstract: Pinnatoxins and pteriatoxins are a group of cyclic imine toxins that have hitherto only been isolated from Japanese shellfish. As with other cyclic imine shellfish toxins, pinnatoxins cause rapid death in the mouse bioassay for lipophilic shellfish toxins, but there is no evidence directly linking these compounds to human illness. We have identified the known pinnatoxins A (1) and D (6), and the novel pinnatoxins E (7), F (8) and G (5), in a range of shellfish and environmental samples from Australia and New Zealand using LC−MS. After isolation from the digestive glands of Pacific oysters, the structures of the novel pinnatoxins were determined by mass spectrometry and NMR spectroscopy, and their LD50 values were evaluated by ip administration to mice. Examination of the toxin structures, together with analysis of environmental samples, suggests that pinnatoxins F and G are produced separately in different dinoflagellates. Furthermore, it appears probable that pinnatoxin F (8) is the progenitor of pinnatoxins D (6) and E (7), and that pinnatoxin G (6) is the progenitor of both pinnatoxins A−C (1 and 2) and pteriatoxins A−C (3 and 4), via metabolic and hydrolytic transformations in shellfish.

text: Isolation, Structural Determination and Acute Toxicity of Pinnatoxins E, F and G Pinnatoxins and pteriatoxins are a group of cyclic imine toxins that have hitherto only been isolated from Japanese shellfish. As with other cyclic imine shellfish toxins, pinnatoxins cause rapid death in the mouse bioassay for lipophilic shellfish toxins, but there is no evidence directly linking these compounds to human illness. We have identified the known pinnatoxins A (1) and D (6), and the novel pinnatoxins E (7), F (8) and G (5), in a range of shellfish and environmental samples from Australia and New Zealand using LC−MS. After isolation from the digestive glands of Pacific oysters, the structures of the novel pinnatoxins were determined by mass spectrometry and NMR spectroscopy, and their LD50 values were evaluated by ip administration to mice. Examination of the toxin structures, together with analysis of environmental samples, suggests that pinnatoxins F and G are produced separately in different dinoflagellates. Furthermore, it appears probable that pinnatoxin F (8) is the progenitor of pinnatoxins D (6) and E (7), and that pinnatoxin G (6) is the progenitor of both pinnatoxins A−C (1 and 2) and pteriatoxins A−C (3 and 4), via metabolic and hydrolytic transformations in shellfish.

year: 2010

title: Spatial and temporal variation of coastal Ross Sea macrozoobenthos

authors: Mackenzie, Kyle

abstract: Antarctic shallow-water communities are projected to undergo considerable changes in the coming decades due to the impacts of climate change on the prevailing environmental conditions. A clear understanding of these communities’ vulnerability to change requires that the current relationships between environmental conditions and species assemblages be well understood. The benthic environment of the Ross Sea is subject to constant changes, including but not limited to changes in ice formations, salinity, light intensity, food types and food availability. The aim of this study was to quantify the temporal and spatial differences in macrozoobenthos between four coastal sites within the Ross Sea and determine the impact these abiotic factors could have on macrozoobenthic ecology.

The macrozoobenthic communities in four Ross Sea coastal sites (Cape Armitage and Cape Evans within the McMurdo Sound, and two sites within Terra Nova Bay, designated as Gondwana and Mario Zucchelli) were investigated, with multiple video transects taken from each site over the space of several years. Transects were taken at depths of 19 to 23 m, between late December and early January. 15 quadrats were selected at random for each of the transects, scaled to a size of 0.25 m². 

Cape Armitage had the highest species diversity (Simpson’s Diversity Index), while Mario Zucchelli had the lowest. Cape Evans and Gondwana shared a similar diversity. Cape Armitage was the most ecologically diverse, with most macrozoobenthos visible through the Cinachyra barbata spicule mat in evenly spaced clusters of diverse species. Cnidaria was the dominant phylum at Cape Armitage, while the remaining three sites were dominated numerically by two Echinoderms Odantaster validus and Sterechinus neumayeri, which were mainly observed on gravel and cobble substrates.

Macrozoobenthos species composition varied significantly between all four locations (One-way PERMANOVA p >0.001). A SIMPER analysis showed that Echinodermata (S. neumayeri and O. validus) and Cnidaria (Alcyonium antarcticum and Artemidactis victrix) were the main drivers of these differences. Only the Mario Zucchelli site showed a significant temporal difference over time, and there the change was marginal (p = 0.048). The change was largely due to an increase/decrease in the density of the main urchin species (S. neumayeri) between sequential year sampling. When data from all sites were combined, the species composition varied significantly across substrates (Two-way PERMANOVA, p >0.001), though it was hard to determine the underlying substrate in Cape Armitage due to spicule mats.

This research highlights the diverse benthic biota within the Ross Sea, and supports previous conclusions that assemblages are site-specific but rather stable over time. In terms of ongoing conservation and monitoring of the Ross Sea benthic environment, it points to the need for increased understanding of ecology in the Ross Sea for maintaining the diverse faunal communities found within the Southern Ocean.

text: Spatial and temporal variation of coastal Ross Sea macrozoobenthos Antarctic shallow-water communities are projected to undergo considerable changes in the coming decades due to the impacts of climate change on the prevailing environmental conditions. A clear understanding of these communities’ vulnerability to change requires that the current relationships between environmental conditions and species assemblages be well understood. The benthic environment of the Ross Sea is subject to constant changes, including but not limited to changes in ice formations, salinity, light intensity, food types and food availability. The aim of this study was to quantify the temporal and spatial differences in macrozoobenthos between four coastal sites within the Ross Sea and determine the impact these abiotic factors could have on macrozoobenthic ecology.

The macrozoobenthic communities in four Ross Sea coastal sites (Cape Armitage and Cape Evans within the McMurdo Sound, and two sites within Terra Nova Bay, designated as Gondwana and Mario Zucchelli) were investigated, with multiple video transects taken from each site over the space of several years. Transects were taken at depths of 19 to 23 m, between late December and early January. 15 quadrats were selected at random for each of the transects, scaled to a size of 0.25 m². 

Cape Armitage had the highest species diversity (Simpson’s Diversity Index), while Mario Zucchelli had the lowest. Cape Evans and Gondwana shared a similar diversity. Cape Armitage was the most ecologically diverse, with most macrozoobenthos visible through the Cinachyra barbata spicule mat in evenly spaced clusters of diverse species. Cnidaria was the dominant phylum at Cape Armitage, while the remaining three sites were dominated numerically by two Echinoderms Odantaster validus and Sterechinus neumayeri, which were mainly observed on gravel and cobble substrates.

Macrozoobenthos species composition varied significantly between all four locations (One-way PERMANOVA p >0.001). A SIMPER analysis showed that Echinodermata (S. neumayeri and O. validus) and Cnidaria (Alcyonium antarcticum and Artemidactis victrix) were the main drivers of these differences. Only the Mario Zucchelli site showed a significant temporal difference over time, and there the change was marginal (p = 0.048). The change was largely due to an increase/decrease in the density of the main urchin species (S. neumayeri) between sequential year sampling. When data from all sites were combined, the species composition varied significantly across substrates (Two-way PERMANOVA, p >0.001), though it was hard to determine the underlying substrate in Cape Armitage due to spicule mats.

This research highlights the diverse benthic biota within the Ross Sea, and supports previous conclusions that assemblages are site-specific but rather stable over time. In terms of ongoing conservation and monitoring of the Ross Sea benthic environment, it points to the need for increased understanding of ecology in the Ross Sea for maintaining the diverse faunal communities found within the Southern Ocean.

year: 2020

title: The modification of toheroa habitat by streams on Ripiro Beach

authors: Cope, Jane

abstract: Habitat modification and loss are key factors driving the global extinction and displacement of species. The scale and consequences of habitat loss are relatively well understood in terrestrial environments, but in marine ecosystems, and particularly soft sediment ecosystems, this is not the case. The characteristics which determine the suitability of soft sediment habitats are often subtle, due to the apparent homogeneity of sandy environments. This can make it difficult to detect habitat change in the first place let alone understand ecological consequences. Subtle differences in habitat quality are even harder to detect on dynamic surf beaches which are controlled by the interactions between the wave climate and the beach sands, and experience frequent and large changes. The exposed surf beaches of northern New Zealand, are home to toheroa (Paphies ventricosa), an endemic surf clam and New Zealand‘s most protected shell fish species. Over the course of the 20th century, toheroa were harvested to the point of collapse resulting in the closure of an important cultural, recreational and commercial fishery. Despite more than 40 years of protection, toheroa populations have failed to recover with populations in most locations continuing to decline. 

In northern New Zealand toheroa distribution is strongly associated with the small streams which flow across the toheroa beaches. A reduction in the flow of fresh water to the beach via these streams has been suggested as one possible factor which may be preventing the recovery of toheroa. However, little is known about the characteristics of the habitat, and the mechanism driving this toheroa-stream relationship has not received specific attention. The objective of this research was to better understand the effect of streams on beach habitat in the hope of determining the drivers of toheroa distribution. Specifically, I investigated how sediment type, topography, water table depth and sediment temperatures varied across exposed intertidal sediments adjacent to and away from streams. Sampling took place at four sites along Ripiro Beach during the summer, the season when toheroa are most susceptible to thermal stress and streams are thought to provide some protection from dissipation and heat stress. Grainsize distributions from the sampled sediment cores were processed using a Malvern Mastersizer 3000 laser diffractometer (Malvern, UK). The surface elevation and sediment temperature profiles of the subaerial beach was measured using a theodolite CDN pro accurate waterproof thermometers (Model DTW450L). Temperatures were measured at five sediment depths (2cm, 4cm, 7.5cm, 10.5cm, 20.5cm) throughout the sampling period. 

The effect of the streams on the grain size distribution of intertidal sediments appeared to be limited to the high tide, where the proportion of fine sediments was highest in stream adjacent sediments. Greater variations in grain size occurred along the beach, but the greatest difference in sediment sizes occurred when contrasting current day beach grain size distributions with sediment data collected in 1974. Beach sediments from 2017 contained 26661% time more medium sediment indicating the beach is now much coaster than it was 44 years ago. However, as no time series is available for sediment composition at Ripiro it is uncertain whether this change in beach make up is indicative of year-to-year variation or a long term trend. Beach topography varied consistently in the vicinity of streams. The elevation and slope of the beach face was lowest in the path of streams. Along the upper beach, low elevation in the path of the stream lead to the formation of deep bowl like features. As a result of this topography, adjacent to the stream, the water table remained close to the sediment surface throughout the sampling period (< 20 cm), in contrast to point‘s away from the stream where the water table was below the sampling depth. 

The hypothesis that streams would provide a thermal refuge for toheroa was one of the key questions of this thesis. What I found was that stream driven difference in sediment temperatures were only apparent in the upper intestinal, the area occupied by juvenile toheroa when they first recruit to the beach. Temperatures away from streams were significantly higher (> 3.5 °C) than stream adjacent sediments. However, in the middle intestinal, the area occupied by adult toheroa, the seep face exerted a greater influence on sediment temperatures than the stream and temperatures were no different regardless of stream proximity. The findings of this study suggest that the toheroa-stream relationship is not a direct response to the presence of freshwater, but rather is driven by the modification of the intertidal sediments by the streams. The increased erosion in these areas reduces the distance between the sediment surface and the water table, increasing the moisture content of the sediments. Additionally, the formation of the basin like depressions in the upper intertidal may act to aggregate spat and juvenile toheroa through the effect of this topography on the beach swash regime. At mid-tide areas adjacent to streams, the depth of the water table was such that adult toheroa are likely to be either fully or partially immersed throughout the low tide. Away from streams, the water table is beyond the burrowing depth of toheroa. For both juveniles and adults, stream associated areas may provide important protection against desiccation, through increasing moisture content of the sediments and for juveniles through reduced sediment temperatures. 

Evidently, streams do modify beach habitat in a way that makes it inhabitable for toheroa. Just not in the way that was anticipated. This study has increased our knowledge of beach characteristics that provide good toheroa habitat. Further research is required to test these hypotheses and better understand the effects of climate and terrestrial land use on beach state and therefore the suitability of the beach for toheroa.

text: The modification of toheroa habitat by streams on Ripiro Beach Habitat modification and loss are key factors driving the global extinction and displacement of species. The scale and consequences of habitat loss are relatively well understood in terrestrial environments, but in marine ecosystems, and particularly soft sediment ecosystems, this is not the case. The characteristics which determine the suitability of soft sediment habitats are often subtle, due to the apparent homogeneity of sandy environments. This can make it difficult to detect habitat change in the first place let alone understand ecological consequences. Subtle differences in habitat quality are even harder to detect on dynamic surf beaches which are controlled by the interactions between the wave climate and the beach sands, and experience frequent and large changes. The exposed surf beaches of northern New Zealand, are home to toheroa (Paphies ventricosa), an endemic surf clam and New Zealand‘s most protected shell fish species. Over the course of the 20th century, toheroa were harvested to the point of collapse resulting in the closure of an important cultural, recreational and commercial fishery. Despite more than 40 years of protection, toheroa populations have failed to recover with populations in most locations continuing to decline. 

In northern New Zealand toheroa distribution is strongly associated with the small streams which flow across the toheroa beaches. A reduction in the flow of fresh water to the beach via these streams has been suggested as one possible factor which may be preventing the recovery of toheroa. However, little is known about the characteristics of the habitat, and the mechanism driving this toheroa-stream relationship has not received specific attention. The objective of this research was to better understand the effect of streams on beach habitat in the hope of determining the drivers of toheroa distribution. Specifically, I investigated how sediment type, topography, water table depth and sediment temperatures varied across exposed intertidal sediments adjacent to and away from streams. Sampling took place at four sites along Ripiro Beach during the summer, the season when toheroa are most susceptible to thermal stress and streams are thought to provide some protection from dissipation and heat stress. Grainsize distributions from the sampled sediment cores were processed using a Malvern Mastersizer 3000 laser diffractometer (Malvern, UK). The surface elevation and sediment temperature profiles of the subaerial beach was measured using a theodolite CDN pro accurate waterproof thermometers (Model DTW450L). Temperatures were measured at five sediment depths (2cm, 4cm, 7.5cm, 10.5cm, 20.5cm) throughout the sampling period. 

The effect of the streams on the grain size distribution of intertidal sediments appeared to be limited to the high tide, where the proportion of fine sediments was highest in stream adjacent sediments. Greater variations in grain size occurred along the beach, but the greatest difference in sediment sizes occurred when contrasting current day beach grain size distributions with sediment data collected in 1974. Beach sediments from 2017 contained 26661% time more medium sediment indicating the beach is now much coaster than it was 44 years ago. However, as no time series is available for sediment composition at Ripiro it is uncertain whether this change in beach make up is indicative of year-to-year variation or a long term trend. Beach topography varied consistently in the vicinity of streams. The elevation and slope of the beach face was lowest in the path of streams. Along the upper beach, low elevation in the path of the stream lead to the formation of deep bowl like features. As a result of this topography, adjacent to the stream, the water table remained close to the sediment surface throughout the sampling period (< 20 cm), in contrast to point‘s away from the stream where the water table was below the sampling depth. 

The hypothesis that streams would provide a thermal refuge for toheroa was one of the key questions of this thesis. What I found was that stream driven difference in sediment temperatures were only apparent in the upper intestinal, the area occupied by juvenile toheroa when they first recruit to the beach. Temperatures away from streams were significantly higher (> 3.5 °C) than stream adjacent sediments. However, in the middle intestinal, the area occupied by adult toheroa, the seep face exerted a greater influence on sediment temperatures than the stream and temperatures were no different regardless of stream proximity. The findings of this study suggest that the toheroa-stream relationship is not a direct response to the presence of freshwater, but rather is driven by the modification of the intertidal sediments by the streams. The increased erosion in these areas reduces the distance between the sediment surface and the water table, increasing the moisture content of the sediments. Additionally, the formation of the basin like depressions in the upper intertidal may act to aggregate spat and juvenile toheroa through the effect of this topography on the beach swash regime. At mid-tide areas adjacent to streams, the depth of the water table was such that adult toheroa are likely to be either fully or partially immersed throughout the low tide. Away from streams, the water table is beyond the burrowing depth of toheroa. For both juveniles and adults, stream associated areas may provide important protection against desiccation, through increasing moisture content of the sediments and for juveniles through reduced sediment temperatures. 

Evidently, streams do modify beach habitat in a way that makes it inhabitable for toheroa. Just not in the way that was anticipated. This study has increased our knowledge of beach characteristics that provide good toheroa habitat. Further research is required to test these hypotheses and better understand the effects of climate and terrestrial land use on beach state and therefore the suitability of the beach for toheroa.

year: 2018