title: Effect of a physical disturbance event on deep-sea nematode community structure and ecosystem function

authors: Leduc, Daniel

subjects: biodiversity

abstract: Numerous studies have been conducted on the effect of physical disturbance on shallow water benthic communities, but there is a paucity of data from deep-sea environments. We conducted a laboratory experiment using undisturbed sediment cores from Chatham Rise (water depth =345 m), Southwest Pacific, to investigate the effects of a physical disturbance event (resuspension of surface sediments) on sediment characteristics (sediment grain size, pigment content), nematode community attributes (abundance, diversity, community structure) and ecosystem function (sediment community oxygen consumption (SCOC)) over a period of 9 days. Disturbance did not have any noticeable impact on sediment characteristics, SCOC, or nematode species richness, but led to changes in vertical distribution patterns and shifts in nematode community structure. The magnitude of disturbance-related effects was, however, much smaller than the effect of sediment depth (0-1, 1-3, and 3-5 cm), and the main impact of disturbance on nematode vertical distribution patterns and community structure appeared to be related to a vertical re-shuffling of nematodes in the sediments rather than mortality. We did not observe substantial increases in the abundance of nematode genera generally regarded as disturbance-tolerant, such as Sabatieria. The worst-affected species belongs to the Stilbonematinae, a group of typically long and slender nematodes that may be easily damaged by physical disturbance. The limited impact of physical disturbance on benthic community structure and function suggests that the Chatham Rise nematode community is relatively resilient to sediment resuspension. This resilience may have arisen from frequent exposure to disturbance in the field (e.g., from strong currents), or may be a more widespread feature of nematode communities.

text: Effect of a physical disturbance event on deep-sea nematode community structure and ecosystem function Numerous studies have been conducted on the effect of physical disturbance on shallow water benthic communities, but there is a paucity of data from deep-sea environments. We conducted a laboratory experiment using undisturbed sediment cores from Chatham Rise (water depth =345 m), Southwest Pacific, to investigate the effects of a physical disturbance event (resuspension of surface sediments) on sediment characteristics (sediment grain size, pigment content), nematode community attributes (abundance, diversity, community structure) and ecosystem function (sediment community oxygen consumption (SCOC)) over a period of 9 days. Disturbance did not have any noticeable impact on sediment characteristics, SCOC, or nematode species richness, but led to changes in vertical distribution patterns and shifts in nematode community structure. The magnitude of disturbance-related effects was, however, much smaller than the effect of sediment depth (0-1, 1-3, and 3-5 cm), and the main impact of disturbance on nematode vertical distribution patterns and community structure appeared to be related to a vertical re-shuffling of nematodes in the sediments rather than mortality. We did not observe substantial increases in the abundance of nematode genera generally regarded as disturbance-tolerant, such as Sabatieria. The worst-affected species belongs to the Stilbonematinae, a group of typically long and slender nematodes that may be easily damaged by physical disturbance. The limited impact of physical disturbance on benthic community structure and function suggests that the Chatham Rise nematode community is relatively resilient to sediment resuspension. This resilience may have arisen from frequent exposure to disturbance in the field (e.g., from strong currents), or may be a more widespread feature of nematode communities.

year: 2013

title: A review on the use of Hydroxyapatite-carbonaceous structure composites in bone replacement materials for strengthening purposes

authors: Siddiqui, Humair Ahmed

subjects: Science & Technology

abstract: Biomedical materials constitute a vast scientific research field, which is devoted to producing medical devices which aid in enhancing human life. In this field, there is an enormous demand for long-lasting implants and bone substitutes that avoid rejection issues whilst providing favourable bioactivity, osteoconductivity and robust mechanical properties. Hydroxyapatite (HAp)-based biomaterials possess a close chemical resemblance to the mineral phase of bone, which give rise to their excellent biocompatibility, so allowing for them to serve the purpose of a bone-substituting and osteoconductive scaffold. The biodegradability of HAp is low (Ksp ≈ 6.62 × 10⁻¹²⁶) as compared to other calcium phosphates materials, however they are known for their ability to develop bone-like apatite coatings on their surface for enhanced bone bonding. Despite its favourable bone regeneration properties, restrictions on the use of pure HAp ceramics in high load-bearing applications exist due to its inherently low mechanical properties (including low strength and fracture toughness, and poor wear resistance). Recent innovations in the field of bio-composites and nanoscience have reignited the investigation of utilising different carbonaceous materials for enhancing the mechanical properties of composites, including HAp-based bio-composites. Researchers have preferred carbonaceous materials with hydroxyapatite due to their inherent biocompatibility and good structural properties. It has been demonstrated that different structures of carbonaceous material can be used to improve the fracture toughness of HAp, as they can easily serve the purpose of being a second phase reinforcement, with the resulting composite still being a biocompatible material. Nanostructured carbonaceous structures, especially those in the form of fibres and sheets, were found to be very effective in increasing the fracture toughness values of HAp. Minor addition of CNTs (3 wt.%) has resulted in a more than 200% increase in fracture toughness of hydroxyapatite-nanorods/CNTs made using spark plasma sintering. This paper presents a current review of the research field of using different carbonaceous materials composited with hydroxyapatite with the intent being to produce high performance biomedically targeted materials.

text: A review on the use of Hydroxyapatite-carbonaceous structure composites in bone replacement materials for strengthening purposes Biomedical materials constitute a vast scientific research field, which is devoted to producing medical devices which aid in enhancing human life. In this field, there is an enormous demand for long-lasting implants and bone substitutes that avoid rejection issues whilst providing favourable bioactivity, osteoconductivity and robust mechanical properties. Hydroxyapatite (HAp)-based biomaterials possess a close chemical resemblance to the mineral phase of bone, which give rise to their excellent biocompatibility, so allowing for them to serve the purpose of a bone-substituting and osteoconductive scaffold. The biodegradability of HAp is low (Ksp ≈ 6.62 × 10⁻¹²⁶) as compared to other calcium phosphates materials, however they are known for their ability to develop bone-like apatite coatings on their surface for enhanced bone bonding. Despite its favourable bone regeneration properties, restrictions on the use of pure HAp ceramics in high load-bearing applications exist due to its inherently low mechanical properties (including low strength and fracture toughness, and poor wear resistance). Recent innovations in the field of bio-composites and nanoscience have reignited the investigation of utilising different carbonaceous materials for enhancing the mechanical properties of composites, including HAp-based bio-composites. Researchers have preferred carbonaceous materials with hydroxyapatite due to their inherent biocompatibility and good structural properties. It has been demonstrated that different structures of carbonaceous material can be used to improve the fracture toughness of HAp, as they can easily serve the purpose of being a second phase reinforcement, with the resulting composite still being a biocompatible material. Nanostructured carbonaceous structures, especially those in the form of fibres and sheets, were found to be very effective in increasing the fracture toughness values of HAp. Minor addition of CNTs (3 wt.%) has resulted in a more than 200% increase in fracture toughness of hydroxyapatite-nanorods/CNTs made using spark plasma sintering. This paper presents a current review of the research field of using different carbonaceous materials composited with hydroxyapatite with the intent being to produce high performance biomedically targeted materials.

year: 2018

title: Viewing the world through a wider lens: Māori and council planning documents

authors: Kennedy, Nathan

subjects: New Zealand

abstract: My effort to convey an iwi perspective on environmental resource management - what we call kaitiakitanga – should highlight for new planners about to enter the profession that the environmental perspectives of hapū  and iwi (which are provided for in the RMA), are currently not well covered in either mainstream local government planning or education.

text: Viewing the world through a wider lens: Māori and council planning documents My effort to convey an iwi perspective on environmental resource management - what we call kaitiakitanga – should highlight for new planners about to enter the profession that the environmental perspectives of hapū  and iwi (which are provided for in the RMA), are currently not well covered in either mainstream local government planning or education.

year: 2008-07-30