title: Consequences of human-mediated marine intrusions on the zooplankton community of a temperate coastal lagoon

authors: Duggan, Ian C.

subjects: sandbar opening

abstract: Barrier bars separating lagoons from oceans are frequently breached as a management tool to prevent flooding of terrestrial ecosystems. The effects of such human-mediated openings on zooplankton have been investigated only in one tropical system. We investigated the temperate Waituna Lagoon, New Zealand, over a 2-year period when the barrier bar was 'artificially' breached on three occasions. Increases in salinity associated with opening of the barrier bars greatly influenced zooplankton community composition, and recovery of communities was dependent on the rate at which salinity returned to pre-disturbance conditions. As such, resilience of zooplankton in coastal lagoons is a function of the lagoon conditions returning to those experienced prior to barrier breach, rather than being a result of the zooplankton community simply recovering from a single defined disturbance event. In contrast to the tropical lagoon studies, temperature in Waituna Lagoon was inferred to explain a significant proportion of the variability in zooplankton community composition, independent of salinity. Appropriate timing for the opening of barrier bars by management authorities in temperate lagoons, which would allow the greatest opportunity for freshwater zooplankton communities to recover rapidly, will rely on determining the best time for rapid barrier bar reformation and high freshwater inflow rates (i.e. the recovery of zooplankton relies on return to initial conditions). However, such an approach is in direct conflict with the opening of barrier bars for management of water levels.

text: Consequences of human-mediated marine intrusions on the zooplankton community of a temperate coastal lagoon Barrier bars separating lagoons from oceans are frequently breached as a management tool to prevent flooding of terrestrial ecosystems. The effects of such human-mediated openings on zooplankton have been investigated only in one tropical system. We investigated the temperate Waituna Lagoon, New Zealand, over a 2-year period when the barrier bar was 'artificially' breached on three occasions. Increases in salinity associated with opening of the barrier bars greatly influenced zooplankton community composition, and recovery of communities was dependent on the rate at which salinity returned to pre-disturbance conditions. As such, resilience of zooplankton in coastal lagoons is a function of the lagoon conditions returning to those experienced prior to barrier breach, rather than being a result of the zooplankton community simply recovering from a single defined disturbance event. In contrast to the tropical lagoon studies, temperature in Waituna Lagoon was inferred to explain a significant proportion of the variability in zooplankton community composition, independent of salinity. Appropriate timing for the opening of barrier bars by management authorities in temperate lagoons, which would allow the greatest opportunity for freshwater zooplankton communities to recover rapidly, will rely on determining the best time for rapid barrier bar reformation and high freshwater inflow rates (i.e. the recovery of zooplankton relies on return to initial conditions). However, such an approach is in direct conflict with the opening of barrier bars for management of water levels.

year: 2010

title: Use of three New Zealand chironomids, Chironomus zealandicus, Chironomus sp. a and Polypedilum pavidus (lnsecta: Diptera) as biotoxicity test organisms

authors: Kanapathippillai, Jeyasingham

abstract: Three species of New Zealand chironomid, Chironomus sp. a, Chironomus zealandicus and Polypedilum pavidus were studied for their potential as biological indicators of freshwater environmental pollution and for use as laboratory bioassay species. 

A standard methodology was developed to successfully culture these three chironomids in the laboratory in order to obtain all larval stages of each species for laboratory bioassays.
 
Head capsule deformities and physical wear were examined for C. zealandicus collected from four study sites in summer and winter from 1994 to 1996, and from larvae reared for two successive generations in a control substrate. Results showed that the incidence of head capsule deformity was influenced by both substrate type and season. The cause of this deformation was not identified although sediment chemistry, genetics and other physico-chemical factors are collectively implicated. Significantly greater frequency of physical wear of head capsule structures in larvae collected from Hamurana Stream and a progressive decline of wear in larvae reared on a paper towel control substrate indicated that feeding activity on a relatively coarse substrate may have caused the wear. 

A field survey indicated that, although all these species were present at every site, they show particular site preference. A life cycle test was performed to investigate the substrate preference of C. sp. a and C. zealandicus on sediments collected from the four study sites, Hamilton Lake, Lake Ngaroto and Hamurana Stream and Sulphur Point of Lake Rotorua. Results showed that Lake Ngaroto sediment and Sulphur Point sediment favour C. sp. a and C. zealandicus respectively.

The acute toxicity of arsenite (Aѕ³⁺), arsenate (Aѕ⁵⁺) and copper (Cu²⁺) under different conditions was investigated. Although C. zealandicus and C. sp. a are closely related, they showed considerable difference in sensitivity to arsenic and copper. A number of biological (age), chemical (valency state), and physical (season, temperature) factors were observed to affect the toxicity of arsenic and copper to the test chironomid species. Chronic sublethal effects of arsenic-spiked sediments from Hamilton Lake and Lake Ngaroto and a paper towel substrate on C. zealandicus and C. sp. a were also studied under laboratory conditions. This study showed that the sensitivity of the chironomid species varied depending on the length of exposure to the spiked sediment, the number of endpoints examined, and other laboratory testing conditions such as renewal of dilution water. This experiment also indicated that C. zealandicus was more resistant to arsenic spiked sediment than C. sp. a. A protocol was developed for conducting standard sediment toxicity tests. 

The results of this work imply that although one or more of the chironomid species used in this study may be used as a bioindicator in monitoring freshwater lakes, use of these species as indicator organisms should be carefully assessed based on their occurrence in the location concerned. Although these three species may be used in laboratory bioassays, C. zealandicus appeared to be more convenient because of its continuous abundance at study sites and tolerance to physical handling.

text: Use of three New Zealand chironomids, Chironomus zealandicus, Chironomus sp. a and Polypedilum pavidus (lnsecta: Diptera) as biotoxicity test organisms Three species of New Zealand chironomid, Chironomus sp. a, Chironomus zealandicus and Polypedilum pavidus were studied for their potential as biological indicators of freshwater environmental pollution and for use as laboratory bioassay species. 

A standard methodology was developed to successfully culture these three chironomids in the laboratory in order to obtain all larval stages of each species for laboratory bioassays.
 
Head capsule deformities and physical wear were examined for C. zealandicus collected from four study sites in summer and winter from 1994 to 1996, and from larvae reared for two successive generations in a control substrate. Results showed that the incidence of head capsule deformity was influenced by both substrate type and season. The cause of this deformation was not identified although sediment chemistry, genetics and other physico-chemical factors are collectively implicated. Significantly greater frequency of physical wear of head capsule structures in larvae collected from Hamurana Stream and a progressive decline of wear in larvae reared on a paper towel control substrate indicated that feeding activity on a relatively coarse substrate may have caused the wear. 

A field survey indicated that, although all these species were present at every site, they show particular site preference. A life cycle test was performed to investigate the substrate preference of C. sp. a and C. zealandicus on sediments collected from the four study sites, Hamilton Lake, Lake Ngaroto and Hamurana Stream and Sulphur Point of Lake Rotorua. Results showed that Lake Ngaroto sediment and Sulphur Point sediment favour C. sp. a and C. zealandicus respectively.

The acute toxicity of arsenite (Aѕ³⁺), arsenate (Aѕ⁵⁺) and copper (Cu²⁺) under different conditions was investigated. Although C. zealandicus and C. sp. a are closely related, they showed considerable difference in sensitivity to arsenic and copper. A number of biological (age), chemical (valency state), and physical (season, temperature) factors were observed to affect the toxicity of arsenic and copper to the test chironomid species. Chronic sublethal effects of arsenic-spiked sediments from Hamilton Lake and Lake Ngaroto and a paper towel substrate on C. zealandicus and C. sp. a were also studied under laboratory conditions. This study showed that the sensitivity of the chironomid species varied depending on the length of exposure to the spiked sediment, the number of endpoints examined, and other laboratory testing conditions such as renewal of dilution water. This experiment also indicated that C. zealandicus was more resistant to arsenic spiked sediment than C. sp. a. A protocol was developed for conducting standard sediment toxicity tests. 

The results of this work imply that although one or more of the chironomid species used in this study may be used as a bioindicator in monitoring freshwater lakes, use of these species as indicator organisms should be carefully assessed based on their occurrence in the location concerned. Although these three species may be used in laboratory bioassays, C. zealandicus appeared to be more convenient because of its continuous abundance at study sites and tolerance to physical handling.

year: 1999

title: Upoko Tapu, Upoko Whakakapowai, Upoko Hokona

authors: Gabel, Robert Rutene Whakaangi

subjects: Ngāpuhi

abstract: Ngāpuhi, a confederation of Māori iwi (tribes) from Te Tai Tokerau, the northern region of Aotearoa, is the largest iwi of New Zealand. They were one of the first iwi to come into contact with Europeans in the early 19th century. During this period of contact, particularly between the years 1820 – 1831, Ngāpuhi had a devastating impact on the history of Māori, as they amassed a fighting force of some two thousand warriors and acquired the use of European firearms. Ngāpuhi then circumnavigated the North Island, waging war on coastal and inland tribes with the purpose of avenging past defeats and losses suffered at the hands of their traditional enemies. This objective was ultimately achieved, but this period of war also saw the emergence of another key event in Māori history, the beginning of the trade in what we now call toi moko, which were used to trade with Europeans for muskets. 

Given that Māori have always regarded the head as the most tapu part of the human anatomy, this thesis investigates and explores what effect or influence tikanga and tapu had on this trade. It further studies some of the rationales which allowed Ngāpuhi to override that sacred tradition and move into the trade of toi moko. This thesis argues that Ngāpuhi did not desecrate tapu in the selling and trading of toi moko but took advantage of another long-standing tradition that the tapu of the vanquished ceased to exist upon his death. Lastly, it argues that the trade in toi moko was necessary to ensure the safety and continuity of the Ngāpuhi iwi.

text: Upoko Tapu, Upoko Whakakapowai, Upoko Hokona Ngāpuhi, a confederation of Māori iwi (tribes) from Te Tai Tokerau, the northern region of Aotearoa, is the largest iwi of New Zealand. They were one of the first iwi to come into contact with Europeans in the early 19th century. During this period of contact, particularly between the years 1820 – 1831, Ngāpuhi had a devastating impact on the history of Māori, as they amassed a fighting force of some two thousand warriors and acquired the use of European firearms. Ngāpuhi then circumnavigated the North Island, waging war on coastal and inland tribes with the purpose of avenging past defeats and losses suffered at the hands of their traditional enemies. This objective was ultimately achieved, but this period of war also saw the emergence of another key event in Māori history, the beginning of the trade in what we now call toi moko, which were used to trade with Europeans for muskets. 

Given that Māori have always regarded the head as the most tapu part of the human anatomy, this thesis investigates and explores what effect or influence tikanga and tapu had on this trade. It further studies some of the rationales which allowed Ngāpuhi to override that sacred tradition and move into the trade of toi moko. This thesis argues that Ngāpuhi did not desecrate tapu in the selling and trading of toi moko but took advantage of another long-standing tradition that the tapu of the vanquished ceased to exist upon his death. Lastly, it argues that the trade in toi moko was necessary to ensure the safety and continuity of the Ngāpuhi iwi.

year: 2012