title: A mass balance evaluation of the ecological significance of historical nitrogen fluxes in Lake Kinneret

authors: Nishri, A.

subjects: nitrate

abstract: Lake Kinneret (LK) is a monomictic lake that has undergone significant biological and chemical changes over the last three decades of the twentieth century. The transition between the 1970s and the 1980s attracted a lot of scientific attention as it was marked by significant changes in the ecology of the lake. In the early 1980s, phytoplankton biomass increased, apparently in response to an increase in the external soluble reactive phosphorus (SRP) load. This period was marked by a rise in hypolimnetic levels of ammonium (NH4) and SRP as well as surface water dissolved oxygen (DO) and pH. Cconcomitantly, in surface waters in winter levels of NH4 increased and NO₃ decreased. In this study interrelationships amongst these observations were examined with a mass balance modelling approach, including simulation of individual nutrient sources and sinks, focusing on nitrogen fluxes in winter. The step-like rise in phytoplankton biomass in 1981 may have been triggered by the increase in winter external loads of SRP, as P is likely to be the growth-limiting nutrient during this season. The additional P load led to a sequence of changes including greater summer phytoplankton biomass, followed by enhanced sedimentation of organic matter. Furthermore, higher organic matter mineralization fluxes within the hypolimnion resulted in elevated levels of NH4 and SRP in this layer through the 1980s, with a feedback to productivity in the trophogenic zone following seasonal destratification in early winter. In an apparent transition period (late 1970s to early 1980s), an increase in the modelled rate of nitrate (NO₃) production occurred via nitrification together with increased uptake of the additional nitrate by phytoplankton. These results are consistent with increased phytoplankton abundance and elevated levels of surface water NH4 and DO during this period. Through this period the increase in phytoplankton uptake of NO₃ predominated over the increase in nitrification, and NO₃ concentrations in the 1980s were reduced compared with the previous decade, with increased partitioning of N in biomass and NH₄.

text: A mass balance evaluation of the ecological significance of historical nitrogen fluxes in Lake Kinneret Lake Kinneret (LK) is a monomictic lake that has undergone significant biological and chemical changes over the last three decades of the twentieth century. The transition between the 1970s and the 1980s attracted a lot of scientific attention as it was marked by significant changes in the ecology of the lake. In the early 1980s, phytoplankton biomass increased, apparently in response to an increase in the external soluble reactive phosphorus (SRP) load. This period was marked by a rise in hypolimnetic levels of ammonium (NH4) and SRP as well as surface water dissolved oxygen (DO) and pH. Cconcomitantly, in surface waters in winter levels of NH4 increased and NO₃ decreased. In this study interrelationships amongst these observations were examined with a mass balance modelling approach, including simulation of individual nutrient sources and sinks, focusing on nitrogen fluxes in winter. The step-like rise in phytoplankton biomass in 1981 may have been triggered by the increase in winter external loads of SRP, as P is likely to be the growth-limiting nutrient during this season. The additional P load led to a sequence of changes including greater summer phytoplankton biomass, followed by enhanced sedimentation of organic matter. Furthermore, higher organic matter mineralization fluxes within the hypolimnion resulted in elevated levels of NH4 and SRP in this layer through the 1980s, with a feedback to productivity in the trophogenic zone following seasonal destratification in early winter. In an apparent transition period (late 1970s to early 1980s), an increase in the modelled rate of nitrate (NO₃) production occurred via nitrification together with increased uptake of the additional nitrate by phytoplankton. These results are consistent with increased phytoplankton abundance and elevated levels of surface water NH4 and DO during this period. Through this period the increase in phytoplankton uptake of NO₃ predominated over the increase in nitrification, and NO₃ concentrations in the 1980s were reduced compared with the previous decade, with increased partitioning of N in biomass and NH₄.

year: 2010

title: Sediment removal as a restoration measure for the campus lakes

authors: Paul, Wendy J.

abstract: The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes.

This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.

text: Sediment removal as a restoration measure for the campus lakes The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes.

This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.

year: 2008-05

title: Te Tarata

authors: Maxwell, Te Kahautu

abstract: This composition placed second in the Haka Composition Section. Te Tarata this composition commemorates the battle of Te Tarata in Te Whakatōhea 15 October 1865. This was the aftermath of the killing of the missionary Rev Carl Sylvius Volkner on the 2 March 1865. At the battle of Te Tarata it is recorded as the only calvary charge in the New Zealand Land Wars. Te Whakatōhea ingeniously wove around the palisade walls tī kouka (Cordyline australis) or cabbage tree. When the canon ball hit the palisades the tī kouka absorbed the force of the canon ball and rebounded the ball. 20 Te Whakatohea were killed and a number of others were wounded. This composition was performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka Competition 2015.

text: Te Tarata This composition placed second in the Haka Composition Section. Te Tarata this composition commemorates the battle of Te Tarata in Te Whakatōhea 15 October 1865. This was the aftermath of the killing of the missionary Rev Carl Sylvius Volkner on the 2 March 1865. At the battle of Te Tarata it is recorded as the only calvary charge in the New Zealand Land Wars. Te Whakatōhea ingeniously wove around the palisade walls tī kouka (Cordyline australis) or cabbage tree. When the canon ball hit the palisades the tī kouka absorbed the force of the canon ball and rebounded the ball. 20 Te Whakatohea were killed and a number of others were wounded. This composition was performed by Ōpōtiki Mai Tawhiti at the Te Matatini World Championship Kapa Haka Competition 2015.

year: 2014-10-10