title: Weed management - Lessons form the USA

authors: Madsen, John

abstract: Aquatic weed management has a more than 100 year history in the United States, with the first efforts by the US Army Corps of Engineers to remove water hyacinth from southeastern United States waters in 1899. Through these efforts, several important lessons have been learned. First, plant management requires a plan of action that considers the level of infestation, makes site-specific management recommendations, and considers all potential techniques for use both spatially and temporally.
A good plan also includes public involvement and education. Integrated Plant Management has become the model for aquatic plant management. It includes developing an understanding of factors that exacerbate plant growth, and methods to mitigate plant growth and enhance management success, including an understanding of target plant biology and phenology. In addition, most natural water bodies will require selective management, targeting the weed and minimizing the impact on desirable native plant species.
Steady funding to invest in plant management is a necessity. Disruptions to funding will result in larger problems in the future. An important part of the investment is a consistent investment in applied research, with the target of improved plant control. In the United States, an attempt is made to consider biological, chemical, mechanical, and physical techniques for management of aquatic weeds. The use of these techniques is restricted by economic, environmental, and regulatory thresholds.
While biological control may appear to be the preferred approach, many weeds do not have an effective biological control agent. Even effective biological control agents do not provide uniform control across the ecological range of a weed. Chemical control is still the most widely used technique in the United States. Chemical control is effective and relatively inexpensive, but increased regulatory restriction has impacted the use of herbicides in some areas.
Mechanical techniques use machines to remove plant growth. In particular, harvesting is widely used as an immediate control to plant growth. However, harvesting is relatively slow and expensive, and may have a significant fish and aquatic animal bycatch. Physical control involves altering the environment to reduce plant growth. In the United States, this includes the use of benthic barriers, shading materials, and drawdown. Each of these techniques can be considered tools in our plant management toolbox, and all have their place and utility.

text: Weed management - Lessons form the USA Aquatic weed management has a more than 100 year history in the United States, with the first efforts by the US Army Corps of Engineers to remove water hyacinth from southeastern United States waters in 1899. Through these efforts, several important lessons have been learned. First, plant management requires a plan of action that considers the level of infestation, makes site-specific management recommendations, and considers all potential techniques for use both spatially and temporally.
A good plan also includes public involvement and education. Integrated Plant Management has become the model for aquatic plant management. It includes developing an understanding of factors that exacerbate plant growth, and methods to mitigate plant growth and enhance management success, including an understanding of target plant biology and phenology. In addition, most natural water bodies will require selective management, targeting the weed and minimizing the impact on desirable native plant species.
Steady funding to invest in plant management is a necessity. Disruptions to funding will result in larger problems in the future. An important part of the investment is a consistent investment in applied research, with the target of improved plant control. In the United States, an attempt is made to consider biological, chemical, mechanical, and physical techniques for management of aquatic weeds. The use of these techniques is restricted by economic, environmental, and regulatory thresholds.
While biological control may appear to be the preferred approach, many weeds do not have an effective biological control agent. Even effective biological control agents do not provide uniform control across the ecological range of a weed. Chemical control is still the most widely used technique in the United States. Chemical control is effective and relatively inexpensive, but increased regulatory restriction has impacted the use of herbicides in some areas.
Mechanical techniques use machines to remove plant growth. In particular, harvesting is widely used as an immediate control to plant growth. However, harvesting is relatively slow and expensive, and may have a significant fish and aquatic animal bycatch. Physical control involves altering the environment to reduce plant growth. In the United States, this includes the use of benthic barriers, shading materials, and drawdown. Each of these techniques can be considered tools in our plant management toolbox, and all have their place and utility.

year: 2015

title: The link between erosion, phosphorus and water quality

authors: Gibbs, Max M.

abstract: In lakes, the solubility of phosphorus (P) in water, and therefore its availability to aquatic plants (macrophytes and algae) for growth, is controlled by oxygen and pH. The supply of dissolved reactive P (DRP) to the lake water column is mostly from sediment release from
decomposing plant material and iron oxides during periods of low oxygen, although in Lake Rotorua and most of the other lakes on the central volcanic plateau, spring-fed streams carry relatively high concentrations of DRP into the lakes. The mechanism for releasing iron-bound DRP from the sediment focusses around the oxidation state iron (Fe) and manganese (Mn). In well oxygenated conditions iron exists in the oxidised state as ferric ions which form ferric oxides that are insoluble in water. These oxides sequester DRP as they precipitate and remove it from the water column. When the oxygen concentration falls to zero (anoxic conditions) iron exists in the reduced state as ferrous ions, which are soluble in water. As the ferric form reduces to the ferrous form it dissolves and the DRP bound to the iron is released into the water column where it is used by algae for growth. The algae eventually senesce and die, returning the P to the sediment as particulate P, where it can be recycled during the next period of anoxia.
Apart from recycling of algal biomass, P also comes from the catchment, bound to the iron oxides in soil particles. The P content of the soil is greatest in the finest soil particles, which are the first to be eroded by rainfall and do not settle until they reach the calm waters of a lake. There they augment the P load from the senescing algal biomass, thereby increasing the amount of DRP that can be released during the next anoxic event. Because of the high background concentration of dissolved inorganic nitrogen in the lake water, the addition of any DRP will stimulate algal growth and thus result in a deterioration of lake water quality. Land management strategies to reduce soil erosion include changes to the way land is farmed and the interception and retention of fine sediment using detention bunds.

text: The link between erosion, phosphorus and water quality In lakes, the solubility of phosphorus (P) in water, and therefore its availability to aquatic plants (macrophytes and algae) for growth, is controlled by oxygen and pH. The supply of dissolved reactive P (DRP) to the lake water column is mostly from sediment release from
decomposing plant material and iron oxides during periods of low oxygen, although in Lake Rotorua and most of the other lakes on the central volcanic plateau, spring-fed streams carry relatively high concentrations of DRP into the lakes. The mechanism for releasing iron-bound DRP from the sediment focusses around the oxidation state iron (Fe) and manganese (Mn). In well oxygenated conditions iron exists in the oxidised state as ferric ions which form ferric oxides that are insoluble in water. These oxides sequester DRP as they precipitate and remove it from the water column. When the oxygen concentration falls to zero (anoxic conditions) iron exists in the reduced state as ferrous ions, which are soluble in water. As the ferric form reduces to the ferrous form it dissolves and the DRP bound to the iron is released into the water column where it is used by algae for growth. The algae eventually senesce and die, returning the P to the sediment as particulate P, where it can be recycled during the next period of anoxia.
Apart from recycling of algal biomass, P also comes from the catchment, bound to the iron oxides in soil particles. The P content of the soil is greatest in the finest soil particles, which are the first to be eroded by rainfall and do not settle until they reach the calm waters of a lake. There they augment the P load from the senescing algal biomass, thereby increasing the amount of DRP that can be released during the next anoxic event. Because of the high background concentration of dissolved inorganic nitrogen in the lake water, the addition of any DRP will stimulate algal growth and thus result in a deterioration of lake water quality. Land management strategies to reduce soil erosion include changes to the way land is farmed and the interception and retention of fine sediment using detention bunds.

year: 2015

title: Transformation geometry: Mā te nekehanga, mā te whakaata, mā te hurihanga

authors: Manuel, Hirāni

abstract: The whakataukī (proverb) promotes the notion that navigating obstacles or barriers successfully is a natural part of learning. The learning and teaching of the Māori language and culture are key practices in Māori-medium settings. Teachers in such classrooms are actively promoting academic success as Māori through the medium of te reo Māori (the Māori language). This stance includes the learning of mathematics.

text: Transformation geometry: Mā te nekehanga, mā te whakaata, mā te hurihanga The whakataukī (proverb) promotes the notion that navigating obstacles or barriers successfully is a natural part of learning. The learning and teaching of the Māori language and culture are key practices in Māori-medium settings. Teachers in such classrooms are actively promoting academic success as Māori through the medium of te reo Māori (the Māori language). This stance includes the learning of mathematics.

year: 2015